MULTIPLE-SITE ADSORPTION OF CD, CU, ZN, AND PB ON AMORPHOUS IRON OXYHYDROXIDE
MULTIPLE-SITE ADSORPTION OF CD, CU, ZN, AND PB ON AMORPHOUS IRON OXYHYDROXIDE
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DOI：
10.1016/0021-9797(81)90063-1
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发表时间：
1981-01-01
影响因子：
9.9
通讯作者：
LECKIE, JO
中科院分区：
文献类型：
--
作者：
BENJAMIN, MM;LECKIE, JO
镉，锌，铜，铅吸附到无定形羟基氧化铁测定作为pH值，金属离子浓度和吸附剂浓度的函数。对于每种金属，存在窄的pH带，其中吸附分数从接近零增加到接近100%。当吸附剂浓度固定时，当吸附密度分别小于10 - 5.0、10 - 3.7和10 - 2.3mol吸附质/mol Fe时，吸附边界的pH值与总吸附质浓度无关。在较大的吸附密度，这三种金属和在整个范围内的吸附密度研究铅，pH值区域的吸附边缘变得更碱性的总吸附质浓度的增加。在任何情况下，吸附密度都没有达到最大极限值。结果表明，表面是由许多组的结合位点。给定金属和表面之间的结合强度可以从一个位置到另一个位置变化一个数量级或更多。在小的吸附密度下，所有类型的位点都是过量的，并且吸附可以通过朗缪尔等温线来描述。然而，在较高的吸附密度，最强的结合位点的可用性降低，导致表观吸附平衡常数的降低。这种现象发生的条件下，只有百分之几的所有表面网站被占用，是不符合现有的单网站模型。
Adsorption of Cd, Zn, Cu, and Pb onto amorphous iron oxyhydroxide was measured as a function of pH, metal ion concentration, and adsorbent concentration. For each metal, there is a narrow pH band where fractional adsorption increases from near nil to near 100%. For fixed adsorbent concentration, the pH region of the pH-adsorption edge is independent of total adsorbate concentration when adsorption density is less than 10−5.0, 10−3.7, and 10−2.3moles adsorbate per mole Fe for adsorption of Cd, Cu, and Zn, respectively. At larger adsorption densities for these three metals and over the entire range of adsorption densities studied for Pb, the pH region of the adsorption edge becomes more alkaline as total adsorbate concentration increases. In no case did adsorption density attain a maximum, limiting value. The results suggest that the surface is composed of many groups of binding sites. The strength of binding between a given metal and the surface may vary by an order of magnitude or more from one site to another. At small adsorption densities all types of sites are available in excess, and adsorption can be described by the Langmuir isotherm. However, at higher adsorption densities, availability of the strongest binding sites decreases, leading to a decrease in the apparent adsorption equilibrium constant. This phenomenon occurs under conditions where only a few percent of all surface sites are occupied, and is inconsistent with available single-site models.