Easy to recycle ethylenediamine tetra(methylene phosphonic acid)-modified carboxymethyl cellulose beads for efficient...

Water pollution by heavy metals poses severe threats to ecosystems and human health. While adsorption offers a promising remediation strategy, the practical application of conventional powdered adsorbents is hampered by poor recyclability, handling difficulties, and limited scalability. To address these challenges, we report a novel adsorbent fabricated by crosslinking carboxymethyl cellulose (CMC) with ethylenediamine tetra(methylene phosphonic acid) (EDTMP), a chelating agent with superior heavy metal affinity. This adsorbent (EDT-CMC) exhibits adsorption capacities of 640.4 ± 9.4 mg/g for Pb²⁺ and 401.2 ± 8.2 mg/g for Cd²⁺ at 298 K, representing increases of 95.8 ± 7.9% and 96.6 ± 10.5%, respectively, compared to EDTMP-absent adsorbents. Systematic investigations of adsorption kinetics, isotherms, and thermodynamics were conducted, complemented by comprehensive characterizations (XRD, FT-IR, SEM, XPS). The material demonstrates good tolerance to pH variations and competing ions, along with promising performance in fixed-bed column and recyclability studies, underscoring its potential for practical applications. Mechanistic studies reveal that surface complexation and ion exchange are the primary drivers of metal removal, with electrostatic interactions playing a secondary role, a conclusion further validated by density functional theory (DFT) calculations. This work offers two key advancements, the first being a spherical bead-like architecture that overcomes the recyclability and handling limitations of traditional powdered adsorbents, enabling practical fixed-bed applications, and the second is a comprehensive mechanistic elucidation combining experimental characterizations with DFT calculations, providing molecular-level insights into the adsorption process. Overall, EDT-CMC was expected to be an effective adsorbent to apply in the field of heavy metal removal.