Synthesis and characterization of titanium dioxide nanoparticles deposited via direct heating technique
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Date
2019-07
Authors
Soo Qian Yee
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Abstract
Industrial effluent has become critical environmental issue due to the difficulty in decomposing the persistent organic pollutants such as synthetic dyes by conventional wastewater treatment approaches. Advanced oxidation process (AOPs) based on titanium dioxide (TiO2) photocatalyst is one of the promising methods for effluent treatment. The commonly used approaches to synthesize TiO2 particles are hydrothermal or solvothermal methods. Nevertheless, these methods consume high electrical energy and take longer time for the synthesis process. Besides, TiO2 particles are easily carried away by flowing wastewater during photocatalysis process, generating secondary pollution in water system. In order to address these problems, direct heating method was developed in order to deposit TiO2 nanoparticles on Kanthal wire. Various characterization methods were used to characterize TiO2 nanoparticles such as X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscope (TEM), X-Ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopy (UV-Vis).The optimum condition for synthesizing ultrafine TiO2 nanoparticles (4.962 ± 1.035 nm) were heating power (60 W), pH solution (pH 7) and heating duration (60 min). Ostwald ripening was apparent with low heating power (45 W) whereas secondary nucleation was prominent with high heating power (>50 W). Coalescence and large size of TiO2 nanoparticles was observed in pH 7 solution. As heating duration increased, thicker TiO2 layer was formed, accompanied with cracking. TiO2 nanoparticles (by-products) exhibited the highest photodegradation efficiency under exposure of visible light (37.16%) as compared to UV light (7.11%). The photodegradation mechanism of RhB dye by TiO2 nanoparticles under visible light was proposed based on the scavenger test that indicated that the dominant reactive species were •O2 - and e- while the minor reactive species was •OH.