Natrayasamy Viswanathan

Removal of fluoride from aqueous solution using protonated chitosan beads.

In the present study, chitosan in its more usable bead form has been chemically modified by simple protonation and employed as a most promising defluoridating medium. Protonated chitosan beads (PCB) showed a maximum defluoridation capacity (DC) of 1664mgF-/kg whereas raw chitosan beads (CB) possess only 52mgF-/kg. Sorption process was found to be independent of pH and altered in the presence of other co-existing anions. The sorbents were characterized using FTIR and SEM with EDAX analysis. The fluoride sorption on PCB follows both Freundlich and Langmuir isotherms. Thermodynamic parameters, viz., DeltaG degrees , DeltaH degrees DeltaS degrees and Ea indicate that the nature of fluoride sorption is spontaneous and endothermic. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. 0.1M HCl was identified as the best eluent. The suitability of PCB has been tested with field samples collected from a nearby fluoride-endemic area.

Uptake of fluoride by nano-hydroxyapatite/chitosan, a bioinorganic composite

A bioinorganic composite namely nano-hydroxyapatite/chitosan (n-HApC) composite which could be employed for technology development was prepared and studied for its defluoridation efficiency. It has been observed that there was a slight enhancement in the defluoridation capacity (DC) of n-HApC composite (1560mgF(-)/kg) than nano-hydroxyapatite (n-HAp) which has a DC of 1296mgF(-)/kg. The sorbents were characterized with XRD and TEM studies. The fluoride sorption was explained with Freundlich and Langmuir isotherms. Thermodynamic parameters such as DeltaG degrees , DeltaH degrees , DeltaS degrees and Ea were calculated in order to understand the nature of sorption. The sorption process was found to be controlled by pseudo-second-order and pore diffusion models. Field studies were carried out with the fluoride containing water sample collected from a fluoride-endemic area in order to test the suitability of the sorbents at field conditions.

Enhanced fluoride sorption using La(III) incorporated carboxylated chitosan beads.

The carboxylated chitosan beads (CCB), which have a defluoridation capacity (DC) of 1385 mg F(-)/kg, have been further chemically modified by incorporating La(3+) ion (La-CCB) and its DC was found to be 4711 mg F(-)/kg whereas the raw chitosan beads (CB) possess only 52 mg F(-)/kg. The fluoride removal by La-CCB is governed by both adsorption and complexation mechanism. The functional groups present in beads were identified by FTIR analysis. The surface condition and existence of fluoride on the beads was confirmed by SEM with EDAX analysis. The experimental data have been analyzed using Freundlich and Langmuir isotherm models. Thermodynamic parameters such as DeltaG(o), DeltaH(o) and DeltaS(o) were calculated to predict the nature of sorption. The kinetic studies were investigated with reaction-based and diffusion-based models. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village.

Defluoridation of water using magnesia/chitosan composite.

Magnesia (MgO) is a well-known adsorbent showing extremely high defluoridation capacity (DC). In order to over come the limitations of MgO for field applications, an attempt has been made to modify magnesia with abundant biomaterial chitosan to form magnesia/chitosan (MgOC) composite in a usable form and its merits over conventional magnesia and raw chitosan is established. Removal of fluoride from aqueous solution with MgO and MgOC composite was studied with batch equilibrium experiments. At equilibrium, MgOC composite has a DC of 4440 mg F(-)/kg while for magnesia it is only 2175 mg F(-)/kg. The physicochemical properties of the synthesised MgOC composite were analyzed with FTIR and SEM with EDAX studies. The equilibrium data were fitted with isotherm and kinetic models. Thermodynamic parameters viz, Delta G degrees, Delta H degrees and DeltaS degrees were calculated to understand the nature of sorption. Field studies were carried out to find the suitability of these sorbents at field conditions.

Fluoride sorption by nano-hydroxyapatite/chitin composite

In this study the fluoride adsorption potential of novel nano-hydroxyapatite/chitin (n-HApCh) composite was explored. The sorbent was characterized using FTIR studies. The effects of pH, interfering anions and contact time were studied. The sorption data obtained under optimized conditions were subjected to Langmuir and Freundlich isotherms. Kinetic studies indicate that the rate of sorption of fluoride on n-HApCh composite follows pseudo-second-order and pore diffusion patterns. n-HApCh composite possesses higher defluoridation capacity (DC) of 2840 mg F(-)kg(-1) than nano-hydroxyapatite (n-HAp) which showed a DC of 1296 mg F(-) kg(-1). Field trials were conducted with the sample collected from a nearby fluoride endemic area.

Sorption behaviour of fluoride on carboxylated cross-linked chitosan beads.

Carboxylated cross-linked chitosan beads (CCB) showed a significant defluoridation capacity (DC) of 1385 mgF(-)/kg than the raw chitosan beads (CB) which displayed only 52 mgF(-)/kg. Sorption experiments were performed by varying contact time, pH, presence of co-anions and temperature. The nature and morphology of the sorbent were discussed using FTIR and SEM with EDAX analysis. The stability of the beads in solution was explained in terms of swelling ratio of the beads. The fluoride uptake onto CCB obeys both Freundlich and Langmuir isotherms. Thermodynamic studies revealed that the nature of fluoride sorption is spontaneous and endothermic. Sorption kinetics is mainly controlled by pseudo-second-order and intraparticle diffusion models. 0.1M HCl was identified as the best eluent. The suitability of CCB at field conditions has been tested with field sample collected from a nearby fluoride-endemic area.

Role of metal ion incorporation in ion exchange resin on the selectivity of fluoride

Indion FR 10 resin has sulphonic acid functional group (H(+) form) possesses appreciable defluoridation capacity (DC) and its DC has been enhanced by chemical modification into Na(+) and Al(3+) forms by loading respective metal ions in H(+) form of resin. The DCs of Na(+) and Al(3+) forms were found to be 445 and 478 mg F(-)/kg, respectively, whereas the DC of H(+) form is 265 mg F(-)/kg at 10 mg/L initial fluoride concentration. The nature and morphology of sorbents are characterized using FTIR and SEM analysis. The fluoride sorption was explained using the Freundlich, Langmuir and Redlich-Peterson isotherms and kinetic models. The calculated thermodynamic parameters such as DeltaG degrees, DeltaH degrees, DeltaS degrees and sticking probability (S(*)) explains the nature of sorption. Comparison was also made by the elution capacity of these resins in order to select a cost effective material. A field trial was carried out to test the suitability of the resins with fluoride water collected from a nearby fluoride-endemic area.

Synthesis of Zr(IV) entrapped chitosan polymeric matrix for selective fluoride sorption

The Zr(IV) loaded carboxylated chitosan beads (Zr-CCB) was synthesised and fluoride removal studies were carried out in batch equilibration method. The results shows an enhanced defluoridation capacity (DC) of Zr-CCB (4850 mg F(-)/kg) than the carboxylated chitosan beads (CCB) and raw chitosan beads (CB) which possesses the DCs of 1385 and 52 mg F(-)/kg, respectively. The mechanism of fluoride removal by Zr-CCB is governed by both adsorption and complexation. The presence of functional groups, elements and the surface morphology of the sorbent were confirmed by FTIR and SEM with EDAX analysis. The experimental data have been analysed using Freundlich, Langmuir and Dubinin-Radushkevich (D-R) isotherms. The best fit isotherm model was identified using various methods of non-linear analysis. Thermodynamic parameters such as DeltaG degrees , DeltaH degrees and DeltaS degrees were calculated to predict the nature of fluoride sorption. A field trial was carried out with fluoride water collected from a nearby fluoride-endemic village.

Development of multifunctional chitosan beads for fluoride removal.

Chitosan beads (CB) which have negligible defluoridation capacity (DC) have been chemically modified by introducing multifunctional groups, viz., NH(3)(+) and COOH groups by means of protonation and carboxylation in order to utilize both amine and hydroxyl groups for fluoride removal. The protonated cum carboxylated chitosan beads (PCCB) showed a maximum DC of 1800 mg F(-)/kg whereas raw chitosan beads displayed only 52 mg F(-)/kg. Sorption process was found to be independent of pH and slightly influenced in the presence of other common anions. The fluoride sorption on modified forms was reasonably explained by Freundlich and Langmuir isotherms. The sorbents were characterised by FTIR and SEM with EDAX analysis. The sorption process follows pseudo-second-order and intraparticle diffusion kinetic models. The suitability of PCCB has been tested with field sample collected from a nearby fluoride endemic area.