Influencing Factors of Nanofiltration for Removing Pb2+ and Cd2+ from Slightly Polluted Water
With the increase of sewage and wastewater discharge,heavy metal ions in drinking water source water exceed the standard from time to time.Due to the unique nature of heavy metal ions,it is difficult to meet the safe drinking water standard by traditional treatment methods.In this paper,a self-designed nanofiltration pilot plant was used to test the removal effects of two nanofiltration membranes VNF-4040K and ESNA1-4040 on Pb2+and Cd2+in micro polluted water by orthogonal test.The power function polynomial was used to fit the test data to characterize the functional relationship between the test indicators and various factors.The effects of influent concentration,conductivity,pH value,membrane flux and recovery on the removal effect of heavy metal ions by nanofiltration were investigated.The test shows that the removal of Pb2+ and Cd2+ by VNF-4040K and ESNA1-4040 nanofiltration membranes are affected by the operating conditions,and the change of influent concentration has a great impact on the removal rate,reaching the highest when the concentration multiple is 1,which are 94.76%,84.49%,97.64%and 95.69%respectively;the membrane flux positively is correlated with the retention of heavy metal ions(Pb2+,Cd2+)by the two nanofiltration membranes;the conductivity and recovery rates are negatively correlated with the removal rate.Alkaline conditions are conducive to the removal of heavy metal ions(Pb2+,Cd2+)by nanofiltration membrane;ESNA1-4040 membrane has better removal efficiency of Pb2+and Cd2+than VNF-4040 K membrane.
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