Ultrasonic-assisted sol–gel synthesis of samarium, cerium co-doped TiO2 nanoparticles with enhanced sonocatalytic efficiency

• Synthesis of samarium, cerium co-doped TiO2 by ultrasonic-assisted sol–gel method.
• Study the sonocatalytic removal of Methyl Orange as a model organic pollutant.
• Higher sonocatalytic activity of Sm, Ce co-doped TiO2 than mono-doped and pure.
• Optimization of the effect of dopants contents on sonocatalytic activity.
• Optimization of the effect of operational variables on sonocatalytic activity.

In this work, pure TiO2 and samarium, cerium mono-doped and co-doped TiO2 catalysts were synthesized by an ultrasonic-assisted sol–gel method and their sonocatalytic efficiency studied toward removal of Methyl Orange as a model organic pollutant from the textile industry. The relationship of structure and sonocatalytic performance of catalysts was established by using various techniques, such as XRD, TEM, SEM, EDX, DRS, and PL. A comparison on the removal efficiency of sonolysis alone and sonocatalytic processes was performed. The results showed that the samarium, cerium co-doped TiO2 catalyst with narrower band gap energy and smaller particle size leads to a rapid removal of pollutant. It was believed that Sm3+ and Ce4+ ions can serve as superficial trapping for electrons at conduction band of TiO2 and prolonged the lifetime of electron–hole pairs. Finally, the effect of synthesis and operational variables on the sonocatalytic activity of co-doped TiO2 catalyst was studied and optimized using response surface methodology as a statistical technique. The results showed that the maximum removal efficiency (96.33%) was achieved at the optimum conditions: samarium content of 0.6 wt%, cerium content of 0.82 wt%, initial pollutant concentration of 4.31 mg L−1, catalyst dosage of 0.84 mg L−1, ultrasonic irradiation power of 700 W, and irradiation time of 50 min.

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