Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Environmental Research Institute, Chulalongkorn University, Bangkok, Thailand.
Chemosphere. 2024 Sep;364:142997. doi: 10.1016/j.chemosphere.2024.142997. Epub 2024 Aug 7.
Magnetic powdered activated carbon (Mag-PAC) is an effective adsorbent to remove hexavalent chromium (Cr(VI)) from water and can be recovered for reuse. However, the tradeoff between the adsorption performance of Cr(VI) and magnetic properties of Mag-PAC remains unclear. Herein, we prepared a series of Mag-PAC adsorbents containing various iron-oxide mass fractions with FeSO·7HO as the precursor, using a facile wet-chemical precipitation route and conducted batch experiments to evaluate the Cr(VI) adsorption performance. Results revealed that Mag-PAC was functionalized by magnetic iron oxide comprising crystalline goethite and magnetite structures. Furthermore, its adsorption performance was highly dependent on pH and was most effective at an initial solution pH of 2. Both the sorption rate constant and Cr(VI) adsorption capacity were greatly influenced by magnetization, and they gradually decreased as the iron-oxide mass fraction increased. Among the prepared adsorbents, Mag-PAC-75 (∼32% wt iron) exhibited not only an excellent Cr(VI) adsorption performance (Langmuir adsorption capacity: 75.76 mg/g) but also effective magnetic properties (saturation magnetization: 9.66 emu/g). Coexisting anions had a negligible competitive effect on Cr(VI) removal by Mag-PAC-75 at an initial pH of 2, whereas the presence of tannic acid markedly improved the Cr(VI) elimination. The presence of trivalent chromium on the surface of Mag-PAC-75 confirmed via X-ray photoelectron spectroscopy indicated that some synergistic redox reactions may occur during the sorption process. After five regeneration cycles using NaOH, Mag-PAC-75 continued to exhibit a high Cr(VI) removal efficiency and magnetic stability. These findings indicate that optimizing the adsorption performance and magnetic properties is a key factor for realizing the practical application of Mag-PAC for Cr(VI) removal. Overall, Mag-PAC may have been a promising application prospect for Cr(VI) removal from water due to its high adsorption capacity and magnetic properties, coupled with its good reusability and magnetic stability after regeneration cycles.
磁性粉末活性炭（Mag-PAC）是一种有效的吸附剂，可用于从水中去除六价铬（Cr(VI)），并可回收再利用。然而，Mag-PAC 对 Cr(VI)的吸附性能与磁性能之间的权衡关系尚不清楚。在此，我们使用简单的湿化学沉淀法，以 FeSO·7HO 为前驱体，制备了一系列含有不同氧化铁质量分数的 Mag-PAC 吸附剂，并通过批量实验评估了其对 Cr(VI)的吸附性能。结果表明，Mag-PAC 被磁性氧化铁功能化，包含结晶针铁矿和磁铁矿结构。此外，其吸附性能高度依赖于 pH 值，在初始溶液 pH 值为 2 时效果最佳。吸附速率常数和 Cr(VI)吸附容量都受到磁化的极大影响，随着氧化铁质量分数的增加而逐渐降低。在所制备的吸附剂中，Mag-PAC-75（约 32%wt 铁）不仅表现出优异的 Cr(VI)吸附性能（Langmuir 吸附容量：75.76 mg/g），而且还具有有效的磁性（饱和磁化强度：9.66 emu/g）。在初始 pH 值为 2 时，共存阴离子对 Mag-PAC-75 去除 Cr(VI)的竞争影响可以忽略不计，而单宁酸的存在则显著提高了 Cr(VI)的去除率。X 射线光电子能谱证实，Mag-PAC-75 表面存在三价铬，表明在吸附过程中可能发生一些协同氧化还原反应。使用 NaOH 进行五次再生循环后，Mag-PAC-75 继续表现出高的 Cr(VI)去除效率和磁性稳定性。这些发现表明，优化吸附性能和磁性是实现 Mag-PAC 实际应用于去除 Cr(VI)的关键因素。总的来说，由于具有高吸附容量和磁性，以及良好的再生循环后的可重复使用性和磁性稳定性，Mag-PAC 可能在水中去除 Cr(VI)方面具有广阔的应用前景。
