Bao Jianguo, Zheng Han, Tufail Haseeb, Irshad Sana, Du Jiangkun
School of Environmental Studies, China University of Geosciences Wuhan 430074 P. R. China
RSC Adv. 2018 Nov 14;8(67):38425-38435. doi: 10.1039/c8ra06622a.
Mercury (Hg) contamination of wastewater streams as a result of anthropogenic activities is a great threat to living organisms due to its acute toxicity. Therefore, current research is focused on the development of effective remediation technologies to protect human health and the environment. In this study, a novel chemical modification route was applied for the multi-functionalization of biochar in order to make it more efficient and selective for Hg(ii) removal from aqueous solution. The amino-grafted modified biochar (AMBC) having multifunctional groups on its surface was successfully synthesized through the activation of excessively available carboxylic groups (-COOH) on pre-oxidized biochar (BC-COOH). The maximum Hg(ii) adsorption capacity for the optimized amino-BC2 sample was 14.1 mg g, which was almost twice as that for pristine biochar (BC, 7.1 mg g). SEM, FTIR, and XPS techniques were applied for the confirmation of chemically grafted amino groups as well as the presence of residual -COOH groups on the biochar surface. Based on the batch adsorption data, adsorption kinetics and isotherms as well as XPS results, it was concluded that the Hg(ii) removal mechanism was purely driven by chemisorption such as electrostatic interaction, surface complexation, ion exchange with no precipitation and crystalline material being adsorbed on the adsorbent surface. These research findings not only provide a suitable adsorbent for decontamination of Hg(ii) from aqueous solution but also offer a new route for the multi-functionalization of biochar in order to make environment-friendly and inexpensive adsorbents.
由于人为活动导致废水流中汞（Hg）污染，因其急性毒性对生物构成巨大威胁。因此，当前研究集中在开发有效的修复技术以保护人类健康和环境。在本研究中，应用一种新型化学改性路线对生物炭进行多功能化，使其从水溶液中去除Hg（II）更高效且更具选择性。通过活化预氧化生物炭（BC-COOH）上过量存在的羧基（-COOH），成功合成了表面具有多功能基团的氨基接枝改性生物炭（AMBC）。优化后的氨基-BC2样品对Hg（II）的最大吸附容量为14.1 mg/g，几乎是原始生物炭（BC，7.1 mg/g）的两倍。应用扫描电子显微镜（SEM）、傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）技术来确认生物炭表面化学接枝的氨基以及残留-COOH基团的存在。基于批量吸附数据、吸附动力学和等温线以及XPS结果，得出Hg（II）去除机制完全由化学吸附驱动，如静电相互作用、表面络合、离子交换，且没有沉淀，吸附剂表面也没有吸附结晶物质。这些研究结果不仅为从水溶液中去除Hg（II）提供了一种合适的吸附剂，还为生物炭的多功能化提供了一条新途径，以制备环境友好且廉价的吸附剂。
