Treatment of cosmetic wastewater containing N, N-dimethylformamide and high concentration of chloride salt by chemical precipitation and electrochemical method.

High-strength wastewater containing elevated levels of chloride salt and N, N-dimethylformamide (DMF) solvent was collected from manufacturing of sunscreen cream (for UVA/UVB protection) at a cosmetic factory. In evaporation process, precipitates, formed due to the high chloride content (around 160 g/L), clog the pipeline, seriously reducing the treatment efficiency. This study aimed to develop a two-stage process integrating chemical precipitation and electrochemical oxidation to specifically remove the concentrated chloride salt and organic compounds (COD >100 g/L). Chloride ions were initially recovered as insoluble Friedel's salt using calcium hydroxide (Ca(OH)) and sodium aluminate (NaAlO) as the precipitants. The [Cl]/[Ca]/[Al] ratio and solution pH were optimized to obtain a pure crystallized phase of CaAlCl(OH)•2HO. Afterwards, the organic compound were treated by a Fered-Fenton with the addition of HO and FeSO to degrade the remaining COD. The cost and energy consumption of this integrated processes were evaluated, compared to the conventional evaporation method.