title: Removal of fluoride from aqueous solution using protonated chitosan beads.
abstract: 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.
authors.affiliation: Department of Chemistry, Gandhigram Rural University, Gandhigram 624302, Tamilnadu, India. natrayasamy_viswanathan@rediffmail.com
authors.forename: Natrayasamy
authors.initials: N
authors.lastname: Viswanathan
authors.forename: C Sairam
authors.initials: CS
authors.lastname: Sundaram
authors.forename: S
authors.initials: S
authors.lastname: Meenakshi
mesh_terms: D000327:Adsorption; D002021:Buffers; D048271:Chitosan / Q000737:chemistry*; D004058:Diffusion; D005459:Fluorides / Q000737:chemistry* / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D011522:Protons; D012996:Solutions; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D002021:Buffers; D011522:Protons; D012996:Solutions; D048271:Chitosan; D005459:Fluorides