Application Of Carbon-coated Foam Iron In Electrochemical Water Treatment

Electrochemical technology can accurately adjust and control the directional movement of electrons,and remove pollutants through oxidation or reduction reactions.With its advantages of flexibility,high energy efficiency and environmental friendliness,it has been widely used in the field of water treatment.The reaction in electrochemical water treatment system mainly occurs on the electrode surface.The preparation of electrode materials and the optimization of corresponding process are the key problems of electrochemical water treatment technology.Carbon based material is stable and has good electrical conductivity,while iron material is relatively active and has excellent reduction performance.The iron/carbon composite is one of the commonly used electrode materials.In this paper,carbon coated iron foam composite electrode material was prepared and applied to micro-electrolysis and electro-Fenton cathode for the removal of organic pollutants in water.The main research contents are as follows:1.Preparation of carbon coated iron foam composite electrode material.Using foamed iron as substrate and glucose as carbon source,carbon was coated on foamed iron by hydrothermal and high temperature carbonization to obtain an integrated block iron/carbon composite--carbon-coated foam iron(CCFI).By scanning electron microscope(SEM),the surface of CCFI is covered by carbon layer,carbon particles are spherical,uniformly coated on the foam iron frame;XRD results show that carbon is graphite phase and iron is zero valence;BET specific surface area of CCFI was 53.2047 m²·g^-1.Linear voltammetric characteristic scan(LSV)showed that it had catalytic activity for oxygen reduction.2.CCFI material was used as micro-electrolysis material in micro-electrolysis water treatment system.Through the redox potential difference generated by the iron-carbon interface in CCFI material,the internal microscopic galvanic cells were formed.At the same time,free radical was generated by oxygen to degrade organic pollutants.Using Dimethyl phthalate(DMP)as the target pollutant,the DMP removal rate of CCFI micro-electrolysis system was 89.25%after 90 min under the initial p H of 3,oxygen aeration rate of 80 m L·L^-1and CCFI dosage of 3 g·L^-1.CCFI was used to degrade DMP in 8 groups of cyclic experiments,and CCFI could still maintain good degradation effect of DMP.Through free radical inhibition experiment and EPR detection analysis,·OH and ¹O₂can be detected in CCFI micro-electrolysis system under initial p H of 3,indicating that CCFI micro-electrolysis system can produce active·OH and¹O₂to remove pollutants.In addition,20 mg·L^-1benzoic acid(BA),sulfamethazine(SMT)and methylene blue(MB)can also be degraded by CCFI micro-electrolysis system under initial p H of 3.3.CCFI material was used as electro-Fenton cathode in electro-Fenton water treatment system.In electro-Fenton system,carbon electrode is often used as cathode to reduce oxygen to produce H₂O₂and then react with iron ion to produce·OH to oxidize organic pollutants efficiently.The aerobic reduction activity of carbon on the surface of CCFI material can reduce oxygen to H₂O₂,and the iron in the material can react directly with H₂O₂to generate·OH to oxidize organic pollutants.The reduction reaction of iron ion can occur at the cathode,which promotes the iron cycle and accelerates the Fenton reaction.The electro-Fenton system was constructed with CCFI as the cathode,platinum sheet as the anode and DMP as the target pollutant.The working conditions of electro-Fenton were optimized by DMP degradation experiment.Under the conditions of current of 25 m A,initial p H of 3,oxygen aeration rate of80 m L·L^-1,CCFI electro-Fenton system had good degradation effect on 5-40 mg·L^-1DMP.CCFI was used to degrade 20 mg·L^-1DMP in 8 groups of cyclic experiments,and DMP could be completely degraded by CCFI electro-Fenton system within 30 minutes,indicating that CCFI had stable reaction performance and could be used continuously for a long time.The free radical analysis of reaction products and reaction process showed that both·OH and singlet oxygen ¹O₂produced in the reaction process of electro-Fenton system contributed to the degradation of DMP,and·OH degradation was dominant under the condition of electricity.In addition,CCFI electro-Fenton system was used to degrade MB,BA and SMT.The results showed that CCFI electro-Fenton system had good degradation effect on different organic pollutants.4.Corrosion protection of iron/carbon materials.The material loss and inactivation caused by corrosion of iron/carbon materials in practical application cannot be ignored.Sodium silicate was introduced into the electro-Fenton system.Adding 0.1wt%sodium silicate to CCFI electro-Fenton system,the solution was still clear and colorless at p H 5,7 and9,and the surface of CCFI material had no obvious rust stain,which improved the performance of CCFI under neutral aerobic condition.Under neutral condition,0.1 wt%sodium silicate can achieve good corrosion inhibition effect.Under the condition of containing 0.1wt%sodium silicate,CCFI electro-Fenton system degraded DMP in 4consecutive cycles at the initial p H of 7.CCFI could keep the surface rust free.Compared with the electro-Fenton system without sodium silicate,CCFI can be used for several times,which improves the utilization rate and performance of the material.