Performance of coffee husk biochar in sulfadiazine retention and remediation of soil water contamination: a batch and column study_Article

This research aimed to analyse the effect of biochar as a filtering layer in the transfer mechanisms of Sulfadiazine (SDZ), an antibiotic found in urban surface waters. Laboratory tests of kinetics and sorption isotherms of SDZ with biochar were conducted in batch conditions. Additionally dynamic adsorption analyse was performed on sand column experiments and breakthrough curves were established. As it is fundamental for understanding the SDZ transport dynamics, simulations of the breakthrough curves were performed using Hydrus-1D, for comparison. The results suggest that the biochar significantly improves the SDZ sorption rates. With a biochar filtering layer into the column, a rapid increase in sorption was observed throughout the first hours, reaching the equilibrium condition within 24 hours, and the experimental data were best fitted through a pseudo-second-order model. Additionally, a markable dependency was observed for the loading capacity of the biochar with the experimental condition of the sorption test, as the loading value without batch (41%) was below the obtained in the batch trials (53%). The simulations also showed that the Convection Dispersion Equation and the two site sorption models best fit the observed data, indicating no chemical equilibrium. Furthermore, the adjustments of the kinetics and sorption isotherms suggest that chemisorption in multiple layers was the predominant mechanism in sorption. Consequently, it is possible to infer that despite the risk SDZ represents to the environment and humans, the coffee husk biochar can be an effective alternative to mitigate its presence, or even more, to remove this contaminant from urban waters.

本研究旨在探究生物炭（biochar）作为过滤层时，对城市地表水中检出的抗生素磺胺嘧啶（Sulfadiazine, SDZ）迁移机制的影响。本研究于批量静态实验条件下，开展了磺胺嘧啶与生物炭的动力学及吸附等温线测试；此外通过砂柱实验完成动态吸附分析，并建立了穿透曲线（breakthrough curves）。为深入理解磺胺嘧啶的迁移动力学特征，本研究采用Hydrus-1D软件对穿透曲线进行模拟以作对照。结果表明，生物炭可显著提升磺胺嘧啶的吸附速率：在砂柱中添加生物炭过滤层后，吸附量在初始数小时内快速上升，并于24小时内达到平衡状态；实验数据最优拟合模型为伪二级动力学模型（pseudo-second-order model）。此外，研究观察到生物炭的吸附容量与吸附实验的操作条件存在显著相关性——非批量实验条件下的吸附容量为41%，低于批量试验中的53%。模拟结果还显示，对流弥散方程（Convection Dispersion Equation）与两位点吸附模型（two site sorption models）可最优匹配实验观测数据，表明体系未达到化学平衡。进一步的动力学与吸附等温线拟合结果表明，多层化学吸附是该吸附过程的主导机制。综上可推断，尽管磺胺嘧啶对环境及人体存在潜在风险，但咖啡壳生物炭（coffee husk biochar）可作为有效替代方案，减轻其在环境中的残留，甚至可实现城市水体中该污染物的高效去除。