Mass transfer parameters for the aqueous extraction of yerba mate (Ilex paraguariensis) leaf residue

The industrial processing of yerba mate (Ilex paraguariensis) generates significant quantities of a fine leaf residue that is currently underutilized. This study investigated the kinetic and equilibrium parameters of the aqueous extraction of this by-product at three temperatures (35, 60, and 85 °C) to assess its potential for valorization. All extractions were performed using water as the solvent. The residue exhibited a low granulometry (mean particle size: 317.5 µm) and a composition comparable to commercial yerba mate leaves, with a soluble solids content of 40–45%. Extraction kinetics revealed that equilibrium was reached in less than 20 min at all tested temperatures, with higher temperatures enhancing the release of soluble compounds during the initial phase of extraction. Equilibrium data were well described by a linear model, with no statistically significant differences observed between the equilibrium lines at 60 and 85 °C. Under gravity filtration, the mean retention index was 7.58 g of extract per g of inert solids in the raffinate. However, the application of pressure during filtration significantly reduced this value. Furthermore, pressure filtration produced a greater deviation from ideality in the equilibrium relationship compared to gravity filtration, highlighting potential trade-offs in process design. The results can be applied to the design of multistage extraction systems to enhance cost-effectiveness in industrial operations.