Demulsification efficiency and mechanism of hydrophobic carbon chains modified hyperbranched polyethylenimide on oil-in-water emulsion

Abstract

A series of amphiphilic hyperbranched polyethylenimine (HPEI-Cn) with different length hydrophobic carbon chains were synthesized by amidation modification of hyperbranched polyethylenimine (HPEI), which can be used for separation of oil-in-water emulsion. The demulsification effect of HPEI-Cn under different demulsifier concentration, temperature, settling time and pH value were evaluated by bottle test method. The results indicated that the demulsification efficiency (DE) of HPEI-Cn increased with the increase of graft length of carbon chain. Encouragingly, the HPEI-C16 had the characteristics of small amount (50 mg/L), short settling time (30 min) and wide temperature adaptation range (20–60 °C). Through three-phase contact angle tests (CA), dynamic interfacial tension tests (IFT), elastic modulus analysis, Zeta potential and microscope observation, the demulsification mechanism of HPEI-Cn was systematically revealed. The excellent DE of HPEI-C16 was attributed to the high interfacial activity and appropriate length of hydrophobic groups. On the one hand, the high interfacial activity drives hyperbranched macromolecules to rapidly diffuse and adsorb to the oil-water interface. On the other hand, it contains appropriate hydrophobic carbon chains C16 to flocculate and coalesce oil droplets, thus achieving efficient demulsification.