Study On The Bioreduction Performance And Mechanism Of Te(Ⅳ) By Fe(Ⅲ) Regulation And Sulfur Autotrophic Process

Tellurium and its compounds have been widely used in industrial fields in recent years,resulting in the increase of tellurium content in industrial wastewater.In particular,tellurite [Te(Ⅳ)],which is highly toxic in the environment,will cause water pollution in large quantities.In order to solve the problem of slow bioreduction efficiency of Te(Ⅳ)wastewater and how to treat Te(Ⅳ)on a large scale,ferric citrate with low cost,high bioavailability and wide source was used to improve the bioreduction efficiency and achieve the purpose of efficient and rapid reduction of Te(Ⅳ).The acceleration mechanism is expounded from the perspectives of electron generation,electron transfer and energy level.Te(Ⅳ)wastewater was continuously treated by constructing a laboratory-scale sulfur autotrophic biological process.Furthermore,the bioreduction performance of Te(Ⅳ)and the mechanism of Te(Ⅳ)bioreduction by sulfur autotrophic biological process were discussed from various angles.The main research results are as follows:(1)To explore the bioreduction performance of bioavailable iron citrate[Fe(Ⅲ)] on Te(Ⅳ)and its acceleration mechanism.The experimental results showed that 5 m M Fe(Ⅲ)increased the bioreduction efficiency of Te(Ⅳ)from 0 to 12.40 mg/(L·h).Using cyclic voltammetry,electrochemical impedance spectroscopy and Tafel to study electron transport in the Te(Ⅳ)bioreduction process,Fe(Ⅲ)significantly increased NADH production(electron production)to 138%.Fe(Ⅲ)stimulated the increase of cytochrome c,thus increasing the electron transport system activity.At the same time,Fe(Ⅲ)promoted the secretion of extracellular polymeric substances(EPS)and reduced the membrane permeability,thereby reducing the toxicity of Te(Ⅳ).The increase of ATP provided energy for the metabolic process of Te(Ⅳ)bioreduction and played a positive role in cell activity.The coating of EPS on the surface of tellurium nanoparticles increases its stability.(2)The bioreduction performance and mechanism of sulfur autotrophic biological process for treating Te(Ⅳ)wastewater were evaluated.The research showed that the sulfur autotrophic biological process can effectively biologically reduce Te(Ⅳ).When the initial concentration was 5-30 mg/L,the reduction efficiency was kept above 90%.The mechanism study showed that Te(Ⅳ)stimulated the increase of redox substances and electron transfer system activity in polymeric substances,which was helpful for electron transfer.The improvement of cell membrane permeability was beneficial to electron shuttle transfer.A large amount of ATP provided energy for various life activities during the Te(Ⅳ)bioreduction.Catalase slowed down the oxidative stress induced by Te(Ⅳ).Meanwhile,the activities of nitrate reductase,nitrite reductase,sulfide: quinone oxidoreductase and sulfur dioxygenase played an active role in the bioreduction and sulfur oxidation of Te(Ⅳ).C10-HSL and C14-HSL may regulate the change of microbial community during the Te(Ⅳ)bioreduction,which made electroactive bacteria,heavy metal reducing bacteria and sulfur oxidizing bacteria rich.This study provided a new idea for biological treatment of Te(Ⅳ)wastewater from different perspectives,and provided theoretical support for efficient practical engineering treatment of Te(Ⅳ) wastewater.