As the nickel plating of nickel sulfate concentration of nickel plating solution is usually only one-tenth, if the recycling of rinsing water re-use, virtually no impact on the environment. However, the chemical nickel plating bath is always important to the aging problem is, when the repetitive use of more than 5 cycles, due to the bath of phosphate and sulfate Central Asia, the accumulation will be significant impact on the quality of coating. Then the general aging of the bath containing 3-5g/ l of nickel, if directly mixed with rinse water, will undoubtedly impact on the environment; increase the rinse water treatment difficult.
A result showed that the purpose of electrolysis should be the recovery of nickel considering the whole treating process of electroless nickel plating wastewater. And the optimal parameters were pH of 9, current density of 8.0 mA·cm-2, temperature of80℃, circulation, electrolysis time of 2h while the recovery efficiency of nickel was 98.7% and the removal efficiency of COD was 61.91%. The H2PO2- in the wastewater was completely oxidized. Then precipitation was applied for the purpose of the removal of phosphorus. CaO and Fe2(SO4)3 were chosen as the precipitant. Each effect of precipitant’s parameters on the removal efficiency of HPO32-, PO43- and total phosphorus were studied. The result of Fe2(SO4)3 was better than CaO, the optimal parameters were pH of 5, Fe/P molar ratio of 1, aging temperature of20℃, aging time of 6.5h. The removal efficiency of HPO32-, PO43- and total phosphorus were 98.6%, 99.99% and 99.48% with a certain degradation of COD. EF was applied to degrade the COD of wastewater. It showed that EF could remove the COD of wastewater effectively. The optimal parameters were continuous dosing, pH of 3, current density of 13.16 mA·cm-2, H2O2 dosage of the oretical value, Fe2+/H2O2 molar ratio of 1/10. The removal efficiency of COD is 97.89%. HPO32- was oxidized to PO43-,then PO43- precipitated with Fe3+.After the whole treating process, total nickel and total phosphorus of electroless nickel plating wastewater achieved the national discharge standard. The residual COD was 305.52mg·L-1 and pH was 3. The quality of the wastewater was greatly improved.
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