| Arsenic is one of the most toxic inorganic elements and widely found in industrial waste water and natural water, which has caused seriously concern to the field of arsenic removal. In aqueous solution, arsenic is primarily existing in the forms of arsenite and arsenate. The amounts of arsenic in drinking water less than 10?g/L recommended by WHO, which hints a higher requirement for arsenic removal process. Among various methods of arsenic removal, adsorption process is considered to be one of the most simple and effective way to arsenic removal from Water.In this paper, a new spray drying-calcination process was designed for the preparation of iron-based oxide adsorbents. The ferric nitrate mixed with glucose was found to be the optimal system for preparation of the adsorbent via the exploration experiments. Unary and binary iron-based magnetic adsorbents prepared by spray drying-calcination process were used for the removal of As(III) in the aqueous solutions.Firstly, based on the ferric nitrate as the source of iron and glucose as the pore-foaming agent, the iron-based magnetic adsorbent was prepared by the spray drying-calcination method. The influence factors, such as the ferric nitrate/glucose mass ratio, calcination temperature, calcination time, p H, coexisting ions and initial As(III) concentration, were considered to identify the most suitable process conditions of preparation. Then the kinetics of As(III) adsorption were studied. The results show that the arsenic removal rate of the adsorbent reached to 80.18%, when the ferric nitrate/glucose mass ratio was 3:1 by calcination at 300°C for 3h. And the As(III) removal were more than 70% within the wide range of p H of 4~10. The presence of anions had an obvious impact on the As(III) removal, the effect of the anions followed the selectivity pattern: HPO42->Si O32->CO32-. Kinetic studies indicated that the adsorption process was fitted well with the Freundlich isotherm and pseudo-second-order kinetic model. The saturated adsorption capacity of As(III) was 81.41mg/g.Secondly, Various Fe-M binary adsorbents prepared by spray drying method were examined and Fe-Mn was found to be the best combination for arseinc removal. Then, the p H, coexisting ions and initial As(III) concentration were examined and the adsorbent regeneration experiments and kinetics experime nts were carried out on As(III) removal. The results indicated that Mn O2 can significantly improve the As(III) removal rate and arsenic removal rate to 89.76% when the molar ratio of Fe/Mn was 3:1; HPO42- was the greatest competitor with arsenic for adsorptive sites on the surface of adsorbents. Regeneration experiments indicated that Fe-Mn binary magnetic adsorbent has good reproducibility recyclability and As(III) removal rate reached to 86.04% after the desorption-oxidative regeneration of adsorbent by Na OH-Na Cl-Na Cl O; Kinetics experiments indicated that arsenic adsorption in Fe-Mn magnetic adsorbent is accord with the Freundlich isothermal adsorption and the pseudo-second-order adsorption dynamics model. The maximal adsorption capacity of arsenic was 92.62mg/g, which was higher than that of unary iron-based adsorbent. Finally, the adsorbents were characterized by SEM, XRD, XPS, Zeta potential analyzer and BET. The results showed that the prepared adsorbent was mesoporous materials with amorphous structure magnetic microspheres and had large surface area; Fe and Mn exited mainly in the oxidation state of Fe3O4 and Mn O2 respectively and As(III) was oxidized to As(V) on the surface of adsorbent. Low cost and high adsorption capability of the Fe-Mn binary oxide magnetic particles make it potentially attractive material for the removal of As(III) from water. |
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