Positively Charged Fibrous Membrane for Efficient Surfactant Stabilized Emulsion Separation via Coalescence

Abstract Surfactants improve the emulsion stability and change the intrinsic wettability of the membrane surface, devastating the separation effects for oil/water emulsion. Poly (2-(methacryloyloxy) ethyl trimethylammonium chloride) (PDMC) particles was synthesized and deposited on the glass fiber membrane (GM) to fabricate positively charged membranes (GM/PDMCs). The chemical composition, structure, pore size distribution and underwater-oil wetting behavior of the membranes were investigated. The characterizations verified that PDMC particles were successfully located on the GM surface turning the smooth fiber surface into roughness, and narrowed pore size of the membrane. With the increase of PDMC deposition, the oil contact angle underwater first increased and then decreased. Afterwards, the optimal condition of separating surfactant-free emulsion for GM/PDMC membrane was established. The oil removal efficiency was beyond 98% with pressure drop below 0.45 MPa under water flux of 5928 L∙m-2∙h-1 for 8-cycle test. Furthermore, the wetting behaviors of GM and GM/PDMCs in three surfactants containing solutions were explored and inferred the real state of oil droplet contacting with the membranes which explained the separation performance. It turned out that GM/PDMC membranes achieved excellent long-term separation efficiency of 97.1% for cationic surfactant containing emulsion and effectively demulsified anionic surfactant stabilized emulsion with 97.5% separation effect. However, neutral surfactants were easily adsorbed on the surface of the membranes affecting the separation efficiency. Finally, different types of oil emulsions were examined with good performance indicating that the GM/PDMC membrane has broad application prospects.