Experimental study on treatment of electroplating wastewater by nanofiltration

Nanofiltration (NF) was investigated for the treatment of an electroplating rinse wastewater containing Cu and Cr. Three NF membranes, DL, DK, and NTR-7450, were used in the experiment. Effects of pressure, temperature, and feed pH on membrane performance were investigated. With the rise of pressure, flux decline with time for DL and DK membranes was obvious. Flux of NTR-7450 membrane was stable at different pressure in the experiment. With the increase of pressure, the Cr and Cu rejections of three NF membranes increased slightly. With the rise of temperature, the permeate flux increased and rejections of Cr and Cu did not change obviously in the scope of this experiment. The change of flux with feed pH was not great generally. The permeate flux was minimum around the isoelectric points of the membranes. The Cr and Cu rejections for the feed with pH more than 7 were greater than that for the feed with pH less than 7. In the latter stage of the NF concentration process, flux decline behaviors of membranes were obvious. Stability investigation results showed that DK membrane had better stability in the raw electroplating wastewater with pH 2.32 than DL membrane.