Treatment of metal-plating waste water by modified direct contact membrane distillation

Abstract

In this study, the treatability of metal-plating waste water by modified direct contact membrane distillation (DCMD) at different temperature differences (Delta T = 30 degrees C, 40 degrees C, 50 degrees C, and 55 degrees C was investigated. Two different hydrophobic membranes made of poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) having different pore sizes (0.22 mu m and 0.45 mu m) were used. The results indicated that conductivity, COD, sulphate, copper, and nickel could be successfully removed by modified DCMD. The rejection efficiencies for conductivity, COD, and sulphate were 99 %, 86 %, and 99 %, respectively. Copper rejection was effective with both membranes while nickel concentration was below the limit of detection in the effluent. It was found that the pollutant rejection efficiency was affected by the raw water characteristics, membrane properties, and influent heating temperatures. In addition to the water quality parameters, the flux was measured to evaluate membrane performance. A high flux was obtained at 65 degrees C (Delta T = 55 degrees C) with 0.45 mu m pore size PTFE membrane (24.1 L m(-2) h(-1)) and with PVDF membrane (17.1 L m(-2) h(-1)). The flux was mainly affected by temperature and membrane properties. As a result, modified DCMD and all the membranes used in this study were effective for the treatment of metal-plating waste water. (c) 2016 Institute of Chemistry, Slovak Academy of Sciences