An efficient and regenerable quaternary amine modified chitosan beads for the removal of nitrate and phosphate anions

This paper presents a study of the adsorption of nitrate and phosphate ions from aqueous solution using quaternized chitosan beads (QCB) which is produced through the reaction of cross-linked chitosan beads and glycydyl trimethyl ammonium chloride (GTMAC). A series of batch experiments were conducted to examine the effects of contact time, the initial concentration of adsorbate, adsorbent dosage, solution pH, temperature and effect of co-ions. The sorption capacity (SC) of QCB toward nitrate and phosphate from 1000 mg/L solutions were 67.5 and 59 mg/g, respectively. Presence of common anions like Cl−, HCO3− and SO42− has not altered the SC of nitrate and phosphate. The results of pH effects indicated that the QCB effectively adsorbs nitrate and phosphate in the pH ranges of 3–9. Equilibrium isotherm data of adsorption of both nitrate and phosphate were well fitted to the linear Freundlich isotherm model. The adsorption kinetics data were best described by the pseudo-second-order rate equation. QCB was regenerated using the aqueous solution of 0.025 M NaCl within 30 min. The regeneration studies were carried out up to 10th cycle, even then 99% and 97.5% of the actual adsorption efficiency for respective nitrate and phosphate were retained. The QCB was characterized using SEM, EDAX, FTIR and thermal studies.