Physicochemical study of a bio-based adsorbent made from grape marc

•Biologically oxidized grape marc hydrogel as eco-friendly adsorbent.•Effective color removal from wastewater with grape marc based biopolymer.•Morphological changes in a grape marc biocomposite during dye adsorption.•Grape marc bio-based composite follows Freundlich isotherm in dye removal.

In the last few years bio-oxidized grape marc (formulated by encapsulation in calcium alginate beads) has been proposed as an eco-friendly adsorbent for wastewater treatment. However, the physicochemical properties of the bioadsorbent have not yet been reported. This study analyzed the stability of the bio-based adsorbent before and after adsorption of dye compounds from winery wastewater. Minor morphological changes in the adsorbent were observed after it was used to treat the wastewater. The physicochemical properties of the bioadsorbent at equilibrium were also evaluated. The process of adsorption onto the heterogeneous surface of the bio-based adsorbent was best described by the Freundlich isotherm, and the adsorption process was physically controlled (E = 0.61 kJ/mol).