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共存离子对砷与锑在金属氧化物表面 吸附 的 影响机制研究
Alternative TitleEffect of Co-existing Ions on the Adsorption of Arsenic and Antimony on different Metal Oxides
李晓辰
Subtype博士
Thesis Advisor景传勇
2020-06
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学博士
Degree Discipline环境科学
Keyword砷 锑, 共存物质 ,二维 红外 相关光谱,表面络合模型 arsenic, Antimony, Co-existing Substance, Two-dimensional Correlation Infrared Spectroscopy, Cd-music
Abstract

      水体中砷 与 锑的 污染问题是 当今 世界 面临的 重要问题 之一 。 大量的含高浓度砷、锑的废水被排入环境中,不但对生态环境造成了极大的破坏,还对人类的 生存 产生严重的威胁。因此, 发展 更加高效的砷、锑去除 新 技术, 开发更加高效、经济 的砷、锑去除 新 材料,深入研究 砷、锑共去除的机理,成为了当今环境领域的研究热点。 此外,环境中存在大量的 共 存 物质 ,对砷、锑的去 除产生了重要的影响。然而,目前不同共存物质对砷 与 锑在不同材料表面吸附去除的影响机制仍有待进一步研究。 本 研究旨在 从分子水平上阐述砷 与 锑在 不同氧化物 表面 的吸附过程和机理,并研究 共存物质对砷 与 锑去除的影响机制。
       首先,本研究通过吸附实验 、 衰减全反射傅里叶变换红外光谱( ATR-FTIR 、 二维相关光谱 2D-COS 及 理论 计算 结合的方式,从分子水平上研究了砷 As( 和磷 在 针铁矿( α-FeOOH 、 羟基氧化镧 LaOOH 和二氧化钛( TiO2 上的竞争吸附顺序与机制,并研究了 钙的存在对 As(V)、PO43−竞争吸附的影响。借助二维相关红外光谱,证明了 As(V)比 PO43−更快地吸附到 α-FeOOH表面,而 PO43−则优先吸附到 LaOOH表面。这一结论与吸附实验得到的吸附量的结果相同,即在 α-FeOOH表面 As(V)的吸附更多,而在 LaOOH表面 PO43−的吸附量更大。在 TiO2表面尽管 As(V)和 PO43−的吸附量非常地接近,但是二维相关红外光谱技术表明, As(V)的吸附速率比 PO43−更快。 晶体轨道哈密顿 布居 分析( COHP 的结果也证明,在 α-FeOOH和 TiO2表面, As(V)的络合物 在 能 量 上更加 地 稳定,而在 LaOOH表面 PO43−的吸附更加优先。 此外,As(V)与 PO43−在 LaOOH表面 形成的络合物 最稳定, 在 TiO2表面 形成的络合物最不稳定。 Ca2+存在没有改变 As(V)和 PO43−在 α-FeOOH和 LaOOH表面的吸附顺序,但是却使得 As(V)和 PO43−在 TiO2上的吸附发生了变化。
     其次,针对 锑 Sb( 污染区域 地下水中 Sb(V)、 Ca2+共存的 环境问题,通过 吸附实验、 拉曼光谱( Raman 、 红外光谱( FTIR 等手段结合在分子水平上研究了 Sb(V)和 Ca2+在 TiO2表面 的共吸附机理。 结果表明, 在 pH 3~11的 范围里可以实现 Sb(V)和 Ca2+在 TiO2表面 的 共去除。 Sb(V)和 Ca2+的存在促进了彼此 在 TiO2 上的 吸附 。 Ca2+的存在可以增加 TiO2表面的正电荷, 从而促进 Sb(V)的吸附 此 外, Sb(V)和 Ca2+可以 在 TiO2 表面 形成三元表面络合物 ,并 随着Sb(V)和 Ca2+浓度的增加 进一步转化为 表面沉淀 。 当初始摩尔比 Sb(V)/Ca2+等 于1:0.5时, Sb(V)和 Ca2+的 总 吸附密度 QSb(V) + QCa随着 pH的升高而减小; 当Sb(V)/Ca2+等于 1:10时, 吸附密度 QSb(V) + QCa则随着 pH的升高而增大,这是由于此浓度下 Ca2+的 吸附 对锑钙共 去除 的贡献更大。 因此 可以通过调节 pH和Sb(V)/Ca2+比例 实现 Sb(V)和 Ca2+的 高效 共 去除。
       最后,我们研究了 酒石酸 配体 tartrate 对 三价锑( Sb( 在常见的固定床吸附材料 颗粒氢氧化铁( GFH 表面 吸附 的 影响 。 Sb的 K边 X 射线近边结构光谱( XANES 表明, 不同 pH条件下 Sb(III)在 吸附过程中 并没有发生 氧化的 现象 。 延伸 X射线吸收精细结构( EXAFS 光谱得到的 Sb-O和 Sb-Fe键的键长和配位数表明, Sb(O,OH)3在铁氧化物表面会与正八面体的 Fe(O,OH)6形成双齿双核角共享的内层络合物;此外,在 pH较高时存在正四面体的 Sb(O,OH)4与正八面体的 Fe(O,OH)6形成双齿单核的内层络合物。借助电荷分布多点络合CD-MUSIC)模型,结合 EXAFS得到的分子水平的信息,并考虑到 有机配体络合的竞争作用,我们很好 地 拟合了 Sb(III)的吸附数据。 CD-MUSIC模型的拟合结果表明, 酸性条件下 水溶液中 酒石酸 配体 与 Sb(III)的 络合 会 与 Sb(III)在GFH上的吸附产生强烈的竞争作用,从而使得 Sb(III)的吸附减少;而如果不考虑这种竞争作用,进行拟合时就会得到错误的偏低的吸附常数。根据吸附模型的拟合结果,我们利用 PhreePlot软件 绘制 出 Sb(III/V)的 pe-pH优势区间分布图。
      本研究不仅得到了 Sb(III)在 GFH上吸附的正确的表面络合常数,还为今后模拟预测不同阴离 子在水环境中竞争吸附提供了理论指导意义, 也为实际地下水和工业废水中的 砷锑吸附共去除 奠定了理论基础 。

Other Abstract

       Arsenic (As) and antimony (Sb) contamination is one of the major challenges in the world. The high concentration of arsenic and antimony in wastewater discharged by industrial production or groundwater derived from geothermal water has seriously endangered our health and environment. Therefore, developing effective new technologies, discovering efficient and economic new materials, and deeply studying the principles of efficient removal of arsenic and antimony have become the hotspots in the environment fields. Due to its high removal efficiency, low cost, and simple operation, adsorption has become one of the most widely used technologies for arsenic and antimony removal.
      In addition, there are a large number of coexisting substances in the environment, which have an important impact on the removal of arsenic and antimony. However, the effect of different coexisting substances on the adsorption and removal of arsenic and antimony on the surface of different materials remains unclear. Therefore, the purpose of this study is to explore the adsorption process and mechanism of arsenic and antimony on different adsorption materials at the molecular level, and to explain the influence mechanism of coexisting substances on the removal of arsenic and antimony.
     First, the competitive adsorption of arsenate and phosphate on α-FeOOH, LaOOH, and nano-TiO2 was studied by batch adsorption experiments and in-situ flow cell attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) coupled with a two-dimensional correlation spectroscopy approach. The two-dimensional correlation spectroscopy method allowed us to study the kinetics and adsorption sequence at a higher temporal resolution. The results showed that phosphate was adsorbed faster than arsenate by LaOOH, but arsenate was adsorbed faster than phosphate by α-FeOOH and TiO2. The adsorption sequence results implied that phosphate sorbed to LaOOH had to be remobilized to allow arsenate to be sorbed, but that sorption of phosphate by α-FeOOH and TiO2 was hindered by arsenate. This might explain why phosphate was effectasively outcompeted by arsenate sorption on α-FeOOH and TiO2, but arsenate was effectively outcompeted by phosphate when adsorbed on LaOOH. Crystal orbital Hamilton population (COHP) analysis revealed that arsenate bonding on α-FeOOH and TiO2 was stronger than phosphate bonding. In contrast, phosphate bonded more tightly than arsenate on LaOOH. The COHP results also showed that the surface complexes of arsenate and phosphate on LaOOH were more stable than those on α-FeOOH and TiO2, while the surface complexes on TiO2 were least stable energetically. The presence of calcium did not affect the arsenate and phosphate adsorption sequence on α-FeOOH or LaOOH. However, calcium reversed the adsorption sequence on TiO2, possibly resulted from the formation of ternary surface complexation on TiO2 surface.
       Second, the simultaneous removal of coexisting Ca2+ and Sb(V) in wastewater was studied by batch experiments and multiple complementary characterization techniques. The simultaneous removal of coexisting Ca2+ and Sb(V) can be achieved by adsorption onto TiO2 over a wide pH range from 3 to 11. The adsorption of Sb(V) decreased whereas that of Ca2+ increased with the increase of pH. Both Sb(V) and Ca2+ exhibited a positive effect on the adsorption of each other by TiO2. The improved adsorption of Sb(V) onto TiO2 was due to the increased  -potential and the enrichment of Ca2+ on its surface at lower Ca2+ concentrations (< 1 mmol/L), or due to the co-precipitation of roméite (Ca2Sb2O7) at elevated Ca2+ concentrations (> 10 mmol/L). Besides, the formation of a ternary complex may also account for this enhancement. Furthermore, the sum of QSb(V) + QCa decreases with elevated pH when the Sb(V)/Ca2+ ratio is 1:0.5. However, an opposite trend was observed with a lower Sb(V)/Ca2+ ratio of 1:10, contributing to a more significant adsorption of Ca2+ than Sb(V) in this situation. It proves that pH and Sb(V)/Ca2+ ratio optimization is a feasible strategy to achieve the simultaneous removal of Sb(V) and Ca2+on TiO2.
        Finally, the effect of tartaric on the removal of antimony(III) by an extensively used adsorbent GFH was investigated at the molecular level. Sb K-edge X-ray absorption fine structure (EXAFS) spectra gave Sb−O and Sb−Fe distances and compatible with a bidentate binuclear innersphere complex with trigonal Sb(O,OH)3 polyhedra sharing corners with Fe(O,OH)6 octahedra and a bidentate mononuclear inner-sphere complex but with Sb(O,OH)4 tetrahedra at alkaline pH. Experimental batch titration data were fitted using the charge-distribution multisite surface complexation (CD-MUSIC) model, constrained by the EXAFS molecular level information and taking competitive effects by the organic ligand into consideration. The proportion adsorbed at acid to neutral pH decreased as the Sb(III) concentration increased. The CD-MUSIC adsorption model indicated that this was solely caused by strong competition from tartrate complexation in solution, which lead to adsorption constants higher than those derived without taking this competition into account. The adsorption model results allow for calculating a pe−pH predominance diagram using the USGS PhreePlot code. The study provides consistent surface complexation stability constants, allowing the new database to be used also to reliably model adsorption of toxic oxyanions in anoxic aqueous environments: for example, to accurately simulate competition between Sb(III) and As(III) on different adsorbents when dissolved organic matter existed.
 

Pages127
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/43599
Collection环境化学与生态毒理学国家重点实验室
Recommended Citation
GB/T 7714
李晓辰. 共存离子对砷与锑在金属氧化物表面 吸附 的 影响机制研究[D]. 北京. 中国科学院生态环境研究中心,2020.
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