Rojas Delgado R, Arandigoyen Vidaurre M, De Pauli C P, Ulibarri M A, Avena M J
Departamento de Química Inorgánica e Ingeniería Química, Campus de Rabanales, Universidad de Córdoba, Edificio C-3, 14071 Córdoba, Spain.
J Colloid Interface Sci. 2004 Dec 15;280(2):431-41. doi: 10.1016/j.jcis.2004.08.045.
A Zn-Cr layered double hydroxide (LDH) having the formula Zn(2)Cr(OH)(6)Cl(0.7)(CO(3))(0.15)2.1H(2)O was synthesized and characterized by powder X-ray diffraction, infrared spectroscopy, acid-base potentiometric titration, mass titration, electrophoretic mobility, and modeling of the electrical double layer. Adsorption of alizarin was also performed in order to show some particular features of the HDL. Net hydroxyl adsorption, which increases with increasing pH and decreasing supporting electrolyte concentration, takes place above pH 5. The electrophoretic mobility of the particles was always positive and it decreased when the pH was higher than 9. An isoelectric point of 12 could be estimated by extrapolating the data. The modified MUSIC model was used to estimate deprotonation constants of surface groups and different adsorption models were compared. Good fit of hydroxyl adsorption and electrophoresis could be achieved by considering both OH(-)/Cl(-) exchange at structural sites and proton desorption from surface hydroxyl groups. The modeling, in agreement with alizarin adsorption, indicates that most of the structural positive charge of the LDH is screened at the surface by exchanged anions and negatively charged surface groups. It also suggests that only structural charge sites initially neutralized by chloride ions are active for anion exchange. The remaining sites are blocked by carbonate and do not participate in the exchange.
合成了化学式为Zn(2)Cr(OH)(6)Cl(0.7)(CO(3))(0.15)2.1H(2)O的锌 - 铬层状双氢氧化物（LDH），并通过粉末X射线衍射、红外光谱、酸碱电位滴定、质量滴定、电泳迁移率和双电层建模对其进行了表征。还进行了茜素吸附实验以展示该层状双氢氧化物的一些特殊性质。在pH高于5时发生净羟基吸附，其随pH升高和支持电解质浓度降低而增加。颗粒的电泳迁移率始终为正，当pH高于9时降低。通过外推数据可估计出等电点为12。使用改进的MUSIC模型来估计表面基团的去质子化常数，并比较了不同的吸附模型。通过考虑结构位点处的OH(-)/Cl(-)交换以及表面羟基的质子解吸，可以很好地拟合羟基吸附和电泳。该建模结果与茜素吸附一致，表明LDH的大部分结构正电荷在表面被交换阴离子和带负电的表面基团屏蔽。这也表明只有最初被氯离子中和的结构电荷位点对阴离子交换具有活性。其余位点被碳酸盐封闭，不参与交换。
