Modified activated carbon loaded with bio-synthesized Ag/ZnO nanocomposite and its application for the removal of Cr (VI) ions from aqueous solution

Abstract

Chromium (VI) is recognized as a highly toxic contaminant metal ion, due to its potential toxic effect to human and animal health. From the most common processes applied for Cr (VI) ions removal is the sorption process hence it has been highly efficient and inexpensive technique. In the present work, a bio-synthesized Ag/ZnO nanocomposite loaded on activated carbon as a new eco-friendly and effective sorbent for the removal of Cr (VI) ions. The modification of activated carbon confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The optimum conditions for the uptake of Cr(VI) ions by Ag/ZnO-AC was found to be at pH 2.5, shaking time 60 h, Cr (VI) ions concentration of 40 ppm, and 0.4 g sorbent dose. The results indicated that sorption process optimally correlated with Freundlich isotherm and pseudo second order kinetic models. The values of ΔG° are negative at all studied temperatures (-0.55, -1.18, -2.43, -3.68, -4.93 and -7.43 kJ. mol−1) suggesting that the sorption process is spontaneous. The positive values of ΔH° (36.7 kJ. mol−1) and ΔS° (0.125 kJ. mol−1) indicate the endothermic and physisorption nature of the sorption process. The results demonstrated that Ag/ZnO-AC can be used as a potential sorbent for the uptake of Cr (VI) ions.