Browsing by Author "Núñez, Gonzalo A."

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    Equilibrium partition of rapeseed oil between supercritical CO2 and prepressed rapeseed
    (2015) Urrego, Freddy A.; Núñez, Gonzalo A.; Donaire, Yazmin D.; Del Valle Lladser, José Manuel
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    Supercritical CO2 extraction of pelletized oilseeds : Representation using a linear driving force model with a nonlinear sorption isotherm
    (2021) Toledo Cayuleo, Felipe Rodrigo; Del Valle Lladser, Jose Manuel; Opazo, Álvaro P.; Núñez, Gonzalo A.
    This work develops a general, predictive model for the SuperCritical (SC) CO2 extraction of pelletized oilseeds. Cumulative SC-CO2 extraction curves of small (S, dp = 2.5 mm) and large (L, dp = 4.0 mm) cylindrical evening primrose seed pellets were modeled simultaneously using a Linear Driving Force (LDF) approximation modified to consider the nonlinear oil partition between CO2 and the substrate and extrapolated using the actual solubility of oil in CO2 at extraction conditions (40 °C and 45 MPa). Model best-fitting parameter was a single interparticle porosity (εp) of pellets considering equilibrium conditions after static extraction, and mass transfer kinetics during dynamic extraction. The adaptation of general model to bisized mixtures containing 25–75% S-pellets, predicted experimental results better than a monosized version (same Sauter mean diameters) because of the negative impact on overall cumulative extraction curves of slow-extracting L-pellets. Finally, a simplified version of the general model was developed that neglected the intraparticle porosity (εp = 0) and used a microstructural factor () in the general model as the best-fitting parameter. This simplified model saved 33% of computational time at the expense of overestimating extraction rates, particularly at the beginning of the diffusion-controlled period, which diminished as εp decreased and FM increased.
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    Thermodynamic properties of CO2 during controlled decompression of supercritical extraction vessels
    (2015) Richter, Eduardo A.; Del Valle Lladser, José Manuel; Núñez, Gonzalo A.
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    Use of Hansen solubility parameters to select supercritical carbon dioxide cosolvents for improved extraction selectivity: Case study on green tea decaffeination
    (2025) del Valle Lladser, José Manuel; Cuellar Alvarez, Laura María; Canales Muñoz, Roberto Ivan; de la Fuente, Juan C.; Núñez, Gonzalo A.
    This study explores the selective decaffeination of green tea using supercritical (SC) CO 2 modified with ethanol and/or water as cosolvents based on experimental data in eight manuscripts in literature. We analyzed the solubility trends of caffeine (data from three literature sources) and epigallocatechin-3-gallate (EGCg) (data from a single source) using the Hansen solubility parameter (HSP) model to evaluate the solute-solvent interactions through the distance parameter R. We identified that the highest selectivity (favoring caffeine removal and EGCg retention) occurred at 70 ◦ extraction C and ≥25 MPa using pure CO 2 and hypothesized that the addition of water facilitated substrate swelling and improved inner mass transfer. Ethanol showed limited benefits at higher pressures. Data for operational solubility were more in line with actual solubility than apparent solubility, although both were still dependent on substrate-solute interactions. Solubility measurements revealed a significant scatter in the data, particularly for caffeine in water- and/or ethanol-modified CO 2 , underscoring the need for better experimentally derived data. Despite these challenges, HSP-based approaches effectively identified conditions that maximized selective decaffeination while preserving EGCg content.