Studies on remediation of neutral red using water insoluble β-cyclodextrin (β-CD) polymers in aqueous solution

The increasing global contamination of dyes in natural waters has highlighted the need for versatile and effective cleanup methods. In this study, water-insoluble beta-Cyclodextrin (beta-CD) polymers, including CA/beta-CD, MA/beta-CD, and TA/beta-CD, were synthesized by cross-linking beta-cyclodextrin with three different organic acids: citric acid (CA), tartaric acid (TA), and malic acid (MA). This synthesis aimed to create polymers with distinct properties by incorporating these acids into the beta-Cyclodextrin framework. The resulting polymers were characterized using various advanced analytical techniques, such as Fourier transform infrared spectroscopy, scanning electron microscopy, and UV-visible (UV-Vis) spectrophotometry. The synthesized polymers were then used to adsorb neutral red dye from aqueous solutions. The study explored various conditions for adsorption, including pH, adsorbent mass, dye concentration, temperature, and contact time, as well as adsorption isotherms, kinetics, and thermodynamics. Among the polymers, CA/beta-CD, with its higher content of carboxyl groups, showed the highest efficiency in adsorbing neutral red dye under all tested conditions. The CA/beta-CD adsorbent achieved 92% removal efficiency, with the dye being attracted to the negatively charged carboxyl ions through electrostatic forces, effectively removing it from water. These findings suggest that water-insoluble cyclodextrin-based polymers could be cost-effective adsorbents for removing dye from aqueous solutions.