State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin, 150090, PR China.
School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, PR China.
Chemosphere. 2021 Apr;268:128805. doi: 10.1016/j.chemosphere.2020.128805. Epub 2020 Oct 28.
Sorption of sulfonamides (SAs) on magnetite-coated biochar (MBC) is a promising approach for the remediation of antibiotic contaminants, due to its extended adsorption capacity and irreversibility. However, the actual sorption mechanisms of SAs on MBC remain unclear and the gap in knowledge hinders understanding of the fate of SAs in soils or sediments. In this study, various MBCs were prepared under different pyrolysis temperatures, with batch sorption experiments conducted using SMT as the model pollutant. Results of a two-compartment kinetic model demonstrated that aromatic components of MBCs dominated slow-sorption mechanisms, whereas the embedded magnetite further accelerated fast-sorption due to H-bonding. Modification of BC with magnetite improved the distribution coefficient (K) and isotherm linearity of SMT. Multi-parameter model results indicated that the pH-dependence of SMT sorption on BCs and MBCs occurred via a dominant mechanism of π-bond assisted H-bonding. Compared to pristine BCs, the change in pH-dependent sorption characteristics of SMT on MBC results from the regulation of π-bonding and proton configuration. Simultaneous transformation of SMT to sulfate ions on BCs or MBCs was also observed. The degradation of SMT occurred because of persistent free radicals (PFRs) on BCs or the inherent redox of iron minerals on MBCs. However, the small fraction of SMT transformed on BCs or MBCs was not found to result in overestimation of SMT sorption. This study presents the critical mechanisms of SMT sorption on pyrochars and provides novel understanding of the fate of SMT on carbonaceous materials during practical remediation applications.
磺胺类抗生素（SAs）在磁铁矿修饰生物炭（MBC）上的吸附是一种很有前途的修复抗生素污染物的方法，因为它具有扩展的吸附容量和不可逆性。然而，SAs 在 MBC 上的实际吸附机制仍不清楚，知识上的差距阻碍了对 SAs 在土壤或沉积物中命运的理解。在这项研究中，不同的 MBC 在不同的热解温度下制备，使用 SMT 作为模型污染物进行批量吸附实验。双室动力学模型的结果表明，MBC 的芳香族成分主导了慢吸附机制，而嵌入的磁铁矿由于氢键进一步加速了快速吸附。BC 用磁铁矿修饰提高了 SMT 的分配系数（K）和等温线线性。多参数模型的结果表明，SMT 在 BC 和 MBC 上的吸附对 pH 的依赖性是通过π键辅助氢键的主要机制发生的。与原始 BC 相比，SMT 在 MBC 上的 pH 依赖性吸附特性的变化是由于π键和质子构型的调节。同时也观察到 SMT 在 BCs 或 MBCs 上向硫酸盐离子的转化。BCs 上的持续自由基（PFRs）或 MBCs 上铁矿物的固有氧化还原作用导致 SMT 的降解。然而，在 BCs 或 MBCs 上转化的 SMT 分数很小，没有发现会高估 SMT 的吸附。本研究提出了 SMT 在热解炭上吸附的关键机制，并为 SMT 在实际修复应用中在碳质材料上的命运提供了新的认识。
