| 摘要 |
<p>PURPOSE:To lower silver concentration in waste water after clarified, while recoverying silver with a high yield rate, by adding a halogenic axydizing agent to photographic waste water and then treating the waste water with active carbon. CONSTITUTION:A halogenic oxydizing agent, e.g. sodium hyprochlorite, is added to photographic waste water so as to raise an oxidation-reduction potential at a level higher than about 300mV, to oxidize and decompose complex ions such as silver thio-sulfuric ion in the wasre water and to form precipitate of colloidal silver halide. Thereafter, the silver halide is adsorbed to active carbon. The active carbon is then roasted to convert the adsorbed silver halide into raw metallic silver. Silver is recovered from the raw metallic silver by refining. According to this method, silver can be economically recovered with a high yield rate, and silver concentration in the clarified waste water can be reduced at a lowered level of about 0.3ppm or less.</p> |
