Environmental Engineering Reference
In-Depth Information
conducted suggesting that the n-HApC composite can be used as an effective deluorida-
tion agent.
Viswanathan and Meenakshi (2008) also reported carboxylated chitosan beads (CCB)
and lanthanum incorporated CCB (La-CCB). The adsorption capacity of CCB was
observed to be 1.385 mg/g, which increased to 4.711 mg/g after La incorporation. The
adsorption capacities of both CCB and La-CCB were signiicantly higher than luoride
adsorption capacity of raw chitosan beads (CB) (0.052 mg/g). The results of ield trials
indicated that the La-CCB can be effectively used for removal of luoride. Viswanathan
et al. (2009) also reported chitosan beads modiied by simple protonation. Protonated
chitosan beads (PCB) showed maximum deluoridation capacity of 1.664 mg/g, whereas
raw chitosan beads (CB) possess only 0.052 mg/g. The removal eficiency was observed
to be independent of pH; however, the presence of other coexisting anions also affects
the removal. The study also established that the materials can be easily regenerated
using 0.1 M HCl. The authors further extend modiication of CB by multifunctional
groups, namely
NH
3
+
and COOH groups. The protonated and carboxylated chitosan
beads (PCCB) showed a maximum deluoridation capacity of 1.8 mg/g, which was sig-
niicantly higher than raw chitosan beads. Field trial results conirmed that luoride
levels below permissible limits can be achieved using PCCB, and it can also remove
other ions in addition to luoride.
Titanium-modiied chitosan-based adsorbent has been explored for deluoridation
of water. Titanium macrospheres (TM) prepared by a precipitation method showed an
excellent luoride removal capacity of 7.2 mg/g, which is high compared with raw and
previously reported modiied chitosan (Jagtap et al., 2009). The good stability and settling
property of TM ensures good separation and makes it a potential material for deluo-
ridation. Davila-Rodriguez et al. (2009) prepared a biocomposite based on chitin and a
polymeric matrix, and studied the adsorption of luoride from aqueous solutions. The bio-
composite shows luoride adsorption capacity of 0.29 mg/g at pH 5.0 and initial luoride
concentration of 15 mg/L. Sundaram et al. (2009) reported a novel nanohydroxyapatite/
chitin (n-HApCh) composite for deluoridation of water with deluoridation capacity of
2.84 mg/g. The n-HApCh composite has several advantages, viz. biocompatibility, low
cost, and local availability. Viswanathan et al. (2010) have prepared and investigated a new
biocomposite by incorporation of zirconium (IV) tungsten-phosphate (ZrWP) into the
biopolymer matrix. The adsorption capacity of luoride from water by this ZrWP/chitosan
(ZrWPCs) composite was found to be 2.025 mg/g at pH 3.0 and initial luoride concentra-
tion of 10 mg/L. Considering the high afinity of luoride toward alumina, Viswanathan
et al. (2010) explored the possibility of preparation of alumina and biopolymeric com-
posite. Alumina/chitosan composite was synthesized by incorporating alumina particles
in the chitosan polymeric matrix, which showed maximum deluoridation capacity of
3.809 mg/g, signiicantly higher than both alumina and raw biopolymer. Jiménez-Reyes
et al. (2010) have explored the eficacy of HAp as a potential material for the treatment of
water contaminated with luoride ions. The sorption capacity of the HAp-based adsor-
bent was 4.7 mg/g at pH 5-7.3 with initial luoride concentration of 5 mg/L. Thakre et al.
(2010) synthesized lanthanum-incorporated chitosan beads (LCB) using a precipitation
method, and evaluated for luoride removal from drinking water. The LCB-10 exhibited
luoride adsorption capacity of 4.7 mg/g, which is reasonably higher than the commer-
cially used AA and signiicantly higher than raw chitosan. Besides having high adsorp-
tion capacity, LCB-10 also possesses relatively fast kinetics, high chemical and mechanical
stability, high resistance to attrition, negligible lanthanum release, suitability for column
applications, etc.
