Research On Advanced Treatment Of Complex Nickel Plating Effluents By Heterogeneous Fenton Based On PMS

Nickel is widely used in the electroplating industry due to its excellent corrosion resistance.However,nickel in plating effluents often forms complex nickel with high chemical stability with complexing agents.Traditional treatment methods have poor treatment effects on complex nickel,so the removal of the complex nickel has always been major difficulty in the field of plating effluents treatment.The most important thing to deal with heavy metal complexes is to break complexes,and Fenton oxidation technology has become one of the most commonly used methods for breaking complexes due to its excellent oxidative degradation ability.However,the traditional Fenton oxidation technology has disadvantages such as narrow operating p H,large mud production,and large consumption of oxidant H₂O₂.For this reason,some scholars have proposed a heterogeneous Fenton system based on PMS.Compared with traditional homogeneous ferrous reagent catalysts,heterogeneous catalysts such as ZVI and Fe₃O₄are less affected by environmental p H and have better catalytic effects.In addition,compared with the liquid H₂O₂oxidant in the traditional Fenton system,solid PMS is chemically more stable,convenient for transportation and storage,and more in line with industrial needs.However,as the country’s requirements for the discharge of plating effluents are further improved,the catalytic activity of the current heterogeneous catalysts cannot effectively remove complex heavy metals in the water,that is,the plating effluents cannot be deeply broken.For this reason,this research selects the heterogeneous Fenton technology based on PMS to improve the electron utilization of heterogeneous catalysts to improve the activation effect of heterogeneous catalysts and provide theoretical support for the deep removal of complexed heavy metals.This topic uses the synthesis of different heterogeneous catalysts to activate PMS to treat complexation plating effluents.Mainly three types of heterogeneous catalysts of zero-valent iron@nitrogen/graphite carbonitride carbon doped carbon（ZVI@C-N/g-C₃N₄）,zero-valent iron@carbon/copper sulfide/copper sulfide（ZVI@C/CuS/Cu₂S）,molybdenum/copper sulfide（MoS₂/CuS）.The performance of the heterogeneous catalyst is evaluated by simulating the heavy metal removal rate of the complexation plating effluents,and its activation mechanism is inferred.The main research contents are as follows:（1）In order to improve the electron utilization of ZVI,the ZVI@C-N/g-C₃N₄composite material with core-shell structure was synthesized by hydrothermal calcination method and used to activate PMS to treat complexation nickel plating effluents.The best treatment conditions are:p H=4.11,PMS=32m M,ZVI@C-N/g-C₃N₄=2.0g/L.Under these conditions,the removal efficiency of ZVI@C-N/g-C₃N₄activated PMS to treat 50 ppm Ni-EDTA and Ni citrate simulated wastewater for 45 minutes reached 95.8%and 100%,respectively.The residual nickel ion concentration can meet China’s emission standards（nickel ion concentration<0.5ppm）.The excellent performance of ZVI@C-N/g-C₃N₄composite material activated PMS processing complex nickel is attributed to its C-N/g-C₃N₄shell layer.The C-N/g-C₃N₄shell of the ZVI@C-N/g-C₃N₄composite material regulates the diffusion rate of H⁺in the shell by capturing,storing and releasing H⁺,providing a suitable microenvironment and regulating the electrons released for the ZVI core.This greatly improves the catalytic activation performance of the ZVI@C-N/g-C₃N₄composite material.（2）In order to further increase the electron transmission rate of the ZVI core in the core-shell structure,the ZVI@C/CuS/Cu₂S composite material was prepared by a combination of hydrothermal method and dipping method,and applied to activate PMS to treat Ni-EDTA simulated plating effluents.The best treatment conditions are:p H=6.30,PMS=48m M,ZVI@C/CuS/Cu₂S=2.0g/L.Under these conditions,ZVI@C/CuS/Cu₂S activated PMS,and the removal efficiency of 50ppm Ni-EDTA simulated wastewater reached 99.53%in 10 min.The residual nickel concentration also meets China’s emission standards（residual nickel ion concentration<0.5 ppm）.Doping CuS/Cu₂S in the carbon layer effectively improves the conductivity of the shell layer and improves the electron transfer efficiency of the ZVI core,which makes the ZVI@C/CuS/Cu₂S composite material have a very high activation rate.And the CuS/Cu₂S in the shell layer also promotes the cycle of Fe³⁺/Fe²⁺,which makes the ZVI@C/CuS/Cu₂S composite material can continuously activate the PMS.In addition,the autocatalysis of CuS/Cu₂S itself further improves the activation rate of PMS and the decomplexation rate of Ni-EDTA.（3）In order to completely avoid the production of iron sludge,synthesis of MoS₂/CuS composite material without iron is used to activate PMS to treat Ni-EDTA electroplating wastewater.The best treatment conditions are:p H=1.95,PMS=48m M,MoS₂/CuS=2.0g/L.Under the best conditions,the removal rate of Ni-EDTA by MoS₂/CuS+PMS process can reach 99.7%within 20 mins.The synergy between MoS₂and CuS greatly improves the catalytic performance of MoS₂/CuS composites.The metal sulfide itself also plays a role in inducing decomplexation.In addition,since the EDTA complexing agent has different complexing strengths to metal elements of different valence states,the metal sulfide itself can also induce decomplexation of Ni-EDTA.（4）Among the three process systems ZVI@C-N/g-C₃N₄+PMS,ZVI@C/CuS/Cu₂S+PMS and MoS₂/CuS+PMS studied in this paper.Among them,the ZVI@C/CuS/Cu₂S+PMS process has the fastest treatment efficiency for complex nickel electroplating wastewater.Thetreatment cost of the MoS₂/CuS+PMS process is the lowest.