Intensification of photocatalytic wastewater treatment using a novel continuous microcapillary photoreactor irradiated by visible LED lights

•Fabrication of a new flow microcapillary photoreactor irradiated by LED lights.•Photocatalytic degradation of methyl orange (MO) using novel photoreactor.•Comparing results of flow microcapillary reactor with a batch and mili photoreactor.•Study on the effect of capillary tube geometry on MO degradation efficiency.•COMSOL simulation for the study of the effect of capillary tube geometry. This paper presents a novel multi microcapillary photoreactor capped with two transparent poly (methyl methacrylate) (PMMA) plates irradiated by a 60 W visible LED SMD lamp for intensified degradation of methyl orange (MO). Copper phthalocyanine doped Bi2O3-ZnO nanophotocatalysts (CuPc-Bi2O3-ZnO) were coated on inner walls of the microcapillaries. XRD and FESEM-EDX analyses confirmed highly dispersion of copper phthalocyanine, Bi2O3 and ZnO nanoparticles with approximate size of 41 nm on the inner walls of the microcapillary tubes. DRS analysis indicated CuPc doping resulted in red shift of the light absorption region and reduction of the bandgap energy to 2.68 eV. Photocatalytic space-time yield for the fabricated intensified microphotoreactor was obtained 3.74 × 10−2 m3 wastewater/m3 reactor.day.kW, while this benchmark was 4 orders of magnitude lower, 7.5 × 10−6 m3 wastewater/m3 reactor.day.kW, for a studied batch photoreactor, and 2.17 × 10−2 m3 wastewater/m3 reactor.day.kW, for a tubular flow photoreactor, revealing positive effect of process intensification on efficiency of the photocatalytic degradation of MO. MO degradation percent in the fabricated microphotoreactor, the studied batch photoreactor, and the tubular flow photoreactor was obtained 90.83%, 58.6%, and 65.33%, respectively, as well. Study on the effect of length (30, 45, 60 mm) and diameter (400, 850 μm) of the microcapillary tubes illustrated MO conversion decreased from 94.19% (30 mm length, 850 μm diameter) to 58.01 % (45 mm length, 400 μm diameter) because according to laser analysis and COMSOL simulations with narrowing and elongating tubes, photon loss, pressure drop, and turbulence in tubes increased. [Display omitted]