ENHANCEMENT OF VISIBLE-LIGHT-DRIVEN PHOTOCATALYTIC ACTIVITY OF TiO2/WO3 NANOCOMPOSITE FOR ORGANIC REMOVAL

Abstract

Water is importance to all living things. However, freshwater resources are limited and facing an increasing pressure from drought, flood, pollution, population growth, and competition from many uses (e.g., ecosystem protection, agriculture, energy production, and recreation). In the meanwhile, decrease in the quality of water resource from pollution and contamination (such as heavy metals, dyes, pesticides) by various types of discharge is a serious environmental problem in all over the world.

In order to overcome the future water scarcity, wastewater treatment is an effective solution to improve the wastewater quality and reuse it in any proposes. In many wastewater treatment methods, advanced oxidation processes (AOPs) have received increasing attention in research and development of wastewater treatment technologies in last decades. Among of the AOPs, photocatalysis process is considered as the greenest technology, due to high stability of photocatalyst and no toxic secondary pollutants formation.

Moreover, photocatalysis process is effective organic degradation, which is a common pollutant in the wastewater. Various photocatalysts can be used, however TiO2 has been known as the most widely used photocatalyst. Due to its relatively wide band gap (~3.2eV), TiO2 can be activated under strong light energy such as UV. This becomes an important operating cost of using photocatalysis process of TiO2 for wastewater treatment and reuse. WO3 is another photocatalyst, having a low band gap value of 2.4–2.8 eV, and widely used for base material for biomarker detection and gas sensor. Therefore, a hybrid of TiO2 and WO3 as TiO2/WO3 composite is possible to enhance the photocatalytic activity as well as the properties of each TiO2 and WO3 photocatalyst.

In this work, TiO2/WO3 nanocomposite was synthesized by using hydrothermal method at various ratios of WO3 from 0.01% to 0.3%. The physico-chemical properties of this nanocomposite were investigated by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Brunauer–Emmett–Teller (BET) analytical instruments. Furthermore, the adsorption and photocatalytic degradation of methylene blue (MB) as a model organic pollutant were investigated, and then compared to pure TiO2 and pure WO3. The results showed that the increasing ratios of WO3 can cause an enhancement of adsorption ability of TiO2/WO3 nanocomposite, and consequently increase MB photocatalytic degradation. Approximately 22% of MB was removed by adsorption and later degraded by photocatalytic degradation in 10 min with kinetic constant value (k) of 0.22 min-1, when TiO2/WO3 0.01%wt. was used as photocatalyst. At the highest ratio of TiO2/WO3 0.3%wt., the high adsorption of 57% was found, while the k value of MB photocatalytic degradation was also high as 0.33 min-1. This is because the improvement of photocatalyst properties including band gap energy (< 2.8 eV), specific surface area (> 105.6253 m2/g), pore volume (> 0.2550 cm3/g) and pore size (< 79.571 A°).

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