Heavy metal pollution of water is a global concern, which adversely affects human health because of its resistance to biodegradation and thus its transmission in the food chain via bioaccumulation. Nano zerovalent iron (nZVI) is very effective for the removal of heavy metals and is cost effective in terms of production. However, the main problems of nZVI are agglomeration and ease of oxidation. Several stabilization materials have been implemented to limit the aggregation of nZVI, such as silica, activated carbon and biochar. In comparison, as a support material, biochar possesses a large surface area, high stability and strong adsorption capacity, as well as being obtainable from various types of materials. Thus, this work aims to establish the opportunities available on the use of biochar-supported nZVI in utilizing its ability to stabilize and immobilize the nZVI. This review also reports the preparation, modification and surface enhancement of biochar, nZVI and biochar-nZVI for practical use as adsorbents. This review shows that modifications of the nZVI surface can help in their stabilization and reduction of aggregation. Additionally, this review is able to increase one's understanding of heavy metal sorption behavior by biochar-supported nZVI as it is the important as heavy metal sorption is driven based on biochar-nZVI type and heavy metal species which involve numerous mechanisms, including physical binding, complexation, ion exchange, surface precipitation and electrostatic interactions. Furthermore, this research reviews the adsorption parameters, including the crucial adsorption mechanism of heavy metals onto biochar-nZVI; the reusability of the biochar-nZVI is also discussed in this work. © 2022 Society of Chemical Industry (SCI).

中文翻译：

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生物炭负载纳米零价铁有害重金属吸附剂的制备、表面增强及吸附机理综述

水的重金属污染是一个全球性的问题，由于它对生物降解具有抵抗力，因此它通过生物蓄积在食物链中传播，因此对人类健康产生不利影响。纳米零价铁 (nZVI) 对去除重金属非常有效，并且在生产方面具有成本效益。然而，nZVI 的主要问题是结块和容易氧化。已经实施了几种稳定材料来限制 nZVI 的聚集，例如二氧化硅、活性炭和生物炭。相比之下，作为载体材料，生物炭具有比表面积大、稳定性高、吸附能力强等特点，可由多种材料获得。因此，这项工作旨在确定使用生物炭支持的 nZVI 的机会，以利用其稳定和固定 nZVI 的能力。本综述还报道了生物炭、nZVI 和 biochar-nZVI 的制备、改性和表面增强，作为吸附剂的实际应用。这篇综述表明，对 nZVI 表面进行修改有助于稳定它们并减少聚集。此外，这篇综述能够增加人们对生物炭负载的 nZVI 重金属吸附行为的理解，因为它很重要，因为重金属吸附是基于生物炭-nZVI 类型和重金属种类驱动的，涉及多种机制，包括物理结合，络合、离子交换、表面沉淀和静电相互作用。此外，本研究回顾了吸附参数，包括重金属在生物炭-nZVI 上的关键吸附机制；本工作还讨论了 biochar-nZVI 的可重复使用性。© 2022 化学工业协会 (SCI)。