Preparation of polyvinyl alcohol hydrogel modified with environment-friendly pomegranate peel polyphenols: An efficient and regenerative adsorbent for Congo red adsorption

This study reports the fabrication of polyvinyl alcohol (PVA) based hydrogel with pomegranate peel polyphenols (PPP) via the freezing-thawing cycles method, employed as a cost-effective and efficient Congo Red (CR) adsorbent. Numerous techniques, including TGA, SEM, FTIR, XRD, DLS, BET, together with universal stretching machine, were employed to confirm the successful synthesis of PVA/PPP hydrogels with porous structures. When compared to pure PVA hydrogel, the PVA/PPP hydrogels showed greater adsorption capabilities for CR. The kinetic data coincided with pseudo-second-order modeling (R2 = 0.9927). Freundlich isotherm modeling was highly-conformed through adsorption (R2 = 0.9985). CR adsorption appeared to be exothermic and spontaneous, according to the thermodynamic study. Moreover, following five consecutive runs, adsorption effectiveness for PVA/PPP hydrogels remained above 88%, demonstrating their exceptional reusability. The mechanisms analysis revealed that the CR adsorption was facilitated by electrostatic attraction, hydrogen bonding, together with π-π stacking interplays.