To effectively recover useful components from the sludge formed at the time of acidic halogen tin electroplating and to effectively decrease the amt. of solid waste.
The raw sludge formed at the time of acidic halogen tin electroplating is separated by a water leaching treatment to a soln. contg. sodium fluorostanate (IV) and blue sludge contg. iron ferrocyanide and sodium fluoroferrate (III). The white sludge contg. tin hydroxide or tin oxide is precipitated and separated by adjusting the pH of the soln. to >7. After this white sludge is dried, the white sludge is reduced and the metal tin is recovered. The sodium fluoride included in the soln. is recovered as sodium hydrogenfluoride by the pH adjusting treatment to lower the pH of the soln. contg. the sodium fluoride after the adjustment of the pH to >7 to 2.0 to 5.0.
YAMAMOTO YOSHIHIDE
HAMAGAMI KAZUHISA
OKAWA YOSHIHIRO
