凹凸棒土膜的制备及其离子截留性能

Preparation of an attapulgite membrane and its rejection performance for various ions

采用固态粒子烧结法在陶土-粉煤灰基体表面制备了纳米级凹凸棒土膜,改善了基体表面形貌,收窄了基体的孔径分布区间。考察了凹凸棒土膜对不同类型离子模拟废水的处理效果,并研究了pH值对凹凸棒土膜截留性能的影响。结果表明:涂覆在陶土-粉煤灰基体上的凹凸棒土膜对Ca2+、PO34-和Cl-等离子均具有一定的截留效果,特别是对高价阴离子的截留效果优异;不同类型离子模拟废水均在特定pH值时出现最低截留率,证明了凹凸棒土膜的截留机理为道南排斥和介电效应,此特定pH值即为等电位点,且等电位点随溶液的不同而发生变化。

A nanoscale attapulgite membrane has been prepared on the surface of a clay-fly ash substrate by a solid state sintering process, which improved the surface morphology and narrowed the pore size distribution of the sub- strate. The performance of the attapulgite membrane was tested with various samples of simulated wastewater and the relationship between pH and retention rate was investigated. The results showed that the membrane had a rea- sonable retention for Ca2＋ , PO34- and C1- , with a particularly good performance for highly charged anions. Each simulated wastewater sample demonstrated a minimum retention at a specific pH value, showing that the rejection mechanism for the attapulgite membrane involved both Donnan and dielectric effects. The pH value for miniumum retention corresponds to the isoelectric point and it varied with liquid composition.