CHAPTER - 2 REVIEW OF LITERATURE

2.1. Historical background of ion exchange

Ion exchange materials are widely distributed in nature in the form of clays,

zeolites, humic acids, certain coals and other mineral compounds. Now a days, ion-

exchange materials have been essential for a number of processes pertaining to

analysis, preconcentration and recovery of a number of ionic species from aqueous as

well as from non-aqueous systems. These materials have also been employed for the

preparation of ion-exchange membrane, chemical sensors etc. The ion-exchange

process could be observed when wood cellulose converts bitter water into drinking

water, in the first case and in the second case silicates were used for the improvement

of the taste of water. Presently ion exchange permeates several areas of human

activity and its continually expanding applications bring man nearer to his dream of

comfort. Till the middle of the 18th century the ion exchange process was not known,

until two different researchers had published two papers in the same area. In 1950,

Thomson and Way firstly recognized the ion exchange process in soil for the

exchange of calcium and magnesium ions with potassium and ammonium ions

(Thompson and Roy, 1850: Way, 1850). Later in the same year Eichron proved that

the ion exchange properties of the solid arise form zeolite. Gan in 1905 explored the

ion exchangers for industrial applications. The first application of synthetic zeolite

was reported by Folin and Bell in 1917 for the collection and separation of ammonia

from urine (Folin and Bell, 1917).

Adam and Holms in 1935 developed the synthetic ion exchange resin for the

first time (Adam and Holms, 1935). Organic resins have been used for a long time

due to their high mechanical and chemical stability. However, they decomposed at

elevated temperatures and under strong radiations. Thus, there have been revived

interests in the synthesis of inorganic ion exchanger.

Kraus et al and Amphlet have done excellent work at the initial stages. Later

on, good deal of work has been reported by different workers on synthetic inorganic

ion exchangers (Amphlett et al., 1964; Vesely and Pekareck, 1972; Clearfield, 1982;

Frache and Dadone, 1972). In India, a number of such inorganic materials have been

28

prepared and explored for different applications during the past 35 years. The work

being done by Anil K De Shantiniketan and Tandon at Roorkee on the synthesis of

ion exchangers has attracted a lot of interest from various quarters.

2.2. Properties of ion exchange process

Since the discovery of ion exchangers, they have been used for diverse

applications. The ion exchange material comprises of two main groups such as

organic and inorganic exchangers. Both groups include synthetic and natural

materials. Ion exchangers contain a fixed electric charge which can bind counter ions

with an opposite charge. The inorganic groups are attached to the skeleton either

directly or through another group (Varshney et al., 1998). The exchange of the ions

between the solution and ion exchangers is a physiochemical process and has some

properties as follow:

1. The ion exchange process takes place between the like charges.

2. The ion exchange process is reversible in nature.

3. The exchange reaction takes place on the basis of equivalency and in

accordance with the principle of electroneutrality.

2.3. Characteristics of ion exchangers

In order to characterize a new material as an ion exchanger, following

properties may be studied in detail:

1. Ion exchange capacity

2. Chemical and thermal stability

3. Selectivity

4. Elution concentration and concentration behavior

5. pH - titration

6. Composition

7. Structural studies

8. Analytical applications

29

2.4. Types of ion exchangers:

2.4.1. Inorganic ion exchangers

The ion exchangers recently have drawn considerable interest due to an

increased interest in industrial applications. Synthetic ion exchangers are the chemical

compounds prepared with the desired physical and chemical properties. The inorganic

ion exchangers depending upon their composition are classified by Vesley into the

following types (Vesley and Pekarek, 1972):

1. Synthetic Aluminosilicates

2. Oxide and hydrous oxides

3. Acidic salts of polyvalent metal ions

4. Heteropolyacid salts

5. Insoluble hydrated metal ferrocyanides

2.4.1.1. Synthetic aluminosilicates

The first inorganic ion exchangers successfully used for the large scale

effluent treatment were the natural zeolites. The zeolites are basically made up of

aluminosilicates and are available as microcrystalline powders, pellets or beads. Later,

the synthetic zeolites were prepared to overcome the disadvantages of the natural

zeolites. The synthetic zeolites were more preferred as compared to natural zeolites,

as they could be manufactured with wide variety of pore sizes and chemical properties

and stabile at high temperatures. Moreover, synthetic zeolites have suffered from

some major limitations as:

(a) Their comparatively high cost

(b) Limited stability at either very high or very low pH range

(c) They have limited mechanical stability

A lot of investigation has been carried out to study the usefulness of the

locally available synthetic zeolite for the removal of metals like cesium, strontium and

thorium (Biskup and Subotic, 2010; Sinha et al., 1996).

30

2.4.1.2. Oxides and hydrous oxides

Oxides and hydroxides have been used as excellent material for ion exchange

applications. Freshly prepared trivalent metal oxides are used most effectively as ion

exchangers. Hydrous ferric oxide and ferric hydroxide have been used for the

adsorption of alkaline earth cations (Kurbatov et al., 1951; Ratner, 1948). A wide

range of hydroxides display an excellent selectivity towards elements due to their

amphoteric nature. Metals of groups 3, 4, 13 and 14 usually form hydrous oxides.

Hydrous titanium oxide shows high selectivity for Cs+ and can be used for the

preconcentration of uranium (Kise and Sato, 2003). Freshly prepared magnesium

oxide have been used as scavenging agent towards fission products in the solution

(Tye, 1976 ; Preetha and Janardanan, 2010). Hydrous cerium oxide and tin oxide have

been used for the separation of caesium from water systems (De and Chowdhury,

1974). Quadrivalent metal oxides have also been used as ion exchangers and used for

different applications. Inoue and Yamazak in 1987 have synthesized the hydrous

metal oxide with composition i.e. TiO2. (2.0 - 2.3) H2O, SnO2. (2.1-2.2) H2O, ZrO2.

(3.9 - 4.1) H2O and Nb2O5. (5.0 - 5.5) H2O (Inoue and Yamazak, 1987). The hydrous

metal oxides were investigated for their ion exchange capacity, thermal stability and

distribution coefficient (Kd value) for representative element ions and transition metal

ions.

2.4.1.3. Acidic salts of polyvalent metal ions

Multivalent metal ions include mostly the metal ions of the d block. Acidic

salts of polyvalent metal ions have been used as ion exchangers. The acidic salts of

multivalent metal ions are formed by mixing the solutions of the salts of III and IV

group elements with more acidic salts. The most commonly used metals studied are

zirconium (IV), thorium (IV), titanium (IV), cerium (IV), tin (IV), aluminium (III),

iron (III), chromium (III) etc. and the anions used includes phosphate, arsenate,

antimonate, vanadate, molybdate, tungstate, silicate, oxalate etc. These salts possess a

gel like microcrystalline structure and usually act as cation exchangers. They have a

high chemical, thermal and radiation stability (Yeh, 2002). The cation exchange

properties of these compounds may arise due to the presence of readily exchangeable

hydrogen ions, associated with the anionic groups present in the salts.

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2.4.1.4. Metal ferrocyanides

Insoluble metal ferrocyanides have also been used as ion exchangers. They are

prepared by the precipitation of metal salt solutions with H4[Fe(CN)6], Na4[Fe(CN)6]

or K4[Fe(CN)6] solutions. The acidity, order of mixing and the initial ratio of reacting

components determined the composition of these precipitates. They are stable in acid

solutions up to 2 M concentration. Metal ferrocyanides have been used for the

separation of radioactive wastes and other fissionable material. Baetsle explored

ferrocyanide molybdate and established its structure by X- ray studies (Baetsle et al.,

1965). For the first time amine based ferrocyanides were prepared by researchers who

prepared a cobalt amine ferrocyanide (Hahn and Clein, 1968). It was followed by the

preparation of Sn(III) and Sn(IV) ferrocyanides (Varshney and Gupta, 1990). The

insoluble metal ferrocyanides have numerous applications in analytical chemistry due

to their good chemical, mechanical strength and high selective ion exchange capacity.

2.4.1.5. Heteropolyacid salts

Heteropolyacid salts can be used as inorganic ion exchangers. These ion

exchanger have been derived from 12 - heteropolyacids with general formula

HmXY12O40.nH2O where m is 3, 4 or 5, X may be phosphoric, arsenic, silicon,

germanium or boron and Y represents elements such as molybdenum, tungsten,

vanadium etc. The heteropolyacids containing small cations are comparatively more

soluble than those with larger cations. In strong alkaline solutions these acids undergo

hydrolytic degradation. The ion exchange mechanism of heteropolyacid salts was

studied extensively by Van (Van et al., 1964). In 1981, Qureshi et al have been used

these materials for the separation of radiochemical waste (Qureshi et al, 1981). Gupta

et al in 2000 have synthesized and characterized a chemically stable heteropolyacid

based ion exchanger (Gupta et al., 2000). These exchangers were studied for the

separation of Zn2+, Cd2+, Co2+, Ni2+ metal ions from aqueous solution. It was observed

that three component ion exchangers possess ion exchange properties different from

those of the two-component ion exchangers. In addition, they show superiority over

the two component ion exchangers mainly due to three reasons:

1. The ion-exchange capacities are higher than those of two component ion

exchangers

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2. They are more selective

3. They are thermally and chemically more stable

In view of the above facts, the researchers have focused to synthesize and

investigate the ion exchange behavior of three component ion exchange materials. In

the recent years, a number of synthetic inorganic ion exchangers based on tetravalent

metals have been synthesized with selectivity and intercalation properties (Qureshi et

al., 1996; Jaimez et al., 1997; Serlei and Claudio, 1997; Clearfield and Wang, 2002)

Heteropolyacid salts based on Sn (IV), Zr (IV), Ti (IV) and Th (IV) have been

reported as good ion exchange materials.

Literature survey revealed that many inorganic ion exchanger such as

zirconium (IV) iodooxalate (Singh et al., 2002), zirconium (IV) iodovanadate (Singh

et al., 2003), zirconium (IV) selenomolybdate (Gupta et al., 2000), zirconium (IV)

aluminophosphate (Varshney et al., 1998), Zirconium (IV) tungstoiodophosphate

(Qureshi et al., 1995), zirconium (IV) antimonoarsenate (Mittal and Singh, 2006),

zirconium vanadate (El-Latif et al., 2008), zirconium (IV) tungstomolybdate (Nabi et

al., 2007) have been synthesized, characterized and used for different applications.

Titanium (IV) molybdosilicate has been found selective for Pb2+ and Bi3+ (Nabi et

al., 2007). Zirconium (IV) molybdotungsto vanadosilicate was prepared by Zonoz and

co workers and found effective for the selective removal of specific radionuclides

(Zonoz et al., 2009).

Zirconium molybdate and zirconium silicate were successfully applied for the

separation of some metal ions such as sodium, cobalt and europium by applying

chromatographic techniques (El-Gammal and Shady, 2006). The separation of amino

acids using a mixture of ammonium tungstophosphate and silanized silica gel and

ammonium tungstophosphate molybdophosphate layers have been reported (Lepri et

al., 1981). Nabi and Khan have applied the thin layer chromatographic technique for

the separation of several amino acids by using stannic arsenate-cellulose layer (Nabi

and Khan, 2003).

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2.4.2. Organic ion exchangers:

The organic ion exchangers are insoluble, cross linked, long chain polymers

with a microporous structure and a functional group attached to the chain which is

responsible for the exchange of ions. These resins have high ion exchange capacity

and high chemical stability. The organic ion exchanger was first developed by Adom

and Holms in year 1935. The most abundant groups of ion exchangers today are the

synthetic organic resins present in both powder and bead forms. The resins comprise

of a flexible frame work of long hydrocarbon chains. The frame work possesses the

ionic group such as -SO3-, -COO-, -PO3

2-, -AsO32- etc. in cation exchangers and -

NH3+, -NH2

+, -N+ etc. in anion exchangers. These resins are insoluble due to the cross

linking of the hydrocarbon chains. The extent of cross linking helps to know the width

of the matrix, hardness and mechanical durability of the ion exchangers. The organic

ion exchangers have a few advantages such as high exchange capacity, wide

applications and low cost.

The main limitation of the organic ion exchange resin is their low stability

towards radiations and heat. The majority of the commercial resins are based on the

styrene-divinylbenzene structure because of its good resistance against chemical and

physical stress. The structure is stable at relatively high temperatures and over the

whole pH range. The ion exchange properties of organic resins are mainly based on

ionogenic groups which can be attached to practically all the styrene rings in the

styrene - divinylbenzene co-polymer. Ion exchange resins have been used for the two

step cyanide recovery treatment of acidic copper or zinc solutions. The resin was also

used in baths for removing the cationic impurities. Picolylamine resins has been used

for removing trace amounts of metal cations from the background of very high

concentrations of alkaline and alkaline earth metal ions at acidic pH (Sengupta, 1991).

2.4.3. Composite ion exchangers

Both inorganic and organic ion exchangers have their own limitations. For

example inorganic ion exchangers are non-reproducible in nature and if fabricated

into rigid beads type media then are not suitable for column chromatography. Organic

polymeric part of the composite provides mechanical and chemical stability, whereas

the inorganic part supports the ion-exchange behaviour, thermal stability and also

34

increases the electrical conductivity. The synthesis of hybrid ion exchangers with

controlled functionality and hydrophobicity could open new avenues for

organometallic chemistry, catalysis, organic host guest chemistry, analytical

chemistry, hydrometallurgy, antibiotic purification, separation of radioactive isotopes

and large scale application in water treatment and pollution control.

The composite materials have numerous applications in the field of chemistry,

biochemistry, engineering and material science (Collinson, 1999). This transformation

of ion exchangers from inorganic to organic to composite have solved a lot of

environmental issues and thus have attracted a lot of attention of environmentalists.

Simple sol-gel method has been adopted universally for the preparation of organic-

inorganic composite materials (Philipp and Schmidt, 1984). The hybrid materials are

granular in nature and hence are suitable for column operation which makes it more

suitable for reuse. The organic polymers such as polyaniline, polyprrole, polystyrene,

chitosan, cellulose, polyacrylonitrile etc contribute extensively towards the

mechanical strength in the composite ion exchange materials. In an endeavor to

synthesize efficient ion exchange materials ligands of complexing agents were also

used. In these materials various chelating groups like dimethyl glyoxime have been

incorporated into the matrix. These type of ion exchangers have been developed

recently and explored for analytical applications.

Vernon and Eccles prepared a number of chelating ion exchangers by

incorporating ligands on to the resins (Vernon and Eccles, 1976). These chelating ion

exchangers have greater selectivity as compared to the conventional type of ion

exchangers. The nature of the chelating group determines the affinity of a particular

metal ion for a certain chelating resin. The combinations of organic polymers and

inorganic materials have led to the formation of the organic-inorganic hybrid ion

exchange materials to create high performance and superior materials. Thus, organic-

inorganic hybrid materials are expected to provide many possibilities.

The hybrid ion exchangers are synthesized to modify the organic polymeric

materials or the inorganic materials in order to exhibit entirely different properties

from their original components. These hybrid ion exchangers showed the

improvement in chemical, mechanical, radiation stability and a few other properties.

35

Khan et al. has successfully reported the application of hybrid ion exchange materials

for chromatographic techniques (Khan and Alam, 2004; Khan and Inamuddin, 2006a;

Khan et al., 2005).

The hybrid ion exchangers are three dimensional porous materials in which

various layers are cross linked forming layered compounds containing sulphonic acid,

carboxylic acids or amino groups. Many composite ion exchangers which have been

synthesized and used for diverse applications include pyridinium - tungstoarsenate

(Malik et al., 1983), zirconium (IV) sulphosalisylo phosphate, styrene - zirconium

phosphate, polypyrrole - thorium (IV) phosphate, polyaniline - tin (IV) phosphate

(Khan and Inamuddin, 2006b), polyaniline - tin (IV) arsenophosphate (Khan et al.,

1999), polystyrene zirconium (IV) tungstophosphate (Khan et al., 2002), poly-o-

toluidine - thorium (IV) phosphate (Khan et al., 2007), poly-o-anisidine - tin(IV)

phosphate (Khan and Khan, 2009) and poly-o-toluidine - zirconium (IV) phosphate

(Khan and Akhtar, 2008).

Polypyrrole have been used for the selective separation of Pb2+, Hg2+, Cd2+

(Khan et al., 2003). Pandit and Chudasma have synthesized o-chlorophenol -

zirconium (IV) tungstate and p-chlorophenol - zirconium (IV) tungstate and used

them for analytical applications (Pandit and Chudasma, 2001).

Pectin - thorium (IV) phosphate which has been synthesised by sol gel method

has found many analytical applications (Vershney et al., 2003). Gupta et al. in 1994

have reported polyaniline -zirconium (IV) tungstophosphate for the separation of La3+

and UO22 + form water system (Gupta et al., 1998).

Cellulose acetate - zirconium (IV) molybdophosphate was found to have high

thermal stability and was applied for the separation of metal ions such as Mg2+, Ca2+,

Fe2+, Cr3+, Zn2+ and Cd2+ from synthetic samples and pharmaceutical formulation

(Nabi and Naushad, 2008).

Nabi et al have reported the synthesis of polyaniline stannic silicomolybdate

and studied the quantitative separation of lead ions from industrial effluents (Nabi et

al., 2011). Poly-o- methoxy aniline - Zr (IV) molybdate composite cation exchanger

was found effective for the removal of cadmium ions from polluted water (Al-Othman

36

et al., 2011). The wide range of applications of the composite ion exchangers have

been observed in the following areas:

1. Effluent management (Bolto and Pawlowaski, 1983)

2. Softening of water (Strauss and Puckorius, 1984)

3. Separation of metal ions (Mulik and Sawicki, 1975)

4. Catalysis (Arrad and Sasson, 1989)

5. Hydrometallurgy (Mindler and Paulson, 1953)

6. Ion exchange fiber (Arshad et al., 2008)

7. Electrodialysis (Meyer and Strauss,1940)

8. Ion selective electrode (Rai and Chattopadhyaya, 2002)

9. Conducting polymers (Khan and Akhtar, 2008)

10. Nuclear separation (Yousefi et al., 2012)

Nanocomposites are a new class of materials containing particle filled polymer

with very small phase dimensions in nanometer scale (Alexandre and Dubois, 2000).

Already the nano composite materials have found a wide range of applications in

diverse field such as construction, transportation, electronics and other consumer

products (Ganguli et al., 2008; Murray et al., 2000). Due to their nanometer size the

nanocomposite materials possess exclusive characteristics which are not shown by

their conventional microcomposite counterparts due to which they offer a brand new

technology along with business prospects (Chazeau et al., 1999; Heron and Thon,

1998). These nanocomposites exhibit stiffness, strength and stability in two

dimensions. The nanocomposite materials have some excellent properties such as

promoting thermal, mechanical (Becker et al., 2002), molecular barriers (Liu et al.,

2013) and flame retardant behavior (Drabik and Slade, 2004).

Poly-o-toludine - thorium (IV) phosphate nanocomposite was synthesized with

a partical size in the range from 11.00 to 18.00 nm having better ion exchange

capacity as compared to its inorganic counterpart. This composite material was used

to prepare an ion selective membrane electrode for the detection of Hg2+ ion in

aqueous solution (Khan et al., 2007). Nanocomposite materials like poly-o-anisidine -

tin (IV) arsenophosphate (Khan et al.,2009) and Poly-o-toludine Ce (IV) phosphate

(Khan and Akhtar, 2011) were reported and explored for their analytical properties for

37

the preparation of ion selective electrode membranes in order to detect the Pb2+ ions

and Cd2+ ions from aqueous solution.

Polynailine - Zr (IV) sulphosalicylate nanocomposite ion exchanger was

synthesized and characterized for its adsorption behavior (Nabi et al., 2011). Khan

and Khan have reported the synthesis, characterization and electrical conductivity of

polyanisidine - Sn (IV) phosphate [POASn(IV)P] nanocomposite cation exchanger

(Khan and Khan, 2009).

Recently, polyaniline zirconium (IV) silicophosphate (PANI–ZSP)

nanocomposite ion exchanger was prepared using sol–gel method (Pathania et al.,

2014). The nanocomposite ion exchanger was characterized by different techniques

and studied for thermal stability, elution behaviour, concentration behaviour and acid-

base properties. The nancomposite material exhibit higher ion exchange capacity

(1.05meq/g) as compared to its inorganic counterpart (0.65meq/g). The

nanocomposite ion exchanger was utilized as photocatalyst for the remediation of

methylene blue dye from water. It was also successfully used as an antibacterial agent

against Escherichia coli.

Polyaniline - zirconium (IV) silicophosphate nanocomposite has been used for

the removal of methylene blue dye from water system. The adsorption data was

studied using various isotherms, kinetic models and thermodynamics. The maximum

adsorption capacity of methylene blue (MB) onto nanocomposite was found to be 12

mg/g. The adsorption of MB onto nanocomposite followed the second-order kinetics

and best fitted in the Frendluich isotherm. The thermodynamic parameters such as

enthalpy change (∆H°), entropy change (∆S°) and free energy change (∆G°) were

found to be 4.42 kJ/mol, 33.18 J/mol K and −5.80 kJ/mol, respectively (Gupta et al.,

2014).

Guar gum - cerium (IV) tungstate nanocomposite (GG/CTNC) cationic

exchanger was used as potential adsorbent for the remediation of methylene blue. The

correlation coefficient value indicated a good fit of monolayer Langmuir model to the

adsorption of methylene blue. The adsorption kinetic study revealed that the

adsorption process followed the pseudo second order kinetics. The Gibbs free energy

values confirmed the spontaneous nature of adsorption process (Gupta et al., 2014).

38

Pectin - thorium (IV) tungstomolybdate (Pc/TWM) nanocomposite was

synthesized and characterized using different techniques. The nanocomposite ion

exchanger was thermally stable and retained 59% of its ion exchange capacity upto

400◦C. The nanocomposite was explored for antibacterial and photocatalytic

activities. 76% of methylene blue dye was photocatalytically degraded after five hours

exposure (Gupta et al., 2013)

2.5. Photocatalysis

Environmental pollution is the major concern of all the human population

today. A considerable percentage of the world’s production of dyes is lost during the

process of dyeing in the water system. The presence of dyes in the water system is

posing a dangerous effect to human beings as well as aquatic life (Asahara et al.,

2009; Aksu, 2005). Photocatalysis has become a very important technology for

eradicating this environmental problem. More and more technologies are being

developed for the removal of organic pollutants from waste waters (Klavarioti, et al.,

2009).

Lately, due to increasing population and rapid industrialization, water

pollution has become a major issue. The textile industries discharge their dye

effluents into the water bodies which affect the physical and chemical nature of

natural water and makes it unfit for use. The dyes used in textile industries have

complex structure and most of them are mutagenic and carcinogenic to human beings

(Kant et al., 2014). Methylene blue (C16H18 N3SCl) is a blue coloured powder which

is water soluble and causes different problems in humans such as nausea, haemolysis,

hypertension and distress in respiration. Several classical and conventional methods

have been used to remove the organic contamination from effluents but are not

reliable and effective. The commonly used techniques such as coagulation, microbial

degradation, chemical oxidation, adsorption and photocatalysis have been explored

for the removal of organic pollutants from the aqueous system (Wang et al., 2010).

Among these techniques, photocatalysis is the most efficient and consistent method

for the degradation of a large variety of organic dyes due to their simplicity, fast

degradation and non generation of toxic materials (Anbia and Ghaffari, 2011).

39

Presently, a number of inorganic metal oxide nanoparticles like ZnO nano

materials have been synthesized due to their characteristic optical, electrical,

mechanical and piezoelectrical properties. The nanoparticles such as TiO2, SnO2,

ZnO, ZrO2, SrTiO3, CdS, MOS2, Fe2O3, WO3 and WS2 have been identified as

efficient photocatalysts for the degradation of various organic pollutants.

Photocatalysis is one of the most widely accepted techniques used for pollutant

removal from water system (Bharti and Varshney, 2010; Pouretedal et al., 2009).

The various types of nanoparticles such as SrTiO3, CdS, Bi2O3/Cu2O, Fe2O3

etc. have been investigated as effective photocatalysts for the degradation of organic

pollutants (Gupta et al., 2013; Xu et al., 2007). However, the composite ion

exchangers with nano scale dimensions have attracted a great concern due to their

varied applications in different fields. A detailed study of transition metal sulphides

has been carried out by Salem and Linsebigler for their catalytic properties (Salem et

al., 2003; Linsebigler et al., 1995). In photocatalytic degradation of organic dyes some

doped materials were also used. Wang applied Ag doped ZnO nano scale dimensions

for the degradation of methylene blue dye (Wang et al., 2004). Ullah and Dutta

investigated the applicability of manganese doped ZnO material for the

photocatalytical degradation of the methylene blue dye in aqueous system (Ullah and

Dutta, 2008). Hoffmann in 2003 reported wide applications of nanocomposites in

fundamental and applied research for the environmental protection (Hoffmann et al.,

2003).

The advantage of heterogeneous catalysis over other processes is the easy and

safe recovery of adsorbent and adsorbate by which secondary pollution can be

avoided (Lian et al., 2009). The composite ion exchangers exhibit a high efficiency in

heterogeneous photocatalytic process and hence have drawn the attention of scientists

(Karthikeyan,1990; Seoudi et al., 2012). The photogenerated electron-hole pairs

diffuse to the nanoparticle surface before recombination to initiate a chain of

photochemical reactions (Yang et al., 2013). Photocatalytic process resulted in the

oxidation–reduction and finally the degradation of a wide variety of organic pollutants

through their interaction with photo generated holes or reactive oxygen species, such

as •OH− and •O2− radicals. The advanced oxidation process initiated by photocatalytic

degradation has offered a better solution for decolourization, breakdown and

40

mineralization of dyes. Styrene based ion exchangers have been recorded cost

effective, easily processable, renewable and excellent material for remedial

applications (Khan et al., 2002; Varshney and Tayal, 2001). Polymer based

nanocomposites have been used as excellent photocatalyst as the polymer on the

surface of the catalyst helps to transfer the photogenerated electrons and holes and

prevents non radiative recombination of electrons and holes at surface.

Photocatalysis for degradation of dye

2.6. Antimicrobial property

Different techniques such as agar diffusion method and colony forming unit

method have been used for the determination of antibacterial activities of

nanocomposites against pathogenic bacteria. It was revealed that the major advances

in antibacterial drug development occurred in the middle of the 20th century and

helped to control the means of infection in humans (Feng et al., 2000). In the last few

years, the synthesis of new metal complexes for antibacterial activity has attracted a

significant attention. Several metal complexes have been investigated for

antibacterial, antifungal and anticancerous nature. Metal ion based nanomaterials

exhibit broad spectrum biocidial activity towards different fungi, bacteria and viruses

(Das et al., 2011; Greenberg et al., 2005).

Zarchi et al have investigated the effective long lasting antibacterial activity of

nano-TiO2 towards the gram negative bacterium E. coli (Zarchi et al., 2010). Zhang et

41

al in 2010 reported the green method for the preparation of silver nanoparticles with

aloe vera and recorded its synergic antibacterial effects (Zhang et al., 2010). The

antibacterial activity of cobalt complex has been reported (Saha et al., 2009). The

cobalt complex with histidine ligand was synthesized and studied for antimicrobial

activity against P. aeruginosa, E. coli and S. typhi. The results revealed the inhibition

of the bacterial growth by cobalt particals. The antibacterial activity of the silver

nanoparticals caped with linoleic acid was analyzed against pathogenic bacteria such

as S. basillus, S. aureus and P. aureginosa by Das et al. The results evidenced that

Ag-nanoparticals are effective against different microbes. It has been observed that

more than 97% bacterial growth was inhibited by the Ag - nanoparticals (Das et al.,

2011). The antibacterial activity of ZnO, CuO and TiO2 with S. cerevisiaewas

microorganism was studied by Kasemets et al. The effect of metal oxide nanoparticles

was investigated separately in both bulk and ionic forms and a comparison was made

(Kasemets et al., 2009; Sadiq et al., 2005).

2.7. Separation of phenols

Phenols and their compounds have been considered as ubiquitous pollutants

and may enter into water resources from the effluents of different chemical industries

such as phenol manufacturing, cool refineries, pharmaceuticals, dying, wood,

petrochemical etc (Fleeger et al., 2003; Mukherjee et al., 1990; Mukherjee et al.,

1991). Fractions derived from fossil fuels by distillation or by synthesis contain

phenol, the cresols, xylenols and polynuclear compounds. Inhalation and dermal

exposure to phenol is highly irritating to the skin, eyes and mucous membranes of

humans (Amoore and Hautala, 1983). Phenols and its derivatives also caused toxic

effect on fish. They have high bioaccumulation rate along the food chain due to their

lipophilicity (Jagetia and Aruna, 1997). Thus phenol pollution represents a threat

against natural environment and also to human health. Due to the presence of phenols

in the environment the fish food consumption, mean weight and fertility are

significantly reduced (Saha et al., 1999). Thus their presence and separation is water

system is of great concern.

Phenolic compounds embrace a wide range of naturally occurring substances,

but they are of two main groups such as simple phenolics and flavonoids. The simple

phenolic includes phenols, such as catechol and resorcinol: phenolic acids, such as

42

protocatechuic, syringic acids, and cinnamic acids (caffeic acid) and their lactone

derivatives. The flavonoids comprise of the widely occurring water soluble plant

pigments, the anthocyanins and flavones, and a number of related substances

(isoflavones, catechins, tannins and biflavonyls).

Thin layer chromatography (TLC) has been used as a preparative technique

for isolation and purification of compounds of interest. The origin of TLC can be

traced back to 1938 when two Russian researchers, Izmailov and Shraiber, utilized a

technique called drop chromatography on horizontal thin layers. It took another

twenty years for this technique to become a practical tool when Stahl described

equipment and efficient sorbents for the preparation of plates. TLC has been used for

the separation of phenolic compounds using different adsorbents. In 1948

chromatography became an established procedure in this field. The classical

separations of structural isomers of monohydric, dihydric and polyhydric phenols and

their derivatives have generally formed the basis for subsequent applications to

mixtures of more complex compounds. All these initial studies were essentially

qualitative and have led over the past four decades to quantitative work aimed at the

determination of a single phenolic substance in a mixture or the total phenolic

composition.

Thus the present study mainly deals with the synthesis, characterization and

analytical applications of the following nanocomposite cation exchangers:

• Cellulose acetate- Tin (IV) phosphate

• Cellulose acetate- Tin (IV) molybdate

• Styrene- Tin (IV) phosphate

• Styrene- Tin (IV) molybdate

This thesis incorporates five chapters:

1. Introduction presents a preview of the various types of ion exchangers and

their progressive development along with the environmental aspects.

2. Literature review deals with the research work done by various researchers in

the field of ion exchangers.

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3. Experimental includes the synthesis, characterization and applications of the

synthesized nanocomposite ion exchangers.

4. Results and discussion deals with the various results that have been analyzed

with the help of different analytical techniques.

5. Summary and conclusion present a recapitulation of the entire work.