| Electrochemical oxidation technology has been widespread concern in refractoryorganic wastewater treatment, because of its no secondary pollution andenvironment-friendly superiority. Electrode materials are the core of electrochemicaloxidation process and the degradation efficiency is the key factor to constraint industrialapplications of electrochemical oxidation technology in wastewater treatment. In orderto improve the efficiency, the impact law and mechanism of electrode materials,preparation and modification on electrode performance were investigated. Thedegradation mechanisms of different electrochemical processes for organic matter wereanalyzed by the degradation process of phenols. The results provide a reliabletheoretical basis for the preparation and application of high performance electrodes.Tin titanium base electrode (Ti/Sb-SnO2) was modified by rare earth elementcerium group, and the electrolysis effects of analog nitrophenol (p-NP) wastewater withdoped and undoped electrode were compared. Experimental results showed that the bestLa doped tin titanium-based electrode performance was the best. The results showedthat92.8%p-NP was removed when using Ti/Sb-SnO2-La as electrode, which wasmuch higher than that when using Ti/Sb-SnO2as electrode.The micrograph and the structure of the electrode were characterized by SEM andXRD. The element composition of electrode coating were determined by EDS．Thebinding energy of the elements in electrode coating were analyzed by XPS. Andelectrochemical properties of the electrodes were determined by linear sweepvoltammetry (LSV). Various test results showed that electrode coating becoming moredense, grain refining and enrichment of doping elements on the electrode surface electrodes which caused by rare earth doping was the main reason for electrodeperformance improvement. Besides, the increase of oxygen vacancy and adsorbedoxygen within the coating caused by rare earth doping was also the key actor.The study of electrode life extending was carried out by adding Mn, Ni, Co, Cr, ina tin titanium base electrode coating as the intermediate layer. Quick electrode life testshowed that: the life of electrode which added MnO2as intermediate layer is4times ofthe electrode which not added the intermediate layer. According to SEM analysis, theelectrode coating cracks were reduced and surface protrusions were increased whichadded MnO2as intermediate layer. This illustrated that intermediate layer which addedin the electrode coating can prevent the corrosion and oxidation on titanium substratewith electrolyte and oxygen.High performance gas diffusion cathode was prepared with graphite andpolytetrafluoroethylene (PTFE). Moreover, the influence of the material ratio and thepreparation conditions on the electrode performance was discussed. Experimentalresults showed that Under the optimum conditions which graphite and PTFE in a massratio is2︰1, rolling pressure is10MPa, and calcination temperature is330℃,Pore-forming agent is the major factor which affect the performance of the gas diffusionelectrode. The performance of electrode with3as pore-forming agent is the best, in thiselectrolysis system production of hydrogen peroxide improved by232%than theelectrode that is not added pore-forming agent. SEM and porosity test explained thatpore-forming agent increasesed the vapor and liquid channels of electrodes thatimproved their electrocatalytic properties. In addition, Tm and Ce doping in cathode canalso promote the generation of hydrogen peroxide.Chitosan-based organic polymer particle electrode was prepared by usingcrosslinked chitosan and its graft product with four amino cobalt phthalocyanine. Theparticle electrode was constituted dimensional electrode system with titanium-based tinelectrodes to degrade phenol wastewater. Three-dimensional electrode increased theratio of electrode surface to electrolyzer volume, and the electrolysis efficiency wasbetter than the plate (two-dimensional) electrode. When achieved the same degradationefficiency, the electrolytic time which used in Three-dimensional electrode is only halfof the plate electrode. The electrolysis efficiency which four amino cobalt phthalocyanine crosslinked chitosan worked as particle electrode is best, phenolics finaldegradation rate was about7%higher than that of activated carbon particle electrode.The degradation course of phenolic compounds was concluded by their ultravioletspectrometry detecting with anodic oxidation and electro-Fenton oxidation process. Theoxidation mechanism of different electrochemical oxidation process degrading phenoliccompounds was discussed. The experiment results show that: there was phenolicintermediate accumulation in the p-NP wastewater which degraded in the anodicoxidation process. This illustrated that in anodic oxidation process, in addition to theindirect oxidation of hydroxyl radicals, the direct oxidation which gradually oxidateorganic pollutants played an important proportion in oxidation effect. However, therewas no phenolic intermediate accumulation in the phenol wastewater which degraded inthe electro-Fenton oxidation process. The results show clearly that the oxidationfunction was completely performed by hydroxyl radicals produced in electro-Fentonsystem, and oxidation reaction process was quickly and thoroughly.The electro-Fenton technology with stainless steel anode and cathode ofgraphite-based gas diffusion electrode was constituted to treat semi-coke wastewater.The effect of electro-Fenton technology treating real production wastewater wasinspected, and the electrolytic process conditions were optimized. By several exhaustiveexperiments, the optimum removal rate of COD is up to78.62%at the optimizedconditions in the laboratory of the oxygen sparging rates at2.5L/min, the optimalelectrode plates distance at2cm, current density at5.2mA/cm2, solution pH at3, whichis proved an high efficiency pretreatment for semi-coke wastewater, and an promisingnew method for the treatment of non-biodegradable high concetration wastewater in thefuture. |
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