Supercritical CO2 extraction of V. vinifera leaves: influence of cosolvents and particle size on removal kinetics and selectivity to target compounds

Leaves from Vitis vinifera L. contain potential bioactive compounds, namely: long chain aliphatic alcohols (e.g., 1-hexacosanol, 1-octacosanol and 1-triacontanol), α-tocopherol, β-sitosterol, and the triterpenes β-amyrin and lupeol. Supercritical fluid extraction (SFE) runs were measured at lab scale using: crushed and ground biomass; pure CO2 at 300 bar and 40−80 °C; and CO2 modified with 5 and 10 wt.% of ethanol or ethyl acetate. Total SFE yields ranged from 1.86 to 7.52 wt.%. The broken plus intact cells model (BICM), provided a good fitting of the SFE curves with 4.06 % error for total yield and 1.98–5.49 % for the individual yields of the said compounds. The BICM results revealed that the SFE is limited by intraparticle diffusion. Remarkable experimental and calculated selectivities were obtained for triterpenes (lupeol and β-amyrin), starting with a score of 1.7 and increasing along time to 10−100.publishe

Applications of electrified dust and dust devil electrodynamics to Martian atmospheric electricity

Atmospheric transport and suspension of dust frequently brings electrification, which may be substantial. Electric fields of 10 kVm-1 to 100 kVm-1 have been observed at the surface beneath suspended dust in the terrestrial atmosphere, and some electrification has been observed to persist in dust at levels to 5 km, as well as in volcanic plumes. The interaction between individual particles which causes the electrification is incompletely understood, and multiple processes are thought to be acting. A variation in particle charge with particle size, and the effect of gravitational separation explains to, some extent, the charge structures observed in terrestrial dust storms. More extensive flow-based modelling demonstrates that bulk electric fields in excess of 10 kV m-1 can be obtained rapidly (in less than 10 s) from rotating dust systems (dust devils) and that terrestrial breakdown fields can be obtained. Modelled profiles of electrical conductivity in the Martian atmosphere suggest the possibility of dust electrification, and dust devils have been suggested as a mechanism of charge separation able to maintain current flow between one region of the atmosphere and another, through a global circuit. Fundamental new understanding of Martian atmospheric electricity will result from the ExoMars mission, which carries the DREAMS (Dust characterization, Risk Assessment, and Environment Analyser on the Martian Surface)-MicroARES (Atmospheric Radiation and Electricity Sensor) instrumentation to Mars in 2016 for the first in situ measurements