Removal of nickel from electroless nickel plating rinse water with di(2-ethylhexyl)phosphoric acid-impregnated supports

Electroless nickel plating technology is playing an increasingly important and indispensable role in many fields such as the electronic and automobile industries. As a result, the treatment of the rinse water containing about 50mg/dm(3) of nickel is becoming a serious environmental problem. Although this water is currently treated by the conventional precipitation method, a method without sludge generation is highly desired. This study explores the possibility of removing and recovering nickel from the rinse water with di(2-ethylhexyl)phosphoric acid-impregnated supports (D2EHPA-IS). Macroporous polymer and oil adsorbents made of synthetic and natural fibers as the supporting materials were tested for the nickel removal abilities from simulated rinse water. In the batch experiments, more than 90% of the nickel can be adsorbed by these D2EHPA-IS without pH adjustment. The adsorption of nickel reaches the equilibrium within 1.2 ks at 298K at a shaking rate of 140 rpm. The pH-dependency of the nickel adsorption by the D2EHPA-IS shows that the nickel is adsorbed by a cation exchange reaction. The adsorbed nickel can then be readily eluted with mineral acids. Most of the IS can be used many times without losing their adsorption abilities. In the column experiments, the breakthrough curves of nickel for these supports indicate that the nickel-D2EHPA complex formed at the high nickel loading region tends to dissolve into the aqueous phase. These findings lead to the conclusion that most of the studied D2EHPA-IS are effective for the removal and recovery of nickel from an electroless nickel plating rinse water in batch mode.