无机微滤膜分离草浆黑液中木素的机理

选用50nm,0.2μm和0.8μm的无机微滤膜,研究了它们对黑液中木素的截留效果.结果表明,微滤膜能够有效地分离黑液中的木素,0.2μm α-Al₂O₃和ZrO₂膜的通量高于50nm和0.8μm膜的通量,当黑液SS较低时,随着SS浓度的增加各个微滤膜的通量急剧下降,当SS较高时,微滤膜的通量和SS浓度成线性关系.2g/L聚乙二醇4000(PEG4000)溶液不会显著影响0.2μm和50nm膜的通量,但却能使0.8μm膜的通量下降60%.2g/L聚乙二醇20000(PEG20000)溶液能使各个微滤膜的通量急剧下降.按照微滤膜污染模型的计算结果和实测被稀释黑液的粒径分布,膜面形成滤饼层和木素分子形成的絮体是引起膜通量下降并改变了膜的截留性能的原因.

Mechanisms of Separating Lignin from Black Liquid by Inorganic Microfiltration

The effects of rejection to lignin from black liquid were carried out by inorganic membranes which had pore size 50 nm, 0.2 micron and 0.8 micron, respectively. The results show that MF membranes can effectively separate lignin from black liquid. The flux of 0.2 micron alpha-Al2O3 and ZrO2 membranes were larger than the flux of 50 nm and 0.8 micron membranes. The flux of each membrane drops deeply as the SS concentration increased under the conditions of low SS in black liquid. However, the flux dropping had the linear relationship with SS concentration when it was high. 2 g/L polyethylene glycol 4000 solution can not affect the fluxes of 0.2 micron and 50 nm membranes, effectively, instead of decreasing the flux of 0.8 micron membrane about 60%. 2 g/L polyethylene glycol 20,000 solution can sharply decrease the flux of each membrane. Reason that provoke flux decreasing and change the rejective ability was the cake formation on the surface membrane and the lignin aggregation.