キレート試薬によるニッケルめっき液中の微量銅イオンの選択除去

Abstract

The selective removal of trace copper (II) ion in Watts nickel bath was studied by using chelating reagents, 2-quinolinecarboxylic acid (QA), N-nitroso-N-phenylazanol ammonium salt (CP), 2-mercapto-benzothiazole (MBT), and (2-hydroxylphenylmethylene) azanole (SA). These chelating reagents formed insoluble complexes with copper (II) ion in the bath. Residual copper (II) ion lower than 0.1mg/l was attaind by the addition of MBT or SA, whereas the residual ion was below 5mg/l for QA or CP. Since the chelating reagents have harmful effects on the appearance of nickel deposits, the bath had to be treated with activated carbon prior to use. Amounts of activated carbon, required for reducing the concentration of chelating reagents from 100mg/l to harmless value, 10mg/l, were 0.7, 1.4, 3.0 and 4.0g/l for MBT, SA, QA and CP respectively. Activated carbon modified with the chelating reagent was also useful for the selective removal of copper (II) ion. Additional activated carbon treatment was not necessary, because the desorption of SA from the modified activated carbon into Watts bath was too little to be harmful.