Technology For Breaking Strong Complex Containing Copper And Nickel In Electroless Planting

Electroless plating is a technology that do not need impressed current but can form a coating process,thus,large amount of additives such as complexing agent in the plating solution were needed.Stable complex compounds were formed between complexing agent and heavy metal ions,which guarantee the quality of the plating and the lifetime of the plating solution.Therefore,more complexing agents were produced during the process of chemical plating when compared with electroplating wastewater process.There were some limitations when using the conventional processing methods to treat the chelating heavy metal,moreover,it was hard to meet the discharged standards of heavy metal ions,especially after the discharge standards become stricter.To ensure the normal operation of enterprises,it is urgent and practicable to do some research.This study investigated the treatment of high concentration of wastewater containing heavy metal ions,which based on the treatment technology of electroplating wastewater in an electronics factory in Guangzhou Science City.Baed on Fenton process and chlorine oxygen treatment technique on the factory,DDTC complexation precipitation method,Fenton-chlorine oxide method,and coagulation-oxidation method were further used to treat the complexing copper-nickel wastewater.Operating parameters were optimized in experiments,and the mechanism of copper-nickel removal from wastewater by coagulation-oxidation method was further explored via experiment results.The main conclusions are as follows:The optimum operating parameters on treatment of electroless planting wastewater by DDTC complexation precipitation method are 30.0 g/L of DDTC and the reaction time of 2 min at p H 8.0.In this optimum reaction condition,the residual concentrations of Cu²⁺ and Ni²⁺ are 0.21 mg/L and 0.13 mg/L,respectively.The treated wastewater failed to meet the discharge standard because the residual concentrations of Ni²⁺ is higher than 0.1 mg/L.DDTC showed higher selectivity for Cu²⁺ compared with Ni²⁺.This method failed to remove COD and total nitrogen from wastewater,so it can be used aspretreatment and depth processing technology.The optimum operating parameters on treatment of electroless planting wastewater by Fenton chlorine-oxide process are 33.33g/L H₂O₂?30%?,n?Fe SO₄?/n?H₂O₂?=3:1with the reaction time of 1h at p H 3.0.In the later stage of experiment,the pH was adjust to8.0,and 44.0g/L Na Cl O?10%?was added.Then the reaction time continued for 45 min.The residual concentrations of Cu²⁺ and Ni²⁺ are 0.27mg/L and 0.08 mg/L,respectively.The treated wastewater meet the discharge standard of table 3 in?The Discharge Standard Of Electroplating Pollutants??GB21900-2008?.The optimum operating parameters on treatment of electroless planting wastewater by coagulation-oxidation process are as follows:?i?add 0.25 L FeSO₄?25%?and stir for10 min at pH 8.0;?ii?0.6L Na Cl O?10%?was added and reaction for 45 min at pH 8.0.After that,the residual concentrations of Cu²⁺and Ni²⁺are 0.25 mg/L and 0.09 mg/L,respectively.The treated wastewater meet the discharge standard.This study combined DDTC complexation precipitation and coagulation-oxidation method to treat electroless planting wastewater.First,0.25 L FeSO₄?25%?and 0.15 L Na Cl O?10%?were added,reaction for 45 min at p H 8.0.Then 1.0g DDTC was added to the solution.After that,the residual concentrations of Cu²⁺ and Ni²⁺ are 0.16 mg/L and0.09 mg/L,respectively.The treated wastewater meet the discharge standard of table 3 in?The Discharge Standard Of Electroplating Pollutants??GB21900-2008?.The chemical agent cost for treatment of 1 t of electroless planting wastewater is 212.5 yuan,and the mechanism of coagulation and oxidation was further explored.In conclusion,complexation precipitation had obvious effect on heavy metals when compared with other methods but it could not be used alone;Fenton-chlorine oxygen method did not cause secondary pollution and had perfect removal efficiencies,but required high cost;Coagulation-oxidation was cheaper and had good removal efficiencies,but high levels of free chlorine could cause secondary pollution.Therefore,it is necessary to combine the technology and explore new methods.In this research,our results indicated that the combined method of complexation and oxidation method showed good treatment efficiencies,moreover,it did not cause secondary pollution andcheaper.