Xiong Huixin, Xu Jing, Li Shiqing, Xu Yiqun
College of Environmental Science and Engineering, Yangzhou University, Yangzhou, Jiangsu 225127, People's Republic of China E-mail:
Water Sci Technol. 2023 Mar;87(5):1140-1158. doi: 10.2166/wst.2023.049.
Iron oxyhydroxides for heavy metal treatment have attracted wide attention. In this work, iron oxyhydroxides of isomeric FeOOH (GpI) and tunnel-structural schwertmannite/akaganéite (GpII) were selected to study chromium (Cr(III)) adsorption removal from acidic aqueous solutions by batch experiments, under various reaction time, adsorbate/adsorbent level, pH and anions. Adsorption processes well fitted to pseudo-second-order kinetics (R = 0.992-0.999, except for 0.829 for Lep). Isotherm data could be fitted by Langmuir (R = 0.901-0.985), Freundlich (R = 0.884-0.985) and Temkin (R = 0.845-0.961) models at pH 3.7. Langmuir maximum adsorption capacities (mg/g) were 10.4-18.8 (FeOOH, except for 3.08 for Gth2) in GpI, and 20.60/43.40 (Sch-Chem/Sch-Bio) and 12.80/24.70 (Aka-Chem/Aka-Bio) in GpII. Adsorption capacities would gradually increase as Cr(III) concentrations increased within 0-40 mg/L, and could be markedly affected by the SO and HPO anions. There were stable adsorption capacities at about pH 3.7, and then increased at pH 3.7-4.1. The Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results showed that adsorption mechanisms were electrostatic interaction and surface complexation. In addition, three optimal bio-/chem-schwertmannite and lepidocrocite adsorbents had good reusable properties and treating abilities of Cr(III)-polluted waters at pH 4.0. These results could provide a theoretical basis for the application of iron oxyhydroxides in removing Cr(III) from acid wastewaters.
羟基氧化铁用于重金属处理已引起广泛关注。在本研究中，选择了异构FeOOH（GpI）和隧道结构的施韦特曼石/赤铁矿（GpII）的羟基氧化铁，通过批量实验研究在不同反应时间、吸附质/吸附剂水平、pH值和阴离子条件下，从酸性水溶液中吸附去除铬（Cr(III)）的情况。吸附过程很好地符合准二级动力学（R = 0.992 - 0.999，Lep为0.829除外）。在pH 3.7时，等温线数据可以用Langmuir（R = 0.901 - 0.985）、Freundlich（R = 0.884 - 0.985）和Temkin（R = 0.845 - 0.961）模型拟合。GpI中Langmuir最大吸附容量（mg/g）为10.4 - 18.8（FeOOH，Gth2为3.08除外），GpII中为20.60/43.40（Sch-Chem/Sch-Bio）和12.80/24.70（Aka-Chem/Aka-Bio）。在0 - 40 mg/L范围内，随着Cr(III)浓度的增加，吸附容量会逐渐增加，并且会受到SO和HPO阴离子的显著影响。在约pH 3.7时吸附容量稳定，然后在pH 3.7 - 4.1时增加。傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）结果表明，吸附机制为静电相互作用和表面络合。此外，三种最佳的生物/化学施韦特曼石和纤铁矿吸附剂在pH 4.0时对Cr(III)污染的水具有良好的可重复使用性能和处理能力。这些结果可为羟基氧化铁在酸性废水中去除Cr(III)的应用提供理论依据。
