Photo-treatment of TNT wastewater in the presence of nanocomposite of WO3/Fe3O4

The nanocomposite of WO3/Fe3O4 was prepared using a facile precipitation method and characterized by several techniques. XRD patterns showed a magnetite and a monoclinic structure, respectively, for Fe3O4 and WO3 particles. Formation of WO3/Fe3O4 nanocomposite proved using EDX spectra and also EDX element maps indicated the uniform distribution of Fe, W, and O atoms in the prepared nanocomposite. The SEM image approved a spherical shape for nanocomposite particles. Band-gap energy of WO3/Fe3O4 obtained 1.2 eV using DRS spectra. The room temperature hysteresis loops showed magnetization 21.21 emu/g for WO3/Fe3O4 particles. The synthesized magnetite photocatalyst used in treatment of yellow water as one of the effluents of the production process of TNT. Central composite experimental design applied for optimization of independent variables such as pH of the sample, dose of photocatalyst and amount of pollutant. Photodegradation efficiencies were calculated by reducing the COD values of the samples. The p-values of studied variables obtained <0.05 in ANOVA (analysis of variance) results which indicates their impact on photodegradation efficiency. The F-value and p-value of proposed model for photodegradation process were 29.65 and <0.05, respectively, in 95% confidence level. Also, the p-value of lack-of-fit (>0.05) showed that predicted data of the proposed model fit to actual experimental response data. A 65% reduction in the COD value of a sample was achieved under optimized conditions of pH 5, dose of photocatalyst 1.0 g.L-1 and amount of pollutant 20 mg.L-1.

Automated summary

A nanocomposite of WO3/Fe3O4 was successfully prepared and characterized by various techniques, showing uniform distribution of Fe, W, and O atoms. The nanocomposite exhibited spherical particles and a band-gap energy of 1.2 eV, with a magnetization of 21.21 emu/g. The optimized conditions of pH 5, dose of photocatalyst 1.0 g.L-1 and amount of pollutant 20 mg.L-1 led to a 65% reduction in COD values, demonstrating efficient photodegradation of yellow water effluents. The central composite experimental design helped in determining the impact of independent variables on photodegradation efficiency.