Basic Research On Deep Purification And Resource Utilization Of Nickel Ions In Electroless Nickel Plating Wastewater

Electroless nickel plating is an important surface treatment technology.However,in order to improve the quality of the coating,a large amount of complexing agent,such as ethylenediaminetetraacetic acid（EDTA）,pyrophosphoric acid,hypophosphorous acid,lemon,needs to be added to the plating solution.acid and tartaric acid,etc.As a result,most of the nickel in the wastewater exists in the form of complex complexes,which greatly increases the difficulty of treatment.In view of the strong ecotoxicity of nickel and the shortage of nickel resources,this paper combines quantum chemical calculation and experimental characterization to systematically carry out basic research on the deep purification and resource treatment of nickel ions in electroless nickel plating wastewater based on chelation precipitation and electrolysis.The main conclusions and innovative achievements of this paper are as follows:（1）Quantum chemical calculation,solution chemical analysis and UV-Vis spectral characterization studies show that nickel ions and complexing agents can form stable complexes,among which EDTA has the strongest complexing ability.Drawing on the design theory of flotation reagents and the principle of element geochemical affinity,through quantum chemical calculations and simulated electroless nickel plating wastewater experiments,the optimal nickel chelating precipitants are dithiocarbamates（DTCs）（SDD）.The experimental results of the system’s simulated electroless nickel plating wastewater show that,except for EDTA-Ni,other complex nickels can be efficiently removed by SDD.In addition,after the nickel chelate precipitate is calcined at 400°C,a product with a mass fraction of nickel of more than 30%can be obtained,thereby realizing the resource utilization of nickel.（2）For the most difficult EDTA-Ni,based on the quantum chemical calculation of reaction thermodynamics,a new strategy of"Fe³⁺substitution-SDD chelation precipitation"is proposed.The EDTA-Ni wastewater test proves that this strategy can indeed effectively remove nickel ions,and the residual concentration of nickel is less than 0.1 mg/L,which meets the advanced treatment standard.Mechanism analysis shows that Fe³⁺will spontaneously replace Ni²⁺in EDTA-Ni complex under strong acidity,increasing the percentage of free nickel in wastewater,thereby enhancing the efficiency of SDD chelation to remove nickel.（3）The main influencing factors of electrolysis are anode material,p H value and current density.When electrolysis is used alone to treat electroless nickel plating wastewater,it is difficult to achieve the discharge of nickel up to the standard.