School of Ecology and Environment Studies, Nalanda University, Rajgir, Bihar, 803 116, India.
School of Ecology and Environment Studies, Nalanda University, Rajgir, Bihar, 803 116, India.
J Environ Manage. 2022 Sep 1;317:115356. doi: 10.1016/j.jenvman.2022.115356. Epub 2022 May 25.
Chromium originates from geogenic and extensive anthropogenic activities and significantly impacts natural ecosystems and human health. Various methods have been applied to remove hexavalent chromium (Cr(VI)) from aquatic environmental matrices, including adsorption via different adsorbents, which is considered to be the most common and low-cost approach. Biochar materials have been recognized as renewable carbon sorbents, pyrolyzed from various biomass at different temperatures under limited/no oxygen conditions for heavy metals remediation. This review summarizes the sources, chemical speciation & toxicity of Cr(VI) ions, and raw and modified biochar applications for Cr(VI) remediation from various contaminated matrices. Mechanistic understanding of Cr(VI) adsorption using different biochar-based materials through batch and saturated column adsorption experiments is documented. Electrostatic interaction and ion exchange dominate the Cr(VI) adsorption onto the biochar materials in acidic pH media. Cr(VI) ions tend to break down as HCrO, CrO, and CrO ions in aqueous solutions. At low pH (∼1-4), the availability of HCrO ions attributes the electrostatic forces of attraction due to the available functional groups such as -NH, -COOH, and -OH, which encourages higher adsorption of Cr(VI). Equilibrium isotherm, kinetic, and thermodynamic models help to understand Cr(VI)-biochar interactions and their adsorption mechanism. The adsorption studies of Cr(VI) are summarized through the fixed-bed saturated column experiments and Cr-contaminated real groundwater analysis using biochar-based sorbents for practical applicability. This review highlights the significant challenges in biochar-based material applications as green, renewable, and cost-effective adsorbents for the remediation of Cr(VI). Further recommendations and future scope for the implications of advanced novel biochar materials for Cr(VI) removal and other heavy metals are elegantly discussed.
铬来源于地质成因和广泛的人为活动，对自然生态系统和人类健康有重大影响。已经采用了各种方法来从水环境污染基质中去除六价铬（Cr(VI)），包括通过不同的吸附剂进行吸附，这被认为是最常见和低成本的方法。生物炭材料已被认为是可再生的碳吸附剂，在有限/无氧条件下，由各种生物质在不同温度下热解而成，用于重金属修复。本综述总结了 Cr(VI)离子的来源、化学形态和毒性，以及原始和改性生物炭在各种污染基质中用于 Cr(VI)修复的应用。通过批量和饱和柱吸附实验记录了使用不同基于生物炭的材料吸附 Cr(VI)的机制理解。在酸性 pH 介质中，静电相互作用和离子交换主导着 Cr(VI)在生物炭材料上的吸附。Cr(VI)离子在水溶液中倾向于分解为 HCrO、CrO 和 CrO 离子。在低 pH（约 1-4）下，由于存在-NH、-COOH 和-OH 等可用官能团，HCrO 离子的可用性导致静电吸引力，这鼓励更高的 Cr(VI)吸附。平衡等温线、动力学和热力学模型有助于理解 Cr(VI)-生物炭相互作用及其吸附机制。通过固定床饱和柱实验和使用基于生物炭的吸附剂对 Cr 污染的实际地下水进行分析，总结了 Cr(VI)的吸附研究，以评估其实际应用。本综述强调了生物炭基材料作为绿色、可再生和具有成本效益的吸附剂在修复 Cr(VI)方面的重大挑战。还优雅地讨论了为 Cr(VI)去除和其他重金属去除的先进新型生物炭材料的影响提出建议和未来研究方向。
