State Key Laboratory of Pollution Control and Resources Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
Water Res. 2013 Sep 1;47(13):4340-8. doi: 10.1016/j.watres.2013.05.028. Epub 2013 May 28.
Coagulation with the conventional coagulants such as ferric and aluminum salts is not efficient for As(III) removal. In this study Ti(SO4)2 was employed for enhanced As(III) removal and Fe2(SO4)3 was used as a reference. The removal efficiencies of As(III) by Ti(SO4)2 at pH 4.0-9.0 were greater than that by Fe2(SO4)3 by 7.39-32.8% and 3.14-48.1% for coagulants dosed at 8.0 mg/L and 12.0 mg/L, respectively. The advantage of Ti(SO4)2 over Fe2(SO4)3 for As(III) removal was more significant at lower pH, which may be ascribed to the more negatively charged surface of Ti(IV) hydroxides. To reduce As(III) from 0.2 mg/L to 10 μg/L, the necessary dosage of Ti(SO4)2 was only ≈ 50% of that of Fe2(SO4)3. The adsorption capacity of As(III) on Ti(IV) hydroxides formed in-situ was greater than that on Fe(III) hydroxides formed in-situ by ≈ 100 mg/g and several times higher than the adsorption capacities of TiO2 for As(III) reported in the literature. The presence of competing anions, silicate, phosphate and humic acid, did not alter the advantage of Ti(SO4)2 over Fe2(SO4)3 for arsenite removal. Replacing partial Ti(SO4)2 with Fe2(SO4)3 (same dosage) and applying them sequentially could achieve similar As(III) removal efficiency as single Ti(SO4)2, which could thus reduce the chemical cost. The extended X-ray absorption fine structure (EXAFS) spectroscopy indicated that As(III) form bidentate binuclear surface complexes with Ti(IV) hydroxides as evidenced by As(III)-Ti bond distances of 3.33-3.35 Å. This study revealed that Ti(SO4)2 may be an alternative coagulant for efficient As(III) removal.
对于砷（III）的去除，传统的铁盐和铝盐等凝聚剂的效果并不理想。在这项研究中，采用 Ti(SO4)2 来增强砷（III）的去除效果，并使用 Fe2(SO4)3 作为参考。在 pH 值为 4.0-9.0 的条件下，8.0mg/L 和 12.0mg/L 剂量的 Ti(SO4)2 对砷（III）的去除效率分别比 Fe2(SO4)3 高 7.39-32.8%和 3.14-48.1%。在较低的 pH 值下，Ti(SO4)2 对砷（III）的去除效果优于 Fe2(SO4)3，这可能归因于 Ti(IV)氢氧化物表面带更多的负电荷。为了将砷（III）从 0.2mg/L 降低到 10μg/L，Ti(SO4)2 的必要剂量仅约为 Fe2(SO4)3 的 50%。原位生成的 Ti(IV)氢氧化物对砷（III）的吸附容量大于原位生成的 Fe(III)氢氧化物，约为文献中报道的 TiO2 对砷（III）的吸附容量的 100 倍以上。共存的阴离子硅酸根、磷酸根和腐殖酸并没有改变 Ti(SO4)2 去除亚砷酸盐的优势。用 Fe2(SO4)3（相同剂量）替代部分 Ti(SO4)2 并依次使用它们，可以实现与单一 Ti(SO4)2 相似的砷（III）去除效率，从而降低化学成本。扩展 X 射线吸收精细结构（EXAFS）光谱表明，As(III)与 Ti(IV)氢氧化物形成双齿双核表面配合物，As(III)-Ti 键距离为 3.33-3.35Å。本研究表明，Ti(SO4)2 可能是一种替代的混凝剂，用于有效去除砷（III）。
