烷基苯磺酸盐在盐溶液中沉淀/溶解的热力学模型及聚电解质的影响

A THERMODYNAMIC MODEL OF PRECIPITATION AND REDISSOLUTION OF ALKYLBENZENE SULFONATE IN BRINE AND THE EFFECTS OF THE ADDITION OF POLYELECTROLYTES

本文分别研究了几种聚电解质诸如硅酸盐和磷酸盐等对烷基苯磺酸盐在多价阳离子水溶液中溶解/沉淀/再溶解过程的影响。结果表明,这些聚电解质的加入都能不同程度地提高烷基苯磺酸盐对多价阳离子的容忍能力,提高程度取决于聚电解质的浓度及其对多价阳离子的螯合能力。在螯合能力范围内,随着聚电解质的浓度的增加烷基苯磺酸盐对多价阳离子的容忍能力增加。加入高模数的硅酸盐时磺酸盐对多价阳离子的容忍能力要比加入低模数的硅酸盐时的高。本文从磺酸盐沉淀的溶度积以及双电层理论出发,提出了烷基苯磺酸盐在多价阳离子水溶液中沉淀/溶解的热力学模型。该模型考虑了聚电解质对双电层的影响、磺酸盐-阳离子体系中“混合胶束”的形成。胶束表面电势的变化以及聚电解质对阳离子的螯合作用,并且引入了多价阳离子与胶束的缔合度。在聚电解质存在或不存在下,用该模型计算的烷基苯磺酸盐—氯化钙体系的沉淀边界与实验结果非常吻合。

The effects of polyelectrolytes such as silicates and phosphates on the dissolution/ precipitation/ redissolution of aJkylbenzene sulfonate in a multiva-lent cation aqueous solution have been studied in this paper. It turns out that, the addition of polyelectrolytes gives an increase in the sulfonate tolerance for the multivalent cation to a different degrees depending upon the concentration and the chelation of polyelectrolytes. Within the limits of chelation, as the polyelectrolytes concentration is increased, the sulfonate tole-rance of the maltivalent cation increases. The sulfonate tolerance of the cation in presence of higher polymerization degree silicate is more than that in the presence of silicate with lower degree of polymerization. A thermodynamic model is presented for the precipitation and redissolution of olkylbenzene sulfonate in multivalent cation aqueous solution based on the solubility product of the sulfonate precipitates and the theory of double electric layer. The presented model takes the effect of polyelectrolytes on the electrical double layer, the formation of 'mixed micelles' in the sulfonate-cations system, the variation of micelle surface potential and the chelation of polyelectrolytes to cations and the introduction of the degree of association of the multivalent cation with the micelles into consideration. Reasonable agreement in precipitation boundaries between the results of calculations with this model and those from actual experiment for alkylbenzene sulfonate-calcium. chloride system is obtained with or without polyelectrolytes.