Visible light assisted photocatalytic degradation and mineralization of Rhodamine B in aqueous solution by Ag3PO4

Abstract

The semiconductor Ag3PO4 was synthesized by precipitation using AgNO3 and Na2HPO4 as precursors with three different methods. Ag3PO4 prepared by addition of Na2HPO4 on AgNO3 gave the best photocatalytic degradation of Rhodamine B (Rh B) under both Light Emitting Diodes (LEDs) and solar light, due to the smaller size. The catalyst was characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance and photo-electrochemistry. The influences of the initial concentration of Rh B (5–20 mg L-1), catalyst dose (0.25 −1 g L-1), pH (4–11), intensity and source of light were investigated. Rh B was quasi totally degraded under the optimal conditions: 10 mg L-1 of dye, 0.5 g L-1 of Ag3PO4, Ph ∼ 7 and 10.5 mW cm-2. The degradation was controlled by UV–Vis spectroscopy and high-performance liquid chromatography (HPLC). The kinetic indicated that the Langmuir-Hinshelwood (L-H) model was well fitted to the experimental data. Additionally, the mineralization was investigated by the Chemical Oxygen Demand (COD) and Total Organic Carbon (TOC). Rh B was completely mineralized after 75 min of illumination and the degradation obeys to first order with a half-life 14.44 min. A photocatalytic degradation mechanism was proposed to explain the high activity under visible light. Moreover, the stability of the catalyst was checked.