The removal of Cl− from acidic wastewater by Cu2+/VC: Through reduction & precipitation function

Nowadays, recycling as the material for industrial sulfuric acid (H2SO4) has become the development trend for the treatment of the acidic wastewater containing H2SO4. To ensure the quality of the recycled H2SO4, the impurities need to be pre-removed, among which chloride ion (Cl−) is still a big issue. In our previous studies, several methods for the removal of Cl− were proposed, however, a limitation of the requirement for the high concentration of H2SO4 remains to be solved. In this work, an approach for the removal of Cl− by copper ion (Cu2+) and ascorbic acid (VC) from the wastewater containing low concentration of H2SO4 was systematically studied. The removal efficiency of Cl−, the mechanism and the application to the actual wastewater were successively explored. For the wastewater with the H2SO4 concentration below 15 g/L, a Cl− removal efficiency above 85 % was always obtained at the mole ratio of Cu2+, VC and Cl− of 3.5:0.75:1 under room temperature. During the removal of Cl−, Cu2+ was firstly reduced by VC to produce cuprous ion (Cu+), which precipitated with Cl− rapidly, leading to the effective removal of Cl− in the form of cuprous chloride (CuCl).