膜科学与技术

负压膜蒸馏中不同类型表面活性剂的润湿机理研究

作者：谢松辰，侯春光，庞志广，余子昱，岳殿鹤，彭跃莲

单位：北京工业大学环境与生命学部，北京 100124

关键词：表面活性剂；负压膜蒸馏；膜润湿；膜污染；临界胶束浓度

出版年,卷(期):页码： 2024,44(1):8-15

摘要：

表面活性剂导致的膜润湿是膜蒸馏技术在处理实际废水面临的主要问题。为了缓解膜润湿现象，采用新型的负压膜蒸馏来评价不同类型表面活性剂盐溶液的润湿能力，并利用扫描电子显微镜、动态光散射等手段分析了表面活性剂的润湿和污染机理。首先，恒浓处理0.1 mM SDS、CTAB以及Tween-20盐溶液，当料液含阴离子表面活性剂（SDS）时，膜通量稳定，冷凝液电导率保持在3 µS/cm以内。而料液含阳离子（CTAB）和非离子表面活性剂（Tween-20）时，膜通量都衰减，甚至出现负值。通过分析污染膜表面以及溶液中表面活性剂胶束的粒径，证实CTAB和Tween-20是通过胶束污染膜表面，造成膜润湿。为了探究胶束污染和表面活性剂浓度之间的关系，分别测试表面活性剂浓度为0.1CMC、0.5CMC、1.0CMC的盐溶液，其中SDS、CTAB以及Tween-20的临界胶束浓度（CMC）分别为9.6×10-3 mol/L、9.1×10-5 mol/L和6×10-5 mol/L。当分别恒浓处理9.1×10-6 mol/LCTAB（0.1CMC）和6×10-6 mol/LTween-20（0.1CMC）盐溶液时，膜通量都能维持稳定；更高浓度时，膜润湿。但对于SDS盐溶液，膜通量都出现衰减，这种原因主要是SDS的临界胶束浓度（9.6×10-3 mol/L）比其他两种表面活性剂高两个数量级，且具更高的亲水亲油平衡值（40），使得盐溶液都具有极低的表面张力（26.4 mN/m），最终导致膜润湿。

Wetting due to surfactants was a major problem in membrane distillation when treating real wastewater. In order to alleviate membrane wetting, a negative pressure direct-contact membrane distillation (DCMD) process was used to evaluate the membrane performance when different surfactant saline solutions were the feed, and the wetting mechanism was analyzed through scanning electron microscopy, dynamic light scattering technology and other techniques. First, 0.1 mM SDS, CTAB, and Tween-20 surfactant saline solutions were respectively treated in a negative pressure DCMD. The results showed that when SDS saline solution was treated, the membrane flux was stable, and the permeate conductivity remained 3 µS/cm. For CTAB and Tween-20 saline solution, the membrane flux decayed and negative flux existed. By analyzing the foulant on the membrane surface and the micelle size in the solution, it was confirmed that cationic and nonionic surfactant micelles deposited and fouled the membrane surface, causing membrane wetting. In order to explore the relationship between membrane fouling and critical micelle concentration, saline solutions with 0.1CMC, 0.5CMC, 1.0CMC surfactant content were tested. The critical micelle concentrations (CMC) of SDS, CTAB, and Tween-20 were 9.6×10-3 mol/L, 9.1×10-5 mol/L and 6×10-5 mol/L, respectively. The results showed that the membrane flux remained stable when 9.1×10-6 mol/L CTAB (0.1CMC) and 6×10-6 mol/L Tween-20 (0.1CMC) saline solutions were treated. However, for SDS saline solution, the membrane flux decreased. The main reason was that the critical micelle concentration of SDS (9.6×10-3 mol/L) was two orders of magnitude higher than the other two surfactants, and it also had a higher hydrophilic-lipophilic balance value (40), 9.6×10-4 mol/L SDS (0.1CMC) saline solution had a lower surface tension (26.4 mN/m), leading to membrane wetting.

谢松辰（1996-），男，湖南郴州人，博士生，从事膜蒸馏中的膜结垢和润湿机理及预防策略研究，E-mail：305578024@qq.com

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