Effect of surface modification of microfiltration membrane on capture of toxic heavy metal ions.

A novel complexing membrane containing 8-hydroxyquinoline groups was used for the removal of heavy metal ions (Cd2+ and Ni2+) from aqueous solution. The functionalized membranes were characterized by FTIR-ATR, SEM and EDAX for the presence of functional groups, the physical structure of the membranes and the analysis of the particles deposited on the membrane, respectively. The influence of 8-hydroxyquinoline concentration, feed concentration, pH and temperature of the solution on capture capability was studied. The modified membrane showed a higher affinity to Cd2+ cations than to Ni2+. The metal ion rejection was increased with an increase in concentration of 8-hydroxyquinoline from 0.5 to 2.0 wt%. However at a ligand concentration higher than 2.0 wt%, no significant change was observed in the metal rejection. The experimental results revealed that the metal rejection was decreased with an increase in metal ion concentration in the feed. Moreover the rejection depended on feed pH and is higher for elevated pH. By changing the temperature in the range of 23-28 degrees C, no considerable effect on metal rejection was observed. However, a higher temperature resulted in a decline in metal rejection. For filtration of a mixture of the two metal ions, the retention was similar to that of the single cations, i.e. Cd > Ni but with smaller absolute rejections.