Synergistic effect of pH solution and photocorrosion of ZnO particles on the photocatalytic degradation of Rhodamine B

This research aims to study the synergistic effect of pH solution and photocorrosion of ZnO particles on the photodegradation of Rhodamine B (RhB) dye. The stability of ZnO particles was investigated by zeta potential measurement. The structure, morphology and photocatalytic activity of ZnO were analysed by X-ray diffraction, scanning electron microscope and ultraviolet–visible spectrophotometer, respectively. The ZnO particles were highly crystalline with a bandgap energy of 3.23 eV. The surface charges of particles were found to be pH-sensitive, where they were more negative under alkaline condition, i.e., - 11.1, - 5.3 and - 38.2 mV at pH 3, 7 and 11, respectively. ZnO particles that dissolved in pH 3 solution produce Zn²⁺ ions, while precipitation of Zn(OH) 4 2 - was observed in pH 11 solution, resulting in morphology change of ZnO from rod shape to lamellar shape. The synergistic effect of photocorrosion and dissolution of ZnO particles in acidic solution reduced RhB dye removal efficiency from * 90% at pH 7 to ∼ 70% at pH 3. In alkaline solution, ZnO particles displayed remarkable reusability as it still recorded a 94.8% degradation efficiency after five successive cycles. (author)