Separation And Transformation Of Nickel And Phosphorus In Electroless Plating Wastewater

Due to the wide application of electro less plating technology,a large amount of electro less plating wastewater was produced.The pollutants such as nickel and phosphorus in the wastewater had great influence on the aqueous environment,especially nickel enters into human body could cause disease、cancer and death in all probability.Therefore,the treatment of electro less plating wastewater had become a hot research topic.As a simple and efficient method,chemical precipitation had made some progress in the treatment of electro less plating wastewater.However,this method had some problems such as complexes cannot be completely processed,large amount of waste residue and low recovery and utilization efficiency.Therefore,based on the chemical precipitation method,applied the pretreatment method of decomplexation method to solve the complex.For solving the waste residue problem,nickel was recovered in the form of nickel hydroxide colloid by adjusting the reaction conditions.In order to improve the purity of nickel hydroxide,the colloid was dried by solvent displacement.During this study,the reaction conditions were adjusted by using the decomplexation method and controlling variables,so as to achieve the optimization of nickel removal effect.The results showed that,ammonia to nickel with a ratio 1:1 in 50ml simulated liquid system,1 mL NaClO decomplexing 30 min,added 6 mol/L 6 mL NaOH solution,adjusted the solution pH to 9.5,reaction temperature of 30℃,and 500 r/min under the reaction conditions of reaction 8 h,then aged 8 h to get the fluid(water)solid(gel)two phase system,nickel ions removal rate can reach 99.9%,which meet the national discharge standard GB21900-2008 of nickel content was less than 1.0 mg/L.Based on the above reaction principles and phenomena,the gelation imaging diagram was constructed through the change of reaction process parameters to explore the factors affecting the gelation amount in different systems.The gelation amount and nickel removal efficiency of different systems were expressed in phase diagrams to establish the optimal reaction and separation parameters.The results showed that,the decomplex of pH was 9.51,temperature was 30℃,per litre of H2PO2-was 0.2 mol、HPO32-was 0.8 mol、HEDP was 0.02ml、C6H8O7·2/3Ni was 0.06 mol reached the minimum colloid content of about 39%under the condition.And the actual wastewater was tested,the nickel content in the treated wastewater was 0.1915 mg/L,which was in line with the national discharge standard GB21900-2008 and less than 1.0 mg/L.Colloid volume accounted for 31.1%of the total volume.Finally,XPS,XRD,ion chromatography,FT-IR spectro scopy and other modern analytical techniques were used to analyze and characterize the gel products processed by three different drying methods:ethanol solvent displacement,freeze drying and room temperature drying.The results showed that solvent displacement drying could protect the internal structure of nickel hydroxide powder to the greatest extent,and rapidly and efficiently recover the nickel hydroxide powder with purity over 94%.