锑（Sb）是一种有潜在致癌毒性的类金属环境污染物，环境中的锑主要以五价（Sb(V)）和三价（Sb(III)）两种价态存在，是一种氧化还原敏感性元素。采矿和冶炼活动是矿区锑污染的重要来源，而施氏矿物是一种常见于酸性矿山环境中的高铁硫酸盐氢氧化矿物。以往的研究发现施氏矿物对Sb具有很强的吸附能力，而有关吸附及氧化微观固定机理和分子机制的研究仍不深入。本论文通过吸附批实验、表面表征技术（XAFS、XRD、TEM SAED、FTIR等）、理论计算（DFT）和表面络合模型（SCM）系统研究了Sb在施氏矿物上的微观固定机理、Sb(III)的氧化和电子转移路径及其主要驱动力，并考察了不同环境条件（pH、Sb负载量、共存离子等）对吸附和氧化的影响。研究结果对深入理解矿山环境中锑的环境地球化学过程及归趋具有重要的理论意义。本论文的主要研究结果如下：

（1）系统阐明了Sb(V)在施氏矿物表面及孔道内的微观固定机理及主要驱动力，完善了施氏矿物结构的计算化学模型。结果表明，施氏矿物对Sb(V)具有很强的吸附能力和吸附稳定性。Sb(V)可以通过与施氏矿物的硫酸根发生阴离子置换反应或与羟基发生络合被吸附在施氏矿物表面及孔道内。低Sb(V)负载条件下Sb(V)除了可以生成双齿单核、双齿双核两种吸附产物外，还会部分掺入到施氏矿物骨架结构中；而高Sb(V)负载条件下Sb(V)只生成双齿单核、双齿双核两种吸附产物，不发生掺入骨架结构的行为。Sb(V)在施氏矿物表面及孔道内形成吸附和掺入产物引起的显著能量降低（吸附能）是其被稳定保留的主要驱动力，这种驱动力也使施氏矿物更加稳定，在宏观上体现为将施氏矿物稳定存在的pH窗口拓宽至中性甚至碱性条件。

（2）揭示了Sb(III)在施氏矿物上的固定机理及电子转移路径。施氏矿物对Sb(III)的强大去除能力主要通过阴离子置换反应、表面络合反应和形成Sb₂O₃表面沉淀三种途径实现。Sb(III)可与施氏矿物发生直接电子转移促进施氏矿物的还原溶解。氧气不仅会促进溶液中Fe(II)与Sb(III)的共氧化，还会影响Sb(III)在施氏矿物上的固定机理，促进锑华的生成。Sb(III)在施氏矿物表面及孔道内形成的吸附产物引起的显著能量降低（吸附能）是其被稳定保留的主要驱动力，并且孔道内双齿双核共角络合物和双齿单核共边络合物中Sb的5s、5p轨道、表面O配体的2p轨道和与O配体连接的Fe的3d轨道组合形成的新分子轨道打破了原有的Sb 5s轨道电子向Fe 3d轨道的跃迁禁阻，是Sb(III)氧化的直接驱动力。

（3）阐释了常见共存阳离子Cu(II)/Pb(II)/Zn(II)与Sb(V)在施氏矿物上的协同吸附微观机理。Cu(II)/Pb(II)/Zn(II)阳离子可与Sb(V)在施氏矿物表面形成结构相似的Fe-Sb(V)-Cu(II)/Pb(II)/Zn(II)三元表面络合物，此外，Sb(V)与Pb(II)还可通过生成表面沉淀显著增强两者在施氏矿物上的固定。阳离子-Sb(V)-施氏矿物三元络合物都具有比Sb(V)-施氏矿物二元络合物更强的吸附能，从微观反应能量角度可以对体系起到强烈的稳定作用，这是Sb(V)和三种阳离子在施氏矿物表面共吸附协同效应的主要驱动力。

Antimony (Sb) is a toxic trace element with potential carcinogenicity. It has oxidation-reduction activity and mainly exists in the environment as Sb (V) and Sb (III). Schwertmannite is a frequently observed ferric oxyhydroxysulfate mineral in acid mine drainage (AMD) and is one of the main sinks of heavy metal pollutants in mining areas. Previous studies have focused on the adsorption capacity of Sb by schwertmannite, while the micro-immobilization mechanism is scarcely studied. Therefore, this thesis studies the micro-immobilization mechanism of Sb on schwertmannite, the oxidation mechanism of Sb(III) and its main driving force through batch experiments, surface characterization techniques (XAFS, XRD, TEM SAED, FTIR, etc.), theoretical calculation (DFT) and surface complexation model (SEM), and examines the effects of different environmental conditions (pH, Sb loading, coexisting ions, etc.) on the micro- immobilization mechanism. The main results are as follows:

(1) The micro immobilization mechanism and main driving force of Sb(V) on the surface and in the tunnel of schwertmannite are systematically clarified, and the computational chemistry model for the structure of schwertmannite is improved. The immobilization of Sb(V) mainly originated from the exchange of Sb(V) with hydroxyl and sulfate. Under low Sb(V) loading conditions, Sb(V) can not only form two kinds of adsorption products, but also partially blend into the Fe-O framework of schwertmannite. However, under high Sb (V) loading, Sb (V) only generates two kinds of adsorption products without the behavior of incorporation. The significant energy reduction (adsorption energy) caused by the formation of adsorption and incorporation products of Sb(V) is the main driving force for its stable retention, and the adsorption/incorporation products in the tunnel are more stable than that on the surface. The complexes formed by Sb(V) on/in schwertmannite reduces the energy of schwertmannite and broaden the pH window of its stable existence to neutral or even alkaline conditions.

(2) The immobilization mechanism and electron transfer paths of Sb(III) on schwertmannite have been revealed. Sb(III) immobilized by schwertmannite through three ways: anion exchange reaction, surface complexation reaction and formation of Sb₂O₃ surface precipitation. Sb(III) can promote the reduction and dissolution of schwertmannite by direct electron transfer. In aerobic environment, O₂ will not only promote the co-oxidation of Fe(II) and Sb(III), but also affect the immobilization mechanism of Sb(III) on schwertmannite by promoting the formation of valentinite. The significant energy reduction (adsorption energy) caused by the sorption products of Sb(III) on/in schwertmannite is the main driving force for its stable retention. The combination of the 5s and 5p orbitals of Sb, the 2p orbitals of the surface O ligand and the 3d orbitals of Fe connected with the O ligand in the bidentate binuclear complex and bidentate mononuclear complexes in the tunnel breaks the transition barrier of the original Sb 5s orbital electrons to the Fe 3d orbital, which is conducive to the direct transfer of Sb(III) valence electrons to schwertmannite.

(3) The microscopic mechanism of synergistic adsorption of common coexisting cations Cu(II)/Pb(II)/Zn(II) and Sb(V) on schwertmannite is explained. Cu(II)/Pb(II)/Zn(II) divalent cations can form Fe-Sb(V)-Cu(II)/Pb(II)/Zn(II) ternary surface complexes with similar structure with Sb(V), and promote the adsorption of cations and Sb(V) on schwertmannite simultaneously. The co-adsorption mechanism of Sb(V) and Pb(II) is different from that of Cu(II) and Zn(II). In addition to the formation of ternary complex, the immobilization of Sb(V) and Pb(II) on schwertmannite can be significantly enhanced by the formation of surface precipitation. Cation-Sb(V)-schwertmannite ternary complexes has stronger adsorption energy than Sb(V)-schwertmannite binary complexes, which is the main driving force for the adsorption amount of Sb(V) and three cations in the surface of schwertmannite to be greater than the adsorption amount in the binary systems.