The development of heterostructures incorporating photocatalysts optimized for visible-light activity represents a major breakthrough in the field of environmental remediation research, offering innovative and sustainable solutions for environmental purification. This study explores the photocatalytic capabilities of a SnFe₂O₄/g-C₃N₄ heterojunction nanocomposite, successfully synthesized from graphitic carbon nitride (g-C₃N₄) and tin ferrate (SnFe₂O₄) and applied to the degradation of the cationic dye brilliant cresyl blue (BCB) in an aqueous solution. These two components are particularly attractive due to their low cost and ease of fabrication. Various characterization techniques, including XRD, FTIR, SEM, and TEM, were used to confirm the successful integration of SnFe₂O₄ and g-C₃N₄ phases in the synthesized catalysts. The photocatalytic and photo-Fenton-like activity of the heterojunction composites was evaluated by the degradation of brilliant cresyl blue under visible LED illumination. Compared to the pure components SnFe₂O₄ and g-C₃N₄, the SnFe₂O₄/g-C₃N₄ nanocomposite demonstrated a superior photocatalytic performance. Furthermore, the photo-Fenton-like performance of the composites is much higher than the photocatalytic performances. The significant improvement in photo-Fenton activity is attributed to the synergistic effect between SnFe₂O₄ and g-C₃N₄, as well as the efficient separation of photoexcited electron/hole pairs. The recyclability of the SnFe₂O₄/g-C₃N₄ composite toward BCB photo-Fenton like degradation was also shown. This study aimed to assess the modeling and optimization of photo-Fenton-like removal BCB using the SnFe₂O₄/g-C₃N₄ nanomaterial. The main parameters (photocatalyst dose, initial dye concentration, H₂O₂ volume, and reaction time) affecting this system were modeled by two approaches: a response surface methodology (RSM) based on a Box–Behnken design and artificial neural network (ANN). A comparison was made between the predictive accuracy of RSM for brilliant cresyl blue (BCB) removal and that of the artificial neural network (ANN) approach. Both methodologies provided satisfactory and comparable predictions, achieving R² values of 0.97 for RSM and 0.99 for ANN.

The treatment of sewage wastewater generates a substantial amount of sludge, which poses significant ecotoxicological and environmental challenges. Managing this sludge is critical, as traditional disposal methods carry risks: agricultural use can lead to environmental contamination, while landfill disposal raises concerns about solid waste management and the preservation of landfill sites. Our research focuses on converting this urban sludge into activated carbon. We employed various techniques to characterize NaOH-activated biochar, including infrared (IR) analysis. BET analysis revealed a specific surface area of 62.35 m²/g. We also assessed NaOH-activated biochar for its effectiveness in adsorbing brilliant cresyl bleu (BCB). The SSE error calculations indicated a first-order adsorption, while the isotherms suggested a better fit with the Sips model, indicating heterogeneous adsorption with an ns value of 0.95. Our study highlights the effectiveness of biochar in adsorbing dyes such as brilliant cresyl bleu BCB.

Water pollution caused by synthetic dyes is a major environmental concern due to their stability, toxicity, and resistance to conventional wastewater treatments. This study presents a sustainable approach for synthesizing zinc oxide (ZnO) nanoparticles using artichoke biomass (waste) as a green precursor and enhancing their visible light photocatalytic activity through phosphorus doping. ZnO nanoparticles were successfully synthesized via a simple green route and doped with 3–6% phosphorus using NH₄H₂PO₄. The structural, morphological, and optical properties of the resulting P-ZnO were characterized by XRD, SEM/EDX, TEM, FTIR, and UV-Vis spectroscopy. (6 wt%) Phosphorus doping effectively reduced the band gap from 3.06 eV to 2.95 eV, extended light absorption into the visible range, and improved electron–hole separation, resulting in enhanced photocatalytic performance. The P-ZnO nanoparticles were evaluated for methylene blue (MB) degradation under visible light in a photo-Fenton-like process, with H₂O₂ as an oxidant. The degradation efficiency reached 87.05% with 6% P-ZnO and further increased to 92.35% upon addition of H₂O₂. Durability and reusability tests demonstrated that the 6% P-ZnO catalyst maintained its activity and structural integrity over four consecutive cycles, indicating negligible loss of efficiency and excellent resistance to surface poisoning. The photocatalytic activity was strongly impacted by the quantity of catalyst, solution pH, and initial dye levels, with optimal performance at 0.3 g/L catalyst loading, pH 3, and lower MB concentrations.

To decrease the environmental and health consequences associated with pollution, several cobalt oxides-decorated biochar substrates have been developed for effective catalytic reduction of 4-NP. The porous biochar was produced by pyrolysis of sewage sludge and acid demineralization, and subsequently, Co₃O₄ was loaded with varying amounts to synthesize Co₃O₄/biochar nanocomposites. The characterization of the materials included FTIR, XRD, SEM/EDX, TEM, BET, CHNS elemental analysis, TGA/DTA, and pH_pzc analysis. The catalytic activity of synthesized composites was monitored by UV-Vis spectroscopy to measure the transformation of a priority toxic pollutant, 4-NP, to a desirable pharmaceutical intermediate, 4-AP, by NaBH4, considering it a reducing agent. The influence of corresponding parameters such as catalyst dosage, NaBH₄ concentration, and Co₃O₄ content in the composite on the reduction time of 4-NP was modelled using central composite design (CCD) of RSM. The optimal conditions for the catalytic reduction of 0.3 mM 4-NP were found to be a catalyst dosage of 5 mg, a NaBH₄ concentration of 26 mM, and a Co₃O₄ loading of 13%, resulting in complete reduction within 5 min. The optimized catalyst displayed a high porosity, well dispersion of Co₃O₄ nanoparticles, good catalytic stability, and cost-effectiveness, revealing new insights into application of cobalt oxide and sewage sludge for pollutant reduction.