二硫化钼物相调控优化重金属去除效率和去除机理研究

随着现代工业的发展，水体和土壤中的重金属污染已经成为亟待解决的问题。吸附法作为重金属去除最常用的方法，其进步与发展离不开新型吸附材料的开发。近几年发展迅速的二维纳米功能材料二硫化钼（MoS2），在重金属去除方面的应用受到广泛的关注。其中，MoS2的相态是其最重要的物理性质之一，可能对MoS2的重金属去除性能产生十分重要的影响，但目前尚缺乏系统的研究。本文深入探究了MoS2的相态对重金属的去除性能的影响及其中机理，总结了MoS2与重金属离子作用的规律。在此基础上，探究了MoS2独特的二维纳米孔道性质及其对重金属去除的作用。具体研究内容及结果如下： (1) 通过水热合成的方法控制MoS2的相态组成，成功合成了1T与2H两种相态的MoS2纳米颗粒，通过批次实验和密度泛函理论计算，本研究深入探究了不同相态MoS2对两种不同类型的典型重金属离子Pb(II)和Ag(I)的去除效率和去除机理。研究结果显示，1T相MoS2对于两种类型重金属离子均显示出更高的去除容量和反应活性，这表明了MoS2的1T相在重金属去除中具有优越性。同时，本研究发现干湿状态引起的层间距变化对重金属去除效率具有重要影响，1T相MoS2在干燥后层间距的收缩导致其对Pb(II)和Ag(I)的去除容量分别下降了70%和25%。此外，研究中还具体分析了MoS2去除Pb(II)时表面吸附和沉淀的贡献占比，发现1T-MoS2在厌氧环境下对Pb(II)的去除主要为表面吸附作用，其贡献达90%以上。 (2) 为了探究不同介质中MoS2相态对去除重金属的影响，本研究对比了不同相态MoS2修复含Pb(II)土壤的效果。利用水热合成的1T相、2H相和天然矿物MoS2粉末修复Pb(II)污染土壤，结果表明，不论是土壤中Pb(II)的浸出变化还是植物对Pb(II)的吸收，1T相MoS2均有更好的修复效果，这符合两种相态MoS2与重金属Pb(II)的作用规律。同时，MoS2的加入还缓解了Pb(II)对植物根部的毒性。进一步研究发现，MoS2在土壤修复过程中具有优异的动力学速率，土壤中Pb(II)浸出量的下降速率明显优于Si基和C基材料，这为MoS2的实际应用提供了潜在可能性。 (3) 通过化学剥离的方法制备了单层MoS2纳米片，并探究了其去除重金属Cr(VI)的效率和机理。实验结果表明，单层MoS2纳米片具有高效的去除Cr(VI)能力，其机理主要包括还原、吸附和沉淀三部分。同时，本研究发现单层MoS2纳米片中1T相组分会更优先地与Cr(VI)反应，这再次证明了1T相在重金属去除中具有更高的反应活性。最后，通过重新堆叠单片层MoS2构造层状纳米孔道结构，并利用其层间距干燥收缩现象，最终实现对Cr(III)的捕获、去除和固定。这一探索对深入理解二维材料的结构、性质及环境应用具有十分重要的意义。

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