ＬＩＸ８４Ｉを用いた溶媒抽出法による使用済み無電解ニッケルめっき浴からのニッケルの分離回収

Abstract

In order to recover nickel ion in a spent electroless nickel-phosphorus alloy plating bath and, at the same time, to remove impurities such as iron and zinc, the applicability of solvent extraction with LIX84I as the extractant has been investigated using actual spent bath. Although the extraction efficiency of nickel from the spent bath is considerably lower than that from the nickel sulfate-nitrate solution, nickel in the spent bath is selectively extracted with high efficiency (> 99 %) at the pH of 6-7. The extracted nickel is effectively stripped by sulfuric acid at a pH of less than 3. On the basis of these results, a flowsheet for recovering nickel from the spent bath is proposed. Chemical equilibrium calculations of the spent bath have shown that the complexes of nickel with anions such as lactate and phosphonate ions become predominant in the pH range between 2 and 6. This results in the depression of nickel extraction efficiency from the spent bath as compared with that from the nickel sulfate-nitrate solution. By combining these aqueous equilibrium calculations with the extraction equilibrium and the successive aggregation equilibria of the active component of the extractant in the organic phase, the extraction behavior of nickel is quantitatively predicted.