Decolorization of methyl orange dye by photo-Fenton process using silica gel/iron oxide catalyst

Dyes are generally considered as serious water pollutants which are massively produced in textile, plastic, leather and dye industries. These contaminants need to be removed from the wastewaters. In this study, we developed a new method for preparing a photocatalyst for degradation of methyl orange dye. For this, a series of silica gel/iron oxide nanocomposites were prepared by a solid phase ion-exchange method. The physical and chemical characteristics of nanocomposites were investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), diffusion reflection spectroscopy (DRS) and adsorption/desorption isotherms of nitrogen Brunauer???Emmett???Teller. Then, there photocatalytic performance was evaluated for the photo-Fenton decolorization of methyl orange dye. The results showed that the synthesized nanocomposite in 3 h had the best color decol-orization efficiency of 72.6%. Based on the EDX results, the amount of iron in the synthesized nano -composites during 1, 3 and 5 h were equal to 1.4, 1.5 and 1.6 wt.%, which were very close to each other. The DRS analysis showed the presence of FexOy cluster oligomers and large Fe2O3 particles in the synthesized nanocomposite. The specific surface area of the silica gel was 340 m2/g. The ion -exchange reduced the surface area to about 260 m2/g. The optimal pH in the degradation of dye was about 2, which resulted in 89.4% decolorization. The decolorization efficiency was enhanced with the increase of the amount of photocatalyst in the reaction medium to 10 g/L enhanced; however, fur-ther increase had a negative effect on the reaction. Also, the duration of decolorization was increased in the high concentrations of dye. It has been concluded that the solid-state ion-exchange method has a great potential in the production of photocatalysts for methyl orange dye degradation.

Automated summary

This study developed a new photocatalyst for degradation of dyes and prepared silica gel/iron oxide nanocomposites using a solid phase ion-exchange method. The synthesized nanocomposite showed the best decolorization efficiency after 3 hours, and the solid-state ion-exchange method has potential in photocatalyst production.