SC-CO2 Treatment Research Articles

Preparing hot-dip galvanized steel surfaces for painting or powder coating: a primer

Supercritical carbon dioxide (scCO2) treatment was employed for rapid formation of a zinc patina layer on hot dip galvanized (HDG) steel. In the presence of H2O and a Cu precursor, an artificial patina consisting of two distinctive phases was formed: a dense ~ 1 μm layer of anhydrous ZnCO3 adjacent to native zinc coating, and a needle-like porous structure showing resemblance to hydrozincite (Zn5(CO3)2(OH)6). The artificial patina layer significantly decreased the surface free energy of HDG, which was evidenced also by good wettability by a polyester melamine coating. Furthermore, the needle-like patina surface structure stayed intact through the coating process, indicating improved coating adhesion. ScCO2 treatment facilitates rapid and impurity-free surface treatment of hot dip galvanized steel, and could be used to tailor novel adhesion and corrosion promoting surface morphologies.

Microencapsulation of protein particles within lipids using a novel supercritical fluid process.

Solvent-free microparticles, loaded with a model protein (bovine serum albumin: BSA) have been produced using a novel coating process based on supercritical (SC) fluid technology. Coating material consists of either trimyristin (Dynasan114) or Gelucire50-02, two lipidic compounds having a high melting point. Microparticles were characterized as regards their morphology, protein content and in vitro release profile. A discontinuous coating made of crystalline micro-needles was obtained using Dynasan114. It led to particles with an initial burst release of about 70% in 30 min at 37 degrees C. However, a prolonged release of the protein has been achieved over a 24 h period from particles coated with Gelucire50-02, which produces a more homogeneous, film-forming coating. Furthermore, it was shown that BSA does not undergo any degradation after SCCO2 treatment under the SC conditions used in the coating process.

Impact of Supercritical Carbon Dioxide and High Pressure on Lipoxygenase and Peroxidase Activity

ABSTRACT:The effects of supercritical carbon dioxide (ScCO2) treatment and high hydrostatic pressure treatment on the activities of lipoxygenase (LOX) and peroxidase (POD) were studied. Hydrostatic pressure treatment (240 MPa, 55 °C, 15 min) of LOX and POD in 30% sucrose solutions without buffer led to approximately 80% and approximately 50% residual activity, respectively. Application of ScCO2 (35.2 MPa, 40 °C, 15 min for LOX and 62.1 MPa, 55 °C, 15 min for POD) achieved approximately 35% LOX and approximately 65% POD inactivity in 30 % sucrose solutions. Total inactivation of LOX (10.3 MPa, 50 °C and 15 min) and of POD (62.1 MPa, 55 °C and 15 min) could be achieved through ScCO2 treatment of unbuffered solution. Increasing the concentration of sucrose and buffering (pH range 4 to 9) of enzyme solutions resulted in increased resistance of the enzymes to ScCO2 treatment.

00/00790 Focus on the future of nuclear liability law

The former process for the cementation of transuranic (TRU) low-level wastes poses several technical problems. Specifically in the US a TRU waste-form has not yet passed the Waste Isolation Pilot Plant prohibition for free liquid. For this reason, treatment of the portland cement based waste-form with supercritical carbon dioxide (SCCO2) is shown to satisfy regulations. The effect of SCCO2 treatment by applying different CO2 pressure and temperature conditions (8.4 MPa<p<28 MPa, 35°C<T<62°C) on the leachability, phase constitution, and microstructure of surrogate-doped portland cement type I/II samples is presented. Leaching studies were performed using a synthetic groundwater leaching procedure. Changes in phase constitution of the major crystalline phases (Ca(OH)2, CaCO3) as well as the microstructure were measured by X-ray diffraction and scanning electron microscopy. SCCO2 treatment at 8.4 MPa and 35°C can be shown as the most promising conditions to satisfy the requirements of the Department of Transportation (DOT) and to enhance the natural aging reaction of cement paste by carbonation, combined with the lowest release rates of the surrogates 232Th, and 151/153Eu.

A study of hydrolases stability in supercritical carbon dioxide (SC-CO2)

The thermal stability and stability against pressurization/depressurization steps of lipase from Pseudomonas sp. and lipase from Candida cylindracea have been compared with data of other enzymes previously published. Hydrolases (lipases and esterases, crude preparations) with disulfide bridges have a lower degree of inactivation after several pressurization/depressurization steps but no better thermal stability (75°C, 150 bar, 24 h) compared to an enzyme without cystines. A higher loss in enzyme activity was observed after 30 depressurization steps from the liquid phase (56.3% loss of the initial activity) than from the supercritical phase (36.1% loss). Twenty phase transition cycles (liquid–supercritical and supercritical–liquid) do not cause more enzyme inactivation (86.8% residual activity) than simple incubation at 20°C (95.3%) or 65°C (82.1%). Comparing a crude form of lipasefrom Aspergillus niger and a preparation with higher activity, it turns out that the stability of the crude enzyme (92% of initial activity) against 30 pressurization/depressurization steps is similar to that of the purer preparation (102%). Also, thermal stabilities do not differ greatly (108% vs. 97%). Fluorescence spectra indicate no conformational change oflipase from Aspergillus niger after SC-CO2 treatment.

Lipid Composition of Hexane and Supercritical Carbon Dioxide Reduced Cholesterol Dried Egg Yolk , ,

Cholesterol was extracted from commercially spray-dried egg yolk using hexane at atmospheric pressure or supercritical carbon dioxide (SCCO2) (45 C, 238 atm; 45 C, 306 atm; 55 C, 374 atm). The effects of the different extraction methods on the lipid composition of the cholesterol-reduced yolks were evaluated. Polar lipids were separated into seven fractions using HPLC. Fractions 4, phosphatidylethanolamine (PE), and 5, phosphatidylcholine plus lysophosphatidylethanolamine (PC+LPE), accounted for almost 85% of the phospholipid (PL). As SCCO2 temperature and pressure increased, total lipid remaining decreased from 64.9 to 35.1%, but the PL content (15%) remained unaffected. The proportions of PE (12%) and PC+LPE (72%) of the PL fraction were constant. There was little effect on the fatty acid composition of the phospholipid fractions due to the SCCO2 treatments. However, the unsaturated fatty acids in the neutral lipids (NL) appeared to be effected by SCCO2 treatments. Hexane extracted a larger amount of total lipid (66%) and the NL fraction was decreased more than the PL fraction. Supercritical carbon dioxide was more efficient in removing cholesterol without major effects on the PL.

EFFECT OF SUPERCRITICAL CARBON DIOXIDE ON MICROBIAL POPULATIONS IN SINGLE STRENGTH ORANGE JUICE1

ABSTRACTThe effect of supercritical carbon dioxide on aerobic total plate count (TPC) of fresh‐squeezed and quick‐frozen single strength orange juice from Valencia oranges was studied. Orange juice was treated with SC CO2 at different temperatures (35° to 60°C) and pressures (8.3 to 33.1 MPa). SC CO2 treatment at 35°C reduced the TPC by 2 log cycles after 1 h treatment at 33 MPa. At 45°C and 33 MPa 2 log cycles reduction required 45 mins, and 15 mins treatment was sufficient at 60°C. D values of temperature control samples decreased as temperature increased, while that of supercritically treated juice decreased as pressure increased. D values at 35, 45 and 60°C of the supercritically treated juice at 33.1 MPa were calculated as 28, 22.6 and 12.7 min, respectively. The calculated values of z were 180°C, 167°C and 72°C at 8.3 MPa, 20.7 MPa and 33.1 MPa, respectively.