Photocatalytic activity of ZnO-PbS nanoscale toward Allura Red AC in an aqueous solution: Characterization and mechanism study

Abstract

A binary ZnO-PbS catalyst in nanoscale was prepared and characterized via some identification techniques of XRD, DRS, BET, photoluminescence, and SEM-EDX techniques. The average size for ZnO, PbS, and ZnO-PbS was about 17.4, 19.5, and 22.5 nm by the Scherrer model, and 22.7, 23.5, and 18.5 nm by the Williamson-Hall model, respectively. ZnO and the coupled catalyst showed absorption edge wavelengths of 379 nm and 537 nm corresponding to Eg of 3.27 eV and 2.31 eV. The pHpzc of as-synthesized PbS, ZnO, and ZnO-PbS were obtained to be 6.0, 7.2, and 6.7, respectively. Synergistic photocatalytic activity of the binary sample, concerning the semiconductors alone, was achieved toward Allura Red AC (AR) as a dye pollutant model that varied with the change in the amount of the semiconductors in the coupled sample. The best activity was reached when moles of ZnO in the coupled system were four times greater than the other. Optimal conditions for RF photodegradation were: dose: 0.9 g/L, ZnO: PbS mole ratio: 4:1, CAR: 2 ppm, pH 5.