Sundman Ola, Persson Per, Ohman Lars-Olof
Department of Chemistry, Umeå University, S-901 87 Umeå, Sweden.
J Colloid Interface Sci. 2008 Dec 15;328(2):248-56. doi: 10.1016/j.jcis.2008.09.027. Epub 2008 Sep 17.
Aiming for a better understanding of the interactions between water suspended cellulose fibres and metal ions, this study was focused on characterising the interactions between Ca2+, Cu2+ and two different fibre materials--a fully bleached softwood Kraft pulp, and a chemically modified fully bleached softwood Kraft fibre material. The study was conducted as a function of pH (2-7), and both in the absence and presence of an excess of Na+ ions, 0-100 mM Na(Cl). For both fibre materials, adsorption data collected in the absence of Na+ were fully explained by the unspecific Donnan ion-exchange model. However, in an excess of Na(Cl), data clearly indicated that higher amounts of divalent metal ions adsorbed, than predicted by the Donnan model. Therefore, to model these data, specific metal ion-fibre surface complexes were assumed to form, in addition to the Donnan ion-exchange. A neutral surface species involving two surface carboxylate groups and one metal ion was, for both metal ions, found to yield a good description of data at all ionic strengths. In the case of Cu2+, the existence of this complex was corroborated by Cu K-edge EXAFS data, suggesting that copper ions interacts directly with carboxyl groups present int the fibres. EXAFS data also indicate that one Cu2+ interacts with two carboxyls.
为了更好地理解水悬浮纤维素纤维与金属离子之间的相互作用，本研究着重表征Ca2+、Cu2+与两种不同纤维材料之间的相互作用，这两种材料分别是全漂针叶木硫酸盐浆和化学改性的全漂针叶木硫酸盐纤维材料。该研究是在pH值（2 - 7）范围内进行的，并且分别在不存在和存在过量Na+离子（0 - 100 mM NaCl）的情况下开展。对于这两种纤维材料，在不存在Na+时收集的吸附数据完全可以用非特异性唐南离子交换模型来解释。然而，在过量NaCl存在的情况下，数据清楚地表明，吸附的二价金属离子量比唐南模型预测的要多。因此，为了对这些数据进行建模，除了唐南离子交换外，还假定形成了特定的金属离子 - 纤维表面络合物。对于这两种金属离子，一种涉及两个表面羧基和一个金属离子的中性表面物种在所有离子强度下都能很好地描述数据。在Cu2+的情况下，Cu K边扩展X射线吸收精细结构（EXAFS）数据证实了这种络合物的存在，表明铜离子与纤维中存在的羧基直接相互作用。EXAFS数据还表明一个Cu2+与两个羧基相互作用。
