Preparation of polyvinyl alcohol hydrogel modified with environment-friendly pomegranate peel polyphenols: An efficient and regenerative adsorbent for Congo red adsorption
Qihua Zhou, Fei He, Rui Zhao, Yating Xu, Xiongzi Dong, Na Li, Yanzhen Lu, Richuan Rao
Abstract
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.