Anion exchange material based on polyvinylchloride and urea for the removal of chromium(vi) ions from aqueous solutions

Abstract

In this study, an anion exchange material obtained by chemically modifying granulated polyvinyl chloride with urea was examined. To study the structural morphology of the anion exchanger, polymer PVC-based anion exchange resin second type (PPE-2), we applied different characterization techniques including X-ray diffraction (XRD), Fourier-transform infrared (FTIR), scanning electron microscopy (SEM), and water vapor adsorption analysis. Moreover, PPE-2 was used to remove hexavalent chromium ions from aqueous media. A pseudo-second order model was used to describe sorption kinetics as well as the adsorption mechanism. The Langmuir isotherm and the pseudo-second order kinetic model led to the most consistent results in describing ion removal from solution. In the case of hexavalent chromium ions, the maximum adsorption capacity was 148.4 mg g⁻¹. The Dubinin-Radushkevich (D-R) free energy of adsorption (E_D) was >16 kJ mol⁻¹, which indicates chemical interaction between the ion exchange material and Cr(VI) ions. The Gibbs energy ΔG, enthalpy ΔH, and entropy ΔS changes during binding showed that the sorption process is spontaneous and involves chemical sorption through endothermic ion exchange reactions. In addition, the results demonstrate that the anion exchanger (PPE-2) very efficiently removed hexavalent chromium ions from industrial wastewater.