Chromium-zinc ferrite nanocomposites for the catalytic abatement of toxic environmental pollutants under ambient conditions

摘要

Highlights•Oxidizing power of zinc ferrite nanocomposites increases with chromium substitution.•Direct correlation between surface acidity and catalytic activity of composites.•Rate of reaction is strongly dependent on catalyst amount and its composition.•Composite is reusable with negligible leaching, indicating heterogeneous mechanism.AbstractCatalytic abatement of 4-chlorophenol, 2,4-dichlorophenol and 2,4-dichlorophenoxy acetic acid in water was investigated by peroxide oxidation over chromium substituted zinc ferrite nanocomposites at ambient conditions. The structural and chemical properties of composites synthesized by sol-gel auto combustion method was studied by X-ray diffraction, Fourier Transform Infra-Red spectroscopy, Transmission Electron Microscopy, surface area, X-ray Fluorescence spectroscopy, Temperature Programmed Reduction and Desorption techniques. Complete removal of 4-CP, DCP and 2,4-D was achieved within 60, 75 and 90min with 96.7/90.5%, 93.88/77.23% and 88.55/62.1% of COD/TOC removal respectively at 298K and 343K. Influence of reaction variables including reaction temperature, oxidant concentration, substrate concentration, catalyst dosage and its composition on the removal efficiency was studied. Kinetic study revealed that wet peroxide oxidation followed a first order kinetic model with rate constant and activation energy of 3.5×10−2min−1/10.7kJ/mole, 9.5×10−3min−1/12.9kJ/mole and 2.29×10−2min−1/17.7kJ/mole respectively for 4-CP, DCP and 2,4-D. The results of five consecutive catalytic runs from X-ray diffraction, Brunauer Emmet Teller surface area and leaching studies from Atomic Absorption Spectrophotometry (AAS) revealed the excellent stability of the catalyst. Scavenging effect ofn-butanol on hydroxyl radical indicated a heterogeneous free radical mechanism.