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This study investigates the effectiveness of various chemical methods, both ultrasound-assisted and non-assisted, for extracting cellulose from banana pseudostem (BPS) waste, comparing the results with commercial pine and eucalyptus cellulose fibers. Delignification treatments with NaOH (25% and 30%) and H2O2 (8%) were evaluated, applied with both conventional and focused sonication. Ultrasound-assisted methods, particularly with NaOH, achieved cellulose percentages as high as 99.5%. X-ray diffraction (XRD) analysis revealed that NaOH treatments significantly increased the cellulose crystallinity index, reaching up to 67.9%, surpassing commercial fibers. Scanning electron microscopy (SEM) results showed that NaOH treatments, especially at 30%, improved fiber morphology and exposure. Thermogravimetric analysis (TGA) indicated that methods using NaOH and focused sonication enhanced the thermal stability of the cellulose. Compared to commercial fibers, some samples obtained with the proposed methods demonstrated higher purity, yield, and thermal stability, highlighting the effectiveness of ultrasound-assisted and NaOH methods. [ABSTRACT FROM AUTHOR]

The simultaneous removal of heavy metals (Fe2+, Zn2+, Ni+2, Cr2+, and Cu2+) using filters built with cheap and easily accessible materials was studied in raw real wastewater generated from an electroplating industry localized in Medellín-Colombia. Various synthesized materials from banana peel waste were used as adsorbents, including powdered dry biomass and functionalized (chemically treated with activating agents) and unfunctionalized biochars, all obtained via hydrothermal and pyrolytic synthesis. For comparison, a commercial activated carbon (CAC) was employed. Significant variations in both structural and surface characteristics were observed among the materials depending on the activating agents utilized. As it was raw wastewater, the coexistence of multiple metals posed challenges in the objective comparison of adsorbents. Thus, the normalization of the maximum adsorption capacity about various parameters (for example, the amount of adsorbent, the specific surface area, the type and abundance of superficial functional groups, or the diameter and volume of the pore) confirmed the complexity of this type of process. In general terms, CAC and unfunctionalized biochar exhibited the highest adsorption capacities (for most metals). This suggests that, when employing banana waste adsorbents for the simultaneous removal of heavy metals in electroplating industry wastewater, the functionalization processes (which involve energy consumption, reagent usage, and waste generation) may not be necessary. [ABSTRACT FROM AUTHOR]

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Hydrodeoxygenation (HDO) kinetics of glycerol into 1,2-propanediol (1,2-PDO) in the liquid phase is studied on Cu-Pd/TiO 2 catalysts. At a stirring speed higher than 480 rpm and an average diameter of the catalyst particles smaller than 89.5 μm, no mass transfer resistance artifacts are observed. The increasing temperature and H 2 concentration promote the glycerol conversion and the selectivity to 1,2-PDO and disfavor the selectivity to acetol. Based on the experimental data, empirical kinetic pseudo-homogeneous expressions are proposed for glycerol disappearance, 1,2-PDO formation, and acetol formation in the catalytic system. Dependence of the disappearance rate of glycerol is closer to 1 with respect to glycerol and nonmeaningful with respect to H 2 . The formation rate of 1,2-PDO is not highly dependent on the initial concentration of glycerol or H 2 , and the formation rate of acetol is directly dependent on glycerol and inversely dependent on H 2 , since it accelerates acetol conversion to 1,2-PDO. The activation energies for glycerol disappearance (77.8 kJ/mol), 1,2-PDO formation (51.2 kJ/mol), and acetol formation (84.6 kJ/mol) evidenced the selective formation of 1,2-PDO in this catalytic system., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

We demonstrated recently that CuPd/TiO 2 -Na bimetallic catalysts synthesized by sequential wet impregnation are active, selective, and stable for the hydrodeoxygenation (HDO) of glycerol into propylene glycol at low H 2 pressure. The present study reports on the nature and distribution of Cu and Pd surface species in CuPd/TiO 2 -Na bimetallic catalysts using different scanning transmission electron microscopy techniques that supply cluster-specific alloying details. In particular, we used atomic-resolution Z -contrast imaging, X-ray energy-dispersive spectroscopy, and electron energy-loss spectroscopy. We also include X-ray photoelectron spectroscopy results. Our analysis shows that the metallic nanoparticles adopt mainly five different structures according to how the Cu and Pd atoms coordinate among themselves: a homogeneous CuPd alloy structure (45-61%), a Cu shell/CuPd core (15-23%), a smaller number of particles formed by Cu on the surface and Pd in the nucleus (10-17%), and there are also nanoparticles formed only by Pd (4-7%) or by Cu (8-13%). We determined that there is a inhomogeneous distribution of Cu and Pd in the bimetallic nanoparticles, with Cu being predominant on the surface (between 76 and 90% of the total area analyzed for each particle). Most bimetallic nanoparticles have sizes below 6 nm, the Pd monometallic nanoparticles are in the 2-4 nm range, whereas the monometallic Cu nanoparticles are larger than 8 nm. Bimetallic nanoparticles with sizes smaller than 6-7 nm are fundamentally made up of Cu 0 -Pd 0 and Cu 1+ -Pd 0 . The nanoparticles with sizes greater than 7 nm consist of Cu 2+ and Cu 2+ -Pd 2+ . Our obtained results also help describe reports about the activation of HDO by Pd-Cu in the absence of H 2 , an effect apparently not observed with other bimetallic systems., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)