Alginate and alginate-chitosan hydrogels for wastewater remediation: effect of composted biowaste-derivative addition

The rising utilization of renewable and residual biomasses for environmental preservation and remediation are important objectives to be pursued to minimize the environmental impact of human activities [1]. In this perspective, biowaste-containing hydrogels are herein proposed as aqueous pollutant adsorbents. We prepared hydrogels by crosslinking sodium alginate (derived from brown algae) with Ca2+ or chitosan (derived from crustacean exoskeleton), by adding soluble biowaste-derived substances isolated from green compost (BBS-GC). Alginate, chitosan and BBS-GC (that bear similarities with humic-like substances) are sustainable, non-toxic and environmental-friendly reactants, bringing a multiplicity of different functional groups, able to act as sequestrating agents for the remediation of contaminated wastewaters [1,2]. Thanks to the multi-analytical approach adopted for the physicochemical characterization of the materials (i.e. scanning electron microscopy, thermogravimetric analysis, water uptake/swelling measurements, Fourier transformed infrared spectroscopy, rheological measures), it was possible to define some relationships among structural, morphological and rheological features of the gels together with their adsorbing properties, evaluated in the removal of different dyes, which represent typical polluting substances discharged downstream of textile industries [3]. The enhanced performances registered for the BBS-GC-containing gels in comparison with reference ones, suggest their potential use as sustainable tools for wastewater treatments.