School of Environmental Studies & State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, 388 Lumo Rd., Wuhan, Hubei 430074, PR China.
Institute of Ecology and Environmental Governance, College of Life Sciences, Hebei University, Baoding 071002, Hebei Province, PR China.
Sci Total Environ. 2021 May 10;768:144604. doi: 10.1016/j.scitotenv.2020.144604. Epub 2021 Jan 2.
Fe-modified biochar (FeBC) has been considered for aqueous hexavalent chromium (Cr(VI)) removal, but a better understanding is needed with respect to the removal behavior, chemical processes, and removal mechanisms under aerobic and anaerobic conditions. Aqueous Cr(VI) removal was evaluated using unmodified (BC) and FeBC. The Cr(VI) was completely removed in a pH range of 2-10. The removal behavior was properly depicted using pseudo-second-order (PSO) and Langmuir models under aerobic conditions, and using PSO and Freundlich models under anaerobic conditions. Removal rate and capacity were enhanced by up to 3.8 times under anaerobic conditions. Desorption experiments indicated removed Cr in FeBC was stable except under strong acid condition. X-ray absorption spectroscopy (XAS) analysis suggested removed Cr in FeBC was 100% in Cr(III) form and bound to Fe with a bond length of 3.01 Å in the stable form of Fe(III)Cr(III)(OOH). The removal mechanisms of Cr(VI) under aerobic conditions by FeBC mainly included electrostatic adsorption, chemical reduction, and complex precipitation.
铁改性生物炭（FeBC）已被用于去除水中六价铬（Cr(VI)），但需要更好地了解在有氧和厌氧条件下的去除行为、化学过程和去除机制。使用未改性生物炭（BC）和 FeBC 评估了水中 Cr(VI)的去除。在 pH 值为 2-10 的范围内，Cr(VI)被完全去除。在有氧条件下，使用准二级（PSO）和 Langmuir 模型可以很好地描述去除行为，而在厌氧条件下则使用 PSO 和 Freundlich 模型。在厌氧条件下，去除率和容量提高了 3.8 倍。解吸实验表明，除在强酸条件下外，FeBC 中去除的 Cr 是稳定的。X 射线吸收光谱（XAS）分析表明，FeBC 中去除的 Cr 以 100%Cr(III)的形式存在，并以 3.01 Å 的键长与 Fe 结合，形成 Fe(III)Cr(III)(OOH)的稳定形式。FeBC 有氧条件下去除 Cr(VI)的机制主要包括静电吸附、化学还原和络合沉淀。
