进水钙、铝离子共存对反渗透膜污染的影响效应分析

基于某生物制药企业膜生物反应器处理出水配置了不同Ca/Al配比的料液，以考察其对反渗透膜污染的结构、形貌、组成与特征的影响效应。结果表明：进水中共存的钙、铝成分结合有机物在膜面上形成了复合污染层，Ca/Al配比的变化导致差异显著的膜污染特性。在低铝含量、高Ca/Al比条件下，进水中Al-O-H形态与膜面有机官能团之间强势极性作用力优先结合，同时与进水中疏水性有机组分的凝聚作用共同沉积于膜面，对膜污染的形成具有远大于Ca组分的作用。根据扩展杨氏方程计算得到系统总表面张力分别为：低钙低铝，53.0 mJ/m2；低钙高铝，69.5 mJ/m2；高钙高铝，70.4 mJ/m2，表明进水中铝含量变化主要影响进水溶液与膜面材料之间的极性作用力，钙含量变化几乎没有相应影响。膜清洗结果表明进水中钙铝成分引起的膜污染在空间结构上是分层的，铝通过与膜面分子间的极性力作用紧密结合在膜污染的底层，形成难以清洗的不可逆污染；Ca则主要存在于污染的滤饼层，极易通过化学清洗恢复。因此，精准控制前段混凝预处理阶段Al盐投加量对防止膜污染具有重要意义。

Effect of the influent Calcium and Aluminum ions on reverse osmosis membrane fouling

The effects of structure, morphology, composition and characteristics of reverse osmosis membrane fouling were investigated by an effluent with different Ca/Al ratios of membrane bioreactor in a biopharmaceutical enterprise.The results demonstrated that calcium and aluminum combined with organic matter formed a composite fouling layer on the membrane surface,and the change of Ca/Al ratio resulted in significantly different membrane fouling characteristics.The form of Al-O-H in the solution was preferentially combined with the organic functional groups by polar force ,and it was co-deposited with the coagulation of the hydrophobic organic components under the condition of low aluminum content and high Ca/Al ratio.It had a far greater effect on the formation of membrane fouling than the Ca component. According to the extended Young''s equation,the total surface tension of the system was calculated as:53.0 mJ/m2 (low Ca low Al),69.5 mJ/m2 (low Ca high Al),70.4 mJ/m2 (high Ca high Al).It showed that the change of aluminum content mainly affected the polar force between the solution and the membrane material, and the change of the calcium content had almost no corresponding effect.The results of membrane cleaning indicated that the membrane fouling caused by calcium-aluminum components were stratified in spatial structure,and aluminum was tightly bound to the bottom layer of membrane fouling by the polar force between the molecules on the membrane surface, forming irreversible fouling.Calcium was mainly exist in the contaminated filter cake layer which can be easily recovered by chemical cleaning.Therefore,it is of great significance to accurately control the dosage of aluminum salt in the coagulation pretreatment stage to prevent membrane fouling.