Preparation, characterization and performance of nanofiltration membranes for the treatment of electroplating industry effluent

Two new nanofiltration (NF) membranes were prepared by coating (cast and spray) of strong chelating agent diethylene triamine pentaacetic acid (DTPA), using polyether sulfone (PES) ultrafiltration (UF) membrane as substrate and their performance were studied to treat actual electroplating industry wastewater. The resulting membranes, observed to be nanofiltration membranes, were characterized with the help of scanning electron microscopy (SEM) and swelling behavior. The structure of sprayed membranes was observed to be more porous than that of cast membranes and hence, the sprayed membranes gave higher permeation rate than that of cast membranes. Effects of pressure, feed flow rate, feed pH, and concentration of DTPA on the rejection of zinc and iron were investigated. The rejection was higher for cast membrane when compared to spray membrane. The maximum observed rejection for cast and spray membranes was found to be 94% and 89% for zinc and 93% and 88% for iron, respectively. The rejection of SS and TDS was over 99.4%. From the experimental results it was evident that as pressure, and feed flow increased, the observed rejection of both the metal ions increased. Also, it was observed that the feed pH had great effect on permeate flux but marginal influence on observed rejection for both ions.