Magnetically recoverable functionalized Fe3O4/Cu-MOF reduces divalent ions in oilfield wastewater and synergizes with crude oil binary drive for enhanced recovery

Given the ongoing global demand for oil, polymer–surfactant binary flooding technology plays a key role in enhancing oil recovery. However, in high-temperature, high-salinity, and high-calcium/magnesium reservoirs, traditional binary flooding systems face limitations due to thermal degradation, salt sensitivity, and formation adsorption, significantly reducing their effectiveness. In this study, a novel magnetic nanocomposite, BS@Fe 3 O 4 /MOF, was synthesized using Cu-based metal–organic framework (Cu-MOF)-doped Fe 3 O 4 magnetic nanoparticles and functionalized with dodecyldimethyl betaine (BS-12). The nanocomposite effectively removed Ca 2+ and Mg 2+ ions. Emulsification tests optimized the binary surfactant/polymer (SP) flooding system with octylphenol ethoxylate (OP-10) and xanthan gum (XG) and verified the feasibility of constructing the SP-BS@Fe 3 O 4 /MOF system. The system showed strong tolerance to high temperatures, salinity, and varied pH environments, with a substantial increase in viscosity and ultra-low interfacial tension in crude oil. Adsorption loss was 14%, with separation rates of 8.28% for the nanocomposite and 17.86% for XG. Oil recovery tests showed an 8.22% improvement, and magnetic recovery added another 3.75%. Overall, BS@Fe 3 O 4 /MOF enhances binary flooding, providing a strategic solution for field application challenges.