Zhao Zezhou, Lou Wei, Zhong Delai, Shi Yao, Zhang Fengjiao, Wang Linling, Wu Xiaohui, Sheng Anxu, Chen Jing
Hubei Key Laboratory of Multi-media Pollution Cooperative Control in Yangtze Basin, School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Hunan Provincial Engineering Research Center for Resource Recovery and Safe Disposal of Industrial Solid Waste, Hunan Heqing Environmental Technology Company Limited, Changsha 410032, China.
Sci Total Environ. 2024 Nov 1;949:175241. doi: 10.1016/j.scitotenv.2024.175241. Epub 2024 Aug 2.
Engineering black carbon (e.g. biochar) has been widely found in natural environments due to natural processes and extensive applications in engineering systems, and could influence the geochemical processes of coexisting arsenic (As) and Fe, especially when they are exposed to oxic conditions. Here, we studied time-varying kinetics and efficiencies of As immobilization by solid-phase Fe (Fe) and Fe (Fe) in Fe-As-biochar systems under both anoxic and oxic conditions at pH 7.0, with focuses on the effects of biochar surface and biochar-derived dissolved organic carbon (DOC). Under anoxic conditions, Fe could rapidly immobilize As via co-adsorption onto biochar surfaces, which also serves as the dominant pathway of As immobilization at the initial stage of reaction (0-5 min) under oxic conditions at high biochar concentrations. Subsequently, with increasing biochar concentrations, Fe precipitation from aqueous Fe (Fe) oxidation (5-60 min) starts to play an important role in As immobilization but in decreased efficiencies of As immobilization per unit iron. In the following stage (60-300 min), Fe oxidation is suppressed and leads to As release into solutions at >1.0 g·L biochar. The decreasing efficiency of As immobilization over time is attributed to the gradual release of DOC into solution from biochar particles, which significantly inhibit As immobilization when Fe is generated from Fe oxidation in the vicinity of biochar surfaces. Specifically, 4.06 mg·L of biochar-derived DOC can completely inhibit the immobilization of As in the 100 μM Fe system under oxic conditions. The findings are crucial to comprehensively understand and predict the behavior of Fe and As with coexisting engineering black carbon in natural environments.
由于自然过程以及工程系统中的广泛应用，工程黑碳（如生物炭）已在自然环境中广泛存在，并且可能影响共存的砷（As）和铁的地球化学过程，尤其是当它们暴露于有氧条件下时。在此，我们研究了在pH 7.0的缺氧和有氧条件下，Fe-As-生物炭体系中固相铁（Fe）和Fe（Fe）固定As的时变动力学和效率，重点关注生物炭表面和生物炭衍生的溶解有机碳（DOC）的影响。在缺氧条件下，Fe可通过共吸附到生物炭表面快速固定As，这也是在高生物炭浓度的有氧条件下反应初始阶段（0 - 5分钟）As固定的主要途径。随后，随着生物炭浓度增加，Fe（Fe）氧化产生的Fe沉淀（5 - 60分钟）开始在As固定中发挥重要作用，但单位铁固定As的效率降低。在随后阶段（60 - 300分钟），Fe氧化受到抑制，导致在生物炭>1.0 g·L时As释放到溶液中。As固定效率随时间降低归因于DOC从生物炭颗粒逐渐释放到溶液中，当在生物炭表面附近由Fe氧化生成Fe时，DOC会显著抑制As的固定。具体而言，4.06 mg·L的生物炭衍生DOC可在有氧条件下完全抑制100 μM Fe体系中As的固定。这些发现对于全面理解和预测自然环境中与共存工程黑碳相关的Fe和As的行为至关重要。
