| In recent years, electroless plating has been widely used in surface treatment industry due to its unique characteristics. On the other hand, it is harmful to the environment owning to complicated composition and high pollutant concentration. This paper discusses the recovery and treatment of glass fiber electroless Ni-W-P and Ni-Co-P plating bath with chemical precipitation and wadding coagulation, and it gets good results.Sodium hypophosphite is used as reducing agent for electroless plating Ni-W-P and Ni-Co-P. During electroless plating, phosphite ion and sulfate ion accumulate gradually in reaction process. When their concentration reaches a certain level, the reaction could not continue and the plating bath has to be discarded. If it were drained directly, many valuable components would be wasted, and the worst thing is, these ions pollute the environment seriously. Hence over drainage is strictly forbidden in our country and the bath must be purified to conform the corresponding state standard before it is drained.In order to cutting down the cost and making full use of resources, the harmful phosphite ions and sulfate ions are removed, and the useful ingredients nickel, tungsten, cobalt, hypophosphite and organic acid ions are reserved significantly. In the experiment, calcium acetate is used as the precipitator of phosphite ion and sulfate ion, and the residual calcium is removed with sodium fluoride due to the low solubility constant of calcium fluoride. Then feeding effective agents into the plating bath and plating on glass fiber. It can be seen glass fiber dispersing very well in the regeneration bath, and the layers are produced uniformly and the electrical conductivity is improved. The paper also presents the effect of CaO and Ca (OH)2 to plating bath. It finds that CaO brings high pH value and removes phosphite ion and useful heavy metal at the same time;furthermore, high pH value results in decomposition of the plating bath. |
PDF Full Text Request