Unveiling the potential of a functionalized pyrrole-based polymer for efficient cadmium ion removal from wastewater: synthesis, characterization, and performance evaluation

Cadmium ion Cd2+ contamination is a major environmental issue caused by industry. Polyarylidene N-hexane pyrrole (PAPh) and crosslinked polyarylidene N-phenyl pyrrole (PAPD) were prepared from the previously synthesized polymer (polyarylidene ketone (PAK)) by using the advantage of repeating carbonyl groups at the 1,4 position and reacting it with hexylamine and P-phenylenediamine via the Paal–Knorr reaction. Various methods were used to characterize polymers, such as FT-IR spectroscopy, X-ray diffraction (XRD), thermogravimetry analysis (TGA), UV–visible spectroscopy, scanning electron microscope (SEM), zeta potential, and surface area measurements (BET), revealing successful fabrication, good thermostability, and well-defined microporous structures useful for Cd2+ adsorption. Optimal adsorption capacities of 55.8 mg g−1 for PAPh and 86.95 mg g−1 for PAPD indicate a significant enhancement in Cd2+ adsorption via their microporous structures, Cd2+ adsorption was also investigated in terms of contact time, initial concentration, and pH. A total input concentration of 30 ppm Cd ions, may yield an 84.3% removal rate for PAPh and an 89.2% removal rate for PAPD. The experimental results were well-fit by many models, including pseudo-second-order kinetics (PSO), Freundlich isotherms, intraparticle diffusion, and Langmuir. The varying adsorption performances of the two polymers studied, (PAPh) and (PAPD), were found to be derived from their respective chemical structures, which include various functional groups, according to studies conducted on Cd2+ in an aqueous solution. Cd2+ adsorption on polymers was considered physisorption; π–cation interactions and surface complexation played significant roles in adsorption. The PAP polymers may be considered promising substitutes and innovative adsorbents to remove Cd2+ ions from a water solution.