Phase equilibrium diagrams for the system water, inert and solutes from mate (Ilex paraguariensis) leaves at constant temperature and cyclic pressurization

Experimental equilibrium curves for a three-component mixture of water, insoluble and soluble matter from dry leaves of mate at 17 °C, 32 °C and 47 °C were obtained. They were built from equilibrium data of solute mass fractions (on an inert-free basis) at solid to solvent mass ratios of 1.5:30, 3:30, 4.5:30 and 6:30. The equilibrium concentrations in the leached solution were tuned on a large set of kinetic data (≥55) of solute in the liquid phase by involving a first-order solid-liquid extraction model. The kinetic experiments of solute removal were carried out in an isothermal batch extractor under a frequency of pressurization of 1:600 cycles per second (300 s at 91.4 kPa + 300 s at 182.8 or 365.6 kPa per cycle) for 25,200 s. The equilibrium mass fractions of solute in the slurry were calculated by a mass balance for the mate solubles based on the known composition of the starting solid in terms of total solute and inert. A constant mass ratio of retained solvent to inert close to 4.2 was experimentally obtained by draining under gravity the bed of solids taken to leaching. The results are presented in McCabe-Thiele and Ponchon-Savarit diagrams, and revealed the significant influences of solid to solvent ratio and leaching temperature on solute equilibrium concentrations at a high probability level (p ≤ 0.05). The non-vertical tie lines in the rectangular diagram of Ponchon-Savarit evidenced that solute is adsorbed by the insoluble solid, which means that solute distributes unevenly between the liquid and solid phases at equilibrium (i.e.; yAe≠xAe).