Acid/Alkali-Resistant Modified MOF-74 Grafted with Polyether Demulsifier for Oil-in-Water Emulsions Under Ambient Conditions

The effective and rapid separation of oil-water emulsions at room temperature, particularly under harsh environmental conditions like acid-base fluctuations, high salinity, and the coexistence of surfactants, remains a significant challenge in oily wastewater treatment. To address this, a novel amphiphilic demulsifier, MOF-74@SiO₂-GPTMS grafted ANP (MSG-ANP), was synthesized by first modifying MOF-74@SiO₂ (MS) with γ-glycidoxypropyltrimethoxysilane (GPTMS) to create epoxy-functionalized MSG particles, followed by grafting the non-ionic polyether C₁₂-C₁₄ aliphatic polyethylene oxide polyoxypropylene (ANP) onto MSG. Bottle tests demonstrated that MSG-ANP achieved a high demulsification efficiency of 93% within 15 min for oil-in-water emulsions at room temperature. It exhibited excellent environmental tolerance, maintaining efficiencies of 89% at pH 3.0, 82% at pH 11.0, and 95% under high salinity (50,000 mg/L, pH 6.8). Furthermore, MSG-ANP effectively treated surfactant-stabilized emulsions, exceeding 96% efficiency against both cetyltrimethylammonium bromide and sodium dodecyl sulfate after 30 min, outperforming commercial demulsifiers SP-169 and AR-331 by factors of 1.2 and 1.6, respectively. This superior performance stems from synergistic hydrogen bonding (via hydroxyl, ether, ester, Fe-O, and Si-O groups) destabilizing the interfacial film and electrostatic neutralization of coalescing charged droplets. Consequently, MSG-ANP presents a promising solution for rapid, room-temperature demulsification across a wide pH range and under high-salinity conditions.