This paper reports the successful synthesis of spinel‐type CuFe ₂ O ₄ ferrite nanoparticles with an average particle size of 24 nm, produced using the citrate sol–gel autocombustion method. The structure of the synthesized material was analyzed through x‐ray diffraction (XRD) and further supported by Raman and FT‐IR spectroscopy. The analysis confirmed that the material formed a spinel ferrite structure with the Fd3m space group. Valence states and energy levels of the elements were examined using x‐ray photoelectron spectroscopy (XPS). Surface morphology was studied using scanning electron microscopy (SEM), coupled with elemental analysis. The magnetic properties of the synthesized CuFe ₂ O ₄ ferrite nanoparticles were investigated using a vibrating sample magnetometer (VSM). Magnetization measurements revealed that the sample exhibited characteristic magnetic parameters of copper ferrite, with a saturation magnetization (Ms) of 23.10 emu/g, a coercivity Hc of 415 Oe, and a remnant magnetization (Mr) of 12.80 emu/g. These magnetic properties enable efficient magnetic separation of the nanoparticles from aqueous solutions, thereby enhancing process efficiency and minimizing catalyst loss during photocatalytic applications. Optical and photocatalytic properties were investigated using spectrophotometry, revealing an optical band gap of 1.85 eV, which demonstrates potential for photocatalytic activity under visible light. The CuFe ₂ O ₄ ferrite effectively degraded dyes such as methylene blue (MB), malachite green (MG), Safranine (S), Congo Red (CR), and Rhodamine B (RhB) within 180 min, highlighting its practical application potential. The study identified that hydroxyl radicals (·OH), generated from H ₂ O ₂ decomposition under visible light irradiation, played a critical role in enhancing the efficiency of the photo‐Fenton reaction. A proposed mechanism involves the excitation of CuFe ₂ O ₄ under visible light, facilitating electron transfer that leads to the generation of ·OH radicals, which degrade the dye molecules. Among the tested dyes, CR exhibited the highest degradation percentage with a rate constant of 0.033 min⁻ ¹ and followed a pseudo‐first‐order kinetic model. The effect of hydrogen peroxide concentration on dye degradation efficiency was also evaluated.

The present work reports the results of a systematic study on the evolution of the morphological properties of porous carbons derived from coffee waste using a one-pot potassium-hydroxide-assisted process at temperatures in the range of 400–900 °C. Raw materials and obtained carbons were studied by TG, DTG, SEM and nitrogen adsorption porosimetry. The decomposition temperature ranges for hemicellulose, cellulose and lignin as the main component of the feedstock have been established. It is shown that the proposed method for the thermochemical treatment of coffee waste makes it possible to obtain activated carbon with a controllable pore size distribution and a high specific surface area (up to 1050 m²/g). A comparative study of the evolution of the distribution of pore size, pore area and pore volume has been carried out based on the BJH and NL-DFT (slit-like pores approximation) methods. The fractal dimension of the obtained carbons has been calculated by Frenkel–Halsey–Hill method for single-layer and multilayer adsorptions.

A comprehensive study of the correlation between the structural and morphological parameters and the frequency-temperature dependences of the conductivity of porous carbon materials obtained by carbonization of hemp fibers has been carried out. The effect of treatment with nitric acid and additional annealing on the transport of charge carriers in carbon materials carbonized in the temperature range of 500–1000 °C has been established. Porous carbon materials have been described as a heterophase system, in which highly conductive graphitized particles are separated by low conductivity amorphous carbon, from the standpoint of the effect of carbonization temperature and changes in the morphology of materials due to acid treatment and annealing on the formation of conduction channels with the simultaneous implementation of fluctuation-assisted tunneling between graphitic clusters separated by low conductive barriers and the formation of conduction channels as a result of contact of individual graphitized carbon clusters. A model has been constructed that relates the results of measuring the specific surface area and pore size distribution, changes in the size of graphite crystallites, and changes in conductivity with temperature. The possibility of applying the theory of percolation conductivity to describe the charge transport has been analyzed and the percolation threshold has been established.