| In contaminated water, the high toxicity element arsenic is one of the contaminants prior to control, thus arsenic pollution in drinking water and how to remove arsenate from water have attracted much attention. By using high effective adsorbent to remove arsenate from water is a practical method, but how to prepare it is the key point. Based on the strong affinities of Fe (Ш) and Al (Ш) ions to arsenate, in this thesis, the adsorption performances of ferric hydroxide, aluminum hydroxide, manganese dioxide and composite iron-aluminum hydroxide to remove arsenate from water were investigated.The results showed that the sorption capacity of ferric hydroxide and aluminum hydroxide to As (V) ion was related to the solution pH. When the pH of solution was equal to 3～10 and initial arsenic concentration was 0.001 mol/L, 0.0001 mol/L, 0.00001 mol/L, the sorption percentage of ferric hydroxide to As (V) ion was 99.9%, 99.5% and 95% respectively and the arsenic concentration could be decreased to less than 0.05 mg/L. When the pH = 6～9 and initial arsenic solution concentration was 0.0001 mol/L and 0.0001 mol/L, the sorption percentage of aluminum hydroxide to As (V) ion was >99%; When the pH = 4 and initial arsenic concentration was 0.001 mol/L, the optimal As (V) elimination was 84.56%. At pH = 3, 7 and 12, the adsorption isotherm could be well fitted by using the Freundlich or Langmuir model with the relationship coefficient R2>0.99.Fixing the pH of solution and changing Fe (Ш)/Al (Ш) molar ratio, nine iron-aluminum hydroxide compounds have been prepared by chemical precipitation method and characterized by contemporary analytical machines such as chemical analysis, X-ray diffraction (XRD), infrared spectrum(IR), scanning electron microscopy (SEM), superficial analyzed machine and potentiometric titration. The chemical constitution, material phases, appearances, specific surface, pore volume, pore radius and superficial electron character of them have also been determined and the adsorption capability of these compounds to arsenate have been investigated too; From the component, structure, and surface character of the adsorbent and the pH, component of solution and arsenate species in solution, the possible adsorption mechanism have been discussed. The adsorption experiments showed that when the pH ranged from 5.0 to 9.0 and arsenic concentration was 2 mg/L, all compounds can make the arsenic concentration of solution decrease to less than 0.01 mg/L, the standard for drinking water set by the World Health Organization. Among them, the compound with the Fe (Ш)/Al (Ш) molar ratio of 7/3 owned the highest adsorption capacity. Furthermore, the adsorption isotherms of all compounds were well fitted with the Freundlich or Langmuir equations at pH 5.0-9.0.The adsorption mechamism experiments showed that the pH of solution, the structure and surface electric charge of iron-aluminum hydroxide were crucial factors to affect arsenic adsorption. The character of microcrystal-amorphous morphology, the small pore diameter, the big specific surface and the high equipotential point were the main reasons that these compounds have strong adsorption capability. The common co-existed ions didn't influence their adsorption abilities to As (V) ion and the desorption amount of As (V) ion mount up with the pH of desorbent increasing. The scanning microscopy (SEM) images showed that the surface pores of the absorbent with loaded As (V) were obviously smaller and more uniform than those without loaded As (V), which confirmed that the As (V) ions were adsorbed to the inner pores of the absorbent. The possible adsorption mechanism is that arsenate anions enter into the inner pores of absorbent by electrostatic interaction firstly, then form multinuclear complexes with≡Fe-OH and≡Al-OH moieties on the absorbent surface, and consequently cause the specific chemical adsorption of As (V) ion.The sorption capacity of purchasing manganese dioxide was related to the solution pH too. When the pH = 6 and initial arsenic concentration was 0.001mol/L, 0.0001mol/L, 0.00001mol/L, arsenic sorption was 23.26%, 50.62% and 98.67%, respectively. The adsorption isotherm at pH 3, 7 and 12 could be well fitted by using the Freundlich model with the relationship coefficient R~2>0.96.
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