Biosorption of As(V) onto the shells of the crab (Portunus sanguinolentus): Equilibrium and kinetic studies

Abstract

Worldwide concerns over inorganic arsenic in water bodies have prompted much research and policy development focusing on removal of this chronic human carcinogen. In the present study, the potential use of shell particles of crab (Portunus sanguinolentus) for removal of arsenic(V) from aqueous solution was investigated on the basis of systematic equilibrium and kinetic studies. Crab shells favor the removal of arsenate ion, especially under acidic pH conditions, because of the presence of CaCO3 and chitin in the biosorbent. The scanning electron micrographs together with energy dispersive X-ray analysis (EDX) confirmed the presence of arsenic on the crab shells. A series of isotherm experiments conducted at different pH conditions revealed that pH 3 favored arsenic biosorption. Among the four isotherm models (Langmuir, Freundlich, Redlich-Peterson, and Toth) employed in the study, the Toth model provided a better fit with the experimental data than others as revealed by high correlation coefficients, low % error, and root-mean-square error (rmse) values. The arsenic biosorption kinetics was very fast, and the kinetics data were successfully modeled using nonlinear pseudo-second-order model. As the ionic strength increased, arsenic uptake declined to a great extent. Desorption experiments were conducted to explore the feasibility of regenerating the biosorbent for further use. Results indicated that 0.1 M NaOH was sufficiently strong to remove the biosorbed arsenate ions from the crab shell with elution efficiency of 98.2%. © 2009 American Chemical Society.