Bio-pillared graphene oxide strata-scaffolds for targeted removal of ionic organic dyes: thermodynamic, kinetic, and isotherm modeling insights

Abstract Developing sustainable, high-capacity adsorbents that combine structural stability, recyclability, and predictive modeling remains a critical challenge in wastewater remediation. To address this challenge, this study developed a three-dimensional “Strata-Scaffold” comprising sodium alginate, graphene oxide (GO), and carboxylated nanocellulose (c-NC) extracted from Phoenix dactylifera fibers via a green oxidation route. Structural characterization using TEM, SEM, XRD, and SAED confirmed the integration and reorganization of the GO/c-NC phases within the three-dimensional scaffold, supporting the proposed reinforcing and spacer role of c-NC. The resulting scaffold exhibited a hierarchical porous structure with a BET surface area of 1092 m²/g. ATR-FTIR and Raman analyses further revealed functional groups and structural interactions relevant to dye adsorption, including electrostatic interactions, hydrogen bonding, and π–π interactions. These structural features were reflected in the adsorption performance, with an experimentally observed methylene blue (MB) equilibrium adsorption capacity ( q ₑ) of approximately 655 mg/g at an initial MB concentration of 700 mg/L. In binary systems, the scaffold also showed preferential adsorption of MB over methyl orange (MO). Nonlinear regression analysis identified the Sips isotherm and Avrami kinetic model as the best-fitting models based on multiple error criteria (SSE, RMSE, ARE, χ², and R²). The Sips model yielded a saturation capacity ( Q ₛ) of 1422.2 mg/g, while thermodynamic analysis indicated spontaneous and exothermic adsorption. Furthermore, the scaffold retained 86.5% of its initial adsorption capacity after five regeneration cycles, demonstrating good reusability.