The synergistic effect of ultrasound power and magnetite incorporation on the sorption/desorption behavior of Cr(VI) and As(V) oxoanions in an aqueous system

Abstract

Though abundant studies have targeted the sorption of Cr(VI) and As(V) anions by organic polymers or magnetic metal oxides, there is no research literature on the sorption characteristics of Cr(VI) and As(V) by thiourea-formaldehyde resin (TF) and its magnetic derivative (MTF). TF resin is a strong chelating agent, which has several practical applications. This paper reports on the removal of Cr(VI) and As(V) oxoanions by TF and MTF sorbents. The sorbents were characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopy, elemental analysis, zetametry, Brunauer-Emmett-Teller (BET) analysis, and differential light scattering (DLS). The synergistic influence of magnetite incorporation and ultrasonic power on sorption kinetics, isotherms, and oxoanion desorption were investigated, including the analysis of the uncertainty in the study results. The relationship between kinetic and equilibrium constants of the two sorbents under normal shaking and ultrasound shaking was analysed. Ultrasound power improved the mass transfer and makes the sorption ultra-fast while magnetite enhanced the sorption capacity. The MTF particles sorbed 4.28 and 1.97 mmol g−1 of Cr(VI) and As(V), respectively, under optimum conditions. Further, desorption kinetics and efficiency of Cr(VI) and As(V) were estimated using normal shaking and ultrasonic agitation. Ultrasound power reduced the time and the concentration of NaCl required for the stabilization of desorption efficiency.