Hybrids Of Mycelium Biochar And Molybdenum Based Semiconductor And Their Adsorption-Photocatalytic Mechanism For Uranium Extraction

As a nuclide which widely existed in radioactive wastewater,uranium has the characteristics of strong radioactivity,long half-life,and chemical toxicity.Currently,it is challenging to search an efficient,safe,and cheap method for uranium extraction in radioactive wastewater.However,the water-soluble organics in radioactive wastewater are able to coordinate with the uranium,which hampered the development of traditional adsorption method for uranium extraction.P arallel to adsoption method,photocatalysis can reduce the water-soluble hexavalent uranium to indissolvable tetravalent one,together with the degradation of organics.Despite the advantages of photocatalysis method,the photocatalysts generally suffer from the limiting of active sites.In addition,the accumulation of hexa valent uranium on the surface of catalyst impedes the continious photocatalytic reaction.Based on the analysis above,this thesis prepared the hybrids of biochar and Mo-based semiconductor with a well-contacted interface through a bioconcentration strategy.In this case,the photogenerated electrons in Mo-based semiconductor were introduced into biochar framework which contains considerable adsorption sites.This system simultaneously achieved the adsorption-photocatalytic reduction of uranium and the degradation of soluble organics.The structure-activity relationship of the hybrids and extraction performance was also established based on the rational analysis of the corresponding mechnism.The main conclusions were as follows:?1?Molybdenum element?Mo?was enriched on the carbon skeleton of fungal hypha?FH?by bioaccumulation method.Spherical FH/MoO_x composite material was prepared by further treatment,which was used as a high-efficiency adsorption catalyst for the control of uranium in pollution water.It is found that FH/MoO_x composites have three-dimensional network structure,with typical diffraction peaks of carbon,molybdenum oxide,and rich functional groups.The results show that FH/MoO_x can effectively remove U?VI?and TA from aqueous solution.The maximum removal efficiency of FH/MoO_x composite for U?VI?and TA is 78.3%and 86.2%,respectively[TA?10 mg/L?and U?VI??8 mg/L?,pH=5.0 and T=293 K]A mechnistic study revealed that the photogenerated electrons and hole s were produced by the conduction and valent band of MoOx,respectively.The photoelectrons were transffered into the FH biochar framework,which enables the continious photoreduction of U?VI?.Meanwhile,the OH·activated by photogenerated holes and the O₂^-activated by the photoelectrons could photodegrade the TA.?2?FH/MoS₂composite was further prepared by modifying the FH/MoO_x material.Compared with FH/MoO_x,FH/MoS₂ has an ideal band gap,which makes the reduction and degradation of uranium reaction much easier.The maximum removal rates of U?VI?and TA by FH/MoO_x composite are 95.5%and 92.4%%,respectively[TA?10 mg/L?and U?VI??8 mg/L?,pH=5.0 and T=293 K].A mechnistic study revealed that the MoS₂ and FH biochar framework constructed a quasi schottky contact.In theis heterojuction,the photoelectrons of MoS₂ were transferred into FH biochar framework and thus achieved the uranium reduction on biochar.The adsorption-photocatalytic reduction performance and mechanism were influenced by the photooxidation of organics.This research finds that the bio-enrichment method can effectively form a close Schottky-like junction between molybdenum oxygen and sulfide and biomass carbon materials.And this adsorption-reduction catalytic can successfully solved the catalyst poisoning during the treatment of nuclear waste water.So,FH/Mo-basedmaterials have potential application in the treatment of nuclear waste water and even other system.