Preparation and photocatalytic performance of tungstovanadophosphoric heteropoly acid salts

Abstract

Tungstovanadophosphoric heteropoly acid H₅PW₁₀V₂O₄₀·5.76H₂O (HPWV) has been synthesized via stepwise acidification and gradual addition of elements. Some metals like Fe, Al and Cu were introduced into the heteropoly acid (HPA) in the molar ratio of 10 : 6, 10 : 6 and 10 : 4 respectively. The prepared catalysts were characterized by UV, FTIR, TG/DTA and XRD. The results indicated that HPWV and its metal salts all contain Keggin units, which are the primary structures of the heteropoly acids. The homogeneous photocatalytic degradation of phenol by heteropoly acid salts was studied in detail under artificial UV irradiation and addition of hydrogen peroxide (H₂O₂), and the effects of initial phenol and H₂O₂ concentrations on the rate of photocatalytic phenol degradation were examined. The results suggested that the heteropoly acid salts showed good catalytic activities for phenol degradation via the ·OH radical mechanism. Under irradiation with a 10 W Hg lamp, 96% phenol was degraded within less than 60 min in the solution containing 50 mg L⁻¹ phenol + 2 μmol L⁻¹ Fe₅(PW₁₀V₂O₄₀)₃ + 4 μmol L⁻¹ H₂O₂, with the performance of the catalysts in order FePWV > AlPWV > CuPWV > HPWV. This work demonstrated that the photo-Fenton reaction catalyzed by the heteropoly acid salts was a promising advanced oxidation tool for the treatment of phenol-containing wastewater.