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 (N₂), 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 Fe_xO_y (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 M H₂O₂) showed the best results in terms of total organic carbon (TOC) abatement, discoloration, and E. coli inactivation without leaching of Fe.