Magnetic protein hydrogel for dye and heavy metal adsorption

M. D'ORSO; P. MENDOZA ZÉLIS; C. MEIORIN; J.F. MARTUCCI

Congreso; Congresso Brasileiro Interdisciplinar em Ciência e Tecnologia; 2022

Water pollution is a problem that afflicts people throughout the world. Adsorption is the most widely used method to remove contaminants from water. This paper proposes an eco-friendly protein hydrogel as a potential adsorbent for water purification.Protein hydrogels are widely studied due to their high adsorbent capacity. In this study, we developed magnetic protein hydrogels based on gelatin and phycobiliproteins (PBPs) obtained from lyophilized commercial Spirulina Platensis (SP) powder. The incorporation of PBPs was motivated by their chelating characteristics, and the incorporation of magnetic particles (Fe3O4/γFe2O3) will allow the creation of magnetic biocompounds that can may be afterwards removed from the medium. Oxidized sodium alginate (AO) was used as a crosslinking agent, providing dimensional stability to hydrogels in aqueous environments. Magnetic nanoparticles (magnetite, NPs) were prepared from iron salts through chemical coprecipitation. To obtain the hydrogels, aqueous protein solutions at 20% w/V were prepared, using bovine gelatin (Ge) and SP (0-1.5% w/V), and were cross-linked with AO (5% w/w protein); glycerol was added to the protein system (30% w/w protein) as a plasticizer. The NPs were incorporated (1% w/w protein) and the system was homogenized by sonication cycles.The hydrogels were stabilized for 48h in a refrigerator (4°C) and then lyophilized to characterize them by DSC, TGA, XRD and VSM to assess their thermal and magnetic behavior. A superparamagnetic behavior was observed in all the gels with NPs. The swelling capacity of the hydrogels in water was analyzed. The highest rate of absorption of the hydrogels occurs during the first 2h of swelling, when they reach 40% of the maximum capacity. A steady state is reached after 24h. Similar results were observed for dextrose-crosslinked, gelatin-based hydrogels. The formulation with SP and NPs produced the highest absorption capacity. After the first swelling cycle, the gels were lyophilized and the mass loss was evaluated gravimetrically. The results showed a mass loss at 24h of about 25% without significant differences due to the presence of SP or NPs. By assessing the absorption capacity of methyl orange as a model dye, it was observed that it only depends on the water absorption capacity of the hydrogel.