Synthesis and characterization of sodium tungstate: Investigation of energy storage mechanism effect and its photocatalytic application

In the present work, Na2WO4 was synthesized for photocatalytic degradation towards palm oil mill effluent (POME). The synthesized Na2WO4 was characterized of their thermal and optical properties via thermogravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS), respectively. The energy storage potential as the newest scheme in photocatalytic performance was assessed by their color and Chemical Oxygen Demand (COD) removal. Result revealed that Na2WO4 photocatalyst is inconsistent for photocatalysis of the aforementioned decolorization and degradation towards POME. In addition, result showed an optimal calcination temperature for maximal degradation of POME at 400°C. The highest efficiency of decolorization and degradation of POME were found to be W4 (25%) under visible-light-driven (VLD) scheme, and W6 (53%) for energy storage material (ESM) scheme under visible-light irradiation. The results indicated that the influence of calcination temperature of Na2WO4 with addition of citric acid used in the synthesis procedure did not have a strong influence on the thermal and optical properties. Meanwhile, the decolorization and degradation of POME have been observed during temperature increment. It was found that increased calcination temperature led to smaller bandgaps, which emerged at the optical absorption edges. This shows synthesized Na2WO4 demonstrated suitable bandgap of photocatalyst and can, therefore, have promising photocatalytic applications.