Synergistic Removal Of Organic Sulfur From Petcoke By Microorganisms And Fe-TiO₂ Photocatalysis

With the deepening of supply-side structural reform,China’s electrolytic aluminum industry is embarking on the road of healthy development,and the demand for petcoke has also maintained a steady rise.At present,the market of high-quality low-sulfur petroleum coke is in short supply,and many enterprises have to turn their attention to high-sulfur petcoke.Therefore,it is of great significance to find an efficient and economic desulfurization method of high-sulfur petcoke to improve its utilization.In this study,the synergistic desulfurization of microorganisms and photocatalysts was carried out for the purpose of removing organic sulfur from petcoke.Firstly,Rhodococcus sp.DQ-07,which was screened and isolated from long-term oil-contaminated soil,is a dibenzothiophene-tolerant degradation strain that can specifically break C-S bonds without damaging the calorific value.Secondly,nano-TiO₂thin films were prepared by sol-gel method and doped with transition metal iron to improve its photocatalytic properties.Finally,the petcoke was pretreated by photocatalytic oxidation through Fe-doped TiO₂film,and then biodesulfurization was carried out to realize the deep desulfurization of high sulfur petcoke.The main research contents of this study are as follows:（1）Nine strains of bacteria resistant to dibenzothiophene were screened and isolated from oil-contaminated soil in Daqing.Through the identification of the fermentation broth,a strain of bacteria that can specifically oxidize dibenzothiophene to o-phenylphenol and sulfate ions was finally screened.After 4 days of fermentation,the degradation rate of Dibenzothiophene was 85.5%.The strain is preliminarily predicated belong to Rhodococcus by the cell morphology and 16S rRNA sequence analysis and named as Rhodococcus sp.DQ-07.（2）Fe-doped TiO₂photocatalyst was prepared by the sol-gel method,and then the sol was made into a thin film by impregnation and pulling.In the experiment of photodegradation of dibenzothiophene,the preparation process of Fe-doped TiO₂film was optimized.When the amount of Fe doping was 4 wt%,the heat treatment temperature was 450℃,and the number of coating layers was four,the TiO₂photocatalyst film shows the best photocatalytic activity.After photocatalysis for two hours,the degradation rate of Dibenzothiophene was 67.78%,and the degradation rate of Dibenzothiophene could still be maintained at about 60%after repeated use for five times.Addition of strongly oxidizing species such as H₂O₂to TiO₂photocatalysis system enhances dramatically the degradation rate of organic compounds.Dibenzothiophene can be completely degraded in one hour.Therefore,a small amount of hydrogen peroxide is introduced in the subsequent photocatalytic pretreatment of petcoke to enhance the pretreatment effect.（3）The optimum conditions of biodesulfurization were determined by single factor experiment:10 g/L of glucose,2 g/L of ammonium chloride,initial pH=7.0 and30℃of cultivation temperature.Under these conditions,the highest desulfurization rate of petcoke after 14 days is 28.25%.（4）The petcoke was pretreated by photocatalytic oxidation with Fe-doped TiO₂film,and was subjected to biodesulfurization.After six days,the desulfurization rate of petcoke was 50.09%.Compared with pure biodesulfurization,the desulfurization cycle is shortened to 6 days and the desulfurization rate is increased by 23.91%.The mechanism of synergistic desulfurization is as follows,and Fe-doped TiO₂film produces a large number of hydroxyl radicals under light,which quickly oxidizes DBT to DBTO₂.Then,with the participation of the Dsz A and Dsz B,which play a key role in cutting the C-S bond,and DBTO₂is converted to 2-HBP,and S is oxidized into SO₄^2-.The paper has 40 pictures,13 tables,and 88 references.