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<p>Photocatalytic demulsification of crude oil-in-water emulsions typically relies on ultraviolet light and hydroxyl radicals, yet interfacial asphaltene–resin films may be more efficiently degraded by superoxide radicals (<sup>•</sup>O<sub>2</sub>−). Herein, a Cu–Fe co-doped TiO<sub>2</sub> photocatalyst was synthesized via impregnation–calcination at 700&#xa0;°C to enable visible-light activation and selective •O<sub>2</sub>− generation. Characterization by XRD, FE-SEM, EDX, DLS, Raman, DRS, and zeta potential measurements confirmed successful dual doping, which narrowed the bandgap from 3.20 to 2.50 eV (extending absorption to ~ 495 nm) and raised the zeta potential from + 16.7 to + 26.2 mV, thereby strengthening electrostatic attraction toward negatively charged oil droplets. Under visible light, the catalyst achieved 92.1% demulsification efficiency for a 2 wt% crude oil emulsion at pH 4 and 1.0 g L<sup>−1</sup> loading within 120 min. Radical scavenger tests demonstrated that benzoquinone (<sup>•</sup>O<sub>2</sub>− scavenger) caused a 20.77 percentage-point loss in efficiency, whereas isopropanol (<sup>•</sup>OH scavenger) reduced it by only 1.45 points, unequivocally identifying •O<sub>2</sub>− as the dominant reactive species. The demulsification kinetics followed a pseudo-second-order model (R<sup>2</sup> = 0.99989), indicating that surface-mediated oxidation controls the process. These findings confirm that Cu–Fe co-doping transforms TiO<sub>2</sub> into an efficient visible-light-active demulsifier driven primarily by superoxide-mediated degradation of interfacial films, offering a promising route for treating oily wastewater using solar energy.</p> Graphical abstract <p></p>

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Visible-light-driven demulsification of crude oil-in-water emulsions by Cu–Fe Co-doped TiO2

  • 期刊论文

  • 发表日期：

    2026年7月4日

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  • Kheira Matter Essa,
  • Mehdi Parvini,
  • Mohammad Ghorbanpour

摘要

Photocatalytic demulsification of crude oil-in-water emulsions typically relies on ultraviolet light and hydroxyl radicals, yet interfacial asphaltene–resin films may be more efficiently degraded by superoxide radicals (•O2−). Herein, a Cu–Fe co-doped TiO2 photocatalyst was synthesized via impregnation–calcination at 700 °C to enable visible-light activation and selective •O2− generation. Characterization by XRD, FE-SEM, EDX, DLS, Raman, DRS, and zeta potential measurements confirmed successful dual doping, which narrowed the bandgap from 3.20 to 2.50 eV (extending absorption to ~ 495 nm) and raised the zeta potential from + 16.7 to + 26.2 mV, thereby strengthening electrostatic attraction toward negatively charged oil droplets. Under visible light, the catalyst achieved 92.1% demulsification efficiency for a 2 wt% crude oil emulsion at pH 4 and 1.0 g L−1 loading within 120 min. Radical scavenger tests demonstrated that benzoquinone (•O2− scavenger) caused a 20.77 percentage-point loss in efficiency, whereas isopropanol (•OH scavenger) reduced it by only 1.45 points, unequivocally identifying •O2− as the dominant reactive species. The demulsification kinetics followed a pseudo-second-order model (R2 = 0.99989), indicating that surface-mediated oxidation controls the process. These findings confirm that Cu–Fe co-doping transforms TiO2 into an efficient visible-light-active demulsifier driven primarily by superoxide-mediated degradation of interfacial films, offering a promising route for treating oily wastewater using solar energy.

Graphical abstract