Experimental Study On The Treatment And Recovery Of Nickel Containing Wastewater By Electrolysis

With the development of metallurgical avionics,electroplating has become the most widely used surface treatment technology.Electroless nickel plating can provide gloss and corrosion-resistant coatings for various conductors and insulators with excellent uniformity,wear resistance,corrosion resistance,and stability.But at the same time,a large number of electroless nickel plating wastewater with high toxicity,strong stability,and difficult biodegradation will be produced.If directly discharged into the natural environment,nickel will migrate to the soil environment along with the water environment,damaging the ecological balance and soil structure.It enters the human body via the food chain.When the body ingests too much nickel,it can irritate the stomach and intestines,causing diarrhea.Produce pathological changes to the nerve,blood,brain,and other organs,and even induce cancer.In electroless nickel plating wastewater,nickel exists in the form of a complex,and the removal effect of nickel by the traditional process is not good.Therefore,in this paper,the actual electroless nickel plating wastewater was taken as the target pollutant,and the treatment effect of the electrocatalytic collaborative electrodeposition extraction method on actual electroless nickel plating wastewater was studied.On this basis,small-scale and pilot-scale experiments were carried out to determine the optimal processing parameters.The research content and results of this paper are as follows:（1）Firstly,Electrocatalytic oxidation and electrodeposition were used to treat wastewater from electroless nickel plating,and an efficient and stable electrochemical system was established to recover nickel from wastewater from electroless nickel plating.In addition,the influence of initial p H value,current density,and initial nickel ion concentration on the performance of the electrochemical system was studied.The results showed that the complex was broken and nickel recovery was realized by an electrocatalytic collaborative electrodeposition system.When the current density is 83.3 m A/cm~2,the initial p H value is 3.0,and the initial nickel ion concentration is 0.01 M,the nickel recovery rate and TOC removal rate are 94.84%,and 63.94%,respectively.The cathode recovered product was characterized by scanning electron microscopy（SEM）energy dispersive X-ray（EDS）X-ray powder diffraction（XRD）X-ray photoelectron spectroscopy（XPS）.The results showed that the recovered product was an elemental nickel.It was confirmed that the nickel recovery rate remained above 95%and the TOC removal rate remained unchanged after six consecutive cycles of electrocatalytic oxidation and electrodeposition system.In addition,the energy consumption of recovering 1.0 g nickel under the optimal conditions is 0.05×10^-3 k Wh/g and the cost is 64.113 yuan/kg.（2）Practical electroless nickel plating wastewater was treated by extraction and electrodeposition.The effect of reaction time,initial p H value,dosage of extractant,and reaction temperature on nickel extraction rate was investigated.The experimental results show that the dosage of extractant and the initial p H value of wastewater have significant effects on the extraction effect,while the reaction temperature has no obvious effect on the extraction effect.When the amount of extractant was 80 m L and the initial p H value was 6.0,the nickel extraction rate was the best after 15 min reaction at room temperature.In addition,GC-MS and FT-IR were used to analyze the components of the extractant before and after the reaction,which proved that the extractant had a good life cycle without secondary pollution.About 98%of the nickel is recovered during electrodeposition.The recovered products were analyzed by XRD,SEM,and XPS.The results show that the main element in the cathode sediments is Ni、O and P,and nickel exists in the form of zero valences.In the electrodeposition process,Ni²⁺reacts with OH^-to form Ni（OH）₂,which is gradually reduced to metallic Ni.（3）The main technological parameters of the electrocatalytic oxidation collaborative electrodeposition process were studied by pilot-scale test.Under the condition that the current is 20 A and the initial p H is 3.0,the nickel recovery remains above 90%after 180 min,and the concentration of nickel ion in the effluent is between 80 mg/L and 130 mg/L.In the pilot test,the electrocatalytic collaborative electrodeposition system has strong stability,and the process runs well.It not only realized the efficient recovery of nickel in the wastewater but also met the nickel ion concentration at the outlet of the sewage treatment plant in the park.