海藻酸不同存在状态对纳滤膜硅酸盐结垢影响

Effect of the different existent states of alginic acid on silicate scaling of nanofiltration membrane

摘要:

为探索硅酸盐结垢过程中, 多糖类有机物海藻酸(AA)在纳滤过程中的不同存在状态, 即在溶液中与饱和硅酸盐共存、在膜面生成有机污染层, 对聚酰胺复合纳滤膜硅酸盐结垢的影响.由过滤实验研究硅酸盐结垢过程中膜通量衰减趋势; 结合扫描电子显微镜及原子力显微镜, 分析膜表面污染层结构; 通过Zeta电位研究静电排斥作用的影响; 利用原子力显微镜结合二氧化硅胶体探针分析不同结垢阶段的黏附力特点.结果表明:硅酸盐结垢污染程度为:新膜>AA与硅酸盐共存时(新膜)>AA污染膜.对比新膜的硅酸盐结垢, AA与硅酸盐共存时, 可以较弱程度地减轻硅酸盐结垢; 然而当AA污染层在膜面形成后, 硅酸盐结垢程度显著降低.上述结果表明, AA的不同存在状态对硅酸盐结垢的影响差异很大.

Abstract:

This paper aimed to investigate the effects of the different existent forms of alginic acid (AA), a polysaccharide organic matter, on the silicate scalings of polyamide composite nanofiltration membranes. Different existent forms of AA in nanofiltration process coexist with saturated silicate in the feedwater, and hence generate organic fouling layers on the membrane surface. The trend of membrane flux decline during silicate scaling was studied by filtration experiments and the structures of the fouling layers on membrane surface were analyzed by scanning electron microscopy and atomic force microscopy. The effect of electrostatic repulsion was investigated through zeta potential. Atomic force microscope combined with silica colloidal probe were used to analyze the characteristics of the adhesion forces during different scaling stages. The results showed that the degree of silicate scaling decreased in the order of virgin membrane > coexistence of AA and silicate (virgin membrane) > AA-fouled membrane. Compared with the silicate scaling of the virgin membrane, AA could weaken the silicate scaling when AA coexisted with silicate. However, when the AA fouling layer had formed on the membrane surface, the degree of silicate scaling was significantly reduced. The above results indicated that the effects on silicate scalings brought by different existent forms of AA vary greatly.