离子强度对粘土和改性粘土絮凝去除水华铜绿微囊藻的影响

研究了水体的离子强度对粘土和壳聚糖改性粘土絮凝去除铜绿微囊藻的影响 .离子强度的增加有利于粘土对藻类的絮凝去除 .与一般粘土除藻相反 ,壳聚糖改性粘土却在离子强度低的条件下具有更好的除藻效果 ,是适合在湖泊 ,水库和江河等淡水 (低含盐量 )水体中应用的应急除藻技术 .当离子强度从 0.17mol/L降到 0mol/L时 ,海泡石除藻率从 90 %以上降为 70 %以下(投加量700mg/L) ,而壳聚糖改性海泡石的除藻率却从 70%左右升至 95% (投加量仅为 11mg/L) .用粘度法研究了壳聚糖改性海泡石的絮凝机理 ,发现相对低的离子强度更有利于壳聚糖分子链上阳电荷的相互排斥作用 ,有利于壳聚糖分子链的舒展 ,从而可以充分发挥架桥网捕作用 ,利于絮凝除藻 .

Effects of Ionic Strength on the Flocculation and Removal of Cyanobacterial Cells of Microcystis aeruginosa by Clays

The effect of ionic strength on the flocculation and removal of Microcystis aeruginosa by clays and chitosan-modified clays were studied. High ionic strength was beneficial to the removal of algae cells by clays due to the reduction of the thickness of electrical double layer that enhanced the collision probability of the granules. In contrast to normal clays, chitosan-modified clays showed a higher removal efficiency of Microcystis aeruginosa cells under low ionic strength. The removal efficiency was reduced from more than 90% to 70% by sepiolite, but promoted from 70% to 95% by modified sepiolite when the ionic strength decreased from 0.17mol/L to 0 mol/L. This is because the repulsion of positive charged groups in chitosan molecule chain were shielded by large number of ions at higher ionic strength that reduce the extensibility of the chitosan molecule, leading to the reduction of bridging and netting between particles. Chitosan-modified clays were therefore suitable for removal cyanobacterial cells in fresh waters such as lakes, reservoirs and rivers.