| Arsenic pollution is ubiquitous in aqueous environment,which poses a great risk on people’s health and ecological security.Adsorption is one of the most effective techniques to removal arsenic in water.The developing of materials with the characteristic of environment-friendly,efficient and low cost is kept a hot topic in the field of arsenic removal.Halloysite,one of natural existed minerals,has drawn a lot of attentions recently due to its excellent adsorption ability for many pollutants.In this thesis,two composites based on natural-borne halloysite nanomaterial（HNTs）were prepared for exploring their performances in the simultaneous removal of arsenate（As（Ⅴ））and arsenite（As（III））in aqueous samples.The main contents and results are as follows:（1）A composite named Fe3O4@SiO2@Mn-HNTs was synthesized for arsenic removal in aqueous samples.Halloysite nanotubes（HNTs）were selected as the substrate with Mn oxides loaded on the surface to enhance its arsenic adsorption ability and then grafted onto the SiO2-coated Fe3O4 microsphere to get a just enough magnetic performance facilitating the material’s post-treatment.The prepared composite was extensively characterized by instruments.Batch experiments were carried out to get the optimum test conditions for arsenic adsorption by the composite,including p H,loading amount of Mn oxides,adsorbent dosage and the co-existing ions.Results showed that:（1）The composite showed a good performance for both As（III）and As（Ⅴ）in a wide range of p H（4-11）while most coexisted ions had little influence on their removal efficiency.The capacities of the prepared composite are 3.28 mg·g-1 for As（III）and3.52 mg·g-1 for As（Ⅴ）respectively,which are comparable or better than those of many reported materials in the references;（2）The adsorption of As（III）and As（Ⅴ）on Fe3O4@SiO2@Mn-HNTs were both well fitted with the pseudo-second order kinetic model as well as the Langmuir adsorption isotherm model revealing the chemisorption between arsenic and Fe3O4@SiO2@Mn-HNTs.The adsorption process of As（III）and As（Ⅴ）were both endothermic and spontaneous displayed by the thermodynamic study;（3）Toxicity Characteristic Leaching Procedure（TCLP）and Synthetic Precipitation Leaching Procedure（SPLP）tests were carried out to access the secondary environmental risk of the composite and showed that it was quite environmentally stable and can be safely disposed;（4）The composite was successfully applied in environmental water samples indicating its great potential applicability in future.（2）A HNTs composite modified by ferric,manganese and zirconium（Fe-Mn-Zr-HNTs）was synthesized for arsenic removal in aqueous samples through flash precipitation method.Many characterization techniques were applied to analyze the morphology and structural characteristics of the composites.The influences of different factors on arsenic adsorption in water were explored through batch adsorption experiments.The results showed that:（1）Optimal adsorption conditions were obtained as follows:p H=7,the dosage of adsorbent was 2.0 g·L-1,the initial arsenic concentration was 20.0 mg·L-1 and the adsorption time was 480 minutes;（2）The maximum adsorption capacity of the composite were 11.40 mg·g-1for As（III）and 14.56mg·g-1for As（V）,respectively;（3）Mn（IV）played a major role in the oxidation of As（III）,and As（V）is adsorbed on the surface of the composites by multi metal interaction;（4）TCLP experiment showed that it had good safety and would not produce secondary pollution;（5）The composite has high safety,simple preparation and good application prospect. |
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