Biochar Particle Electrodes Facilitated Three-dimensional Electro-fenton Degradation Of Electronic Industry Wastewater

Currently,rapid development of electronic industry produced a large number of correlated wastewater.The composition of this kind of wastewater was complex,containing a large number of organic pollutants which were refractory to be degraded,if not effectively treated,it will pose a threat to the ecological environment and human health.Compared with other methods,electrochemical method is a method with good treatment effect and high efficiency.As an electrochemical method developed on the basis of traditional electro-Fenton（EF）,three-dimensional electro-Fenton（3D/EF）overcame the low current efficiency of traditional electro-Fenton with the adding of particle electrodes between anode and cathode.In this study,biochar prepared from Taihu blue algae was adopted as the particle electrodes while stainless steel was employed as the anode and cathode to construct a 3D/EF system for the treatment of electronic industry wastewater.Meanwhile,the simulated wastewater containing Mono-2-ethylhexyl Phthalate（MEHP）was selected,and degradation mechanism of the simulated wastewater treatment via 3D/EF system was studied.The main conclusions of this study are as follows:（1）Containing a large number of organic pollutants with high aromatics and high molecular weight,the panel wastewater was selected as a typical electronic industry wastewater for further investigation.The optimal reaction parameters of Fenton process for the treatment of electronic industry wastewater are as follows:the concentration of ferrous sulfate heptahydrate（Fe SO₄·7H₂O）of hydrogen peroxide（H₂O₂）reached 0.53 and 12.3 mmol/L,respectively.Accordingly,removal rate of chemical oxygen demand（COD）in wastewater achieved 81.6%after 60 min.（2）Using Taihu blue algae as raw material,the algal biochar particle electrode was prepared by activation of potassium hydroxide（KOH）activation and nickel chloride（Ni Cl₂·6H₂O）loading.The successful loading of nickel element was demonstrated by scanning electron microscopy（SEM-EDS）,specific surface area（BET）and X-ray photoelectron spectroscopy（XPS）characterization.The specific surface area of biochar ranged from 1317.9m²/g to 1568.0 m²/g after loading,which could improve the electrocatalytic activity of material.In addition,iron elements appeared on the surface of biochar after the reaction,which proved that iron ions deposited on the biochar materials during the reaction process of 3D/EF system,forming bimetallic catalytic oxidation effect.（3）The optimal reaction conditions of 3D/EF system for the treatment of electronic industrial wastewater are as follows:initial p H at 3,current density at 20 m A/cm²,aeration rate at 100 m L/min and particle electrode dosage at 2.0 g/L.Afterwards,COD removal reached more than 80%after 60 min reaction,and the energy consumption was 14.24 k W·h/m³,which was much higher than the effect of the wastewater treatment via EF system.The repeatability experiment of biochar particle electrode showed that the total organic carbon（TOC）removal rate decreased from 68.0%to 60.5%after repeated 5 batches,indicating that this material has good reusability.（4）MEHP removal via 3D/EF system was significantly reduced after the addition of free radical quenchers p-benzoquinone（BQ）and tert-butanol（TBA）,indicating that free radicals played an important role in the degradation of MEHP.Then,the molecular structure of MEHP was optimized by quantum chemistry calculation,and the radical attack sites of MEHP were analyzed based on density functional theory（DFT）.Combined with the intermediate products produced by MEHP in the 3D/EF system during the process of gas chromatography-mass spectrometry（GC-MS）analysis,degradative pathway of MEHP into CO₂ and H₂O in the 3D/EF system was proposed.In conclusion,employing algal biochar as particle electrode to construct 3D/EF system to treat electronic industrial wastewater could achieve more than 80%of COD removal and realize the resource utilization of blue algae.Besides,through the characterization of the biochar particle electrodes before and after the reaction,it was found that the anode continuously released iron ions during the reaction process,to form bimetallic catalytic oxidation effect in the 3D/EF system together with nickel elements.This study provides a new direction for the treatment of electronic industry wastewater and the utilization of blue algae.