| The electroless plating process is a new type of metal surface treatment technology,which is uniform in coating,simple,energy-saving,environmentally friendly,and has a wide range of uses.At the same time,various novel complexing agents,brighteners and buffer solutions are added in the electroless plating process to form an intractable complex metal（especially a nickel complex）,which makes the wastewater treatment difficult to be greatly increased.In recent years,national and local environmental protection departments have imposed stricter requirements on the discharge of electroplating wastewater pollutants.The total Ni emission limit is 0.1mg·L-1.in the wastewater discharge standard stipulates of Table 3.Therefore,this paper mainly takes the chemical nickel plating wastewater after conventional physicochemical treatment as the research object,and conducts in-depth research on its low concentration and high steady state complex Ni pollutants,and finds a new stable and efficient advanced treatment method.In this paper,the actual electroless nickel plating wastewater from the wastewater treatment plant of an electroplating industrial park in Dongguan was selected as the research object,and the water pollution index and pollution characteristics were analyzed.The pre-oxidation and decomposing combined with heavy metal precipitant was used to remove the total Ni in the wastewater.A new and efficient ozone pre-oxidation decomposing-heavy metal capture chelation depth treatment technology system was selected through experiments,which is called O3-SN9 coupling system.Through single-factor static experiments,the effects of different treatment conditions on the total nickel（Ni）removal rate of effluent were investigated.The results show that the optimal conditions are 7.011.0 of pH,40 min of reaction time,3 L·min-11 of ozone carrier gas flow rate,40 mg·L-1 of SN9 dosage.After the treatment,the total Ni concentration of the wastewater is less than 0.1 mg·L-1,which can meet the emission concentration requirement of total Ni in the special discharge limit of water pollutants（Table 3）.The results of LC-MS and TBA capture·OH tests show that ozone oxidation is dominated by indirect oxidation and direct oxidation is supplemented.In order to improve the gas-liquid mass transfer efficiency and effective utilization rate of O3,a solid catalyst is added in the process of ozone pre-oxidation to form a catalytic system of ozone catalytic oxidation-heavy metal chelation（SAO3-II/O3-SN9）.The results showed that the optimal reaction conditions for the SAO3-II/O3-SN9 system were the initial pH range of 7.010.0,30 min the reaction time of,1:1.5 of the solid-liquid ratio and 3 L·min-11 of the O3 carrier gas flow rate.The SAO3-II catalyst layer is placed close to the aeration head.After treatment with SAO3-II/O3-SN9 system,the total Ni concentration of the effluent was 0.09 mg·L-1,and the reaction time was reduced by 25%compared with the O3-SN9 system.Characterization of SAO3-II shows that SAO3-II can catalyze the conversion of ozone into a strong oxidizing·OH,increasing the indirect oxidation capacity of ozone.According to the best test results,a set of extended test equipment for continuous operation is designed and pilot research is carried out in the electroplating treatment plant.The results show that under the condition of maximum treatment flow rate of60 L·h-1,the total Ni concentration of effluent which below 0.1 mg·L-1.Through statistical pilot test data,the processing cost is calculated,which provides data support and theoretical basis for the next stage of research. |
