Direct extraction of uranium from yellow cake and ore matrices using supercritical carbon dioxide

The study demonstrates the accomplishment of single step, direct supercritical fluid carbon dioxide (SC CO2) dissolution and extraction of uranium from crude matrices viz. yellow cakes (>90%) and rock phosphate ores (70%) employing adducts of trialkyl phosphates and nitric acid, thus avoiding free acid usage and eliminating number of process steps. Rock phosphate ore was made amenable for supercritical fluid extraction (SFE) system by unique strategy of pyrohydrolytic removal of fluorine. Pressure and temperature conditions, which were found to influence uranium extraction efficiency, were optimized at 150 atm. and 323 K. Two milliliter of adduct amount was found to be adequate. Adducts of branched alkyl phosphate, tri-isoamyl phosphate and tri-ethyl hexyl phosphate (TEHP), yield better purity in comparision to straight chain tri-butyl phosphate (TBP).

Efficacy of Neem Kernel Bioactives Extracted using Supercritical Fluid Carbon Dioxide on Selected Dermatophytes and Foodborne Pathogens

Neem seed kernel was subjected to supercritical fluid carbon dioxide (SCF) process and evaluated for the inhibition of selected dermatophytes such as Candida albicans, Candida tropicalis, Candida parapsilosis, Trichophyton rubrum, Trichophyton mentagrophytes. The extraction was carried out by SCF-CO2 at 300 bar 50 °C with and without entrainer (30 % methanol and acidified methanol). Results showed that the inhibition of the growth of all the dermatophytes is maximum in the extract obtained at 300 bar 50 °C with methanol (SCF-Me) followed by 300 bar 50 °C without methanol (SCF). The acidified SCF (SCF-MeA) extract did not show any remarkable inhibition. Of the dermatophytes, SCF-Me showed the inhibition against Candida parapsilosis of 18.46±0.25 mm compared to Candida albicans 16±0.26 mm, whereas the methanol control exhibited 10±0.3 mm inhibition. Out of the two fungal organisms, SCFMe inhibited the growth of Trichophyton rubrum and Trichophyton mentagrophytes at 21.53±0.23 mm and 18.1±0.1 mm respectively. The extracts were also evaluated for its inhibition against the foodborne pathogens (bacteria, fungi, and yeast). The SCF-Me extract showed maximum inhibition against Pseudomonus aeroginosa (27.26±0.25) compared to Bacillus subtilis (24.36±0.35) at the concentration of 70mg. In fungus, Aspergillus ochraceus (16.7±0.60) was maximum when compared to Aspergillus niger (15.2±0.43) and yeast exhibited the inhibition of 15.93±0.20 at the concentration of 80mg. The dermatophytic and antimicrobial activity of the SCF-Me extract is due to the presence of higher amount of triterpenoinds such as Azadirachtin (50.7 %), 6-deacetyl nimbin (0.14 %), Nimbin (0.08 %), Salannin (1.83 %) and Epoxy azadiradione (1.58 %) which were confirmed by liquid chromatography and mass spectroscopy (LC-MS).

Selective Extraction of ω-3 Fatty Acids from Nannochloropsis sp. Using Supercritical CO2 Extraction

In this article, microalgae Nannochloropsis sp. was used for fatty acid (FA) extraction, using a supercritical fluid-carbon dioxide (SF-CO2) extraction method. This study investigated the influence of different pre-treatment conditions by varying the grinding speed (200–600 rpm), pre-treatment time (2.5–10 min), and mixing ratio of diatomaceous earth (DE) and Nannochloropsis sp. biomass (0.5–2.0 DE/biomass) on FAs extraction. In addition, the effect of different operating conditions, such as pressure (100–550 bar), temperature (50–75 °C), and CO2 flow rate (7.24 and 14.48 g/min) on eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) recovery, was analyzed. Experimental data evidenced that, keeping constant the extraction conditions, the pre-treatment step enhanced the FAs extraction yield up to 3.4 fold, thereby the maximum extracted amount of FAs (61.19 mg/g) was attained with the pre-treatment with a ratio of DE/biomass of 1 at 600 rpm for 5 min. Moreover, by increasing both SF-CO2 pressure and temperature, the selectivity towards EPA was enhanced, while intermediate pressure and lower pressure promoted DHA recovery. The highest amount of extracted EPA, i.e., 5.69 mg/g, corresponding to 15.59%, was obtained at 75 °C and 550 bar with a CO2 flow rate of 14.48 g/min, while the maximum amount of extracted DHA, i.e., ~0.12 mg/g, equal to 79.63%, was registered at 50 °C and 400 bar with a CO2 flow rate of 14.48 g/min. Moreover, the increased CO2 flow rate from 7.24 to 14.48 g/min enhanced both EPA and DHA recovery.