Modification of TiO2 to enhance photocatalytic degradation of organics in aqueous solutions

Heterogeneous photocatalysis, an advanced oxidation process (AOP), has shown to be efficient for the degradation of refractory organics in aqueous solutions into simple compounds. Two issues that arise with the use of unmodified TiO2 are the fast recombination of electron/hole pairs and the lower effectiveness in the presence of visible irradiation. This study aims to develop a photocatalyst by doping transition metals, especially noble metals such as Ag, onto the original TiO2. The combination of photocatalysts is a method to improve the photocatalytic activity for the degradation of organic compounds in wastewater. In this study, first Ag-doped TiO2 is prepared and then, a composite of Fe2O3/TiO2 is synthesized in different mass ratios. A series of experiments is conducted for the treatment of two azo dyes, Congo Red (CR) and Methyl Orange (MO), by photocatalysis under the UV-vis irradiation. The degradation of organic materials is measured in terms of total organic carbon (TOC). Scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS) along with the Brunauer, Emmet, and Teller (BET) method have been utilized to illustrate the characteristics of the prepared powder photocatalysts. X-ray diffraction (XRD) was used to identify crystallinity and phase conversion of the photocatalyst. Results show that silver doped TiO2 increases the degradation of MO (12.2%) and CR (14.5%) compared to that of the bare TiO2. The degradation efficiency of MO and CR increases by applying composite photocatalyst of Fe2O3/TiO2 in the range of 28.9 and 25.1%, respectively, compared to that of the bare TiO2.