| The electroplating sludge are electroplating sediment, which is produced in the process of electroplating, and solid content after wastewater treatment. The electroplating sludge is more harm than electroplating watewaster. It is urgent to solve the problems that how to deal with the sludge, and avoid arbitrary stacking or mishandling to cause more serious secondary pollution, and achieve the resources. The research object in this paper is the nickel electroplating sludge. Through the component testing, the content of nickel in the sludge was 14.63%. The sludge was deserved for resource utilization.Orthogonal test and single factor optimization test were studied, the results showed that effect of heavy metal nickel leaching rate on acid leaching conditions. the main influencing factors of adsorption and desorption of nickel on ion exchange resins and the kinetics of acid leaching and ion exchange adsorption were researched.Sulfuric acid was selected to leach the nickel in electroplating sludge. After orthogonal test and single-factor experiment, the results showed that the highest leaching rate was achieved when sulfuric acid mass fraction was 15%, solid-to-liquid ratio was 1:7, leaching time was 60 min, sludge particle size less than 0.15 mm, and leaching temperature was 20?. Under these conditions, the nickel leaching rate was 96.02%. Electroplating sludge leaching experiment were also magnified 10 times and 40 times, the leaching rate of nickel were still around 95%.The leaching kinetics were analyzed, the results showed that the sulfuric acid leaching process in line with the solid product layer diffusion control model of the unreacted shrinking model, the kinetic equation was 1-2?/3-(1-?)2/3=kDt, the reaction series is 1,the nickel diffusion coefficient for the reaction was K=0.0117×e-3.127/RT, the apparent activation energy was 3.127 kJ/mol. The leaching thermodynamics were analyzed, the results showed that the enthalpy was-1005.2 kJ·mol-1, the entropy was-167.06J·mol-1·K-1, the gibbs free energy was -955.4 kJ·mol-1. The leaching process was an exothermic process and a spontaneous one because the enthalpy and gibbs free energy were both negative.Iron needs to be removed before extraction of nickel because of the leach liquor contains a lot of iron. The SI-2 resin and SIAP resin were used to remove iron ions. The results showed that the optimum absorption conditions of SI-2 resin were listed as follows:adsorption equilibrium time 80min, pH 1.5, adsorption temperature 20?.Under these conditions, adsorption capacity of nickel was 35.00 mg/g. The optimal conditions of SIAP resin were achieved when adsorption equilibrium time 40min, adsorption temperature was 20?, saturated adsorption capacity of nickel was 35.00 mg/g.SI-2 resin was selected as the adsorption material to extracted Ni2+ from the leach liquor. The results of the static adsorption showed that best adsorption pH was 5, adsorption time was 100 min, temperature was 20?, saturated adsorption amount was 3000 mg/g. The optimum desorption conditions were:hydrochloric acid was the eluent, the concentration was 4mol·L-1, time was 80 min, elution rate at about 93%.The adsorption kinetics was studied, the results showed that The adsorption kinetics fit the pseudo-second-order equation well, the linear correlation coefficient more than 0.99, the adsorption process was controlled by film diffusion, the activation energy was 1.532 kJ/mol.The adsorption thermodynamics was studied, the results indicated that the adsorption isotherm of the Ni2+ on the resin fits the isothermal adsorption model of Langmuir and Freundlich. The constant of Freundlich was between 2 and 3, which illustrated that adsorption process was easier. According to the thermodynamics formula, we can calculate that ?H=3.39 kJ/mol, ?S=73.05 J/(mol·K),?G=-18.38 kJ/mol when the temperature was 298 K. Enthalpy was positive, which indicated that the whole process for the endothermic process. The gibbs free energy was negative, which showed that the adsorption process could occur spontaneously. |
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