Angove MJ, Wells JD, Johnson BB
Division of Physical Sciences and Engineering, La Trobe University, Bendigo, Bendigo, Victoria, 3552, Australia
J Colloid Interface Sci. 1999 Mar 15;211(2):281-290. doi: 10.1006/jcis.1998.6010.
The adsorption of Cd(II) and Co(II) onto goethite was measured at five temperatures between 10 and 70 degrees C. For both cations the amount adsorbed at any given pH increased as the temperature was increased. Cd(II) adsorbed at a slightly lower pH at each temperature than Co(II). Adsorption isotherms at pH 7.00 for Cd(II) could be fitted closely by a simple Langmuir model, but a two-site Langmuir model was needed for Co(II). Potentiometric titrations of goethite suspensions in the presence and absence of added cation could be modeled closely by a constant-capacitance surface complexation model that assumed the adsorption reactions M2+ + SOH ⇋ SOM+ + H+ and M2+ + SOH + H2O ⇋ SOMOH + 2H+, where M represents Cd or Co. This model also fitted the experimental data from the adsorption edge and adsorption isotherm experiments. Thermodynamic parameters estimated from both Langmuir and surface complexation models showed that the adsorption of both metals was endothermic. Values obtained for the adsorption enthalpies from both modeling schemes were similar for both cations. Estimates of the adsorption entropies were model-dependent: Langmuir parameters yielded positive entropies, while some of the surface complexation parameters generated negative adsorption entropies. Copyright 1999 Academic Press.
在10至70摄氏度之间的五个温度下测量了镉（II）和钴（II）在针铁矿上的吸附情况。对于这两种阳离子，在任何给定pH值下，吸附量都随温度升高而增加。在每个温度下，镉（II）的吸附pH值略低于钴（II）。镉（II）在pH 7.00时的吸附等温线可以用简单的朗缪尔模型很好地拟合，但钴（II）需要用双位点朗缪尔模型。在添加和不添加阳离子的情况下，针铁矿悬浮液的电位滴定可以用恒电容表面络合模型很好地模拟，该模型假设吸附反应为M2+ + SOH ⇌ SOM+ + H+和M2+ + SOH + H2O ⇌ SOMOH + 2H+，其中M代表镉或钴。该模型也拟合了吸附边界和吸附等温线实验的实验数据。从朗缪尔模型和表面络合模型估计的热力学参数表明，两种金属的吸附都是吸热的。两种建模方案得到的吸附焓值对于两种阳离子来说都相似。吸附熵的估计值取决于模型：朗缪尔参数产生正熵，而一些表面络合参数产生负吸附熵。版权所有1999年学术出版社。
