Preparation Of Co-based Particle Electrodes And The Performance And Mechanism For Catalytic Degradation Of Humic Acid

Humic acid（HA）is an important component of landfill leachate,coking wastewater,and sewage sludge wastewater.It is difficult to be removed by biodegradation because of its complex structure,which seriously affects the treatment of wastewater.Three-dimensional（3D）electrode has been considered as a promising method for the removal of refractory organic pollutants due to its simple operation,mild reaction conditions and high efficiency.Three-dimensional electrode system is usually composed of cathode plate,anode plate and filled particle electrodes.Particle electrode is the core factor in 3D system.In this paper,activated carbon powder（PAC）was used as the carrier and cobalt（Co）was used as the catalyst to prepare the cobalt-based particle electrode and use to degrade HA.The degradation performance and mechanism of HA by cobalt-based particle electrode,cobalt-based particle electrode and persulfate system were studied.Besides,the carbon point（CDs）was introduced to Co-based particle electrode to study the degradation performance and mechanism of HA.The main results are as follows:Columnar activated carbon（Co⁰/AC）catalytic particle electrode loaded with zero-valent Co was successfully prepared by using PAC as carrier and N₂ completely replacing H₂,which can realize efficient degradation of HA.When the initial COD of HA was 200 mg/L,at 3.34 m A/cm²,p H 7.0,Na₂SO₄ 0.01mol/L and hydraulic retention time（HRT）20 min,the COD removal efficiency was 88.1%-93.6%.An increase in current or HRT had a positive effect on HA degradation.HA could be degraded efficiently under acidic and neutral conditions.The presence of Na₂SO₄ was beneficial to HA degradation,while the addition of Na NO₃ reduces the degradation efficiency of HA.The·OH and H*radicals were mainly produced in the Co⁰/AC system.The co-participation of advanced electrooxidation and advanced electroreduction greatly improved the degradation and removal of HA.The water treatment technology of Co⁰/AC particle electrode combined with PS（Co⁰/AC+PS）was constructed.The Co⁰/AC+PS system enhanced HA degradation,and the degradation efficiency increased from 37.7%to 90.3%.The molar ratio of[PS]/[HA]was only 6.8,reducing the dosage of PS.The addition of PS made the effluent neutral and overcome the problem of alkaline effluent.The addition of PS eliminated the negative effect of NO₃^-on HA degradation.The addition of PS increased the oxygen evolution potential of Co⁰/AC in acidic and neutral media,and decreased the hydrogen evolution potential.In the Co⁰/AC+PS system,SO₄^-·,·OH and H*radicals were mainly produced.Co⁰/AC particle electrode accelerated the activation of PS to produce SO₄^-·and·OH,and promoted the generation of H*radical.CDs-doped Co⁰/AC（Co-CDs/AC）catalytic particle electrode was prepared by modifying Co⁰/AC with CDs.The doping of CDs weakened the agglomeration of catalyst,made the catalyst more dispersed and increased the catalytic active site.Compared with Co⁰/AC+PS system,Co-CDs/AC achieved high efficiency degradation of HA without adding PS,reaching 87.4%-99.1%.The addition of CDs eliminated the inhibition of NO₃^-,improved the mass transfer coefficient and extended the p H range of the process application.The·OH and H*radicals were mainly produced in the Co-CDs/AC system.The introduction of CDs promoted the generation of H*free radicals.Compared with Co⁰/AC system,the contribution rates of direct oxidation and·OH radical oxidation were consistent in Co-CDs/AC system,but the production amount and second-order rate constant of·OH were decreased.Different from most reports,the degradation and removal of HA were realized by oxidation,and the reduction of H*free radicals played an important role in the cobalt-based particle electrode system,and HA macromolecules were gradually decomposed into saturated alkane and other small molecular organics.