Experimental Study On The Treatment Of Heavy Metal Nickel In Electroless Nickel Plating Wastewater

The electroless plating industry has helped the growth of economy enormously but alsobrought serious environmental pollution problems.Due to illegally emission wastewater which contain kinds of heavy meatal,such as Nickel,it can accumulate in the soil,then enter the food chain,and eventually end up accumulate in animals.It has long-term damage to the animal's metabolic activity.The concentration of heavy metals in electroless nickel-plating wastewater is high and most of them are in complex state.Facing of increasingly stringent emission standards,traditional methods such as chemical precipitation,electrolysis,and biological methods have been difficult to meet the needs of enterprises.In the current situation,the electroless nickel plating wastewater from a certain electroplating company?with a nickel concentration of40.5-50.1mg/L?has found a green,efficient,and economical“electrochemical+tubular microfiltration membrane”combination process.The concentration of heavy metal nickel in the electroless nickel plating wastewater was reduced to 0.1 mg/L or less.In the course of the study,the influencing factors of each process were examined,and the optimum process parameters of the combined process were determined through experiments.The removal of nickel in electroless nickel plating wastewater by traditional Fenton method found that when the reaction time=40min,pH=3,H₂O₂ dosage=8mmol/L,and C?H₂O₂?/C?FeSO₄?=10,nickel The removal rate can reach 95.1%,but the reaction time is longer,and a large amount of flocculant needs to be added,and the amount of sludge is also large.Electrochemical method to remove nickel in electroless nickel plating wastewater shows that the factors affecting the nickel removal rate by electrochemistry method are influent pH>current density>H₂O₂ dosage>reaction time,electrochemical optimal process parameters.For inlet water pH=3,current density=170 A/m2,H₂O₂dosage=0.8mmol/L,reaction time=8 min,the treatment effect can reach 98.5%.Compared with Fenton's method,the electrochemical reaction time is shorter,H₂O₂ is more efficient and produces less sludge.Finally,two factors influencing the treatment effect of the tubular microfiltration membrane equipment were discussed:the pH of the influent water and the ratio of concentrated water to the produced water,and the optimal process parameters for removing the nickel from the tubular microfiltration membrane equipment were determined:pH=10 for incoming water,water production Concentrated water ratio=1/1;factors affecting the life cycle of the tubular membrane,operating pressure and backwashing time were analyzed and the best parameters were obtained:operating pressure=0.3MPa,backwashing time=20s.The experiment of"continuous integration of electrochemical+tubular microfiltration membrane"has been carried out.The experiment shows that the"electrochemical+tubular microfiltration membrane"combination process can basically reduce the heavy metal nickel in the electroless nickel plating wastewater to below 0.1 mg/L,the expected target of this experimental study was achieved.