Study of Adsorption of Janus Green B and Methylene Blue on Nanocrystalline Cellulose

Preparation of new green poly (amino amide) based on cellulose nanoparticles for adsorption of Congo red and its adaptive neuro-fuzzy modeling

In this study, a novel green poly(amino amide) nanoparticle based on cellulose nanoparticles (Cell-PAMN) was developed for the efficient adsorption of Congo Red dye. Cellulose nanocrystals obtained from acid hydrolysis of cotton linter were functionalized via Oxa-Michael addition of acrylamide on their surface hydroxyl groups, followed by transamidation with ethylenediamine. The resulting nanoparticles were characterized using FT-IR spectroscopy, SEM, and X-ray diffraction techniques. The as-prepared Cell-PAMN exhibited considerably higher adsorption capacity compared to unmodified cellulose nanoparticles due to the presence of amino and amide functional groups. The adsorption kinetics and the effects of parameters such as contact time and initial dye concentration on the adsorption capacity were investigated. An adaptive Neuro-Fuzzy model was used to study the efficiency of dye removal, accurately predicted the adsorption behavior of Cell-PAMN. The kinetic study results showed that the adsorption process followed a pseudo-second-order kinetic model, with a maximum adsorption capacity of around 40 mg/g. The results demonstrated the potential of the synthesized material for the removal of Congo Red from aqueous solutions, highlighting its applicability in wastewater treatment. This research contributes to the development of sustainable and eco-friendly materials for environmental remediation applications.

Gas and Solution Uptake Properties of Graphene Oxide-Based Composite Materials: Organic vs. Inorganic Cross-Linkers

This study focused on a comparison of the adsorption properties of graphene oxide (GO) and its composites that were prepared via cross-linking with chitosan (CTS) or Al3+ species, respectively. Comparative material characterization was achieved by several complementary methods: SEM, NMR spectroscopy, zeta-potential, dye-based adsorption, and gas adsorption at equilibrium and dynamic conditions. SEM, solids NMR, and zeta-potential results provided supporting evidence for cross-linking between GO and the respective cross-linker units. The zeta-potential of GO composites decreased upon cross-linking due to electrostatic interactions and charge neutralization. Equilibrium and kinetic adsorption profiles of the GO composites with methylene blue (MB) in aqueous media revealed superior uptake over pristine GO. The monolayer adsorption capacity (mg g−1) of MB are listed in descending order for each material: GO–CTS (408.6) > GO–Al (351.4) > GO (267.1). The gas adsorption results showed parallel trends, where the surface area and pore structure of the composites exceeded that for GO due to pillaring effects upon cross-linking. The green strategy reported herein for the preparation of tunable GO-based composites revealed versatile adsorption properties for diverse heterogeneous adsorption processes.

Study of Adsorption Mechanism of Congo Red on Graphene Oxide/PAMAM Nanocomposite

Graphene oxide/poly(amidoamine) (GO/PAMAM) nanocomposite adsorbed high quantities of congo red (CR) anionic dye in 0.1 M NaCl solution, with the maximum adsorption capacity of 198 mg·g⁻¹. The kinetics and thermodynamics of adsorption were investigated to elucidate the effects of pH, temperature, shaking rate, ionic strength, and contact time. Kinetic data were analyzed by the KASRA model and the KASRA, ISO, and pore-diffusion equations. Adsorption adsorption isotherms were studied by the ARIAN model and the Henry, Langmuir, and Temkin equations. It was shown that adsorption sites of GO/PAMAM at experimental conditions were phenolic hydroxyl groups of GO sheets and terminal amine groups of PAMAM dendrimer. Analysis of kinetic data indicated that amine sites were located on the surface, and that hydroxyl sites were placed in the pores of adsorbent. CR molecules interacted with the adsorption sites via hydrogen bonds. The molecules were adsorbed firstly on the amine sites, and then on the internal hydroxyl sites. Adsorption kinetic parameters indicated that the interaction of CR to the –NH₃⁺ sites was the rate-controlling step of adsorption of CR on this site and adsorption activation energies calculated for different parts of this step. On the other hand, kinetic parameters showed that the intraparticle diffusion was the rate-controlling step during the interaction of CR molecules to –OH sites and activation energy of this step was not calculable. Finally, the used GO/PAMAM was completely regenerated by using ethylenediamine.

Bioconjugated graphene oxide hydrogel as an effective adsorbent for cationic dyes removal

In this study, graphene oxide - cellulose nanowhiskers nanocomposite hydrogel was easily synthesized through covalent functionalization of cellulose nanowhiskers with graphene oxide via a facile approach. The nitrene chemistry applied for covalent functionalization of graphene oxide sheets. The surface morphology and chemical structure of the nanocomposite hydrogel were characterized by FTIR, TGA, Raman, XRD, elemental analysis and SEM. The UV/Visible absorption spectrum revealed that the obtained porous nanocomposite hydrogel can efficiently remove cationic dyes such as methylene blue (MB) and Rhodamine B (RhB) from wastewater with high absorption power. The adsorption process showed that 100% of MB and 90% of RhB have been removed and the equilibrium state has been reached in 15min for low concentration solutions in accordance with the pseudo-second-order model. Moreover, the sample exhibited stable performance after being used several times. High adsorption capacity and easy recovery are the efficient factors making these materials as good adsorbent for water pollutants and wastewater treatment.