Study On Treatment Of Coking Tailwater By Fe-La Modified Biochar Particle Electrodes Electro-activated Persulfate

Coking wastewater is a mixture of liquids produced during the production of coke,coal washing,coke quenching,collection of coking products and separation and refinement of by-products.Its pollutant composition is complex,biotoxic and hard to degrade.Biologically treated coking wastewater still contains many hard-to-degrade organic substances,and direct discharge will harm human health as well as fisheries and agriculture.Advanced oxidation technology is based on the non-selective reaction of highly reactive radicals with most organic substances and is widely used for the removal of refractory pollutants from wastewater.In this paper,based on the preparation of Fe-La/biochar（BC）particle electrodes,the coking tailwater was treated with synergistic electrochemical activated persulfate,combining two advanced oxidation processes,which enhanced the current efficiency of the reaction system and reduced the energy consumption,providing a new idea for the deep treatment of coking wastewater.The prepared Fe-La particle electrodes were analyzed by SEM,XRD,FTIR and BET characterization;the effects of different factors on COD,TOC and UV₂₅₄of treated coking tailwater were also investigated.Combined with gas chromatography-mass spectrometry（GC-MS）and three-dimensional fluorescence spectroscopy（3D-EEM）,the types of organic matter in the coking tailwater before and after treatment were judged and analyzed.Fe-La/biochar（BC）particle electrodes were prepared by co-precipitation method and hydrothermal method,respectively.Analytical characterization（SEM,XRD,FTIR and BET）showed that the crystallinity of Fe-La/BC particle electrode prepared by hydrothermal method was better than that of co-precipitation method,and the metal oxides were uniformly distributed on the particle electrode surface,and the specific surface area was reduced due to the loading of metal oxides.The above results indicate that the metal oxides were successfully loaded onto the surface of biochar（BC）.In the Fe-La/biochar（BC）particle electrodes activated persulfate（KPS）treatment system for coking tailwater.When Fe-La/biochar（BC）particle electrode was dosed at 20g/L,peroxynitrite（KPS）concentration was 2 mmol/L,current density was 30 m A/cm²,and electrolysis time was 90 min,COD and TOC decreased from 486.07 mg/L and 340.00mg/L to 67.33 mg/L and 141.65 mg/L,respectively,and UV₂₅₄decreased from 4.54 to 1.56.The GC-MS and 3D-EEM techniques showed that the untreated coking tailwater was mainly composed of long-chain alkanes,esters,benzenes and high molecular organic compounds such as alcohols,while the coking tailwater treated with Fe-La/BC/KPS system was mainly composed of small molecules of halogenated hydrocarbons and benzenes.The Fe-La/BC particle electrodes had a higher oxygen precipitation potential and higher catalytic activity than the biochar（BC）particle electrode alone,and the addition of peroxynitrite（KPS）will increased the oxygen precipitation potential of the system and suppressed the oxygen precipitation side reactions in the process.The hydroxyl radicals（·OH）and sulfate radicals(SO₄^·-)were generated in the system and participated in the oxidation of organic pollutants in the system.Moreover,the stability of Fe-La/biological carbon（BC）particle electrodes were better,and their current efficiency during the reaction were improved and energy consumption were duced.