Removal of phosphite and sulfate from electroless nickel-phosphorus plating bath with hydrotalcite for the management of watershed

This study was focused to remove both HPO32- and SO42- for the improvement of efficiency in electroless nickel- phosphorus plating process with hydrotalcite- like compound ( HT). The adsorbed amount, q(e), of H2PO2- which was main component was low and H2PO2- had little influence on the adsorption of HPO32- and SO42-. HPO32- and SO42- were similar in the adsorption behaviors of the adsorption isotherm and the influence of solution pH. The q(e) was increased with the increase of water temperature, because the CO32- was decreased with the increase of water temperature. On the coexisting adsorption, the q(e) of HPO32- was decreased with SO42-. The ion selectivity of HT was in the order of SO42- > HPO32- > PO43- >> H2PO2- at pH 10. The results indicated that the HT- Cl is a useful adsorbent for HPO32- and SO42- removal in the exhausted electroless nickel- phosphorous plating bath.