生物炭负载纳米Fe3O4/过硫酸根协同除铊效能及其界面反应机理研究

Recently, the water pollution incidents inflicted by the toxic element thallium (Tl) are becoming increasingly frequent, thus drawing significant attention to the development of Tl removal technology. The Tl-bearing wastewater is usually treated by dosing disposable precipitants and adsorbents, the resulted sludge with high Tl content is extremely toxic and is susceptible to secondary pollution. The development of efficient and reusable materials for Tl removal and the elucidation of the associated technological principles are important steps toward the control of Tl pollution. Our preliminary tests on Tl removal using biochar-supported nano-magnetite indicate that strong alkaline conditions can greatly enhance the thallous ions adsorption, and that this magnetic composite has high regeneration ability. Further experiments suggest that the additional dosing of persulfate can improve the Tl removal and also lower the reaction pH that is efficient in Tl removal to weak alkaline level. Therefore, the mechanisms on the synergistic Tl removal and adsorbents resue regarding the biochar-supported nano-magnetite and persulfate system are worthy of further investigation. This project is proposed to address the above-mentioned scientific issues on Tl removal using the combined system consisting of persulfate and biochar-supported nano-magnetite. By using adequate experimental design and advanced characterization techniques including X-ray photoelectron spectroscopy and electron paramagnetic resonance, the preparation methods on the synthesis of reusable biochar-based magnetic composite with high surface area will be investigated. The related mechanisms on the synergistic Tl removal and the adsorbents resue will also be explored on the basis of multiple interfacial interactions. In addition, the roles of repeated surface hydroxylation, sulfate radical activation and porous biochar adsorption in the oxidation, surface complexation and reversible ions exchange regarding Tl will be elucidated. The outcomes obtained will provide scientific insights into the removal and recovery of Tl from wastewater, and will also be helpful to the establishment of the sustainable wastewater treatment technology.

近年来铊元素的水污染事件频发，关于其水处理技术研究受到极大关注。含铊废水常采用一次性药剂处理，所产生的高铊污泥毒性大，易致二次污染。研究高效、可再生除铊材料的制备与摸清其反应调控机理是当前控制铊污染的迫切任务。我们的前期实验表明，生物炭负载纳米Fe3O4在强碱性条件下有较高的一价铊去除效能，也有较好的再生潜力；添加过硫酸盐可降低该反应体系的高效除铊pH值。因此，该磁性复合材料与过硫酸根体系的协同除铊与材料再生机理值得深入研究。本项目通过合理的批式除铊实验设计，结合电子顺磁共振波谱、X射线光电子能谱等表征技术，研究高比表面积的生物炭-纳米Fe3O4复合材料的制备方法，揭示该磁性复合材料与过硫酸根协同除铊及其循环再生的界面反应机理，阐明反复表面羟基化、硫酸根自由基活化、生物炭吸附对铊的氧化、表面络合、可逆离子交换的影响规律。本研究为高效富集回收废水中铊的可持续技术研发提供理论依据与技术支持。

铊（Thallium, Tl）是一种具有高生物蓄积性的剧毒重金属元素。近年来水体铊污染事件频发，研究高效、可再生除铊材料的制备与摸清其除铊反应机理是解决水体铊污染问题的重要任务之一。磁性铁基生物炭复合材料协同氧化是含铊废水高效处理的技术，值得系统深入研究。本课题构建了可磁分离的铁基（Fe3O4/γ-Fe2O3）生物炭复合材料，考察其与过硫酸盐、次氯酸盐等氧化剂耦合除铊的界面反应过程，并探究了该复合材料的循环再生能力与再生机理。本项目相关研究成果包括：发表SCI学术论文11篇，培养研究生顺利毕业4人，申请国内外发明专利4项。研究结果表明，制备的铁基（Fe3O4/γ-Fe2O3）生物炭复合材料具有丰富的孔隙结构与表面化学基团，适合作为高效的铊吸附材料与催化氧化载体。Fe3O4-生物炭复合材料与过硫酸根除铊过程中产生羟基自由基和硫酸根自由基，促进Tl(I)氧化为Tl2O3，强化除铊效率与速率，其除铊机理包括铊氧化沉淀、表面络合与静电吸附。次氯酸根比过硫酸根具有更强的氧化除铊能力，除铊负荷可高达1123 mg/g，铁基生物炭的协同作用可显著提高除铊速率与负荷。此外，铁基生物炭复合材料协同次氯酸根工艺可对铊、镉、铅共存的多重金属废水实现有效净化，对实际工业废水、受污染河水均有较好除铊效果，表明该技术有较高的应用价值。无机稀酸（HCl、HNO3、H2SO4）在0.1 mol/L的浓度可实现铁基生物炭复合材料的稳定再生利用，经过5次吸/脱附循环使用后，铊去除率仍在99%以上。本项目为水处理过程中固体危险废物减量化提供新途径，为把铊的粗放去除转化为特异性富集回收的可持续技术开发提供科学依据。这对含铊废水的污染控制基础研究及工程应用有重要的指导意义，也将对社会经济可持续发展与环境保护作出贡献。