Dynamic adsorption behavior of bio-based adsorbent for multicomponent wastewater

The co-occurrence of chemically diverse contaminants-including organic dyes, solvents, engineered nanoparticles, and nanoplastics in wastewater and receiving water bodies poses a significant challenge to water resource quality and ecosystem health. Understanding and mitigating the fate and transport of such mixed contaminants require process-oriented, quantitative investigations of their interactions with advanced remediation materials. In this study, we developed a bio-based multifunctional adsorbent by functionalizing natural kapok hollow fibers (KT) with polyethyleneimine (PEI) and subsequent immobilization of Fe(III) ions (Fe@PEI@KT). This material provides amine-rich binding sites and coordination-based adsorption mechanisms, enabling simultaneous removal of pollutants with contrasting physicochemical properties: methyl orange (MO), methylene blue (MB), polymethyl methacrylate nanoparticles (PMMA NPs), and methanol (MeOH). Dynamic packed-column experiments were conducted to simulate continuous-flow water treatment conditions. The results demonstrated that surface functionalization substantially improved contaminant removal compared to raw KT. The maximum adsorption capacities of Fe@PEI@KT for MO, MB, PMMA NPs, and MeOH reached 28.75, 20.12, 33.01, and 23.19 mg/g, respectively. A multi-adsorbent column configuration further enhanced performance in mixed-pollutant systems, achieving capacities of 32.95 mg/g (MB), 25.56 mg/g (PMMA NPs), and 35.63 mg/g (MeOH). Kinetic analysis revealed that the adsorption process followed a pseudo-second-order model, indicating chemisorption-dominated behavior. Breakthrough curves were well described by the Thomas and Yoon-Nelson models, providing quantitative parameters for predicting column performance and contaminant transport. These findings highlight the potential of functionalized Fe-PEI-KT fibers as a biodegradable, cost-effective platform for the remediation of complex wastewater. The integrated experimental and modeling approach contributes to understanding the sorption, transport, and attenuation of mixed organic and nanoparticulate contaminants in aqueous systems, with implications for point-of-use treatment and in-situ remediation strategies in contaminated surface water or groundwater environments.