Adsorptive removal of phosphate from aqueous solution using rice husk and fruit juice residue

The aim of the present study was to investigate the possible use of fruit juice (Citrus limetta) residue and rice husk as adsorbents for phosphate removal from aqueous solutions. Batch experiments were performed to achieve maximal phosphate removal by varying process parameters, like pH, contact time, temperature, adsorbent dose and initial solute concentration. FTIR studies revealed that OH, NO and CN groups are responsible for phosphate binding process. The maximum removal of phosphate was achieved as 95.85% at 298 K, adsorbent dose 3 g/L and pH 6.0 with acid treated fruit juice residue. Adsorption process was fitted with pseudo-first order kinetics at 298, 308 and 318 K, respectively. Various isotherm models and mass transfer mechanisms were studied for the removal of phosphate ions from aqueous solutions. Among various adsorption isotherms, Freundlich isotherm showed a better correlation with experimental data. The adsorption energy calculated from Dubinin-Radushkevich isotherm for the most efficient adsorbent indicated physical nature of adsorption.