The effect of ZnO addition into TiO2 nano photocatalyst on the degradation of dye compound in aqueous solution under UV-LED irradiation

Titanium dioxide (TiO2) is extremely common semiconductor material in a wide use as a photocatalyst for solar conversion as well as in wastewater treatment and environmental air purification. TiO2 catalysts on the other hand, have a narrow band edge (3.2-3 eV for rutile and anatase phases, respectively) that hinders the photocatalytic decomposition. In this regard, the band gap energy has been lowered by attaching various metal oxides to TiO2 catalyst. Both zinc oxide (ZnO) and TiO2 are considered to be semiconductor with a wide band gap, which makes ZnO a potential candidate for combination with TiO2. As a result, the effect of adding ZnO into TiO2 photocatalyst was investigated with regard to the degradation of dye compound in aqueous solution under ultraviolet-light emission diode (UV-LED) irradiation. Powder X-ray diffraction (XRD), scanning electron microscopy [1], and other techniques were utilized in order to characterize the ZnO/TiO2 nanocomposites. Methylene blue (MB) removal was studied using various parameters, including Zn content, catalyst amount, and pH. There was an average crystallite size of 5.7–6.4 nm. When compared to pristine TiO2 nanoparticles, the photolysis of ZnO/TiO2 nanocatalyst was significantly improved. The 1 wt.% ZnO/TiO2 photocatalyst prepared by Al2O3 balls alloying (U1ZnTi) can be applied for direct irradiation under UV-LED light as well as for pollutant adsorption in a short time compared to other studies, suggesting that the U1ZnTi is potential for practical treatment application of organic pollutants as well as dye compounds when a temporary power outage occurs due to unexpected troubles in operation. Photodegradation efficiency of MB by 1 wt.% ZnO/TiO2 (1ZnTi) under UV-LED was greater than that under UV. At an optimal MB decomposition concentration of 40 mg catalyst per gram of ZnO/TiO2 composite, the catalytic activity increased with an increase in ZnO content. At a pH of 7, the most MB was removed without the use of acids or bases.