Effect of crosslinking of alginate / pva and chitosan / pva, reinforced with cellulose nanoparticles obtained from agave Atrovirens karw

Effect of ternary polymer composites of macroporous adsorbents on adsorption properties for heavy metal removal from aqueous solution

This research is focused on the preparation of macroporous poly(vinyl alcohol) (PVA)/chitosan (CS)/Al₂O₃ adsorbents for removal of residual metal ions from wastewater. The PVA/CS/Al₂O₃ adsorbents were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and energy dispersive X-ray (EDX) techniques to confirm that all compositions were incorporated into the PVA/CS/Al₂O₃ adsorbents without chemical modification. Furthermore, a comparison of the properties of the PVA/CS/Al₂O₃ adsorbents suggested that PVA/CS/0.50Al₂O₃ was the most suitable sample for adsorption study. The adsorption properties of PVA/CS/0.50Al₂O₃ for the removal of metal ions such as Pb²⁺, Cu²⁺, Zn²⁺, and Ni²⁺ in aqueous solution adsorbents in both single and quaternary systems were investigated. The results show that the adsorption selectivity of the PVA/CS/0.50Al₂O₃ adsorbent for these metal ions was provided in the following order: Pb²⁺  > Cu²⁺  > Zn²⁺  > Ni²⁺. The adsorption isotherm was studied by equilibrium data obtained from batch experiments. It was found that the Freundlich isotherm model was suitable for explaining the adsorption process. Adsorption kinetics were studied, which indicated that the adsorption of Pb²⁺, Cu²⁺, and Zn²⁺ followed a pseudo-second-order kinetic model, while the adsorption of Ni²⁺ followed a pseudo-first-order kinetic model. In addition, adsorption-desorption cycles were studied to prove the reusability of PVA/CS/0.50Al₂O₃ adsorbents. The PVA/CS/0.50Al₂O₃ adsorbents were able to be regenerated and reused. In a continuous adsorption process, a column experiment was simulated in laboratory. The results showed that Cu²⁺ was the most selective for a fixed-bed column. Thus, PVA/CS/0.50Al₂O₃ adsorbents could be potential used for toxic metal ion removal from wastewater, in both batch and fixed-bed continuous-flow columns.

Novel eco-friendly electrospun nanomagnetic zinc oxide hybridized PVA/alginate/chitosan nanofibers for enhanced phenol decontamination

In the current study, poly(vinyl alcohol)/alginate/chitosan (PVA/Alg/CS) composite nanofiber was immobilized with six different ratios of nanomagnetic zinc oxide (M-ZnO) (0 wt%, 0.2 wt%, 0.4 wt%, 0.6 wt%, 0.8 wt%, and 1 wt%) via the electrospinning technique. The various fabricated composite (M-6) nanofibers were characterized using Fourier transform infrared (FTIR), X-ray diffractometer (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), atomic force microscope (AFM), thermogravimetric analysis (TGA), mechanical testing machine, and optical contact angle measurement. The fabricated composite nanofibers were applied for the adsorption of phenol from aqueous solutions. The 1.0 wt% M-ZnO/PVA/Alg/CS composite nanofibers were selected as the best phenol adsorbent with removal percentage of 84.22%. The influence of different processing parameter such as contact time, composite nanofiber dosage, pH, initial pollutant concentration, and temperature were examined. Increasing nanofiber dosage and the solution temperature was found to enhance the phenol adsorption onto the prepared nanocomposites. The maximum percentage of phenol removal was achieved at 84.22% after 90 min. Meanwhile, the maximum monolayer adsorption capacity (at pH = 5.0) was estimated to be 10.03 mg g^-1 at 25 °C. Kinetic, isotherm, and thermodynamic studies were designated to proof the endothermic, spontaneous, and thermodynamically nature of the phenol adsorption process. These outcomes indicate the effectiveness of the fabricated M-ZnO/PVA/Alg/CS nanofibers as adsorbent materials for phenol from aqueous solutions.

Characterization and Application of Agave salmiana Cuticle as Bio-Membrane in Low-Temperature Electrolyzer and Fuel Cells

This work describes the application of the Agave salmiana cuticle as a new protonic exchange biological membrane (0.080 ± 0.001 mm thickness). Different chemical, electrochemical and mechanical treatments were evaluated to stimulate the ionic exchange properties of the cuticle. Thermal treatment was adequate for its application in a two-chamber electrolyzer. Under optimal conditions an ionic conductivity value of 10 ± 3 mS cm−1 was obtained; this value is similar to the value achieved using a Nafion membrane. The thermally-activated bio-membrane was also evaluated in a fuel cell, where the highest potential was obtained using methanol and hydrogen (0.46 ± 0.01 V). This result makes the Agave salmiana cuticle a competitive choice to replace the commercial membrane. Its surface morphology and their functional groups were evaluated through scanning electron microscopy (SEM), infrared spectroscopy and impedance spectroscopy. This thermally-treated Agave salmiana cuticle is an ecofriendly alternative to replace Nafion membranes in electrolyzer and fuel cells.