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Biofouling is a major problem in water membrane processes, especially in seawater reverse osmosis plants. Inactivation of Vibrio fischeri (a well-known marine bacterium forming biofilm) through photocatalysis via visible light was investigated in this work using active Fe 2 O 3 -TiO 2 nanoparticles. Five Fe 2 O 3 -TiO 2 photocatalysts with different weight percentage of Fe 2 O 3 (0–5 wt%) were synthesized using an ultrasonic-assisted co-precipitation method. The photocatalysts were characterized by powder X-ray diffraction (XRD), BET surface area, transmission electron Æ (TEM) plus selected area electron diffraction (SAED) patterns, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and diffuse-reflectance spectroscopy (DRS). Based on the design of experiments, the synthesized photocatalysts were tested for inactivation of V. fischeri under visible light irradiation at different temperatures (25–35 °C) and different photocatalyst dosage (0.1–2 g/L). The photocatalytic microbial inactivation experiments were performed in artificial seawater appropriate for growth of the marine bacterium. The results revealed that the highest inactivation efficiency of V. fischeri was achieved when 1 g/L of 2.5 wt% Fe 2 O 3 -TiO 2 were used, at 35 °C. Photocatalytic inactivation of microorganisms using visible light-driven Fe 2 O 3 -TiO 2 photocatalysts, could introduce an innovative green method in pretreatment units of reverse osmosis plants to control the membrane biofouling. [ABSTRACT FROM AUTHOR]

• Hybrid process of photocatalytic oxidation together with surfactants was applied. • Effect of three different surfactants was investigated on process efficiency. • Experiments were performed in nutrient rich media and in presence of visible light. • Photocatalytic inactivation rate of V. fischeri followed first order kinetics. The activity of seawater microorganisms is of great concern around the world because of high biofilm formation potential. Visible-light photocatalysis is considered to be one of essential methods for microbial control which could effectively address this challenge. Herein, the effect of three different chemical surfactants, i.e., anionic, cationic, and non-ionic, on the photocatalytic toxicity of Fe 2 O 3 -TiO 2 nanoparticles towards Vibrio fischeri , a marine bacterium, was investigated under 55 w/m2 of visible light irradiation. Although all types of surfactants alone showed slight cytotoxic effects on bacteria, reduction of photocatalytic disinfection efficiency was observed in the presence of different surfactant concentrationsdue to the competitive degradation of bacteria and surfactants competing for oxidative power. The reduction ranges of the photocatalytic toxicity of the Fe 2 O 3 -TiO 2 toward bacterial cells depended on the kind and concentration of the surfactants in the solution. The most significant reduction of photocatalytic toxicity was caused by the addition of non-ionic surfactants, Triton X-100. Moreover, independent of surfactant presence in reaction media, the photocatalytic inactivation rate of V. fischeri followed first order kinetics. [ABSTRACT FROM AUTHOR]

Many industries located in coastal areas use a large amount of seawater. Algal biofouling can be a major problem that hinders the efficiency of these industrial facilities. In most cases, seawater requires algal removal pre-treatment to avoid or mitigate biofilm formation. To remediate green microalgae, Fe 2 O 3 –TiO 2 nanoparticles with 2.5% w/w Fe 2 O 3 were applied as a visible light driven photocatalyst. The anti-algal activity of the photocatalytic pre-treatment using green microalgae, Chlorella vulgaris was tested. The experiments were carried out in freshwater, artificial seawater, and real seawater. Effect of photocatalyst dosage, visible light intensity, and water salinity on the removal of microalgae was investigated. The highest inactivation efficiency of Chlorella vulgaris was achieved under 55 W/m2 visible light irradiation when 0.25 g/L of Fe 2 O 3 –TiO 2 photocatalyst was used. The photocatalytic removal kinetics of Chlorella vulgaris followed the pseudo first order Langmuir-Hinshelwood model. The results revealed that the efficiency of photocatalytic removal of algae decreased with increasing of seawater salinity. The anti-algal activity of Fe 2 O 3 –TiO 2 nanoparticles was attributed to the generation of reactive oxygen species (ROS) through the photocatalytic process. H+ radical was shown to be the most important ROS that nanoparticles produced in the aqueous media. Using Fe 2 O 3 –TiO 2 nanoparticles in photocatalytic pre-treatment could be an efficient environmental-friendly method for micro-algal remediation in seawater under visible light. • Anti-algal activity of Fe 2 O 3 –TiO 2 NPs was investigated in fresh and saline water. • TiO 2 –Fe 2 O 3 NPs achieved a high removal rate of algal cells (99.8%) within 24 h. • Anti-algal activity of NPs was 31.6% higher in fresh water than high-salinity water. • Non-toxic alternative for prevention of algal fouling was presented. • H+ radical was dominant ROS species produced during photocatalysis. [ABSTRACT FROM AUTHOR]