Ikhsan Jaslin, Johnson Bruce B, Wells John D, 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):1-5. doi: 10.1016/j.jcis.2004.01.061.
The interaction of aspartic acid with kaolinite was studied by potentiometric titrations and by adsorption measurements both at constant aspartate concentration (but varying pH) and at a constant pH of 5.5. The temperature was 25 degrees C, and the ionic medium 5 mM KNO3. Aspartic acid dissociation constants estimated from titrations agreed with those from the literature. The adsorption of aspartic acid to kaolinite was weak and varied only slightly with pH; 10-18% of 100 microM aspartic acid adsorbed to kaolinite at 100 m(2)L(-1) between pH 3 and 10. Data from the titrations and adsorption experiments were fitted closely by an extended constant-capacitance surface complexation model, in which monodentate outer-sphere complexes formed between deprotonated aspartic acid molecules and protonated sites on the variable-charge edges of the kaolinite crystals. There appeared to be no adsorption to the permanently charged crystal faces.
通过电位滴定法以及在天冬氨酸浓度恒定（但pH值可变）和pH值恒定为5.5的条件下进行吸附测量，研究了天冬氨酸与高岭土的相互作用。温度为25℃，离子介质为5 mM KNO₃。通过滴定法估算的天冬氨酸解离常数与文献中的数据一致。天冬氨酸在高岭土上的吸附较弱，且随pH值变化不大；在pH值为3至10的范围内，100 μM天冬氨酸中有10% - 18%吸附在100 m²L⁻¹的高岭土上。滴定和吸附实验的数据通过扩展的恒电容表面络合模型得到了很好的拟合，在该模型中，去质子化的天冬氨酸分子与高岭土晶体可变电荷边缘上的质子化位点之间形成了单齿外层络合物。在永久带电的晶面上似乎没有吸附现象。
