2001 Fiscal Year Final Research Report Summary
Studies on treatment and recycling system for non-electrolytic metal-plating wastes
| Project/Area Number |
12650730
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Metal making engineering
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| Research Institution | Fukui University |
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Principal Investigator |
NAGAOSA Yukio Fukui University, Faculty of Engineering, Professor, 工学部, 教授 (20020224)
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| Co-Investigator(Kenkyū-buntansha) |
HORITA Kiyoshi Fukui University, Faculty of Engineering, Professor, 工学部, 教授 (60020195)
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| Project Period (FY) |
2000 – 2001
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| Keywords | non-electrolytic metal-plating waste / chemical treatment of wastes / metal ion / mixed phosphate salts / recovery of waste materials / recycling system / material separation by precipitation / fertilizer |
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| Research Abstract |
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.
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Research Products
(4 results)
