| 镉砷在针铁矿界面共吸附的相互作用机制 |
| 摘要点击 1431 全文点击 397 投稿时间：2022-07-19 修订日期：2022-09-20 |
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| 中文关键词 镉(Cd) 砷(As) 共吸附 针铁矿 三元络合物 |
| 英文关键词 cadmium(Cd) arsenic(As) co-adsorption goethite ternary complex |
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| 中文摘要 |
| 通过吸附动力学和吸附热力学结合表面物理化学表征等手段，研究了As （Ⅴ）和Cd （Ⅱ）在针铁矿界面上的相互作用过程，解析了As （Ⅴ）和Cd （Ⅱ）在针铁矿界面共吸附过程中形成三元络合物的形态.结果表明：① As （Ⅴ）和Cd （Ⅱ）在针铁矿界面的吸附过程均符合准二级动力学模型，吸附以化学吸附为主；② As （Ⅴ）在针铁矿界面吸附均以内圈吸附为主，具有单层吸附的典型特征，Cd （Ⅱ）在针铁矿界面单吸附过程与As （Ⅴ）类似，而添加了As （Ⅴ）的共吸附过程则出现了外圈吸附，呈现多层吸附的典型特征；③ As （Ⅴ）和Cd （Ⅱ）共存时可通过静电作用以及形成三元络合物的方式相互促进对方在针铁矿界面上的吸附；④通过对比各种表征结果，推导As （Ⅴ）和Cd （Ⅱ）在针铁矿上共吸附过程中生成了"Fe-As-Cd"形式的三元络合物.研究结果进一步丰富了对土壤-氧化铁界面重金属元素微化学相互作用过程的理解. |
| 英文摘要 |
| Cadmium (Cd) and arsenic (As) are commonly co-adsorbed onto iron oxides in the soil environment, especially in south China. This study aimed to elucidate the regulatory mechanisms in determining the As(Ⅴ)-Cd(Ⅱ) interactions on a goethite interface after excluding pH interference. At pH 6.0, the results obtained illustrated that As(Ⅴ) and Cd(Ⅱ) adsorbed onto goethite obeyed the pseudo-second-order kinetic model, and the adsorption processes were mainly chemical adsorption. Furthermore, As(Ⅴ) adsorbed onto goethite were mainly inner ring adsorption and monolayer adsorption both in the single adsorption process and in co-adsorption processes with Cd(Ⅱ). For comparison, Cd(Ⅱ) adsorbed onto goethite also demonstrated inner ring adsorption and monolayer adsorption during single adsorption, and As(Ⅴ)-Cd(Ⅱ) co-adsorption were transformed to outer ring adsorption and multilayer adsorption processes. Through analysis by Zeta potential, X-ray diffraction, and X-ray photoelectron spectroscopy, electrostatic adsorption and formation of ternary complexes (Fe-As-Cd) were proven to be the critical mechanisms in determining the interactions between As(Ⅴ) and Cd(Ⅱ) during their co-adsorption processes. The results obtained in this study should help us to further understand the micro-chemical interaction processes of heavy metals on the soil environment. |
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