| In recent years,zero-valent iron(ZVI)has been extensively explored due to its strong reduction,large specific surface area,and wide application potential.However,ZVI is susceptible to passivation and agglomeration in solution,resulting in poor pollutants removal.To overcome the limitations of ZVI passivation and agglomeration,limonite,pyromorphite,and anthracite were used as raw materials to prepare molybdenum sulfide modified ZVI via the carbothermal reduction method(MoS_x@ZVI).An experimental study was conducted to determine the effect of preparation conditions on the removal of simulated acidic orange G(OG)by MoS_x@ZVI.In the meanwhile,the ideal preparation conditions and performance of MoS_x@ZVI were explored,a comparative OG removal test was conducted between MoS_x@ZVI and ZVI,and the OG degradation process was further investigated.The main conclusions of the investigation are as follows:(1)A theoretical study of the preparation of MoS_x@ZVI by carbon thermal reduction and an investigation into the influence of roasting parameters on the OG removal test of MoS_x@ZVI were conducted.Based on the results of thermodynamic calculations,it was determined that the theoretical preparation of MoS_x@ZVI by carbon thermal reduction was feasible.The MoS_x@ZVI obtained under different roasting conditions was analyzed based on experiments on the effect of roasting conditions on the removal of OG by MoS_x@ZVI and by scanning electron microscopy(SEM),X-ray diffraction(XRD)and sulfur(S)content.The findings demonstrated that the optimal preparation parameters for MoS_x@ZVI are 6%pyromorphite,a roasting temperature of 1000℃,25%anthracite,and a roasting period of 60 minutes.(2)The optimally produced MoS_x@ZVI was characterized and analyzed by scanning electron microscopy and energy spectroscopy(SEM-EDS),X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS)to analyze the phase composition.Using a specific surface area and porosity analyzer(BET)and contact angle meter,the specific surface area and hydrophobicity of MoS_x@ZVI produced under ideal circumstances were determined(WCA).The results indicate that the core of MoS_x@ZVI is predominantly composed of Fe-Mo-C alloy,whereas the shell may be composed of molybdenum sulfide,FeS,C,molybdenum oxide,and iron oxide,with a specific surface area of 18.9 m~2/g,a pore size of approximately 15.9 nm,and a contact angle of 113.2 degrees.(3)Under varying parameter settings,MoS_x@ZVI and ZVI systems were evaluated on their capacity to remove OG.The findings indicated that the MoS_x@ZVI system was more successful at eliminating OG than the ZVI system,and the removal rate was higher.(4)The mechanism of OG removal by the MoS_x@ZVI system was analyzed by XRD,Fourier transform near infrared spectroscopy(FTIR),UV-visible absorption spectroscopy(UV-vis)and gas chromatography-mass spectrometry(GC-MS).The results demonstrated that Fe0 in the MoS_x@ZVI core was primarily responsible for the elimination of the OG.In addition,the absence of nitrogen-nitrogen double bond peaks in the FTIR spectrum after the reaction indicates that there was no adsorption during the reaction.During the breakdown of OG,novel intermediates were produced,the naphthalene ring oxidized more readily than the benzene ring,and the TOC removal rate was around 35.0%.Finally,a potential OG degradation mechanism was presented. |
