| Antimony（Sb）,as an important industrial raw material,has been used in many industrial fields,but at the same time it can have many negative effects on human health.With the wide application of antimony and the discharge of wastewater containing antimony,the concentration of antimony in the water environment has increased,causing serious environmental problems.Therefore,the removal of antimony from water environment has become an important research content for many researchers.The technology of removing antimony with iron-based adsorption material has been widely concerned by the researchers in the field of wastewater treatment because of its good adsorption performance and the unique performance of separating from solution and reusing for many times under the action of external magnetic field.In this study,the grinding and polishing sludge rich in hydrated cerium oxide（Ce O2·H2O）was used as the research object to treat it with different methods,and different adsorbents were obtained for antimony removal research.By comparing the antimony removal effect of the obtained adsorbents,an antimony removal adsorbent suitable for this study was obtained,and the synthesis of the adsorbent was optimized.The optimized adsorbent performs static adsorption experiments on antimony in simulated wastewater,analyzes the antimony removal factors of the adsorbent,and combines the characterization results with isothermal adsorption models and kinetic models to study the antimony removal mechanism of the synthesized adsorbents.The research results are as follows:（1）Grinding and polishing sludge obtained by high temperature drying treatment at300°C and 400°C,respectively,followed by modification treatment with sulfuric acid solution,ferric chloride solution and ferric tetroxide,etc.H2SO4-HCO（300）℃</sub>composite adsorbent、H2SO4-HCO（400）℃</sub>composite adsorbent、Fe（III）-HCO（300）℃</sub>composite adsorbent、Fe（III）-HCO（400）℃</sub>composite adsorbent、HCO（300）℃</sub>-doped-（Fe3O4）x composite adsorbent and HCO（400）℃</sub>-doped-（Fe3O4）x composite adsorbent.Comparing the effects of the six adsorbents,it was found that the HCO（400）℃</sub>-doped-（Fe3O4）x composite adsorbent had the best antimony removal effect.（2）The preparation conditions of the HCO（400）℃</sub>-doped-（Fe3O4）x composite adsorbent were optimized,and it was found that when the molar ratio of Ce/Fe was 1:0.67 and 1:1,respectively,the HCO（400）℃</sub>-doped-（Fe3O4）x composite adsorbent had the best adsorption and removal effect on Sb（III）and Sb（V）,respectively.（3）Static adsorption experiment was used to optimize the experimental conditions for the adsorption and antimony removal of HCO-doped-（Fe3O4）x composite adsorbent.It was found that under the conditions of p H of 3 and 2,the dosage of adsorbent was 0.2g/L and25℃,the maximum adsorption amounts of Sb（III）and Sb（V）reached 44.46mg/g and47.91mg/g at 3h and 6h,respectively.（4）The HCO-doped-（Fe3O4）x composite adsorbent was coated with SA to prepare HCO-doped-（Fe3O4）x/SA microspheres（SAB）,and its characterization and antimony removal effect were studied.The results showed that the element composition and phase（main compound composition）of HCO-doped-（Fe3O4）x composite adsorbent were not affected after SA coating.However,the surface area of the HCO-doped-（Fe3O4）x composite adsorbent was reduced due to the wrapping of SA,which caused the performance of SAB microspheres to adsorb Sb（III）and Sb（V）decreased（removal rate decreased and equilibrium time prolonged）.（5）The isothermal adsorption model and adsorption kinetic model were used to study the adsorption process.It was found that the Langmuir model can better describe the adsorption process of Sb（III）on HCO-doped-（Fe3O4）x composite adsorbent（R2>0.9）.The fit of Sb（V）adsorption process is not ideal.The Freundlich adsorption isothermal model can well describe the adsorption process of Sb（III）and Sb（V）on the HCO-doped-（Fe3O4）x composite adsorbent（R2>0.9）.The correlation coefficient R2 of the Freundlich model fitting HCO-doped-（Fe3O4）x adsorption of Sb（V）is up to 0.945,which is higher than the correlation coefficient R2（0.757）simulated by the Langmuir model.It can be seen that the adsorption process of Sb（V）by HCO-doped-（Fe3O4）x composite adsorbent should be described by Freundlich.Freundlich adsorption isotherm model constant 1/n<0.5,indicating that Sb（III）and Sb（V）are easily adsorbed by HCO-doped-（Fe3O4）x composite adsorbent.The adsorption process includes single layer（chemical）and multilayer（physical）adsorption,which belongs to collaborative adsorption.The D-R adsorption isotherm model indicates that the adsorption processes are all chemical adsorption.The adsorption kinetic model shows that the pseudo-second-order kinetic model can better fit the kinetics of HCO-doped-（Fe3O4）x composite adsorbent of Sb（III）and Sb（V）.It is suggested that the Sb（III）and Sb（V）ions are controlled by the chemical reaction at the solid-liquid interface during the adsorption process.At the same time,Elovich can also describe the kinetics of HCO-doped-（Fe3O4）x composite adsorbent of Sb（III）and Sb（V）.This implies that the heterosphere diffusion reaction also plays a certain role in the adsorption process.（6）Modern characterization methods such as SEM,EDS,SBET,XRD and XPS were used to characterize the adsorption of HCO-doped-（Fe3O4）x composite adsorbent and the residues after Sb（III）and Sb（V）adsorption,so as to further study the adsorption mechanism of HCO-doped-（Fe3O4）x composite adsorbent for Sb（III）and Sb（V）.Studies have shown that HCO-doped-（Fe3O4）x composite adsorbent with porous and multiple active sites is successfully formed by doping Fe into HCO sludge using an improved co-precipitation method.Sb（Ⅲ）/Sb（Ⅴ）ions can undergo a ligand exchange reaction with A-type hydroxyl groups in iron octahedra in Fe3O4 in the presence of HCO-doped-（Fe3O4）x composite adsorbent to form monodentate mononuclear,monodentate dinuclear Or bidentate dual-nuclear ligands to achieve the purpose of removal.The compound Fe Ce2O4 was formed during the preparation and preparation of the adsorbent.When antimony was adsorbed and removed,Fe Ce2O4 first underwent electron and ion transfer with water in the hydrolysis process to form a double-electron layer structure,and in situ generated amorphous iron oxide hydrate with high specific surface area X≡Fe-OH,and then exchanged with Sb（III）or Sb（V）on the iron oxide film by ligand exchange reaction.Sb（III）or Sb（V）can react with Ce O2 and Ce2O3 to form Ce Sb O3 or Ce Sb O4 through reaction complexation reaction to achieve the purpose of removal.In addition,Sb（III）can be oxidized and converted into Sb（V）by Ce O2 and Fe2O3 existing in the adsorbent during the adsorption process,and then removed by complexation reaction. |
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