Enhanced photocatalytic activity of Fe3O4-WO3-APTES for azo dye removal from aqueous solutions in the presence of visible irradiation

Development of highly active photocatalysts for treatment of dye-laden wastewaters is vital. The photocatalytic removal of azo dye Reactive Black 5 was investigated by Fe3O4-WO3-3-aminopropyltriethoxysilane (APTES) nanoparticles in the presence of visible light. The Fe3O4-WO3-APTES nanoparticles were synthesized via a facile coprecipitation method. The photocatalyst was characterized by XRD, FT-IR, SEM, EDX, VSM, UV-Vis, and pH(PZC) techniques. The effects of some operational parameters such as solution pH, nanophotocatalyst dosage, initial RB5 concentration, H2O2 concentration, different purging gases, and type of organic compounds on the removal efficiency were studied by the Fe3O4-WO3-APTES nanoparticles as a photocatalyst. Maximum phtocatalytic activity was obtained at pH 3. The photocatalytic removal of RB5 increased with increasing H2O2 concentration up to 5 mM. The removal efficiency declined in the presence of different purging gases and all types of organic compounds. First-order rate constant (k(obs)) decreased from 0.027 to 0.0022 min(-1) and electrical energy per order (E-Eo) increased from 21.33 to 261.82 (kWh/m(3)) with increasing RB5 concentration from 10 to 100 mg/L, respectively. The efficiency of LED/Fe3O4-WO3-APTES process for RB5 removal was approximately 89.9%, which was more effective than the LED/Fe3O4-WO3 process (60.72%). Also, photocatalytic activity decreased after five successive cycles.