Synthesis of Sulfonated Copolyimides by Thermal Imidization for Efficient Lead Ion Adsorption from Aqueous Media

Thermally stable, high performance sulfonated copolyimide adsorbents [OBM (ODPA+BDSA·TEA+MDA) and FBM (6FDA+BDSA·TEA+MDA)] having excellent adsorption ability were prepared via a two-step thermal imidization reaction. By the introduction of hydrophilic sulfonic acid groups into the polyimide backbone, the material's hydrophilicity was improved. The anionic sulfonate group bears strong affinity toward heavy metal ions. Improvement in polymer hydrophilicity enhances the heavy metal ion adsorption capacity due to feasible access to adsorption sites. Atomic absorption spectroscopy (AAS) was employed for heavy metal ion adsorption studies. In addition, quantum chemistry calculations using Molecular Operating Environment (MOE) software were performed, to scrutinize the experimental results for molecular surface studies. A good correlation was observed between computational and experimental findings. OBM was demonstrated to be more effective for Pb(II) removal from aqueous media with a higher qe and percent removal as compared to FBM. The synthesized sulfonated copolyimides are potential adsorbents for heavy metal ions.