The effect of membrane surface charges on demulsification and fouling resistance during emulsion separation

• Published in: Journal of membrane science 2018-10, Vol.563, p.126-133
• Main Authors: Wu, Jindan, Wei, Wei, Li, Shihong, Zhong, Qi, Liu, Fu, Zheng, Jinhuan, Wang, Jiping
• Format: Article
• Language: English
• Subjects: Membrane fouling; Oil/water separation; Surface charge; Surfactant-stabilized emulsion; UV-initiated polymerization
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2018.05.065

The effect of membrane surface charge on demulsification and fouling resistance during emulsion separation is investigated. By grafting poly(2-dimethylaminoethyl methacrylate) (pDMAEMA) and poly(oligo(ethylene glycol) methacrylate) (pOEGMA) onto polypropylene (PP) membrane via ultraviolet (UV)-initiated polymerization, the obtained membranes PP-g-pDMAEMA and PP-g-pOEGMA present positive and negative surface charges in water, respectively. During the emulsion separation, PP-g-pOEGMA and PP-g-pDMAEMA membranes exhibit different separation efficiencies and pollutant resistant behaviors to the emulsions prepared from anionic surfactant (sodium dodecyl sulfate, SDS) and cationic surfactant (cetyltrimethylammonium bromide, CTAB). Comparing to PP-g-pOEGMA, the separation efficiency of PP-g-pDMAEMA was 15% (SDS emulsion) and 300% (CTAB emulsion) higher. But the flux recovery ratio of PP-g-pOEGMA was raised 30% (SDS emulsion) and 16% (CTAB emulsion). Hence, the membrane surface positive charges assist demulsification, but aggravate the membrane fouling. The mechanism obtained is beneficial to construct membranes with high separation efficiency and long-term durability. [Display omitted] •Hydrophilic membranes with different charges are constructed by polymer grafting.•High efficiency is achieved for surfactant-stabilized emulsion separation.•Mechanism of demulsification by membrane-surfactant interaction was studied.•Surface positive charges assist demulsification but aggravate membrane fouling.