| 摘要 |
PURPOSE:To recover easily a fine suspended gold compd. in the form of a coagulated lump by adding an aq. soln. of sodium borohydride under specific conditions to a waste liquid of gold plating, adding a specific neutral flocculating agent and settling the gold compd. CONSTITUTION:A reducing agent is prepd. by dissolving 0.5-2wt% sodium borohydride into 98-99wt% water. Such reducing agent is added to the waste liquid of gold plating consisting of an aq. soln. contg. mainly potassium gold cyanide and is stirred in such a way that the reducing agent is contained at a rate of 7-15ml with 0.1g gold contained in the waste liquid. A neutral flocculating agent (about 30-70% zinc sulfate with respect to 1-18% dilute sulfuric acid) consisting of an amphoteric metallic salt which is not reduced by sodium borohydride such as zinc sulfate and an aq. dilute sulfuric acid soln. is dropped to the waste liquid under stirring until pH attains 7-4. The waste liquid is then allowed to stand and after 10min, the supernatant part is removed and the settled gold compd. is drawn. The gold compd. is dried and filtered to the single substance of gold.
|
