Activated Dolomite Adsorption – Gaseous Effluent Treatment

Activated Dolomite Adsorption – Gaseous Effluent Treatment

Hanna, J-A. (2010). Activated Dolomite Adsorption – Gaseous Effluent Treatment. Invest Northern Ireland.

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The QUESTOR Centre

Applied Technology Unit

Report on behalf of Green Energy Engineering

Activated Dolomite Adsorption

– Gaseous Effluent Treatment

Prepared by ______________________

Dr Julie-Anne Hanna & Manus Carey

Approved by ______________________

Dr Elaine Groom

Date: 6th July 2010

The QUESTOR Centre Applied Technology Unit

1.0 Summary

This project involves trialling dolomite and activated dolomite in a commercial

flue to investigate their ability to remove major gaseous pollutants. Recent

investigations into utilising activated Dolomite have proved extremely

encouraging; in terms of phosphate, nitrate and dye removal from wastewater

and lab based removal of gaseous pollutants.

2.0 The Experimental Objectives

The following areas have been previously been researched:

I. An investigation into the charring of dolomite to optimise the specific

surface area

II. An investigation into the effectiveness of activated dolomite for treating a

range of industrial pollutants

III. Comparison of activated dolomite to activated carbon and other

adsorbates.

IV. Application of standard mathematical isotherm models to experimental

data to predict adsorptive behaviour.

V. Economic evaluation of using biological dolomite as an adsorbent/filter

for industrial gaseous treatment.

During this trial a small filter was produced and fitted in the flue to allow real

time data to be collected. Data was collected on 4 occasions;

With no filter

Raw dolomite filter

Activated dolomite filter

And an activated carbon filter

3.0 Introduction

3.1 Dolomite

Dolomite (the double carbonate of calcium and magnesium) is a compound

rather than a mixture of calcite and magnesite. Dolomite has a chemical

formula of CaCO3.MgCO3 with a molecular weight of 184.4 and a specific

gravity of 2.84g/cm3. Theoretically, pure dolomite contains 45.7% MgCO3 and


54.3% CaCO3. Its hardness is 3.5 – 4.0 on Moh‟s scale and its rhombohedral,

crystal system can be seen in Figure 1, (1). Pure dolomitic limestone has

30.4% CaO, 21.8% MgO, and 47.8% CO2. Impurities such as silica, chert,

clay, shale, feldspar, etc, are usually associated with the dolomitic limestone.

Figure 1: Dolomite structure

Dolomite is used in agriculture for neutralising soil acidity through a base

exchange, with calcium and magnesium cations displacing the hydrogen ions

in the soil. This process has been reported to increase crop yield by 14 –

40%, (1). Furthermore dolomite is used to make-up for the magnesium loss in

the soil due to plant growth and is also extensively used to counteract the

acidity of urea. The uses of dolomite can be classified into the following three

areas: (as shown in Table 1)

Direct applications,

Uses of selectively calcined dolomite,

Chemicals from dolomite.


Direct Applications Semi calcined Dolomite Chemicals from

Dolomite

Agriculture Magnesium Oxy-chloride

Cement

Magnesium Oxide

Cement Mortar

Clinker

Magnesium Oxy-sulphate

Cement

Magnesium Hydroxide

Treatment of Cracks Inorganic Magnesia

Foams

Magnesium Carbonate

Road Filler Silicate Bricks

Table 1: Uses of dolomite

3.2 Acid Rain

Acid rain is a term which describes the acidity of wet and dry deposition. This

includes acidity falling as rain, snow, hail, mist or fog (wet deposition) and the

dry deposition of gases and particles(2).

Rainfall is naturally acidic due to the presence of carbon dioxide in the

atmosphere which combines with the water vapour to form weak carbonic

acid. However the combustion of fossil fuels produces waste gases such as

sulphur dioxide (SO2), oxides of nitrogen (NOX) and to lesser extent, chloride

(Cl). These pollutants, over time, undergo a series of reactions which

produce sulphuric acid, nitric acid or hydrochloric acid, thus increasing the

acidity of the rain.

The main sources of SO2 are fossil fuel combustion, smelting, manufacture of

sulphuric acid, incineration of refuse and production of elemental sulphur.

Coal burning is the single largest man-made source of SO2 accounting for

50% of annual global emissions, with oil burning accounting for a further 25-

30%(3).

Globally, quantities of nitrogen oxides produced naturally far outweigh man-

made emissions. These man made emissions are mainly due to fossil fuel

combustion from both stationary sources i.e. power generation (21%) and


mobile sources i.e. transport (44%). Other contributions come from non-

combustion processes, for example nitric acid manufacture, welding

processes and the use of explosives.

Due to pollutant gas migration acidification is an international problem. For

this reason the European Union have agreed on air quality limit values for

specified pollutants in a series of „Daughter Directives‟.

The first Daughter Directive (1999/30/EEC), covering SO2, NOX,

particular matter as PM10, and lead, came into force on 19 July 1999.

This Directive contains values for these pollutants.

The second Daughter Directive (2000/69/EC) covers carbon monoxide

and benzene. It came into force on 13 December 2002.

The third Daughter Directive (or EC Ozone Directive, 2002/3/EC) came

into force in 2002 and is scheduled for transposition in 2003.

The air quality strategy sets out a strategy framework with in which air quality

policies will be taken forward in the short to medium term, and also details

objectives to be met by 2005 for the air pollutants covered(4).

The Large Combustion Plant Directive:

The Revised Large Combustion Plants Directive (LCPD, 2001/80/EC) applies

to combustion plants with a thermal output of greater than 50 MW. The

revised LCPD takes into account advances in combustion and abatement

technologies. It will replace the original LCPD (88/609/EEC) adopted in

November 1988. The LCPD aims to reduce acidification, ground level ozone,

and particles throughout Europe by controlling emissions of sulphur dioxide

(SO2), nitrogen oxides (NOx), and dust (particulate matter (PM)) from large

combustion plants (LCPs). These plants include power stations, petroleum

refineries, steelworks, and other industrial processes running on solid, liquid,

or gaseous fuel.


3.3 Global Warming

Global Warming is also referred to as the greenhouse effect or climate

change. Greenhouse gases such as, water vapour, carbon dioxide (CO2),

methane and nitrous oxide (N2O) trap the infrared radiation emitted by the

Earth‟s surface. The atmosphere acts like the glass in a greenhouse, allowing

short-wave UV radiation to travel through but trapping some of the long-wave

infrared radiation. This process makes the temperature rise in the

atmosphere just as it does in the greenhouse (2).

Increasing the concentration of the greenhouse gases traps more radiation in

the lower atmosphere, enhancing the natural greenhouse effect. The

„enhanced‟ greenhouse effect is the direct result of human activities.

Processes such as, the burning of fossil fuel, industrial operations and

deforestation, increase CO2 and methane in the atmosphere. The effect of

this global warming has a profound effect on rainfall, plant growth and rising

sea levels.

Carbon dioxide is the gas most commonly thought of as greenhouse gas. It is

responsible for approximately half of the atmospheric heat retained by trace

gases. It is produced naturally through respiration. However man-made

sources of CO2 include fossil fuel combustion, forest clearing, biomass

burning and manufacture of cement.

Figures produced by the Government show that emissions of the basket of six

greenhouse gases fell by about 14½ per cent between the base year and

2005. The UK has agreed to cut greenhouse gas emissions by 12.5 per cent

over the 2008-2012 period to meet its Kyoto Protocol commitment.

Provisional 2005 data suggest carbon dioxide emissions in 2005 rose by a

quarter of one per cent on 2004 figures. The increase is due mainly to the rise

in energy consumption, coupled with a small switch from gas to coal in power

stations. Net emissions of carbon dioxide fell by about 5½ per cent between

1990 and 2005.

Methane is formed naturally in wetland regions as a by-product of the decay

of organic material. Rapid increases in methane levels are attributed to a

number of factors resulting from human activities. Among these are, direct


leakage of natural gas, by-production emission of coal mining, and disposal of

domestic refuse in landfill sites. Nitrous oxide is naturally produced by oceans

and rainforests. Man-made sources of N2O include nylon and nitric acid

production, agricultural practices, cars with catalytic converters and biomass

burning.

3.4 International Response to Climate Change

In June 1992 at the Rio Earth Summit, 162 Governments signed the

Framework Convention of Climate Change. This Convention calls for nations

to adopt a precautionary approach towards the threat of global warming. At

the Kyoto Conference of Parties (1997) nations agreed to reduce greenhouse

gas emissions by 5.2% by 2008-2012, relative to 1990 levels (the Kyoto

Protocol)(4). The Kyoto Protocol was finally ratified by 146 countries and

came into effect on 16th February 2005.

The Kyoto protocol expires in 2012, thus the United Nations Framework

Convention for Climate Change created to combat climate change beyond

that date.

The Convention on Climate Change sets an overall framework for

intergovernmental efforts to tackle the challenge posed by climate change. It

recognizes that the climate system is a shared resource whose stability can

be affected by industrial and other emissions of carbon dioxide and other

greenhouse gases. The Convention enjoys near universal membership, with

189 countries having ratified.

Under the Convention, governments:

gather and share information on greenhouse gas emissions, national

policies and best practices

launch national strategies for addressing greenhouse gas emissions

and adapting to expected impacts, including the provision of financial

and technological support to developing countries

cooperate in preparing for adaptation to the impacts of climate change

http://www.bbc.co.uk/climate/policies/un_convention.shtml

http://www.bbc.co.uk/climate/policies/un_convention.shtml


4.0 Literature Review

4.1 Adsorption

In adsorption, molecules distribute themselves between two phases, one of

which is a solid whilst the other may be a liquid or a gas (5). It is a physical-

chemical process by which molecules diffuse from the bulk of the fluid to the

surface of the solid forming a distinct adsorbed phase.

The solid, which takes up the gas, is called the adsorbent, and the fluid taken

up on the surface is called the adsorbate. It is not always easy to tell whether

the gas is inside the solid or merely at the surface because most practical

adsorbents are very porous structures with large internal surface areas. It is

not possible to determine the surface areas of such materials by optical or

electron microscopy because of the size and complexity of the pores and

channels of the materials. The gas adsorption itself, however, can be used to

determine the accessible area of the adsorbents.

Molecules and atoms can attach themselves onto surfaces in two ways. In

physisorption (physical adsorption), there is a weak van der Waals attraction

between the adsorbate and the surface. This attraction although weak is long

ranged. During the process of physisorption, the chemical identity of the

adsorbate remains intact, i.e. no breakage of the covalent structure of the

adsorbate takes place.

In chemisorption (chemical adsorption), the adsorbate attaches to the solid by

formation of a chemical bond with the surface. This interaction is much

stronger than physisorption, and, in general, chemisorption has more stringent

requirements for the compatibility of adsorbate and surface site than

physisorption.

Any potential application of adsorption has to be considered along with

alternatives such as distillation, absorption and liquid extraction. Each

separation process exploits a difference in a property between the

components to be separated.


4.2 Characterisation by Physical Gas Adsorption

Physical gas adsorption is often the most widely used technique to study the

pore characteristics of solid materials. The technique accurately determines

the amount of gas adsorbed (adsorbate) on a solid material, which is a direct

correlation to its structure and porous properties.

When the quantity of adsorbate on a surface is measured over a wide range

of relative pressures at constant temperature, the result is an adsorption

isotherm. Similarly, desorption isotherms can be obtained by measuring the

quantities of gas removed from the sample as the relative pressure is

lowered. All adsorption isotherms may be grouped into one of five types

shown in figure 2(6).

Figure 2: The Five Different Adsorption Isotherms

Type I physisorption isotherms are exhibited by microporous solids having

relatively small external surfaces, for example, activated carbons. Type II

isotherms are the normal form of isotherm obtained with a nonporous or

macroporous adsorbent. This type of isotherm represents unrestricted

monolayer – multiplayer adsorption. Type III isotherms are convex to the

P/Po axis over its entire range. An example is the adsorption of water vapour

on nonporous carbons. Type IV isotherms are associated with capillary


condensation in mesopores, indicated by the steep slope at higher relative

pressures. Type V isotherms corresponds to the type III isotherm, except that

pores in the mesopore range are present. Types IV and V, associated with

mesoporosity, usually exhibit hysteresis between the adsorption and

desorption isotherms.

The isotherm obtained from these adsorption measurements provides

information on the surface area, pore volume, and pore size distribution.

Different probe gases including N2, Ar, and CO2 are frequently used as the

adsorbates, depending on the nature of the material and the information

required. For example; in the case of activated carbon, CO2 is often the

preferred adsorbate, since these adsorption measurements are mostly

performed at temperatures near ambient, which will improve the diffusion

properties in the highly microporous system compared to the low

temperatures used in N2(7).

N2 adsorption at 77K and at below atmospheric pressures, has remained

universally unsurpassed and can be used for routine quality control, as well as

for investigation of new materials. If applied over a wide range of relative

pressures, N2 adsorption isotherms provide information on size distribution in

the micro-, meso-, and macro- porosity range (approx. 0.5 - 200nm).

4.3 Adsorption Isotherms Theories

4.3 1 Langmuir Isotherm Theory

The Langmuir theory (8) is based on the assumption that localised adsorption

takes place on a surface that is energetically homogeneous with no

interaction between adsorbed molecules. The surface has a specific number

of sites, each of which can adsorb one molecule. Maximum adsorption

corresponds to a saturated monolayer and is represented by a plateau in the

isotherm. The Langmuir isotherm has the form

pK

pK

L

L

1 (1)


linearization of equation (1) allows the Langmuir constants KL and vm to be

evaluated.

mmLads

pp

K

pp 00 /1/ (2)

Plotting (p/p0)/vads (or (p/p0)n) against (p/p0) allows vm to be determined from

the slope (1/vm or 1/nm) and KL from the intercept (1/KLvm or 1/KLnm).

4.3.2 Freundlich Isotherm Theory

The Freundlich theory (9), empirically derived to fit the parabolic shape of the

adsorption isotherm, and is described as;

Fn

F pKq

1

0<n

1<1 and n >1 (3)

By plotting the linear form lnq against lnp, nF, the heterogeneity factor, can be

determined from the slope (1/nF) and KF from the intercept (lnKF).

The Langmuir and Freundlich Isotherm Models when applied to the

adsorption on the various adsorbents at 20°C. These constants were

determined using linear regression techniques on the isotherm data.

The nomenclature is as follows:

nm = number of moles of adsorbate required to form a monolayer on the

adsorbent (moles)

KL = Langmuir constant (N-1m-2)

Nf = Freundlich heterogeneity factor

KF = Freundlich constant (N-1m-2)

r2 = square of the Pearson product moment correlation coefficient


4.4 Adsorption of Carbon Dioxide The pressure on industry to decrease the emission of gaseous pollutants has

increased in recent years due to the strict regulations brought in to force,

coinciding with the Kyoto Protocol. It is generally accepted that the cost

associated with the separation of CO2 from flue gases introduces the largest

economic penalty to the industries involved.

The major sources of carbon dioxide are from fossil fuel power stations,

natural gas treatment, purification of hydrocarbons, production of hydrogen

gas and aerospace industry. Therefore a broad spectrum of cost effective gas

separation processes have been developed. In relation to price/performance,

physical adsorption is one of the most important techniques to control air

pollution.

A suitable adsorbent required for the adsorption of CO2 from industrial

streams must have the following properties (10):

High selectively and adsorption capacity for CO2 at high temperatures

Adequate adsorption/desorption kinetics for CO2 at operating conditions

Stable adsorption capacity of CO2 after repeated adsorption/desorption cycles

Adequate mechanical strength of adsorbent after cyclic exposure to high

pressure streams

The concept of using thermally treated dolomite as an adsorbate optimises

the carbonation reaction of CaO and the reversible calcination of CaCO3 as a

suitable separation process for CO2. The background for this separation was

first proposed by DuMotay and Marechal which used lime to aid the

gasification of carbon by steam (11). Silaban et al. (12) studied the reversibility

of this reaction in dolomites and limestones as the base of a high temperature

separation of CO2 to produce hydrogen (13).

4.5 Removal of Sulphur Dioxide (SO2).

SO2 is a colourless gas, formed during the combustion of fuels containing

sulphur. It is a respiratory irritant, and is toxic at high concentrations. It is

also damaging to ecosystems and a major precursor in the formation of acid

rain.


Total SO2 emissions in 2000 were 1,125,000 tonnes, which is a reduction of

70% since 1990. Power stations account for 66% of total SO2 emissions. By

2010, total emissions, according to guidelines must be below 625,000

tonnes(14).

A reduction in the atmospheric emissions of SO2 produced by fossil fuel

combustion process can be achieved at one of three stages (15).

1. Reducing the sulphur content before combustion:

The majority of coals currently in use within the UK, have a sulphur

content in the range of 1-3% by weight. Sulphur in coal is found in

sulphate, inorganic and organic forms. Inorganic sulphur, in the form of

pyrite (FeS2), can be removed and can result in a reduction of 10-50%

of the total sulphur content. However this process subsequently

produces large quantities of wastewater. Washing can also change the

physical characteristics of coal; therefore operational problems may

occur when combustion takes place.

2. Sulphur removal during combustion:

The most developed commercial technology for the removal of sulphur

during combustion is the Fluidised Bed Combustion (FBC) process.

This process involves the combustion of coal in a bed of inert material

such as sand, with air being blown up from beneath the bed at high

velocities. The fluidised movement within the combustion chamber

results in a greater heat transfer efficiency and therefore operational

temperatures are lower than in a conventional system. SO2 emissions

are controlled by adding a sorbent (limestone) to the bed of inert

material. The limestone effectively absorbs the SO2 as it is released;

retaining it within the ash. The FBC can achieve in the region of 80-

90% SO2 removal. Two main disadvantages of this system are large

quantities of sorbent required and the large quantity of alkaline waste

produced.

3. Removal of sulphur after combustion:

Emissions of SO2 generated during the combustion of fossil fuels can

be reduced by treating the flue gases before they are emitted into the


atmosphere. This is termed Flue Gas Desulphurisation (FGD). The

most globally used FGD system involves the use of crusted

limestone/lime mixed with water. This mixture is sprayed into the

sulphur containing flue gas, the sorbent reacts with the SO2 to form an

aqueous slurry of calcium sulphite. Compressed air blown into the

slurry oxidises the calcium sulphite to produce calcium sulphate. This

product is then treated to remove the excess water and either sold to

the building trade or disposed of as landfill. SO2 removal can be in the

region of 90%.

4.6 Removal of Oxides of Nitrogen (NOX).

A mixture of nitrogen dioxide (NO2) and nitric oxide (NO) are emitted during

combustion processes. This mixture of oxides of nitrogen termed NOX. NO

produced is subsequently oxidised to NO2 in the atmosphere. NO2 is thought

to have both acute and chronic effects on airway and lung function,

particularly in people with asthma.

Total emissions of NOX have declined by 39% between 1990 and 2001. The

total NOX emissions in 2001 were 1,680,000 tonnes. By 2010, the UK have

agreed to cut the emissions of NOX to below 1,181,000 tonnes(14)

A reduction in the atmospheric emission of NOX produced by fossil fuel

combustion processes can be achieved at one of two stages (15).

1. NOX removal during combustion:

Low NOX burners ensure that initial fuel combustion occurs within fuel

rich conditions (low oxygen concentrations) resulting in any nitrogen

derivative produced being reduced to N2. Once initial combustion has

taken place, further air is introduced to the combustion chamber to

ensure complete combustion of the fuel. This greatly reduces the

opportunities for NOX production. Advanced low NOX burners can

reduce NOX concentration by up to 30%. Low NOX burners can be

installed on either new or existing combustion plants, and as such have

been retrofitted to a number of UK power stations.


2. NOX removal after combustion:

Emissions of NOX generated during the combustion process can be

reduced, as with SO2, by treating the flue gases. There are a number

of systems available;

Selective Catalytic Reduction (SCR)

Within the SCR, ammonia is injected into the flue gas. The NOX

present in the flue gases react with the ammonia and are converted to

nitrogen and water. This reaction occurs in the presence of vanadium

or tungsten oxide catalyst. This process can achieve a NOX reduction

of up to 80-90%, with minimal waste production. The main

disadvantages with this system are the high catalyst costs and the

short (2-3 year) operational life of the catalyst. This system is not

operational within the UK, although it is being used extensively in

Japan.

5.0 Material and Methods

5.1 Materials

The primary adsorbent used in the research was dolomite. A number of other

adsorbent materials were also used for comparison purposes. The materials

used as adsorbents during the research were:

5.1.1Dolomite Dolomite was obtained from Acheson and Glover in Co. Fermanagh, where it

was extracted from an open mine. Dolomite was used in three physical states,

untreated, charred and charred and washed in the lab trials. The chemical

formula was CaCO3.MgCO3 and is a common double carbonate mineral with

an ideal formula CaMg(CO3)2, rather than a mixture of calcite and magnesite,

with a molecular weight of 184.4 and specific gravity of 2.84g/cm3. Dolomite

forms rhombohedrons as its typical crystal habit but possibly due to twinning,

some crystals curve into saddle-like shapes. These crystals represent a

unique crystal habit that is well known as classical dolomite but is difficult to

distinguish from calcite


Some of the main physical properties are summarised below:

(i) colour is often pink or pinkish and can be colourless, white,

yellow, grey or even brown or black when iron is present in the

crystal

(ii) luster is pearly to vitreous to dull

(iii) crystals transparency ranges from transparent to translucent;

(iv) crystal System is trigonal bar 3

(v) crystal habits include saddle shaped rhombohedral twins and

simple rhombs some with slightly curved faces, also prismatic,

massive, granular and rock forming. Never found in

scalenohedrons

(vi) cleavage is perfect in three directions forming rhombohedrons

(vii) fracture is conchoidal

(viii) hardness is 3.5-4, (Mohz Scale)

(ix) specific gravity is 2.86 (average).

5.1.2 Activated Carbon

Chemviron Carbon supplied the Activated Carbon. The product known as

HGR US pellet of activated carbon designed for air and gas purification

applications. The product is produced by high temperature steam activation

of coal which resulting in a porous material with a high surface area allowing it

to adsorb a wide rang of organic compounds. The coal-based raw material

also ensures a high density product with good mechanical strength and low

dust content.

The extruded activated carbon has several properties that explain the

performance in a wide range of applications:

High loading capacity for a wide range of organic compounds.

Low outlet concentrations obtainable ensuring the emission

requirements.

High hardness to ensure excellent resistance to mechanical and

thermal stress.


Low stream to solvent ratio to minimise energy costs for steam

consumption, easier product recovery and reduced waste water in

solvent recovery applications.

This activated carbon was used in two different physical states, one in the

manufactured pellet form. The other was broken or ground form; this was

equivalent to the particle size range of that of the dolomite used.

5.2 Experimental Methods

5.2.1 Charring procedure

Dolomite was charred at a temperature of 800oC ±10%. Four crucibles were

filled with approximately 100g of dolomite. The furnace used was a Carbolite

type RHF 14/4. The dolomite filled crucibles were placed into the furnace

chamber, when the furnace was at the required temperature. The samples

remained in the furnace for an allocated time period of 12 hours at which point

the furnace chamber door was opened and the furnace switched off. The

dolomite remained in the furnace for a further hour, then it was removed to

cool.

5.3 Experimental Methods

5.3.1 Static Equilibrium Isotherm Determination

Initially, the sample to be studied was outgassed at 250 oC for at least 12

hours to ensure that the sample was completely dry, as this would affect the

adsorption properties.

The main sample vessel consisted of a 500ml Quickfit Pyrex reaction flask

and flask cover. The flask cover provides ports to allow pressure

measurements, temperature measurements, connection to a vacuum source

and a port to allow the introduction of adsorbate into the vessel. It was

ensured that all ports and connections were gas tight by use of Swaglock

connectors, silicon vacuum grease and finally wrapping of joints with Parafilm.

A known mass of the outgassed sample (approximately 0.5g ±0.5mg) was

placed into the vessel and sealed. The vessel was then placed into a 20 oC

(±0.5 oC) environment and put under vacuum for 2 hours at which point it was


isolated form the vacuum source, and the pressure monitored for 30mins so

as to ensure no leaks were present. The atmospheric pressure was recorded

using a mercury barometer also the initial pressure of the system was

recorded before the vacuum source was applied.

When the vessel was deemed to be at constant temperature and pressure,

these were recorded, and the first 50ml dose of adsorbate was introduced to

the vessel. The instantaneous pressure at injection and the pressure at

equilibrium was observed and recorded. Equilibrium would take anything

from up to 10-15 minutes to be achieved.

This process of injecting adsorbate and monitoring the pressure was

continued, whilst ensuring that the vessel was kept at a constant temperature,

until the relative pressure reached approximately 1.

This process was carried out a further two times so as to ensure the results

were repeatable. Any isotherms determined which deviated from the mode

observation was neglected and the procedure repeated.

5.3.2 Site Investigation

A filter was produced using a series of metal meshes which were coated in

the adsorbent material which was being investigated. The filter was fitted into

a flue joint for ease of fitting.

Figure 3: Joint in the flue were the filter was fitted

There was a small sample point drilled in the flue approximately 15inches

above the filter to allow the gases to be monitored. The probe of the gas

analyser was inserted into the flue to stabilise for approximately 15minutes

before the start of trial. During this time the boiler was ramped up to

maximum operating conditions. There were a number of gas samples taken


before the filter was fitted to be used a baseline. The filter was fitted and the

trial started with samples analysed regularly during the test period. The boiler

was fed wood pellets during the trial.

Figure 4: Feed stock and boiler

6.0 Investigation of Dolomite and Dolomite Adsorbents

6.1 Particle Size Distribution

The raw dolomite sample was placed in sieves and shaken for 30 minute

periods until the weight fractions remained constant. Sieves ranged from 90

micron – pan for the powdered dolomite to 2mm – pan for the grit. The results

displayed in figure 5 are those obtained from the initial analysis, which clearly

shows an uneven spread of particle size. The majority of the sample, 73.73%,

actually falls below 0.5mm. The results, figure 5, confirm that powder dolomite

is extremely fine, which may pose problems of blockage in any column

applications. The aim of this work is to develop dolomite usage for gaseous

effluent treatment, which would require a particle size more suited to column

and industrial scale work, i.e. grit size. As a result; dolomite samples used in

the charring and future experimental will have a particle size range of

2mm<X>0.5mm.

Figure 5: Sieve Analysis of the Dolomite Grit


6.2 Metal Analysis

The amount of selected metals present in the dolomite sieve analysis was

determined using an Inductively Coupled Plasma Optical Emission

Spectroscopy (ICP/OES). The ICP data in table 2, it was observed that all the

sieve fractions contained no or undetectable amounts of arsenic, cadmium,

cobalt, mercury or selenium.

Metals

(ppm) X>2mm 2<X>1.4 1.4<X>1.0 1.0<X>0.5 0.5<X>0.15 0.15<X>0.09 0.09<X>Pan

Al 16.640 21.020 19.900 27.620 47.530 58.045 110.675

B 0.262 0.120 0.108 0.116 0.153 0.148 0.269

Ba 0.108 0.083 0.074 0.090 0.117 0.139 0.289

Ca 6193 6698 6157 6534 6407 5962 5911

Cr <LOD 0.061 <LOD 0.066 0.178 0.281 0.754

Cu 0.063 0.221 0.252 0.144 0.221 0.21 0.344

Fe 66.33 71.32 60.94 66.19 75.86 82.00 128.65

Mg 3634 3523 3300 3616 3642 3387 3326

Mn 10.84 10.81 10.24 11.00 11.14 10.80 13.34

Ni 0.026 0.059 0.044 0.062 0.123 0.189 0.522

Pb 0.105 0.398 0.569 0.342 0.367 0.370 1.004

Sn 0.078 0.188 0.166 0.103 0.122 0.209 0.515

Sr 1.035 1.460 1.401 1.294 1.136 1.096 1.350

Ti <LOD <LOD <LOD 0.422 0.416 0.625 1.524

V 0.129 0.211 0.225 0.313 0.449 0.550 0.981

Zn 0.128 0.165 0.141 0.197 0.204 0.293 0.170

Sieve Analysis - Sieve Fractions

Table 2: The metal content of the various materials considered

As expected the majority of the metal cations present are that of calcium and

magnesium. The large quantities present are due to the calcium-magnesium

carbonate structure of dolomite. From the ICP/OES data, the percentage

composition of the Calcium and Magnesium oxides were found to be 35.6%,

22.8% respectively.

The percentages were calculated using the following methods:

Calcium

Average value for Ca present in the sample 6192.88mg/l and using the

molecular weight ratio for Ca: CaO 40:56. It was calculated that there was

8670.0332mg/l of CaO available in the sample. As the average dolomite

sample weight which was digested in acid was 0.2435g, it produced a solution


with the following concentration of dolomite 24354mg/l. The percentage of

CaO present was then calculates by

8670.0332mg/l divided by 24354mg/l = 0.35600033 this is multiplied by 100 to

produce a percentage 35.600033% shortened to 35.6%

Magnesium

Average value for Mg present in the sample 3330.92mg/l and using the

molecular weight ratio for Mg: MgO 24:40. It was calculated that there was

5551.51127mg/l of MgO available in the sample. As the average dolomite

sample weight which was digested in acid was 0.2435g, it produced a solution

with the following concentration of dolomite 24354mg/l. The percentage of

MgO present was then calculates by

5551.51127mg/l divided by 24354mg/l = 0.22795069 this is multiplied by 100

to produce a percentage 22.795069% shortened to 22.8%

This result provides a comparison to other leading dolomite research (Table

3). The Fermanagh dolomite contains a much higher percentage of both

oxides, suggesting dolomite with the potential to be a superior adsorbent.

Dolomite

Source

CaO

(%)

MgO

(%)

Fermanagh 35.6 22.8

Poland(8) 29.5 19.4

Hungary(9) 29.8 21.4

Table 3: Comparison of the different composition of Dolomite

On further inspection of the ICP data, it was seen that the majority of

impurities present in the samples, are varying amounts of iron, aluminium and

manganese. Figure 6 shows these impurities in relation to the different sieve

fraction, i.e. particle size. The increasing quantities of iron and aluminium


relate to the decreasing particle size. The results also suggest the amount of

manganese present is independent of particle size.

Figure 6: Metal Impurities present in Dolomite

6.3 Dolomite Charring

The thermal processing or „calcining‟ process is based on the fact that the

magnesium carbonate component of the dolomite decomposes at

temperatures around 800°C. The decomposition of dolomite at 800°C leads

to changes in the chemical composition of the surface and surface area of the

mineral. Generally, the products of partial decomposition of dolomite contain

calcium carbonate (calcite) and magnesium oxide and show a significant

increase in specific surface area and pore volume.

Partial decomposition results in the decomposition of magnesium carbonate

only, the calcium carbonate remains as a stable and mechanically resistant

structure of pumice type. As the time increases, the calcium carbonate

structure starts to breakdown and collapses in on itself, reducing the surface

area.

6.4 FTIR Spectroscopy

Infrared spectroscopy is an important technique in organic chemistry. It is an

easy way to identify the presence of certain functional groups in a molecule.

Also, one can use the unique collection of absorption bands to confirm the

identity of a pure compound or to detect the presence of specific impurities.


FTIR spectroscopy relies on detection of molecular vibrations. Mineral

identification is possible because minerals have characteristics absorption in

the fingerprint region of the infrared (1500-400 cm-1).

FTIR of Untreated Dolomite

0

5

10

15

20

25

30

35

40

45

50

4006008001000120014001600

Wavenumber (cm-1

)

Ab

so

rba

nce

Figure 7 FTIR spectroscopy of untreated dolomite

This fingerprint spectroscopy was obtained for the untreated dolomite (figure

7) displaying a number of regions were absorption occurred. From figure 8, it

can be seen that the major absorption peaks are present in the same areas

for charring time up to 4 hours however the gerenal trend of the absorbency of

these peaks has decreased due to the increased char time. As the charring

time becomes more extensive i.e. 6 and 8 hours (figure 9) these absorption

peaks do not appear. This observation would seem to suggest the breakdown

of the structure of these samples which are present in the other samples,

namely the complete decomposition of the calcium carbonate structure.

FTIR of Charred Dolomite Samples (I)

0

5

10

15

20

25

30

35

40

4006008001000120014001600

Wavenumber (cm-1

)

Ab

so

rba

nce

30min

1hr

2hr

4hr

Figure 8: FTIR spectroscopy of charred dolomite samples (I)


FTIR of Charred Dolomite Samples (II)

0

5

10

15

20

25

30

35

40

45

4006008001000120014001600

Wavenumber (cm-1)

Abs

orba

nce

6hr

8hr

Figure 9: FTIR spectroscopy of charred dolomite samples (II)

6.7 X-ray Diffraction

The X-ray Diffraction technique provides data, in the form of fingerprint

spectrum, characteristic of the minerals present in the material. To

investigate in detail the effect of the charring process, dolomite samples were

analysed using x-ray diffraction (XRD) and the resultant scans are presented

in this section.

Figure 10: Crystalline Structure of Untreated Dolomite

The first scan analysed was for untreated dolomite (figure 10). As expected,

the scan indicates that dolomite has a very crystalline structure and the

presence of a small amount of natural calcite (single calcium carbonate)

impurity in the samples.

Calcite

Dolomite


Figure 11: The effect of 30min charring on the Dolomite structure

The XRD data relating to 30min (@800°C) char sample, figure 11, show a

reduction in the presence of dolomite compared to the untreated dolomite

sample (figure 10). This reduction is by almost a half, with the count falling

from 14000-7000. The presence of dolomite in this 30min char sample

confirms what was suggested in the FTIR results (figure 8 & 9) that this is not

a sufficient amount of time for the decomposition of the calcium-magnesium

carbonate structure of the dolomite.

Figure 12: The effect of 1hr charring on the Dolomite structure

From the XRD data relating to 1hr char (@800°C) sample, figure 12, it can

be seen that only a very small amount of the dolomite structure remains, with

the count falling from 7000 to 600. The decomposition of the dolomite

structure requires more than 1 hour at this char temperature.

XRD Graph of Dolomite (1hr Char @ 800°C)

0

1000

2000

3000

4000

5000

6000

0 10 20 30 40 50 60 70

2 Theta

Co

un

tCalcite

Dolomite

Dolomite

Calcite


Figure 13: The effect of 2hr charring on the Dolomite structure

From figure 13, the XRD scan shows that the complete decomposition of the

dolomite structure has occurred at this char time. It can also be noted that

over the three char times 30mins, 1hr and 2hr, the presence of calcite has

increased with counts of 1700, 5000 and 7800 respectively. This suggests

that calcite is one of the main components gained by the decomposition of

the calcium-magnesium carbonate structure.

Further XRD investigation into the other char temperatures (750°C & 850°C)

and the decomposition of the dolomite was completed. The XRD scans

relating to the different char temperatures are shown in figures 14-17. As

expected, the higher char temperature correlates to the more rapid

decomposition of the dolomite. At the lower char temperature (figures 14 &

15), this point was observed at 4 hours, while for the higher char temperature

(figures 16 & 17), it was noted at 1 hour.

Figure 14: The effect of 2hr (@750°C) charring on the Dolomite structure


0

2000

4000

6000

8000

10000

0 10 20 30 40 50 60 70

2 Theta

Co

un

t


0

2000

4000

6000

8000

0 10 20 30 40 50 60 70

2 Theta

Co

un

tCalcite

Calcite Dolomite


Figure 15: The effect of 4hr (@750°C) charring on the Dolomite structure

Figure 16: The effect of 30min (@850°C) charring on the Dolomite structure

Figure 6.15: The effect of 1hr (@850°C) charring on the Dolomite structure

6.8 Surface Area Analysis

Analysis of all samples produced was carried out using the Nova 4200e,

Surface area and pore size analyser and Quantacrome software. By use of

standard isotherm models, it was possible to interpret the adsorbed data

obtained to calculate the adsorbent BET surface area.


0

2000

4000

6000

8000

0 10 20 30 40 50 60 70

2 Theta

Co

un

t


0

2000

4000

6000

8000

10000

0 10 20 30 40 50 60 70

2 Theta

Co

un

t

XRD Graph of Dolomite (30min Char @ 850°C)

0

2000

4000

6000

8000

0 10 20 30 40 50 60 70

2 Theta

Co

un

t

Calcite Dolomite

Calcite

Calcite


Figure 18: Sample Isotherm of Charred Dolomite

The isotherm developed by the Nova indicates that the dolomite chars are

Type II isotherms. Reversible Type II isotherms are generally observed

when the adsorbent concerned has a wide range of pore sizes. The shape

of the plot indicates unrestricted monolayer-multilayer adsorption, where the

point of inflexion, at the start of a nearly linear section, indicated where

monolayer coverage is complete and multilayer coverage commences. Type

II isotherms are also typical of physical adsorption.

Figure 19: Sample Isotherm of Washed Charred Dolomite

Figure 19 displays a typical isotherm observed for the borax washed charred

samples exhibit a similar type II isotherm. The presence of a type A

Sample Isotherm of Charred Dolomite

0

2

4

6

8

10

12

0 0.2 0.4 0.6 0.8 1 1.2

Relative Pressure (P/Po)

Vo

lum

e (c

c/g

) Adsorption

Desorption

Sample Isotherm of Borax Washed Dolomite

0

2

4

6

8

10

12

14

16

0 0.2 0.4 0.6 0.8 1 1.2

Relative Pressure (P/Po)

Vo

lum

e (

cc/g

)

Adsorption

Desorption


hysteresis between the adsorption and desorption isotherm, correlates to an

adsorbent which have slit shaped pores due to the sorbent being formed

from an aggregate of plate like particles.

As previously stated, from the isotherm data obtained, the BET surface area

can be determined. The BET values derived for the adsorbents studied are

regarded as being amenable since all the isotherms obtained were

essentially Type II in nature. Table 4 is a summary of the surface area

results for all dolomite chars, borax washed chars and untreated dolomite

Char

Time

(hrs) 750 800 850 750 800 850

0.5 1.35 2.48 4.63 2.91 2.03 1.88

1 2.92 4.44 5.05 2.46 3.72 4.16

2 3.58 4.74 4.00 4.99 5.49 5.83

4 5.81 7.00 5.80 6.60 8.63 8.83

6 5.01 5.73 6.28 6.27 7.89 8.60

8 5.19 6.12 7.10 4.62 10.84 10.31

12 4.38 7.43 9.98 4.69 11.88 9.92

Untreated Dolomite 1.36 m2/g

Char Temperature (°C)

Dolomite Charred Samples

Char Temperature (°C)

Washed Charred Samples

Table 4: Summary of Surface Area (m2/g) results observed for the various Dolomite Samples

Figure 22 shows how the BET surface area observed for the dolomite

charred samples varied. The untreated dolomite sample was found to have

a BET surface area of 1.36m2/g. It can be seen from figure 20 that charring

the dolomite greatly increased the BET surface area.

Figure 20: The correlation between Surface Area and the char duration of the Dolomite

Surface Area Of Dolomite Chars

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 2 4 6 8 10 12 14

Char Time (hrs)

BE

T (

m2/g

)

750°C

800°C

850°C


There are two areas of interest in figure 20 for each char temperature (750,

800 & 850°C). Firstly the results obtained from 0.5-4hrs char times, were

each temperature trend contains both peaks and troughs. This period of

time relates to the decomposition of the calcium-magnesium carbonate

structure of the dolomite. At these points, the structure is undergoing the

most significant changes which results in the most likely explanation for

these observations.

Secondly the results obtained from 6-12hrs char times. For the 800°C and

850°C char temperatures, the surface area trends increase rapidly at this

point however for 750°C char temperature the surface area gradient levels

off. This suggests that at the higher char temperature at this time period of

charring the decomposition of the remaining calcium carbonate structure has

initiated however at this lower char temperature this has not occurred.

6.9 Scanning Electron Microscope

The topography (visible analysis) of the surface of the samples was carried

out using a scanning electron microscope (SEM). SEM is a microscope that

uses electrons rather than light to form an image. There are many

advantages associated with the SEM in comparison to a standard light

microscope. Electron micrographs of the surface of each material and are

typical of the overall surface of each sample are represented in figures 21-

24. These include untreated dolomite and a number of char times (@800°C)

at two magnifications.


Figure 21: Untreated dolomite at 1000 X 25mm

Figure 21 shows the SEM of the untreated dolomite sample. It can be seen

that although the surface seems quite rough in nature, the dolomite itself is

quite homogenous, with little porosity in evidence.

Figure 22: 30min char at 1000 X 25mm

Figure 22 shows the SEM of the 30min char (@800°C) sample. It can be

seen that due to the charring process, small cracks have appeared

throughout the structure.


Figure 23: 1 hr char at 1000 X 25mm

Figure 24: 1 hr char at 2000 X 25mm

Figures 23 and 24 shows SEM‟s of 1hr char (@800°C) sample. It can be

seen that this char time the appearance of cracks and cavities. This would

confirm the macroporous nature of the dolomite displayed in the Type II

isotherm study.

6.10 Mechanical Strength

From the analysis already completed, included the SEMs, it has been noted

that the dolomite structure undergoes a large amount of change during the

charring process. The decomposition of the dolomite can be visually seen,

as the charred sample become more powder-like at the longer char times.


The mechanical strength of the dolomite charred samples were analysed

using a Texture Analyser by means of a Crush Test. The strength or

crushability of the dolomite charred samples is an important factor when

considering scale-up column work or industrial applications.

Figure 25: A graph which displays the effect of the Charring Process on the Mechanical

Strength of Dolomite

From figure 25, it can be seen that, at char time of 0.5 hours, there is a large

decline in mechanical strength with little variation between the char

temperatures (750°C, 800°C & 850°C).

Generally as the char time increases the mechanical strength of the samples

continues to decline. It is noted that the effect of the higher char temperature

(850°C) is more significant than the other char temperatures, with the

mechanical strength of the samples becoming undetectable after a char time

of 6hours.

7.0 Static Equilibrium Isotherm Determination

The method to determine the equilibrium isotherms of the adsorbents

studied, with CO2, NO2 and SO2 (single component), has been outlined in

greater detail in section 5. This section describes the isotherms observed for

the various dolomite adsorbents studied and compares them against other

commercial adsorbents.


7.1 CO2 Analysis

7.1.1 The Isotherm Observed:

A typical graph is shown below (figure 26); this demonstrates a Type II

isotherm. A typical type II isotherm is „concave to P/Po axis then almost

linear and finally convex to the P/Po axis‟ (7). The observed isotherms for CO2

obtain a small degree of the concave to the P/Po axis however the

description fits well subsequently.

A Typical Example of Isotherm Obtained

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

0.00 0.20 0.40 0.60 0.80 1.00

P/Po

Gas U

pta

ke (

km

ol/g

)

Figure 26: A graph which displays a representative example of the experimental isotherms observed.

This type of isotherm corresponds to previous work completed using

Nitrogen. The Type II isotherms are obtained with macroporous adsorbents,

which allow unrestricted monolayer – multilayer adsorption to occur at high

partial pressures.


7.1.2 Carbon Dioxide Uptake:

CO2 Isotherms for 750oC Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

0.00 0.20 0.40 0.60 0.80 1.00

P/Po

Gas U

pta

ke

(km

ol/

g)

1h750

4h750

8h750

Figure 27: This graph shows the gas uptake (Kmol/g) of Carbon Dioxide on the

chars thermally treated at 750°C

CO2 Isotherms for 800°C Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

1.4E-05

0.00 0.20 0.40 0.60 0.80 1.00

P/Po

Gas

Up

take

(k

mo

l/g

)

1h800

4h800

8h800

Figure 28: This graph shows the gas uptake (Kmol/g) of Carbon Dioxide on the


The isotherms observed from the adsorbents charred at 750°C (figure 27)

follow a comparable trend, with many points overlapping at lower partial

pressures. The sample with the highest gas uptake (1.017x10-5 kmol/g) was

the 4h char. This result correlates to the surface area data obtained from

section 6.8. The surface area determined for the 4h char sample was

5.81m2/g.

In the case of the 800°C chars, the 8h char having as expected a greater gas

uptake capacity overall. The 1h and 4h char isotherms merged over the

entire range of partial pressures. The 8h char (1.27x10-5 kmol/g) had a


greater gas uptake than the 4h char (1.036x10-5 kmol/g) however the surface

area for the 4h char was larger at 7.00 m2/g than the 8h char at 6.12m2/g.

CO2 Isotherms for 850oC Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

1.4E-05

0 0.2 0.4 0.6 0.8 1

P/Po

Gas U

pta

ke (

km

ol/g

)1h850

4h850

8h850

Figure 29: This graph shows the gas uptake (Kmol/g) of Carbon Dioxide on the chars thermally treated at 850°C

CO2 Isotherm for Untreated Dolomite

0.0E+00

2.0E-03

4.0E-03

6.0E-03

8.0E-03

1.0E-02

1.2E-02

0.00 0.20 0.40 0.60 0.80 1.00

P/Po

Gas U

pta

ke (

km

ol/g

)

Figure 30: This graph shows the gas uptake (Kmol/g) of Carbon Dioxide on the thermally

untreated dolomite

The isotherms observed from the adsorbents charred at 850°C also are very

similar and followed the same trend (figure 29). The adsorbent with the

highest uptake of gas was the 8h char (1.26x10-5 kmol/g). This sample is

also the char with the largest surface area at 7.10m2/g.

The untreated dolomite isotherm also observed the same trend (figure 30) as

all other samples analysed. The gas uptake of this adsorbent (9.708x10-6

kmol/g) is notably lower to the other values stated in this section. This also

corresponds to its lower surface area at 1.36m2/g compared to the other

samples.


The adsorbent with the largest surface area was the 8h 850°C, which along

with the 8h 800°C sample, obtained the highest gas uptake over all samples

investigated.

7.2 NO2 Analysis




linear and finally convex to the P/Po axis‟ (7). The observed isotherms for NO2

lack the initial concave to the P/Po axis however the description fits

subsequently.


y = 6E-06x + 2E-07

R2 = 0.9993

0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

5.0E-06

6.0E-06

7.0E-06

0.0 0.2 0.4 0.6 0.8 1.0P/Po

Ga

s u

pta

ke

(k

mo

l/g

)

Figure 31: A graph which displays a representative example of the experimental isotherms

observed.




partial pressures.


7.2.2 Nitrogen Dioxide Uptake:

NO2 Isotherms for 750°C Chars

0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

5.0E-06

6.0E-06

7.0E-06

8.0E-06

0 0.2 0.4 0.6 0.8 1

P/Po

Ga

s U

pta

ke

(k

mo

l/g

)

1h750

4h750

8h750

Figure 32: This graph shows the gas uptake (kmol/g) of Nitrogen Dioxide on the



0.0E+00

1.0E-06

2.0E-06

3.0E-06

4.0E-06

5.0E-06

6.0E-06

7.0E-06

8.0E-06

0 0.2 0.4 0.6 0.8 1

P/Po

Ga

s U

pta

ke

(k

mo

l/g

)

1h800

4h800

8h800



The isotherms observed from the adsorbents charred at 750°C (figure 32). In

particular, the 1h and 8 h char times resulted in similar trends with the 8h

char having as expected a greater gas uptake capacity overall than the 1 h

char. However, the 4h char, initially (low partial pressures) mapped

alongside the 8h and at higher partial pressures verged closer to the 1h char.

In the case of 800°C (figure 33), all three char times gave comparable

trends. At partial pressures below 0.5, the gas uptake capacity increased in

the order of 1h, 4 h and 8h, respectively. However at higher partial


pressures the 1h and 8 h char times, merged while the 4 h char gas uptake

fell below that of both other char times.


0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

0 0.2 0.4 0.6 0.8 1P/Po

Ga

s U

pta

ke

(k

mo

l/g

)

1h850

4h850

8h850

Figure 34: This graph shows the gas uptake (kmol/g) of Nitrogen Dioxide on the chars thermally treated at 850°C

NO2 Isotherm for Untreated Dolomite

0.0E+00

5.0E-07

1.0E-06

1.5E-06

2.0E-06

2.5E-06

3.0E-06

3.5E-06

4.0E-06

4.5E-06

0.00 0.20 0.40 0.60 0.80 1.00P/Po

Ga

s U

pta

ke

(k

mo

l/g

)


thermally untreated dolomite

The isotherms observed from the adsorbents charred at 850°C also gave

comparable trends (figure 34). However, the 1h and 4h char times are

merging over the entire partial pressures range. The 8h char as expected

has a substantially higher gas uptake than the 1h and 4h char times.

For all three char temperatures, 750°C, 800°C and 850°C the adsorbent

charred for 8 h obtained the greatest adsorption capacity, 7.06x10-6, 6.83x10-

6 and 9.93x10-6 kmol/g respectively.


The untreated dolomite isotherm also observed a similar trend (figure 35) to

that of the other samples analysed. The gas uptake for this adsorbent,

4.23x10-6 kmol/g is notably lower to the other values obtained.

7.3 SO2 Analysis




linear and finally convex to the P/Po axis‟ (7). The observed isotherms for SO2

lack the initial concave to the P/Po axis however the description fits

subsequently.


y = 1E-05x - 2E-06

R2 = 0.9928

-2.0E-06

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

0.0 0.2 0.4 0.6 0.8 1.0

P/Po

Gas U

pta

ke (

km

ol/g

)

Figure 7.36: A graph which displays a representative example of the experimental isotherms

observed.




partial pressures.


7.3.2 Sulphur Dioxide Uptake

SO2 Isotherms for 750°C Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

0 0.2 0.4 0.6 0.8 1P/Po

Gas U

pta

ke (

km

ol/g

)

1h750

4h750

8h750

Figure 37: This graph shows the gas uptake (kmol/g) of Sulphur Dioxide on the chars

thermally treated at 750°C

SO2 Isotherms for 800°C Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

0 0.2 0.4 0.6 0.8 1P/Po

Gas U

pta

ke (

km

ol/g

)

1h800

4h800

8h800



The isotherms observed from the adsorbents charred at 750°C (figure 37)

follow the same trend, with many points overlapping initially. The sample

with the highest gas uptake (8.972x10-6 kmol/g) was the 4h char. This result

correlates to the surface area data obtained from the Nova. The surface

area determined for the 4h char sample was 5.81m2/g.

In the case of 800°C (figure 38), all three char times gave comparable

trends. At lower partial pressures (below 0.4), the gas uptake capacity

increased in the order of 1h, 8 h and 4h, respectively. However at the higher


partial pressures the 8h and 4 h char times merged, while the 1h char gas

uptake fell below that of both other char times.

SO2 Isotherm for 850°C Chars

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

0 0.2 0.4 0.6 0.8 1P/Po

Gas U

pta

ke (

km

ol/g

)1h850

4h850

8h850



SO2 Isotherm for Untreated Dolomite

0.0E+00

2.0E-06

4.0E-06

6.0E-06

8.0E-06

1.0E-05

1.2E-05

0.0 0.2 0.4 0.6 0.8 1.0

P/Po

Gas U

pta

ke (

km

ol/g

)

Figure 40: This graph shows the gas uptake (kmol/g) of Sulphur Dioxide on the thermally

untreated dolomite

The isotherms observed from the adsorbents charred at 850°C also gave

comparable trends (figure 39). Each isotherm is distinct and the 8h char as

expected has a substantially higher gas uptake than the 1h and 4h char

times.

For the higher char temperatures, 800°C and 850°C the adsorbent charred

for 8 h obtained the greatest adsorption capacity, 8.565x10-6 and 1.133x10-5

kmol/g respectively. However for the char temperature of 750°C the greatest

adsorption capacity was observed was the 4h char, 8.972x10-6 kmol/g, which

coincides with the higher surface area.


The untreated dolomite isotherm also observed a similar trend (figure 40) to

that of the other samples analysed. The gas uptake for this adsorbent,

1.033x10-5 kmol/g is notably higher than values obtained for dolomite chars

of lower char time.

7.3.3 SEM: INCA Probe

The SEM unit has an INCA Probe, which allows the ability to scan the

sample surface for the presence of elements and calculate the atomic

percentage of the sample. Samples treated by CO2, NO2 and SO2 were

investigated however only SO2 treated samples obtained significant results.

Sulphur Calcium Magnesium Carbon Oxygen

5.27 7.65 1.12 18.47 65.19

1.19 7.28 2.09 25.03 63.90

0.71 14.13 2.62 21.10 61.01

/ 13.98 10.04 19.73 56.36

1.21 6.53 7.57 25.54 59.15

0.05 4.04 10.25 28.21 57.44

1.02 9.92 16.18 / 72.88

0.38 3.42 6.42 36.15 53.65

0.62 9.14 8.74 18.64 62.86

0.28 15.51 14.54 / 69.67

/ 6.00 5.43 25.34 62.82

8h850

Untreated Dolomite

4h800

8h800

1h850

4h850

1h750

4h750

8h750

1h800

Atomic PercentageDolomite Sample

(SO2 Treated)

Non-charred

Table 6: SEM-INCA probe data observed for the various dolomite samples

From table 6, it can be seen that the atomic percentage for untreated

dolomite contains no sulphur present, therefore any sulphur present in the

remaining samples are due to the SO2 treatment.

Non-charred dolomite sample treated with SO2 was substantially higher than

any of the charred dolomite samples. Generally the lower char times and

char temperatures tended to have the greater percentage of sulphur present.

Figure 41 shows the SEM of the non-charred dolomite sample treated with

SO2. It can be noted that the surface of the dolomite has a covering of

needle-like crystals; this confirms the formation of sulphate/sulphite

compounds.


Figure 41: SEM of Non-charred dolomite surface treated with SO2.

Similar work was completed for the commercial adsorbents. Activated

carbon was the only adsorbent to show the presence of sulphur. The atomic

percentage, 1.53%, was a smaller amount than that observed for the non-

charred dolomite sample but similar to the dolomite charred samples.

7.4 Comparison between the Gases Analysed

This section will discuss the adsorption capacity of the adsorbents with

respect to SO2, CO2 and NO2. A summary of results for all gases and

adsorbents investigated are displayed in the Graphs 42 - 45. These results

related closely to the surface area of each sample therefore these results are

also included in Table 7.

The isotherms observed for the adsorption of CO2 have comparable trends

and deviate little between the different adsorbents (figure 42). The results

indicate that the greater capacity for adsorption is related to the longer char

times and higher char temperatures, that is the 8h800°C and 8h850°C chars.


Figure 42: This graph shows the gas uptake (mg/g) of Carbon Dioxide on the thermally

treated dolomite

Figure 43: This graph shows the gas uptake (mg/g) of Nitrogen Dioxide on the thermally

treated dolomite

The isotherms observed for the adsorption of NO2 (figure 43) have a more

linear trend compared to that obtained for CO2. Also the isotherms tend to

be quite distinct at lower partial pressures with the individual isotherm less

uniformed over the range of chars. The adsorbent 8h800°C obtained the

greatest adsorption capacity however two other chars, 4h850°C and

4h800°C were equally as effective.


Figure 44: This graph shows the gas uptake (mg/g) of Nitrogen Dioxide on the thermally

treated dolomite

The isotherms observed for the adsorption of SO2 (figure 44) display a

comparable trend to that observed for CO2 however there is a greater

deviation of the isotherms throughout the range of chars. The isotherms are

uniformed and at lower partial pressures have merging regions. The

8h850°C char has a substantially higher gas uptake than that of the other

adsorbents.

Figure 45: This graph shows the gas uptake (mg/g) of the three gases on the untreated

dolomite

The isotherms observed for the adsorption of all three gases to the untreated

dolomite (figure 45); relate the same trends discussed for the dolomite chars.

The isotherms for CO2 and SO2 are comparable however the NO2 isotherm

is again more linear. This disparity is in relation to the degree of adsorption


rather than alternative isotherm type. The adsorption capacity for untreated

dolomite is substantially greater for Sulphur Dioxide than the other gases.

Table 7: The maximum adsorption capacity (kmol/g) for the samples investigated for all three gases,

and the surface area of the samples.

When considering the maximum gas uptake (kmol/g) it is the number of

moles adsorbed compared to the isotherm were the mass (mg/g) of gas

adsorbed is considered. This distinction allows a different trend to be

observed as the molecular weight of the gases is every different. It is

apparent that the SO2 results (table 7) are substantially lower than NO2 and

CO2, which is the opposite observation of the isotherm obtained.

The adsorbent with the largest surface area was the 8h 8500C, which along

with the 8h 8000C char, obtained the highest gas uptake over all CO2

investigated chars. However the overall range of CO2 results obtained was

quite narrow 0.845-1.269 x10-5 kmol/g.

The NO2 maximum gas uptake varies considerably with char temperature,

the results observed for the 750°C char temperature is significantly lower

than the other temperatures. The 8 h 800°C char obtained the highest

adsorption capacity than any other char. The overall range is considerably

larger 0.507-1.224 x10-5 kmol/g.

Char Temp Char Time

(oC) (hrs)

750 1

4

8

800 1

4

8

850 1

4

8

1.361.033

2.91

5.81

5.19

4.44

7.00

6.12

5.05

5.80

7.10

0.784

0.644

0.897

0.832

0.652

0.852

0.857

0.959

0.988

1.133

0.971

0.507

0.603

0.706

0.896

1.171

1.224

1.000

1.206

1.269

0.845

1.043

1.256

Untreated Dolomite

Nitrogen Dioxide Sulphur Dioxide

1.017

1.104

1.036

0.929

0.986

Maximum Gas Uptake

0.993

Surface Area

(x10-5

)(kmol/g) (m2/g)

Sample

Maximum Gas Uptake Maximum Gas Uptake

(x10-5

)(kmol/g) (x10-5

)(kmol/g)

Carbon Dioxide


The extent of SO2 adsorption is directly related to the higher char

temperature and longer char time. The adsorbent with the largest surface

area was the 8h 8500C, which also obtained the highest maximum gas

uptake.

7.5 Comparison with Commercial Adsorbents Analysed

When considering the maximum gas uptake of the commercial adsorbents,

table 8 it can be seen that the Activated Carbons and Industrial Zeolite

obtained similar results for each gas investigated.

437.64

Maximum Maximum Maximum

Ind. Zeolite 1.085 1.653 1.445

14.79

Clintoptlilte 0.798 0.971 1.020 130.78

Mordenite 0.712 0.956 0.806

677.57

A.C.Broken 0.626 1.694 1.571 668.68

A.C. Pellet 0.802 1.400 1.566

Surface Area

Adsorbents (x10-5

)(kmol/g) (x10-5

)(kmol/g) (x10-5

)(kmol/g) (m2/g)

Commerical Gas Uptake Gas Uptake Gas Uptake

Carbon Dioxide Nitrogen Dioxide Sulphur Dioxide

Table 8: The maximum adsorption capacity (kmol/g) for the samples investigated for all three gases, and the surface area of the samples.

The Industrial Zeolite observed the highest value, 1.085x10-5 kmol/g, for

CO2. This valve is similar to the 4h850 charred sample which observed a

value of 1.043x10-5 kmol/g.

Activated Carbon (Broken), observed a maximum gas uptake for NO2,

1.694x10-5 kmol/g, the highest value of the commercial adsorbents. This

value was higher than any of the dolomite charred sample, the highest being

8h800 char at 1.224x10-5 kmol/g.

The Activated Carbon (Broken), observed the highest maximum gas uptake,

1.571x10-5 kmol/g, for SO2 which was substantially higher than any dolomite

charred samples. The highest maximum gas uptake value for 8h850

dolomite char was 1.133x10-5 kmol/g.


Overall the Activated Carbon and Industrial Zeolite samples obtained greater

maximum gas uptakes for NO2 and SO2 than the dolomite charred samples.

However when considering the difference in surface areas, Activated Carbon

(Broken) observed the higher value of 677.57m2/g against the highest

dolomite charred sample, a surface area of 7.10m2/g. It can be seen that the

extent of gas uptake for dolomite samples was excellent when considering

the low surface area.

8.0 Adsorption Isotherm Modelling 8.1 Summary of Langmuir Modelling

8.1.1 Comparison between the Gases Analysed

The application of the Langmuir model to the CO2, NO2 and SO2 adsorption

isotherms resulted in the model constants shown in Table 9. The constants

Nm and KL are the number of moles of adsorbate to form a monolayer and

the Langmuir coefficient, respectively. The r2 value is derived by linear

regression analysis of the fit of the linearised model expression to the

experimental data. r2 is equal to or less than 1 and the closer the value to 1

the better the fit.

When considering the Langmuir isotherm model, the higher the values of KL

and nm the better the sorbent is for the particular absorbate. The KL values

obtained for the adsorbents (table 9) vary greatly between the adsorptive

gases. The NO2 constants obtained the higher KL values and also the

greatest range, 6.066-1030.3 N-1m-2. The CO2 and SO2 constants, 1.025-

9.431 N-1m-2 and 1.092-4.395 N-1m-2 respectively, were similar and of a

narrower range.

The Nm values obtained for the SO2 adsorptive were greater than the other

two gases however the values are small and of a narrow range for all

adsobates. There is little relationship between the values of KL and Nm

observed for the samples. These values would have been expected to

increase the most for the optimum adsorbents compared to the values

observed for the adsorbents with the lower uptake of adsorbate. This was


not seen to be the case for the KL values and only slightly visible for the Nm

values.

8.4.2 Comparison with Commercial Adsorbents Analysed

When considering the Langmuir adsorption constant of the commercial

adsorbents, table 10, it can be seen that for the KL values, for the CO2 and

NO2 data, fell within the same range observed for the dolomite charred

samples. However the KL values obtained by the SO2 data, notable the

Activated Carbons values, were much higher than the values observed for

the dolomite samples.

The Langmuir Nm values observed from the commercial adsorbents were

very similar to that of the dolomite chars for each of the gases analysed. The

r2 values which represent the fit of the experimental data to the Langmuir

model data show that for NO2 and SO2 the commercial adsorbents were a

better fit than the dolomite samples.


Sample Carbon Dioxide Nitrogen Dioxide Sulphur Dioxide

Char Temp Char Time nm (x10-4

) KL r2 nm (x10

-4) KL r

2 nm (x10

-4) KL r

2

(oC) (hrs) (moles) (N

-1m

-2) (moles) (N

-1m

-2) (moles) (N

-1m

-2)

750 1 3.171 3.313 0.922 1.079 12.519 0.624 3.645 3.368 0.968

4 2.488 6.678 0.968 1.614 12.978 0.857 4.451 1.756 0.789

8 2.629 6.383 0.962 1.444 1030.3 0.922 3.394 4.395 0.891

800 1 2.62 3.443 0.936 2.025 12.288 0.886 4.264 2.354 0.955

4 3.158 3.661 0.931 1.678 16.192 0.979 3.880 2.262 0.815

8 2.731 4.981 1 1.980 198.10 0.964 3.420 3.126 0.906

850 1 4.959 1.025 0.963 2.461 6.066 0.815 5.466 1.466 0.846

4 3.008 4.287 0.958 1.427 11.394 0.854 5.844 1.092 0.781

8 2.375 9.431 0.952 2.035 7.531 0.735 3.761 3.216 0.931

Untreated Dolomite 3.156 2.963 0.948 2.318 8.804 0.92 5.320 1.697 0.778

Table 9: The Langmuir Model constants obtained from the experimental data for the gases investigated CO2, NO2 and SO2.


nm (x10-4

) KL r2

nm (x10-4

) KLr2

nm (x10-4

) KLr2

(moles) (N-1

m-2

) (moles) (N-1

m-2

) (moles) (N-1

m-2

)

3.740 1.953 0.731 1.557 9.701 0.959 2.479 17.037 0.974

1.753 6.294 0.813 2.051 41.881 0.958 3.000 401.399 0.990

2.206 7.940 0.927 2.303 18.158 0.983 3.660 3.782 0.962

2.433 3.463 0.841 1.943 30.305 0.967 3.774 3.114 0.947

2.494 5.230 0.933 2.128 18.410 0.903 3.440 3.765 0.931

Mordenite

Clintoptlilte

Ind. Zeolite

Other

Adsorbents

A.C. Pellet

A.C.Broken


Table 10: The Langmuir Model constants obtained from the experimental data for the gases

investigated CO2, NO2 and SO2.

8.5 Summary of Freundlich Modelling Data

8.5.1 Comparison between the Gases Analysed

The application of the Freundlich model gives an analytical expression for

the experimental data rather than a precise picture of the mechanism of

adsorption. The Freundlich constants, KF and nF, along with the fit coefficient

r2 are given in Table 11.

Linearisation of the model expression overall gave exceptionally good

straight-line plots. This is reflected in the high r2 values, 0.990 or above for

the adsorbates investigated for CO2 and NO2. The same degree of

linearisation is not shown for the SO2 adsorption with low r2 values ranging

from 0.776-0.963.

Generally when considering the Freundlich Isotherm Model, the higher the

value of nF and KF, the greater the amount of particular adsorbate will be

absorbed by the adsorbent. The closer the nF to zero, the greater the

heterogeneity of the adsorbent. It can be seen from the Table 11 that for the

adsorptive NO2 the nF values were the smallest and within the range of

0.727-1.390. This indicated that all the adsorbents studied were

heterogenous in nature.



Char Temp Char Time nf KF (x10-2

) r2 nf KF (x10

-3) r

2 nf KF (x10

-2) r

2

(oC) (hrs) (N

-1m

-2) (N

-1m

-2) (N

-1m

-2)

750 1 1.754 2.794 0.991 1.390 18.674 0.999 1.7541 0.02794 0.991

4 1.574 1.799 0.995 0.902 2.084 0.994 1.5741 0.01799 0.995

8 1.576 1.837 0.995 0.933 2.068 0.998 1.5758 0.01837 0.995

800 1 1.665 2.373 0.997 1.209 6.349 0.999 1.6647 0.02373 0.997

4 1.793 2.899 0.985 0.781 0.295 0.998 1.7928 0.02899 0.985

8 1.639 1.901 0.997 1.166 4.213 1 1.6385 0.01901 0.997

850 1 1.737 2.882 0.99 1.193 5.670 0.996 1.4981 0.01400 0.995

4 1.593 1.909 0.995 0.883 0.710 0.999 1.5926 0.01909 0.995

8 1.477 1.287 0.997 0.727 0.246 0.996 1.4773 0.01287 0.997

Untreated Dolomite 1.623 2.247 0.998 1.339 10.401 0.999 1.6234 0.02247 0.998

Table 11: The Freundlich Model constants obtained from the experimental data for the gases investigated CO2, NO2 and SO2


8.4.2 Comparison with Commercial Adsorbents Analyses

When considering the Freundlich adsorption constants of the commercial

adsorbents, table 12, it can be seen that for the KF values with regards to the

CO2 data, the values are similar but slightly higher than the observed values of

the dolomite samples. For NO2 and SO2 data, notable Activated Carbon, the KF

values are considerably lower than the other commercial adsorbents and the

dolomite samples.

The Freundlich nf values observed for the commercial adsorbents were similar

to that of the dolomite charred samples for all three gases investigated. The

one exception to this trend was Activated Carbon as again the values observed

for nf for NO2 and SO2 are considerably lower than the other commercial

adsorbents or the dolomite samples.

nf KF (x10-2

) r2

nf KF (x10-3

) r2

nf KF (x10-2

) r2

(N-1

m-2

) (N-1

m-2

) (N-1

m-2

)

1.846 3.306 0.990 0.654 0.043 0.985 0.966 0.066 0.990

1.709 3.332 0.985 0.669 0.043 0.983 0.979 0.076 0.994

2.094 4.987 0.973 1.296 8.164 1.000 1.680 2.048 0.997

1.863 3.249 0.992 1.182 5.178 0.999 1.657 1.767 0.998

1.775 2.470 0.991 0.831 0.336 0.992 1.601 1.226 0.998

Mordenite

Clintoptlilte

Ind. Zeolite

Other

Adsorbents

A.C. Pellet

A.C.Broken


Table 12: The Freundlich Model constants obtained from the experimental data for the gases

investigated CO2, NO2 and SO2


9.0 Trial Results

9.1 Baseline data

The baseline data was collected as described previously figures 46 & 47.

The carbon monoxide reading range between 1000 to 2000 ppm. The peaks

which are noticeable on both graphs indicate changes in the burn as fresh

material is added.

Figure 46: This graph shows the carbon monoxide baseline data

Figure 47: This graph shows the NO, NO2 & SO2 baseline data

9.2 Carbon Monoxide data

The follow graph indicates that all the materials trialled significantly reduced

the carbon monoxide reading. It had been expected that the activated

dolomite would outperform the other materials but this was not the case the

raw untreated dolomite outperformed the other materials. The only possible


explanation for this is the increased temperatures which occur in the flue as

all previous trials have been completed at room temperature.

Figure 48: This graph shows the CO data recorded for each trial

9.3 Nitrogen Dioxide and Nitrogen Monoxide data

The following figures (49 &50) illustrate the data obtained for nitrogen dioxide

and nitrogen monoxide respectively. Again there were some unexpected

results raw dolomite and activated carbon reduced the NO2 to zero and the

activated dolomite reduced the nitrogen dioxide by approximately 40%. This

was not repeated with nitrogen monoxide were all materials performed

similarly. There was no significant difference between the performance of

activated and raw dolomite.


Figure 49: This graph shows the NO2 data recorded for each trial

Figure 50: This graph shows the NO data recorded for each trial

9.4 Sulphur Dioxide data

The following figure (51) illustrates the data obtained for sulphur dioxide.

Again there were some unexpected results raw dolomite and activated

carbon reduced the SO2 to less than 3 where as the activated dolomite had

no effect on the concentration sulphur dioxide.


Figure 51: This graph shows the SO2 data recorded for each trial

Conclusions

It was evident from the experimental data that the dolomitic sorbents have an

affinity to both carbon dioxide and nitrogen dioxide. From the equilibrium

isotherms there is a difference in isothermal shape between gases. This

disparity is in relation to the degree of adsorption rather than alternative

isotherm type. The maximum gas uptake results in Table 7 indicate that

dolomitic sorbents have a higher capacity for carbon dioxide than nitrogen

dioxide. Results with respect to the untreated dolomite, show the capacity for

carbon dioxide is twice that of nitrogen dioxide. The constants determined

from the Freundlich isotherm model for both gases in Table 11, also observe

this trend.

The charring process was successful in the production of dolomite

adsorbents with high adsorption capacities. It was determined be means of

analytical and visual methods that this increase in capacity was due to the

decomposition of the calcium – magnesium carbonate structure of the

dolomite to magnesium oxide and calcium carbonate.

Prolonged charring times resulted in the decomposition of the remaining

calcium carbonate structure. This was seen to have a detrimental effect on


the mechanical strength of the material resulting in a powder-like appearance

of the samples. A compromise may have to be reached between the

adsorption capacity required and the structural integrity of the dolomite.

The charred dolomite was expected to displayed high affinity for the

adsorption of carbon dioxide but this was not the case during the site trial.

However, the unpredictably high adsorption rates achieved by the untreated

dolomite and the lack of sample preparation required, would thus

recommend itself as the appropriate sample for carbon dioxide adsorption. It

is still unconfirmed why this occurred but it is suspected that the increase

was due to the increased temperature in the flue.

Activated Carbon and untreated dolomite displayed comparatively high

adsorption capacities for the adsorption of nitrogen dioxide. The charred

dolomite samples analysed displaying little affinity to the adsorption of this

gaseous pollutant. Although the untreated dolomite resulted in marginally

lower adsorption rates, than the commercial adsorbents, dolomite could still

be a viable option for the treatment of nitrogen dioxide due to the economical

raw material and preparation costs involved with this adsorbent.

For sulphur dioxide adsorption, both Activated Carbon and untreated

dolomite displayed comparatively high adsorption capacities. The charring

process resulted in a reduction in the adsorption capacity of the dolomite

samples. The presence of sulphite/sulphite crystals on the surface of the

untreated dolomite and to a lesser extent the charred dolomite sample,

suggests that the reaction of the gas to the surface is chemisorption rather

than physisorption. As Chemisorption is reversible the recovery of the

sulphur formed on the dolomite surface could be a possibility. Currently

there is a shortage of sulphur on farming land and as the dolomite is

currently used as a soil conditioner this could be a possible added value

route for spent filter media.


References

1. Anani, A., (1984). „Applications of Dolomite‟, Industrial Minerals, 45-55

2. Kiely, G., (1997). „Environmental Engineering‟, McGraw Hill, London

3. Manahan, S.E., (1994), „Environmental Chemistry‟, Lewis, London

4. Department of Environment, Foods and Rural Affairs, UK Government.

„Air Quality Legislation‟. 5. Coulson, J.M., „Chemical Engineering. – Vol 2: Particle technology and

separation processes‟. 5th ed., Oxford, Butterworth-Heinemann. 6. Brunauer, S. et al., (1940), J. Amer. Chem. Soc., 62, 1723 7. Tien, C., (1994), “Adsorption Calculations and Modelling”. 1st ed.,

Butterworth-Heinemann, series in Chemical Engineering. 8. Groen, J.C. et al., (2003), “Microporous and Mesoporous Materials”, 60,

1-17.

9. Langmuir, I., “Adsorption of Gases on Plane Surfaces of Glass, Mica and

Platinum”, J. Am. Chem. Soc., 40, (1918), 1361-1403

10. Freundlich, H., “Adsorption in Solution”, Phys. Chemie., 57, (1907) 11. Yong, Z., Mata, V., Rodrigues, A.E., (2002), “Adsorption of carbon dioxide

at high temperatures – a review”, Separation and Purification technology, 26,195-205.

12. Squires, A.M., “Cyclic use of calcined capture dolomite to desulfurize

fuels undergoing gasification”, Adv. Chem. Ser., 69, (1967), 205-229. 13. Silaban, A., Narcida, M., Harrison, P.,”Charactertics of the reversible

reaction between CO2(g) and calcined dolomite, Chem. Eng. Commum. 146 (1996), 149-162.

14. Balasubramanian, B., Lopez-Ortiz, A., et al., “Hydrogen from methane in

a single-step process”, Chem. Eng. Sci. 54, (199), 3543-3552. 15. Seinfeld, J.H., (2004). „Air Pollution: A Half Century of Progress‟, AICHE

Journal, 50, 6, 1096-110

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Activated Dolomite Adsorption – Gaseous Effluent Treatment

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