Novel sustainable Schiff Base covalent organic polymers from optimized dialdehyde carboxymethyl cellulose and 4,4′-oxydianiline via dual synthesis method for Pb (II) removal

In this study, sustainable Schiff base COP were synthesized from oxidized carboxymethyl cellulose and 4,4′-oxydianiline via two distinct synthetic routes to remove heavy metals. First, oxidation of CMC was optimized to maximize the aldehyde functional group, facilitating efficient Schiff base formation. Then, the synthesis of the Schiff base imine was conducted employing two distinct methodologies. In Method I, paraformaldehyde was used to mediate a controlled imine condensation at 120 ℃. In Method II, the Schiff base reaction was carried out for one day of reflux before being subjected at 80°C without the addition of PFA. Both COP were analyzed through FTIR, FE-SEM, XRD, BET, and zeta potential measurements, confirming functionalization and morphological differences. COPs were assessed for their effectiveness in eliminating Pb(II) from water under optimized conditions. The adsorption performance was evaluated using nonlinear kinetic and isotherm models as well as thermodynamic studies. Thermodynamic studies showed that adsorption is exothermic for both COPs. Method II COP was more beneficial and showed q e max ∼67 mg g −1 , while Method I COP was 33.5. There were significant differences in the adsorption behavior depending on the synthesis route. The findings highlight the potential of dual-method Schiff base-modified biopolymers as efficient adsorbents for heavy metal remediation.