Studies on treatment and recycling system for non-electrolytic metal-plating wastes

非电解金属涂层技术已广泛应用于镍、铜、金或银等基材的表面沉积。金属电镀液中除所研究的金属离子外，还含有亚磷酸盐（1.2M）、次亚磷酸盐（0.8M）等还原剂。而金属电镀液的还原能力在反复使用后会下降，最终导致电镀液无法使用。另一方面，根据日本环境保护法，废水中总磷酸盐的限量浓度限制在16毫克/升。为了保护环境，需要一种从废水中回收和循环利用磷的技术。本文尝试建立了一种简单快速氧化-沉淀法化学处理金属电镀废料中的亚磷酸盐和次磷酸盐的方法。建议的治疗方法如下：至50。取1 mL废样品溶液，加入25 mL 4M氢氧化钠沉淀Ni (OH)_2。过滤除去沉淀后，加入3M过氧化氢13ml， 0.2M铜溶液0.4 ml， 70℃加热40min，取滤液20.0 ml。滤液中保留的铜离子用Chelex-100树脂吸附分离。因为结果解(5。0 mL)只含磷酸盐离子，加入5.0 mL的1.3M氯化铵和10.0 mL的1.3M氯化镁，加入氨水调节pH 8.3 ~ 8.8。最终形成NH_4MgP0_4沉淀。经过上述化学处理，95%以上的磷酸盐被回收为铵盐，如果得到细粒度的沉淀物，就可以用作肥料。化学氧化过程可能有助于镀镍液的回收技术。从而避免了废弃物的排放，保护了环境。

A non-electrolytic metal-coating technique has been widely used for the surface deposition of nickel, copper, gold or silver etc. onto base materials. The metal electroplating solution contains such reducing agents as phosphite (1.2M) and hypophosphite (0.8M) in addition to the metal ion of interest. The reducing ability of metal electroplating solutions, however, decreases after repeated uses, and finally the electroplating solution becomes unusable. On the other hand, the limit concentration of total phosphate in wastewater is restricted to 16 mg/L according to the Japanese Environmental Protection Law. A recovery and recycling technique of phosphorus from the wastewateris needed to protect the environmental. We have tried to establish a method of chemical treatment of phosphite and hypophosphite in metal plating wastes by using a simple and rapid oxidation followed by precipitation. The recommended treatment procedure is as follows : To 50.OmL of a waste sample solution, 25 mL of 4M sodium hydroxide was added to precipitate Ni (OH)_2. After the precipitate was removed by filtration, 20.0 ml of the filtrate was heated after addition of 13 mL of 3M hydrogen peroxide and 0.4 mL of 0.2M cupric solution at 70 ℃ for 40 min. The cupric ion, which remained in the filtrate, was then separated by adsorption with Chelex-100 resin. Because the resultant solution(5.O mL) contained only phosphate ion, 5.0 ml of 1.3M ammonium chloride and 10.0 mL of 1.3M magnesium chloride was added with ammonia to adjust pH 8.3〜8.8. The precipitate NH_4MgP0_4 was formed finally.As a result of the chemical treatment described above, more than 95 % of the phosphate was recovered as the ammonium salt, which could be used for a fertilizer if the fine particle size of the precipitate was obtained. The chemical oxidation process may be helpful for the recycling technique of a nickel-plating solution used. Thus, the emission of the waste materials to be avoided for environmental protection.