Abstract
The discharge of strongly acidic industrial wastewater containing high concentration of chloride ions (Cl(-)) has become one of the major environmental challenges faced globally. For the removal of extremely stable Cl(-) in acidic aqueous conditions, precipitation method possesses major advantages of strong adaptability and simple operation. This study proposed a novel cuprous oxide (Cu(2)O) method assisted by ascorbic acid (VC) for the removal of Cl(-) from strongly acidic wastewater. First, liquid-phase reduction was chosen as the optimal Cu(2)O synthesis method based on product purity and composition. Then, parameter optimization results show that increased reagent dosage and acidity significantly enhanced Cl(-) removal efficiency, while other factors had negligible impacts. After treatment with the sole addition of Cu(2)O, the dosed Cu(2)O existed in four forms, including cuprous chloride (CuCl), copper ion (Cu(2+)), elemental copper (Cu(0)), and Cu(2)O, among which the generation of Cu(2+) and Cu(0), through the oxidation and disproportionation of cuprous ion (Cu(+)), served as the main reason for the unsatisfactory efficiency in the removal of Cl(-). Fortunately, VC is precisely capable of inhibiting the side reactions of Cu(+), and under the assistance of 0.10 g VC, the removal of Cl(-) by Cu(2)O was greatly improved with the multiple of theoretical reagent dosage decreasing from 12 to 3, the residual concentration of Cu(2+) decreasing from 1197 to 18.4 mg/L and the residual concentration of Cl(-) decreasing from 88.4 to 53.8 mg/L, thus validating the feasibility of this method.