Posidonia fibers grafted with β-cyclodextrin for the adsorption of paracetamol

Pharmaceutical and personal care products, such as paracetamol, are emerging contaminants frequently detected in aquatic environments, raising concerns due to their persistence and resistance to conventional wastewater treatment methods. This study reports the development of a sustainable bifunctional bioadsorbent by grafting β-cyclodextrin (β-CD) onto fibers of Posidonia oceanica, a Mediterranean seagrass rich in lignocellulosic components. The grafting was achieved using citric acid as a green, non-toxic crosslinker and potassium dihydrogen phosphate as a catalyst, yielding the Pos-βCD material. The most suitable CD type for being grafted was selected from the determination to the binding affinities of paracetamol to α-, β-, and γ-CD. The latter were evaluated in solution by ¹H NMR experiments. β-CD formed the most stable 1:1 inclusion complex. The Pos-βCD materials were synthesized at different grafting ratios and thoroughly characterized by IR, ζ-potential, TGA, BET, optical microscopy, SEM, and light scattering. IR spectroscopy confirmed the formation of ester bonds and successful surface modification. Morphological analyses by BET, optical microscopy, and SEM showed the preservation of the fiber structure after grafting along with improved thermal stability disclosed by TGA. Zeta potential measurements showed that the Pos-βCD had a negative charge over the whole pH range. The successful grafting of β-CD onto pure cellulose and pure lignin showed that β-CD was grafted to both these two components of Pos. Adsorption of Paracetamol showed the potential of Pos-βCD bioadsorbents for the removal of pharmaceutical substances from contaminated water, providing an environmentally friendly and cost-effective alternative to conventional adsorbents. This work also highlights the valorization of marine biomass waste within a circular economy framework.