Sonochemical-assisted synthesis of CuO/Cu2O/Cu nanoparticles as efficient photocatalyst for simultaneous degradation of pollutant dyes in rotating packed bed reactor: LED illumination and central composite design optimization

•Ultrasonication is an easy, simple and green technique for the fabrication of CuO/CuO2/Cu nanoparticles.•Photo-degradation of methylene blue and safranin O in continuous flow rotating packed bed reactor.•Cu-NPs as co-cocatalyst incorporation to Cu2O/CuO heterojunction for greatly accelerate electron transfer.•Sonochemical preparation of H and O radicals for Cu2+ reduction. CuO/CuO2/Cu nanoparticles were prepared by sonochemical combined thermal synthesis method and used as new photocatalyst for simultaneous photocatalytic degradation of safranin O (SO) and methylene blue (MB) dyes in rotating packed bed reactor equipped to blue light emitting diode (LED). The physicochemical properties of the synthesized CuO/Cu2O/Cu nanoparticles were investigated by XRD, SEM and DRS analysis. The band-gap of the prepared CuO/Cu2O/Cu-NPs was estimated to be about 1.42eV which is appropriate for photodegradation process under blue light irradiation. In rotating packed bed reactors, two key parameters are very important, one high centrifugal field and other porous media, which intensify mass transfer operation leads to photodegradation improvement. The maximum photodegradation efficiency was obtained at pH of 6 and subsequently the effects of CuO/Cu2O/Cu-NPs dosage, rotational speed, initial dyes concentration, flow rate and reaction time were studied by central composite design (CCD) and optimized values were found to be 0.3g/L, 900rpm, 10mg/L of both dyes, 0.3L/min and 90min, respectively. Finally, results showed that synergistic effects induced by forming Cu2O/CuO heterojunction containing Cu-NPs co-cocatalyst greatly accelerate electron transfer and effectively retard the reduction of CuO by photo-generated electrons.