Technische Universität Berlin, Chair of Water Quality Control, Str. des 17 Juni 135, 10623 Berlin, Germany.
Technische Universität Berlin, Chair of Water Quality Control, Str. des 17 Juni 135, 10623 Berlin, Germany.
Chemosphere. 2019 Mar;218:749-757. doi: 10.1016/j.chemosphere.2018.11.152. Epub 2018 Nov 24.
Hexavalent chromium is highly toxic and elaborate technology is necessary for ensured removal during drinking water production. The present study aimed at estimating the potential of a micro-sized iron hydroxide (μGFH] adsorbent for chromate removal in competition to ions presents in drinking water. Freundlich and Langmuir models were applied to describe the adsorption behaviour. The results show a high dependency on the pH value with increasing adsorption for decreasing pH values. The adsorption capacity in deionized water (DI) at pH 7 was 5.8 mg/g Cr(VI) while it decreased to 1.9 mg/g Cr(VI) in Berlin drinking water (DW) at initial concentrations of 1.2 mg/L. Desorption experiments showed reversible adsorption indicating ion exchange and outer sphere complexes as main removal mechanisms. Competing ions present in DW were tested for interfering effects on chromate adsorption. Bicarbonate was identified as main inhibitor of chromate adsorption. Sulfate, silicate and phosphate also decreased chromate loadings, while calcium enhanced chromate adsorption. Adsorption kinetics were highly dependent on particle size and adsorbent dose. Adsorption equilibrium was reached after 60 min for particles smaller than 63 μm, while 240 min were required for particles from 125 μm to 300 μm. Adsorption kinetics in single solute systems could be modelled using the homogeneous surface diffusion model (HSDM) with a surface diffusion coefficient of 4∙10 m/s. Competitive adsorption could be modelled using simple equations dependent on time, adsorption capacity and concentrations only.
六价铬具有高毒性，在饮用水生产过程中需要采用精细的技术以确保其去除。本研究旨在评估微纳米尺寸的氢氧化铁（μGFH）吸附剂在去除饮用水中存在的离子时对铬酸盐的去除潜力。应用 Freundlich 和 Langmuir 模型来描述吸附行为。结果表明，吸附行为高度依赖于 pH 值，随着 pH 值降低，吸附量增加。在 pH 值为 7 的去离子水中的吸附容量为 5.8 mg/g Cr(VI)，而在初始浓度为 1.2 mg/L 的柏林饮用水（DW）中，吸附容量降低至 1.9 mg/g Cr(VI)。解吸实验表明，吸附是可逆的，表明离子交换和外层络合物是主要的去除机制。对 DW 中存在的竞争离子进行了测试，以研究其对铬酸盐吸附的干扰影响。碳酸氢根被确定为铬酸盐吸附的主要抑制剂。硫酸盐、硅酸盐和磷酸盐也降低了铬酸盐的负载量，而钙离子增强了铬酸盐的吸附。吸附动力学高度依赖于颗粒尺寸和吸附剂剂量。对于小于 63 μm 的颗粒，60 min 后即可达到吸附平衡，而对于 125 μm 至 300 μm 的颗粒，则需要 240 min。在单溶质体系中，吸附动力学可以使用均相表面扩散模型（HSDM）进行模拟，表面扩散系数为 4∙10 m/s。竞争吸附可以使用仅依赖时间、吸附容量和浓度的简单方程进行模拟。
