Electrochemical Treatment Of Sulfadiazine And Copper Ions In Livestock Wastewater By Boron-doped Diamond Electrode

In recent years,antibiotics have been widely used in the livestock and poultry farming industry due to their special effectiveness in the prevention and treatment of livestock and poultry animal related diseases.In addition,metal ions such as copper and zinc are also added into livestock and poultry feeds in large quantities due to their functions in promoting cell metabolism and growth.Antibiotics and heavy metals are frequently detected in livestock excreta due to their excessive use and low absorption in animals.Antibiotics and heavy metals in livestock and poultry excreta will not only pollute the environment and destroy the ecological balance,but also may cause harm to humans through the food chain,posing a high risk to the ecological environment and human health.As a kind of advanced oxidation treatment process,electrochemical treatment can completely remove antibiotics and heavy metal pollutants without secondary pollution,so it has received wide attention in recent years and has been tried to be applied in the treatment of livestock and poultry breeding wastewater.In this paper,an electrochemical process with Boron-doped diamond（BDD）electrode as the anode and stainless steel electrode as the cathode was proposed to degrade sulfadiazine（SDZ）,a commonly detected antibiotic in livestock farming wastewater,and copper ions(Cu²⁺),a commonly detected heavy metal.On the basis of the physical and electrochemical properties of the BDD electrode,the effect of each key factor on the degradation efficiency of the target pollutant was investigated to reveal the degradation mechanism of SDZ and Cu²⁺in the electrochemical system.Finally,the efficacy of BDD electrochemical technology on livestock farming wastewater under three different water quality conditions was comprehensively investigated,with a view to providing technical references for further practical application of the treatment process.The physical properties of the BDD electrode were characterised by SEM,EDS and Raman spectroscopy,showing that:the BDD electrode has good surface morphology,high mechanical strength and superior metal-like properties;the cyclic voltammetric curve and linear scan curve analysis of the BDD electrode proved that:the electrode has high oxygen precipitation potential,less oxygen precipitation side reactions,which is conducive to the generation of active species and the improvement of electrocatalytic efficiency.Typical antibiotics（SDZ,C₀=10 mg/L）and heavy metals(Cu²⁺,C₀=5 mg/L)were selected as target pollutants to configure a simulated livestock farming wastewater,and the effects of different electrolysis parameters,common background ions in the water column,simultaneous electrochemical treatment and separate electrochemical treatment on the degradation efficacy of the reaction system were investigated.The results showed that the optimal working conditions for the simultaneous electrochemical treatment were:current density of 40 m A/cm²,pole plate spacing of 20 mm,rotational speed of 400 r/min,electrolyte Na₂SO₄concentration of 50 mmol/L,initial p H=8.0 of the reaction system,the degradation efficiency of SDZ after 90 min of electrochemical treatment was 93.3%,and the degradation efficiency of Cu²⁺was 84.3%,after treatment,the concentration of Cu²⁺was only 0.32 mg/L;among the common background ions,Cl^-played a certain degree of promotion,HCO₃^-played an inhibitory role on the degradation efficiency of the reaction system,PO₄^3-also played a certain degree of inhibition on the degradation of pollutants in the reaction system,but the inhibition effect was less than that of HCO₃^-;the simultaneous electrochemical treatment played a positive role on the removal of SDZ because the addition of copper.This is because the addition of Cu ions resulted in a faster electron transfer rate,a stronger current response and an increase in the amount of active species in the reaction system.The simultaneous electrochemical treatment inhibited the removal of Cu²⁺to a certain extent,but the inhibitory effect was small,and the efficacy of the simultaneous electrochemical treatment was better than that of the separate electrochemical treatment.The reaction system contributes to the degradation of SDZ by the DET reaction and the advanced oxidation of·OH through free radical inhibitor and chemical probe tests;the analysis of the degradation products of SDZ in the electrochemical system showed that the degradation of SDZ was mainly caused by a series of oxidation,bond breaking and ring opening through the action of electrode electron transfer and reactive species;XPS analysis shows that the degradation of Cu²⁺in the system is in accordance with the degradation law under alkaline conditions,i.e.at the beginning of the reaction,Cu²⁺reacts rapidly to form Cu（OH）₂precipitate,and as the reaction proceeds,the p H of the solution gradually decreases and the Cu（OH）₂precipitate gradually dissolves,and after the Cu²⁺is analyzed,it is gradually adsorbed at the cathode by reduction and deposited and finally removed.The efficacy of the electrochemical process was investigated with three different water qualities,including raw water,anaerobic digestate effluent and aerobic effluent of livestock farming wastewater,the results show that this process system has the best degradation efficiency when applied to the deep treatment of aerobic effluent.Therefore,the boron-doped diamond anode electrochemical treatment process can be considered for the deep treatment of livestock and poultry farming wastewater,with a view to providing reference for the exploration of new advanced oxidation treatment processes and the promotion of engineering applications.