| Summary: | The appearance of organic pollutant in aquatic environment has become a concern due to their toxicity that could cause chronic health issues and could affect the rate of photosynthetic and biological growth in the water body. The utilization of heterogeneous photocatalysis as part of advanced oxidation processes provides sustainability to treat organic pollutants due to its superiorities such as more effective chemical reaction, high recyclability, no water disposal problem issues, and its low cost. Graphitic carbon nitride (g-C3N4, GCN) and titanium dioxide (TiO2) have been known as one of the best photocatalyst for photodegradation process because of their advantages including their quality of being environmentally benign, effective, low cost, and having high physicochemical stability. Unfortunately, those photocatalysts faced challenging issues which hampered their photoactivity, such as high charge carrier recombination of GCN and larger band-gap of TiO2. Those issues can be resolved by applying nanostructure modification of GCN into 1D/2D homojunction by chemical-thermal polymerization, addition of ionic liquid in synthesis process of GCN and TiO2 via hydrothermal, bringing out the heterojunction effect by combining 1D/2D nanostructured GCN, and construction of thin-film photocatalyst via vacuum filtration process which is considered as the significances of this research. The objective of this research covers the study of the synthesis mechanism of 1D/2D nanostructured GCN and multi element doped TiO2, investigation on the effect to ionic liquid toward morphology, elemental, electronical, surface and pore aspects of each as-synthesized GCN and TiO2, determination and evaluation of the performance of GCN, TiO2, and GCN/TiO2 thin film in degrading malachite green oxalate (MGO) as organic pollutant model under visible-LED light radiation with the assistance of H2O2. The mechanism of GCN formation with 1D/2D nanostructure and TiO2 with multi element doping were explained in detail. The characterization of thin-film photocatalyst using field emission scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, N2 adsorption-desorption isotherm, ultraviolet-visible-near infrared diffused reflectance spectroscopy, Raman spectroscopy, and X-ray diffraction justified the effect of ionic liquid toward morphological, elemental, surface and pore, chemical bonding, optical and crystalline properties of fabricated thin-film. The performance test revealed that the 1D/2D nanostructured GCN, multi element doped TiO2, and multi element doped TiO2/nanostructured GCN could accelerate photodegradation of MGO (20 ppm) under low-energy visible-LED light (50 W) radiation with the maximum percentage and reaction rate of 85.13, 97.23, 99.2% and 0.0137, 0.029, 0.0447 min-1, respectively. Lastly, the mechanism of MGO photodegradation employing thin-film photocatalyst was investigated. This study demonstrated a promising approach by utilizing advanced photocatalyst thin film containing multi-element doped TiO2 and 1D/2D nanostructured GCN for effective photodegradation of MGO as an organic pollutant.
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