Improving separation capability of regenerated cellulose ultrafiltration membrane by surface modification

In this study we introduced dialdehyde groups to a commercial regenerated cellulose (RC) ultrafiltration membrane by periodate oxidation. They were further converted to nitrogen-containing derivatives by Schiff base reaction with diethylenetriamine (DETA). The modified membrane was challenged with aqueous solution containing Pb(II) metal ions. The different variables affecting the rejection of lead ion by membrane including oxidization time, concentration of DETA, initial metal ion concentration and pH of the solution were elucidated. The membranes were characterized by FTIR-ATR, SEM, EDAX and elemental analyses. The process efficiency was enhanced by improving the oxidization time up to a certain period. In our case this was diminished after 9 h due to deterioration in the membrane integrity. The Pb2+ removal was facilitated by increasing feed pH and DETA concentration. This was diminished for more concentrated metal ion in the feed. Membrane regeneration was successfully utilized using 0.1 M HNO3 solution. The removal capability of the regenerated membranes was maintained even after four cycles.

Research highlights▶ Functional groups were introduced to ultrafiltration membrane by oxidation. ▶ Rejection and flux were improved up to a certain oxidization time. ▶ Longer oxidation time resulted in membrane degradation leading to lower rejection. ▶ The removal of Pb2+ was improved with pH increment. ▶ The removal capability was maintained even after four cycles.