| This thesis established chalcocite,indigenous photoelectron microorganism and U???-As???with different complex forms to stud y the process of the growth and metabolism of Kocuria rosea promoted b y photogenerated electrons of local chalcocite semiconductor mineral in controlling the chemical valences of U-As.Competition and s yn ergy effects will be anal ysis while U??/??-As??/??with different complex forms reduced b y photo electric microbe after utilize photogenerated electrons,b y contrast reduction efficiency and kinetics of photoelectron reduction of sulfide semiconductor,bioreduction of microbial cells with different surface potentials and s ynergy of Cu 2S and microbe.The boundary conditions of the U-As orientation transition regulated b y optoelectronic/microbial will be determined.The process of electron transfers and coupling effect mechanism in the U??/??-As??/??s ystem with sulfide semiconductor,microbe and s ynerg y of Cu 2S and microbe will be clarified.The detailed conclusions are as follows:?1?The temporal and spatial distribution characteristics of uranium/arsenic in surface water,river sediment and soil in the multi-metal mining area and the main minerals of uranium/arsenic were identified.The average concentration of uranium and arsenic in the three surface runoffs in the mining area is about 0.5 mg/L,and the highest is 72 mg/L.The average uranium concentration in soil in 2014was 160 mg/kg,up to 250 mg/kg;the concentration of arsenic in soil was as high as 1800 mg/kg,about 10 times the concentration of uranium.By 2017,the concentration of arsenic in the soil is more than 10 times lower than that in 2014.The average arsenic content in the soil is onl y50 mg/kg,and the highest concentration is less than 150 mg/kg.Climatic factors,engineering repairs such as cement dams and bioremediation projects have a major impact on uranium and arsenic content in the soil.There is a significant negative corre lation between the distribution of uranium and arsenic in soil.The main minerals of uranium/arsenic in this mining area are mainl y Pitchblende,magnesia-phosphorus-uranite,copper-arsenic-uranite,vanadium-aluminum-uranite,vanadium-calciumuranite,niobium-titanium uranite,rubitite,water-calcium carbonate uranite,sodium-uranite,arsenic-iron-copper ore.?2?The tolerance of Kocuria rosea to uranium and arsenic,the uranium-arsenic reduction behavior in ionic and mineral phases,and the uranium/arsenic/iron conversion and mineralization behavior in uranium-toxic sand system were clarified.In the reduction behavior of solution uranium-arsenic b y Kocuria rosea,the higher the concentration of coexisting arsenic,the higher the removal rate of uranium,indicating that arsenic plays an active role in the uranium migration in environment.Kocuria rosea first interacts with the surface of the arsenic-uranium mica mineral through the P=O,C=O and COO-groupsinthecellmembranephospholipids,proteinsand pol ysaccharides,and then adheres to the mineral surface and graduall y forms a biofilm.After 24 h,As???in the mineral lattice has been transformed into As???b y microorganisms,but U???has not been reduced until 48 h.According to the change of bond le ngth,bond angle and bond energ y of As-O tetrahedron and U-O octahedron,it can be concluded that lattice damage did not occur because As???in the mineral lattice is converted into As???.Both Thioba cillus ferrooxidans and uranium???can significantl y accelerate the oxidative dissolution of the arsenop yrite.The release of arsenic and iron in the dissolution process of arsenop yrite has obvious correlation.Oxidizing microorganisms play an important role in the ox idation of arsenop yrite,and reducing mic roorganisms may only promote the reduction of uranium b y arsenopyrite.Uranium???also significantl y accelerates the dissolution of the arsenop yrite.The main phases of the product are Pitchblende,scorodite and ferrous arsenic mica.?3?The s ynthesis pr ocess and characteristics of Chalcocite,the electrochemica l reduction behavior of uranium???/arsenic???,the uranium???/arsenic??/??behavior and interface processes regulated b y Chalcocite are clarified.The flavin substances secreted b y microorganisms can significantl y accelerate the electron transfer efficiency and reduce the star ting point potential of uranium???reduction.However,for arsenic???,it onl y increases the electron transfer efficiency of the s ystem without reducing the starting point potential.Whenuranium???-arsenic???coexists,uranium???-arsenic???will first form a part of the complex precipitation,while copper-based chalcocite photogenerated electrons reducing uranium???and arsenic???with obvious selectivity.It will first act with arsenic???,f ollowed b y reduction of uranium???.When the s ystem is a uranium???-arsenic???double-chamber system,the content of superox ide radical in the photocatal ytic chamber solution is significantl y reduced with time,and the change of content in superoxide radicals is obvious.The linear negative correlation trend has a correlation coefficient of 0.995.At the beginning of the reaction,a high concentration of arsenic???in the light chamber may act as a hole scavenger.?4?The elect ron transfer process and coupling mechanism of the uranium[U??/??]-arsenic[As??/??]s ystem is revealed.When uranium???coexists with diff erent concentrations of arsenic???,the removal rate of uranium???is different for single and both of Kocuria ros ea and Chalcocite,but they all show obvious S ynergies.There are two ways to transfer the photoelectrons after photocatal ysis b y sunlight.One is to directl y react with the ionic or complex pr ecipitated uranium???/arsenic???in the solution.Another one is absorbed and utilized b y Kocuria rosea in direct contact or indirect manner.The tricarbox ylic acid cycle involved in the microorganism is used b y microorganisms to produce ATP for the growth and metabolism of the bacteria itself,and then the bacte ria transfer the bioele ctron to uranium???/arsenic???.In double-chamber s ystem,photoelectrons and holes are generated after the photocatal ysis of chalcocite,and a small portion of photoelectrons can react with ox ygen to produce superox ide radical.Arse nic???is oxidized to arsenic???b y the holes and a small amount of superoxide radicals,which promotes efficient separation of photoelectrons and holes.The s ystem can simultaneousl y realize uranium???reduction/arsenic???ox idation b y photocatalytic holes?oxidation?and photoelectrons s ynergistic with Kocuria rosea?reduction?. |
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