Weng Liping, Van Riemsdijk Willem H, Hiemstra Tjisse
Department of Soil Quality, Wageningen University, 6700 EC Wageningen, The Netherlands.
Langmuir. 2006 Jan 3;22(1):389-97. doi: 10.1021/la051730t.
Variable-charge nanoparticles such as proteins and humics can adsorb strongly to charged macroscopic surfaces such as silica and iron oxide minerals. To model the adsorption of variable-charge particles to charged surfaces, one has to be able to calculate the adsorption free energy involved. It has been shown that the change in the free energy of variable-charge particles is related to the change in their average chemical state upon adsorption, which is commonly described using surface complexation models. In this work, expressions for the free-energy change in variable-charge particles due to changes in chemical binding are derived for three ion-binding models (i.e., the Langmuir, Langmuir-Freundlich, and NICA models) and for changes due to nonspecific binding for the Donnan model. The expressions for the adsorption free energy of the variable-charge particles to a charged surface are derived on the basis of the equality of the (electro)chemical potential of the particles in the bulk solution and adsorption phase. The expressions derived are general in the sense that they account for the competition between charge-determining ions that bind chemically to the particles, and they also apply in case of the formation of chemical bonds between particle ligands and surface sites. The derived expressions can be applied in the future to model the adsorption of variable-charge nanoparticles to charged surfaces. The results obtained for the NICA-Donnan model make it possible to apply this advanced surface complexation model to describe the adsorption of humics to minerals.
蛋白质和腐殖质等可变电荷纳米颗粒能够强烈吸附到二氧化硅和氧化铁矿物等带电荷的宏观表面上。为了模拟可变电荷颗粒在带电荷表面上的吸附过程，必须能够计算其中涉及的吸附自由能。研究表明，可变电荷颗粒的自由能变化与吸附时其平均化学状态的变化有关，这通常使用表面络合模型来描述。在这项工作中，针对三种离子结合模型（即朗缪尔模型、朗缪尔 - 弗伦德里希模型和NICA模型）以及唐南模型中非特异性结合导致的变化，推导了可变电荷颗粒因化学结合变化而产生的自由能变化表达式。基于本体溶液和吸附相中颗粒的（电）化学势相等，推导了可变电荷颗粒在带电荷表面上的吸附自由能表达式。所推导的表达式具有通用性，因为它们考虑了化学结合到颗粒上的电荷决定离子之间的竞争，并且在颗粒配体与表面位点形成化学键的情况下也适用。所推导的表达式未来可用于模拟可变电荷纳米颗粒在带电荷表面上的吸附。NICA - 唐南模型得到的结果使得应用这个先进的表面络合模型来描述腐殖质在矿物上的吸附成为可能。
