chapter-1 introduction and literature...

Chapter-1 Introduction and Literature Survey

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POLLUTION PROBLEM

Pollution is a problem for mankind on this earth. Before 19th

century with no

much industrial revolution, people lived more in harmony with their immediate

environment. As industrialization has spread around the globe, so the problem of

pollution has spread with it. When earth's population was much smaller, no one

believed pollution would ever cause such a serious problem. It was once popularly

believed that the oceans were far too big to pollute. With the population growth, the

technology no longer remained simple and man started exploiting nature rather

ruthlessly. Today, with over 8 billion people on the planet, it has become apparent

that there are limits of creating pollution. Pollution is one of the signs that humans

have exceeded its limits. It has attained the stage that the earth’s in-built ecosystem

could no longer dilute, decompose and recycle the waste products.

Nature’s tolerance capacities and generosity knows no boundaries but man’s

carelessness has crossed it, thus degrading environment is the obvious

consequence. The splendid plentifulness of nature is a heritage that should never be

spoiled. But the unlimited rapacious exploitation of nature by man has disturbed the

delicate ecological balance existing between living and non-living components on

the planet earth. This undesirable situation created by man has threatened the

survival of man himself and other living biota on the earth. It’s about time that we

preserve this for our future generation or face catastrophe that cannot be reckoned.

Since the beginning of the 20th

century there has been a huge growth in the

manufacture and use of synthetic chemicals. Environmental pollution and other

environmental problems have become important with increase of world’s

population and development of industrial applications. There are many possible

sources of chemical contaminations. These include wastes from chemicals

industries, metal plating operations, textile dying, wood preservatives, leather

industries, pesticides run off from agricultural lands and the other industrial

applications and productions [1].


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SOURCES OF WATER POLLUTION

Dumping of industrial wastes, containing heavy metals, harmful chemicals, by-

products, organic toxins and oils, into the nearby source of water is one of the

visible causes of water pollution.

Another cause for the contamination of water is the improper disposal of human

and animal wastes.

Effluents from factories, refineries, injection wells and sewage treatment plants

are dumped into urban water supplies, leading to water pollution.

A number of pollutants, both harmful and poisonous, enter the groundwater

systems through rain water.

The residue of agricultural practices, including fertilizers and pesticides, are

some of the major sources of water pollution.

Untreated pollutants are drained into the nearest water body, such as stream,

lake or harbor, causing water pollution.

Another major source of water pollution comprises of organic farm wastes.

When farm land, treated with pesticides and fertilizers, is irrigated, the excess

nitrogen and poisons get mixed into the water supply, thereby contaminating it.

Figure 1.1 Sources of water pollution


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All industries use specific chemicals or the other raw materials to produce

their final products. If the final production involves long steps reaction which is the

total of many reactions then each process can produce hazardous wastes. A waste is

considered hazardous if it is reactive, ignitable, corrosive or toxic. About ninety

five chemicals have been defined as toxic including phenols on the basis of

production volume, exposure and biological effects [2].

The numbers of organic compounds that have been synthesized since the

turn of the century now exceeds half a million and 10,000 new compounds are

added each year. As a result, many of these compounds are now found in the

wastewaters originated from most municipalities and communities. Currently, the

release of volatile organic compounds (VOCs), non-volatile or semi-volatile

organic compounds and volatile toxic organic compounds (VTOC) found in

wastewater is of great concern in the operation of both collection systems and

treatment plants.

Many industries are located near water or fresh water streams. These

industries discharge their untreated effluents into the nearest water reservoirs. Most

of the industries discharge highly toxic heavy metals such as chromium, arsenic,

lead, mercury etc. along with hazardous organic and inorganic wastes. For

example, river Ganges, receives waste from textile, sugar, paper and pulp mills,

tanneries, rubber and plastic industries. Most of these pollutants are resistant to

breakdown by microorganism (non biodegradable) and chemically polluted water

damages the growth of crop and is unsafe for drinking purposes.

HARMFUL EFFECTS OF WATER POLLUTION

Pollution affects the chemistry of water. The pollutants, including toxic

chemicals, can alter the acidity, conductivity and temperature of water.

As per the records, about 14000 people perish or incur of various infectious

diseases due to the consumption of contaminated drinking water.

The concentration of bacteria and viruses in polluted water causes increase in

solids suspended in the water body, which in turn, leads to health problems.


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Marine life becomes deteriorated due to water pollution. Lethal killing of fish

and aquatic plants in rivers, oceans and seas is an after-effect of water

contamination only.

Diseases affecting the heart, poor circulation of blood, the nervous system, and

ailments like skin lesion, cholera and diarrhea are often linked to the harmful

effects of water pollution.

Carcinogenic pollutants found in polluted water might cause cancer.

Alteration in the chromosomal makeup of the future generation is foreseen, as a

result of water pollution.

Discharges from power stations to nearest water body reduce the availability of

oxygen.

The flora and fauna of rivers and oceans is adversely affected by water

pollution.

Polluted municipal water supplies are found to pose a threat to the health of

people using them.

A number of waterborne diseases are produced by the pathogens present in

contaminated water, affecting humans and animals alike.

The wastewaters from the industries contain hydrocarbons which may

present in many forms such as chlorinated hydrocarbons, halogenated

hydrocarbons, organophosphates and non volatile or semi volatile aromatic

hydrocarbons. Phenol, as an aromatic semi volatile hydrocarbon is present in

wastewaters of most industries such as high temperature coal conversion,

petroleum refining, resin and plastic, leather and textile manufacturing [3], oil

refineries, chemical plants, coke ovens, aircraft maintenance, foundry operations,

paper-processing plants, paint manufacturing, rubber reclamation plants, nitrogen

works, and fiberglass manufacturing in different ranges from 1ppm to 7000 ppm

(Table 1.1) [4].

Phenolic constituents stand at eleventh rank out of the 126 chemicals which

have been pointed as priority pollutants according to United States Environmental

Protection Agency (EPA) [5]. Phenolic derivatives belong to a group of common

environmental contaminants and basic structural unit for variety of synthetic


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organic compounds. Phenols and substituted phenols are significant contaminants

in medical, food and environmental matrices. Their presence even at low

concentrations can be an obstacle to the use of water. Phenols cause unpleasant

taste and odour of drinking water and can exert negative effects on different

biological processes. Phenolic compounds are a class of polluting chemicals, highly

soluble in water, easily absorbed by animals and humans through the skin and

mucous membranes. Their toxicity affects directly a great variety of organs and

tissues, primarily lungs, liver, kidneys and genitourinary system. Human

consumption of phenol-contaminated water can cause severe pain leading to

damage of the capillaries ultimately causing death.

Table 1.1 Levels of phenolic compounds reported in industrial wastewaters

Industrial Source Concentration of phenolic

compounds (ppm)

Petroleum refineries 40 - 185

Petrochemical 200 - 1220

Textile 100 - 150

Leather 4.4 - 5.5

Coke ovens (without dephenolization) 600 - 3900

Coal conversion 1700 - 7000

Ferrous industry 5.6 - 9.1

Rubber industry 3 - 10

Pulp and paper industry 22

Wood preserving industry 50 - 953

Phenolic resin production 1600

Phenolic resin 1270 - 1345

Fiberglass manufacturing 40 - 2564

Paint manufacturing 1.1

Phenol containing water, when chlorinated during disinfection of water also

results in the formation of chlorophenols. The majority releases of chlorophenols to

the environment are caused by spills and leachate from treated wood. They are also

breakdown products of agricultural pesticides. Chlorophenols are also emitted


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during treated wood combustion. Significant amounts of chlorophenol are produced

during the chlorine bleaching process in pulp and paper-mills, incineration and

water chlorination. The releases from manufacturing industries are significant with

accidental spillage being negligible. There are believed to be no significant natural

sources of them. Most of these compounds are recognized as toxic carcinogens.

Nitroaromatic compounds are used in the synthesis of dyes, explosives,

pesticides and drugs. In particular, nitrophenols are involved in much of this

chemistry. For example, 4-Nitrophenol (4-NP/PNP) is the final product of the

enzyme catalyzed, biochemical reaction of acetyl cholinesterase and paraoxon.

Nitrophenol isomers have even served as model systems to explore the role of

silver nanoparticles in the conversion of aromatic nitro-compounds to aromatic

amines, which has industrial and environmental significance. In the US, eleven

phenols are listed as priority pollutants by the EPA including 2-Nitrophenol (2-NP)

and 4-NP [6].

Industrial sources of phenolic contaminants such as pulp and paper, resin

manufacturing, gas and coke manufacturing, explosives, tanning, textile, plastics,

wood preserving chemicals rubber, pharmaceutical, oil refineries, coal gasification

sites and petrochemical units, etc. [7-10] generate large quantity of phenols residue.

Besides that the phenolic derivatives are widely used as intermediates in the

synthesis of plastics, colours, pesticides and insecticides, etc. Degradation of these

substances means the appearance of phenol and its derivatives in the environment

[11]. Henceforth, the determination of phenolic compounds is of great importance

due to their toxicity and persistency in the environment [12]. The estimation and

detoxification of phenol from the wastewaters is, therefore of great importance.

HEALTH EFFECTS OF STUDIED PHENOLS

PHENOL

Phenol has acute and chronic effects on human health. Inhalation and dermal

exposure to phenol is highly irritating to skin, eyes and mucous. These inverse

effects also known as acute (less than 14 days-exposure) effects of phenol.


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The other acute health effects are headache, dizziness, fatigue, fainting, weakness,

nausea, vomiting and lack of appetite at high levels. Effects from chronic exposure

(longer than 365 days) include irritation of the gastrointestinal tract. Phenol also

can change blood pressure and can cause liver and kidney damage. Nervous system

is affected negatively for long time exposures (EPA, 2002). EPA has classified

phenol as a Group D, not classifiable as to human carcinogenicity. Animal studies

have not shown tumors resulting from oral exposure to phenol, while dermal

studies have reported that phenol applied to the skin may be a tumor promotor

and/or a weak skin carcinogen in mice.

ortho-CHLOROPHENOL

Inhalation of o-Chlorophenol (OCP) can cause cough, shortness of breath,

sore throat, abdominal pain, convulsion, drowsiness and weakness. Skin and eye

absorption may cause redness, pain and blurred vision. Chlorophenol spills have

resulted in fish kills. Exposure to large quantities of chlorophenol impairs algal

primary production and reproduction. Biodegradation in soils is likely to be

reasonably rapid (days-weeks) and it binds moderately to soil/sediment particles,

however for significant spills to land, leaching to groundwater may be possible.

Bioaccumulation of chlorophenols appears to be moderate.

para-NITROPHENOL

Exposure of para-Nitrophenol (PNP) irritates eyes, skin and respiratory tract

and may cause the inflammation of those parts. It has a delayed interaction with

blood and forms met-haemoglobin which is responsible for the met-

hemoglobinemia, potentially causing cyanosis, confusion and unconsciousness.

When ingested, it causes abdominal pain and vomiting. Prolonged contact with skin

may cause allergic response.

http://en.wikipedia.org/wiki/Methaemoglobin

http://en.wikipedia.org/wiki/Methemoglobinemia

http://en.wikipedia.org/wiki/Methemoglobinemia


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USES OF STUDIED PHENOLS

PHENOL

Phenol is used in making plywood, construction, automotive and appliance

industry as a raw chemical and in the production of nylon, epoxy resins. In

addition, it becomes a disinfectant, slime-killing agent and an additive in

medicines. Production of biphenol A is another usage area of phenol [4].

ortho-CHLOROPHENOL

It is used as disinfectant agent and pesticide. This particular compound has

fewer applications but is an intermediate in the polychlorination of phenol.

para-NITROPHENOL

It is used for the synthesis of drugs as an intermediate eg. paracetamol. It is

used as the precursor for the preparation of phenetidine and acetophenetidine

indicators and raw materials for fungicides. In peptide synthesis, carboxylate

ester derivatives of para-nitrophenol may serve as activated components for

construction of amide moieties.

Most of the chemicals present in wastewater are generally toxic and cause

adverse effects on aquatic ecosystem and human life. As a result of development of

better analytical systems and better health monitoring technologies, the acceptable

minimum concentration of these chemicals is progressively decreasing. As such,

stringent regulations have been introduced by most countries with respect to

presence of these chemicals in water and which binds industries and other bodies to

minimize the concentrations appreciably before the wastewater is discharged into

natural water bodies containing good quality of water. In view of importance of

pollution control technologies require substantial financial input and many times,

their use is restricted because of cost factors overriding the importance of pollution

control. It has therefore, been the efforts of many workers to develop cost effective

technologies for the wastewater treatments. Thus, the search for safe, convenient

and cost effective treatment of wastewater is still going on.

http://en.wikipedia.org/wiki/Disinfectant

http://en.wikipedia.org/wiki/Chlorination

http://en.wikipedia.org/w/index.php?title=Phenetidine&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Acetophenetidine&action=edit&redlink=1

http://en.wikipedia.org/wiki/Peptide_synthesis

http://en.wikipedia.org/wiki/Carboxylate_ester



http://en.wikipedia.org/wiki/Amide


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TECHNOLOGIES AVAILABLE FOR THE REMOVAL OF

PHENOLIC COMPOUNDS

Wastewaters are typically classified as industrial wastewater and municipal

wastewater. Industrial wastewater with characteristics compatible with municipal

wastewater is often found to be discharged to the municipal sewers. From

industries to industries the characteristics of industrial wastewaters vary greatly and

consequently the treatment process for industrial wastewater also varies.

There are several methods reported for the removal of pollutants from the

effluents/wastewater. These technologies can be divided into three categories:

physical, chemical and biological. All of them have advantages and drawbacks.

Because of the high cost and disposal problems, many of these conventional

methods for treating phenol bearing wastewater have not been widely applied at

large scale in the industries.

Water treatment process selection is tedious assignment involving the

consideration of many factors which include available space for the treatment,

facilities, reliability of process equipment, waste disposal constraints, desired

finished water quality and capital and operating cost, including chemical cost.

Wastewater to be treated must be characterized fully, particularly with a thorough

chemical analysis of possible waste constituents and their chemical and metabolic

products. Current treatment technologies are available to remove phenols from

wastewaters. Both physicochemical and biological treatment techniques are

successful in full scale industrial use and high efficiencies of phenol removal can

be obtained. Phenolic wastes also contain other contaminants which require

additional special treatment procedures. Some of them involve physico-chemical

processes, such as coagulation [13, 14], reverse osmosis by membrane filtration

[15, 16], electrochemical oxidation [17], catalytic oxidation [18, 19], ion exchange

[20], biological methods [21, 22], enzyme treatment [23], solvent extraction [24],

adsorption [3, 8, 9, 25, 26], pervaporation [27], advanced oxidation processes [28,

29], disinfection by ozone [30, 31], activated sludge [32], photo catalysis [33] etc.

For example, in case of wastewaters from petroleum industry, organic pollutants

are removed by biological treatment or chemical oxidation methods [4]. In addition


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to biological treatment and chemical oxidation methods, another method for phenol

removal is also used such as adsorption on to granular activated carbon [34, 35].

Choice of a suitable and effective treatment technique depends on economic factors

and special wastewater characteristics.

Among these, a particular treatment may not be effective sometimes in

removing all pollutants and in such cases; a number of processes may be

incorporated in conjunction, so that all type of pollutants can be tackled [35].

However, these methods have their own shortcomings and limitations. For

example, the method based on chemical/ biological oxidation, ion exchange and

solvent extraction have shown low efficiency for the removal of trace levels of

pollutants [37]. Further, coagulation requires pH control and causes the problem of

sludge disposal, whereas ozonation while removing colour effectively does not

minimize chemical oxygen demand (COD) and also comprise high operational

cost. Most of methods suffer from some drawbacks, such as high capital and

operational cost, regeneration cost and problem of residual disposal. Among the

various technologies available for water pollution control listed above, the

‘sorption’ process is considered to be the most effective and proven technology

having wide potential applications in both water and wastewater treatment [38].

The commonly used treatment methods are discussed in the following paragraphs.

CHEMICAL METHODS

Chemical methods include coagulation or flocculation combined with

flotation and filtration, precipitation–flocculation with Fe (II)/Ca(OH)2, electro

flotation, electro kinetic coagulation, conventional oxidation methods by oxidizing

agents (ozone), irradiation or electrochemical processes [17-19]. These chemical

techniques are often expensive, and although the phenols are removed,

accumulation of concentrated sludge creates a disposal problem. There is also the

possibility that a secondary pollution problem will arise because of excessive

chemical use. Chemical oxidation by ozone and chlorine has been reported

effective for some toxic organics including phenol. It is possible to reach 48 %

removal efficiency for phenol at pH 7 and initial phenol concentration of 1000mg/L


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using ozone as an oxidant. Several factors influence the effectiveness of the

oxidation process, such as reactivity of the ozone itself with the target compound,

the rate of reactivity, the ozone demand to achieve a desired degree of treatment,

the extent of incidental stripping associated with ozone dispersion and other

treatment variables such as pH and temperatures [28-31]. For example, the ozone

treatment of phenol proceeds approximately twice faster at pH 11 than at pH 7 [4].

Recently, other emerging techniques, known as advanced oxidation processes [27-

29], which are based on the generation of very powerful oxidizing agents such as

hydroxyl radicals, have been applied with success for pollutant degradation.

Although these methods are efficient for the treatment of waters contaminated with

pollutants, they are very costly and commercially unattractive. The high electrical

energy demand and the consumption of chemical reagents are common problems.

SOLVENT EXTRACTION

Solvent extraction method can be predominantly applied for the separation

of organic materials from wastewaters. Solvent extraction is also called liquid

extraction and liquid-liquid extraction. Solvent extraction occurs when a waste

constituent in the wastewater is selectively removed when it is contacted with an

organic solvent, because it has more solubility in the solvent than it is in the

wastewater [24]. In this process, the solvent and the waste stream are mixed to

allow mass transfer of the contaminant from the waste to the solvent. The solvent,

immiscible in water, is then allowed to separate from the water by gravity. The

solvent solution containing extracted contaminants is called the extract. The

extracted waste stream with the contaminants removed is called the raffinate. If the

extract is sufficiently enriched, it may be possible to recover the useful materials.

For the recovery of the solvent and reusable organic chemicals from organic

materials, distillation is often employed. The solvent extraction process has found

wide application in the ore processing, food processing and the petroleum industry

[39]. Large quantity of solvent is required in this method to remove the

contaminants and recovery of the solvent involves tedious processes. Solvent

extraction methods are economically and environmentally unfavoured at large


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scale.

BIOLOGICAL TREATMENT PROCESS

Biological remediation methods are often cheaper and more environmentally

friendly than their physical or chemical counterparts (i.e., incineration, ozonation).

Biological treatment is often the most economical alternative when compared with

other physical and chemical processes. Biodegradation methods such as fungal

decolonization, microbial degradation, adsorption by (living or dead) microbial

biomass and bioremediation systems are commonly applied to the treatment of

industrial effluents because many microorganisms such as bacteria, yeasts, algae

and fungi are able to accumulate and degrade different pollutants. Unfortunately,

they are also less versatile as microbial activity is more easily affected by process

parameters such as the effluent toxicity. Hence, a more cost-efficient alternative

consists in combining physical and chemical processes with biological methods

[40].

Phenolic compounds, especially chlorinated ones, are similar to herbicides

and pesticides in structure and they are difficult to remove by biological treatment

processes because of their resistance of biodegradation [3]. However, Phenol can

be removed from wastewater by different treatment method including biochemical

ways [41]. Biological treatment involves the action of living microorganisms. The

various microorganisms utilize the waste material as food and convert it into

simpler substances by natural metabolic process. Organic waste from the petroleum

industry can be treated biologically. In addition to the traditional biological

treatment systems (activated sludge and trickling filter processes), a treatment

method called land farming and land treatment may be used. The waste is carefully

applied to and mixed with surface soil, microorganisms and nutrients may also be

added to the mixture, as needed. The toxic organic material is degraded

biologically, whereas inorganic materials are adsorbed in the soil [42]. Phenol

concentrations up to 500 mg/L are generally considered suitable for biological

treatment techniques [4]. Certain organic hazardous wastes can be treated in slurry

from in an open lagoon or in a closed vessel called a bioreactor. A bioreactor has


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fine bubble diffusers to provide oxygen and mixing device to keep the slurry solids

in suspension [42].

However, their application is often restricted because of technical

constraints. Biological treatment requires a large land area and is constrained by

sensitivity toward diurnal variation as well as toxicity of some chemicals, and less

flexibility in design and operation. Biological treatment is incapable of obtaining

satisfactory phenol removal with current conventional biodegradation processes.

Moreover, although many organic molecules are degraded, many others are

recalcitrant due to their complex chemical structure and synthetic organic origin.

PHYSICAL METHODS

Different physical methods are also widely used, such as membrane-

filtration processes [13-16] (nanofiltration, reverse osmosis, electrodialysis, etc.)

and adsorption techniques. The major disadvantage of the membrane processes is

that they have a limited lifetime before membrane fouling occurs and the cost of

periodic replacement must thus be included in any analysis of their economic

viability. In accordance with the very abundant literature data, liquid-phase sorption

is one of the most popular methods for the removal of pollutants from wastewater

since proper design of the adsorption process will produce a high quality treated

effluent. This process provides an attractive alternative for the treatment of

contaminated waters, especially if the sorbent is inexpensive and does not require

an additional pre-treatment step before its application.

Sorption is a well known equilibrium separation process and an effective

method for water decontamination applications. Adsorption has been found to be

superior compared to other techniques for water reuse in terms of initial cost,

flexibility and simplicity of design, ease of operation and insensitivity to toxic

pollutants. Also, adsorption does not result in the formation of harmful substances.


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ADSORPTION ONTO GRANULAR ACTIVATED CARBON

The most common method for the removal of dissolved organic material is

sorption on activated carbon [43], a product that is produced from a variety of

carbonaceous materials, including wood, pulp-mill char, wheat, rice husk, peat,

lignite etc. Effectiveness of these materials comes from its tremendous surface area.

The carbon is produced by charring the raw material anaerobically below 600°C

followed by an activation step consisting of partial oxidation. Carbon dioxide may

be employed as an oxidizing agent at 600-700°C, or the carbon may be oxidized by

water at 800-900°C [34, 35].

These processes develop porosity, increase the surface area and leave the

carbon atoms in arrangements that have affinities for organic compounds.

Activated carbon might be in two general types: granulated activated carbon,

consisting of particles 0.1-1mm in diameter and powdered activated carbon, in

which most of the particles are 50-100µm in diameter. For water treatment,

currently granular carbon is most widely used. It may be employed in a fixed bed,

through which water flows downward. Accumulation of particulate matter requires

periodic backwashing. Economics require regeneration of the carbon, which is

accomplished by heating it to 950°C in a steam air atmosphere. This process

oxidizes adsorbed organics and regenerates the carbon surface, with an

approximately 10% loss of carbon [1]. Activated carbons are the most widely used

adsorbents due to their excellent adsorption abilities for organic pollutants. The

high adsorption capacities of activated carbons are usually related to their high-

surface-area, pore volume, and porosity.

ADSORPTION PROCESS

The term adsorption was proposed by Bios-Reymond but introduced into the

literature by Kayser [44]. Ever since then, the adsorption process has been widely

used for the removal of solutes from solutions and harmful gases from atmosphere.

Adsorption process is efficient for the removal of organic matter from waste

effluents. Adsorption is the physical and/or chemical process in which a substance

is accumulated at an interface between two phases. For the purposes of water or


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wastewater treatment, adsorption from solution occurs when impurities in the water

accumulate at a solid-liquid interface. The substance which is being removed from

the liquid phase to the interface is called as sorbate and solid phase in the process is

known to be sorbent.

The use of term ‘sorption’ instead of adsorption became common in 19th

century, for the surface activities. Sorption is defined as being the attraction of an

aqueous species to the surface of a solid. Sorption is a rapid phenomenon of passive

sequestration separation of sorbate from an aqueous/gaseous phase onto a solid

phase. Sorption occurs between two phases in transporting pollutants from one

phase to another. It is considered to be a complex phenomenon and depends mostly

on the surface chemistry or nature of the sorbent, sorbate and the system conditions

in between the two phases. Sorption processes offer the most economical and

effective treatment method for removal of pollutants. The process is often carried

out in a batch mode, by adding sorbent to a vessel containing contaminated water,

stirring the mixture for a sufficient time, then letting the sorbent settle and drawing

off the cleansed water.

At the surface of the most solids, there are unbalanced forces of attraction

which are responsible for sorption. In cases where the sorption is due to weak Van

der Waals forces, it is called physical sorption which is reversible in nature with

low enthalpy values. On the other hand, in many systems there may be a chemical

bonding between sorbate and sorbent molecule. Such type of sorption is

chemisorption. As a result of chemical bonding, the sorption is irreversible in

nature and has high enthalpy of sorption.

Sorption phenomenon is operative in most natural physical, biological and

chemical systems. Sorption operations employing solids such as activated carbon

and synthetic resins are used widely in industrial applications and for purification

of waters and wastewaters.

Dissolved species may participate directly in air-water exchange while

sorbed species may settle with solids. Figure 1.2 illustrates a brief sorption process

for a general aromatic organic matter [45].


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Figure 1.2 Illustration of sorbed species behave differently from dissolved

molecules of the same substance

Physical sorption (physisorption) is relatively non-specific and is due to the

operation of weak forces between molecules. In this process, the sorbed molecule is

not affixed to a particular site on the solid surface; it is free to move over the

surface. The physical interactions among molecules, based on electrostatic forces,

include dipole-dipole interactions, dispersion interactions and hydrogen bonding.

When there is a net separation of positive and negative charges within a molecule,

it is said to have a dipole moment. Molecules such as H2O and N2 have permanent

dipoles because of the configuration of atoms and electrons within them. Hydrogen

bonding is a special case of dipole-dipole interaction and hydrogen atom in a

molecule has a partial positive charge. Positively charged hydrogen atom attracts an

atom on another molecule which has a partial negative charge. When two neutral

molecules which have no permanent dipoles approach each other, a weak

polarization is induced because of interactions between the molecules, known as

the dispersion interaction [46]. Figure 1.3 illustrates the main interactions and

forces during physical sorption processes [45].


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Figure 1.3 Illustration of the various molecular interactions arising from uneven

electron distributions

In water treatment, sorption of an organic sorbate from polar solvent (water)

onto a nonpolar sorbent (carboneous material) has an often interest. In general,

attraction between sorbate and polar solvent is weaker for sorbates of a less polar

nature; a nonpolar sorbate is less stabilized by dipole-dipole or hydrogen bonding

to water. Nonpolar compounds are sorbed more strongly to nonpolar sorbents. This

is known as hydrophobic bonding. Hydrophobic compounds sorb on to carbon

more strongly. Longer hydrocarbon chain is more nonpolar, so, degree of this type

of sorption increases with increasing molecular length [46].

Additionally, branched chains are usually more sorbable than straight

chains, an increasing length of the chain decreases solubility. An increasing

solubility of the solute in the liquid decreases its sorbability. For example, a

hydroxyl group generally reduces sorption efficiency. Carboxyl groups have

variable effects according to the host molecule. Double bonds affect sorbability of

organic compounds depending on the carboxyl groups. The other effective factor

on sorption is molecular size [47]. Aromatic and substituted aromatic compounds


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are more sorbable than aliphatic hydrocarbons [4]. Figure 1.4 illustrates the

sorption of an aromatic compound on to a polar surface.

Figure 1.4 Illustration of the aromatic hydrocarbon sorption on a polar inorganic

surface

Chemical sorption (chemisorption) is also based on electrostatic forces, but

much stronger forces act a major role on this process [48]. In chemisorption, the

attraction between sorbent and sorbate is a covalent or electrostatic chemical bond

between atoms, with shorter bond length and higher bond energy [46].

The enthalpy of chemisorption is very much greater than that for

physisorption and typical values are in the region of 200 kJ/mol, whereas this value

for physisorption is about 20 kJ/mol. Except in the special cases, chemisorption

must be exothermic. A spontaneous process requires a negative free energy (ΔG)

value. Because, the translational freedom of the sorbate is reduced when it is

sorbed, entropy (ΔS) is negative. Therefore, in order for ΔG to be negative, ΔH

must be negative and the process exothermic. If the enthalpy values less negative

than -25 kJ/mol, system is physisorption and if the values more negative than -40

kJ/mol it is signified as chemisorption [49].


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Table 1.2 The bond energies of various mechanisms for the sorption

Interaction between sorbent and sorbate Enthalpy (kJ/mol)

- ΔH + ΔH

Electrostatic chemical bonding > 40 > 200 chemisorption

Dispersion interactions and hydrogen

bonding

8 -40 physisorption

Dipole-dipole interaction < 8 < 20 physisorption

ADSORPTION VERSUS ABSORPTION

Adsorption is a process that occurs when a gas or liquid or solute (called

adsorbate) accumulates on the surface of a solid or more rarely a liquid (adsorbent),

forming a molecular or atomic film (adsorbate) layer. It is different from

absorption, where a substance diffuses into a liquid or solid to form a solution.

Absorption is process by which atoms/molecules or ions enter a bulk phase

of the whole volume of absorber. Figure 1.5 shows the primary differences between

the absorption and adsorption. The main difference being that, in adsorption

contaminant particles are attracted to the outer surface of the particle, while in

absorption they are actually incorporated into the particle's structure.

Absorption at the microscopic scale commonly involves adsorption at the

nanoscopic scale. For example, a molecule of water adsorbed on the surface of

single crystal/grain is part of the water absorbed in a mass of those crystals/grains

(Figure 1.6).


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Figure 1.5 Differences between Adsorption and Absorption

Figure 1.6 Sorption: Adsorption and Absorption

To design a sorption system, it is imperative to understand the process of

sorption mechanism, so that optimization can be achieved. It is also important to

understand the sorption mechanism for effective activation and regeneration of the

sorbents.

MECHANISM OF SORPTION

The mechanism of sorption on the sorbent in removal process involves the

following three steps: (1) diffusion of sorbate molecules through the solution onto


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the surface of the sorbents, (2) sorption of sorbate molecules on the surface of the

sorbents through molecular interactions and (3 & 4) diffusion of sorbate molecules

from the surface into the interior of the sorbent materials either monolayer or multi

layer. The concentration of sorbate and agitation may affect the first step of

sorption. The second step is dependent on the nature of the sorbate molecules, such

as anionic and cationic structures. The third step is usually considered as the rate

determining stage in the sorption process, which certainly should affect the sorption

of sorbate on the substrates.

Resistance to mass transfer in sorption processes can be described by two

processes, resistance due to external mass transfer through the particle boundary

layer and resistance due to intraparticle diffusion. The external mass transfer has

been described by two methods using linear and nonlinear isotherms [50]. The

major differences in the two resistance models are due to the mechanism of

intraparticle diffusion proposed, namely pore diffusion, solid diffusion or a

combination of both. Solid phase diffusion is the dominant effect in intraparticle

mass transfer. The film homogeneous solid diffusion model assumes external mass

transfer dominance in the initial stages of sorption.

Sorption phenomena are dependent on experimental conditions like pH,

temperature, sorbent dose, sorbent particle size, surface morphology of sorbent,

sorbate concentration and type and structures of the sorbates.

Figure 1.7 Mechanism of sorption process


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LITERATURE SURVEY

SORBENTS FOR POLLUTION CONTROL OF WASTEWATER

Sorbents are characterized first by surface properties such as surface area

and polarity. The high porosity and consequently larger surface area with more

specific sorption sites are the fundamental characteristic of good sorbent [51]. A

large specific surface area is preferable for providing large sorption capacity, but

the creation of a large internal surface area in a limited volume inevitably gives rise

to large numbers of small sized pores between sorption surfaces. The size of the

micropores determines the accessibility of sorbate molecules to the internal

sorption surface, so the pore size distribution of micropores is another important

property for characterizing sorptivity of sorbents. Especially materials such as

zeolite and carbon molecular sieves can be specifically engineered with precise

pore size distributions and hence tuned for a particular separation.

Most sorbents, used in pollution control tend to have porous structure; this

porous structure not only increases surface area and consequently sorption, but also

affects the kinetics of the sorption. A sorbent with high surface area and requires

less time for sorption equilibrium is considered a better one, so that the removal of

pollutants require short time treatment. Hence, for the removal of pollutants, one

generally looks to sorbents with high surface area and faster kinetics.

Surface polarity corresponds to affinity with polar substances such as water

or alcohols. Polar sorbents are thus called "hydrophillic" and aluminosilicates such

as zeolites, porous alumina, silica gel or silica-alumina are examples of sorbents of

this type. On the other hand, non-polar sorbents are generally "hydrophobic".

Carbonaceous sorbents, polymer sorbents and silicalite are typical non-polar

sorbents. These sorbents have more affinity with oil or hydrocarbons than water.

Some of the important sorbents used for pollution control and various industrial

operations are listed herein.


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Table 1.3 Different sorbents used for the removal of pollutants

No Sorbents used References

1 Silica gel/ modified silica gel 52, 53

2 Resins 20, 54, 55

3 Activated alumina and bauxite 56-58

4 Activated charcoal, Activated carbon, Coal ash 11, 26, 30, 35, 3,

43, 50, 59, 60

5 Activated and novel phosphate 61, 62

6 Saw dust/ Sand and Soil 63-65

7 Natural and synthetic zeolites 66-74

8 Slag 75

9 Pearl millet husk/ Modified peanut husk/ Oak dust 76-78

10 Fly ash/ Shale oil ash/ Fuel oil fly ash 79-81

11 Thermo sensitive gel or polymer 60, 82

12 Kyanite / Perlite / Pyrite / Synthetic iron sulphides 83-85

13 Bagasse/ Bagasse fly ash/modified bagasse fly ash 86-101

14 Modified coir fibres / Coir pith carbon 102-104

15 Red mud / Acid activated red mud 105, 106

16 Modified rice straw / Rice husk ash 107, 108

17 Hen feathers/ fungus/ Silk worm pupa 109-112

18 Tendu leaf/ Papaya wood / Neem leaf 113-115

19 Conventional and non conventional low cost

adsorbents

116, 117

20 Ca - alginate bead 118, 119

21 Iron – based nano adsorbent 120

22 Fly ash and impregnated fly ash 121

23 Industrial wastes 122-124

24 Clays 125-127

25 Natural sorbent/Olive cake/Tea waste 128-131

26 Biomass/bioadsorbents-biosorption 132-135, 22

27 Bentonite/Modified bentonite 137-146

28 Weather Basalt Andesite product 147,148

29 Chitosan, Chitin and its derivatives 149-152

30 Silk cotton hull 153

31 Rubber seed coat 154

32 Agricultural solid wastes 102


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ELEMENTAL POLLUTANTS

Elements that occur at very low levels of a few parts per million or less in a

system are known as “Trace elements”. Some of these elements are believed to be

essential for the growth and development of organism, are recognized as nutrients

required for animal and plant life. Many of these are essential at low levels, but

toxic at higher levels. Natural water normally contain considerable mineral content,

in particular cases levels of harmful inorganic components may be significant quite

independent of any man-made pollutants. Among the various elements heavy

metals have been recognized as most deleterious to aquatic ecosystem and human

health. These heavy metals are introduced into wastewater from many industries

and show significant toxic effects and thus considered as pollutants [155]. The

common heavy metals present in wastewater are chromium, lead, cadmium,

arsenic, copper, iron, manganese, vanadium, nickel, mercury, cobalt, molybdenum,

bismuth etc. The most toxic metals are cadmium, lead, mercury, beryllium and

arsenic, where as several others are also exceedingly harmful. It is essential that

every trace of such metals be removed. Thus it is an important point to notice that

whether a particular element is beneficial or detrimental. Some of these elements,

such as lead or mercury, have such toxicological and environmental significance.

The presence of heavy metal in water also cause disease like ‘Minamata epidemic’

and ‘Itai Itai’ due to Mercury and Cadmium respectively.

Some of the metalloids, elements on the borderline between metals and non-

metals, are significant water pollutants. Arsenic, selenium and antimony are of

particular interest. Inorganic chemical manufacture has the potential to contaminate

water with trace elements. It may be added that most wastewaters contain heavy

metals in higher concentration than permissible limits, introduced into surface

water be evidence for significant toxic effects and therefore needs to be removed.

Different sorbents used for the removal of various metals are listed in Table 1.4.


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Table 1.4 Different sorbents used for the removal of heavy metals

Heavy

Metals Sorbents Reference

Pb+2

Sugar cane Bagasse/ Bentonite 88, 137, 156

Kaolinite, Bauxite, Aluminium oxide, Fly ash 157

Natural and activated phosphate/ Calcined phosphate 62, 158

Granular activated carbon/ Activated carbon fibers 159, 160

Palygorskite clay/ Pyrite and synthetic iron sulphide 125, 85

Bagasse fly ash/ Saw dust and modified peanut husk 91, 77

Low cost biopolymer/ Olive cake/ Natural sorbent 161, 130, 129

Al2O3 supported iron oxide/ Tea waste/ Fungus 162, 131, 109

Cancrinite zeolite/ Coal fly ash/ Brown algae 163, 164, 134

Cr+3

/Cr+6

Resins-1200H 1500H and IRN97H 20

Bagasse fly ash 91

Granular activated Carbon/ activated carbon fibre 159, 160

Functionalized silica/ Modified oak saw dust 165, 76

Saw dust and modified peanut husk/ Kyanite 77, 83

Kaolinite, Bauxite, Aluminium oxide, Fly ash 157

Weathered basalt andesite products/ Biomass 148, 166

Brown algae 134

Cd+2

Sugar cane bagasse/ Coal fly ash/ Bagasse fly ash 86, 164, 89

Kaolinite, Bauxite, Aluminium oxide/ Resin 157, 55

Activated carbon fibers/ Functionalized silica 160, 165

Pyrite and synthetic iron sulphide/ Fungus 85, 109

Low cost biopolymer/ Olive cake, Fly ash 161, 130

Papaya wood/ Chitin/ Brown algae 114, 167, 134

Alginate-chitosan hydrogel/ Rice husk 168, 93

As+3

/As+4

Ni, Cu and Co doped goethite sample 169

Coal fly ashes 170

Hg+2

Industrial minerals/ Furfural adsorbent/ Brown algae 171, 172, 134

Chitosan and its derivatives/ Thiol-grafted chitosan 173, 174

Cu+2

Sugar cane bagasse/ bagasse fly ash 87, 90

Modified oak husk saw dust/ Sawdust and Peanut

husk 76, 77

Papaya wood/ Tea waste/ Biomass 114, 131, 132

Alginate-chitosan hydrogel/ Chitosan 168, 152

Kaolinite, Bauxite, Aluminium oxide 157

Functionalised silica/ Low cost biopolymer 165, 161

Cancrinite zeolite/ Natural Zeolites/ Resin 163, 66, 55

Calcined phosphate/ Coal conversion 158, 60

Biosorption/Activated Carbon/ Natural Zeolites 134, 159, 66

Pyrite and synthetic iron sulphide/ Kyanite 85, 83

Coal fly ash/ Brown algae/ Synthetic zeolite 164, 134, 175


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Heavy

Metals Sorbents Reference

Zn+2

Bentonite/ Calcinated phosphate/ Kyanite 137, 159, 83

Kyanite, Fly ash/ Synthetic nanocrystalline kaganite 83, 120

Zeolite (ETS-10 & ETAS-10)/ Papaya wood/ Resin 175, 114, 55

Modified coir fibers/ Natural sorbents/ Rice husk 176, 129, 93

Cancrinite/ Natural zeolite 163, 66, 69

Bagasse fly ash/ Coal fly ash/ Brown algae 92, 164, 134

Mn+2

Zeolite (ETS-10 & ETAS-10)/ Natural zeolite 175, 66

Coal fly ash/ Fly ash 164, 177

Ni+2

Functionalized silica/ Modified oak saw dust 165, 76

Coal conversion/Kyanite/ Fungus 60, 83, 109

Poly(ethyleneterphthalate)-g-itaconic acid / Acrylamide

fiber 178

Modified coir fibers/ Cancrinite 176, 163

Bagasse fly ash and rise husk ash/ Resin 89, 93, 55

Co+2

Functionalized silica/ Natural Zeolite 165, 66

Zeolite (ETS-10 & ETAS-10)/ Cancrinite 175, 163

Poly(ethyleneterphthalate)-g-itaconic acid / Acrylamide

fiber 178

Natural sorbents/Alginate-chitosan hydrogel 129, 168

Granular activated carbon 159

ORGANIC POLLUTANTS

Organic pollutants include dyes, phenols, detergents, pesticides, aromatic

hydrocarbons, polychlorinated biphenyls and other organic chemicals. These

organic compounds enter into the water streams and undergo degradation and

putrefaction by bacterial activity. They consume dissolved oxygen and cause

marked decrease in its content. The decrease in dissolved oxygen content is an

indication of water pollution, generally caused by organic chemicals. The most

common organic pollutants are discussed in brief here.

DYES

Dyes are visual water pollutants which are generally present in the effluents

of textile, leather, food processing, dyeing, cosmetics, paper and dye manufacturing

industries. They are synthetic aromatic compounds which are embodied with


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various functional groups. The coloured dye effluents are generally considered to

be highly toxic to the aquatic biota and affect the symbiotic process by disturbing

the natural equilibrium through reducing photosynthetic activity due to the

colouration of the water in streams. Dyes are considered obnoxious type of

pollutants because they impart color to water which is not acceptable due to

aesthetic consideration and adversely affect life due to toxic effects. The

nonbiodegradable, toxic and inhibitory nature of the spent dye bath has

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

dyes are reported to cause allergy, dermatitis, skin irritation, cancer and mutation in

humans. Thus, the removal of dyes from effluents is important before they are

mixed up with unpolluted natural water bodies. Sorbents used for the removal of

dyes are listed in Table1.5.

PHENOLS

Phenol and its derivatives belong to a group of common environmental

contaminants and basic structural unit for variety of synthetic organic compounds.

The wastewater originating from industries like chemical plants, pesticides, dyes,

pulp and paper, resin manufacturing, gas and coke manufacturing, tanning, textile,

plastics, rubber, pharmaceutical and petroleum contain different types of phenols.

Wastewater also contains phenols, formed as a result of decay of vegetation. They

impart bad taste and odour to water and are also toxic even at low concentrations.

Phenolic compounds are a class of polluting chemicals, easily absorbed by animals

and humans through the skin and mucous membranes. Their toxicity affects

directly a great variety of organs and tissues, primarily lungs, liver, kidneys and

genitourinary system. Human consumption of phenol-contaminated water can

cause severe pain leading to damage of the capillaries ultimately causing death. The

removal of phenols from effluents is considered essential before they are

discharged due to their toxicity, bad taste and odour imparted to water. The

estimation and detoxification of phenols from wastewaters is, therefore of great

importance. The sorbents used for the removal of phenols are listed in Table 1.6.


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Table 1.5 Different sorbents used for the removal of dyes

Dyes Sorbents Reference

Reactive dyes

Activated carbon and bottom ash 179, 73

Metal hydroxide sludge/ Resins 180, 54

Zeolite/ Modified zeolite 74, 73

Cellulose/ Mixture of carbon and fly ash 181, 182

Coke waste/ Mesoporous materials 183, 184

Chemically crosslinked chitosan 185

Basic dyes

β –Cyclodextrin polymer, Coir pith carbon 186, 187

Hen feathers/ Calcium alginate bead 110, 111, 119

Fly ash/ Bagasse fly ash and activated carbon 188, 95-98

Bagasse fly ash/ Neem leaf powder 94, 101, 115

Fuel oil fly ash/Perlite/ Bagasse 81, 84, 86

Carbonaceous sorbent/activated sludge biomass 78, 133

Acid activated red mud/ Sugar industries mud 106, 189

Green algae/ Sand/ Low cost adsorbents 190, 191, 116

Industrial waste, Waste carbon slurry and blast

furnace slug 124

Coal fly ash/ Silk worm pupa 60, 112

Cross linked polysaccharide/ Bentonite 192, 141

Acid dyes

β –Cyclodextrin polymer/ Activated carbon 186, 95

Bagasse fly ash/ Mixture of carbon and fly ash 94, 182

Hen feathers/ Activated red mud 110, 106

Bentonite / Organo Bentonite 138, 140, 145

Cross linked polysaccharide 192

Direct dyes β – Cyclodextrin polymer, Bio-sludge 186, 194

Disperse dyes β–Cyclodextrin polymer, Cross linked

polysaccharide 186, 192


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Table 1.6 Different sorbents used for the removal of phenols

Phenols Sorbents Reference

Phenol

Palm seed activated carbon/ Biomass 3, 10

Various activated Carbon 11, 26, 35

Zeolites/ Activated Carbon 71, 72, 100

Polymeric adsorbent/ Coir pith carbon 82, 104

Bagasse fly ash 99, 100, 205

Red mud an aluminum industry waste 105

Rice husk/ Immobilized biomass 108, 136

Tendu leaf/ Montmorillonite clay 113, 126

Fly ash and impregnated fly ash 121

Bentonite/Peat, Fly ash, Bentonite 142, 143

Hexadecyl trimethyl ammonium-bentonite 146

Rubber seed coat/ Activated carbon fibers 154, 199

Corn grain-based activated carbons 195

Chitosan-Calcium alginate beads (CS/Ca) 196

cross-linked algae, organobentonites 198, 212

Paper mill sludges/ Kaolinite clay/ Chitosan 200, 201, 208

Nitrophenols

Silver nanostructures/ Paper mill sludges 6, 9, 200


Natural Zeolite/ Polymeric adsorbent 25, 82

Bagasse fly ash/ Alginate gel beads 99, 118 Palygorskite and surfactant modified (TMAB,

HDTMAB, DDMAB and SDS) palygorskite 197

Kaolinite clay/ Activated carbon cloth 201, 203

Activated carbon and Resins 209, 202, 204

Carbon obtained from fertilizer waste 206

Resins and natural adsorbents 207

Functional chitosan 208

Organopalygorskites/ Organobentonites 210, 212

Chlorophenols

Various adsorbents/ Paper mill sludges 8, 9, 200


Soil/ Zeolites/ Activated carbon 65, 72

Polymeric adsorbent/ Coir pith carbon 82, 104

Fuel oil fly ash 81

Activated Carbon Fibers 199

Red mud an aluminum industry waste 105

Rice husk/ Industrial waste 108, 122, 123

Montmorillonite clay 126

Organophilic bentonite 139

Chitosan/ Chitosan-alginate 149, 151

Chitosan-Calcium alginate beads (CS/Ca) 196

Functional chitosan 208

Bituminous shale/ Organobentonites 211, 212


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PROBLEM, AIM AND OBJECTIVE OF PRESENT WORK

The literature survey has revealed that recently many methods have been

used for removing pollutants from the wastewater. Application of traditional

treatment techniques needs enormous cost and continuous input of chemicals,

which becomes impracticable and uneconomical and causes further environment

damage. Hence, easy effective, economical and ecofriendly techniques are required

for fine tuning of effluent/wastewater treatment. Among all the techniques, sorption

/ adsorption is found to be the most widely used procedure because of its versatility

and easy operation. The activated carbons are the most preferred sorbents in

wastewater treatment plants, where sorption methodology is adopted. The activated

carbons are costly material and therefore, regeneration of spent carbon is resorted

too. However, chemical regeneration may create additional pollution and

regenerated carbon also exhibits lower sorption capacity. Attempts have therefore

been made to utilize low cost natural materials or industrial wastes as alternative

sorbents of activated carbons. The search for a low cost and easily available sorbent

has led to the investigation of materials of agricultural and biological origin along

with industrial by products, as sorbent.

There is a growing interest in the preparation of low cost sorbents for

wastewater treatments, so the usage of natural (untreated) and synthesized zeolitic

abundant materials are important for the cost-cutting of the processes. Various

techniques have been investigated for sorption of organic and inorganic pollutants

from water by different fly ashes over the past years. Several research studies had

been reported on the characterization of fly ashes and sorption of organic and

inorganic pollutants using them. None have been recorded on the sorption of

phenol, ortho-chlorophenol and para-nitrophenol using modified bagasse fly ash

(zeolitic bagasse fly ash). Hence, it was decided to embark on this investigation.

Thus, the present study is envisaged to develop low cost zeolitic material using

abundantly available sugar industry solid waste, Bagasse Fly Ash (BFA), which is

facing solid waste disposal problem of sugar industries for the removal of phenolic

pollutants from water. Suitably treated BFA can be effectively and efficiently


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converted into Zeolite by alkaline hydrothermal treatment (CZBFA) and fusion

treatment (FZBFA). It has been successfully converted into zeolitic products and

utilized to study their potential for the removal of phenols from simulated water

system. The results of investigation incorporated in this thesis show that zeolitic

material prepared from BFA remove phenols satisfactorily and can therefore, be

looked forward as low cost alternative as compared to activated carbons. The aim

behind this study is to minimize the cost of wastewater treatment so that the small

scale industries in developing countries could get advantage of it. This would

provide basic probability of obtaining a successful treatment method of industrial

effluents containing phenol and its analogues.

The scope of this study was to:

Characterize the zeolitic nature of CZBFA and FZBFA.

Investigate the effectiveness of the BFA, CZBFA and FZBFA to sorb

phenol, ortho-chlorophenol and para-nitrophenol from aqueous systems

(simulated wastewater) during batch and column treatment processes.

Investigate the effects of pH, contact time, initial phenol concentration,

sorbent dosage and temperature during batch experiments.

Determine the applicability of Freundlich, Langmuir, Temkin, Dubinin

Reduskwich isotherms

Determine the sorption kinetics of the various phenolic compounds onto

BFA, CZBFA and FZBFA.

Examine the mechanism of phenol sorption on sorbents.

Desorption studies.

Approach to estimate design the parameters characterizing the performance

of the batch and the column tests.

Determine the breakthrough point for a column operated under different

sobent bed in order to evaluate its performance.

chapter-1 introduction and literature...

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