Experimental Study On The Treatment Of Nickel-cobalt Battery Wastewater By Physical And Chemical Methods Reactors

Nickel-cobalt battery wastewater mainly includes wastewater of cleaning slurry from the battery production line, pharmaceutical wastewater leakage of allocation of slurry spill, wastewater of cleaning the ground. Nickel and cobalt ion content in wastewater is high, several times more than the allowable emission standards. Nickel and cobalt ions will be retained, accumulated and migrated. Heavy metals, even small concentrations, can accumulate in the surface of fish and shellfish by adsorption, into the food chain cycle, resulting in pollution.This test uses physical and chemical methods treating nickel-cobalt battery wastewater and it researches the treatment effect of coagulation sedimentation process and try to master the best experimental conditions. At first, it uses sodium hydroxide, sodium carbonate and sodium sulfide as precipitant to treat nickel battery wastewater in order to determine the best precipitant. And then it investigates treatment effect by single factor analysis and orthogonal experimental study of various reaction factors, and the dosing sequence of precipitant and flocculant to find the best conditions. Finally it researches treatment effect for wastewater of different concentrations to provide the basis datas for wastewater treatment.The result of laboratory experiment indicated that NaOH is optimum for precipitant and PAC+PAM is the best coagulant and the suitable feeding sequence is feeding NaOH before PAC+PAM. When the concentration of Ni2+ is 500mg/L and the concentration of Co2+ is 120mg/L in the wastewater, the best reaction condition:pH=11.5, PAM quantity=1mg/L, PAC quantity=1mg/L, rapid mixing time=4min, mixing speed=360r/min, slow mixing time=10min, mlxing speed=60r/min, settling time=30min. In this reaction condition at room temperature, the removal rate of nickel and cobalt ions can reach more than 99.6%, so nickel and cobalt ion content in water is up to the national emission standards. But it can not separate nickel and cobalt precipitation by such methods, and it needs to be isolated by other methods. According to the principle of thermodynamic equilibrium, the solubility of Ni(OH)2 is least at pH range of 10 to 11. The diagram for the conditional solubility product pPs-pH indicates that the pPs reaches minimum at the pH range of 9 to 11. Experimental data shows that the optimal pH 11 for treating nickel wastewater with the same theoretical value and 11.5 for treating nickel-cobalt mixed wastewater,so it is in error range.