Recyclable polyether–polyquaternium grafted SiO2 microsphere for efficient treatment of ASP flooding-produced water: oil adsorption characteristics and mechanism

Abstract

In this work, an interfacially active PPA@SiO₂ microsphere for ASP flooding-produced water treatment was synthesized by grafting polyether–polyquaternium (PPA) copolymer onto mesoporous hydrated silica (SiO₂). This PPA@SiO₂ microsphere integrates both demulsification and adsorption functionalities. The physicochemical properties of the SiO₂ variants were monitored via SEM, BET, XPS, contact angle and zeta potential tests. When disposing of a simulated alkali–surfactant–polymer flooding produced water that contained 500 mg L⁻¹ oil, this functional PPA@SiO₂ microsphere exhibited an oil removal efficiency of 78.0% at 1.0 g L⁻¹ dosage, which is higher than that of pristine SiO₂ (39.1%) and hydrophobic modified SiO₂ (54.2%). This remarkable oil removal efficiency was attributed to its abilities to destabilize and aggregate the emulsified oil droplets. Oil micromorphology test results indicated that PPA@SiO₂ could aggregate the fine oil droplets into oil clusters, which significantly favors the oil–water separation efficiency. An adsorption kinetics and thermodynamics study manifested that oil adsorption onto PPA@SiO₂ was an exothermic process, mainly dominated by external surface adsorption, which agreed with the BET and micromorphology study. Furthermore, the oil adsorption mechanism has been explored and confirmed according to all the experimental results. This modification protocol significantly reduced the PPA consumption and it was also found that the loaded oil onto PPA@SiO₂ could be effectively separated through a petroleum ether extraction process, so as to recycle the carrier particles. This novel PPA@SiO₂ microsphere with its high oil removal efficiency offers technical promise and huge potential for oily wastewater treatment.