Purifying condensed water with ceramic ultrafiltration membranes

Background: High-temperature condensed water has high recoverable value but it contains iron ions and oil, which need to be removed before use. Ceramic membranes with pore size between 4 and 50nm were selected to purify the high-temperature condensed water. The effects of operating parameters and membrane structure on the separation performance were investigated. Continuous concentration experiments were conducted to evaluate the influence of volume concentration factor (VCF) on membrane permeability. Results: The membrane exhibited high rejection of iron ions and oil. With increase of iron ions concentration, the permeate flux gradually decreased but the oil rejection increased. Oil concentration had no significant effect on the rejections of iron ions and oil. However, the permeate flux decreased with oil concentration owing to the formation of a thick fouling layer on the membrane surface. In the continuous concentration process, removal efficiencies of iron ion and oil were more than 99%, and the turbidity and oil concentration in permeate were less than 0.5 NTU and 0.5mgL^-1, respectively. The iron ion concentration in permeate was less than 0.3mgL^-1. These results meet the standards for boiler feedwater. Finally, the ceramic membrane was washed with 1vol% HNO₃ and then with 1wt% NaOH. Pure water flux was recovered at >95%. Conclusion: This study showed the feasibility of purifying high-temperature condensed water using a ceramic ultrafiltration membrane.