The Key Laboratory of Water and Sediment Sciences, Ministry of Education, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, PR China.
Water Res. 2013 Jun 15;47(10):3411-21. doi: 10.1016/j.watres.2013.03.035. Epub 2013 Mar 27.
Magnetic nanoparticles (MNPs) modified simultaneously with amorphous Fe and Mn oxides (Mag-Fe-Mn) were synthesized to remove arsenite [As(III)] from water. Mag-Fe-Mn particles were fabricated through heterogeneous nucleation technique by employing the maghemite as the magnetic core and Fe-Mn binary oxide (FMBO) as the coating materials. Powder X-ray diffraction, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy were utilized to characterize the hybrid material. With a saturation magnetization of 23.2 emu/g, Mag-Fe-Mn particles with size of 20-50 nm could be easily separated from solutions with a simple magnetic process in short time (within 5 min). At pH 7.0, 200 μg/L of As(III) could be easily decreased to below 10 μg/L by Mag-Fe-Mn particles (0.1 g/L) within 20 min. As(III) could be effectively removed by Mag-Fe-Mn particles at initial pH range from 4 to 8 and the residual As was completely oxidized to less toxic arsenate [As(V)]. The co-occurring redox reactions between Mn oxide and As(III) was confirmed by XPS analysis. Chloride, sulfate, bicarbonate, and nitrate at common concentration range had negligible influence on As(III) removal, whereas, silicate and phosphate reduced the As(III) removal by competing with arsenic species for adsorption sites. As(III) removal was not obviously affected by natural organic matter (up to 8 mg/L as TOC). Mag-Fe-Mn could be regenerated with ternary solution of NaOH, NaCl, and NaClO. Throughout five consecutive cycles, the adsorption and desorption efficiencies maintained above 98% and 87%, respectively. Mag-Fe-Mn had a larger adsorption capacity for As(III) (47.76 mg/g) and could remove trace As(III) more thoroughly than MNPs modified solely with either Fe or Mn oxide due to the synergistic effect of the coating Fe and Mn oxides. This research extended the potential applicability of FMBO to a great extent and provided a convenient approach to efficiently remove trace As(III) from water.
同时用非晶态 Fe 和 Mn 氧化物修饰的磁性纳米颗粒（Mag-Fe-Mn）被合成以去除水中的亚砷酸盐[As(III)]。Mag-Fe-Mn 颗粒通过使用磁铁矿作为磁性核和 Fe-Mn 二元氧化物（FMBO）作为涂层材料的异质成核技术制备。采用粉末 X 射线衍射、X 射线光电子能谱（XPS）、拉曼光谱和透射电子显微镜对混合材料进行了表征。Mag-Fe-Mn 颗粒的饱和磁化强度为 23.2 emu/g，尺寸为 20-50 nm，可在短时间内（5 分钟内）通过简单的磁处理从溶液中轻易分离。在 pH 值为 7.0 时，200 μg/L 的 As(III)可在 20 分钟内被 0.1 g/L 的 Mag-Fe-Mn 颗粒轻易降低至 10 μg/L 以下。Mag-Fe-Mn 颗粒可在初始 pH 值为 4 至 8 的范围内有效去除 As(III)，并且残留的 As 被完全氧化为毒性较低的砷酸盐[As(V)]。XPS 分析证实了 Mn 氧化物与 As(III)之间的共发生的氧化还原反应。在常见浓度范围内，氯离子、硫酸根离子、碳酸氢根离子和硝酸根离子对 As(III)去除的影响可以忽略不计，而硅酸根离子和磷酸根离子通过与砷物种竞争吸附位点而降低 As(III)的去除。天然有机物（高达 8 mg/L 的 TOC）对 As(III)去除没有明显影响。Mag-Fe-Mn 可以用 NaOH、NaCl 和 NaClO 的三元溶液再生。在五个连续循环中，吸附和解吸效率分别保持在 98%以上和 87%以上。Mag-Fe-Mn 对 As(III)的吸附容量更大（47.76 mg/g），并且由于涂层 Fe 和 Mn 氧化物的协同作用，能够更彻底地去除痕量的 As(III)，比单独用 Fe 或 Mn 氧化物修饰的 MNPs 更有优势。这项研究在很大程度上扩展了 FMBO 的潜在适用性，并提供了一种从水中高效去除痕量 As(III)的便捷方法。
