Nyström Roger, Backfolk Kaj, Rosenholm Jarl B, Nurmi Kari
Department of Physical Chemistry, Abo Akademi University, FIN-20500 Abo, Finland.
J Colloid Interface Sci. 2003 Jun 1;262(1):48-54. doi: 10.1016/S0021-9797(03)00211-X.
The flocculation performance of cationic starches on calcite pretreated with anionic sodium polyacrylate (NaPA) was investigated by measuring the mean particle size and the dynamic mobility of the calcite dispersions. Cationic starches of different molecular weight and degree of substitution were used. By varying the amount of anionic sodium polyacrylate, which has a strong affinity to the calcium carbonate surface, one is able to anionically modify the particles and reverse the charge character of the originally cationic calcium carbonate. By such modification of the charge character of the calcium carbonate dispersion, it is possible to approach the mechanisms of flocculation caused by cationic macromolecules like starch. The importance of different mechanisms of flocculation, such as bridging, charge neutralization, and flocculation induced by polyelectrolyte complexes (PEC), was further investigated in this work. It was found that when the NaPA is completely absorbed at the calcite surfaces the mechanism of the flocculation induced by the starch is mainly bridging flocculation. Excess NaPA in the calcium carbonate dispersion will result in polyelectrolyte complexes formed between the non-absorbed NaPA and the oppositely charged starch polymers. These complexes will in most cases strongly enhance the flocculation due to mainly charge neutralization. Depending on the ratio of non-absorbed NaPA and the starch in the aqueous phase, the calcite dispersion is either re-stabilized or more strongly flocculated due to the formed polyelectrolyte complexes. Both the mobility and the particle size measurements support the mechanisms described. It was further demonstrated that the molecular weight and degree of substitution of the starches might be adjusted to control the flocculation behavior.
通过测量方解石分散体的平均粒径和动态迁移率，研究了阳离子淀粉对方解石（用阴离子聚丙烯酸钠（NaPA）预处理）的絮凝性能。使用了不同分子量和取代度的阳离子淀粉。通过改变对碳酸钙表面具有强亲和力的阴离子聚丙烯酸钠的用量，可以对颗粒进行阴离子改性，并使原本带阳离子的碳酸钙的电荷特性发生反转。通过这种对碳酸钙分散体电荷特性的改性，有可能深入了解由淀粉等阳离子大分子引起的絮凝机制。在这项工作中，进一步研究了不同絮凝机制的重要性，如架桥、电荷中和以及聚电解质络合物（PEC）诱导的絮凝。结果发现，当NaPA完全吸附在方解石表面时，淀粉诱导的絮凝机制主要是架桥絮凝。碳酸钙分散体中过量的NaPA会导致未吸附的NaPA与带相反电荷的淀粉聚合物之间形成聚电解质络合物。在大多数情况下，这些络合物将主要由于电荷中和而强烈增强絮凝作用。根据水相中未吸附的NaPA与淀粉的比例，方解石分散体要么重新稳定，要么由于形成的聚电解质络合物而更强烈地絮凝。迁移率和粒径测量结果均支持所描述的机制。进一步证明，可以调节淀粉的分子量和取代度来控制絮凝行为。
