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SYNTHESIS, CHARACTERIZATION ANDAPPLICATION OF ANTIMONY(V) ISOPOLY

ACID ION EXCHANGERS

Reetha Nanu Cheruvalath “Studies on some ion exchangers” Thesis. Department of Chemistry, Sree Narayana Post Graduate College, University of Calicut, 2006

CHAPTER I11

SYNTHESIS, CHARACTERIZATION AND APPLICATION OF ANTIMONY(V) ISOPOLY

ACID ION EXCHANGERS

Among the synthetic ion exchangers, insoluble salts of polybasic acids

and polyvalent metals had been studied extensively. Preparations of both

polycrystalline and amorphous compounds have been reported, among which

zirconium phosphate is the most widely studied one. Several other gelatinous

salts of titanium antimonate, -arsenate, -1nolybdate and -tungstate had been

studied as cation exchangers. Some of these were found to be more effective

than zirconiuin phosphate for specific purposes. Other compounds studied

include vanadate, tellurate, silicate, oxalate, salts of thoriuin(IV), cerium(IV),

aluminium(III), iron(III), chromium(III), uranium(VI), etc.. Recent

developn~ents in the study of such materials have led to a successful

preparation and characterization of well defined crystalline compounds. They

had layered structure and exhibited ion exchange properties. Knowledge of

the crystal structure gave a deeper understanding of their ion-exchange

processes and reversibility as well as a firm basis for the interpretation of their

therinodynainic properties.

Exchangers containing pentavalent metal ion, especially, antimony

have not been studied in much detail. The only laown antimony based ion

exchangers are antimonic acid1'', antiinony(V) silicatelS5 antimony

pentoxide156. Therefore, synthesis and ion exchange properties of the

following six antimony(V) based isopolyacid ion exchangers having different

anionic part are presented in this chapter. They are antimony(V) iodate,

antimony(V) selenite, antimony(V) vanadate, antimony(V) tellurite,

antimony(V) arsenite and antimony(V) arsenate. As the synthesis,

characteristion and application of these exchangers are similar, colnlnon

experimental procedure are given below.

3.1 Experimental

3.1.1. Reagents und solutions

Potassium pyroanti~nonate (made in Germany) and potassium iodate,

sodium selenite, sodium vanadate, sodium terllurite, sodiuin arsenite and

sodium arsenate (all BDH) were used. The other chemicals used were of

analytical grade. Double distilled water froin pyrex glass distillation unit and

calibrated measuring vessels were used. The following solutions were

prepared:

I. 0.05 and 0.1M solutions of potassiu~n pyroantimonate.

. . 11. 0.05 and 0.1 M solutions of potassium iodate, sodium selenite, sodium

vanadate, sodium tellurite, sodiuin arsenite and sodiun~ arsenate.

iii. 0.1 M standard NaOH.

iv. 1.0 M solutions of LiCl, NaC1, KC1 and BaC12

v. 0.005M solutions of Cd(II), PbCII), Zn(II), Ca(II), Cu(II), Ni(II),

Mg(II), Hg(II), Co(II), Al(III), Bi(II1) and Th(1V) salts.

vi. 0.005 M EDTA solution.

vii. 0.00 1 M, 0.0 l M and 0.1 M solutions of HN03 and NH4N03

Glass columns (id 1.1 cm) were used for column operations. A digital

pH meter, MK V1 (Csistromics) was used for pH measurements. Calibrated

glass wares were used for volumetric analysis. Thermal stability

measurements were performed using muffle furnace. For IR studies Perkin

Elmer model was used. For TG-DTA Lab: METTLER TOLEDOS R system

were used.

3.1.3 Syntlt esis

All the antimony(V) isopoly acid ion exchangers mentioned were

prepared according to a common method; i.e., aqueous solutions of potassium

iodate, sodiuin selenite, sodium vanadate; sodiuin tellurite, sodiuin arsenite or

sodium arsenate were added to acidic solution of potassium pyro antiinonate

in different concentration, pH, and mixing ratios. The mixture was stirred well

and the pH was adjusted using aqueous ammonia. The precipitate thus

obtained was allowed to stand in their respective mother liquor for 24 h at

room temperature. The precipitate was then filtered, repeatedly washed with

distilled water and dried at room temperature. The H+ form of the exchanger

was obtained by immersing the sample in 1M HN03 for 24 h and filtered,

washed with distilled water and dried at room temperature and stored over

NH4C1 in a desiccator. The different products obtained in 100- 150 mesh were

used in all experiments.

3.1.4. Clt emical conzposition

The composition of the exchanger was determined using a solution

obtained by dissolving a known amount of antimony(V) isopolyacid ion

exchanger in concentrated mineral acids. The antimony was determined as

pyrogallate. 157a Iodate as silver iodide157b, selenite gravimetrically'57c,

vanadate as silver ana ad ate'^^^, Tellurite as ~ e l l u r i u m ' ~ ~ ~ , asrinite was

determined by t i t r i m e t r i ~ a l l ~ ~ ~ ~ ' and arsenate gravimetrically a silver

arsenate'57g.

The IR spectra of the exchangers in H+ form using KBr disc on a

spectrometer and the thermogravimetric analysis of the exchanger in H+ form

was performed at a heating rate of 10°C/ min.

3.1.5. Determination of ion exchange capacity

The ion exchange capacity of material in H+ forin was determined by

column operation. The ion exchanger ( l .0 g) was placed in the column with a

glass wool support. Sodium chloride (1.0 M) was used as the eluent, and 200

m1 of eluate was collected in each case. The flow rate was maintained at 0.5

in1 inin-' The hydrogen ions separated from the coluinn were determined

titrimetrically with standard NaOH, The exchange capacity (ineqlg) was

a.v evaluated using the formula, -, where 'a' is the molarity, v is the volume of

alkali used during titration and W is the weight of exchanger taken. Exchanger

could be regenerated thrice without any appreciable loss of exchange

capacity.

3.1.6. Effect of temperature on ion exchange cripacity

1 g of the exchanger was heated for 3 h at various temperatures in a

thermostatically controlled hot air oven. The ion exchange capacities of the

heat treated samples were determined by the coluinn inethod after cooling

them to room temperature as described above.

The effect of electrolyte concentration on distribution coefficient was

studied by immersing the exchanger in solutions of the metal ions in various

concentrations of electrolytes (HN03, NH4N03, etc.) for 24 h, and

determining the Kd values by batch process.

3.1.7. pH titration curves

The pH titrations were performed by method of Topp and ~ e ~ ~ e r ' ' ~ .

About 500 ing portions of the exchanger were placed in 250 m1 conical flasks

and equiinolar solutions of alkali metal chlorides and their hydroxides in

different voluine ratios were added. The final voluine was restricted as 50 m1

to maintain a constant ionic strength. The pH of the solution was recorded

after every 24 h until equilibrium was obtained. The results were plotted to

get the pH titration curves.

3.1.8. Distrib crtion coefficient

The distribution coefficients (Kd) for different inetal ions in aqueous

media were deterinined by batch operations. 100 mg of the exchanger beads

in the H' form were equilibrated with 20 m1 of each metal ion solution for 24

h. The deterininations were carried out volumetrically using EDTA as the

titrant. Distribution coefficients were calculated by the formula,

where I is the initial volume and F is the final volume of EDTA; V is volume

of metal ion solution and A is weight of exchanger taken.

3.1.9. Sepnrntiolz of metal ions

The exchanger in H+ form (100 - 150 mesh size, 5g) was used for

coluinn operation in a glass tube having an internal size of (30 cm X 1.1 cm).

The column was washed thoroughly with distilled water and the mixture was

loaded. After recycling 2 or 3 times to ensure complete adsorption of the

mixture on the coluinn bead, the metal ions were eluted at a flow rate of 0.5

inllmin. The inetal ions in the effluent were determined quantitatively by

titration with EDTA. The metal ion concentrations in all cases were 0.005M

for binary and ternary separation, and 5 m1 of each of metal ion solution were

used. The separation was achieved by passing a suitable eluent through the

column. The eluents used were HC1, NH4N03, HN03, etc. in different

molarity.

3.2. Results and discussion

3.2.1. Atztiurzony(v iodate

Various samples of antimony(V) iodate (Table 1) have been prepared

in different conditions. As per Table 1, the sample No. l showed maximum

ion exchange capacity (2.39 meqlg) and hence it was used for the present

investigations. Although all inorganic exchangers dissolve completely in

alkaline medium, antimony(V) iodate exhibited significant insolubility in 0.0 1

M NaOH. However, it dissolved in 0.1 M NaOH. The exchanger was stable

in acetic acid, alcohol, 1.0 M solutions of HC1, HN03, LiC1, KC1, MgC12,

CaC12 and BaC12. It could be regenerated thrice without appreciable loss in

capacity.

IR spectra of the sample showed the following five bands at the

frequency ranges, 3401, 2363, 1629, 1350 and 741 cm'. The strong and

broad band at 3401 cm-' is characteristic of free water and OH groups. The

bands of strong intensities at 2363 and 1629 cm-' also represent the free water

molecules. Bands at1350 and 741cin-' are due to 1-0 and Sb-0 stretching

vibrations, respectively.

Therinoanalytical investigations threw some light on the empirical

formula and theoretical exchange capacity of the sample. The weight-loss up

to 390°C can be correlated to the loss of 3.34% of water. Assuming the

weight-loss at this temperature and the data obtained from chemical analysis,

the composition of the sample was fixed as Sb2051205. The number of moles

of water losed per Sb205 formula weight of the exchanger can be calculated

by the method of ~ lbe r t i '~ ' . If 'n' is the number of water molecules per mole

of mixed oxide, from the equation,

where X is the percentage of water content, and (M+18n) is molar mass of the

material. From this the number of water molecules was found to be n - 10.

Therefore, the formula assigned was Sb205120510H20

The effect of size and charge of the in going ion on the capacity of the

exchanger is shown in Table 2 for the alkali and alkaline earth metal ions.

The sequence shown by antimony(V) iodate is as follows.

Usually, at low aqueous concentrations and at ambient temperatures,

the extent of exchange increases with increasing valency of the ingoing ion,

ie. Ca(I1) > ~ a ( 1 ) ' ~ ~ ' . Antirnony(V) iodate did not obey this. The solubility

products of the corresponding iodates of the metal ion seemed to be

responsible for the deviation from normal behaviour. Under similar conditions

in the case of univalent ions the extent of exchange usually increases with

decrease in size of the hydrated cation.

K(1) > Na(1) > Li (I)

In the case of antimnony(V) iodate this sequence was found to be followed.

Antiinony(V) iodate retained about 80% of its exchange capacity after

drying at 100°C. The decrease in capacity on heating is due to the loss of

structural hydroxyl groups, bearing the exchangeable protons.

Distribution coefficients for eleven metal ions in demineralised water

(Table 3) showed a sequence, Ca(I1) > Cd(I1) > Cu(I1) > Pb(II)> Ni(I1) >

Hg(I1) > Mg(I1) > Co(I1) > Zn(I1) > Al(II1) > Th(1V). Effect of electrolyte

concentration on the distribution coefficient for certain inetal ions, such as,

Cd, Cu, Pb, etc. showed that increasing electrolyte concentration decreased

the distribution coefficients. These studies are important to find out the

elution behaviour. This observation is a general concept which is same for

all exchangers.

For binary -on, s & h w of metal ians of concefl~w 0,005M I

- ~ s ~ ~ ~ 1 o f c ~ - ~ ~ ~ , T h o , ~

a m i ~ w e r e a c h k v e d ~ g a ~ ~ @ f ~ e m b g e c Theel~e~ltsused

were ]HNOs -Q, H@ @ v d w $ &&m ("hbie 4). The m e r y

Q' 2 4 8 ' :

.- - mWb of -OH bm added

. - . - . .

Ibe pH titration -a obtained under qdiMum d t i m for NsUWPSICI,

KOWKCl and B t r ( O m C 1 2 showed W the exchanger was

mmofhct id as given in the figwe 3.

Table 1 . Conditions of synthesis and properties of' antitnony(V) iodate

Table 2. Effect of size and charge of the exchanging ions and temperature on the exchange capacity of antimony(V) iodate

Sample

Effect of size and charge 1 Effect of temperature

Hydrated Ion Exchanging exchange

ionic radii ion (A0)

capacity (1neq/g)

Molarity of reagent

Li (I)

Na (1)

I( (1)

Mg (11)

Ca (11)

Sr (11)

Ra (11)

Mixing ratio

S b(V)

Ion exchange capacity (1neq/g)

1 2 1 0.10 I 0.10

Colour of H' form

White (low yield)

1 White

Ion exchange capacity (mecl/g)

Table 3. llistribution coefficients of some nictal ions on antimony(V) iodate

Table 4. Binary separations on antimony(V) iodate

Cation

Zn.(l l)

Cd(ll)

Hg(ll)

Pb(l l)

Mg(ll)

Ca(l1)

Cu(ll)

Co(ll)

Ni(ll)

AI(III)

Th(lV)

Taken us

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

Mixture of metal ions

HE;(II)

Cd(I1)

Pb(I1)

Cd(I1)

Al(II1)

Cd(I1)

Th(1V)

Cd(I1)

Kd(mllg)

Eluents

0.01M HN03

0.1 M NNNO3 + 0.5M NH4N03

0.01M HN03

0.1 M NI-103 -I- 0.5M NH4N03

0.01M HN03

0.1M I-IN03 + 0.5M NH4N03

0.01M HN03

0.1M I-IN03 + 0.5M NH4 NO3

1166.00

114.00

146.40

103.95

Complete uptake

245.45

101.20

125.71

Metal ion loaded (mg)

0.1M HNO3

255.00

Recovered (mg)

0.01 M HN03

612.00

355.00

125.00

0.1 M NH4N03

450.00

350.20

0.001 M HN03

1055.0

110.00

130.00

630.00

230.00

100.00

120.00

0.01 M NH4N03

834.00

110.00

700.00

155.00

0.001 M NH2N03

113.00

145.00

102.00

complete uptake

240.00

101.00

125.00

3.2.2. Antimorty(V) selenite

Various samples of antimony(V) selenite (Table 5) have been prepared

at different concentrations. It was obtained as white amorphous powder. It is

evident from Table 5 that the sample No.1 showed maximum ion exchange

capacity (2.22 meqlg) and hence it was used for the present investigation. The

exchanger dissolved slightly in alkaline medium and was stable in 1.0 M

solutions of mineral acids and salt solutions. It could be regenerated thrice

without any loss in capacity.

IR spectra of the sample revealed the following data. There are seven

peaks in the spectrum at the frequency ranges 3782, 3418, 2364, 1635, 1415,

121 1, 753 and 464 cm". The strong and broad peak at 3418 cm-' is

characteristic of free OH groups. The sharp bands at 2364, 1635 and 1415

cm-' are assigned to water of crystallisation. The bands at 1219, 753 and 464

cm-' are due to Se-0 and Sb-0 stretching, respectively. Thermoanalytical

investigations threw some light on the formula and theoretical exchange

capacity of the sample. The weight-loss up to 100°C was found to be 4.92%

and correlated will with the loss of 4.9175 % water. The co~nposition of the

sainple by chemical analysis was found to be Sb203.Se02. The number of

moles of water lost per formula weight of the exchanger can be calculated by

the method of ~ l b e r t y ' l ~ . If n is the number of water molecules per mole of

the mixed oxide from the equation as explained earlier in the section 3.2.1 and

it is found to be 2.4. Hence the formula of the compound could be

ascertained as Sb2O5. Se02.2H20.

The effect of size and charge of the ingoing ion on the capacity of the

exchanger is shown in Table 6 for the alkali and alkaline earth metal ions.

The sequence shown by Antimony (V) selenite is as follows.

At low aqueous concentrations and at ordinary temperature the extent of

exchange increases with increasing charge of the exchanging ion ie. ~ a '

ca2+ . Antimony(V) selenite followed this sequence under similar conditions

and constant charge. For singly charged ion, the extent of exchange increases

with decrease in size of the hydrated cation.

This sequence was found to follow in the case of antiinony(V) selenite as

Antimony(V) selenite retained about 45% of the exchange capacity

after heating at 300°C (capacity 0.95). The decrease in capacity may be due

to loss of water molecules from the exchanger.

Effect of electrolyte concentration on the distribution coefficient for

certain metal ion like Ca, Mg, Th(IV), etc. showed that the distribution

coefficierrts demased witb in- of e1eddyk ooncentmticm and may be I

h adle camp&h&dmin tfieel-w.

The pH thtiofl CIWes shawed tbat the e x c h m p was

m o n o ~ ~ ~ m in figure.

For biaary @on, mlutims of metal ions of ootlcefl~un 0.005M

wmused. ~ ~ ~ ~ o f P b @ ) ~ H g O a n d ~ , C d @ ) f r o m ~

ThCIV) and M@) from C@) wem achieved on a cciIumn of the exchanger*

The elelnents used were I-IN0, andNI-14N03 and I-ICI at various dilutions

(Table 8). The recovery ranged froin 98 - loo%, with variation of 1% for

repetitive deterininantion.

Separation of ternary mixtures such as Pb(I1) from Th(IV), Hg(II),

Cd(I1) froin Th(IV), Ng(I1) and Mg(I1) froin Zn(II), Ca(I1) were successfully

achieved Table (9).

Table 5. Conditions of synthesis and properties of antimony(V) selenite

Salnple

Molarity of reagent

Mixing ratio

Colour of H' forin

White ainorphous

Ion exchange capacity (meq/g)

Table 6. Effect of size and charge of the exchanging ions and temperature effect on the exchange capacity of antimony(V) sclenite

Effect of size and charge I I

Effect of temperature

Exchanging ion

Table 7. Distribution coefficients of some metal ions on antimony(V) selenitc

Temperature ("C)

Hydrated ionic radii

Cation

Zn(ll)

Cd(ll)

Hg(ll) Pb(1l)

Mg(ll) Ca(ll)

Cu(ll)

Co(ll)

Ni(l1)

AI(! I I)

Th(1V)

Taken as

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

K d (mllg)

Distilled water

812.50

983.00

191 1 .OO

256.00

132.20

124.24

0.1M HN03

112.00

21 5.00

0.01M HNOs

432.00

535.00

810.00

125.00

0.001 M HN03

805.00

953.00

1851 .OO

255.00

130.00

120.00

0.100M NH4N03

215.00

372.00

0.001M NH4N03

0.001M NH4NO3

810.00

982.00

1855.00

250.00

132.00

120.00

Table 8. Binary separations on antimony(V) selenite

Pb(I1) 0.02M IHNO; + 0.5 M NH4NO;

0.0 1 M I-INO;

Mixtures of lnetal ions

Table 9. Termary separations on antimony(V) selenite

Eluents

Mixtures of metal ions

Th(IV)

Pb(I1)

Metal ion Loaded

Recovered (1%)

Eluents

0.01M I-IN03

0.1 M HNO;

0.2 M HNO; + 0.5 M NH4NO3

Metal ion Loaded (mg)

Recovered (1%)

Different sainples of antimony(V) vanadate have been synthesized

(Table 10). It was obtained an yellow ainorphous powder. It is evident from

Table 10 that the sainple No. 1 showed lnaxilnuin ion exchange capacity (2.03

meqlg) and hence it was used for further investigation. Although all ion

exchangers dissolve coinpletely in alkaline medium, animony(V) vanadate

exhibited significant chemical stability in O.1M NaOH. However, it dissolved

in 1.0 M NaOI-I. It was stable in 1.0 M lnineral acids and 1.0 M salt solutions.

It could be regenerated thricc without appreciable loss in capacity.

The IR spectrum showed bands at 3786 and 3402 (broad) and 722

cm". There are sharp bands at 2364, 1629, 1404 and 967 cm-'. The band at

3402 cm-' can be assigned to water of hydration. The band at 1629 cm-' can

be assigned to water of crystallisation. Mctal-oxygen stretching vibrations

have been assigned at 722 and 967 cm-'.

Chemical coinposition was found to be 1:l. TGA curve showed the

reinoval of water lnolecule at 95OC. This corresponds to a loss of about 3

water lnolecules per mole of the exchanger as pcr Alberty equation. I-Ience

the formula proposed was Sb205.V20531-120.

The effect of size and charge of the ion and that of the temperature on

ion exchange capacity were found to be similar as observed in previous cases

(Table 11). Distribution coefficients for eleven rnetal ions in dernineralised

as weiI as e f k t of et-&& amm@aW3 showed (Table 12) the *

Table 10. Conditions of synthesis and properties of antimony(V) vanadate

Table 11. Effect of size and charge of the exchanging ions and temperature on the exchange capacity of antimozj.(\~ vara2r;te

Mixing ratio

Sample

Effect of size and charge

Colour of form

Yellow amorphous

Pale yellow I1

Molarity of reagent

Exchanging ion

Mg(II)

Ca(I1)

Sr(I1)

B a(I1)

Temperature ("C>

Hydrated ionic radio (A0)

Ion exchange capacity (1neqk)

Table 12. Ilistribution coefficients of some metal ions on antimony(V) vanadate

Table 13. Binary separations on antimony(V) vanadate

Cation

Zn(ll)

Cd(ll)

Hg(ll)

Pb(ll)

Mg(ll)

Ca(ll)

Cu(ll)

Co(ll)

Ni(ll)

AI(II1)

Th(lV)

Mixtures of inetal ions

Eluents

Taken as

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

K d (mllg)

Metal ion Loaded

(111g)

Distilled water

892.24

691.66

683.30

734.37

613.04

158.30

1227.70

Recovered (1%)

Ni(I1)

Th(1V)

0.1M HN03

223.00

125.00

123.00

136.00

132.00

0.1 M HCI

0.1 M I-IN03 + 5M NH4NO;

0.01M HN03

435.00

232.00

230.00

242.00

248.00

0.001 M HN03

890.00

690.00

682.00

734.00

612.00

156.00

0.100 M NH4N03

128.00

700.00

0.001 M NH4NOj

252.00

0.001M NH4N03

891.03

691 .OO

683.00

734.30

613.00

158.00

came to uptake

85'.00

1225.00

Antiinony(V) tellurite obtained was white a~norphous powder (Table

14). The inaxiinu~n ion exchange capacity was found to 1.02 ~neqlg. The

exchanger was stable in dilute alkaline medium, in 1.0 M mineral acids and

1.0 M inetal salt solutions. It could be regenerated thrice without any

appreciable loss in capacity.

IR Spectra of the sample had eight band at the frequency range 3782,

3400, 2363, 1591, 1385, 961 and 73 1 cm-'. The strong and broad band at

3400 cm-' is characteristic of free water inolecule and hydroxyl group. The

bands at 2363 and 1591 cm-' also represent the free water molecules. The

bands at 1385, 1074 and 696 cm-' are due to Sb-0, Te-0 stretchings

respectively.

Ther~noanalytical investigation threw some light on the ~nolecular

formula and theoretical exchange capacity of the sample. The weight-loss,

25.19% correspondcd to 13 water inolecules as per the ~ l b e r t i ' ~ ~ method.

Froin the chemical analysis the inole ratio obtained was 2:l . Hence the

forinula of the exchanger was ascertained as Sb2O5, Te03, 13H20.

The effect of size and charge of the ion and temperature and the ion

exchange capacity, effect of electrolyte conce~ltration on distribution

coefficient were found to be in accordance with theory and is similar as

observed in the previous sections (Table 15).

W-., v?--

Mbntim ooefflcients of 12 metal ium in dimin&& water (Table

1 6 ) w e ~ e f a r m d i ~ t b e ~ c e :

Cu(1I) - I-Ig(II), Pb(I1) - Cu(II), Ni(I1) - Cu(II), Cd(I1) - Cu(I1) and Th(1V) -

Cu(I1) were achieved on the coluinn (Table 17).

Table 14. Conditions of synthesis and properties of antimony(V) tellurite

Table 15. Effect of size and charge of the exchanging ions and temperature on the exchange capacity of antimony(V) terrluite

Effect of size and change

Exchanging ion

Mg(II)

Ca(I1)

Sr(I1)

B a(I1)

Temperature ("c)

I-Iydrated ionic radii

Ion exchange capacity (1neqIg)

Ion exchange capacity (1neqk)

Table 16. Distribution coefficients of some lllctal ions on antimony(V) telllirite

Table 17. Binary separations on antimony(V) tellurite

Cation

Zn(ll)

Cd(ll)

Hg(ll)

Pb(l1)

Mg(ll)

Ca(1l)

Cu(ll)

Co(ll)

Ni(ll)

AI(I1I)

Bi(lll)

Th(lV)

Taken as

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

Mixtures of inetal ions

Hg(II)

CU(II)

Pb(I1)

Cu(I1)

Ni(I1)

Cu(I1)

Cd(I1)

Cu(I1)

Th(1V)

CU(II)

Kd (mllg)

Eluents

0. 1 M I-INO;

0.1M MNO; + 0.5 M NH;NO;

0.1M HNO;

0.1M HNO; + 0.5 M NN4N03

0.1M I-IC1

0.1M I-IN03 + 0.5 M NH4N03

0.1M HNO;

0. l M NNO; + 0.5 M NI-14N03

0.01 M I-INO~

0.1 MHN03 + 0.5 M NH4 NO;

Distilled Water

389.20

135.24

1250.90

Metal ion Loaded

0.1M HN03

112.00

Recovered (1ns)

0.01M HN03

188.00

189.00

712.00

0.001 M HNOJ

205.00

380.00

130.00

0.001M NH~NOJ

207.00

389.00

135.00

125.00

0.1 M NH4N03

125.00

0.01 M NH4N03

190.00

213.00

3.2.5. Antimo~zy(v arsenite

Various samples of antimony(V) arsenite have been prepared at

different conditions (Table 18). It is evident from the table 18 that the sainple

l showed inaxiinuin exchange capacity (2.89 ineqlg) and hence it was used

for the present investigation. It was obtained as white a~norphous powder.

The exchanger was stable in 1.0 M mineral acids and l .O M solutions of metal

salts. The exchanger could be regenerated four times without any

IR spectra of the sample showed the following features. There are six

bands in the spectrum at the frequency ranges, 3397, 2363, 1630, 1401, 1072,

773 and 616 cmm'. The bands at 3397, 2363, 1630 and 1401 cm-' are due to

0-H of water molecules. The bands at 1072, 773 and 616 cm-' are due to

inetal oxygen stretching vibrations.

Therinoanalytical investigations could be used to calculate the

~nolecular forinula and theoretical exchange capacity of the exchanger. The

weight-loss upto 100°C can be correlated to the reinoval of water ~nolecule

and is equal to 16.22%. The coinposition of the sainple by chemical analysis

was Sb205.As203. By the method of ~ l b e r t ' ~ ~ , the number of water molecules

present was 1 1. Hence the forinula ~nolecule was Sb205.A203. 1 1 I-120.

The effect of size and charge of the ingoing ion on the ion exchange

capacity of the exchanger is shown in Table 19. For the alkali and alkaline

earth inetal ion, the sequence shown by the exchanger was in accordance with

theory and was similar to the observations in the case of the other exchangers.

The effect of electrolyte concentration on distribution coefficient and

effect of temperature on ion exchange capacity of the exchanger showed that

the distribution coefficients decreased with increase in concentration and ion

exchange capacity decreased with increase of temperature.

Distribution coefficients for 12 inetal ions in demineralised water

(Table 20) decreased in the following sequence: Ni(I1) > Bi(II1) > Mg(I1) >

Hg(I1) > Ca(I1) > Pb(I1) > Th(1V) Cu(I1) > Zn(I1) > Cd(I1) > Co(I1) > Al(II1).

The pH titration curves shows that the exchanger was monofunctional

with respect to NaOHNaCl, KOHIKC1 and Ba(OH)2/BaC1 systems.

The important binary separations carried out on the exchanger column

were: Cd(I1) - Hg(II), Cd(I1) - Pb(II), Al(II1) - Th(IV), Al(II1) - Mg(I1) and

Cu(I1) - Ni(I1) as detailed in the Table 21.

h i L d -

M W t y of mqgent loa '

hfkiag &l~kUOf e~dlatlp

m. As03- ratio pH Wfam

1 0.05 0.05 I:1 1 White 2.89 ; - ;X

rnwphu9; - 2 0.1 0.05 1:l 1 2.0 ,, n

3 0.1 0.1 1:l 1 n 1-86,

4 0.1 0.1 1:2 1 n 1 .S4 L -.

S Q. f Q. 1 2: 1 1 U

Table 19. Effect of size and charge of the exchanging ions and telnperature on the exchange capacity of antimony(V) arsenite

Table 20. Distribution coefficients of some metal ions on antimony(V) arsenite

Effect of size and charge

Exchanging ion

Ca(I1)

Sr(I1)

B a(I1)

Cation

Zn(ll)

Cd(ll)

Hg(ll)

Pb(ll)

Mg(ll)

Ca(ll)

Cu(ll)

Co(ll)

Ni(ll)

AI(III)

Bi(lll)

Th(lV)

Temperature ("C)

Hydrated ionic radii

Ion exchange capacity (1neqJg)

Taken as

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

- Kd (mllg )

Distilled Water

104.28

585.00

400.00

406.06

124.19

1545.45

325.00

O.1M HNO3

0.01M HN03

0.001 M HN03

104.00

580.00

395.00

400.00

124.00

0.1 M NH4N03

0.01 M NH4N03

0.001M NH4N03

104.20

585.00

400.00

625.00

405.00

124.89

1540.00

325.00

Tablc 21. Binary separations on antimony(V) arsenite

3.2.6. Antinzony(v arsenate

Cd(I1)

Hg(II)

Cd(I1)

Pb(I1)

AI(II1)

Th(1V)

Al(II1)

Mg(II)

Cu(I1)

Ni(I1)

Different sainples of antimony(V) arsenate have been prepared under

different conditions (Table 22). The sample No.1 showed maximum ion

exchange capacity (2.60 meq) and obtained in good yield. The exchanger

obtained was white amorphous powder. It is stable in 1.0 M mineral acids

andl.O M metal salt solutions. It can be regenerated four tiines without any

IR spectra of the sample revealed the following. There were seven

bands in the spectruin at frequency range 3780, 3407.5, 2363, 1637, 1401,

Eluents

O.1M HNO;

0.2M MNO; + 15M NH4NO;

O.1M HN03

0.2M EINO; + 0.5M NIH4N03

O.1M MC1

O.1M I-INO; + 0.5M NI-14N03

O.1M HCI

0.1M HNO; + 0.5 M NH4N03

O.1M HCI

O.1M HN03 + 0.5M NH4N03

Metal ion Loaded

Recovered (1%)

808 and 619 cm-' indicating the presence of water molecules and metal-

oxygen bands in the sample.

Therinoanalytical investigations could be used to determine the

formula and theoretical exchange capacity of the sample. The weight-loss

upto 100°C could be assigned to a water loss and is 1 1.0 1 %. Based on the

mole ratio determined by chemical analysis, the empirical formula assigned

was Sb2O5 - As04 nH20. Using the method of Alberti, the number of water

molecules found out as 5. Hence the formula of the exchanger was assigned

as Sb205As045H20.

The effect of size and charge of the ingoing ion on the capacity of the

exchanger (Table 23) for the alkali and alkaline earth metal showed by the

exchanger was as:

At low aqueous concentrations and at ordinary temperature the extent of

exchange increases with increasing charges of the ongoing ion, i.e., Ca(I1) >

Na(1). But antimony(V) arsenate did not show this sequence. The solubility

products of the corresponding arsenates of the metal ions may be responsible

for the departure from expected sequence.

The study of the effect of electrolyte concentration on distribution

coefficient and effect of temperature on ion exchange capacity of the

cmmdmtim and ion ex- cmacit#.demead with increase of

'g> Distn'bution coefficients shown ?y the exchanger fm 11 metal h

d e d n d s e d water (Table 24) were in the following s e q ~

w n o fmctid with respeGt to NaOrnaC1, KOWKCl and mda(OHyBaCh '

The important Binary separation performed on the column of the

exchanger were Cd(I1) - Pb(II), Hg(I1) - Pb(II), Th(1V) - Pb(II), Co(I1) -

Cu(II), Ni(I1) - Cu(II), Mg(I1) - Al(II1) and Mg(I1) - Ca(I1) and the ternary

separations carried out were Mg(I1) - Th(IV) - Pb(II), Mg(I1) - Ca(I1) -

Cu(I1) and Mg(I1) - Th(IV) - Cu(I1) (Table 25).

Table 22. Conditions of synthesis and properties of antimony(V) arsenate

Sample

Molarity of reagent Mixing

Colour of H+ form

White alnorp hous

Table 23. Effect of size and charge of the exclianging ions and temperature on the exchange capacity of antimony(V) arsenate

Table 24. llistribution coefficients of some metal ions on antimony(V) arsenate

Effect of size and change

Exchanging ion

Mg(II)

Ca(I1)

Sr(I1)

B a(I1)

~ f f e c t of temperature

Cation

Zn(ll)

Cd(ll)

Hg(ll)

Pb(ll)

Mg(ll)

Ca(ll)

Cu(ll)

Co(ll)

Ni(ll)

AI(III)

Bi(lll)

Th(lV)

Temperature ("C)

I-Iydrated ionic radii

Taken as

Sulphate

Nitrate

Chloride

Nitrate

Sulphate

Chloride

Sulphate

Chloride

Nitrate

Ion exchange capacity (1neqIg)

Distilled water

71 3.63

81 1.47

193.68

487.50

0.1M HN03

186.00

213.00

0.01M HN03

296.00

325.00

125.00

315.00

0.01 M NH4N03

450.00

512.00

155.00

360.00

K d (rnllg)

0.001 M HN03

629.00

810.00

190.00

480.00

0.001M NH4N03

713.00

81 1 .OO

193.00

487.00

0.1 M NHdN03

21 3.00

250.00

Tahlc 25. Separations on antimony(V) Arsenate

Binary Separation

Cd(I1)

Pb(I1)

Hg(II)

Pb(T1)

Th(1V)

Pb(I1)

Co(I1)

Cu(I1)

Ni(I1)

Cu(I1)

Mg(II)

Al(II1)

Mid111

Ca(I1)

Ternary separation

Mg(II)

Th(1V)

Pb(I1)

Ca(I1)

Cu(I1)

Mg(II)

Th(1V)

Cu(I1)

Eluents

0.1 M HN03

0.1M Erno:, + 0.5M NH4N03

0.01M HN03

O.1M HN03 + 0.5M NM4 NO3

0. l M I-INO:,

0.1M HN03 + 0.5M NI-14N03

0 . 1 ~ IRJO~

0.1M m03 + 0.5M NH4N03

0.01 M HCl

0.1 M m03 + 0.5M NH4N03

0 . 0 1 ~ FJNO~

0.1 M HN03 + 0.5M NH4N03

0.01M HN03

0.1M HN03 + 0.5M NN4 NO3

0.01M NN03

0.1 M NM03

0.1 M HN03 + 0.5M NH4N03

0 . 0 1 ~ I-INO~

0.1 M I-INO~

0.1 M FIN03 + 0.5M NM4N03

0.1M FIN03

0.1M HN03 + 0.5M NI34N03

Metal ions Loaded

Recovered (mg)

3.3. Summary

Six isopoly acid exchangers of antimony(V) reported here had

individual importance with regard to their specific preference for certain

metal ions.

The ion exchanger, antimony(V) iodate had greater specificity for

cadmium and calcium ions. This exchanger could be used for the separation

of cadmium from other metal ions and also for the waste water analysis.

Antimony(V) selenite was specific for magnesium and lead. This

exchanger could be used for the environmentally important heavy elements

separation.

Antimony(V) vanadate was useful in the separation of Thorium metal.

The exchanger had high affinity for thorium. Now-a-days thoriuin separation

from other metal mixtures as well as from nuclear waste disposals are very

important.

Antimony(V) tellurite was found to be specific for bismuth and hence

the separation of this metal could be carried out using the exchanger.

Antimony(V) arsenite also had high affinity for bismuth. Both these

exchangers could be used for the binary separation of heavy elements which

are important in the waste water treatment.

Antiinony(V) arsenate was found to be very useful for the separation of

copper as it had high affinity for copper. Also this exchanger could be used

for the treatment of waster water obtained from spinning and weaving mills.

Also the exchanger was found to be very useful in binary and ternary

separatioils.

Finally, the present investigation showed that these exchangers were

had high ion exchange capacities compared to other exchangers studied till

date, except antimony(V) tellurite.

synthesis, characterization and …shodhganga.inflibnet.ac.in/bitstream/10603/26455/9/09...chapter...

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