甲壳素-壳聚糖对皂土悬浮液的絮凝

研究了三种摩尔质量大体相同而脱乙酰度分别为93%、78%和62%的甲壳素-壳聚糖在pH=3～6范围内对皂土悬浮液的絮凝性质, 并与非离子型絮凝剂聚丙烯酰胺作了比较, 证明含自由氨基的甲壳素-壳聚糖在酸性溶液中形成阳离子聚电解质后. 对带负电的皂土悬浮颗粒有很好的絮凝能力. 通过对上述三种聚合物的絮凝能力、在皂土颗粒表面的吸附量等测定, 认为絮凝中桥连机制起了主导作用, 但聚合物所带正电荷则有利于被皂土颗粒所吸附, 电中和还降低了颗粒间的静电排斥, 这都对桥连絮凝起了促进作用. 聚丙烯酰胺分子在水中不带电, 故当介质pH升高使皂土颗粒双电层变厚时, 絮凝能力迅速下降.

FLOCCULATION OF BENTONITE SUSPENSIONS BY DEACETYLCHITINS

Deacetylchitins of similar molar mass (6.1, 6.9, 7.2×10~5 g·mol~(-1)) but different aminecontent(93%, 78%, 62%) were tested as flocculants for bentonite suspensions. Flocculant performance was assessed by determining the turbidity change of the suspensions with time, the extent of the deacetylchitin adsorption and the electrokinetic potential of the treated particles. The suspension concentration was kept constant at 2 g (bentonite).dm~(-3) in 10~(-3) mol·dm~(-3) NaCl solution; pH was varied from 3 to 6. It was found that bridging was the predominant mechanism of the flocculation, but neutralization of the particle charge by the adsorption of macroelectrolytes did play a contributory role in the destabilization of the suspensions.Similar experiments were carried out using a nonionic acrylamide of high molar mass (1～3×10~6 g·mol~(-1). The efficacy of flocculation by polymer bridging did not counteract the increasing self-repulsion of the bentonite particles with increasing pH which produced poor floc formation.