Pedro H. Britto-Costa

The design of hierarchical copper oxide microstructures with tailored nanomorphologies is essential for next-generation electrocatalytic, sensing, and nanoelectronic applications. Here, we report an atmosphere-controlled thermal oxidation route for the sustainable synthesis of hollow Cu/Cu₂O/CuO microtubes decorated with a dense array of vertically aligned CuO nanowires. The synthesis uses recycled copper microwires from electronic waste (e-waste) coated with a polyurethane (PU) polymer. Comparative analysis under ambient air and high-purity synthetic air reveals that the thermal degradation of the polymeric coating forms a carbon-rich layer, crucial for regulating asymmetric cation transport and inducing mass transport that drives void formation via the Kirkendall effect. This mechanism transforms the solid microwire into a concentric hollow microtube structure. Critically, oxidation under synthetic air promotes the extensive growth of long CuO nanowires (up to 20 μm), guided by anisotropic diffusion along twin boundaries and sustained by a strong chemical potential gradient. These findings establish atmosphere control as a powerful strategy to fine-tune the multiscale architecture of sustainable metal oxide nanostructures from e-waste precursors, opening pathways for the scalable production of multifunctional materials.

This work investigates the incorporation of Vismia guianensis alcoholic extract (EAVG) into cassava starch, with the aim of improving its bioplastic properties. Cassava starch was dissolved into distilled water and doped with 0.2%, 0.5%, and 1.0% EAVG under a temperature controlled at the gelatinization point (∼70 °C) and then cast to form bioplastics. The resulting samples were characterized via attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR), thermogravimetric and differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), atomic force microscopy (AFM), and mechanical essays, providing insights into chemical composition, thermal stability, crystallinity, surface morphology, and mechanical properties. The results demonstrated that EAVG played an effective role, enhancing the flexibility and stability of the bioplastic with potential use in biomedical applications. Moreover, the results also showed significant improvements in mechanical and thermal properties, suggesting that EAVG is a valuable addition to bioplastics. Therefore, EAVG presents a pathway for advancing bioplastics with enhanced mechanical, thermal, and functional characteristics, with the potential for further advancements in these fields.

Porous electrodes have been successfully used for metal electrodeposition from diluted aqueous solution due to their high porosity and specific surface area, which lead to high mass transfer rates. This work studies the mass transfer of copper electrodeposition on reticulated vitreous carbon in a flow reactor without membrane. The flow configuration, otherwise the filter-press electrochemical reactors, was designed in order to minimize the pressure drop. The mass transfer coefficient was determined by voltammetric and galvanostatic electrodeposition. In the voltammetric experiments a Luggin capillary was used to measure the current–potential curves and to determine the limiting current (and, consequently, the mass transfer coefficient). In the galvanostatic experiments the concentration–time curves were obtained and considering a limiting current kinetics model, the mass transfer coefficient (k _m) was determined for different flow velocities. The results showed that both methods give similar values of k _m, thus the voltammetric method can be recommended because it is faster and simpler. Finally, the reactor performance was compared with others from literature, and it was observed that the proposed reactor design has high Sherwood numbers similar to other reactor configurations using membranes and reticulated vitreous carbon electrodes.

This work investigates the removal of metal ions from synthetic aqueous effluents using a spouted bed electrochemical reactor whose cathode was composed of 1.0 mm copper particles. Using a Box–Behnken factorial design, the effects of current (I), electrode thickness (L), draught distance (d) and support electrolyte concentration (C_s) on current efficiency (CE), space–time yield (Y) and energy consumption (EC) were analysed. The results were statistically analysed and the effect of each variable was evaluated using the surface response methodology. The results showed that C_s is the most important variable to consider in the process optimization. A current of 8.0 A can be applied in order to obtain high Y and CE with an acceptable EC. Electrode thicknesses greater than 1.3 cm are not recommended because the irregular potential distribution leads to a Y drop owing to the low CE observed for this condition. The draught distance does not have statistical significance; therefore, the particle circulation rate is not important in this kind of electrochemical reactor.

The use of porous electrodes to remove toxic metals from industrial effluents has been recognized over the years due to its high mass transfer rates resulting in high current efficiencies (CE) and low energy consumption (EC), even at very low metal concentrations. This work addresses the effects of flow velocity and electric current on current efficiency and energy consumption of copper electrodeposition using reticulated vitreous carbon, aiming to optimize the CE and EC by using a modulated current method. First, it was found that a flow velocity of 0.246 m s⁻¹ maximizes the mass transfer coefficient (k_m). Applying this flow velocity and a modulated current, the electrodeposition process was investigated and compared with that carried out under galvanostatic mode. The results showed that using a current control there is a reduction of average EC due to the improvement of the average CE, but the operational time also increases when compared to that obtained using the galvanostatic mode.