CHAPTER 1

INTRODUCTION

Dyes and coloring materials are being used by almost every industry

producing household goods, textile, food, paints, pulp and paper, printing etc. The

release of toxic and hazardous dyes from these industries has created a global concern

due to their immense toxicity toward mankind. Many dyes and pigments are toxic and

have carcinogenic and mutagenic effects that affect aquatic biota and also humans

[Geo et al., 2010]. Color impedes light penetration, retards photosynthetic activity

and also has a tendency to chelate metal ions which result in micro-toxicity to fish and

other organisms. The toxic and hazardous intermediates/substances created by these

dyes after undergoing oxidation and reduction in water further increase the need for

their removal from wastewater. Thus, industrial dye effluents are an increasingly

major concern and need to be effectively treated before being discharged into the

environment in order to prevent these potential hazards.

Dyes and dye intermediates industry is an important sector of the Indian

chemical industry. This sector has grown at a very fast pace after independence and

nearly half of its production is being exported today. India is now the second largest

producer of dyes and intermediaries in Asia. A remarkable feature of the Indian

dyestuff industry is the co-existence of units in the small, medium and large sectors,

actively involved in the manufacture of dyestuffs and their intermediates. The

industry is characterized by the co-existence of a small number of players in the

organized sector (around 50 units) and a large number of small manufacturers (around

1

1,000 units) in the unorganized sector. The distribution of these units is skewed

towards with western region (Maharashtra and Gujarat) accounting about 90%. In

fact, nearly 80% of the total capacity is in Gujarat, where there are nearly 750 units.

[http://myiris.com/shares/sectors/sectorReport.php?secode+dyestuff&peercode=AII&

fname=./data/dyestuff/dyestuff.htm].

Over seven hundred types of dyes and organic pigments are now being

manufactured in the country (both by the organized and the unorganized sector). In

India, only one third of the dyestuff producing industries are in organized sector. The

rest come from the unregulated small-scale sector, which produces more than half of

India's aggregate volume. The domestic textile industry, which consumes up to 80 per

cent of the dyestuffs produced, looks for manageable costs rather than consistent

quality. So the bulk of its demand for dyes is met by the small- scale sector.

The small-scale sector's substantially lower investment in pollution control

measures also makes it more economical. With its need for dyeing and printing, the

textile sector is probably the worst offender when it comes to release colored effluent

discharge. Ludhiana, Panipat, Pali, Bichchri, Patancheru, Jetpur, Ahmadabad, Surat

and Tirupur are some of the country's most polluted zones. Dyes are soluble and

essentially used in paints, inks, textiles and polymers etc. India is a major exporter of

dyes, mostly due to ban on production of some of the dyes and intermediates in the

developed countries due to pollution. The Indian companies together accounts for

around 6.6 % of the world‘s production. India produces 64,000 tonnes of dyes, 2 per

cent of which (7,040 tonnes) are directly discharged into the environment.

[http://www.centralchronicle.com/20050228/2802303.htm].

2

Within India, the major players in the pigments industry are Color Chem and

Sudarshan Chemicals while in the dyestuff industry companies such as Atul, Clariant

India, Dystar, Ciba Specialities and IDI are important players in terms of market

share.

Colored paper is obtained by dyeing the paper stock or the paper surface.

Additionally, fixing agents and other additives are used to improve dye fixation and to

obtain better dyeing results. In the process, it also discharges colored pulping effluent

in water. Color in the wastewater is mainly due to dyes. A wide variety of colored

paper is made using various types of dyes. In the years 1998 and 2001, the sector

discharged more than 100 tonnes of unused dyes. Dyeing operations are water-

intensive. Cellulose dyeing uses massive amounts of salt, whose presence in effluent

leads to very high amount of total dissolved solids in the effluent water. Dyes and

color pigments also contain metals such as copper, nickel, chromium, mercury and

cobalt which are difficult to remove from wastewater. Moreover, the unused dyes and

color released in effluent from dyeing vats interfere with the transmission of light in

the water body that receives the effluent.

Textile dyes, printing inks, pigments, acids, paints and colors are used in

plastics like food colors. The color is introduced into objects to improve aesthetic

value. The desired effect is achieved by incorporating into a substance - say a cloth, a

lipstick or an ink. The manner, in which colorants impart color to an object, makes

their effluent an environmental or health problem.

Sanganer town, district Jaipur (Rajasthan, India), is famous worldwide for its

dyeing and printing industries. There are about 400 industries involved in textile

printing processes, which discharge effluents into nearby ponds and drains, 3

withoutany treatment. These effluents contain highly toxic dyes, bleaching agents,

salts, acids, and alkalis. Heavy metals like cadmium, copper, zinc, chromium and iron

are also found in the dye effluents. Textile workers are exposed to such waters with

no control over the length and frequency of exposure. Further, as the untreated

effluents are discharged into the environment they can cause severe contamination of

surface and underground water. Environmental pollution caused by such textile

effluents results in adverse effects on flora, fauna and the general health of not only

the textile workers, but also the residents of Sanganer town [Nupur et al., 2005].

Cotton textile industry wastewater generated by the different production steps

(i.e. sizing of fibers, scouring, desizing, bleaching, washing, mercerization, dyeing

and finishing) has high pH and temperature. It also contains high concentrations of

organic matter, non-biodegradable matter, toxic substances, detergents, soaps, oil,

grease, sulfide, alkalinity, and suspended and dissolved solids. Because of the low

biodegradability of many textile chemicals and dyes, biological treatment is not

always effective for textile industry wastewater.

1.1 CONSUMPTION PATTERN OF DYES

Dyestuff is a broad term which includes dyes and pigments. A dye is a colored

substance or an organic compound, which when applied in a solution to a fabric,

imparts a color resistant to washing. They are largely used by the textiles, paper and

leather industry, with textiles accounting for over 80% in India. This links the

dyestuff industry's fortunes to that of the textile industry. Dyes are classified

according to various systems. The detailed description of dyes is given in section 1.2.

There are different types of dyes and their applications mentioned in Table1.1. The

different types of dyes used in paper industry are given in Table 1.2. 4

Table 1.1 Classification of dyes and their applications

Group Application

Acid Wool, silk, paper, synthetic fibers, leather

Azoic Printing Inks and Pigments

Basic Silk, wool, cotton

Direct Cotton, cellulosic and blended fibers

Disperse dyes Synthetic fibers

Reactive Cellulosic fiber and fabric

Mineral and pigments dyes Cotton, cellulosic, blended fabric, paper

Sulphur Cotton, cellulosic fiber

Vat dyes Cotton, cellulosic and blended fiber

Table 1.2 Dyes used in paper industry

Sr.

No. Dyes Quality of Paper

Consumption in

colored paper board,

kg per tonne of paper

1 Methylene

Blue

File board, maplitho 2.5 - 3.5

2 Brilliant Green Cover paper 0.8 - 1.0

3 Methyl Violet Violet poster, maplitho paper,

cream wove, colored wove

8.0 - 9.0

4 Scarlet Red File board 0.6 - 1.0

5 Acid Orange Buff board, buff manila board 5.0 - 6.0

6 Malachite

Green

File board, colored 1.0 - 2.0

7 Metanil Yellow File board, colored poster 2.5 - 4.5

8 Sunfast Yellow File board, colored poster, buff

manila board

4.0 - 5.0

9 Auramine File board 0.5 - 1.0

10 Rhodamine File board, pink colored poster,

maplitho, duplex board, cover

paper

1.5 - 2.0

Source: [Freeman, 1995]

5

1.2 DIFFERENT TYPES OF DYES

(a) Acid dyes

Acid dyes are all water-soluble salts (usually sodium or potassium salts) of

colored aromatic organic acids, which dissociate in water to form colored anions.

Acid dyes are highly water soluble. These dyes are neutral or slightly alkaline water

solution, fair to good light fastness and low affinity for wood fibers.

[http://www.dyespigments.net/types-of-dyes.html].

The family of acid dyes is very vast and diverse, varying widely in their

methods of dyeing, application and end use of the dyed fabric. A choice of dyes

should be made considering sometimes-incompatible factors such as level dyeing,

fastness, brightness and ease of application. Care must be taken to use the appropriate

method as prescribed for a given dye. A number of acid dyes are also used to dye

nylon.

(b) Azoic dyes

The word 'Azoic' is the distinguishing name given to insoluble azo dyes that

are not applied directly as dyes, but are actually produced within the fiber itself. This

is done with impregnating the fiber with one component of the dye, followed by

treatment in another component, thus forming the dye within the fiber. The formation

of this insoluble dye within the fabric makes it very easy to washing.

(c) Basic and modified basic dyes

MAUVENE, the first to be discovered by Perkin, was a basic dye and most of

the dyes which followed, including magenta, malachite green and crystal violet, were

6

of the same type. Basic dyes are cationic, which means that the colored part has

a positive charge, when they are dissolved in water. They will bond to either carboxyl

or sulfonic acid groups on a fiber, via the formation of salt links with these anionic

groups in the fiber [www.scribd.com/doc/29028809/different-types-of-dyes]. Basic

dyes include the most brilliant of all the synthetic dyes known, but unfortunately they

have dull color and are difficult to wash. Basic dyes will dye wool and silk from an

acid bath and are used where brightness is of prime consideration. Basic dyes are used

extensively for dyeing cut flowers, dried flowers, also dyeing jute sisal, raffia, coir

and wood (toys). With the introduction of acrylic fiber a new range of 'modified' basic

dyes were perfected for dyeing of this material.

(d) Direct dyes

These are soluble in water and have direct affinity for all cellulose fibers.

Some will also dye silk and wool. By continuous research this group of dyes has been

supplemented with dyes of good fastness to light and washing. As these dyes, when

dyed without additives, do not exhaust well, an addition of salt is required to improve

the yield of the dye and obtain deeper shades. Generally, the wash fastness of these

dyes is inferior but there are a number of after treatments available to improve the

wash fastness of the dyeing. Most direct dyes can be stripped of the use of stripping

salts (Sodium Hydrosulphite) without harmful effects on the fibers.

(e) Disperse dyes

The introduction of a new regenerated cellulose acetate fiber in 1920 led to the

development of an entirely new range of dyes. It was found that cellulose acetate (or

Celanese) fiber had hardly any affinity for water-soluble dyes. These are substantially

7

water-insoluble non ionic dyes for application to hydrophobic fibers from aqueous

dispersion. They are used predominantly on polyster and to a lesser extent on nylon,

cellulose, cellulose acetate and acrylic fibers.

[www.scribd.com/doc/29028809/different-types-of-dyes].

(f) Reactive dyes

This is an entirely a different class of dye introduced to the market in 1956.

They react chemically with the fiber being dyed and if correctly applied, cannot be

removed by washing or boiling. The main feature of the dyestuff is its low affinity to

cellulose; therefore large amount of salt is required to force its deposition on the

fabric [www.textileschool.com/School/TextileFinishing/TypesofDyes.aspx].

(g) Mineral and pigment dyes

Although it is preferred to use water soluble dyes in textile dyeing for two

reasons; ease of application and greater softness of the fabric. Mineral khaki is used in

cotton army equipment because of its cheapness and because it also renders fabric

resistant to rotting and attack by insects in damp conditions. The introduction of heat

setting synthetic resin has opened new fields in textile printing. Mineral and organic

pigments, as used in paint manufacture, can now be applied to any fabric and rendered

wash fast after heat treatment.

(h) Sulphur dyes

The first Sulphur dye was discovered in France in 1873, and further work done

by Raymond Videl enabled the manufacture of 'Videl black". Its outstanding fastness

to light, washing and boiling far surpassed any cotton black known at that time. The

8

general disadvantage of the sulphur dyes that they produce dull shades and lack a red.

The main advantage lays in their cheapness, ease of application and good wash-

fastness. In their normal state sulphur dyes are insoluble in water but are readily

soluble in the solution of sodium sulphide. Sulphur dyes are organic compounds

containing sulfur or sodium sulfide. In this form they have high affinity to the all

cellulose fibers [www.textileschool.com/School/TextileFinishing/TypesofDyes.aspx].

(g) Vat dyes

INDIGO, probably the oldest dye known to man is one of the most important

members of this group. Natural indigo extracted from the plant 'Indigofera tinctorie'

was used by the Egyptians in 200 BC. The first synthetic indigo was introduced to the

textile trade in 1897 and had the effect of completely replacing the natural product.

Although the vat dyes may be divided into three chemical groups, they are similar if

that they are insoluble in water and become water soluble when reduced in the

presence of an alkali. After dyeing, the fabric is oxidized and the dye again becomes

water insoluble. Because of the time consuming and costly procedure in reducing vat

dye into a water-soluble complex, dye manufacturers have produced a stabilized

water-soluble vat dye. This dye can be applied to cotton and viscose rayon by the

methods used by applying direct cotton dyes. After the dyeing, a simple treatment

restores the vat dye to its normal insoluble state. Solubilized vat dyes have an affinity

for cellulose and animal fibres.

[www.textileschool.com/School/TextileFinishing/TypesofDyes.aspx].

1.3 DISCHARGE STANDARDS FOR INDUSTRIAL WASTEWATERS

Standards for the discharge of wastewaters from various industries are directly

9

linked to the wastewater regulations and the water pollution control policies in force

in the country/state concerned. After reviewing the technological capability and the

limitations of the wastewater treatment systems as existing in the industries; the

Pollution Control Board/Ministry of Environment and Forests, Govt. of India, have

fixed maximum allowable limits of the pollutants for different industries as given in

Tables 1.3 - 1.7.

Table 1.3 MINAS for cotton textile industries (composite and processing)

Parameter Concentration not to exceed,

milligram per liter (except

for pH and bioassay)

Common : pH 5.5. to 9.0

Suspended solids 100

Bio-chemical oxygen demand, 5

days 20oC

150

Oil and grease 10

Bio-assay test 90% survival of fish of after

96 hours

Special :

Total chromium (as Cr) 2

Sulphide (as S) 2

Phenolic compounds (as C6H5OH) 5

Source: http://www.cpcb.nic.in/standard41.htm

Table 1.4 MINAS for dye and dye intermediate industry

Parameter Concentration not to exceed milligrams per

liter (except for pH, temperature and bio-

assay)

Suspended Solids 100

pH 6 to 8.5

Temperature

Shall not exceed 5oC above the ambient

temperature of the receiving body.

Mercury (as Hg) 0.01

Hexavalent Chromium (as Cr) 0.1

Total Chromium (as Cr) 2.0

Copper (as Cu) 3.0

Zinc (as Zn) 5.0

Nickel (as Ni) 3.0

Cadmium (as Cd) 2.0

Chloride (as Cl) 1000

Sulphate (as SO4) 1000

10

Phenolic Compounds

(as C6H5OH)

1.0

Oil ad Grease 10

Bio-assay Test (with 1:8

dilution of effluents)

90% survival of Test animals after 96 hours.

Source: http://www.cpcb.nic.in/standard41.htm

Table 1.5 Composite woolen mill: wastewater discharge standards

Parameter Concentration not to exceed,

milligram per liter (except for

pH and bioassay)

Common : pH 5.5. to 9.0

Suspended solids 100

Bio-chemical oxygen demand,

5 days 20oC

150

Oil and grease 10

Bio-assay test 90% survival of fish after 96

hours

Special :

Total chromium (as Cr) 2

Sulphide (as S) 2

Phenolic compounds (as

C6H5OH)

5

Source: http://www.cpcb.nic.in/standard41.htm

Table 1.6 Dye and dye intermediate industry (Wastewater discharge standards)

Parameter Concentration not to exceed milligrams per liter

(except for pH, temperature and bio-assay)

pH 6.0 – 8.5

Color Hazen Unit 400.0

Suspended Solids 100.0

BOD (3 days at 27oC) 100.0

Oil and Grease 10.0

Phenolics as C6H5OH 1.0

Cadmium as Cd 0.2

Copper as Cu 2.0

Manganese as Mn 2.0

Lead as Pb 0.1

Mercury as Hg 0.01

Nickel as Ni 2.0

Zinc as Zn 5.0

Chromium as Cr6+

0.1

Total Chromium 2.0

Bio-assay test 90% survival in 96 hours.

Source: http://www.cpcb.nic.in/standard41.htm

11

Table 1.7 MINAS for pulp and paper mills

Table 1.7a MINAS for small pulp and paper mill

Parameter Discharged on to surface water Disposal on

land

PH 5.5 - 9.0 5.5 - 9.0

Suspended solids (mg/l) 100 100

BOD (mg/l) 30 100

Table 1.7b MINAS for large pulp and paper mills, capacity > 24,000

Tonnes/annum

Parameter Concentration

PH 7.5 - 8.5

Suspended Solids (mg/l) 50

BOD (mg/l) 30

COD (mg/l) 350

TOCl (kg/tonne of paper) 2

Table 1.7c MINAS for caustic chlorine plant

Parameter Concentration

PH 5.5-9.0

Mercury in the final effluent (mg/l) 0.01

Mercury bearing wastewater

generation

10 kilo-liter/tonne of caustic produced

Source: Central Pollution Control Board, New Delhi website

1.4 TOXICITY OF COLOR AND DYES

The worldwide high level of production and extensive use of dyes generate

colored wastewater which causes environmental pollution. Dyes and pigments are

widely used in textile, leather, paper, plastic and other industries. The effluents of

these industries are characterized by fluctuating pH with large load of suspended

solids and COD [Sivraj et al., 2001]. Discharging large amount of dyes into water

12

resources, accompanied by organics, bleaches and salts, can affect the physical and

chemical properties of fresh water. The color of the effluent discharged into receiving

waters affects the aquatic flora and fauna, and causes many water borne diseases.

Some dyes are carcinogenic and others after transformation or degradation yield

compounds such as aromatic amines, which may be carcinogenic or otherwise toxic

[Maguire, 1995]. Ludhiana, Panipat, Pali, Bichchri, Patancheru, Jetpur, Ahmedabad,

Surat and Tirupur are some of the country's most polluted zones.

In addition, dyes accumulate in sediments at many sites, especially at

locations of wastewater discharge, which has an impact on the ecological balance in

the aquatic system. Ground water systems are also affected by these pollutants

because of leaching from soil [Sharma et al., 1999]. Thus, dyes in wastewater have to

be removed before it is discharged into a water body or on land.

There are a group of textile dyes that can cause bladder cancer in people who

worked with or around the dyes. These textile dyes are known as benzidine dyes. The

colored dye effluents are generally considered to be highly toxic to the aquatic biota

and affect the symbiotic process by disturbing the natural equilibrium through

reduced photosynthetic activity due to the coloration of the water in streams. The

nonbiodegradable, toxic and inhibitory nature of spent dye baths has a considerable

deleterious effect on the environmental matrix (water and soil). Some dyes are

reported to cause allergy, dermatitis, skin irritation, cancer and mutations in humans

[Gao et al., 2010].

1.5 COLOR

Color measurement and representation

There are three methods of color measurement:

13

1. Visual comparison method

2. Spectrophotometric method

3. Tristimulus filter method

It should be noted that color is pH dependent and when representing color, pH

should be indicated.

Out of the above methods spectrophotometric method is very useful and

efficient in wide range of color solution. We can use it in two ways. First we can give

the color in the Hazen unit. 1 Hazen unit is corresponding to the color of 1 mg/l

solution of Pt-Co. We can make some different unit standard solutions by varying

concentration of the Pt-Co solution. We take the transmittance of the solution by

spectrophotometer and make a calibration chart. The sample is taken, the turbidity is

removed and then transmittance is checked. This will give the color unit of the

sample.

Secondly, if one does not require color unit and only change is to be measured

then there is no need to prepare calibration chart with Pt-Co solution. The calibration

chart can be prepared by the sample only and at any stage we can check the

concentration of the sample. The color can also be represented as the load in kg per

tonne of the effluent or kg per tonne of product produced.

1.6 TREATMENT METHODS OF DYE BEARING WASTEWATER

Currently, various chemical, physical and biological treatment methods are

used to remove dyes from wastewater. Various chemical methods are oxidative

processes, H2O2-Fe (II) salts (Fentons reagent), ozonation, photochemical, sodium

hypochloride (NaOCl), cucurbituril and electrochemical destruction.

14

In electrochemical method, electricity is used which provide powerful tool

for driving chemical reaction. The chlorides of calcium, magnesium, potassium and

sodium are most commonly used electrolytes. Electrochemical methods have been

successfully applied in the purification of several industrial wastewaters as well as

landfill leachate [Vlyssides et al., 1999]. Many dyes may be effectively decolorized

using chemical oxidizing agents such as chlorine in the form of liquid or gas. Ozone is

a more powerful oxidant than chlorine and it is used for oxidizing dye wastewater.

Environmentally, H2O2 is a friendly oxidant [Hosny et al., 2005].

The degradation of organic matter in colored solutions of different classes of

dyes by ozonation in the presence of activated carbon was investigated. The

combination of activated carbon with ozone enhanced the decolorization of the

solutions and especially the mineralization of the organic matter. Activated carbon

acts both as an adsorbent and as a catalyst in the reaction of ozonation [Patrı´cia et al.,

2005].

Heterogeneous photocatalysis has been considered as a cost effective

alternative for the purification of dye containing wastewater. Indeed, recent studies

have demonstrated that photocatalysis can be used to mineralize organic compounds

or degrade dyes using TiO2 under UV irradiation. Moreover, photocatalysis does not

require expensive oxidants and can be carried out at mild temperature and pressure

[Abdelkahhar et al., 2005].

Physical treatment methods for the removal of dyes are adsorption, membrane

filtration, ion exchange, irradiation and electrokinetic coagulation. Surfactants and

dyes with high molecular weights are successfully removed by the

coagulation/flocculation processes followed by sedimentation, flotation and filtration

15

respectively. The main advantage of the conventional processes like coagulation and

flocculation is decolorization of the waste stream due to the removal of dye molecules

from the dye bath effluents, and not due to a partial decomposition of dyes, which can

lead to an even more potentially harmful and toxic aromatic compound. The major

disadvantage of coagulation/flocculation processes is the production of sludge. The

production of large amounts of sludge occurs, and this results in high disposal costs

[Gahr et al., 1994]. However, the sludge amount could be minimized if only a low

volume of the highly colored dye bath could be eliminated by this chemical treatment

directly after the dyeing process [Vera et al. 2005]. In electrocoagulation, pollutants

were destroyed such as organic to carbon dioxide and water at anode.

Electrocoagulated sludge contains less bound water besides being more shear resistant

and readily filterable.

Ion-exchange has not been widely used for the treatment of dye-containing

effluents [Slokar and Le Marechal, 1997]. Advantages of this method include no loss

of adsorbent on regeneration, reclamation of solvent after use and the removal of

soluble dyes. A major disadvantage is cost. Organic solvents are expensive and the

ion exchange method is not very effective for disperse dyes [Mishra and Tripathy,

1993].

Membrane filtration is suitable for water recycling within a textile dye plant if

the effluent contains low concentration of dyes, but it is unable to reduce the

dissolved solid content, which makes water re-use a difficult task.

Ionizing radiation may be promising for the treatment of textile dye waste

effluents, because the effect of radiation can be intensified in aqueous solution in

which the dye molecules are degraded effectively by the primary products formed

16

from the radiolysis of water [Getoff and Lutz, 1985]. Dye containing effluent may be

treated in a dual-tube bubbling reactor. This method showed that some dyes and

phenolic molecules can be oxidized effectively at a laboratory scale only [Hosono et

al., 1993].

The removal of color by using biological treatment is widely used. The use of

wood rotting fungus, white Rot fungi has been used for effective color removal. Other

fungi such as, Hirschioporus larincinus, Inonotus hispidus, Phlebia tremellosa and

Coriolus versicolor have also been shown to decolorize dye-containing effluent

[Banat et al., 1996; Kirby, 1999]. The microorganism used are Pseudomonas

pseudomallei 13NA, Rhodotorulae rubra and Rhodotorulae sp., P. chrysosporium

BKM-F-1767 Bacillus subtilis IFO 13719, Nocardia globerula, Nocardia coralline,

P. chrysosporium ME446, Coriolus versicolor, Funalia trogii, Laetiporus sulphureus,

Cyathus bulleri, Cyathus stercoreus Cyathus striatus, P. chrysosporium NCIM 1197

and P. chrysosporium MTCC no. 787 [Pearce et al., 2003].

1.7 COMPARISION OF VARIOUS ADSORBENTS

Dyes and pigments are widely used as the coloring agents. Dyes are used in

textiles, food and beverage industries and printing processes. The total dye

consumption of the textile industry worldwide is in excess of 107 kg per year [Ahmad

et al., 2010]. However, approximately 1 million kg/yr of dyes are discharged into

water streams by the textile industry [Cestari et al., 2010]. The cost of adsorption

process is mainly dependent on the cost of adsorbent used for the removal of

dye from wastewater. Activated carbon (AC) is the most popular adsorbent, which

has been used with great success. It becomes more problematic for developing

countries to afford the cost and demand of activated carbon. However, due to high

17

cost of GAC and about 10-15 % loss during its regeneration, alternate adsorbents are

being explored. Many researchers have studied the feasibility of using low cost

materials, such as saw dust (SD) [Kalavathy and Miranda, 2010; Sharma et al., 2009;

Ahmad et al., 2009], bagasse fly ash[Mane et al., 2007a], rice husk ash [Mane et al.,

2007b], waste orange peel [Namasivayam et al., 1996], banana pith [Namasivayam et

al., 1998], bottom ash [Gupta et al., 2004; Gupta et al., 2009; Mittal et al., 2005], and

deoiled soya [Mittal et al., 2008]. The other low cost adsorbents such as rice husk

[McKay et al., 1986], kaolin [Nandi et al., 2009], bentonite clay [Ramkrishna and

Viaraghavan, 1997], neem leaf powder [Bhattacharya and Sharma, 2003], powdered

activated sludge [Kargi and Ozmıhc, 2004], perlite [Dogan and Alkan, 2004] and

powdered peanut hull [Gong et al., 2005] were used. Natural and modified clays like

sepiolite [Mahir et al., 2005], zeolite [Armagan et al., 2004], bamboo dust [Kannan

and Sundaram, 2001], coconut shell [Manju et al., 1998], groundnut shell [Kannan

and Sundaram, 2001], rice straw [Hameed and EI-Khaiary 2008], duck weed

[Waranusantigul et al., 2003], sewage sludge [Otero et al., 2003], sawdust carbon

[Jadhav and Vanjara, 2004], agricultural waste and timber industry waste carbons

[Bansal et al., 2009] and gram husk [Jain and Sikarwar, 2006] as low cost adsorbents

used by earlier researchers for removal of various dyes from wastewaters. Critical

review of low cost adsorbents for wastewater treatment has been presented by earlier

researchers [Gupta and Suhas, 2009; Mall et al., 1996; Bailey et al., 1999; Demirbas,

2009]. Hence, low cost materials are sorely needed which are comparable to activated

carbon in terms of adsorption capacity, economic feasibility and should be locally

available. The total cost for the preparation of 1 kg of adsorbent is Rs. 36/-, Rs. 81/-,

Rs. 29/- and Rs. 35/- for activated tamarind seeds, activated neem leaves, activated

sawdust, and activated flyash respectively. The commercially available adsorbent

18

(activated carbon) is for Rs. 500 per kg. This indicates that the cost associated with

these adsorbents is quite lesser when compared to that of commercial activated carbon

In general; technical applicability and cost-effectiveness are the key factors that play

major roles in the selection of the most suitable adsorbent. Various low-cost

adsorbents derived from agricultural waste, industrial by-product or natural material

are evaluated and compared to those of activated carbon [Kurniawan et al., 2006].

Saw dust shows suitable alternative to activated carbon for the removal of dyes from

wastewaters [Khattri and Singh, 2009; Ozacar and Sengil, 2005].

1.8 SAW DUST AS BEST AVAILABLE ADSORBENT

The by-products from the forestry and agricultural industries could be

assumed to be low-cost adsorbents since they are abundant in nature, inexpensive,

require little processing and are effective materials [Demirbas, 2009]. Saw dust is an

abundant by-product of the wood industry that is either used as cooking fuel or as

packing material [Garg et al., 2004]. Saw dust is easily available at negligible price

[Hameed and Khaiary, 2008]. The role of saw dust materials in the removal of

pollutants from aqueous solutions has been reviewed [Shukla et al., 2002]. Sawdust

has proven to be a promising effective material for the removal of various dyes.

Various researchers have utilized Beech sawdust [Batzias and Sidiras, 2007], Oak

wood saw dust [Ferrero, 2007], Neem sawdust (Azadirachta indica) [Khattri and

Singh, 2009] and Pine wood saw dust [Khattri and Singh, 2009; Ozacar and Sengil,

2005] for removal of dyes. Teakwood saw dust [Naiya et al., 2005], saguan (Tectona

grandis) wood saw dust [Sharma et al., 2009], Raw saw dust (RSD) [Kalavathy and

Miranda, 2010], Meranti tree sawdust [Ahmad, et al., 2009], Indian Rosewood saw

dust (Dalbergia sissoo) [Garg et al., 2004] and Hard-wood sawdust [Dutta et al.,

2001] was also utilized for removal of harmful substances from wastewater. Timber

19

of Indian Eucalyptus wood tree is widely used for furniture making and the waste

sawdust so produced is generally used as cooking fuel due to its zero or negligible

cost.

1.9 BRILLIANT GREEN: PROPERTIES AND HEALTH EFFECTS

Color Index (C.I.) = 42040, chemical formula = C27H34N2 O4 S, Molecular weight =

482.62; Nature = basic green 4. The Molecular structure of BG is shown in Fig. 1.1.

The properties and health effects of BG are mentioned in Table 1.8.

Fig. 1.1 Molecular structure of BG

Table 1.8 Properties and health effects of BG

Sr.

No.

Name of property and

health effects

Properties and health effects

1 Appearance Yellow-green to green powder

2 Odor Odorless

3 Melting Point 210 oC (410

oF) Decomposes

4 Vapor Density (Air=1) 16.6

5 % Volatiles by volume

@ 21oC (70

oF)

0

6 Boiling Point No information found

7 Stability Stable under ordinary conditions of use and

storage

8 Hazardous

Decomposition Products

May form carbon oxides, nitrogen oxides, and

sulfur oxides when heated to decomposition.

(Prepared by: Environmental Health & Safety,

(U.S.A.)

9 Inhalation May cause irritation to the respiratory tract.

Symptoms may include coughing and shortness

of breath

10 Ingestion Causes irritation to the gastrointestinal tract.

Symptoms may include nausea, vomiting and

diarrhea

11 Skin Contact May cause irritation with redness and pain

12 Eye Contact BG contains a cationic dye. Similar dyes have

caused permanent injury to the eyes of humans

and laboratory animals

13 LDLo 5 mg/kg (skin and eye irritant)

14 LD50 Not available

15 Fire Extinguishing Media Dry chemical, foam, water or carbon dioxide

16 Environmental Terrestrial: High mobility in soil and is likely to

leach. Aquatic: Will not adsorb to suspended

solids or organic matter. Atmospheric: Remain as

particulates and is removed by wet deposition.

Will not biodegrade and has a low

bioconcentration potential.

[http://www.merckmedicus.com/pp/us/hcp/thcp_dorlands_content.jsp?pg=/ppdocs/us/

common/dorlands/dorland/dmd-g-023.htm].

[http://www.jtbaker.com/msds/englishhtml/b3840.htm,

http://www.sussex.ac.uk/Units/safety/sgn/sgn27.pdf].

BG is effective against gram-positive bacteria. The main advantage of BG

over the more common antiseptics such as iodine is that it does not irritate mucous

membranes. Gram-positive bacteria are those that are stained dark blue or violet by

Gram staining. This is in contrast to Gram-negative bacteria, which cannot retain the

crystal violet stain, instead taking up the counter stain (safranin or fuchsine) and

appearing red or pink. Gram-positive organisms are able to retain the crystal violet

stain because of the high amount of peptidoglycan in the cell wall. Gram-positive cell

walls typically lack the outer membrane found in Gram-negative bacteria.

BG dye is used for various purposes, e.g. biological stain, dermatological

agent, veterinary medicine, an additive to poultry feed to inhibit propagation of mold,

intestinal parasites and fungus [Nandi et al., 2009].

21

It is also extensively used in textile dying and paper printing [Mittal et al.,

2008]. About 0.8–1.0 kg of BG is utilized per tonne of paper produced [Mane et al.,

2007a, b]. However, in humans, BG causes irritation to the gastrointestinal tract;

symptoms include nausea, vomiting and diarrhea [Mittal et al., 2008]. It also causes

irritation to the respiratory tract, leading to cough and shortness of breath. Skin

contact causes irritation with redness and pain [Mittal et al., 2008]. BG may form

hazardous products like carbon oxide, nitrogen oxide, and sulfur oxides when heated

to decomposition.

1.10 CONGO RED: PROPERTIES AND HEALTH EFFECTS

The CR dye [C.I. = 22120, chemical formula = C32H22N6Na2O6S2, FW = 696.7,

max = 500 nm]. The structure of CR is illustrated in Fig. 1.2.

CR (1-naphthalenesulfonic acid, 3, 3-(4, 4-biphenylenebis (azo)) bis (4-amino-)

disodium salt) is a benzidine-based anionic disazo dye [Mall et al., 2005]. CR

containing effluents are generated from textiles, printing and dyeing, paper, rubber,

plastics industries, etc [Cheng et al., 2011]. Due to its structural stability, CR is

difficult to biodegrade [Ahmad and Kumar 2010]. This dye is known to metabolize to

benzidine, a known human carcinogen [Mall et al., 2005]. It is investigated as a

mutagen and reproductive effector. It is a skin, eye, and gastrointestinal irritant. It

may affect blood factors such as clotting, and induce somnolence and respiratory

problems [Mittal et al., 2009].

Fig. 1.2 Molecular structure of CR

22

NH2

SO3Na

N N N N

NH2

SO3Na