Arsenic sorption onto laterite iron concretions: temperature effect.
Arsenic sorption onto laterite iron concretions: temperature effect.
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DOI：
10.1016/j.jcis.2008.02.034
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发表时间：
2008-05
影响因子：
9.9
通讯作者：
F. Partey;D. Norman;S. Ndur;R. Nartey
中科院分区：
文献类型：
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作者：
F. Partey;D. Norman;S. Ndur;R. Nartey
我们研究了砷酸盐和亚砷酸盐吸附到红土铁结核（LIC），以测试其适用于低技术处理含砷饮用水。在一系列温度、离子强度和pH下对来自加纳Prestea的粉碎的LIC进行分批实验。红土铁结核的零净电荷点由电位滴定法确定，得到平均pHpZNC约为8.64。实验结果表明，随着温度的升高，吸附剂对亚砷酸根和砷酸根的吸附量均增大。在25 ~ 60 °C温度范围内，亚砷酸盐的平衡吸附容量大于砷酸盐。一个Langmuir模型令人满意地拟合亚砷酸盐和砷酸盐的吸附等温线数据。在自然沃茨的pH范围内，亚砷酸盐和砷酸盐都被吸附。亚砷酸盐吸附增加溶液pH值的最大值在pH 7，然后随着溶液pH值的进一步增加而减少。另一方面，砷酸盐吸附，随溶液pH值的增加变化不大。增加溶液离子强度10倍的结果在吸附略有增加。离子强度实验表明，LIC对As（V）的吸附为内层吸附机制，而对As（III）的吸附为外层吸附机制。根据Langmuir等温线计算了LIC吸附亚砷酸根和砷酸根的吉布斯自由能（ΔG°），其负值与反应自发性一致。标准焓（ΔH°）的正值表明LIC吸附砷和砷酸盐的吸热性质。正熵（ΔS°）值表明LIC对溶液中砷物种的亲和力。砷吸附数据的分析表明，LIC可用于低技术天然材料砷水处理。红土铁结核有许多优点，用于这种用途超过商业材料，包括从沃茨中去除砷的能力，具有广泛的pH值范围，能够吸附两种常见的砷水溶液物种同样好，和成本less. Laterite铁结核的正吸附温度依赖性将增强吸附在热带气候，更特别是在地下水资源与地热泉有关的地区。
We investigated arsenate and arsenite sorption onto laterite iron concretions (LIC) to test its suitability for use in the low-tech treatment of arsenic-bearing drinking water. Batch experiments on crushed LIC from Prestea, Ghana were conducted at a series of temperatures, ionic strengths, and pHs. The point of zero net charge on laterite iron concretion was determined by potentiometric titrations yielding an average pHpZNCaround 8.64. Experiments show that sorption capacity for both arsenite and arsenate increase with temperature. The equilibrium sorption capacity for arsenite was larger than that for arsenate over the 25 to 60 °C temperature range. A Langmuir model satisfactorily fits the arsenite and arsenate sorption isotherm data. Both arsenite and arsenate sorbed over the pH range of natural waters. Arsenite sorption increases with increasing solution pH to a maximum at pH 7, then decreases with further increase in solution pH. Arsenate sorption, on the other hand, shows little change with increasing solution pH. Increasing solution ionic strength 10-fold results in a slight increase in sorption. Ionic strength experiments show that an inner-sphere sorption mechanism is responsible for As (V) sorption on LIC, while As (III) sorption is by an outer-sphere mechanism. Gibbs free energy (ΔG°) for arsenite and arsenate sorption onto LIC was calculated from Langmuir isotherms; the negative values agree with reaction spontaneity. The positive values of the standard enthalpy (ΔH°) show the endothermic nature of arsenite and arsenate sorption onto LIC. Positive entropy (ΔS°) values suggest the affinity of LIC for the arsenic species in solution. Analysis of the arsenic sorption data suggests that LIC can be used for low-tech natural-materials arsenic water treatment. Laterite iron concretions have a number of advantages for this use over commercial materials, including the ability to remove arsenic from waters with a wide range in pH, the ability to sorb both common arsenic aqueous species equally well, and cost less. Laterite iron concretion's positive sorption temperature dependence will enhance sorption in tropical climates, and more especially in areas where groundwater sources are related to geothermal springs.