Reductive Adsorption of Chromium(VI) by Coal-Based Activated Carbon

抄録

Cr(VI) has been confirmed as a toxic carcinogenic contaminant; consequently, it must be removed from wastewater pipes prior to discharge. In the present work, the reductive adsorption of Cr(VI) was investigated using coal-based activated carbon. Batchwise reductive adsorption and chromatography study of Cr(VI) were carried out, with varying parameters, such as pH, time, initial concentration, and temperature. The Cr(VI) species adsorbed on the activated carbon were immediately reduced to Cr(III), such that only Cr(III) was observed. The reductive adsorption followed the Langmuir adsorption model, and the highest adsorption capacity of 3.43 mmol g⁻¹ was obtained at an equilibrium pH of 2.04. Thermodynamic studies indicated that the adsorption process was endothermic. The reductive adsorption kinetics were controlled by the adsorption step and expressed by the pseudo-second-order kinetic model. The chromatographic recovery of Cr(VI) using the activated carbon was achieved at a feed pH of 3.0 until a bed volume of 500 was achieved, although the elution of the loaded Cr was difficult.