Preparation and flotation-flocculation performance evaluation of hydrophobic modified PEI for produced water treatment

Imine bond is a kind of dynamic covalent bonds, in this paper, hydrophobic chain was introduced into polyethyleneimine (PEI) through imine bond, and a series of hydrophobic modified PEI were synthesized as flocculants for flotation-flocculation treatment of produced water. The hydrophobic modified PEI had much better flotation-flocculation performance than that of PEI. When the concentration was 20 mg/L and treatment was 10 min, the best hydrophobic modified PEI had the turbidity reduction rate of more than 95 %. Especially, in a short period of time, the flocs formed by the hydrophobic modified PEI can have a great decrease in adhesiveness under pH=4 due to the dissociation of imine bonds, which is good for the produced water treatment because the viscous flocs can be effectively processed. In addition, the mechanism study showed that the hydrophobic modified PEI can adsorb on the surfaces of bubbles and oil droplets to improve the collision efficiency and adhesion efficiency between bubbles and oil droplets, thus possessing good flotation-flocculation performance. This paper provides a novel degradable flocculant for produced water treatment.