Search

This study explores the use of in situ electrochemical process to regenerate granular activated carbon (GAC) loaded with carbendazim (CBZ) and simultaneously oxidize the contaminant. The experiment optimized the flow rate ($Q$ Q), current density ($j$ j), cathodic or anodic chamber, and electrolyte type to achieve the best results. The study found that using GAC in the cathodic chamber and NaCl as a supporting electrolyte, with a $j$ j = 0.5 mA cm−2, and $Q$ Q = 100 L h−1, led to a 64% regeneration with an energy consumption of 0.15 kWh kg−1, which is at least 16× lower than those found in the literature for electrochemical, microwave and thermal processes. Consecutive regeneration tests revealed a decrease in GAC adsorptive capacity over time due to blockage by transformation products, and mainly by oxidation-induced changes in pore structure, as confirmed in dissolved organic carbon (DOC), scanning electron microscopy (SEM), and surface area results. The results also showed that in all tested conditions, residual CBZ was not found in the electrolyte solution. Overall, electrochemical regeneration proved to be an energy-efficient method for extending the lifespan of GAC and minimizing disposal in landfills. [ABSTRACT FROM AUTHOR]

This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z -position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈 D 〉) and Z -position, characterized by a phenomenological equation〈D〉XRDn(Z)=〈D〉0n1+32rZ2+158rZ4, which is further supported by a growth exponent ( n ) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3-4.6 μ Ω · cm. Upon thermal annealing at 200 °C, cuprite Cu 2 O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu 2 O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu 2 O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu 2 O with size close than the Bohr exciton diameter (5 nm) of the Cu 2 O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼10 14 cm -3 , showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu 2 O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications., (© 2024 IOP Publishing Ltd.)

The present study analyzed the performance of photochemical and electrochemical techniques in the degradation and mineralization of the pesticide carbendazim (CBZ). Direct photolysis (DP), heterogeneous photocatalysis (HP), photoelectrocatalysis (PEC), and electrochemical oxidation (EO) were tested, and the influence of UV radiation, current density (j), and supporting electrolyte concentration were evaluated. The results suggest that CBZ is only degraded by DP when UV-C 254nm is used. For HP, the CBZ degradation was observed both when UV-A 365nm or UV-C 254nm were used, which is related to the reactive oxygen species (ROS) formed by the photocatalytic activity (photon-ROS). Neither DP nor HP were able to mineralize CBZ, demonstrating its resistance to photomediated processes. For EO, regardless of the j, there were higher CBZ degradation and mineralization than those observed when using DP and HP. The increase in the supporting electrolyte concentration (Na 2 SO 4 ) did not affect the levels of degradation and mineralization of CBZ. Concerning the PEC, a CBZ mineralization of 52.2% was accomplished. These findings demonstrate that the EO is the main pathway for CBZ mineralization, suggesting an additional effect of the electro-ROS on the photon-ROS and UV-C 254nm . The values of mineralization, kinetics, and half-life show that PEC UV-C 254nm with a j of 15 mA cm -2 was the best setting for the degradation and mineralization of CBZ. However, when the values of specific energy consumption were considered for industrial applications, the use of EO with a j of 3 mA cm -2 and 4 g L -1 of Na 2 SO 2 becomes more attractive. The assessment of by-products formed after this best cost-efficient treatment setting revealed the presence of aromatic and aliphatic compounds from CBZ degradation. Acute phytotoxicity results showed that the presence of sodium sulfate can be a representative factor regarding the toxicity of samples treated in electrochemical systems., (Copyright © 2022 Elsevier Ltd. All rights reserved.)