KINETICS OF CADMIUM AND COBALT DESORPTION FROM IRON AND MANGANESE OXIDES
KINETICS OF CADMIUM AND COBALT DESORPTION FROM IRON AND MANGANESE OXIDES
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DOI：
10.2136/sssaj1995.03615995005900030021x
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发表时间：
1995-05-01
影响因子：
2.9
通讯作者：
SWIFT, RS
中科院分区：
文献类型：
--
作者：
BACKES, EA;MCLAREN, RG;SWIFT, RS
土壤中的铁和锰的氧化物能够吸附大量的痕量金属离子，因此对控制土壤溶液中的痕量金属浓度，从而控制土壤中痕量金属的生物有效性具有重要意义。然而，关于微量金属从氧化物材料中解吸的速率或影响解吸速率的因素的信息相对较少。本研究的目的是研究Cd和Co从两种铁氧化物(针铁矿和铁水铁矿)和两种锰氧化物(黑锰矿和锰锰矿)中解吸的动力学。在pH值为6.0时，锰氧化物对Cd和Co的专性吸附浓度大于铁氧化物。金属也不像铁氧化物那样容易从锰中解吸，总的来说，镉比钴更容易从所有四种氧化物中解吸。将初始吸附时间从1wk增加到15wk，大大降低了吸附的Cd或Co随后从针铁矿中解吸的比例，对于锰氧化物也有类似的影响，但要小得多。Cd和Co的脱附动力学均可用两个同时发生的一级脱附反应或反应部位的连续分布来描述，这些反应中心相对于脱附一级速率常数呈对数正态分布。随着初始吸附时间的增加，两种动力学方程与实验数据的拟合参数均可解释为金属离子向脱附反应较慢的位置移动。
Oxides of Fe and Mn in soils are capable of sorbing large amounts of trace metal ions and can therefore be important in controlling trace metal concentrations in soil solution, and hence trace metal bioavailability in soils. There is, however, relatively little information on the rates of desorption of trace metals from oxide materials or on the factors affecting desorption rates. The objective of this study was to examine the kinetics of desorption of Cd and Co from two Fe oxides, goethite and ferrihydrite, and from two Mn oxides, hausmannite and cryptomelane. The concentrations of Cd and Co specifically sorbed by the oxides at pH 6.0 were greater for the Mn oxides than for the Fe oxides. The metals were also much less readily desorbed from the Mn than the Fe oxides and, in general, Cd was more readily desorbed than Co from all four oxides. Increasing the initial sorption period from 1 to 15 wk substantially decreased the proportion of sorbed Cd or Co subsequently desorbed from goethite, with a similar but much smaller effect also observed with the Mn oxides. Desorption kinetics for both Cd and Co were found to be described wed by assuming either the occurrence of two simultaneous first-order desorption reactions, or by a continuous distribution of reaction sites, distributed lognormally with respect to desorption first-order rate constant. with increasing initial sorption period, the parameters obtained from fitting either type of kinetic equation to the experimental data could be interpreted as indicating a movement of metal ions to sites with slower desorption reactions.