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摘要
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Commercial granular ferric hydroxide (Fe-hydroxide), manganese zeolite (Mn-zeolite), and (powder and granular) activated carbon (PAC, Norit-GAC, and Calgon-GAC) were used for exploring the removal efficiency of antimony from aqueous solutions. Fe-hydroxide exhibited the highest adsorption capacity towards Sb(III) and Sb(V). The removal efficiency followed a decreasing order: Fe-hydroxide (99.6–99.7 %) > Mn-zeolite (35.6 %–37.0 %) > Norit-GAC (8.7 %–21.6 %) > Calgon-GAC (14.5 %–16.0 %) > PAC (4.0 %–4.9 %) for removing Sb(III) as well as Fe-hydroxide (86.7 %–95.3 %) > Calgon-GAC (18.4–25.2 %) > Norit-GAC (12.7 %–16.8 %) > PAC (6.3 %–7.5 %) > Mn-zeolite (5.9%–7.4 %) for removing Sb(V). Antimony adsorption processes by Fe-hydroxide were then conducted under different conditions (pH, material dosage, contact time, co-existing foreign ion and anion, and initial antimony concentration Co). Some kinetic models (pseudo-1st-order, pseudo-2nd-order, pseudo-nth-order, and Avrami) and isotherm models (Langmuir and Freundlich) were applied for modeling data of time-dependent and equilibrium adsorption at pHeq 7.0, respectively. Sb(III) and Sb(V) exist as Sb(OH)3 ion and Sb(OH)6– anions at pH 7.0. Its maximum adsorption capacity (based on the Langmuir model; Qmax) for Sb(OH)3 ions and Sb(OH)6– anions reached 31,375 and 26,279 μg/g. Fe-hydroxide exhibited a stronger adsorption affinity and higher adsorption capacity of Sb(OH)3 ions than Sb(OH)6– anions in water. Possible adsorption mechanism was surface complexation for Sb(OH)3 and electrostatic attraction for Sb(OH)6–. Hydrogen bonding might play an integral role in adsorbing antimony onto Fe-hydroxide. Granular Fe-hydroxide can be considered a promising adsorbent for adsorbing antimony ions. |
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