Desalination of water with a high degree of mineralization using SiO2/PVDF membranes

The performance of a SiO2/PVDF ion-exchange membrane (IEM) prepared in our lab has been evaluated in this work. Desalination experiments were conducted to determine the optimum operating conditions of an electrodialysis (ED) system. The effect of voltage and flow rate on the performance of the SiO2/PVDF membranes was obtained. This was compared with the PVDF IEM employed for the treatment of ultrafiltration effluent of the polymer flooding wastewater with its high degree of mineralization from the Daqing oil field in China. It was found that there were higher energy consumption and longer desalination time for the PVDF membranes compared with the SiO2/PVDF membranes at the same operating conditions. At an applied voltage of 8 V and the optimum flow rate of 25 L/h, the removal ratios for K+, Na+, Mg2+, and Ca2+ by electrodialysis with SiO2/PVDF membranes were 97.8%, 95.8%, 93.5% and 92.5%, respectively, and the corresponding removal ratios for Cl-, F-, HCO3- and SO42- were 95.4%, 94.2%, 92% and 90%, respectively. This study demonstrates that electrodialysis in the presence of SiO2/PVDF IEM is an effective method for the removal of ions in polymer flooding wastewater after ultrafiltration. (c) 2012 Elsevier B.V. All rights reserved.