Nature of sorption of trivalent arsenic on novel iron oxyhydroxide stabilized starch/OMMT composite: A mechanistic approach

Abstract

Materials which are chemically, energetically and operationally acceptable for arsenic water treatment are highly required. In this study a hybrid material (SICC) of aminated starch, oxyhydroxide of iron and OMMT clay has been demonstrated for arsenic treatment. This new material was highly efficient in arsenic water treatment which could reduce arsenic concentration far below detection limits. All binding interactions during material preparation and arsenic sorption were exclusively characterized with FT-IR, XRD and other spectroscopic tools. A molecular modeling on the basis of density functional theory was carried out to verify the above findings. Influence of material dose, treatment time, initial ion concentration, varying temperatures, etc., on extent of sorption was studied in detail. The thermodynamic parameters viz. ΔG (>–11 kJ/mol), ΔH (42.48 kJ/mol), ΔS (177.6 JK−1 mol−1) and E a (59.16 kJ/mol) determined the feasibility of the process, its endothermic behavior and most importantly the chemical nature of the sorption accompanied by ion-exchange to some extent. The sorption followed a monolayer chemisorption pattern as determined by the Langmuir model (R2 = 0.973, R L = 0.081) with a qmax = 2.04 at 303 K. The binding of As(III) on the material was governed by a pseudo second order kinetic model. HIGHLIGHTS Properties of the hybrid material were enhanced synergistically.; Suspended materials were negligibly small in hybrid material.; Material with 10% clay loading accompanied by Iron(III) oxyhydroxide stabilization was found best in all respects.; Arsenic on SICC was predominantly chemisorbed accompanied by ion exchange to some extent.; The sorption process was spontaneous and endothermic in nature.;

Keywords

• chemisorption
• endothermic
• feasibility
• hybrid material
• molecular modeling