Heterogeneous Fenton-like degradation of 4-chlorophenol using a novel FeIII-containing polyoxometalate as the catalyst

• A novel FeIII-containing polyoxometalate (POM) with Keggin unit was synthesized.
• Catalytic degradation of 4-chlorophnol in the POM/H2O2 system was studied.
• The POM shows superior catalytic performance from acidic to neutral pH values.
• A possible mechanism involved redox cycles on the catalyst surface was proposed.

Fenton-like degradation of 4-chlorophenol (4-CP) in aqueous solution was studied over a novel FeIII-containing polyoxometalate (POM) as heterogeneous catalyst. The POM, assigned as FeIIIAspPW12, was synthesized via precipitation reaction of phosphotungstic acid (PW12) with the complex of ferric ion and aspartic acid (Asp) in aqueous solution. The catalyst displays high activity and good reusability for oxidation of 4-CP by hydrogen peroxide in the range from acidic to circumneutral pH values. The enhanced oxidation of 4-CP was observed when the reaction system was irradiated by a high pressure mercury lamp. Under the conditions of H2O2 20 mM, FeIIIAspPW12 0.2 g/L, temperature 25 ± 2 °C and pH 6.5, the complete total organic carbon (TOC) removal for 100 mg/L 4-CP solution could be achieved in both dark and irradiation systems within 120 and 60 min, with H2O2 utilization of 77% and 83% respectively. It is speculated that the catalysis may possibly undergo the redox cycles of FeIII ⇌ FeII and POM ⇌ POM− on the surface of FeIIIAspPW12, accompanied by hydroxyl radical formation from H2O2, and the oxidation of 4-CP consequently.

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