砷镉在不同矿物界面的相互作用过程
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华南师范大学环境学院 广州

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国家自然科学基金项目(41877038, 42077016)和广东省“珠江人才计划”本土创新科研团队项目(2017BT01Z176)资助


Interfacial Reactions between As(V) and Cd(II) Co-adsorption onto Various Mineral Surfaces
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School of Environmental Science, South China Normal University

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Supported by the National Natural Science Foundation of China (Nos. 41877038 and 42077016) and the Local Innovative and Research Teams Project of the Guangdong Pearl River Talents Program of China (No. 2017BT01Z176)

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    摘要:

    重金属元素镉砷由于毒性高、活性大及危害强等特点,其土壤界面化学过程是土壤科学研究中的热点问题。虽然已有大量报道涉及镉砷的界面化学过程研究,但很少排除pH这一重要因子对研究结果的干扰。因此,本研究通过序批式反应,在排除pH干扰的条件下,定量研究了砷及镉在不同矿物界面(包括氧化铝、二氧化钛和高岭石)单独存在以及共同存在条件下的相互作用过程。研究结果表明:不同矿物界面上砷和镉的吸附动力学符合准二级动力学模型,化学吸附为其控速步骤;镉及砷的吸附效率(吸附量/比表面积)在不同矿物界面上均呈现出二氧化钛界面远高于氧化铝界面,而氧化铝界面高于高岭石界面;随着镉/砷浓度比的递增,镉的关键界面作用过程调控机制由静电吸附控制为主逐步转变为静电吸附与形成界面-砷-镉三元络合物共同作用,继而转变为形成表面沉淀控制;而随着砷/镉浓度比的递增,砷的关键界面调控机制发生从吸附控制为主向为沉淀控制为主的转变。该结果可为重金属元素在土壤矿物界面的微观化学作用过程及其调控措施研究提供借鉴。

    Abstract:

    【Objective】pH is the most important environmental factor influencing the reactivity of heavy metals on mineral surfaces. The purpose of this study was to investigate the interfacial reactions between As(V) and Cd(II) adsorption/co-adsorption onto different mineral surface excluding the interference of pH.【Method】Three different minerals: Al2O3, TiO2, and kaolin, were chosen and passed through 100-mesh sieve. The experiments for As(V) and Cd(II) adsorption onto the different minerals were conducted in serum bottles (Effective volume = 2 mL) at pH 6.0. The bottles containing 0.02-1 mmol?L-1 As(V), 0.02-1 mmol?L-1 Cd(II), 28 mmol?L-1 4-Morpholineethanesulfonic acid sodium salt (MES), 100 mmol?L-1 NaCl and 2.0 mg of mineral powders were placed on a rotator at 200 r?min-1 and 25 oC. Batch studies were conducted to assess the adsorption kinetics, adsorption isotherm and the influence of molar ratio of As(V) and Cd(II) on the extent of As(V)and Cd(II) adsorption.【Result】The adsorption kinetics showed that As(V) and Cd(II) adsorbed onto different mineral interfaces followed the pseudo-second-order kinetics model, and chemical adsorption was the rate-controlling steps. Furthermore, the normalized adsorption capacities of Cd(II) and As(V) were ranked as TiO2 > Al2O3 > kaolin. The adsorption abilities of As(V) and Cd(II) were enhanced by the co-existing Cd(II) and As(V). Specifically, the addition of As(V) promoted the adsorption of Cd(II) onto Al2O3, while the addition of Cd(II) enhanced As(V) adsorption onto TiO2. The synergistic effect of As(V) and Cd(II) co-adsorption was mainly controlled by the electrostatic adsorption and the ternary complex formation. Moreover, with the increase of Cd(II)/As(V) concentration ratio, the regulation mechanism of Cd(II) adsorption gradually changed from the electrostatic adsorption to the synergy of the formation of interfacial - As(V) - Cd(II) ternary complex and electrostatic adsorption, and then changed to the formation of surface precipitate. Importantly, with the increase of As(V)/Cd(II) concentration ratio, the key regulation mechanism changed from adsorption controlling to surface precipitation controlling. 【Conclusion】Electrostatic adsorption, formation of interfacial - As(V) - Cd(II) ternary complex, and surface precipitation were the critical mechanisms controlling the interfacial reactions between As(V) and Cd(II) adsorption onto various mineral surfaces at various ratios.

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引用本文

黄敏雪,管玉峰,苏子贤.砷镉在不同矿物界面的相互作用过程[J].土壤学报,DOI:10.11766/trxb202101140027,[待发表]
HUANG Minxue, GUAN Yufeng, SU Zixian. Interfacial Reactions between As(V) and Cd(II) Co-adsorption onto Various Mineral Surfaces[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202101140027,[In Press]

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