Ikhsan Jaslin, Wells John D, Johnson Bruce B, Angove Michael J
Colloid and Environmental Chemistry Laboratory, La Trobe University, P.O. Box 199, Bendigo, Victoria 3552, Australia.
J Colloid Interface Sci. 2004 May 1;273(1):6-13. doi: 10.1016/j.jcis.2004.01.060.
The effect of aspartic acid on the adsorption of Pb(II), Cu(II), Zn(II), Co(II), and Mn(II) on kaolinite at 25 degrees C in the presence of 5 mM KNO3 was investigated by means of potentiometric titrations and adsorption measurements over a range of pH and concentration. Data were modeled by extended constant capacitance models. Aspartic acid slightly enhanced the adsorption of Pb(II), Zn(II), and Co(II) at low pH, but inhibited the adsorption of all the metal ions at higher pH. Adsorption of Cu(II) and Co(II) was inhibited strongly. Because aspartic acid is adsorbed only weakly by kaolinite, inhibition of metal ion adsorption depends on the ability of aspartic acid to form complexes with the various metal ions together with the adsorption characteristics of these complexes. In particular suppression of adsorption at high pH arises from competition between surface sites and dissolved aspartate ions for the available metal ions. Cu(II) and Co(II) form complexes with aspartic acid more strongly than the other metals. As these complexes do not adsorb, Cu(II) and Co(II) suffer greater suppression from aspartic acid than the other metals. There was no evidence of adsorption of aspartic acid complexes to the permanently charged kaolinite faces.
通过电位滴定法和在一系列pH值和浓度范围内的吸附测量，研究了在25℃、5 mM KNO₃存在下，天冬氨酸对高岭石吸附Pb(II)、Cu(II)、Zn(II)、Co(II)和Mn(II)的影响。数据采用扩展恒电容模型进行模拟。在低pH值下，天冬氨酸略微增强了Pb(II)、Zn(II)和Co(II)的吸附，但在较高pH值下抑制了所有金属离子的吸附。Cu(II)和Co(II)的吸附受到强烈抑制。由于天冬氨酸仅被高岭石微弱吸附，金属离子吸附的抑制取决于天冬氨酸与各种金属离子形成络合物的能力以及这些络合物的吸附特性。特别是在高pH值下吸附的抑制是由于表面位点和溶解的天冬氨酸离子对可用金属离子的竞争。Cu(II)和Co(II)与天冬氨酸形成络合物的能力比其他金属更强。由于这些络合物不吸附，Cu(II)和Co(II)比其他金属受到天冬氨酸的抑制更大。没有证据表明天冬氨酸络合物吸附到永久带电的高岭石表面。
