抄録
Electrolytic treatments have been widely conducted for concentrated cyanide waste solutions, but for diluted waste solutions only to a minor extent. This study has been made of an electrolytic treatment of residual copper cyanide in the second rinse water from a cyanide bath in a continuous circulation system. The plating solution contained 39g/l Cu (as metal), 82g/l NaCN (free), 30g/l NaOH and a small quantity of a brightener. The electrolysis was carried out using a graphite anode and a copper cathode under the conditions of DA of 0.15A/dm2 and DK of 0.15A/dm2, a bath temperature of 40°C and a circulating influx rate of the second rinse water of 180l/h. When the rate of dragout from the plating solution was about 1.2l/h, average concentrations of copper and cyanide in the second rinse water during continuous circulation (electrolysis) were about 130mg/l and 280mg/l respectively, which were about 1/40 and 1/25 of those in the first rinse water. This showed that dischaged substances were reduced to less than about 1%. The electric power consumption was about 60kWh/month. This type of rinse water did not have an adverse effect on the plated products over a long period in continuous use. Insufficent agitation of the second rinse water, however, produced stain on the products, presumably due to the high concentration of alkaline substances. Therefore, the removal of alkaline substances from the second rinse water by electrodialysis and improvement in durability of the anode could make this method practical.
