Treatment Of Electroless Copper And Nickel Wastewater By Microwave Advanced Oxidation Process

The copper/nickel electroless plating effluents from chemical plating industrial parks often contain large amounts of complexed metal with different concentrations.Traditional Fenton process for their treatment still exist some defects such as low oxidation efficiency and high sludge yield.Recently,Microwave advanced oxidation processes?MAOPs?have been proved to be effective in the treatment of some refractorty effluents including coal effluents and pharmaceutical effluents,and are characterized as high treatment efficiency and low sludge yield.Theoretically,it is also applicable to the abatement of chemical plating effluents,and may overcome the drawbacks mentioned in the traditional Fenton process.Up to data,only few research focus on the Cu/Ni-EDTA removal by MAOPs.In present study,batch experiments were carried out to study its feasiblity,and a comprehensive treatment approach was finally proposed so as to reduce the pollutant from electroless plating effluents.For the sole Ni-EDTA effluent with the concentration of 100 mg/L,the most effective treatment method was Microwave-Fenton process.Under the optimal conditions(initial p H of 3,Fe²⁺dosage of 1 mmol/L,H₂O₂ dosage of 41 mmol/L,microwave power of 210 W,reaction time of 10 min),the removal efficiencies of Ni and TOC could reach 94.0%and 40.1%respectively,and the sludge yield was only0.28 g/L.While for the Ni-EDTA effluent with the concentration of 1000 mg/L,the same microwave power lower,lower initial p H,higher amount of H₂O₂ and Fe²⁺dosing,and less reaction time has positive effect on the Ni and TOC removal,each with the efficiency of 96.2%and 53.4%,respectively.For the sole Cu-EDTA effluent with the concentration of 100 mg/L,Microwave-Hydrogen peroxide process was found to be the best process.Highest removal efficiencies of Cu?97.1%?and TOC?60.7%?and minimum sludge yield?2.9 g/L?could be achieved in the conditions as follows:initial p H of 3,H₂O₂ dosage of 41mmol/L,microwave power of 210 W,and the reaction time of 10 min.And highest removal efficiencies of Cu?92.9%?and TOC?66.3%?could be obtained for the Cu-EDTA effluent with the concentration of 1000 mg/L under the optimal conditions.The mixed effluents of Ni-EDTA and Cu-EDTA with concentration of 500 mg/L was treated by MW-H₂O₂ process.Under the optimal conditions,the removal rate of Cu,Ni and TOC could reach 95.0%,90.7%and 44.4%.The comparison of the treatment efficiencies for the mixed or separated effluents indicicated that mixing the different effluents together facilitated the decrease of sludge production,even though higher energy might be required.Therefore,it was recommended to mix the effluents containg the Ni-EDTA and Cu-EDTA together before treated by MW-H₂O₂ process.