Iron-reducing Bacteria-mediated Migration And Transformation Of Antimony On Crystal Facet-dependence Hematite

Antimony(Sb)is widely used in various industrial products such as,catalysts and flame retardants.With the exploitation of antimony ore,antimony pollution is considered a more and more serious problem in China.The fluidity and toxicity of Sb largely depend on its oxidation state.The micro-interface process and conversion of antimony is an important process to control its occurrence form and environmental fate,and has become a hot topic in the field of environmental geochemistry.There are many interfaces of environmental media.Hematite is the most typical mineral interface because of its strong chemical stability and wide distribution in the environment.Recent studies have shown that the hematite crystals have an important influence on the interface behavior of pollutants.The difference in the arrangement of atoms on different crystal planes makes the interface adsorption and conversion processes of pollutants significantly different.The reduction reaction of microbial dissimilated iron can have an important effect on the anaerobic soil and the transformation of heavy metal pollutants.Therefore,an in-depth study of the key role played by hematite crystal planes in the adsorption and conversion of antimony under the guidance of microorganisms,and clarification of the antimony micro-interface process and conversion mechanism,will help us understand the environmental geochemical cycle of antimony,and then evaluate its risks.It is of great scientific significance to reasonably formulate antimony pollution prevention measures.In this study,three kinds of hematite exposed to different crystal facet were prepared:nanoplate{001},nanood{110}and nanopolyhedron{111}.Using XRD,FE-SEM,HR-TEM,BET methods to understand the microstructure of the three materials.Comprehensive various water chemical adsorption experiments,such as adsorption isotherm,adsorption kinetics,zeta potential experiment and p H edge,to investigate the difference in adsorption of Sb(?)and Sb(?)under the influence of different solution factors.The results showed that the adsorption process of Sb(?)and Sb(?)on the three hematite crystal facet conforms to the Langmuir model.The maximum adsorption capacity of the three hematite to Sb(?)was 7.7,16.3 and 20.1 mg/g,and the maximum adsorption capacity of Sb(?)was 5.8,8.4 and 8.9 mg/g,respectively.After the adsorption capacity was normalized to specific surface area(molecules/mm~2),nanoplant{001}have the highest adsorption capacity for Sb(?)and Sb(?).The adsorption process of Sb(?)and Sb(?)on the three hematite crystal facet conforms to the second-order reaction kinetics,and the hematite on the nanorod{110}crystal facet adsorbs antimony fastest.After adsorbing antimony,the three types of hematite materials have left shifts in the surface p Hzpc value to varying degrees,indicating that specific chemical adsorption has occurred,forming an inner complex structure.Using the charge distribution multi-site complex model(CD-MUSIC),the reactions occurring at the interface of different crystal facet hematite were discussed to fit the reactions of three crystal facet hematite adsorption Sb(?)and Sb(?).The complex constant log K indicated that the nanorod{110}material has the strongest adsorption of Sb(?).The microbial experiment part explored the reduction and release of iron on three hematite crystal facets and the valence migration and conversion of adsorbed antimony under the mediation of the iron reducing bacteria Shewanella oneidensis MR-1.The results showed that the reduction of dissimilated iron by iron-reducing bacteria occurs in the anaerobic system,but there is no significant difference in the proportion of iron reduction in the three crystal hematite systems.The inoculation of iron-reducing bacteria improves the desorption rate of adsorbed antimony.The smaller the value of the reaction complexation constant log K of the adsorption of Sb(?)and Sb(?)on the three crystal faces of hematite,the corresponding desorption the higher the rate.The iron-reducing bacteria Shewanella oneidensis MR-1 promoted the oxidation of Sb(?)in the adsorbed Sb(?)system,and only the adsorbed Sb(?)system did not have Sb(?)reduction.