メッキ廃液からの有価金属の回収に関する研究 Ｉ 化合物沈澱法によるＮｉの回収

Abstract

Since Ni is a valuable resources and its plating solution is costly, improvements in recycling technique from waste solution and slurry in the Ni plating process have been an necessity. In this paper, the retrieval of Ni from the electroless plating waste waters, especially worn-out ones with high concentration of Ni is considered. The compound precipitation method which retrieves Ni from waste waters as carbonate form or oxalate form is examined.The results show that higher solution temperature is preferable, and that Fe can be removed by neutralization precipitation. Among carbonate, Na2CO3 turns out to be the more effective precipitator than NaHCO3. When the double dose or more of the theoretical equivalent of Na2CO3 were added, and the initial pH was larger than 2, precipitation took the form of weak crystalline whose composition was Ni(CO)3(OH)4 · 4H2O. When NaHCO3 was used as precipitator, together with CO2 bubbling, globular particles precipitated.For oxalate, crystalline particles of NiC2O4 · 2H2O precipitated. The method was tested for waste water from an actual plant and followings were suggested: Ni-B solution should be precipitated with carbonate, while Ni-P solution with oxalates.