Confiscation of aromatic compounds. Microwave synthesized electrolyte treated and Si/Al enhanced mesoporous zeolitic materials originated from sugar industry detritus

CONTENTS

1.INTRODUCTION AND LITERATURE REVIEW
General Overview
Literature Review
Aim and Objective of the present work

2.MATERIALS AND METHODS
Materials and Methods
Synthesis of Zeolitic materials
Physical Characteristics of Sorbents
Sorption Studies

3.SPECTRAL ANALYSIS
Instrumentation and Methods
X-ray Fluorescence Spectroscopy
Fourier Transform Infrared Spectroscopy
Powder X-ray Diffraction
Scanning Electron Microscopy
Results and Interpretation

4.THERMAL ANALYSIS
Experimental
Results and Discussion
Thermal stability
Evaluation of Kinetic Parameters

5.RESULTS AND DISCUSSION
Physical Characteristics of Sorbents
Sorption Studies
Optimization of Operational Variables
Modeling of Sorption Isotherms
Sorption Dynamics

6. COLUMN DYNAMICS AND APPLICATIONS

FINAL CONCLUSIONS

REFERENCES

CONFERENCES/SEMINARS AND PUBLICATIONS

DECLARATION

This is to certify that the work incorporated in the thesis entitled “CONFISCATION OF AROMATIC COMPOUNDS BY MICROWAVE SYNTHESIZED ELECTROLYTE TREATED AND Si/Al ENHANCED MESOPOROUS ZEOLITIC MATERIALS ORIGINATED FROM SUGAR INDUSTRY DETRITUS” submitted by Mr. AMARE A. ABEBE (Registration No: 3203 & Date: 26/10/2013) comprises the results of the original investigations carried out under the supervision of Prof. Bhavna A. Shah. It has not been submitted to any other University/ Institute for any degree or diploma.

Place: Surat

Date: 28th June, 2016

Prof. Bhavna A. Shah

(Research Guide)

Prof. K. C. Patel

(Head of Department)

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ACKNOWLEDGMENTS

Even if one’s deep sense of feeing and regards can often less to reveal by words, I ta.ke this opportunity to express my gratitude to a.CC those who motivated, encoura.ged and hebped me in the course ofstudy. First and foremost, I praise ACmighty God for his a.Cways being with me, without his gra.cious bbessings, I woubd never have been where I am now.

I feel myself very lucky and grateful to work under supervision of Dr. Bhavna A. Shah, Professor, Department of Chemistry, Veer Narmad South Gujarat University, Surat. She ha.s been a constant source of motivation during the course of my research with her kind support, guidance and encoura.gement throughout the course of study a.Cong with her va.st knowbedge, skdb, vision, ethics.

I wish to express my deep and sincere thanks to Dr. Ajay V. Shah, Head, Science and Humanities Department, BVPIT, Vidyabharti Trust, Umrakh, Bardoi for his inva.lna.bCe unconditiona.C heCp in getting Ba.ga.sse fCy a.sh from sugar mdQ Bardoi. Without his guidance and suggestion, this work wouCd have been indeed very difficuCt for me to confront it. His nice guidance, fea.sibCe aid and va.Cua.bCe suggestions have great va.Cue through out whoCe research work.

I express my sincere thanks to Dr. K C. PateC, Professor, Head of Chemistry Department and Dean of facuCty of Science, Veer Narmad South Gujarat University, Surat for providing the necessary Caboratory facdities. I wouCd ike to mention my thanks to a.CC tea.ching and non- tea.ching staff members of the Department for their kind co-operation during the course of my research.

I have great appreciation and a.cknowCedgment to Debre Berhan University who gave me this opportunity to learn my higher degree program in India. I wouCd ike to a.cknowCedge Ministry of Education of Ethiopia for a.CCowing me to do my Ph.D in chemistry through (ICCR) Indian Councd for CuCtura.C ReCation andpaying my sa.Cary.

I would like to express my deepest gratitude for Indian CounciC for Cultural Relation (ICCR) main office in New Delhi and the regional office in Gujarat for a.ccepting me a.s one of African scheme research scholar fellow an availing me necessities as per rule, Ahmeda.ba.d, Gujarat India,

I wish to express my heartfelt thanks to my research collea.gu.es Dr, Ritesh Tailor, Dr, Harendra Patel, Dr, Piyush y, Jadav, Dr, Chirag Mistry, Mr, Alok Navik, Dr, Pratima Surti, Dr, Pravin Patel, Miss, Darshini Pandya, Mr, Hiren Patel, Mr, Alpesh Patel and Miss, Maryam Bagia for their precious idea, constant inspiration, and mora.1 support which contributed to the current shape of my work,

A special note of thanks to CSMCRI (Central Salt and Marine Chemicals Research Institute) Bhavnagar,Gujarat and (SICART) Sophisticated Instrumentation Centre for Applied Research, Anand, Gujarat, IITROORKE for ana.lysis of my samples.

Cheerful special thanks to my friends and other members of the department for being so supportive and hepful in every possible way,

Above all, I would like to give hearty thanks to my families and cousin for their care and mora.1 support and to my brother and sisters for continuous love and support which strengthen me for pursuing higher degree program.

A specia.1 thanks to my wife Miss, Etewa yeshaneh and my lovely daughter Eden Amare for understanding me and her mora.1 support in entire study program.

Amare A. Abebe

Preface

Environmental pollution is the result of natural and human activities disturbances of the ecological equilibrium which cause physical, chemical or biological adverse influences on the environment. Environmental pollution, in general, and water pollution, in particular, is a subject of growing concern to the scientific community worldwide. There has been increasing concern about the release of organic and inorganic compounds to the environment as a result of various industrial, agricultural activities. Currently aromatic organic compound in waste water attracted the attention of researchers since it poses toxicity at trace level which can affect environment and human life.

The aromatic compounds, particularly phenol, aniline, and their derivatives (chloroanilines, nitroanilines, and chlorophenols), nitrobenzene are largely used in industrial productions of pigments, pharmaceutical, dyes, and pesticides; as reagents; synthesis intermediates etc. and can be found at high concentrations in surface water contaminated by industrial wastes. Their concentration in water and soils is continuously increasing, due to their low degradability and large diffusion. Moreover the nitro aromatic compounds due to the presence of a nitro group in the aromatic ring, for example paranitroaniline is resistant to chemical and biological oxidation degradation, and the anaerobic degradation produces nitroso and hydroxylamines compounds which are secondary pollutants. These hazardous aromatic compounds have great impact on living things and environment as trace level such as mutagenic, carcinogenic, hem toxicity, splentoxicity and nephrotoxicity etc.

Due to these reasons remedies of water pollution by aromatic compounds has attracted much attention in recent years, More stringent limits for these compounds with acceptable environmental levels are established gradually in many countries. In some developing countries how to deal with large volume of wastewater containing toxic aromatic compounds is a pressing environmental problem. For instance the maximum allowed level in waste water aniline 2 mg/L, nitrobenzene 1 mg/L and 3mg/L para nitro aniline.

To alleviate the problem and achieve the allowed level or eliminate totally from the waste water various physical, chemical, biological methods are used. Among these methods adsorption is still the best waste water treatment method due to its universal nature, inexpensiveness and ease of operation. Hence powdered activated carbon (PAC) and granular activated carbon (GAC) are both employed today throughout the world in the water and wastewater treatment industry. However the cost of activated carbon and its regeneration of the sorbent are very high. So, researchers in science and engineering have increased interest in finding low-cost adsorbents such as industrial sludge waste, biomass, husk, slag, carbon slurry, bagasse fly ash (BFA), etc. to remove inorganic and organic pollutants from wastewater. There are many researcher results which were done on BFA for the removal of pesticide, dye, phenol etc but during survey of literature no research work is done on the removal of aniline, nitrobenzene and para nitroaniline using BFA and its derived zeolitic materials.

Zeolites are aluminosilicates crystalline materials which contain pores and cavities of molecular dimensions. Many occur as natural minerals, but it is the synthetic varieties which are among the most widely used sorbents.

The aim of this research was to synthesize and study batch properties of zeolite synthesized from Bagasse fly ash and its derived zeolitic material. To achieve this, a study was carried out with the following objectives:

i. To synthesize zeolites from Bagasse fly ash solution via microwave assisted hydrothermal synthesis process.
ii. To study the effect of adding electrolyte and electrolyte with sodium silicate to BFA solution towards the development of zeolitic material.
iii. To investigate the effects of adding sodium hydroxide and sodium hydroxide plus sodium meta silicate for activation of BFA
iv. To examine the structural characteristic of the synthetic zeolite produced (i.e. morphology, physico-chemical and phases identification) via XRF, SEM, FTIR, PXRD, TGA, BET and BJH
v. To evaluate the sorption capacity of the synthesized zeolitic material using aqueous solution of aromatic compounds

The thesis is divided into six chapters

The aim of this work is to get the best using the waste of sugar industry (BFA) by transforming into potential cost effective adsorbents (EMZBFA-Ba and EMZBFA-30-Ba) and their utilization for the elimination of aromatic compound (Aniline, Nitrobenzene and para nitro aniline) from aqueous solution.

Chapter-1: Introduction and Literature Review

This chapter includes the survey of environmental pollution specifically water pollution by industries effluent which are discharged from manufacturing of aromatic organic compounds using permissible limits of organic pollutants’ from environmental protection agency and hazardous chemical index. Literature studies on the types of pollutants, their effect on living things, and their routes to the water system. Current references along with the previous studies on the available technologies as well as adsorbents for the removal of pollutants from water and wastewater have been reported. It contains brief objective and scope of the present work.

Chapter-2: Materials and Methods

This chapter consists of the materials and experimental methods used during the whole research work. The BFA is successfully converted into zeolites by alkali liquids activation which are alkali hydroxide only and mixture of alkali hydroxide and sodium meta silicate with electrolyte media with implementation of microwave assisted treatment

Chapter-3: Instrumental Analysis

This chapter deals with the characterization of the sorbents BFA, EMZBFA-Ba and EMZBFA-30-Ba by different instrumental techniques like XRF, PXRD, FTIR, SEM, TGA, BET and BJH as well as classical methods have been employed.

Chapter-4: Thermal Analysis

The chapter describes the thermal analysis of the sorbents. The Coats and Redfern method was used to evaluate the kinetic parameters from Thermo gravimetric curves.

Chapter-5: Results and Discussion

The native BFA and synthesized zeolitic materials were used as sorbents for uptake of aromatic compound. The various operating variables, viz., solution pH, contact time, initial sorbate concentration, adsorbent dose and temperature. The sorption isotherms and kinetics studies were involved in details. The thermodynamic parameters are also carried out using temperature studies to know the nature of sorption.

Competitive confiscation of p-nitroaniline and nitrobenzene was performed.

Chapter-6: Column dynamics

This chapter describes the utilization of BFA and synthesized zeolitic materials as a fixed bed column for the removal of aromatic organic pollutants as pilot study for industrial application. It includes breakthrough curves of aromatic organic pollutants removal to evaluate the fixed bed column capacities of the sorbents. It also includes the desorption studies of sorbed aromatic organic pollutants with different effluents.

Conclusion

The results and discussion is followed by the concluding remarks derived from this research work.

1. General Overview of Environmental pollution

Environmental pollution is the result of different accidental events, emission of certain environmental pollutants owing to the activity of nature itself or owing to human activities. The term environmental pollution refers to any cause of physical, chemical or biological disturbance of the ecological equilibrium in the environment causing adverse effects. Natural pollutants stem from activities of nature itself and they contain certain sediments in air (dust) and surface waters, dissolved minerals (sometimes toxic metals) in ground and surface water with trace elements in air from volcanic activities. Anthropogenic pollutants are emitted as a result of human activity. Their main types are as follows: industrial, municipal/domestic, agricultural, institutional and commercial activities. On the other hand, the anthropogenic pollutants can be divided into point and nonpoint sources. Nonpoint sources (e.g., roads, streets, parking loats, farm fields, construction sites, etc.) are especially difficult to monitor, regulate and to treat. Natural and anthropogenic pollutants emitted from a given sources are defined as primary pollutants. A number of primary pollutants can undergo changes owing to reactions with other pollutants or with some components of the environment. In this way, the resulting new compounds formed, which can often increase toxicity; they are known as secondary pollutants. Both primary and secondary pollutants occur in all the environmental media, i.e., atmosphere, hydrosphere and geosphere 1.

Before 19th century with no much industrial revolution, people lived more in harmony with their immediate environment. While industrialization has been spread around the globe along with problem of pollution has been increased. Once earth's population was much smaller, no one believed pollution would ever cause such a serious problem. It was formerly popularly believed that the oceans were far too big to pollute but because of increase in population growth, there is increasing demand for fuel, pesticides, fertilizers, industrial chemicals, pharmaceuticals, processed food, textiles and similar indispensable products, which are associated with society’s desire to enhance the quality of life. As a matter of fact industrialization offering commodities and services to the public to meet such demands which has been resulted in waste products, which are released into the environment through wastewaters, gaseous emissions, and solid residues, leading to environmental pollution and a deterioration of natural resources. It has attained the stage that the earth’s in-built ecosystem could no longer dilute, decompose and recycle the waste products 2. So at this stage knowing the source of environmental pollution and taking waste treatment measure is mandatory.

Sources of Water Pollution

There are many types of water pollution depending on the sources the pollutants originate from which is represented in Figure 1.1 and the types of water pollution are as follows:

-Nutrient Pollution: Sewage water, waste water that contains high level of nutrients enters into water bodies. Nutrients in water encourage the growth of algae and weed in the water. This is known as eutrophication. This makes the water unfit for consumption and clog filters. Algal blooms in the water consume all the oxygen in the water, leading to suffocation for other water organisms.
-Surface Water Pollution: Surface water includes rivers, lakes, oceans, streams, lagoons. Surface run-off substances that are hazardous dissolved and mixed with water polluting the surface water. These run-off substances can be from any source like factories, domestic, sewage, agriculture etc.
-Oxygen Depletion: Increase in the content of biodegradable matter in the water encourages the growth of microorganisms which end up using most of the oxygen. This results in oxygen depletion, killing aerobic organisms producing more of toxins like ammonia and sulphides.
-Ground Water Pollution: Chemicals from fertilizers and pesticides applied to the soil are washed off and seep in the ground contaminating the composition of the ground water causing pollution.
-Natural Pollution: Sometimes pollution is caused by microorganisms like bacteria and protozoa, this natural pollution can be lethal for fishes and other water life. Consumption of this water can lead to serious illness to humans.
-Si Suspended Matter: Particulate matter of chemicals and other substances do not dissolve in water easily. These suspended particulate matters settle at the bottom of the water body harming the aquatic life at the floor of the water bodies.
-Chemical Water Pollution: Most of the industrial let-off and chemical fertilizers used in farming end up in the water bodies. These materials are poisonous to most of the aquatic life, can make them infertile and eventually cause death. Water from these sources is obviously unfit for consumption.
-Oil Spillage: Oil tankers and off-shore petroleum refineries cause oil leakage polluting water. Oil spills can cause death of many aquatic organisms and also stick to the bodies and feather which make seabirds unable to fly.
-Domestic Sewage: Domestic sewage is the waste water from households. It also includes sanitary sewage, and it contains a variety of dissolved and suspended particles. Domestic sewage contains disease causing microbes and chemicals contained in washing powders affect the health of all life forms in water.
-Agricultural Run-off: The practices followed in agriculture affect the groundwater quality. Intensive cultivation causes fertilizers and pesticides to seep into the groundwater; this process is known as leaching. Irrigation run-off from agricultural fields causes high nitrate content in ground water.
-Industrial Effluents: Untreated waste water from manufacturing industries contributes to water pollution.
-Thermal Water Pollution: Thermal water pollution is the rise or fall in water temperatures. This change in the temperature of water can be caused due to industries. Some industries use water as cooling agent, the heated water is let-off directly into the natural environment at a higher temperature. Cold water pollution happens when cold water is released into the water bodies. Aquatic organisms like fish are vulnerable to slight changes in the temperature. Heated water decreases oxygen in the water killing fish and other aquatic organisms. Cold water affects eggs and larvae, some invertebrates of the aquatic ecosystem.

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Figure 1.1 sources of water pollution Aromatic pollutants

Aromatic pollutants

The aromatic compounds, particularly phenol, aniline, and their derivatives (chloroanilines, nitroanilines, and chlorophenols), nitrobenzene are largely used in industrial productions of pigments, pharmaceutical, dyes, and pesticides; as a reagent or in synthesis of intermediates etc. and can be found at high concentrations in surface water contaminated by industrial wastes. Their concentration in water and soils is continuously increasing, due to their low degradability and large diffusion [3, 4]. Moreover the nitro aromatic compounds due to the presence of a nitro group in the aromatic ring, for example para-Nitroaniline is resistant to chemical and biological oxidation, degradation, and the anaerobic degradation produces nitroso and hydroxylamines compounds which are secondary pollutants [5, 6]. Further reductive splitting of azo dyes produces aniline and p-phenyl diamine. For example Ponceau SS, Sudan III, and Disperse Yellow 7 are capable of splitting p-phenylenediamine and aniline, while Mordant Orange 1 and Disperse Orange 3 can split only p-phenylenediamine. The structures of the azo dyes are shown below in Figure 1.2 7.

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Figure 1.2 Structural formulae of some of azo dyes reductive splitting

The study was carried out in various wastewater samples for determination of different amines concentration in Canada 8. On account of higher production and manifold applications in different industrial branches, amines are often identified in industrial wastewater and also in municipal sewage. Some examples are listed in Table 1.1 illustrating the appearance of amines in very different concentration ranges in different types of wastewater. Among other examples, the content of benzidines and different types of anilines in industrial wastewater of an azo dye manufacturer and the behavior of these compounds along the treatment path is given in table. The treated effluent was discharged into Lake Ontario, Canada.

Table 1.1 Maximum concentrations of different amines in various wastewaters

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The textile industry is one of the oldest and largest organised sectors in India. With the increased demand for textile products, the textile industry and its wastewaters have increased proportionally. There are over 7000 large-scale textile industries in India located mainly in Gujarat, Maharashtra, Rajasthan and Tamil Nadu states. The textile printing and dyeing industry is a water-intensive industry requiring a large volume of freshwater at various steps of printing and therefore, the volume of wastewater produced is equally large. These industries can generate both inorganic and organic waste mixed with waste water from the production processes, which when discharged into the receiving water bodies can leads to change in both biological and chemical parameters of water 9.

These disposal practices have contaminated the environment and caused adverse effects on the crops, flora, and fauna in many places of India [10, 11]. Such discharge of textile wastewater is of great concern since the discharges are mostly made untreated or partially treated due to poor enforcement of existing laws in the developing world including India 12.

Harmful Effects of Water Pollution and Its Approach of Treatments

Until the middle of the last century, wastewater treatment objectives were mainly concerned with (1) the removal of suspended, colloidal and floatable material, (2) the destruction of biodegradable compounds, and (3) the elimination of pathogenic microorganisms. Since the early 1970s, great strides in analytical techniques have been made allowing for new and more sophisticated instrumentation.

Detection methods have become more sensitive and broader ranges of compounds are now monitored in water bodies. Accordingly, there are a large number of scientific reports documenting the effects of many contaminants and microorganisms present in wastewater on both human health and the environment. While most constituent concentrations are reported in milligrams per liter (mg/L), measurements in micrograms per liter (gg/L) and nanograms per liter (ng/L) are ordinary at present 13.

As new evidence demonstrates the impact of many different pollutants originating from a broad range of industrial activities on human health and on the environment, it becomes critical to know the following when an industrial wastewater is discharged 14:

(1) Constituents of concern in the wastewater;
(2) Impacts of these constituents when the wastewater is dispersed into the environment;
(3) The transformation and long-term fate of these constituents in treatment processes;
(4) Methods that can be used to remove or modify the constituents found in the wastewater; and
(5) Methods for beneficial use or disposal of solids generated by the treatment systems.

Table 1.2 Constituents of waste water treatment and their effects

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The principal constituents that are currently of concern in wastewater treatment, as well as the reason for their importance are summarized in Table 1.2. Priority pollutants, refractory organics and heavy metals deserve special attention for industrial effluents, since many of these constituents are discharged by several manufacturing sectors, and their impact on human health and the environment is well documented 15. Table 1.3 lists the industrial sources for the main aromatic priority pollutants of concern according to the US Environmental Protection Agency (EPA) 16.

Table 1.3 Sources of toxic anthropogenic aromatic pollutants

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Permissible level and Health impacts of Aniline, Nitrobenzene and Para-Nitroaniline

Aniline, nitrobenzene and para-Nitroaniline have great impact on living things and environment at trace level such as mutagenic, carcinogenic, hem toxicity, splentoxicity and nephrotoxicity etc. [17-19].Due to these reasons water pollution by aromatic compounds has attracted much attention in recent years, more and more stringent limits for these compounds with acceptable environmental levels are established gradually in many countries 20. Thus the maximum allowed limit and their health impact of aniline; nitrobenzene and para-Nitroaniline are discussed here in:

Aniline: the maximum allowed level is 2 mg/L (USEPA). A human poison by an unspecified route but experimentally proved that mostly through inhalation and ingestion routes. It has adverse health effects such as reproductive effects, a skin and severe eye irritant and a mild sensitizer. Aniline causes formation of methemoglobin, resulting in prolonged anoxemia and depression of the central nervous system; less acute exposure causes hemolysis of the red blood cells, followed by stimulation of the bone marrow. The liver may be affected with resulting jaundice.

Nitrobenzene: the allowed limit is 1mg/L (USEPA). It is confirmed as carcinogen, poison to human being by an unspecified route and it is experimentally proved that it can poison by subcutaneous and intravenous routes. It will be moderately toxic by ingestion, skin contact and intraperitoneal routes. Human adverse effects by ingestion: general anesthetic, respiratory stimulation, and vascular changes. It has an experimental teratogen and reproductive effects. Mutation data have been reported. An eye and skin irritant can cause cyanosis due to formation of methemoglobin. It is absorbed rapidly through the skin. The vapors are hazardous.

Para-Nitroaniline: the permissible limit is 3 mg/L (USEPA). It is poisonous to human by ingestion, intravenous, and intraperitoneal routes but moderately toxic by intramuscular route. Acute symptoms of exposure are headache, nausea, vomiting, weakness and stupor, cyanosis and methemoglobinemia while its chronic exposure can cause liver damage. 21.

Uses of Aniline, Nitrobenzene and Para-Nitroaniline

Aniline and Para-Nitroaniline: Aromatic amines are organic nitrogen containing compounds that may be considered derivatives of ammonia (NH3) with at least one of the hydrogen atoms replaced by an aryl group. The nitrogen is bound directly to the aromatic ring and so be able to interact with the aromatic p-electron system. The amine can be primary, secondary, or tertiary depending on whether one, two, or three of the protons are replaced by alkyl or aryl groups. The simplest aromatic amine is derived from benzene and is called aniline or benzenamine (C6H5NH2). According to IUPAC nomenclature, the amino (NH2) or modified amino group (NHR, NRR’) is considered a substituting group of the aromatic hydrocarbon. Therefore, these compounds are named as derivatives of benzene, toluene, naphthalene, and others, e.g., N,N- dimethyl aminobenzene, C6H5N(CH3)2. Aniline is generally used as the parent structure for its derivatives unless a carbon atom is attached to the benzene ring or unless a function of higher seniority than amino is present in the molecule. Important derivatives of aniline are named as such, e.g., N methylaniline, p-nitroaniline, chloroaniline

Aromatic amines are widely used as dye intermediates, especially for azo dyes, pigments, and optical brighteners; as intermediates for photographic chemicals, pharmaceuticals, and agricultural chemicals; in polymers via isocyanates for polyurethanes; and as antioxidants. They have been listed as corrosion inhibitors of mild steel in the pickling process 22.

The oldest use of aromatic amines is as intermediates for dyes. Substituted anilines and especially naphthylamines have been precursors of azo dyes since the middle of the 1800s. Even with the replacement of the once predominant anthraquinone dyes with more and more azo dyes derived from aromatic amines, the previous strong demand of aniline in the dye industry has decreased markedly in the United States to less than 4% of its former magnitude. Once over 700 dyes listed in the Colour Index (C. I.) 23 were prepared from aniline and its derivatives; now only a few are produced in commercial quantities. The production and sales volume for the aniline derivatives as a group is generally growing only at the average rate of expansion of the chemical market as a whole. Production of many of them has ceased in united states and the supply is shifted to Japan, Korea, China, and other East Asian countries along with textile and dye production. para-Nitroaniline, with a United States production of 6200 tone in 1981 and an import volume of 630 tone in 1983, is probably the largest in this group. p-Nitroaniline is used mainly in the production of dyes, antioxidants, and pharmaceuticals 24.

Nitrobenzene: The use of nitrobenzene as a processing solvent in specific chemical reactions is minor but important. Most of the (95% or more) nitrobenzene produced is converted to aniline, which has hundreds of downstream products. Lower volume, but nevertheless important, industrial outlets include electrolytic reduction to 4-aminophenol, nitration to give 1,3- dinitrobenzene, chlorination to give 3-chloronitrobenzene, sulfonation to give 3- nitrobenzenesulfonic acid and chlorosulfonation to give 3-nitrobenzenesulfonyl chloride 25.

Technologies Available for the Removal of Aniline, Nitrobenzene and para-Nitroaniline Compounds

Water bodies’ pollution by aromatic compounds has got great attention now a day; strict limits for these pollutants with permissible environmental levels are familiar gradually in many countries. In some developing countries, how to deal with large volume of wastewater containing toxic organic pollutants is a pressing environmental issue. Organic compounds such as p- nitroaniline nitrobenzene and aniline are important intermediates to produce perfumes, synthetic resins, drugs dyes, fuel additives, antioxidants, and pesticides [26-28]. As a result; the aromatic compound containing wastewater has been introduced into water bodies 29.to alleviate the problem and achieve the allowed permissible level or eliminate totally from the waste water various physical, chemical, biological methods are used among these methods, adsorption is still the best waste water treatment method due to its universal nature, inexpensiveness and ease of operation 30. Hence powdered activated carbon (PAC) and granular activated carbon (GAC) are both employed today throughout the world in the water and wastewater treatment industry [31, 32]. However the cost of activated carbon and its regeneration of the sorbent are very high. So, researchers in science and engineering have increased interest in finding low-cost adsorbents such as industrial sludge waste, biomass, husk, slag, carbon slurry, bagasse fly ash (BFA), etc. to remove inorganic and organic pollutants from wastewater [33,34]. There are many researcher’s results which were carried out on BFA for the removal of phenol [35-39], dye [40,41], pesticide 42 etc but during survey of literature no research work is done on the removal of aniline, nitrobenzene and para nitroaniline using BFA and its derived zeolitic materials.

Chemical Methods

Chemical treatment is a widely used process for the destruction or separation of hazardous constituents in wastewater. This can be done by neutralization of acidic or alkaline wastewater until a suitable pH is obtained. Precipitation/Coagulation/Flocculation is used for the removal of heavy metals. Precipitation refers to the formation of a solid phase, coagulation is where the containment is trapped by the formation of a precipitate, and flocculation is the agglomeration of a coagulating chemical.

Oxidation-Reduction or the redox processes are used for converting toxic pollutants to harmless or less toxic materials that are more easily removed. These processes involve the addition of chemical reagents to wastewater, causing changes in the oxidation states of substances both in the reagents and in the wastewater. Ozone is a powerful oxidizing agent that is usually oxygen at temperatures and pressures up to 350°C and 180 atmospheres, respectively, to treat organic wastes. For example aniline was degraded by anodic oxidation in the presence of electrogenerated H2O2, Electro-Fenton and peroxi-coagulation processes. the production of an excess of protons from overall aniline mineralization to CO2 and ammonium ion as follows 43:

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Biological Treatment Process

Biological treatment has been very successful in the removal of organic pollutants and colloidal organics from wastewater. Activated sludge, biological filters, aerated lagoons, oxidation ponds, and aerobic fermentation are some of the methods available for wastewater biodegradation. In removal of toxic waste, more care is needed since the bacteria are prone to destruction from shock loading or increase in toxic material fed without allowing time for the population to grow large enough to deal with it. Biodegradation occurs because bacteria are able to metabolize the organic matter via enzyme systems to yield carbon dioxide, water, and energy. The energy is used for synthesis, motility, and respiration. With simple dissolved matter, it is taken into the cell and oxidized, but with more complex inorganics, enzymes are secreted extracellularly to hydrolyze the proteins and fats into a soluble form which can then be taken into the cell and oxidized. Hence the more complex matter takes longer time to process. Some organic compounds are "refractory," they cannot be oxidized while others are toxic to the bacteria at high concentrations.

The purpose of biodegradation is to convert the waste into the end for example degradation of azo dyes, In anaerobic azo dye reduction, the reductive cleavage of azo linkage, is the first stage in the complete anaerobic-aerobic degradation of azo dyes, resulting in aromatic amine accumulation. Aromatic amines, which are formed during anaerobic treatment, are generally colorless and hazardous; therefore, a convenient treatment is required. Though mineralization of the aromatic amines under aerobic conditions is more common, it was reported that a few aromatic amines that are characterized by the presence of hydroxyl and carboxyl groups can be mineralized under anaerobic conditions [44, 45]. As a result, combined anaerobic and aerobic conditions are essential for the complete biodegradation of colored waste waters 46. The general azodyes degradation scheme is shown below in Figure 1.3.

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Figure 1.3 General overview of the fate of azo dyes and aromatic amines during anaerobicaerobic treatment

Physical Methods

There are several methods used for separating pollutants from wastewater using: activated carbon, steam stripping, evaporation, reverse osmosis, and solvent extraction techinques. The chemical and physical characteristics of the pollutant are important in the selection of the physical removal method. Steam stripping is effective for substances that have an appreciable vapor pressure at the boiling point of water, whereas evaporation is effective for those chemicals that will not volatilize. Soluble, small organic molecules are adsorbed by activated carbon; large ions are separated by reverse osmosis.

Activated Carbon Adsorption--Here the inorganic and organic chemicals are adsorbed onto activated carbon. Usually hydrophobic chemicals are more likely to be removed. The degree of adsorption is linked to the molecular weight, solubility. The smaller the size of the grain, the more surface area is available and so equilibrium is reached quicker with powdered activated carbon compared to the granular form. But then the powdered form needs more pumping to get the wastewater through and hence the costs are increased. There are two principle systems, one is downward flow through the bed (pressure or gravity flow) and the other is upward flow through a packed or expanded bed. Activated carbon adsorption is applicable to the treatment of dilute aqueous wastes, but they should be treated to remove suspended solids, oil, and grease. Temperature and pH are also important for the different compounds to be treated.

Solvent extraction is a process whereby a dissolved or adsorbed substance is transferred from a liquid or solid phase to a solvent that preferentially dissolves that substance. For the process to be effective the extracting solvent must be immiscible in the liquid and differ in density so that gravity separation is possible and there is minimal contamination of the raffinate (extract) with the solvent. The hydrophobic solutes are more likely to be extracted. Solvent extraction can be performed as a batch process, or by the contact of the solvent with the feed in staged or continuous equipment 47. Disadvantages of solvent extraction are costly, hazardous solvents and environmental pollution.

Adsorption Process

Adsorption science has a very long history, and its first practical adoptions were noted in ancient times. The current adsorption theory and relevant applications initiated by Langmuir’s fundamental work have been developed extensively during the last 80 years. Presently, they comprise very advanced approaches that include a wide spectrum of modern surface chemistry. The autonomous existence of adsorption science is due to two unquestionable facts:

- the enormous complexity that is inherent to adsorption phenomena at various interfaces, and
- the widespread, general occurrence and importance of adsorption and related domains in nature, including everyday life’s products, industrial and environmental applications.

The present status of adsorption has been illustrated by a wide range of theoretical descriptions as well as by several practical examples, including industrial and environmental tasks. The basic definitions of adsorption-related terminologies are given in the following to clarify and standardize these widely used terms in this field.

- Adsorption: the adhesion of molecules (as of gases, solutes, or liquids) to the surfaces of solid bodies or liquids with which they are in contact. Whereas
- Absorption: the absorbing of molecules (as of gases, solutes, or liquids) into the solid bodies or liquids with which they are in contact. So far
- Sorption: Formation from adsorption and absorption so adsorbent: usually solid substance that adsorbs another substance on its surface.
- Sorbent: A usually solid substance that adsorbs and absorbs another substance
- Sorbate: Molecules (as of gases, solutes, or liquids) that are adsorbed on sorbent surfaces.

The term sorption together with the terms ‘sorbent’ and ‘sorbate’ used to denote both adsorption and absorption, when both occur simultaneously and cannot be distinguished [48,49]. The difference between adsorption and sorption is illustrated further in Figure 1.4 and 1.5.

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Figure 1.4 Differences between Adsorption and Absorption

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Figure 1.5 Sorption: Adsorption and Absorption

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 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. 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 wastewater. Dissolved species may participate directly in air-water exchange while sorbed species may settle with solids. Figure 1.6 illustrates a brief sorption process for a general aromatic organic matter 50.

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Figure 1.6 Illustration of sorbed species behaves differently from dissolved molecules of the same substance

In aqueous solution, three interactions compete when considering physical adsorption: (1) adsorbate-water interactions, (2) adsorbate-surface interactions, and (3) water-surface interactions. The extent of adsorption is determined by the strength of adsorbate-surface interactions as compared to the adsorbate-water and water-surface interactions. Adsorbate-surface interactions are determined by surface chemistry, and adsorbate-water are related to the solubility of the adsorbate. Water-surface interactions are determined by the surface chemistry, for example, a graphitic surface is hydrophobic and oxygen containing functional groups are hydrophilic. For chemisorption, the primary factor controlling the extent of reaction is the type of reaction that occurs on the surface. In either case, it is important to provide enough surface area for adsorption 51.

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 a fixed 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 52. Figure 1.7 illustrates the main interactions and forces during physical sorption processes 50.

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Figure 1.7 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) is of great 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 52. Additionally, branched chains are usually more sorbable than straight chains, an increasing length of the chain decreases sorption capacity. 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 53. Aromatic and substituted aromatic compounds are more sorbable than aliphatic hydrocarbons 13. Figure 1.8 illustrates the sorption of an aromatic compound on to a polar surface.

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Figure 1.8 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 54. 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 52.

The enthalpy of chemisorption is very much greater than that for physisorption and typical values are in the range 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 (AG) value. Because, the translational freedom of the sorbate is reduced when it is sorbed, entropy (AS) is negative. Therefore, in order for AG to be negative, AH must be negative and the process is 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 55.

Table 1.4 The bond energies of various mechanisms for the sorption Interaction between sorbent and sorbate Enthalpy (kJ/mol)

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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 the surface of the sorbents, (2) sorption of sorbate molecules on the surface of the sorbents through molecular interactions and (3 and 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 56. 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.

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Figure 1.9 Mechanism of sorption process

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.

Literature Survey

Sorbents Used for Pollution Mitigation of Waste Water

Sorption process is efficient for the removal of pollutants from waste streams. The high adsorption capacities of sorbents are usually related to their high-surface-area, pore volume, and porosity. In addition, the adsorption capabilities of the materials strongly depend on the activation method and the nature of source materials. Many researchers have shown that activated carbon is an effective adsorbent for organic compounds removal. However, its high initial cost and the need for a costly regeneration system make it less economically viable as an adsorbent. Taking these criteria into consideration, the search for a low cost and easily available adsorbent has led many investigators to search more economic and efficient techniques to use agricultural waste origin, along with industrial by-products as adsorbents. Because of their low cost and local availability, natural materials such as chitosan, zeolites, clay, or certain waste products from industrial operations such as fly ash, soil, sludges and oxides etc are classified as low-cost adsorbents. Some of the important sorbents used in pollution alleviation and various industrial operations are discussed below.

Heavy Metals

Heavy metal is a term often used as a group name for metals and semi-metals (metalloids) that have been associated with contamination and/or potential toxicity to animals or plants. It is a rather ill-defined term, but common definitions include those metals and metalloids which have (1) a density of greater than 4-6 g cm-3, (2) an atomic weight greater than sodium, or (3) an atomic number greater than 20 or 21 57. Common elements considered includes Cu, Zn, Co, Ni, Pb, Hg, Cd, Cr, Se, and As, and others sometimes included are V, Ti, Sn, Tl, Sr, Ag, Mn, Mg, Li, Fe, Be, Ba, and Sb. Most heavy metals such as Cu, Zn, Co, Ni, Pb, Hg, and Cd are present at common pH values found in soil solution and natural and waste water as divalent cations. However, some others are present in more than one oxidation state and sometimes as oxyanions. For example, Cr occurs in aqueous systems as both Cr (III), a trivalent cation, and Cr (VI), which exists as the anion CrO42-. As is commonly present as both As (III) (AsO3-3 ) and As (V) (AsO43- ), and Se as both Se (IV) (SeO32- ) and Se (VI) (SeO42- ) 58. So the following sorbets in table 1.5 were used to eliminate the heavy metals from waste streams.

Table 1.5 various types of sorbents used for the removal of heavy metals

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Organic pollutants

Phenols

Phenols are generally considered to be one of the important organic pollutants discharged into the environment causing unpleasant taste and odor of drinking water. The major sources of phenol pollution in the aquatic environment are wastewaters from paint, pesticide, coal conversion, polymeric resin, petroleum and petrochemicals industries. Introducing phenolic compounds into the environment or degradation of these substances means the appearance of phenol and its derivatives in the environment. The chlorination of natural waters for disinfection produces chlorinated phenols. Phenols are considered as priority pollutants since they are harmful to organisms at low concentrations [71, 72]. Some of different types of sorbents used for phenol confiscations is shown in table 1.6

Table 1.6 different types of sorbents used for the removal of phenols

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Pesticides

A pesticide is a chemical substance used for preventing, destroying, repelling or mitigating pests such as an insect; rodent, weed or fungus, as well as microorganism like bacteria and viruses. Pesticides can be broadly classified as insecticides, herbicides, fungicides, rodenticides, and antimicrobials, with many subclasses 86. Despite of their numerous merits, the pesticides generated by the intensification of agriculture, are regarded among the most dangerous contaminants of the environment. They are not only toxic but also mobile and capable of bioaccumulation. On top of this, they can take part in various physical, chemical and biological processes. Many of these pesticides are characterized by a strong persistence which explains their wide presence in the different compartments of the environment as well as some of them is mutagenic, carcinogenic and tumorogenic. Due to these physicochemical characteristics and their extensive use, many of these pesticides end-up in surface and ground water 87. Some of the sorbents used for removal of pesticides are listed in table 1.7.

Table 1.7some of different types of sorbents used for the removal of pesticides

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