Tamer Zaki

Transforming pomegranate peel waste into a biodiesel catalyst advances waste-to-resource circularity. A facile hydrothermal carbothermal reduction method was used to synthesize copper-decorated hydrochar nanocomposites derived from peel bio-waste and CuSO ₄ , with Cu(II) concentrations of 10, 25, and 50 mmol/L (denoted as Cu10/HC, Cu25/HC, and Cu50/HC, respectively). The physicochemical properties of the nanocomposites were characterized by FTIR, XRD, BET, XPS, SEM-EDX, and NH₃-TPD, and their catalytic performance was evaluated for biodiesel production via the esterification of oleic acid (OA) with ethanol. Structural analysis confirmed highly pure, crystalline zero-valent copper (Cu⁰) with an FCC nanostructure and spherical morphology (average size ~ 25–63 nm), well-dispersed throughout the hydrochar-derived carbon matrix. XPS verified oxygen functionalities (–COO⁻, > C = O, C–OH) alongside Cu⁰ on the nanocomposite surfaces. Moreover, textural analysis revealed that Cu25/HC exhibited the highest surface area (29.6 m²/g) and pore volume (0.099 cm³/g), whereas Cu50/HC showed reduced porosity but introduced significant acidity (54.9 µmol/g, according to NH ₃ -TPD). Catalytic efficiency increased with higher Cu dispersion density (Cu atoms/nm ² ; R² =0.996): Cu50/HC achieved the best performance (97.4% conversion), followed by Cu25/HC (96.6%) and Cu10/HC (96.0%), outperforming bulk Cu content and BET surface area. Under optimal conditions (70 °C, 5 h, 1.0 wt% catalyst relative to OA, and an ethanol/OA molar ratio of 15:1) the Cu50/HC catalyst attained complete OA conversion. Thermodynamic parameters were determined and indicated an endergonic and thermodynamically non-spontaneous reaction. Notably, the catalyst retained 97.1% of its initial activity after six consecutive cycles, demonstrating excellent operational stability, as confirmed by the FTIR, XRD, and Cu content. These findings position the Cu50/HC nanocomposite as a cost-effective, sustainable, and efficient catalyst for biodiesel production.

Herein, we synthesized Ti-MOF through a solvothermal method and subsequently calcined it to form anatase TiO₂. We further developed a Bi₂O₃@TiO₂ mixed oxide using impregnation and calcination processes. These oxides showed significant photocatalytic activity for degrading Eriochrome Black T (EBT) dye under visible light irradiation. We characterized the prepared samples using various techniques, including XRD, XPS, FTIR, BET, SEM, EDX, TEM, and UV-DRS analyses. Our results indicated that TiO₂ and 10%Bi₂O₃@TiO₂ achieved 80% and 100% degradation of EBT dye solution (50 ppm) within 30 min in acidic medium with a 50 mg catalyst dose, respectively. The calcination of the Ti-MOF into TiO₂ improved its sensitivity to visible light. The Bi₂O₃@TiO₂ composite was also effective in degrading other organic pollutants, such as Congo Red (degradation ~99%), Malachite Green (degradation ~95%), Methylene Blue (degradation ~81%), and Safranine O (degradation ~69%). The impregnation of Bi₂O₃ increased the surface acidity of TiO₂, enhancing its photocatalytic activity by promoting hydroxyl group formation through increased water adsorption. Additionally, 10%Bi₂O₃@TiO₂ demonstrated excellent chemical stability and reusability, maintaining high degradation efficiency over four cycles. Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) calculations were performed to understand the degradation mechanisms. UV-Vis absorption spectrum simulations suggested that the anionic HEB⁻² (O24) or EB⁻³ forms of the EBT dye are likely to undergo degradation. This study highlights the potential of Bi₂O₃@TiO₂ composites for effective photocatalytic applications in environmental remediation.

In this work, Ni-bentonite catalyst was synthesized through exchange method. The synthesized catalyst and the pristine clay were characterized by XRD, XRF, TGA/TDA, TEM, EDX-mapping, nitrogen adsorption-desorption at −196 °C, H₂-TPD and NH₃-TPD. The catalytic efficiency of the dispersed nickel catalyst toward the hydrocracking of mazut (heavy residual fuel oil) under reduced pressure has been evaluated. The experimental results showed increasing yield of middle distillate fraction to 71 wt.% as the reaction temperature raised to 430 °C under pressure 2.0 MPa.