(242e) Size-Dependent Removal of Arsenite From Aqueous Solution By Akaganeite (?-FeOOH)

Crystal size and morphology had a significant effect on its adsorption behaviors. Therefore, in the present study, we have synthesized three different sizes (from <10 nm="" to="">100 nm) and morphologies of akaganeite nanometer materials to investigate their different performance of the adsorption of the arsenite. The kinetics data of these three adsorbents showed little difference and were best described by the pseudo-first-order and pseudo-second-order equation which assumed that the adsorption rate depended on both physical and chemical adsorption. The adsorption equilibrium isotherm fitted a Langmuir isotherm model well and the maximum loading capacity could reach 790 mg of arsenite/g of adsorbent. The value was comparatively higher than previously reported. This was due to the high specific surface and the unique combination between akaganeite and arsenite. The influence of the pH on the adsorption rate was also discussed. The results showed that the adsorption rate of the size smaller than 100 nm had little change with the increasing of pH. While the adsorption rate of the size larger than 100 nm presented apparent difference as pH shifted from 7.3 to 10. A mechanism that chloride ion was replaced by arsenite had been proposed. The phosphate and silicate showed significant competitiveness with arsenite, while sulfate showed little influence. Besides, there was no change on the crystalline structure of the adsorbents after adsorption. This work offered a novel understanding on the adsorption mechanism of the arsenite by the akaganeite.