Isotherm, kinetic and thermodynamics of arsenic adsorption onto Iron-Zirconium Binary Oxide-Coated Sand (IZBOCS): Modelling and process optimization

Abstract

Abstract The aim of this work was preparation and investigation of Iron-Zirconium Binary Oxide-Coated Sand (IZBOCS) for the adsorptive removal of As(V) from water, in both batch and fixed-bed column systems. The batch experiment was performed with As(V) solution of concentration 125 mg/L, at neutral pH, 27 °C temperature by agitating for 120 min and data was fitted in Langmuir, Freundlich, Temkin and Radushkevich isotherms. Langmuir adsorption capacity of IZBOCS for As(V) increased from 45.05 to 84.75 mg/g when temperature of the solution was raised from 27 to 45 °C. Separation factor values, 0.435, 0.489 and 0.508 at 27, 35 and 45 °C indicated feasibility of adsorption process. Dubinin-Radushkevich isotherm gave energy ranging between 0.494 and 0.449 kJ/mol within 27 and 45 °C, indicated physical sorption processes. Gibb's free energy of adsorption came out − 11.391, − 12.255 and − 12.855 kJ/mol at 27, 35 and 45 °C, respectively, and ΔH° was found to be + 12.668 kJ/mol, both indicated spontaneity and endothermic nature. As(V) sorption followed pseudo-second order kinetics, and both liquid-film and intra-particle diffusion process controlled the rate. Column adsorption data was analyzed with Thomas and Yoon-Nelson models to describe dynamic behavior of the adsorption process.