Abstract
The rapid population growth and economic development have largely contributed to environmental pollution. Various advanced oxidation processes have been used as the most viable solution for the reduction of recalcitrant pollutants and wastewater treatment. Heterogeneous photocatalysis is one of the broadly used technologies for wastewater treatment among all advanced oxidation processes. Graphitic carbon nitride alone or in combination with various other semiconductor metal oxide materials acts as a competent visible light active photocatalyst for the removal of recalcitrant organic pollutants from wastewater. Rational designing of an environment-friendly photocatalyst through a facile synthetic approach encounters various challenges in photocatalytic technologies dealing with semiconductor metal oxides. Doping in g-C3N4 and subsequent coupling with metal oxides have shown remarkable enhancement in the photodegradation activity of g-C3N4-based nanocomposites owing to the modulation in g-C3N4 bandgap structuring and surface area. In the current study, a novel ternary Fe-doped g-C3N4/Ag2WO4 visible light active photocatalyst was fabricated through an ultrasonic-assisted facile hydrothermal method. Characterization analysis included SEM analysis, FTIR, XRD, XPS, and UV-Visible techniques to elucidate the morphology and chemical structuring of the as-prepared heterostructure. The bandgap energies were assessed using the Tauc plot. The ternary nanocomposite (Fe-CN-AW) showed increased photodegradation efficiency (97%) within 120 minutes, at optimal conditions of pH = 8, catalyst dose = 50 mg/100 ml, an initial RhB concentration of 10 ppm, and oxidant dose 5 mM under sunlight irradiation. The enhanced photodegradation of rhodamine B dye by ternary Fe-CN-AW was credited to multielectron transfer pathways due to insertion of a Fe dopant in graphitic carbon nitride and subsequent coupling with silver tungstate. The data were statistically assessed by the response surface methodology.
Highlights
Water constitutes a major part of the planet Earth
Iron-doped graphitic carbon nitride was coupled with silver tungstate in which WO4 has attracted attention due to high chemical and thermal stability and has reasonable electron transfer behavior. g-C3N4 and WO4 have almost similar bandgaps [14]. e degradation of rhodamine B (RhB) dye was analyzed over Fe/g-C3N4 (Fe–CN), g-C3N4/ Ag2WO4 (CN-AW), and Fe-doped g-C3N4 -Ag2WO4/(Fe-CNAW). e photocatalytic activity of these three catalysts towards RhB degradation was studied under sunlight. e effect of various parameters, for example, pH, oxidant dose, irradiation time, and catalyst dose, was optimized. e interaction of various parameters was studied using the response surface methodology (RSM). e catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, X-ray diffraction (XRD), XPS, and UVVis techniques
FTIR spectra showed all the characteristic transmittance peaks of g-C3N4 confirming the synthesis of graphitic carbon nitride, without any prominent change at different temperatures, as shown in Figure 2(f ). e broad absorption band of pristine g-C3N4 can be seen in all the samples synthesised at various temperatures. e bands beyond 3000 cm−1 up to 3300 cm−1 are due to N–H bond stretching vibration resulting from partial condensation of amino acids. e series of peaks appearing between 1200 cm−1 and 1620 cm−1 shows the stretching vibrations of CN heterocycles
Summary
Water constitutes a major part of the planet Earth. Almost 98% of this water is seawater and cannot be used for drinking purposes because of the high salt content. Is gross negligence from various industrial units for releasing wastewater without any treatment into freshwater streams has posed grave threats to human health [2] Conventional methods such as activated carbon adsorption, filtration, extraction, oxidation, ultrafiltration, electrolysis, chemical oxidation, and biological treatment were used which usually caused incomplete mineralization of pollutants. Doping of a transition metal in g-C3N4 lattices alters the physical and chemical properties and enhances the visible light absorption response for degradation of pollutants by changing the structure and surface area of g-C3N4 [11]. Iron-doped graphitic carbon nitride was coupled with silver tungstate in which WO4 has attracted attention due to high chemical and thermal stability and has reasonable electron transfer behavior. Iron-doped graphitic carbon nitride was coupled with silver tungstate in which WO4 has attracted attention due to high chemical and thermal stability and has reasonable electron transfer behavior. g-C3N4 and WO4 have almost similar bandgaps [14]. e degradation of rhodamine B (RhB) dye was analyzed over Fe/g-C3N4 (Fe–CN), g-C3N4/ Ag2WO4 (CN-AW), and Fe-doped g-C3N4 -Ag2WO4/(Fe-CNAW). e photocatalytic activity of these three catalysts towards RhB degradation was studied under sunlight. e effect of various parameters, for example, pH, oxidant dose, irradiation time, and catalyst dose, was optimized. e interaction of various parameters was studied using the response surface methodology (RSM). e catalysts were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, X-ray diffraction (XRD), XPS, and UVVis techniques
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