The demand for clean water has become a worldwide problem because of the pollutants' excessive and inappropriate use. In this regard, a new hydrogel nanocomposite adsorbent was fabricated from xanthan gum and graphene oxide via free radical polymerization for methylene blue (MB) dye removal. The physicochemical properties of the synthesized hydrogel nanocomposite were evaluated using scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), Fourier transform infrared (FTIR), and thermogravimetric analysis (TGA). The properties of the bare hydrogel and the adsorption of MB dye in an aqueous solution were enhanced by adding graphene oxide to the hydrogel matrix. The batch adsorption experiment revealed a maximum adsorption capacity of 1008 mg/g for the prepared hydrogel nanocomposite, using 250 mg/L of MB dye at pH 7 over the course of an hour. The findings of the adsorption kinetics model suggested that the order of the adsorption process of the prepared hydrogel nanocomposite is fitted well with pseudo-second-order kinetics. The regeneration study demonstrated excellent recyclability for the synthesized nanocomposite across five successive reusable cycles. The findings from the point of zero charge (pzc) and FTIR investigations indicate that electrostatic attraction is the primary force between the adsorbent and the dye molecules.

The conversion of agricultural waste into high-value nanoparticles presents a sustainable approach to waste management and the production of bio-based goods. This work effectively collected cellulose nanofibers and cellulose nanocrystals from agricultural leftovers using chemical methods. The resulting nanocelluloses were characterised through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to ascertain their chemical structure, crystallinity, morphology, and thermal stability. XRD revealed a crystalline cellulose I structure for cellulose nanofibers and a crystalline cellulose Iβ structure for nanocrystals. The former exhibited a crystallinity index of 74.3 %, surpassing the cellulose nanocrystals index of 66.8 %. Cellulose nanocrystals exhibited reduced thermal stability compared to cellulose nanofibers throughout the analysed TGA range. The zeta potential (ζ) values were found to be -18.2 ± 085 mV for cellulose nanofibers and - 12.80 ± 1.91 mV for cellulose nanocrystals. The kinetic activation energy for cellulose nanofibers exceeds that of cellulose nanocrystals, as determined by the Broido and Coats-Redfern models. The research illustrates the viability of agricultural waste as a plentiful, renewable feedstock for the production of cellulose nanomaterials, which possess properties appropriate for use in biocomposites, films, hydrogels, and advanced functional materials, thereby aiding the advancement of sustainable circular bioeconomies.

Conductive hydrogels (CHs) are widely studied for flexible sensors in hydrogen energy applications due to their excellent conductivity, flexibility, and detection capabilities. However, most CH-based sensors suffer from low sensitivity, poor stability, and weak tensile strength. Furthermore, they often rely on non-biodegradable synthetic polymers, limiting their practical applications. This study utilizes Ag@rGO hydrogel nanocomposite blended with cellulose as an electrochemical sensor for hydrogen gas detection at ambient temperature, considering its higher catalytic activity, favorable surface area, and conductivity to overcome existing limitations. Nonetheless, given that cellulose serves as a binding agent in the formation of hydrogel, its characteristics like biodegradability, compatibility, and the ability to react to various chemical systems are transferred to the surface of the Ag@rGO hydrogel-based sensor. The measured sensitivity for hydrogen detection of the Ag@rGO nanocomposite and Ag@rGO hydrogel nanocomposite was found to be 188.38 and 329.85 µA.M, respectively. The limits of detection were recorded at 0.92 and 0.63 µM, with response/recovery times of 0.6/0.9 s and 0.3/0.6 s. The proposed electrochemical sensor offers an exciting approach for the detection of hydrogen gas. The sensor was fabricated and its microstructure characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Its electrochemical performance, sensing efficiency, interference resistance, and stability were assessed using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS). This study explores the use of biopolymer-blended conductive hydrogels as innovative channel materials for developing gas sensors that are both highly flexible and sensitive.

This study investigates the effectiveness of a novel metal oxide-based hydrogel nanocomposite in degrading synthetic dyes in the presence of UV light. The nanocomposite is synthesized through the insertion of metal oxide nanoparticles (NPs) into a hydrogel matrix, optimizing the material's photocatalytic properties. The successful synthesis of the hydrogel nanocomposite was verified using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). Through determination of XRD parameters, a successful synthesis of Co-CuO HNCs with an average crystallite size of 10.21 nm was confirmed. SEM images showed that after incorporating spherical-shaped Co-CuO NPs into the hydrogel matrix, the surface of the final composite became rough and fragmented with a surface area of 4.06 m²/g. Optical studies showed that the bandgap was reduced as Co-CuO NPs were incorporated into the hydrogel matrix. Photocatalytic degradation experiments were conducted using methylene blue (MB) to assess the hydrogel nanocomposite's efficiency. The results demonstrate a significant enhancement in degradation rates compared to traditional photocatalysts, due to the synergistic effects of the metal NPs and the hydrogel network. Within 120 min, the photocatalytic removal efficiency of MB reached 96% at a pH of 10 using 100 mg of the catalyst. The photocatalytic degradation process followed a pseudo first-order kinetics with a rate constant of 0.0183 min⁻¹. Moreover, scavenger studies showed that ∙OH radicals were major species responsible for the photocatalytic degradation process. The study highlighted the potential of metal-based hydrogel nanocomposites as efficient and sustainable photocatalysts for environmental remediation, offering a promising solution for the treatment of dye-contaminated wastewater. Future research will focus on optimizing the performance of the nanocomposite and exploring its practical applications in large-scale water treatment processes.

In this study, we are interested in preparing novel hydrogel and hydrogel nanocomposite-based adsorbents for removing methylene blue (MB) dye based on grafted locust bean gum (LBG). LBG hydrogel and hydrogel nanocomposite were synthesized using a radical polymerization technique in the absence and presence of TiO₂ with LBG-cl-(acrylic acid (AA)-co-acrylamide (AAm)). Various analytical instruments Fourier transform infrared (FTIR), X-Ray diffraction (XRD), Scanning electron microscopy (SEM), and High-resolution transmission electron microscopy (HRTEM) were used to elucidate the chemical structure and surface morphology of the prepared samples. Using a batch adsorption experiment, the Langmuir isotherm model showed that LBG-cl-p(AA-co-AAm) hydrogel had a maximum adsorption capacity of 1540.9 mg/g and LBG-cl-(AA-co-AAm)/TiO₂ hydrogel nanocomposites had a maximum adsorption capacity of 1273.4 mg/g at neutral pH. The thermodynamic data demonstrated that MB dye was removed via spontaneous adsorption. Furthermore, the regeneration study showed good recyclability for the obtained hydrogel nanocomposites through six consecutive reusable cycles. Therefore, the hydrogel nanocomposites are an effective adsorbent for the removal of MB dye from aqueous solutions.