Adsorption of molybdate and tetrathiomolybdate onto pyrite and goethite: effect of pH and competitive anions.
Adsorption of molybdate and tetrathiomolybdate onto pyrite and goethite: effect of pH and competitive anions.
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DOI：
10.1016/j.chemosphere.2005.06.025
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发表时间：
2006-03
期刊：
影响因子：
8.8
通讯作者：
N. Xu;C. Christodoulatos;W. Braida
中科院分区：
文献类型：
--
作者：
N. Xu;C. Christodoulatos;W. Braida
两种主要的钼（Mo）物质，钼酸盐（MoO42-）和四硫代钼酸盐（MoS42-）在两种主要铁矿物黄铁矿（FeS2）和针铁矿（FeOOH）上的吸附旨在阐明缺氧沉积物中钼固定的可能机制。将 MoS42-（或 MoO42-）和针铁矿（或黄铁矿）在 0.1M NaCl 溶液中的悬浮液在缺氧条件下、25°C、pH 范围为 3 至 10 进行平衡。还讨论了硫酸盐、磷酸盐和硅酸盐对黄铁矿和针铁矿吸附 MoO42-和 MoS42-的竞争效应。 MoO42-和MoS42-在黄铁矿和针铁矿上的吸附通常可以通过Langmuir模型在低pH值下得到很好的描述；吸附程度是 pH 值和表面负载的函数。在低表面负载的酸性 pH 范围 (pH<5) 中观察到最大吸附。钼的吸附 (μmolg−1) 取决于 Mo 的种类和铁矿物的类型，顺序为：MoS42-–针铁矿>MoO42-–针铁矿>MoS42-–黄铁矿>MoO42-–黄铁矿。磷酸盐似乎与 MoO42- 和 MoS42- 强烈竞争黄铁矿和针铁矿的吸附位点。磷酸盐竞争效应的强度遵循MoO42--针铁矿～MoO42--黄铁矿>MoS42--黄铁矿>MoS42--针铁矿的顺序。硅酸盐和硫酸盐对MoO42-和MoS42-的吸附影响可以忽略不计。 MoS42- 铁矿物的优先吸附及其在竞争性阴离子存在下的行为表明，四硫代钼酸盐物质可能是最终的储库，并且可能控制沉积物中的钼富集。
The adsorption of two major molybdenum (Mo) species, molybdate (MoO42-) and tetrathiomolybdate (MoS42-) onto two main iron minerals pyrite (FeS2) and goethite (FeOOH) is addressed to elucidate the possible mechanisms of molybdenum immobilization in anoxic sediments. Suspensions of MoS42-(or MoO42-) and goethite (or pyrite) in 0.1M NaCl solution were equilibrated under anoxic conditions at 25°C in the pH range from 3 to 10. The competitive effects of sulfate, phosphate, and silicate on the adsorption of MoO42-and MoS42-by pyrite and goethite are also addressed. Adsorption of MoO42-and MoS42-on pyrite and goethite is in general well described by a Langmuir model at low pH; the extent of sorption is a function of pH and the surface loading. Maximum sorption is observed in the acidic pH range (pH<5) at low surface loading. The adsorption of molybdenum (μmolg−1) depends upon Mo species and on the type of iron mineral following the order: MoS42-–goethite>MoO42-–goethite>MoS42-–pyrite>MoO42-–pyrite. Phosphate appears to compete strongly with MoO42-and MoS42-for the sorption sites of pyrite and goethite. The strength of the phosphate competitive effect follows the sequence of MoO42-–goethite∼MoO42-–pyrite>MoS42-–pyrite>MoS42-–goethite. Silicate and sulfate have a negligible effect on the sorption of MoO42-and MoS42-. The preferred adsorption by iron mineral of MoS42-, as well as its behavior in the presence of competitive anions suggests that tetrathiomolybdate species may be an ultimate reservoir and may control Mo enrichment in the sediments.