Magnetic Fenton and Photo-Fenton-Like Catalysts Supported on Carbon Nanotubes for Wastewater Treatment

Carbon nanotubes (CNTs) synthesized by the catalytic decomposition of methane were used as the support for magnetic Fenton and photo-Fenton catalysts to treat real wastewater contaminated with dyes and Escherichia coli. The effect of methane flow, the use of diluent (N-2), and the reaction time in the production of CNTs were studied. An increase in the production of CNTs with increased CH4 flow and a decrease over the reaction time were recorded. Catalysts with 1, 3, and 5% w/w Fe were obtained and characterized by several spectroscopic and microscopic techniques. Multi-walled CNTs and bamboo-like carbon nanofibers with average diameters of 44.0 nm and average lengths of 237.0 nm were obtained. The catalysts had FexOy (oxide species) crystallite sizes between 10 and 18 nm and soft ferromagnetic properties. A factorial 33 design was used for selecting variables for the catalytic tests, wherein the concentration of H2O2, the catalyst mass, and the percentage of iron were evaluated. Subsequently, kinetic experiments were performed. The photo-Fenton process (5% Fe, 200 mg, and 0.4 MH2O2) showed the best results in terms of total organic carbon (TOC) abatement, discoloration, and E. coli inactivation without leaching of Fe.