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Unit2, module 3:

Industry and the Environment Locating industrial plants; benefits and risk

Industrial location is an increasingly important decision facing both national and international firms. The

general critical factors of industrial location are transportation, labor, raw materials, markets, industrial sites,

utilities, government attitude, tax structure, climate, and community. In addition, for international location

considerations, four general factors are identified: political situation of foreign countries, global competition

and survival, government regulations, and economic factors.

Some factors which influence a plant site

1. Proximity to raw materials

2. Easily accessible to the workforce

3. Proximity to good infrastructure (seaport, railway, airport, roads)

4. Type of terrain (flat, rugged or slightly rolling hills)

5. Distance from general populace

Checkpoint A

Think of the cement factory in Rockfort, which of the factors listed above would be the most important in

relation to the location of the plant site and give reasons why.

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All industrial plants have general safety requirements. These requirements include head covering, eye

protection, feet protection, and ears as well. Industrial plants can be very hazardous; falling objects, loud noises

as well as fire protection and toxic fumes alerts. However not all safety requirements have the same level of

emphasis placed upon them

Checkpoint B

Compare a cement plant to a petroleum refinery plant. Which safety requirements would be the most critical

for each and why?

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Risk Of Accidents And / Or Harmful Exposures : Areas of Concern

Dangerous Materials ii) Hazards of Pressure

Vessels iii) Hazardous Chemical Reactions

iv) Hazardous of Unit Operations v) Flammable

Gases, Vapours And Dust Hazards

vi) Health Hazards vii) Hazards due to corrosion

viii) Entry in To Confined Spaces ix) Working

with Pipelines x) Plant Alteration and modification

xi) Sampling and Gauging xii) Hazards due to

Instrument Failures.

Dangerous Materials i)Explosives ii) Gases iii) Inflammable Liquids iv)

Inflammable Solids v) Oxidising substances

vi) Toxic and Infectious substances vii)Radio

Active Substances viii)Corrosive Substances

ix)Miscellaneous Dangerous Substances

Hazards Due To Corrosion Weakening and falling of structures and sheds.

Falling of workers from height due to breaking of

raised platforms, hand rails, toe boards, stairs and

ladders.

Spills and toxic releases from pipelines due to

corrosion.

Leakages and bursting of vessels due to corrosion.

Entry into Confined Spaces 1.Oxygen Deficiency 2. Toxic Contamination

3. Flammable Environment4.Possibility of

Electrocutions through electric

equipments5.Possibility of Toxic gas

generation during the work 6.Lack of

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Hazards Of Pressure Vessels 1.Leakage or Bursting of Pressure Vessels

2.Design defects 3.Failure of Relief Systems

4.Lack of hydraulic testing. 5. Lack of Proper

Instrumentation or Instrumentation Failure 6.Lack

of N.D.Tests 7.Corrosion of Vessels. 8. Lack of

routine inspections 9. Attempt of Pneumatic

testing

Ventilation 7.Difficulty in welfare monitoring

8.Failure to escape on emergency

9.Combustible Substances

GENERAL SAFETY REQUIREMENTS FOR INDUSTRY

Hazardous Chemical Reactions Understanding about the behaviours of reactions

and adopting precautionary and emergency

measures

Hazards of Unit operations Understanding the hazards inherent in each unit

operation and adopting precautionary and

emergency measures.

Flammable Gases, Vapours And Dust

Hazards • Identification of potential areas, where possibility

of flammable mixture are possible.

• Efforts to avoid hazardous mixtures, by inert gas

purging and other methods.

• Declaring hazard zones and providing flame proof

electrical fittings and equipments.

• Providing Explosion Vents in spaces with

possibility of air-vapour mixtures.

• Explosive meter testing.

• Providing adequate fire control devices.

• Providing arrangements to avoid static sparks. Etc.

• Corrosion monitoring and control.

• Testing and inspection of vessels and

structures to ensure safety

Safety While Entry into Confined Spaces

Thorough cleaning and purging before hot work.

Safety belt with one end outside.

Life line to monitor welfare.

On going ventilation.

A person to watch the welfare.

Low voltage electric appliances.

Self contained breathing apparatus.

Environmental monitoring for oxygen, toxic gases

and flammable gases before entry.

Pipeline isolation before entry

Electric isolation before entry.

Proper ladder for entry.

Health Hazards • Identification of potential health hazards.

• Assessment of levels of physical and chemical health

hazards.

• Control of hazards by various techniques

• Adequate awareness among the workers.

• Periodic medical examination of the workers.

• Personal protection for occasional exposures.

• Proper hygiene and decontamination facilities. etc.

ALUMINIUM

Extracting aluminium from bauxite

Aluminium is too high in the electrochemical series (reactivity series) to extract it from its ore using carbon reduction. The temperatures needed are too high to be economic.

Instead, it is extracted by electrolysis. The ore is first converted into pure aluminium oxide by the Bayer Process, and this is then electrolysed in solution in molten cryolite - another aluminium compound. The aluminium oxide has too high a melting point to electrolyse on its own.

Aluminium ore

The usual aluminium ore is bauxite. Bauxite is essentially an impure aluminium oxide. The major impurities include iron oxides, silicon dioxide and titanium dioxide.

Purifiying the aluminium oxide - the Bayer Process

Reaction with sodium hydroxide solution

Crushed bauxite is treated with moderately concentrated sodium hydroxide solution. The concentration, temperature and pressure used depend on the source of the bauxite and exactly what form of aluminium oxide it contains. Temperatures are typically from 140°C to 240°C; pressures can be up to about 35 atmospheres.

High pressures are necessary to keep the water in the sodium hydroxide solution liquid at temperatures above 100°C. The higher the temperature, the higher the pressure needed.

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With hot concentrated sodium hydroxide solution, aluminium oxide reacts to give a solution of sodium tetrahydroxoaluminate.

The impurities in the bauxite remain as solids. For example, the other metal oxides present tend not to react with the sodium hydroxide solution and so remain unchanged. Some of the silicon dioxide reacts, but goes on to form a sodium aluminosilicate which precipitates out.

All of these solids are separated from the sodium tetrahydroxoaluminate solution by filtration. They form a "red mud" which is just stored in huge lagoons (mud lakes).

Precipitation of aluminium hydroxide

The sodium tetrahydroxoaluminate solution is cooled, and "seeded" with some previously produced aluminium hydroxide. This provides something for the new aluminium hydroxide to precipitate around.

Formation of pure aluminium oxide

Aluminium oxide (sometimes known as alumina) is made by heating the aluminium hydroxide to a temperature of about 1100 - 1200°C.

Conversion of the aluminium oxide into aluminium by electrolysis

The aluminium oxide is electrolysed in solution in molten cryolite, Na3AlF6. Cryolite is another aluminium ore, but is rare and expensive, and most is now made chemically.

The electrolysis cell

The diagram shows a very simplified version of an electrolysis cell.

The electrode reactions

This is the simplification:

Aluminium is released at the cathode. Aluminium ions are reduced by gaining 3 electrons.

Oxygen is produced initially at the anode.

However, at the temperature of the cell, the carbon anodes burn in this oxygen to give carbon dioxide and carbon monoxide.

Continual replacement of the anodes is a major expense.

Although the carbon lining of the cell is labelled as the cathode, the effective cathode is mainly the molten aluminium that forms on the bottom of the cell.

Molten aluminium is syphoned out of the cell from time to time, and new aluminium oxide added at the top.

The cell operates at a low voltage of about 5 - 6 volts, but at huge currents of 100,000 amps or more. The heating effect of these large currents keeps the cell at a temperature of about 1000°C.

Economic considerations

The high cost of the process because of the huge amounts of electricity it uses. This is so high because to produce 1 mole of aluminium which only weighs 27 g you need 3 moles of electrons. You are having to add a lot of electrons (because of the high charge on the ion) to produce a small mass of aluminium (because of its low relative atomic mass).

Energy and material costs in constantly replacing

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the anodes. Energy and material costs in producing the cryolite,

some of which gets lost during the electrolysis. Transport of the finished aluminium.

Extracting aluminium from the bauxite

Loss of landscape due to the size of the chemical plant needed, and in the production and transport of the electricity.

Noise. Atmospheric pollution from the

various stages of extraction. For example: carbon dioxide from the burning of the anodes (greenhouse effect); carbon monoxide (poisonous); fluorine (and fluorine compounds) lost from the cryolite during the electrolysis process (poisonous).

Pollution caused by power generation (varying depending on how the electricity is generated.)

Disposal of red mud into unsightly lagoons.

Environmental problems in mining and transporting the bauxite

Loss of landscape due to mining, processing and transporting the bauxite.

Noise and air pollution (greenhouse effect, acid rain) involved in these operations

Recycling

Saving of raw materials and particularly electrical

energy by not having to extract the aluminium from

the bauxite. Recycling aluminium uses only about

5% of the energy used to extract it from bauxite.

Avoiding the environmental problems in the

extraction of aluminium from the bauxite.

Not having to find space to dump the unwanted

aluminium if it wasn't recycled.

(Offsetting these to a minor extent) Energy and

pollution costs in collecting and transporting the

recycled aluminium.

Uses of aluminium

Aluminium is usually alloyed with other elements such as silicon, copper or magnesium. Pure aluminium isn't very strong, and alloying it adds to it strength.

Aluminium is especially useful because it

has a low density; is strong when alloyed; is a good conductor of electricity; has a good appearance; resists corrosion because of the strong thin layer of aluminium oxide on its surface. This

layer can be strengthened further by anodising the aluminium.

Anodising essentially involves etching the aluminium with sodium hydroxide solution to remove the existing oxide layer, and then making the aluminium article the anode in an electrolysis of dilute sulphuric acid. The oxygen given off at the anode reacts with the aluminium surface, to build up a film of oxide up to about 0.02 mm thick.

As well as increasing the corrosion resistance of the aluminium, this film is porous at this stage and will also take up dyes. (It is further treated to make it completely non-porous afterwards.) That means that you can make aluminium articles with the colour built into the surface.

Some uses include:

aluminium is used for because

aircraft light, strong, resists corrosion

other transport such as ships' superstructures, container vehicle bodies, tube trains (metro trains)

light, strong, resists corrosion

overhead power cables (with a steel core to strengthen them)

light, resists corrosion, good conductor of electricity

saucepans light, resists corrosion, good appearance, good conductor of heat

firefighter suits High reflective nature

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Checkpoint C

CRUDE OIL

Fractional distillation of crude oil is the first step in the production of many of the materials we have come to rely on in modern life.

All our fossil fuels, virtually all our plastics, detergents and commercial alcohols are

made from products of this process.

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Fractional Distillation of Crude Oil

In order to separate the different length chains in the crude mix, it is heated to a very high temperature. The

temperature is set so that all those fractions with a Carbon chain length of 20 and below are evaporated from the

crude mix. The temperature cannot be set higher than this as there is a risk that the lighter fractions will ignite.

The remaining liquid, which is composed of only the heavier fractions, passes to a second location where it is

heated to a similar temperature, but at lower pressure. This has the effect of making the heavy Hydrocarbon

fractions more likely to evaporate.

How the Distillation Tower Works

The way the Distillation Tower works is by becoming progressively cooler from the base to the top. All the

Hydrocarbon fractions start off in gas form, as they have been heated to that point. The gases then rise up the

tower.

The gas mixture then encounters a barrier through which there are are only

openings into the bubble caps. The gas mixture is then forced to go through a

liquid before continuing upwards. The liquid in the first tray is at a cool enough

temperature to get the heaviest gas fractions to condense into liquid form, while

the lighter fractions stay gaseous.

In this way the heaviest hydrocarbon fractions are separated out from the mixed

gas. The remaining gas continues its journey up the tower until it reaches another

barrier. Here the bubble cap process is repeated but at a lower temperature than before, which then filters out

the next lightest set of fractions.

This process continues until only the very lightest fractions, those of 1 to 4 Carbon atoms, are left. These stay in

gas form and are collected at the top of the tower.

The separation of the heavier elements in the second tower follows exactly the same process but at lower

pressure.

After the Fractional Distillation of Crude Oil

The separated fractions still contain a mixture of different hydrocarbons. After their initial separation the

fractions require further processing and purification. Treatment of the initial products of the fractional

distillation of crude oil also occurs in the refinery. The results of these processes are the products we use in

everyday life.

Uses of Crude Oil

In reality, crude oil is a much larger part of our lives than many of us realize. There are more than 4,000

different petrochemical products. These products are manufactured by refining crude oil.

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Here are some common products that are made from oil:

Gasoline

Diesel fuel

Heating oil

Jet fuel

Bunker fuel

Paint

Fertilizers/pesticides

Plastics

Synthetic rubber

Synthetic fibers

Fertilizers/pesticides

Dyes

Detergent

Photographic film

Food additives (canned food)

Medicine

Synthetic fibers (such as polyester,

nylon, acrylic)

Make-up

Candles

The Impact Of The Petroleum Industry On The Environment

ACCIDENTS: Oil rig accidents, broken pipelines, oil

tanker wrecks etc. all have terrible effects on the plant

and animal life of the locality as we see from the

horrible TV pictures of seabirds coated in oil, and

toxic oil slicks covering the beaches and sands. There

is also the risk to humans from fires and explosions on

rigs or at oil refinery installations and fuel storage

depots etc.Thick oil smothers animals such as birds

and sea otters. It clogs the feeding and breathing

mechanisms of filter-feeders. It can also poison

animals who swallow it. Over the long term, oil can

cause cancer in marine life, destroy the skin and gill

tissues of fishes, upset their equilibrium, and disrupt

the chemical receptors in lobsters and fish that are

necessary for attracting mates.

RISING CARBON DIOXIDE LEVELS:

THE GREENHOUSE EFFECT: (see notes on the

atmosphere below)

ACID RAIN: Fossil fuels contain compounds of the

element sulphur When the fuel is burned the sulphur

compounds also burn to form sulphur dioxide. This is

an acidic gas and dissolves in rainwater, it then reacts

with water and oxygen to form a very dilute solution

of sulphuric acid.

sulphur + oxygen ==>sulphur dioxide

S(in fuel molecules) + O2(g) ==> SO2(g)

Sulphur dioxide is a harmful gas and lung irritant and

contributed to 5000 extra deaths in the great 'London

Smog' in the 1950's as well as being a major acid-rain

gas. It reacts with oxygen (in air) and water (rain) and

gets oxidised to form very dilute sulphuric acid - acid

rain and the overall change is represented by the

equation below.

SO2(g-air) + O2(g-air) + 2H2O(l-rain) ==> 2H2SO4(aq-rain)

The formation of acid rain has several bad effects on

the environment e.g.

the low pH causes plant damage, particularly trees,

kills certain life forms and so damages eco cycles and

food chains in rivers or lakes harming wildlife like

trout,

increases the 'weathering' corrosion rates of building

stone (particularly limestone).

OTHER POLLUTANTS: High

temperature combustion also

produces other pollutants including ...

Nitrogen oxides collectively denoted by NOx: NO is

formed in car engines and changes to NO2, which is

acidic, contributing further to acid rain (above), and

are also involved in the chemistry of 'photochemical

smog' - which produces chemicals harmful to

respiration, irritating to eyes and contributes to acid

rain. Many of the reactions are initiated by sunlight.

nitrogen monoxide is formed in high temperature

combustion situations e.g. car engines, power station

furnace burning coal, oil or natural gas.

nitrogen + oxygen ==> nitrogen monoxide

N2(g) + O2(g) ==> 2NO(g)

and in air the nitrogen monoxide rapidly combines

with the oxygen in air

nitrogen monoxide + oxygen ==> nitrogen

dioxide (acidic gas)

2NO(g) + O2(g) ==> 2NO2(g)

The nitrogen dioxide is oxidised to nitric acid by the

reaction with oxygen from air when it dissolves in

rainwater. The overall process is summarised in the

equation below.

4NO2(g-air) + O2(g-air) + 2H2O(l-rain) ==> 4HNO3(aq-rain)

Carbon monoxide CO, which is toxic, and also

involved in the chemistry of 'photochemical smog'.

This is formed by inefficient combustion

Unburned hydrocarbons, CxHy, which can be

carcinogenic and are also involved in photochemical

smog chemistry.

But catalytic converters* can significantly reduced

these three unwanted emissions (see above for CO and

NO removal, and CxHy gets oxidised to CO2 and

H2O). * e.g. using platinum-rhodium transition metal

catalysts, these are dispersed on ceramic bed to give a

big surface area for the best reaction rate.

There are other indirect pollution problems to do

with burning fossil fuels:

Lead compounds are added to petrol to improve

engine performance. This produces lead compound

emissions into the environment. Lead compounds are

nerve toxins so it is fortunate they are being phased

out in many countries.

AMMONIA

MANUFACTURE OF AMMONIA -THE HABER PROCESS

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The Haber Process combines nitrogen from the air with hydrogen derived mainly from natural gas (methane)

into ammonia. The reaction is reversible and the production of ammonia is exothermic.

A flow scheme for the Haber Process looks like

this:

Hydrogen gas is obtained by reacting methane

with steam over a nickel catalyst. This is called

steam reforming: CH4 + H2O → CO + 3 H2

Nitrogen gas is obtained via fractional distillation

of liquid air

According to Le Chatelier’s Principle, a lower

temperature and a higher pressure would increase

the yield of ammonia. However, too low a

temperature would slow the rate of the reaction

and high pressures are costly as materials must be strengthened to withstand the pressure to resist to risk of explosion.

Thus a compromise is reached, where the temperature is not too low nor too high and the pressure also not too high

but high enough to shift the equilibrium position to the right.

Under these conditions, the conversion rate to ammonia is 15%. However it occurs quickly and unreacted gases are

recycled to improve efficiency. Separating the ammonia: When the gases leave the reactor they are hot and at a very high pressure.

Ammonia is easily liquefied under pressure as long as it isn't too hot, and so the temperature of the mixture is

lowered enough for the ammonia to turn to a liquid. The nitrogen and hydrogen remain as gases even under

these high pressures, and can be recycled.

Uses of Ammonia in Agriculture and the Chemical Industry Agricultural industries are the major users of ammonia. Ammonia is a very valuable source of nitrogen that is

essential for plant growth. Depending on the particular crop being grown, up to 200 pounds of ammonia per acre

may be applied for each growing season.

1. Manufacture of fertilisers and/or used as a fertiliser itself

2. Ammonia used as a source of protein for livestock

3. Used in the manufacture of nitric acid, drugs and various textiles

4. Used in water treatment for control of pH

5. used by the leather industry as a curing agent

6. widely used as commercial and household cleaners and detergents.

The impact of the ammonia industry on the environment

Atmospheric deposition Ammonia gas which is emitted falls to the ground over land, often during rainfall. This results in terrestrial

eutrophication i.e. the enrichment of nitrogen content on land. This ultimately causes the disruption of plant

ecosystems, with a few common fast growing species to dominate over greater variety of plants often of

conversation value.

Eutrophication Over-use of ammonium fertilisers. These fertilisers are water soluble and excess is leached from the soil during

rainfall or irrigation, causing the bacterial levels in nearby water bodies to increase substantially. This large

increase in bacteria robs the water body of adequate oxygen causing other aquatic life to die.

Acid soils

The overuse of fertilisers causes the soil to become acidic. Acidic soils cannot support several crops needed

today and the soil must be neutralised before anymore crops are planted. This neutralisation must be done on a

continuous basis to ensure the viability of the soil.

Air pollution

High concentrations of ammonia in air can damage vegetation such as lichen and moss. It also contributes to the

formation of haze in the atmosphere which reduces visibility and the formation of particulate matter which can

cause respiratory problems. Checkpoint B

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SULPHURIC ACID

THE MANUFACTURE OF SULPHURIC ACID - THE CONTACT PROCESS

The process can be divided into three stages:

1. Preparation and purification of sulphur dioxide

2. Catalytic oxidation (using vanadium pentoxide catalyst) of sulphur dioxide to sulphur trioxide

3. Conversion of sulphur trioxide to sulphuric acid

Stage1: Making the sulphur dioxide

This can either be made by burning sulphur in an excess of air:

. . . or by heating sulphide ores like pyrite in an excess of air:

Purification of air and SO2 (using an electrostatic precipitator) is necessary to avoid catalyst poisoning. The gas

is then washed with water and dried by sulphuric acid.

To conserve energy, the mixture is heated by exhaust gases from the catalytic converter by heat exchangers.

Stage 2: Catalytic oxidation

Sulphur dioxide and oxygen then react in the manner as follows:

2 SO2(g) + O2(g) ⇌ 2 SO3(g) : ΔH = −197 kJ mol−1

To increase the reaction rate, high temperatures (450 °C), medium pressures (1-2 atm), and vanadium(V) oxide

(V2O5) are used to ensure a 96% conversion.

Stage3: Conversion of sulphur trioxide to sulphuric acid

Hot sulfur trioxide passes through the heat exchanger and is dissolved in concentrated H2SO4 in the absorption

tower to form oleum:

H2SO4(l) + SO3(g) → H2S2O7(l)

Note that directly dissolving SO3 in water is impractical due to the highly exothermic nature of the reaction.

Acidic vapour or mists are formed instead of a liquid.

Oleum is reacted with water to form concentrated H2SO4.

The average percentage yield of this reaction is around 30%.

H2S2O7(l) + H2O(l) → 2 H2SO4(l)

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Uses of Sulphur in Industries Microfined sulphur, and derivatives of sulphur are sprayed on plants and trees to destroy the fungus, insects,

bacteria etc. that attack them.

In chemical industries

Sulphuric acid is by far, the most important chemical produced from sulphur. Sulphuric acid is used as a basic

reagent in almost all the chemical preparations and in many industrial processes. It might well be said that the

industrial progress of a nation is directly proportional to the amount of sulphuric acid that it consumes.

Other important compounds of sulphur produced are:

Sulphur dioxide : Used in bleaching straw, wool, etc.

Calcium bisulphite : Used for bleaching wood pulp

Phosphorus trisulphide : Used in safety matches

Carbon disulphide : Used as an industrial solvent etc.

In explosive industry

Sulphur is an important constituent of explosives, like

gunpowder, fireworks and fire crackers.

In the vulcanization of rubber

Raw rubber is soft, but many commercial applications of rubber require it to be hard and resistant to wear and

tear caused through friction. For e.g., the rubber of automobile and aeroplane tyres is very hard. Vulcanization is

the process where raw rubber is boiled with sulphur to make it hard. It is named after Vulcan, the Roman god of

"fire".

Practice Questions

ETHANOL: Making ethanol by fermentation

This method only applies to ethanol. You can't make any other alcohol this way.

The process: To manufacture alcoholic beverages, there are essentially two processes that must occur:

fermentation to produce the alcohol and then distillation to purify and increase the alcohol content.

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Yeast is added to a sugar source e.g. sugarcane, molasses, grapes etc with various nutrients and the correct

temperature and pH and in the absence of oxygen. Sugar is first broken down into glucose and fructose by the

enzyme sucrase. Eventually glucose molecules are respired anaerobically to produce ethanol and carbon

dioxide gas by the enzyme zymase.

C6H12O6 → 2C2H5OH + 2CO2

The ethanol content rises as high as 12% before the yeast cells are killed.

Yeast is killed by ethanol concentrations in excess of about 15%, and that limits the purity of the ethanol that can be produced. The ethanol is separated from the mixture by fractional distillation to give 96% pure ethanol.

For theoretical reasons, it is impossible to remove the last 4% of water by fractional distillation.

Uses of ethanol

1. As a fuel (gasohol) 10 - 20% ethanol 2. Alcoholic beverages 3. Antiseptic use 4. Base chemical for petro-chemical industry 5. Manufacture pharmaceutical drugs

As a solvent: Ethanol is widely used as a solvent. It is relatively safe, and can be used to dissolve many organic compounds which are insoluble in water. It is used, for example, in many perfumes and cosmetics.

Industrial methylated spirits (meths): Ethanol is usually sold as industrial methylated spirits which is ethanol with a small quantity of methanol added and possibly some colour. Methanol is poisonous, and so the industrial methylated spirits is unfit to drink.

The social and economic impact of alcohol production and consumption

The social and economic problems of alcohol use

not only affect those who drink but also those

around them, and society as a whole.

1. In the work environment alcohol can lead to

absences, work accidents, and lower

performance, which, in turn, may lead to

unemployment. This has a cost for the employee,

employer, and the social security system.

2. Drinking can impair how a person performs as a

parent or partner. Drinking can lead a person to

be violent, to spend more time away from home,

to leave other family members destitute, or to

cause them anxiety, fear and depression. Parental

drinking, both during pregnancy and after birth,

can have lasting physical or psychological

effects on children.

3. The economic consequences

of alcohol consumption can be severe,

particularly for the poor. This is not only due to

the amount spent on drinks, but also to lost

wages, and to medical and other expenses.

4. Violence between husbands and wives often occurs

in situations when one or both partners have been

drinking. Heavy drinking has been strongly linked to

violence between partners and to a lesser extent to

violence towards others, possibly because proximity

increases the opportunities for violence. However,

further data is needed to clarify the complex role

of alcohol in such incidents.

5. Alcohol consumption imposes economic and social

costs on society as a whole. Estimating these costs is

often difficult, but it can help improve policies

aiming to reduce harm from alcohol. The few

national estimates that have been made so far

indicate the significant cost of alcohol use to society.

Physiological effects of alcohol consumption

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CHLORINE (a major product of the chlor-alkali industry)

MANUFACTURING CHLORINE USING A DIAPHRAGM CELL

Background chemistry: Chlorine is

manufactured by electrolyzing brine (concentrated sodium chloride solution).

The electrolysis of sodium chloride solution can be used to make three useful substances - chlorine, sodium hydroxide and hydrogen.

The chemistry of the electrolysis process

Sodium chloride solution contains:

sodium ions, chloride ions, hydrogen ions (from the water), hydroxide ions (from the water).

The hydrogen and hydroxide ions come from the equilibrium:

At any one time, the concentration of hydrogen ions or hydroxide ions will be very small - the position of equilibrium lies well to the left-hand side.

At the anode: The negative ions, chloride and hydroxide, get attracted towards the positively charged anode. It is actually easier to liberate hydroxide ions (to give oxygen) than chloride ions (to give chlorine), but there are far, far more chloride ions arriving at the anode than hydroxide ions.

The major reaction at the anode is therefore:

Two chloride ions each give up an electron to the anode, and the atoms produced combine to give chlorine gas.

The chlorine is, however, contaminated with small amounts of oxygen because of a reaction involving hydroxide ions giving up electrons as well.

The chlorine has to be purified to remove this oxygen.

Note: Strictly speaking, this is a simplification. The H+

(aq)ions could be better shown as hydroxonium ions, H3O

+. That would need two water molecules on the left-hand side of the equilibrium. The simplification is fine for this topic. At the cathode: Sodium ions and hydrogen ions (from the water) are attracted to the negative cathode. It is much easier for a hydrogen ion to pick up an electron than for a sodium ion. So this reaction happens:

As the hydrogen ions are converted into hydrogen gas, the water equilibrium tips to the right to replace them.

The net effect of this is that there is a build up of sodium ions and these newly-produced hydroxide ions around the cathode. In other words, sodium hydroxide solution is being formed around the cathode.

The need to keep all the products separate

If chlorine comes into contact with hydrogen, it produces a mixture which will explode violently on exposure to

sunlight or heat. Hydrogen chloride gas would be produced. Obviously, the two gases need to be kept apart.

However, chlorine also reacts with sodium hydroxide solution to produce a mixture of sodium chloride and

sodium chlorate (I) - also known as sodium hypochlorite. This mixture is commonly sold as bleach.

Therefore, if you are trying to manufacture chlorine and sodium hydroxide rather than bleach, you have to keep

the chlorine and sodium hydroxide apart as well.

The diaphragm and membrane cells are designed so that all the products are kept separate.

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The diaphragm cell

Note: This is a simplification of a real cell. For example, in a real diaphragm cell, the electrodes are not a single block of metal. If you are interested, you can find pictures and descriptions of real electrodes by doing a Google search on diaphragm cell and looking for manufacturers' websites.

The diaphragm: The diaphragm is made of a porous mixture of asbestos and polymers. The solution can seep through it from the anode compartment into the cathode side.

Notice that there is a higher level of liquid on the anode side. That makes sure that the flow of liquid is always from left to right - preventing any of the sodium hydroxide solution formed finding its way back to where chlorine is being produced.

Production of the chlorine: Chlorine is produced at the titanium anode according to the equation:

It is contaminated with some oxygen because of the reaction:

The chlorine is purified by liquifying it under pressure. The oxygen stays as a gas when it is compressed at ordinary temperatures.

Production of the hydrogen

The hydrogen is produced at the steel cathode:

Production of the sodium hydroxide: A dilute solution of sodium hydroxide solution is also produced at the cathode (see above for the explanation of what happens at the cathode). It is highly contaminated with unchanged sodium chloride solution.

The sodium hydroxide solution leaving the cell is concentrated by evaporation. During this process, most of the sodium chloride crystallises out as solid salt. The salt can be separated, dissolved in water, and passed through the cell again.

Even after concentration, the sodium hydroxide will still contain a small percentage of sodium chloride.

Industrial importance of the halogens and their compounds

fluorine Used in the making of non-stick coatings for saucepans, aerosol propellants, refrigerants, glass

etching

chlorine Used in the making of bleaches(eg. Sodium hypochlorite NaClO), disinfectants (eg. Chlorine

dioxide), antiseptics (eg. TCP and Dettol), PVC, aerosol propellants (eg. Chlorofluorocarbons),

refrigerants, solvents for dry cleaning and degreasing, insecticides(eg. DDT), anaethestics,

hydrochloric acid, dyes, textiles

bromine Pesticides, flame retardants, photographic chemicals

iodine Antiseptics, photographic film, potassium iodide

Environmental issues within the chlor/alkali industry

There are several environmental concerns that have made a significant impact on the growth of the chlor-alkali

industry over the past twenty years and will dictate the future growth as well. These issues are highly debated,

and the associated "chemophobia" is likely to adversely affect the chlorine consumption profile in the future.

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Chlorine bleaching of wood pulp and dioxin

emissions to the environment

Presence of dioxin, at parts per trillion (ppt) levels, in

paper and paper based products and chlorinated

organics in pulp mill effluents led to decreased

chlorine demand. In the U.S., chlorine consumption in

the pulp and paper industry, decreased from 15% in

1987 to 7% in 1998. The U.S. Environmental

protection agency promulgated "Cluster Rules" in late

1998, mandating the use of elemental chlorine-free

bleaching. These rules, which went into effect in April

2001, lowered the chlorine utilization in the North

American pulp and paper bleaching operations in

favor of sodium chlorate, hydrogen peroxide and

oxygen.

Ozone layer depletion

Because of their contribution to the ozone layer

depletion, production of chlorinated fluorocarbons

(CFC's), carbon tetrachloride (CCl4), and 1,1,1-

trichloroethane was banned in 1997 following the

Montreal Accord.

Polyvinyl chloride plastic

There are two major environmental issues with PVC,

which include their lack of biodegradability and

generation of dioxins when they are incinerated for

energy recovery and for controlled waste recycling.

Hydrochloric acid formation during the thermal

decomposition of PVC is another issue that

environmentalists are strongly invoking for the

substitution of chlorine-free products for PVC.

Mercury emissions

Between 1930 and 1960, several tons of mercury

waste was dumped in Minamata Bay in Japan.

Thousands of people living around the bay developed

methyl mercury poisoning through the consumption of

contaminated fish. The victims suffered from severe

neurological damage, which later became known as

Minamata Disease. Thousands were afflicted and more

than 900 died.

Asbestos

Asbestos is used as a separator material in diaphragm

cells. However, asbestos is a toxic material, causing

lung cancer, asbestosis, and mesothelioma. As a result,

in 2007, a bill was adopted to ban most uses of

asbestos in the United States. Chlor-Alkali plants were

exempt because few cost effective alternatives exist

for this technology.

Practice Question

What is the ratio of moles of NaCl used to moles of Cl2 produced?

Use this ratio to determine mass of NaCl in kg required to produce 2.5 x 1010

kg of Cl2

WATER

The water cycle, also known as the hydrologic cycle or H2O cycle, describes the continuous movement of

water on, above and below the surface of the Earth. Water can change states among liquid, vapour, and ice at

various places in the water cycle.

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Importance of the water cycle

Water is continually being recycled in nature. This recycling:

1. Ensures a constant supply of water is available to plants for photosynthesis.

2. Ensures a constant supply of water is available to all living organisms to keep their cells hydrated and to act as a

solvent.

3. Ensures aquatic organisms have a constant environment in which to live.

4. Purifies water, replenishes the land with freshwater, and transports minerals to different parts of the

globe.

5. Helps to reshape the geological features of the Earth, through such processes as erosion and

sedimentation

6. Through the process of evaporation, takes up energy from the surroundings and cools the environment

7. Through the process of condensation, releases energy to its surroundings, warming the environment.

Methods of Water purification

Water purification is the process of removing undesirable chemicals, materials, and biological contaminants

from contaminated water. The goal is to produce water fit for a specific purpose. Most water is purified for

human consumption (drinking water) but water purification may also be designed for a variety of other

purposes, including meeting the requirements of medical, pharmacology, chemical and industrial applications.

Please note that desalination can also be considered a process of water purification via the use of reverse osmosis

Sedimentation

The water, after coagulation, is left in settling basin further for sufficient period to allow sedimentation of

remaining materials. Sedimentation however considerably reduces microbial population of the water aside

from removing most of the suspended particles.

Flocculation

Water from raw water reservoirs (natural sources) is collected

in large tanks/basins for a sufficient time period to permit large

particulate matter to settle down at the bottom. This material is

removed and then the water is treated with flocculants such

aluminium sulphate which form a floc that precipitates and

carriers with it microorganisms on the surface. Suspended

organic matter settle onto the bottom of the tanks/basins. In this

ways most substances that impart turbidity to water get

coagulated.

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Filtration

After sedimentation, water is subjected to sand filters to remove flocks of living organisms. The process of

filtration is highly critical and important as it can remove protozoan cysts and also about 98-99% of bacteria

from water. The water may also be filtered through activated charcoal to remove potentially toxic organic

compounds and organic compounds that impart undesirable colour and/or taste to the water.

Disinfection

Disinfection is the final step is municipal water purification and it ensures that no pathogenic microorganisms

are carried through water. For water supplies of small towns and localities sodium or calcium hypochlorite

(NaOCl or CaOCl2 respectively) may be used to disinfect water, but for larger cities, however, chloroamine (as

opposed to chlorine) is now the method for disinfection.

Importance of Dissolved Oxygen

All aquatic life depend on the amount of dissolved oxygen (DO) present. This allows all aquatic life to conduct

their metabolic processes essential to life. High levels of DO (above 90%) indicate “healthy” water bodies. DO

can also be related indirectly to biological oxygen demand (BOD), the higher the DO, the lower the BOD.

Once DO levels begin to drop, this usually indicates some form of pollution is present in the water body.

Sources of water pollution

Pollutant Source Effect on environment

Nitrates Manmade fertilisers Drinking water that gets contaminated with nitrates can prove fatal especially to infants that drink formula milk as it restricts the amount of oxygen that reaches the brain causing the ‘blue baby’ syndrome as well as eutrophication.

Phosphates Manmade fertilisers and detergents Eutrophication

Heavy metals (e.g. lead and mercury)

Use of lead pipes causes dissolved lead ions to form in the water, improper disposal of mercury from industrial processes

Lead affects the nervous system and can ultimately lead to death. Mercury stunts physical development of organisms

Cyanides Improper disposal after used in making fabrics

Acts as a poison

Trace metals mining waste and tailings, landfills, or hazardous waste dumps.

Hazardous effects on nervous systems and physical development

Pesticides and herbicides Run off from backyards, farms and golf courses

Accumulate up the food chain and cause impairment of physical development of aquatic life

Petroleum residues From underground storage tanks Similar to pesticides

Suspended particles Industrial processes e.g. cement manufacture

Respiratory problems, covers wide area in fine dust

Tests for pollutants in water

Nitrate NO3– Add NaOH(aq) Add Devarda’s alloy (powdered Zn, Al) Heat & hold moist red litmus at

mouth of test tube

NH3 evolved, litmus paper red blue

Find out about the tests for phosphates, cyanide and lead in water

Practice Questions

1.

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2.

THE ATMOSPHERE

Ozone: The atmosphere surrounding the Earth

contains a small amount of ozone (O3), a gas with

molecules consisting of three oxygen atoms bound

together, instead of the two which form the normal

oxygen molecule (O2) that makes up 21% of the air

we breathe.

The average concentration of ozone in the

atmosphere is about 300 parts per billion by

volume (ppbv) that is, there are about 3 molecules

of ozone for every ten million air molecules. Most

of it (~90%) is contained in the stratosphere about

15 - 30 km above the Earth's surface where it is

present at levels of several parts per million by

volume (ppmv). If all the ozone in the atmosphere

were compressed to atmospheric pressure, it would

form a band ~3 mm thick. Even though it is present

in such small quantities, it plays a vital role in

supporting life on Earth. The natural ozone levels

in the atmosphere allow most harmful solar

radiation to be absorbed before it can reach the

Earth's surface; ozone absorbs a significant portion

of the ultraviolet light known as the UV-B, which

has been linked to various types of skin cancer,

cataracts and damage to the human immune

How the concentration of ozone in the atmosphere is maintained?

When an oxygen molecule receive a photon (h v), it

dissociates into monoatomic (reactive) atoms - a

process called photodissociation. These atoms attack

an oxygen molecule to form ozone, O3.

O2 + h v O + O

O2 + O O3

The last reaction requires a third molecule to take

away the energy associated with the free radical O

and O2, and the reaction can be represented by

O2 + O + M O3 + M*

The over all reaction between oxygen and ozone

formation is:

3 O2 2 O3

The absorption of UV B and C leads to

the destruction of ozone

O3 + h v O + O2

O3 + O 2 O2

A dynamic equilibrium is established in these

reactions. The ozone concentration varies due to

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system; UV-B is also known to be harmful to some

crops and some forms of marine life. Any changes

in the amount of radiation that penetrates to the

Earth's surface as a result of the thinning of the

ozone layer can have potentially serious

implications for human health and ecological

systems, and also for global climate.

the amount of radiation received from the sun.

How do CFCs help depleting ozone?

A relatively recent concern is the depletion of ozone,

O3 due to the presence of chlorine in the troposphere,

and eventually their migration to the stratosphere. A

major source of chlorine is Freons: CFCl3 (Freon 11),

CF2Cl2 (Freon 12), C2F3Cl3 (Freon 113),

C2F4Cl2 (Freon 114). Freons decompose in the

troposphere. For example,

CFCl3 CFCl2 + Cl

CF2Cl3 CF2Cl + Cl.

The chlorine atoms catalyze the decomposition of

ozone,

Cl + O3 ClO + O2

andClO molecules further react with O generated due

to photochemical decomposition of ozone:

O3 + h v O + O2,

ClO + O Cl + O2

O + O3 O2 + O2.

The net result or reaction is

2 O3 3 O2 Thus, the use of CFCs is now a world wide concern.

In 1987, one hundred and forty nine (149) nations

signed the Montreal Protocol. They agreed to reduce

the manufacturing of CFCs by half in 1998. They also

agree to phase out CFCs.

What are CFCs?

Chemist Roy J. Plunkett discovered

tetrafluoroethylene resin while researching

refrigerants at DuPont. Known by its trade name,

Teflon, Plunkett's discovery was found to be

extremely heat-tolerant and stick-resistant. After

ten years of research, Teflon was introduced in

1949. His continued research led to the usage of

chlorofluorohydrocarbons known as CFCs

or freon as refrigerants.

CFCs are made up of carbon, hydrogen, fluorine,

and chlorine.

The nontoxic and nonflammable CFCs have been

widely used as refrigerants, in aerosol spray, and

dry cleaning liquid, foam blowing agents, cleansers

for electronic components in the 70s, 80s and early

90s.

In 1973, James Lovelock demonstrated that all the

CFCs produced up to that time have not been

destroyed, but spread globally throughout the

troposphere.

Effects of ozone on human life

When enough ozone molecules are present, it forms a

pale blue gas. It is an unstable molecule that readily

combines with other atoms. Ozone has the same

chemical structure whether it is found in

thestratosphere or the troposphere. Where we find

ozone in the atmosphere determines whether we

consider it to be Dr. Jekyll or Mr. Hyde.

In the troposphere, the ground-level or "bad"

ozone is an air pollutant that damages human

health, vegetation, and many common materials. It

is a key ingredient of urban smog. In the

stratosphere, we find the "good" ozone that protects

life on earth from the harmful effects of the sun's

ultraviolet rays.

Ozone may be the most harmful air pollutant.

1. It readily attacks organic materials with

C=C bonds, for example in the lungs.

2. Ozone produces harmful irritation in the

respiratory system. It is believed that,

because ozone damages lung tissue, it leads

to a decreased resistance to infectious

disease.

3. One abiological effect of ozone is to attack

rubber (e.g., rubber tires). This effect is

noticeable in the cracking of the sidewalls

of tires. Tires of garaged vehicles last

longer.

Ozone in the Stratosphere

Ozone and oxygen molecules in the stratosphere

absorb ultraviolet light from the sun, providing a

shield that prevents this radiation from passing to the

earth's surface. While both oxygen and ozone together

absorb 95 to 99.9% of the sun's ultraviolet radiation,

only ozone effectively absorbs the most energetic

ultraviolet light, known as UV-C and UV-B, which

causes biological damage. The protective role of the

ozone layer in the upper atmosphere is so vital that

scientists believe life on land probably would not

have evolved - and could not exist today - without it.

Ozone in the Troposphere

The other 10% of the ozone in the earth's

atmosphere is found in the troposphere, which is

the portion of the atmosphere from the earth's

surface to about 12 km or 7 miles up. In the

troposphere, ozone is not wanted. Ozone is even

more scarce in the troposphere than the

stratosphere with concentrations of about 0.02 to

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0.3 parts per million. But even in such small doses,

this molecule can do a lot of damage.

And just to confuse things even further, ozone in

the troposphere is one of the greenhouse gases. As

discussed in the Greenhouse Effect section, the

naturally occurring greenhouse gases (including

ozone) are what make earth habitable for life as we

know it. But scientists are very concerned about the

warming effects of increased greenhouse gases

caused by human activity. So, in the troposphere,

accelerated ozone levels deal us a double whammy

- as a key ingredient in smog and as a powerful

greenhouse gas.

About 90% of the ozone in the earth's atmosphere lies

in the region called the stratosphere between 16 and

48 kilometers (10 and 30 miles) above the earth's

surface. Ozone forms a kind of layer in the

stratosphere, where it is more concentrated than

anywhere else, but even there it is relatively scarce.

Its concentrations in the ozone layer are typically only

1 to 10 parts of ozone per 1 million parts of air,

compared with about 210,000 parts of oxygen per 1

million parts of air.

Maintaining the Balance of Carbon Dioxide Concentration in the Atmosphere

The carbon cycle

Life is built on the conversion of carbon dioxide into the carbon-based organic compounds of living organisms.

The carbon cycle illustrates the central importance of carbon in the biosphere. Different paths of the carbon

cycle recycle the element at varying rates. The slowest part of the cycle involves carbon that resides in

sedimentary rocks, where most of the Earth's carbon is stored. When in contact with water that is acidic (pH is

low), carbon will dissolve from bedrock; under neutral conditions, carbon will precipitate out as sediment such

as calcium carbonate (limestone). This cycling between solution and precipitation is the background against

which more rapid parts of the cycle occur.

Short-term cycling of carbon occurs in the continual physical exchange of carbon dioxide (CO2) between the

atmosphere and hydrosphere. Carbon dioxide from the atmosphere becomes dissolved in water (H2O), with

which it reacts to form carbonic acid (H2CO3), which dissociates into hydrogen ions (H+) and bicarbonate ions

(HCO3-), which further dissociate into hydrogen and carbonate ions (CO3

2-). The more alkaline the water (pH

above 7.0 is alkaline), the more carbon is present in the form of carbonate, as is shown in the following

reversible reactions:

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Here is the exact flow of events, as carbon flows from one layer to another as shown in the diagram above.

1. In the process of photosynthesis, atmospheric carbon is absorbed by plants.

2. This carbon is transferred form plants to the animals feeding on them, and further moves up the food

chain.

3. Respiration, digestion and metabolism plants and animals result in some transfer of carbon back to the

atmosphere.

4. Some carbon also moves to the lithosphere when these living organisms die or when wood and leaves

decay or when animals excrete. Some of these living beings buried millions of years ago have been

converted to fossil fuels.

5. Mining and burning of fossil fuels cause this carbon to move from the lithosphere to the atmosphere.

6. Some of this atmospheric carbon gets dissolved in the oceans and thus completes the cycle.

Question: Explain the importance of maintaining the balance of carbon dioxide concentration in the atmosphere

THE GREENHOUSE EFFECT: The burning of

oil and other fossil fuels is contributing to the

'Greenhouse Effect' or global warming. The

Earth's land-water surfaces absorbs the Sun's

radiation in the form of infra-red (main heating

effect) and visible/ultraviolet sunlight. Carbon

dioxide and other gases including methane,

water vapour and CFC's absorb the re-radiated

lower frequency infrared energy from the Earth's

surface and so warming the atmosphere, rather

like a greenhouse allows the sunlight in but not

out. The effects are predicted to be dramatic e.g.

rising sea levels as polar ice melts causing

flooding in low lying land, more energy in the

global weather system leads to more frequent

violent weather patterns etc.

Effects of the Products of Combustion of Hydrocarbon-Based Fuels

When fossil fuels burn efficiently in

an excess of air/oxygen the only products

are carbon dioxide and water e.g.

o methane + oxygen ==> water +

carbon dioxide

o CH4(g) + 2O2(g) ==> CO2(g) + 2H2O(l)

If there is not enough oxygen present to

completely burn the fuel to carbon dioxide

and water other products may form causing

pollution and fuel inefficiency.

o This is referred to as incomplete

combustion.

The most common partially burned products

are likely to be carbon C (soot) and

deadly carbon monoxide CO.

Carbon-soot, a fine black powder-dust is

potentially harmful and readily formed in

fires i.e. its classically produced by smoky

yellow flames. The soot, like any fine solid

'dust' is harmful when absorbed on the

sensitive tissue of the linings of the nose,

throat and lungs. Soot deposits cause

coughing and sore throat and are ejected from

your body through sneezing, coughing, and

nose blowing. Coarse particles (10 microns)

are inhaled into your windpipe and settle

there, causing irritation and more

coughing. Soot is also a 'carrier' of

polycyclic aromatic hydrocarbons (PAH's) on

it which are carcinogenic.

Even very low concentrations of carbon

monoxide can be fatal. Why? Oxygen is

carried around the body by a complicated

protein molecule in red blood cells called

haemoglobin. The bonding between oxygen

and haemoglobin is quite weak to allow easy

oxygen transfer for cell respiration.

Unfortunately, the bonding between carbon

monoxide and haemoglobin is stronger, so

oxygen is replaced by carbon monoxide and

blocks normal cell respiration. The

consequences are reduced blood oxygen

concentration leading to unconsciousness and

GLOBAL WARMING is the increase in

the average temperature of Earth's near-surface air

and oceans since the mid-20th century and its

projected continuation.

PHOTOCHEMICAL SMOG: air pollution

produced by the action of light on oxygen, nitrogen

oxides, and unburned fuel from automobile exhaust

to form ozone and other pollutants.

The reduction of fossil fuel burning is the only way

to reduce photochemical smog e.g.

using photovoltaic cells to harness solar energy to

produce electricity. Using solar power indirectly in

this way to run electric cars is potentially a good

partial solution to the problem

The equations for incomplete combustion

below show the formation of carbon-soot

and 'deadly' carbon monoxide when there is

a lack of oxygen for complete combustion.

As mentioned already, soot is obviously a

'dirty' pollutant coating any surface

(including your lungs!) that the soot particles

settle on and they contain unburned

carcinogenic hydrocarbons AND carbon

monoxide is involved in the chemistry of

photochemical smogs - so all in all,

inefficient combustion of fossil-hydrocarbon

fuels is very undesirable!

Carbon monoxide is unfortunately emitted

by all car exhausts, though catalytic

converters help reduce this by converting

nitrogen monoxide (another pollutant) and

carbon monoxide into harmless nitrogen and

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carbon dioxide.

eventually death!

Effects of urban smog - NOX

o NO2 has a brown color; it makes our smoggy

skies brownish-yellow. Nitrogen dioxide is a

lung and eye irritant, and, along with nitrogen

monoxide, it is involved in the complex

chemistry of photochemical smogs which can

also produce ozone and other harmful

chemicals in the air.NOX compounds can lead

to chronic lung damage.They can exacerbate

asthma. They increase the susceptibility of

the very young and the very old to respiratory

infections.

NOX contributes to the nitrification (over-

fertilization) of bays and wetlands, leading to

algal blooms, and can lead to fish kills.

2NO(g) + 2CO(g) ==> N2(g) + 2CO2(g)

Transition metals like platinum and

rhodium are used in the catalytic

converter. Nitrogen monoxide, NO, is formed by the

combination of nitrogen and oxygen at high

temperature in automobile engines (cars,

lorries, buses etc. - its all the same!)

N2(g) + O2(g) ==> 2NO(g)

Nitrogen monoxide readily forms nitrogen

dioxide by combining with oxygen in air on

exit from the engine exhaust.

2NO(g) + O2(g) ==> 2NO2(g)

How the atmospheric concentrations of the oxides of nitrogen may be altered

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This

transformation can be carried out via both biological and non-biological processes. Important processes in the

nitrogen cycle include nitrogen fixation, nitrogen assimilation, ammonification, nitrification, and

denitrification.

The majority of Earth's atmosphere (approximately 78%) is nitrogen,[1]

making it the largest pool of nitrogen.

However, atmospheric nitrogen is unavailable for biological use, leading to a scarcity of usable nitrogen in

many types of ecosystems. Human activities such as fossil fuel combustion, use of artificial nitrogen fertilizers,

and release of nitrogen in wastewater have dramatically altered the global nitrogen cycle.

The atmospheric concentrations of the oxides of nitrogen may be altered via the following processes:

o Nitrogen monoxide, NO, is formed by the combination of nitrogen and oxygen at high

temperature in automobile engines (cars, lorries, buses etc. - its all the same!)

N2(g) + O2(g) ==> 2NO(g)

o Nitrogen monoxide readily forms nitrogen dioxide by combining with oxygen in air on exit

from the engine exhaust.

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2NO(g) + O2(g) ==> 2NO2(g)

o Nitrogen oxides dissolve in rainwater to form an acidic solution of nitric acid which contributes

to acid rain. o The conversion of nitrogen oxides to non-toxic products in the catalytic convertors of cars.

2NO(g) + 2CO(g) ==> N2(g) + 2CO2(g)

Methods of control/prevention of atmospheric pollution

The fact is that human activities contribute the most to air pollution. Considering the harmful effects of air

pollution, now it is very essential that everyone should contribute a bit to prevent air pollution. There are certain

ways that one can help to reduce the emission of air pollutants in the atmosphere. Following are some tips for

preventing air pollution:

Car Pool: Forming and implementing a car pool will reduce the number of cars, thereby, preventing air

pollution by cutting down the use of fossil fuels. This way, it will help in the sustainable use of fossil fuel and

its conservation for the future generations.

Vehicle Care: Timely servicing of the car helps to keep it in a good condition and also minimizes fuel exhaust.

Driving the car at an average speed and turning off in traffic is a key to saving fuel. Make sure to use unleaded

petrol and opt for regular pollution checking of your car.

Public Transport: Whenever possible, try to travel by public transports. This helps in two ways; prevents air

pollution and increases public income. If you are going to a nearby place, go by walking or use bicycle, instead

of using your vehicle. The objective is to minimize the use of fuels, as far as possible.

Alternative Energy Source: Another effective way to prevent air pollution is to use alternative energy

sources such as solar energy, hydroelectric energy and wind energy. Nowadays, sophisticated technologies such

as wind turbine, solar water heaters are introduced to generate electricity and other energy forms for the

household use.

Saving Energy: Saving energy will, of course, help to prevent air pollution. Switch off the lights, fans, air

conditioners, televisions, and other appliances, when not in use. You can also share a room with others when the

air conditioner or fan is on, instead of switching them on in every room.

Minimize Air Pollutants: Always try to minimize smoke emission, as it can contribute to air pollution. One

way is to compost dried leaves and kitchen waste, instead of burning them. Composting will also give you

organic fertilizer for your garden. While buying the products, always choose air-friendly and recyclable

products that will minimize the emission of pollutants.

Social awareness about air pollution is the most essential step to be taken for the prevention of air pollution.

Awareness programs and/or advertisements should be encouraged, so that people understand the potential

health hazards of air pollution. Improvement of transport facilities and proper use of land for the sake of social

benefits are equally important for controlling air pollution.

Air Pollution Control Equipment

Here are a few air pollution control systems that are being used by vehicles and industries. They help to either

remove pollutants from a stream of exhaust before they are emitted into the air or destroy them.

Air Pollution Control Systems To Reduce Particulate Matter

Wet Scrubbers: These include a number of devices that remove pollutants from furnace flue gas as well as

other gas streams. The pollutants are removed by the polluted gas stream being forced through a scrubbing

liquid or by using some other method of bringing it into contact with the liquid. Wet scrubbers are used in a

number of industries like large power plants, asphalt plants, steel plants, fertilizer plants, and acid plants.

Electrostatic Precipitator (ESP): Also known as Electrostatic Air Cleaners, this air pollution control system is

a particulate collecting device which uses the force created by an induced electrostatic charge to remove

particulate matter from any flowing gas, e.g. air. These filtration devices are highly efficient and are very

effective in removing fine particles like smoke and dust from the air stream. ESPs are used for controlling

particulate emissions in various industries like oil refineries, pulp mills, and oil and coal fired utilities that

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generate electricity which produce smoke.

Dust Cyclones: These are used to remove particulate matter from a gas or air stream, without using filters,

using vortex separation instead. Mixtures of fluids and solids are separated by using gravity and rotational

effects. There is large scale use of cyclones in oil refineries as well as the cement industry wherein they form a

part of the kiln preheaters.

Air Pollution Control Systems To Reduce NOx (Nitrogen Dioxide and Nitrogen Oxide)

Exhaust Gas Recirculation (EGR): This is a technique used for reducing NOx that is used in most diesel and

gasoline engines. A part of the exhaust of an engine is recirculated back into its cylinders. When the incoming

air is intermixed with the recirculated exhaust gas, it results in diluting the mixture with inert gas, reducing the

adiabatic flame temperature and also lowering the excessive oxygen in diesel engines. The peak combustion

temperature is also lowered because the specific heat capacity of the mix is increased by the exhaust gas. Since

high temperatures cause Nox to form much faster, EGR helps in limiting NOx from being generated. Nox is

produced when a mixture of oxygen and nitrogen is subjected to high temperatures.

Catalytic Converter: This is a device that is used to diminish the toxicity of emissions that are produced by

internal combustion engines. First introduced in 1975 in the US in order to comply with the tightening

regulations by the Environmental Protection Agency, catalytic converters are still used most commonly in the

exhaust systems of motor vehicles. Some of the other places they are use in are: trains, mining equipment,

forklifts, generator sets, and other machines equipped with engines.

Air Pollution Control Systems To Decrease Volatile Organic Compounds (VOC):

Gas Flare: Also called a flare stack, this is a chimney that is erected on oil rigs or oil wells, as well as landfills,

chemical plants, and refineries. When flammable gas or unusable waste gas plus liquids are discharged by

pressure relief valves, this device is used to burn them off. This device is also used in landfills to burn and/or

vent the waste gas that is produced by the decomposing materials.

Biofilters: This is a technique for pollution control which uses living matter to trap and biologically degrade

pollutants. In air pollution control, the pollutants in the air are subjected to microbiotic oxidation. In other

words, when it is applied in the filtration and purification of air, microorganisms, such as fungi and bacteria that

are embedded in a biofilm, are used to degrade the air pollutant.

Solid Waste What is Solid Waste?

Solid waste is defined as any garbage, refuse, sludge

from waste treatment plant, water supply treatment

plant, or air pollution control facility and other

materials, including solid, liquid, semisolid, contained

gaseous resulting from industrials, commercials,

mining and agricultural operations from community

activities.

Characteristics of wastes

• Corrosive: these are wastes that include acids or

bases that are capable of corroding mental

containers, e.g. tanks

• Ignitability: this is waste that can create fires

under certain condition, e.g. waste oils and

solvents

• Reactive: these are unstable in nature; they cause

explosions, toxic fumes when heated.

• Toxicity: waste which are harmful or fatal when

ingested or absorb

Types of waste

• Non Hazardous waste: refuse, garbage, sludge,

municipal trash.

• Hazardous waste: solvents acid, heavy metals,

pesticides, and chemical sludges

• Radioactive: high and low-level radioactive waste

• Mixed waste: Radioactive organic liquids,

radioactive heavy metals. Waste treatment Waste disposal

• Incineration:

• Solidification: solid waste are melted or evaporated

• Landfills: waste is placed into or onto the land

in disposal facilities.

• Underground injection wells: waste are

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to produce a sand like residue.

• Heat treatment: Heat applied at moderate

temperature, is used in treating volatile solvents.

• Chemical treatment: is the application of chemical

treatment in the treatment of corrosive solid.

injected under pressure into a steel and

concrete-encased shafts placed deep in the

earth.

• Waste piles: is accumulations of insoluble

solid, non flowing hazard waste. Piles serves

as temporary or final disposal.)

• land treatment: is a process in which solid

waste, such as sludge from wastes is applied

onto or incorporated into the soil surface.

• Waste are disposed in flowing rivers in less

developed countries.

Impacts of solid waste on Terrestrial environment

Effects of Solid Waste on Animals and Aquatics life

• Chemical poisoning through chemical inhalation

• Uncollected waste can obstruct the storm water runoff

resulting in flood

• Low birth weight

• Cancer

• Congenital malformations

• Neurological disease

• Nausea and vomiting

• Increase in hospitalization of diabetic residents living

near hazard waste sites.

• Mercury toxicity from eating fish with high levels of

mercury

• Increase in mercury level in fish due to

disposal of mercury in the rivers.

• Plastic found in oceans ingested by birds

• Resulted in high algal population in rivers and

sea.

• Degrades water and soil quality

Impacts of solid waste on Environment

• Waste breaks down in landfills to form

methane, a potent greenhouse gas

• Change in climate and destruction of ozone

layer due to waste biodegradable

• Littering, due to waste pollutions, illegal

dumping, Leaching: is a process by which

solid waste enter soil and ground water and

contaminating them.

What is Solid Waste Management? Process involved in waste reduction

Solid Waste Management is the process of reducing, re-

using and recycling waste products.

• Proper management of solid waste

• Involving public in plans for waste treatment

and disposal

• Provide the public accurate, useful information

about the whole projects, including the risks

and maintain formal communication with

public

• Educate people on different ways of handling

waste.

• Waste Minimization is a process of reducing

waste produce by individuals, communities

and companies, which reduces the impact of

chemical wastes on the environment to the

greatest extent.

• Household level of proper segregation of

waste, recycling and reuse.

• Process and product substitution e.g. use paper

bag instead of plastic bags.

It requires a change in our habits but does not necessarily

mean a return to a more difficult lifestyle. Good solid

waste management improves our standard of living. In

fact if we do not reduce waste, the economic and social

cost of waste disposal will continue to increase and

communities large and small will face increasingly harder

decisions about managing their trash.

Precycling & Recycling

Precycling is making purchasing decisions that will

reduce waste. Recycling on the other hand is the process

of producing goods from waste products or where

possible, finding other uses for them.

We need to start re-using

Paper

Glass Bottles

Aluminum Wrapping

Organic Waste such as spoilt or unwanted portions of food

items, for example, banana skins

Plastics

Helpful Tips on Managing Solid Waste in the Home

1. Use sheets of used writing paper to make a

message pad

2. Choose cloth diapers over disposable ones