Environmental Soil Chemistry Research Group, Department of Plant and Soil Sciences, 152 Townsend Hall, University of Delaware, Newark, Delaware 19717-1303, United States.
Environ Sci Technol. 2012 Feb 21;46(4):2212-9. doi: 10.1021/es202376c. Epub 2012 Feb 6.
The kinetics of Ni sorption to two Delaware agricultural soils were studied to quantitatively assess the relative importance of Ni adsorption on soil organic matter (SOM) and the formation of Ni layered double hydroxide (Ni-LDH) precipitates using both experimental studies and kinetic modeling. Batch sorption kinetic experiments were conducted with both soils at pH 6.0, 7.0, and 7.5 from 24 h up to 1 month. Time-resolved Ni speciation in soils was determined by X-ray absorption spectroscopy (XAS) during the kinetic experiments. A kinetics model was developed to describe Ni kinetic reactions under various reaction conditions and time scales, which integrated Ni adsorption on SOM with Ni-LDH precipitation in soils. The soil Ni speciation (adsorbed phases and Ni-LDH) calculated using the kinetics model was consistent with that obtained through XAS analysis during the sorption processes. Under our experimental conditions, both modeling and XAS results demonstrated that Ni adsorption on SOM was dominant in the short term and the formation of Ni-LDH precipitates accounted for the long-term Ni sequestration in soils, and, more interestingly, that the adsorbed Ni may slowly transfer to Ni-LDH phases with longer reaction times.
研究了镍在两种特拉华州农业土壤上的吸附动力学，以定量评估土壤有机质（SOM）对镍吸附的相对重要性以及镍层状双氢氧化物（Ni-LDH）沉淀的形成，同时采用实验研究和动力学模型。在 pH 值为 6.0、7.0 和 7.5 的条件下，在 24 小时至 1 个月的时间内进行了两种土壤的批量吸附动力学实验。在动力学实验过程中，通过 X 射线吸收光谱（XAS）测定了土壤中镍的时间分辨形态。开发了一种动力学模型来描述在不同反应条件和时间尺度下的镍动力学反应，该模型将 SOM 上的镍吸附与土壤中的 Ni-LDH 沉淀结合起来。使用动力学模型计算的土壤镍形态（吸附相和 Ni-LDH）与吸附过程中通过 XAS 分析获得的结果一致。在我们的实验条件下，模型和 XAS 结果都表明，SOM 上的镍吸附在短期内占主导地位，而 Ni-LDH 沉淀的形成则导致土壤中镍的长期固定，更有趣的是，吸附的镍可能随着反应时间的延长而缓慢转移到 Ni-LDH 相中。
