Rehman Saeed, Yousaf Sayyaf, Ye Quanyun, Chenhui Liu, Bilal Muhammad, Shaikh Ahson Jabbar, Khan Muhammad Saqib, Shahzad Sohail Anjum, Wu Pingxiao
School of Environment and Energy, South China University of Technology, Guangzhou, 510006, People's Republic of China.
Department of Environmental Sciences, COMSATS University Islamabad, Abbottabad Campus, KPK, University Road, Abbottabad, 22060, Pakistan.
Environ Sci Pollut Res Int. 2023 Feb;30(10):26107-26119. doi: 10.1007/s11356-022-23948-z. Epub 2022 Nov 9.
This study reports the mercury binding by bentonite clay influenced by cattle manure-derived dissolved organic matter (DOM). The DOM (as total organic carbon; TOC) was reacted with bentonite at 5.2 pH to monitor the subsequent uptake of Hg for 5 days. The binding kinetics of Hg to the resulting composite was studied (metal = 350 µM/L, pH 5.2). Bentonite-DOM bound much more Hg than original bentonite and accredited to the establishment of further binding sites. On the other hand, the presence of DOM was found to decrease the Hg binding on the clay surface, specifically, the percent decrease of metal with increasing DOM concentration. Post to binding of DOM with bentonite resulted in increased particle size diameter (~ 33.37- ~ 87.67 nm) by inducing the mineral modification of the pore size distribution, thus increasing the binding sites. The XPS and FTIR results confirm the pronounced physico-chemical features of bentonite-DOM more than that of bentonite. Hydroxyl and oxygen vacancies on the surface were found actively involved in Hg uptake by bentonite-DOM composite. Furthermore, DOM increased the content of Hg binding by ~ 10% (pseudo-second-order q = 90.9-100.0) through boosting up Fe reduction with the DOM. The quenching experiment revealed that more oxygen functionalities were generated in bentonite-DOM, where hydroxyl was found to be dominant specie for Hg binding. The findings of this study can be used as theoretical reference for mineral metal interaction under inhibitory or facilitating role of DOM, risk assessment, management, and mobilization/immobilization of mercury in organic matter-containing environment.
本研究报告了牛粪衍生的溶解有机物（DOM）对膨润土吸附汞的影响。将DOM（以总有机碳计；TOC）与膨润土在pH为5.2的条件下反应，监测随后5天内汞的吸附情况。研究了汞与所得复合材料的结合动力学（金属浓度 = 350 μM/L，pH 5.2）。膨润土-DOM对汞的吸附量远高于原始膨润土，这归因于更多结合位点的形成。另一方面，发现DOM的存在会降低汞在粘土表面的吸附，具体而言，随着DOM浓度的增加，金属吸附百分比会降低。DOM与膨润土结合后，通过诱导孔径分布的矿物改性，导致粒径增大（约33.37 - 约87.67 nm），从而增加了结合位点。XPS和FTIR结果证实，膨润土-DOM的物理化学特性比膨润土更为显著。发现膨润土-DOM复合材料表面的羟基和氧空位积极参与汞的吸附。此外，DOM通过促进DOM对铁的还原作用，使汞的结合量增加了约10%（准二级动力学q = 90.9 - 100.0）。猝灭实验表明，膨润土-DOM中产生了更多的氧官能团，其中羟基是汞结合的主要物种。本研究结果可为DOM抑制或促进作用下的矿物-金属相互作用、风险评估、管理以及含汞有机环境中汞的迁移/固定提供理论参考。
