This review examines in detail all components involved in heterogeneous Fenton-type reactions, with special focus on copper species supported on alumina for H₂O₂ decomposition, their redox chemistry, and their practical advantages over traditional Fenton for the degradation of recalcitrant organic compounds. Several aspects for a deeper comprehension of the properties of γ-Al₂O₃ as support for catalytic applications are discussed. Iron-free systems stability after calcination and catalyst performance during the oxidation reaction are evaluated to solve the disadvantages of iron-based system. Copper species supported on alumina for H₂O₂ decomposition in Fenton-like reactions are examined, with special focus on their redox chemistry and practical advantages over traditional Fenton system for recalcitrant compounds degradation. Characterization techniques for the elucidation of the structures, compositions, and chemical properties of both the solids used in heterogeneous catalysis, and the adsorbates and intermediates present on the surfaces of the catalysts during reaction are explained. Global indicators for chemical characterization of wastewaters and measurement of catalytic efficiency are described.

This work proposes a kinetic model for the reactions involved in the heterogeneous copper-based Fenton-type oxidation of mixed recalcitrant compounds in a real industrial effluent from the alkaline sulfite treatment of wood. This kind of treatment is unusual in this industry due to the complexity of the effluents and the high costs involved in total mineralization of the organic matter. Nevertheless, conversion of recalcitrant to degradable compounds and catalyst recovery can make the difference. The complexity of the effluent and the great number of compounds formed as intermediates, make extremely difficult the identification and quantification of the individual reactions that occur during oxidation. To solve this drawback TOC parameter was used as a representative measurement. To verify the level of TOC degradation produced by the heterogeneous catalysis reaction, experiences of homogeneous catalysis and adsorption were accomplished. The studied temperature range was 45–80 °C. A “two-step” kinetic model was applied to TOC reduction in heterogeneous and homogeneous oxidations, admitting two sequential steps of oxidation: a first fast stage (“seconds stage”) followed by a slow one (“minutes stages”). Kinetic constants were obtained for both processes and activation energies were also determined for the “minutes stage” step (33.17 kJ/mol and 15.13 kJ/mol, respectively). Homogeneous catalysis studies confirm mass transfer limitations in heterogeneous oxidations. Experiences of adsorption of organic matter on CuO/γ-Al₂O₃ catalyst demonstrated that this phenomenon is exothermic and cannot be neglected. The activation energy of adsorption was determined as 7.32 kJ/mol. Catalysts were characterized through SEM, EDS, XRD, FTIR, and TGA.

The conversion of cellulosic biomass into renewable chemicals can serve as a sustainable resource for levulinic acid (LA) production. LA yield is significantly influenced by reaction temperature, reaction time, substrate concentration, active sites, catalyst amount, catalyst porosity, and durability. Beyond the features of the catalyst, such as acidity, porosity, functional groups, and catalytic efficiency, the contact between the solid acid catalyst and the solid substrate is of vital importance. Solid-based catalysts show remarkable catalytic activity for cellulose-derived LA production, thanks to the incorporation of functional groups. For a solid carbon-based catalyst to be effective, a synergistic interaction between the binding domain (functional groups capable of anchoring cellulose to the catalyst surface, such as chloride groups, COOH, or OH) and the hydrolysis domain (due to their ability to cleave glycosidic bonds, such as in SO₃H) is essential. As a relatively new market niche, carbon-based catalyst supports are projected to reach a market value of nearly USD 125 million by 2030. This review aims to highlight the advantages and limitations of carbon-based materials compared to conventional catalysts (including metal oxides or supported noble metals, among others) in features like catalytic activity, thermal stability, and cost, examine recent advancements in catalyst development, and identify key challenges and future research directions to enable more efficient, sustainable, and scalable processes for LA production. The novelty of this review lies in its focus on carbon-based catalysts for LA production, emphasizing their physical and chemical characteristics.

Because of their chemical complexity, industrial chemi‐mechanical pulping effluents are evaporated and burned, in spite of the high associated cost involved in these processes. The aim of this study was to remove recalcitrant compounds from this kind of wastewater using a Fenton‐type treatment. The main parameters involved in the process and their influence on the results were determined. Homemade catalysts based on CuO, Fe₂O₃, NiO, and ZnO, supported on γ‐Al₂O₃ have been tested for catalytic oxidation, and the CuO/γ‐Al₂O₃ catalysts showed the greatest effect on total organic carbon (TOC) reduction (52.7%). A series of two‐level factorial experiments was subsequently applied to evaluate the most favorable range of conditions for CuO/γ‐Al₂O₃ application. The studied variables were hydrogen peroxide concentration ([H₂O₂], g/L), active phase content (metal oxide supported on alumina,%), mass of catalyst (metal oxide/alumina system, g), and reaction temperature (°C). The highest reduction of all parameters was obtained at the superior level of all variables with CuO/γ‐Al₂O₃, achieving reductions of chemical oxygen demand (COD) and TOC between 40 and 50%. Increasing catalyst mass did not produce additional benefit. This variable has a significant effect only on the reduction of aromatic compounds. At its low level, reduction in aromatic content exceeded 80%. Color reduction was influenced only by temperature (maximum reduction of 90%).