Xu Zhi Ping, Jin Yonggang, Liu Shaomin, Hao Zheng Ping, Lu Gao Qing Max
Australian Research Council Centre of Excellence for Functional Nanomaterials, Australian Institute for Bioengineering and Nanotechnology and School of Engineering, The University of Queensland, Brisbane, QLD 4072, Australia.
J Colloid Interface Sci. 2008 Oct 15;326(2):522-9. doi: 10.1016/j.jcis.2008.06.062. Epub 2008 Jul 11.
In this research, we investigated the effect of dynamic anion adsorption/exchange on the surface charging property of Mg(2)AlClLDH and Mg(2)AlCO(3)LDH particles that show the average zeta potential of 41 and 34 mV in the as-prepared suspension, respectively. The addition of NaCl up to 3x10(-3) M in the suspension does not obviously affect the zeta potential of both LDHs, which can be attributed to the less affinity of Cl(-) to LDH. The introduction of Na(2)CO(3) severely reduces the zeta potential at the CO(3)(2-) concentration higher than 1x10(-4) M, and to the negative value in both LDH systems at ca. 2x10(-3) M, which is presumably resulted from the exchange and the re-orientation of CO(3)(2-) in a tilt/vertical style on the surface. All four organic anions (dodecyl sulfate, folate, citrate and polyacrylate) also significantly affect the zeta potential of the LDH particles. At the lower concentrations of organic anionic groups (<1x10(-4) M), the zeta potential was slightly affected, i.e. limited exchange/adsorption. However, the concentration increasing to some point suddenly decreases and reverses the zeta potential of the LDH particles, which is presumably caused by the hydrophobic interactions that bind the hydrophobic hydrocarbon chains (especially in dodecyl sulfate) into the micelle-like bilayer bunches on the LDH surface. In addition, the effect of pH in 5.5-11.0 on the LDH particle surface charging is mainly reflected through the conversion of CO(3)(2-) to HCO(3)(-)/H(2)CO(3) when pH decreases from ca. 11 to 6, with limited contribution from protonation/deprotonation and exchange/adsorption.
在本研究中，我们研究了动态阴离子吸附/交换对Mg(2)AlCl LDH和Mg(2)AlCO(3)LDH颗粒表面电荷性质的影响，这两种颗粒在制备好的悬浮液中的平均zeta电位分别为41和34 mV。在悬浮液中添加高达3×10(-3) M的NaCl对两种LDH的zeta电位没有明显影响，这可归因于Cl(-)对LDH的亲和力较低。当CO(3)(2-)浓度高于1×10(-4) M时，引入Na(2)CO(3)会严重降低zeta电位，并且在两种LDH体系中，当浓度约为2×10(-3) M时，zeta电位会变为负值，这可能是由于CO(3)(2-)在表面以倾斜/垂直方式进行交换和重新取向所致。所有四种有机阴离子（十二烷基硫酸盐、叶酸、柠檬酸盐和聚丙烯酸盐）也显著影响LDH颗粒的zeta电位。在较低浓度的有机阴离子基团（<1×10(-4) M）下，zeta电位受到轻微影响，即发生有限的交换/吸附。然而，当浓度增加到某一点时，LDH颗粒的zeta电位会突然降低并反转，这可能是由于疏水相互作用将疏水烃链（特别是在十二烷基硫酸盐中）结合到LDH表面的胶束状双层束中所致。此外，pH在5.5 - 11.0范围内对LDH颗粒表面电荷的影响主要通过当pH从约11降至6时CO(3)(2-)向HCO(3)(-)/H(2)CO(3)的转化来体现，质子化/去质子化以及交换/吸附的贡献有限。
