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

Catalytic 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 90 min with 96.7/90.5%, 93.88/77.23% and 88.55/62.1% of COD/TOC removal respectively at 298 K and 343 K. 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 × 10−2 min−1/10.7 kJ/mole, 9.5 × 10−3 min−1/12.9 kJ/mole and 2.29 × 10−2 min−1/17.7 kJ/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 of n-butanol on hydroxyl radical indicated a heterogeneous free radical mechanism.