Pomegranate Peel Polyphenols-incorporated PVA/CMC Hydrogels for High-efficiency Removal of Methylene Blue from Aqueous Solutions

Pomegranate peel, a by-product of pomegranate fruit processing, is frequently discarded in substantial quantities. This agricultural waste contains an exceptionally high concentration of natural polyphenols, distinguished by abundant hydroxyl groups possessing dual hydrogen-bond donating and accepting capabilities. However, research on the fabrication of hydrogels from pomegranate peel polyphenols (PPP) for organic dye removal applications remains limited. In this research, polyvinyl alcohol/sodium carboxymethyl cellulose (PVA/CMC) hydrogel was first synthesized through freeze–thaw cycles, and subsequently soaked in an aqueous PPP solution to fabricate the PVA/CMC/PPP composite hydrogel. We employed Fourier transform infrared spectrometer, scanning electron microscope, X-ray photoelectron spectroscopy, and simultaneous thermal analyzer for hydrogel characterization. Our findings revealed a porous structure in the hydrogel, with PPP immersion enhancing its pore configuration and thermal stability. Swelling tests further revealed that PPP reduced the degree of hydrogel swelling. The combined action of PPP and the PVA/CMC hydrogel augmented the adsorption capacity for methylene blue (MB). The adsorption of MB conformed to the Freundlich isotherm model, and its kinetic behavior aligned more closely with the pseudo-second-order model. The PVA/CMC/PPP hydrogel preserved superior MB removal capability even after five cycling operations. Thus, the formulated PVA/CMC/PPP hydrogel holds promise as a promising candidate for organic dye extraction from water.