BiFeO3–BiOI impregnation to UiO-66(Zr/Ti) as a promising candidate visible-light-driven photocatalyst for boosting urea photodecomposition in a continuous flow-loop thin-film slurry flat-plate photoreactor

Abstract The BiOI/BiFeO3/UiO-66(Zr/Ti)-MOF composite as a new ternary separable visible light photocatalyst was synthesized and well-characterized through the XRD, FE-SEM, FTIR, PL, VSM and DRS analyses. The BiOI/BiFeO3/UiO-66 photocatalytic performance for urea photo-oxidation to N2, H2O and CO2 were evaluated in a continuous flow-loop thin-film slurry flat-plate photoreactor (TFSR) equipped to blue light-emitting diodes (LEDs) illumination. Results show that the introduction of BiFeO3 perovskite and BiOI on the UiO-66(Zr/Ti) surface improves the separation and migration rate of photo-induced charges and thereby boosting the photocatalytic efficiency. Additionally, the appropriate band alignment, photo-stability and electron-hole pairs separation improvement of BiOI/BiFeO3/UiO-66(Zr/Ti)-MOF cause to enhance the urea decomposition. Moreover, five operational parameters including solution flow rate, pH, initial urea concentration, photocatalyst mass and light irradiation time were analyzed and optimized using the central composite design (CCD) and desirability function (DF), respectively. The maximum urea photocatalytic oxidation and elimination efficiency (88.53%) with the desirability value of 0.84 was achieved at the optimum conditions: 603 ​ml/min, 0.12 ​g/L, 7, 136 ​min and 60 ​ppm for flow rate, photocatalyst mass, pH, irradiation time and initial urea concentration, respectively.