Recovery And Treatment Of Waste Liquid In Chemical Nickel Plating Process

Electrolysis and assisting chemical precipitation are applied to achieve recovering and treating nickel and phosphorus resource of spent electroless nickel plating bath.Electrolysis was adopted to recover the nickel resource. The influences of processing conditions, the direct-current power and the pulse power, different species of DSA anode on the recovery efficiency of nickel and the power consumption were studied. Research showed that the recovery rate of nickel was reduced from 98.93%, the consumed energy was 5.88kWh·kg-1Ni2+ under the conditions of the pH 7, temperature 60℃, agitate, current density 8.0mA·cm-2, Ti/RuO2-TiO2 coating anode, electrolysis time 2h. At the same conditions, when pulse duty cycle is 20%, pulse frequency is 1kHz and pulse electrolysis time 2h using Ti/RuO2-TiO2 coating anode, he recovery rate of nickel was reduced from 99.27%, the consumed energy was 5.00kWh·kg-1Ni2+. While conditions are the same as pulse electrolysis and using Ti/IrO2-Ta2O5 coating anode, electrolysis time 2h, the recovery rate of nickel was reduced from 99.32%, the consumed energy was 4.46kWh·kg-1Ni2+.Heavy metal chelating agent DTCR was induced to removal residual nickel in waste liquid which was treated by electrolysis. Effects of pH, amount of DTCR and flocculant, temperature and time of reactions on removal efficiency of residual nickel were studied. Results showed that under condition of pH=9, adding 1.0g·L-1 DTCR, and fast mixing 15 min, then adding 6.4mg·L-1 Polyacrylamide, and followed with slow mixied for 5 min, after standing for 10min, the removal efficiency of residual nickel had reached 96.91%, and with residual nickel concentration of 0.95mg·L-1, meeted National Discharge Standard of 1 mg·L-1.Calcium hypochlorite was used to recover phosphorus resource in the waste liquid. The influence of dosing quantity of calcium hypochlorite, pH, temperatrure and reaction time on removal efficiency of phosphorus resource were studied. The Optimum Conditions were pH=8, 60℃, added 3g calcium hypochlorite, continuous stirring for 4h, then the recover rate of phosphorus resource can reach 99.996%, with the residual concentration of 0.93mg·L-1. The sediment can be used as Phosphate Fertilizer.