Discarded yerba mate as a source of cellulose fibers with promising applications for drinking water decontamination

Abstract

In recent years, the focus on environmental sustainability and circular economy has encouraged the reutilization of plant residues. This work aimed at evaluating the potential of discarded yerba mate (DYM) as a source of cellulose fibers suitable to retain low biodegradability emerging contaminants, such as dyes. In addition, we aimed at testing whether the inclusion of silver nanoparticles within those fibers could result in a novel nanocomposite with antimicrobial properties. The raw material (DYM) and the cellulose fibers were characterized according to TAPPI standards. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and tensile strength assessment were conducted. The cellulose content of the DYM was 46.61%. The XRD analysis revealed an increase in cellulose crystallinity index from 19% in the raw material to 60% after cellulose extraction treatments. Cellulose fibers adsorbed about 80–90% of the dyes tested (crystal violet, CV; methylene blue, MB; and safranin, S) at a concentration of 20 mg/L. The adsorption efficiency of the nanocomposite was somewhat lower than that of the fibers alone, while its ability to immobilize Escherichia coli and Staphylococcus aureus cells was higher. Due to these features, the nanocomposite here described could be useful to obtain, in the future, a simple filtering device which could provide safer water at domestic level to periurban settlers with no access to potable water sources.