A novel iron-containing polyoxometalate heterogeneous photocatalyst for efficient 4-chlorophennol degradation by H2O2 at neutral pH

An iron-containing polyoxometalate (Few LysSiW) was synthesized from ferric chloride (Fe), lysine (Lys) and silicotungstic acid (SiW), and characterized using ICP-AES, TG, FT-IR, UV-vis DRS, XRD and SEM. The chemical formula of Fe(III)LysSiW was determined as [Fe(H2O)(5)(C6H14N2O2)HSiW12O40 center dot 8H(2)O, with Keggin-structured SiW12O404- heteropolyanion and lysine moiety. As a heterogeneous catalyst, the as prepared FeffiLysSiW showed good performance in the degradation of 4-chlorophenol by H2O2 in both the dark and irradiated systems. Under the conditions of 4-chlorophenol 100 mg/L, FeffiLysSiW 1.0 g/L, H2O2 20 mmol/L and pH 6.5, 4-chlorophenol could be completely degraded in ca. 40 min in the dark and ca. 15 min upon irradiation. Prolonging the reaction time to 3 h, the TOC removal reached to ca. 71.3% in the dark and ca. 98.8% under irradiation. The catalytic activity of Fein LysSiW stems from synergetic effect of ferric iron and SiW12O40-4 in the catalyst, corresponding to Fenton-like catalysis and photocatalysis, respectively. The enhanced degradation of 4-CP under irradiation is due to the simultaneous oxidation of 4-CP through the Fenton-like and photocatalytic processes. The high catalytic activity of Fe(III)LysSiW is also strongly related to the chemisorption of H2O2 on Fe(III)LysSiW surface by hydrogen bonding, which promotes both the Fenton-like and photocatalytic processes. (C) 2016 Elsevier B.V. All rights reserved.