壳聚糖对微细粒蛇纹石的分散/絮凝作用

Effect of Chitosan on the Dispersion/Flocculation Behavior of Fine Serpentine

通过沉降试验、吸附量测试和Zeta电位测试,研究壳聚糖对微细粒蛇纹石的分散及絮凝作用,并考察其作用机理。结果表明:蛇纹石的沉降受pH值影响较大,在pH=9时沉降较快。壳聚糖对蛇纹石的絮凝作用受pH影响较大,在pH值为3时,壳聚糖溶解在水中,通过氢键作用吸附在蛇纹石表面,吸附量较低,对微细粒蛇纹石产生分散作用,使其沉降速度降低;pH值为9时,壳聚糖从溶液中析出,沉积在蛇纹石表面,吸附量较大,从而使微细粒蛇纹石形成较大的絮团,沉降速度较快并在底部形成体积较大的沉降体。当沉降体的pH值从9变为3时,沉积在蛇纹石表面的壳聚糖重新溶解,絮凝作用消失,蛇纹石絮团分散,蛇纹石颗粒在自身重力作用下继续沉降,使沉降体体积降低,含水量也降低。

The effect of chitosan on the dispersion/flocculation behavior of fine serpentine particles was studied and the mechanism was discussed. The sedimentation results show that pH has influence on the settling behavior of serpentine particles and the sedimentation velocity is more quickly at high pH. Chitosan is a useful flocculant for the settling of serpentine but the floeculation effect of chitosan is influenced greatly by pH. When chiosan was added at pH = 9, large floecules can form and the sedimentation velocity of serpentine is more quickly. The reason is that chitosan has a critical solution pH above which it become insoluble and strongly adsorbs onto the particles surfaces. The adsorbed reagent molecules are interconnection and make the particle form large floes, which accelerate the sedimentation process. When the pH was changed from 9 to 3, the adsorbed ehitosan desorption from serpentine surface and the flocculation effect disappeared. The flocs were disorganized to the particles and the sediment consolidated to significantly higher densities under its own gravity.