Gelatin-polyvinyl alcohol/lanthanum oxide composite: A novel adsorbent for sequestration of arsenic species from aqueous environment

Novel gelatin-PVA/La2O3 (GPL) composite was prepared by copolymerization of polyvinyl alcohol (PVA) and gelatin in presence of La2O3 using glutaraldehyde as cross-linker. The BET surface area of the composite was 53.5m(2)/g. The GPL was used as an adsorbent for efficient removal of As(III) and As(V) from aqueous medium. The adsorption data was best fitted to the Langmuir isotherm model as indicated by higher R-2 values {0.981-0.983 for As(III) and 0.993-0.996 for As(V)} and lower values of standard error of estimation {1.13-1.21 for As (III) and 0.96-1.17 for As(V)}. The saturation capacity was 61 mg/g for As(III) and 100 mg/g for As(V). The arsenic adsorption rate was governed by pseudo-second order kinetics. The positive values of Delta S-o (0.0084-0.0047 kJ/mol/K) indicated increased randomness onto GPL-As(III) or As(V) interface. The positive Delta H-o values {As(III):16.8; As(V): 9.7 kJ/mol} implied endothermic adsorption. The negative values of Delta G(o) {As(III): 9.2; As (V): 5.0 kJ/mol} suggested spontaneity of the adsorption process. The reusability of GPL up to four adsorptiondesorption cycles, and its capability to remove arsenic species at the ppb levels, and from real wastewater samples spiked with arsenic proved the GPL composite as an efficient, economical, and environment compatible adsorbent for sequestration of arsenic species from water/wastewater.