Carbon Dioxide In Solutions Research Articles

Effect of Residence Time on the Fractionation of Whey Protein Isolate with ScCO2 in a Continuous Reactor

This study proposes a fractionation of proteins using solutions (5%) of Whey Protein Isolate (WPI) and supercritical carbon dioxide (scCO2) in a continuous reactor. The experiments were performed at different values of pressure, temperature, and residence times - 65.4, 34.3, and 32.3 min, respectively. a-lactalbumin (a-LA) and s-lactoglobulin (s-LG) levels were determined by HPLC. WPI used without treatment showed an a/s ratio = 0.40. 16 MPa/55 °C and 16 MPa/60 °C were the conditions that suffered the most positive and negative influence of the increase and decrease in residence time, respectively. In the most severe condition, 24 MPa, 65 °C, and 4.0 mL·min-1, circular dichroism indicated that, despite not having obtained a high level of pureness, the fractionation technique employing scCO2 did not denature the proteins a-LA and s-LG.

Synthesis, characterization, CO2 mineralization in air, and thermal decomposition of nano- C8H10MgO10·4H2O powder

Effective solutions for efficient carbon dioxide (CO2) capture in air at room temperature are in high demand due to the major impacts CO2 has on global climatic changes. Solid adsorbents materials for CO2 capture received great attention over the past years, among them, magnesium-based sorbents have been identified as a promising solution for CO2 capture at intermediate temperatures. This study reports for the first time (1) the synthesis of monoclinic magnesium malate tetrahydrate by combining electrospinning and aging processes, and (2) its room temperature CO2 adsorption and mineralization in air. Commercial magnesium hydroxide (Mg(OH)2) powder was used as raw material in the synthesis of magnesium carbonate hydrates (MCH), by three processes; (1) direct calcination, (2) electrospinning and calcination, and (3) electrospinning, calcination, and aging (at room temperature and in air to incubate CO2 mineralization). The synthesized powder samples were characterized thoroughly using XRD, SEM, EDS, and TGA analyses. Effects of calcination temperature/aging time on CO2 adsorption (at room temperature), crystallization, and mineralization of MCH were studied. Interestingly, the results showed that the 6-month aged samples (via the third synthesis process above), recorded a CO2 adsorption capacity of 15.5 wt% within 90 min at 30 °C. Subsequently, three novel mechanisms of thermal decomposition CO2 adsorption/mineralization were proposed, and a theoretical upper limit of carbon saving potentials was estimated, i.e., 8 mol CO2 per 1 mol MgO. This work provides a novel CO2 mineralization approach that results in (1) effective and practical solutions of carbon dioxide (CO2) emission management and which holds (2) great potential for novel carbon-based fuels development.

TOWARD A NONINVASIVE MEASUREMENT METHOD OF CO2 ARTERIAL PRESSURE

Until now, the measurement of carbon dioxide blood pressure is done ex vivo, using an invasive process. This paper describes a first step toward a novel noninvasive process for in vivo measurement of this pressure. As first approximation, the blood solution is modeled as a simple aqueous solution of carbon dioxide in a cylindrical rigid canalization. The drift flux model and the Young–Laplace equation are employed to describe the fluid behavior. The numerical model relates the carbon dioxide pressure through the mixture pressure and velocity. The spatial distributions of these parameters are implemented to create linear mathematical relations between the mean mixture pressure and the radial velocity variation. As long as we are interested in a noninvasive measuring of the carbon dioxide pressure, a response model is proposed to describe the ultrasound signal backscattered by the considered solution. The linear relations are applied to deduce the carbon dioxide pressure through the measured radial velocity difference, using two computing methods of ultrasound signal. A comparative study is made between them showing the more appropriate process to compute the carbon dioxide pressure.

Highly Sensitive Porous PDMS-Based Capacitive Pressure Sensors Fabricated on Fabric Platform for Wearable Applications.

A novel porous polydimethylsiloxane (PDMS)-based capacitive pressure sensor was fabricated by optimizing the dielectric layer porosity for wide-range pressure sensing applications in the sports field. The pressure sensor consists of a porous PDMS dielectric layer and two fabric-based conductive electrodes. The porous PDMS dielectric layer was fabricated by introducing nitric acid (HNO3) into a mixture of PDMS and sodium hydrogen bicarbonate (NaHCO3) to facilitate the liberation of carbon dioxide (CO2) gas, which induces the creation of porous microstructures within the PDMS dielectric layer. Nine different pressure sensors (PS1, PS2,..., PS9) were fabricated in which the porosity (pore size, thickness) and dielectric constant of the PDMS dielectric layers were varied by changing the curing temperature, the mixing proportions of the HNO3/PDMS concentration, and the PDMS mixing ratio. The response of the fabricated pressure sensors was investigated for the applied pressures ranging from 0 to 1000 kPa. A relative capacitance change of ∼100, ∼323, and ∼485% was obtained by increasing the curing temperature from 110 to 140 to 170 °C, respectively. Similarly, a relative capacitance change of ∼170, ∼282, and ∼323% was obtained by increasing the HNO3/PDMS concentration from 10 to 15 to 20%, respectively. In addition, a relative capacitance change of ∼94, ∼323, and ∼460% was obtained by increasing the PDMS elastomer base/curing agent ratio from 5:1 to 10:1 to 15:1, respectively. PS9 exhibited the highest sensitivity over a wide pressure sensing range (low-pressure ranges (<50 Pa), 0.3 kPa-1; high-pressure ranges (0.2-1 MPa), 3.2 MPa-1). From the results, it was observed that the pressure sensors with dielectric layers prepared at relatively higher curing temperatures, higher HNO3 concentrations, and higher PDMS ratios resulted in increased porosity and provided the highest sensitivity. As an application demonstrator, a wearable fit cap was developed using an array of 16 pressure sensors for measuring and mapping the applied pressures on a player's head while wearing a helmet. The pressure mapping aids in observing and understanding the proper fit of the helmet in sports applications.

Density and Viscosity of Aqueous (Ammonia + Carbon Dioxide) Solutions at Atmospheric Pressure and Temperatures between 278.15 and 318.15 K

The density and the viscosity of aqueous (NH3 + CO2) solutions have been measured at atmospheric pressure over a temperature range of 278 to 318 K and apparent concentrations of solute between 4 and 10 molNH3 kgH2O–1 for NH3 and between 1 and 5.2 molCO2 kgH2O–1 for CO2. Solute loss from the aqueous solution associated with the high equilibrium partial pressure of NH3 and of CO2 has been limited by devices and protocols developed ad-hoc for sample preparation and density and viscosity measurement. Solid or vapor formation out of the initial liquid mixture has been avoided by means of a thermodynamic model-driven design of experiments. The experimental values gathered in this work have been used to obtain empirical models of density and viscosity, as a function of the apparent concentration of solutes, that is, NH3 and CO2, and temperature, that are able to reproduce the experimental values in all cases with deviations below 1.1% for density and below 9.4% for viscosity. While it is the first time that, to our knowledge, experimental viscosity data of aqueous ammonia solutions loaded with CO2 are added to the literature, the density model developed in this work is also able to reproduce experimental density data from literature with deviations below 1.5%, even outside the boundaries of the experimental conditions considered in this work.

ГЕОХИМИЧЕСКИЕ ОСОБЕННОСТИ КРЕМНИСТЫХ И КРЕМНИСТО-КАРБОНАТНЫХ МЕТАСОМАТИТОВ В МЕЛОВЫХ И ПАЛЕОГЕНОВЫХ ОТЛОЖЕНИЯХ НИЖНЕГО ПОВОЛЖЬЯ

The chemical composition and microstructure of Paleocene quartzite sandstones and Upper Cretaceous siliceous-carbonate rocks in the Volgograd right bank of the Volga River have been studied. Numerous pipe-like channels, along which hot silica-saturated solutions flowed at the stage of sand cementation are found to have a two-layer structure. The inner layer consisting of dense quartzite has been enriched with ore elements (Fe, V, Cr, Mo, Ni, W, and Cu). Majority of detected ore phases is presented with reduced forms while minority is represented with sulfide and oxide ones. Siliceous-carbonate rocks contain high concentrations of strontium, chromium, molybdenum, tungsten, and uranium in addition to calcium in cold carbon dioxide solutions outputs.

Supercritical fluid extraction with cosolvent of alkaloids from Lupinus mutabilis Sweet and comparison with conventional method

AbstractThe purpose of this study was to evaluate the use of supercritical fluid extraction with cosolvent (SFE‐co) as an alternative process in the extraction of lupin alkaloids. A sample of crushed Lupinus mutabilis Sweet seeds, with a high content of alkaloids, was treated using aqueous extraction (AQE) and SFE‐co, where the effect of the operating conditions and the solvent in the SFE‐co were evaluated applying a factorial design. Results showed that both methods reduced the content of total alkaloids in the lupin seed, ensuring its safe consumption. SFE‐co got an extraction yield (39.19 ± 0.14 mg/g) comparable with AQE (39.22 ± 0.16 mg/g) at a temperature of 323 K, a pressure of 27 MPa, using as a solvent supercritical carbon dioxide (scCO2) and dilute ethanol solution, but limited to a fraction of the treated sample. SFE‐co, unlike AQE, was able to keep the nutritional value of the lupin seeds, reducing the time process from 235 hr (AQE) to 2.5 hr, assuring the non‐use of an excessive amount of water and hazardous solvents. Moreover, the fractions formed in the extraction vessel by SFE‐co allowed the understanding of the extraction mechanism of different components from a complex matrix related to their chemical polarity.Practical ApplicationsThis study shows that it is possible to remove lupin alkaloids with green technology as supercritical fluid extraction with cosolvents, reaching extraction yields comparable with the conventional method (aqueous extraction), keeping the nutritional value of the sample, saving time and resources. However, working with a larger quantity of material than the usual used in a laboratory showed an inhomogeneous extraction of alkaloids from the sample, limiting the optimal extraction yield to one of the fractions formed. This reveals a future problem in the use of this technology at an industrial level, where the characteristics of the extracts are not only important but also the material treated since, in the lupin industry, the debittered seed and the released alkaloids are useful in the food and pharmaceutical industries, respectively.

Machine learning models for the prediction of diffusivities in supercritical CO2 systems

The molecular diffusion coefficient is fundamental to estimate dispersion coefficients, convective mass transfer coefficients, etc. Since experimental diffusion data is scarce, there is significant demand for accurate models capable of providing reliable diffusion coefficient estimations.In this work we applied machine learning algorithms to develop predictive models to estimate diffusivities of solutes in supercritical carbon dioxide. A database of experimental data containing 13 properties for 174 binary systems totaling 4917 data points was used in the training of the models. Five machine learning algorithms were evaluated and the results were compared with three commonly used classic models.The best results were found using the Gradient Boosted algorithm which showed an average absolute relative deviation (AARD) of 2.58 % (pure prediction). This model has five parameters: temperature, density, solute molar mass, solute critical pressure and solute acentric factor. For the same dataset, the classic Wilke-Chang equation showed AARD of 12.41 %. The developed model is provided as command line program.

Deposition of Ni-Based Thin Films in Supercritical Carbon Dioxide Solution Via Flow-Type Reaction System

Ni-based films have been extensively studied owing to their potential application in several fields such as metal coatings 1, microelectronic devices 2, magnetic devices 3, and catalysis 4. One of the techniques to deposit Ni thin films is supercritical fluid chemical deposition (SFCD) that offers the potential for the capability of high conformal step coverages and high-aspect-ratio features at materials dimensions 5-6. This technique includes the dissolution of precursor in supercritical fluids, adsorption of precursor and reducing agent onto the substrate surface, the reaction between adsorbed precursor and a reducing agent to its metal or metal oxide form on the substrate surface, and desorption of hydrogenated ligands from the substrate into the supercritical fluids phase. These process steps typically proceed under supercritical carbon dioxide (scCO2) solution due to its relatively moderate critical temperature (31.1°C) and pressure (7.38 MPa) 7 that has high molecular density, high diffusivity, low viscosity and zero surface tension 8.There are two basic type reaction systems for the SFCD technique namely batch-type and flow-type systems 9. In a typical batch-type system, a substrate, a fixed amount of precursor, CO2, and H2 gas are together charged in a closed reactor. The temperature and pressure could ramp up/down because of there is no inlet or outlet in this system. Consequently, the unreacted precursor or the reaction by-product accumulates in the reactor which may make the final product in poor film quality. To overcome this problem, we present here the deposition of Ni thin films in scCO2 solution from Ni(hfac)2 ·3H2O precursor through hydrogen reduction with a variety of independent variables via a flow-type reaction system. In this system, a precursor, CO2, and H2 are continuously supplied at a fixed flow rate, concentration, and pressure into a tubular flow reactor. Furthermore, we also employed the deposition of Ni-Sn alloy thin films with various compositions by flow-type SFCD reaction system, and then their activity was evaluated.The raw materials used in this study were Si(100) wafers having a TiN/SiO2 layer on top, Ni(hfac)2.3H2O, and (i-C3H7)4Sn as Ni and Sn precursor sources respectively, liquid CO2, hydrogen gas, and acetone. Liquid CO2 was cooled and pressurized above a CO2 critical pressure. H2 gas with a certain pressure was added to the scCO2 solution using a gas mixing unit. The precursor solution was added to scCO2 using a high-pressure pump. The substrate was placed inside a tubular flow reactor. And the pressure of this system was adjusted by a back-pressure regulator. All the process parameters of Ni thin film deposition are consisting of precursor concentration, hydrogen concentration, and growth temperature.Ni thin films were successfully deposited onto TiN/SiO2 film by the SFCD technique. Fig. 1 shows the XRD patterns of Ni films deposited at various precursor concentrations and temperatures. This shows that the Ni thin films were highly (111) structure-oriented. For the XRD patterns of Ni-Sn alloy thin films, the Ni(111) and Ni(200) peaks after added an Sn ratio was slightly shifted and became low intensity that might indicate the formation of the Ni-Sn alloys in a wide composition range. Based on the precursor concentration dependence, the curve trend lines in this study indicated Langmuir-Hinshelwood-type adsorption that the Ni growth rate found to be a zero-order reaction. At temperature dependence, the increase in H2 concentration resulted in the Ni growth rate increase, indicating the activation energy decreased with increasing H2 concentration.

STUDY OF UNIVERSAL COMBINED INHIBITOR FOR OIL AND GAS INDUSTRY

Using the gravimetric method, the inhibitory efficiency of the combined inhibitor with respect to hydrogen sulfide and carbon dioxide corrosion of St3 steel in model-produced water MI was studied. Corrosion tests were carried out in 0.5 l sealed vessels on St3 samples of size 30×20×1. Gossypol resin + MARZA was used as a multifunctional combined inhibitor. Diesel fuel and kerosene were used as solvent. It has been established that the protective effect of using a multifunctional combined inhibitor in formation water with oil containing hydrogen sulphide and carbon dioxide using kerosene as a solvent ranges from 75 to 96 and for diesel as 80 to 100. The combined inhibitor allows to achieve in the MI medium containing hydrogen sulfide and carbon dioxide in the process of daily testing the corrosion rate of steel is about 0.04 g/ m2∙h only in a concentration of not less than 70 mg/l. However, with an increase in the duration of the test by an order of magnitude, a similar corrosion rate is observed already at an inhibitor concentration of 50 mg/l. The same is characteristic of carbon dioxide and hydrogen sulfide - carbon dioxide solutions. The bactericidal properties of the combined inhibitor with respect to two types of Desulfovibriodesulfuricans and Desulfomicrobium sulfate-reducing bacteria were studied. The effect of the inhibitor on the number of bacterial cells and the formation of hydrogen sulfide in Postgate nutrient medium “B” was evaluated. It has been shown that the combined inhibitor exhibits a bacteriostatic effect on to sulphate-reducing bacteria. It was revealed that the degree of suppression of the number of microorganisms Desulfovibriodesulfuricans at a concentration of the combined inhibitor 100.0 mg/l is higher than Desulfomicrobium. In the latter case, to achieve this effect, 120.0 mg/l concentration of the combined inhibitor is required. The studied combination inhibitor causes inhibition of hydrogen diffusion in steel St3 in the MI medium saturated with H2S and CO2 separately and together, and contributes to preserving the ductile properties of the steel St3 after exposure to solutions compared to non-inhibited media.

Monitoring of the Environmental Technogenic Hazard of the Oil Extraction Plant

In Ukraine there is a tendency to increase the number of man-made emergencies, which directly affects the state of the environment and the population. Particularly dangerous situations are formed in case of disturbance of objects with high risk conditions, which include oil extraction enterprises. Observing the state of the environment and the operation of technological equipment at such enterprises, warning of the risk of emergencies that are hazardous to human health and the environment, are the basis and task of monitoring. The results of engineering and ecological analysis of the state of ecological and technogenic danger on the example of private joint-stock company «Kropyvnytskyi oil extraction plant» are presented in the work. The main probable factors of its formation at each technological stage of production are established. The sources of environmental and human hazards are technological equipment and materials. Pollutants of land, water and atmospheric air are dust of vegetable origin and meal, solvent of hexane and its vapors, carbon dioxide and washing solution - soda ash, etc. Expert evaluation of the main production operation - oil extraction was carried out in detail. The extraction process is the main production operation for both press oil and extraction oil, as well as cake and meal. The results of the study can be used to clarify the program of monitoring the sources of technogenic and environmental risk at high risk facilities, planning activities and means of improving the resilience of the enterprises of the industry, preventing emergencies and minimizing their consequences. Awareness enhances management efficiency and minimizes environmental and population risks.

Research universal combined inhibitor for the oil and gas industry

Using the gravimetric method, the inhibitory efficiency of the combined inhibitor with respect to hydrogen sulfide and carbon dioxide corrosion of St3 steel in model produced water MI was studied. Corrosion tests were carried out in 0,5 liter sealed vessels on St3 samples of size 30х20х1. Gossypol resin + MARZA was used as a multifunctional combined inhibitor. Diesel fuel and kerosene were used as solvent. It has been established that the protective effect of using a multi-functional combined inhibitor in formation water with oil containing hydrogen sulfide and carbon dioxide using kerosene as a solvent ranges from 75 to 96 and for diesel as 80 to 100. The combined inhibitor allows to achieve in the MI medium containing hydrogen sulfide and carbon dioxide in the process of daily testing the corrosion rate of steel is about 0,04 g/m2·h. only in a concentration of not less than 70 mg/l. However, with an increase in the duration of the test by an order of magnitude, a similar corrosion rate is observed already at an inhibitor concentration of 50 mg/l. The same is characteristic of carbon dioxide and hydrogen sulfide - carbon dioxide solutions.

Sodium hydrogen bicarbonate and water as blowing agent in palm kernel oil based polyol polyurethane foam

Palm kernel oil polyol based flexible polyurethane foams were synthesized by using two different types of natural blowing agentswater and sodium hydrogen bicarbonate (SHB), as alternatives to replace the climate change accelerating blowing agents (BA). The samples have been studied and analyzed by scanning electron microscopy (SEM), density measurements, Fourier transform infrared (FT-IR) spectroscopy and tear resistance test. SEM has revealed that adding water (2 php) has increased the cell size by 157% and pore size by 226%, while adding water (2 php) and SHB (25 php) have increased the cell size and pores by 276% and 920%, respectively. The addition of natural BAs has impacted struts differently. SHB has resulted in thicker struts compared to water due to increment of polyurethane mixture's viscosity. FT-IR spectroscopy has confirmed that both BAs did not affect the polyurethane’s functionalities, nor did react with any of the reactants. The absence of (–NCO) functionality peaks attributed to full exploitation of diisocyanate during the foaming reaction. It was found that additional of (2 php) water in the PU had reduced the density by 24%. On the other hand, additional of SHB (2 php) into PU, has increased the density of the foam, under water deficiency condition. It has been found that, adding 2 php SHB resulted high tear resistance strength (0.76 N/mm), which has shown an improvement of 26% of tear resistance strength as compared to the sample without blowing agents.

Silver Composites of Ultradisperse Polytetrafluoroethylene and Its Fractions in Supercritical Carbon Dioxide: Synthesis and Structural Study

Ultradisperse polytetrafluoroethylene is separated into fractions soluble and insoluble in supercritical carbon dioxide. The initial polymer and its soluble and insoluble fractions are impregnated with silver(I) (1,5-cyclooctadiene)-1,1,1,5,5,5-hexafluoroacetylacetonate in supercritical carbon dioxide solution for 6.6 h under thermodynamic conditions at 65°С and 8 MPa followed by reduction of the metal in an atmosphere of hydrogen for 6 h at 65°С and 1.2 MPa. According to X-ray fluorescence analysis, the content of the metal attains 2.4 wt %. Ag-polymer composites are studied by X-ray fluorescence spectroscopy, transmission electron microscopy, small-angle X-ray scattering, and X-ray photoelectron spectroscopy. It is shown that silver in the form of nanoparticles with a size of 1.0–7.5 nm is localized largely in the soluble low molecular weight fraction.

Kinetics of chemical absorption of carbon dioxide into aqueous calcium acetate solution

AbstractIncreasing energy demand in the world leads to more electricity generation mainly at fossil fuel power plants. Greenhouse gases are thus produced and mostly emitted to the atmosphere directly, resulting in global warming and climate change. Carbon dioxide is believed to be a main pollutant among greenhouse gases responsible from global warming. Conventional systems using mostly amine solutions to capture carbon dioxide at the source have some disadvantages, and alternatives are constantly being searched. In this work, a benign system of aqueous calcium acetate solution was investigated for this purpose. Calcium acetate is easy to produce, relatively cheap, environmentally friendly, nonhazardous, and noncorrosive. These properties make it a great alternative for use in capturing carbon dioxide. This absorption process is accompanied by chemical reaction. Therefore, the reaction kinetics needs to be investigated before its use in absorbers. A stirred cell reactor was used in the experiments using aqueous calcium acetate solution of different concentrations (2‐20% w/w) and different carbon dioxide concentrations in gas mixtures (4.5‐100% v/v dry carbon dioxide) at temperatures ranging from 286 to 352 K. The Gibbs free energy change for the overall reaction between carbon dioxide and aqueous calcium acetate solution was found to be –2.75 kJ/mol that shows the reaction is exergonic and occurs spontaneously. It was also found out that the reaction is pseudo–first order with respect to carbon dioxide which was also proven by calculating the Hatta number. Activation energy and Arrhenius (frequency) constant were also determined experimentally.

Carbon dioxide sealing-based inhibition of coal spontaneous combustion: A temperature-sensitive micro-encapsulated fire-retardant foamed gel

In order to enhance the inhibition efficiency of inhibitor on spontaneous combustion of coal and optimize the grouting process of traditional foamed gel, a temperature-sensitive retardant microcapsule (TSRM) was prepared via encapsulation of polyphenols with paraffin. Using composite surfactant (CFA) as a foaming agent and Carbon dioxide (instead of the traditional N2) as the gas source, a small amount of TSRM was incorporated into the water glass solution as base material to prepare microcapsuled retardant foamed gel (CDSFG-TSRM). TSRM temperature sensitivity allows melting at 60 °C followed by the release of tea polyphenols, which extends the effective period of tea polyphenols and improves the inhibitory effect on spontaneous coal combustion. Due to the inorganic polycondensation reaction between carbon dioxide and water glass solution, the preparation process of the material reduces carbon dioxide emission as a greenhouse gas and achieves a rapid gelation process of the mixed solution without the addition of a crosslinking agent, hence simplifying the preparation process of foam gel. The combination of in-situ FTIR and TG-IR indicated that the extent of oxidation on the surface hydroxyls of the coal sample treated with CDSFG-TSRM was low and the concentration of ether bond was high. The characteristic absorption peak intensity of C–H structure and Carbon dioxide were obviously weakened, and the characteristic absorption peak of Carbon dioxide appears at a higher temperature. In addition, CDSFG-TSRM has the advantages of shorter extinguishing time, higher retardant efficiency and difficulty in re-ignition.

Artificial Neural Network and Support Vector Regression Applied in Quantitative Structure-property Relationship Modelling of Solubility of Solid Solutes in Supercritical CO2

In this study, the solubility of 145 solid solutes in supercritical CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; (scCO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;) was correlated using computational intelligence techniques based on Quantitative Structure-Property Relationship (QSPR) models. A database of 3637 solubility values has been collected from previously published papers. Dragon software was used to calculate molecular descriptors of 145 solid systems. The genetic algorithm (GA) was implemented to optimise the subset of the significantly contributed descriptors. The overall average absolute relative deviation MAARD of about 1.345 % between experimental and calculated values by support vector regress SVR-QSPR model was obtained to predict the solubility of 145 solid solutes in supercritical CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;, which is better than that obtained using ANN-QSPR model of 2.772 %. The results show that the developed SVR-QSPR model is more accurate and can be used as an alternative powerful modelling tool for QSAR studies of the solubility of solid solutes in supercritical carbon dioxide (scCO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;). The accuracy of the proposed model was evaluated using statistical analysis by comparing the results with other models reported in the literature.

Effects of Propofol Anaesthesia Pre-Medicated with Xylazine on Serum Biochemical Profiles and Sleep Pattern in Red Sokoto Goats

This study was conducted with the objective to compare the sleep pattern and biochemical changes during general anesthesia at different timing interval with the baseline information using Propofol as the agent of choice and xylazine as a pre-medicant at 4 mg kg-1 intravenously and 0.025 mg kg-1 intramuscularly respectively. The onset of anaesthesia was rapid (30.1±11.3 seconds), the anaesthetic induction, surgical plane and recovery were good. There was a significant difference (P&lt;0.05) between baseline and other timing intervals in the rectal temperature, respiratory rate, systolic and diastolic blood pressure, but there was no significant difference (P&gt;0.05) in pulse rate. Similarly, a statistically significant difference (P&lt;0.05) was observed in the serum calcium ion, magnesium ion, hydrogen bicarbonate ion, Alkaline Phosphatase (ALP), creatinine, total protein and glucose levels, but there was no significant difference (P&gt;0.05) in the sodium ion, potassium ion, Alanine aminotransferase (ALT), Albumin (ALB), Aspartate aminotransferase (AST), , and Urea. It was concluded that the combination of Propofol and Xylazine at 4mgkg-1 and 0.25mgkg-1 respectively can be effectively and safely used for induction and maintenance of anaesthesia in Red Sokoto goats. It was also noted that recovery was smooth without any violence. The combination was also observed to have minimal effects on the clinico-biochemical parameters of Red Sokoto goats.

Formation of Dispersed Particles of Tungsten Oxide and Deposition of Platinum Nanoparticles on Them Using Organometallic Precursors from Solutions in Supercritical Carbon Dioxide

Abstract—A one-pot synthesis of dispersed platinum-tungsten composites has been developed. Initially, using tungsten hexacarbonyl as a precursor in solution in supercritical CO2 in the presence of oxygen as an oxidizer promoting thermal decomposition of the precursor, dispersed particles of tungsten oxide with a grain size of about 100 nm and an aggregate size of 200–500 nm have been synthesized. Then, these dispersed particles have been used as a substrate for the subsequent deposition of platinum nanoparticles, which includes two stages: (1) forming a film of an organometallic precursor by deposition from a solution in supercritical CO2 and (2) thermal decomposition of the precursor. Two types of platinum precursors, the dimethyl(1,5-cyclooctadiene)platinum and platinum hexafluoroacetylacetonate, which are both soluble in supercritical CO2, are typically used in the practice of similar studies. The size of the platinum nanoparticles formed using the former and latter precursors are 2.3 ± 0.7 nm and 3.5 ± 0.8 nm, respectively. The composites obtained are characterized by a relatively narrow size distribution of the noble metal nanoparticles and their uniform distribution over the surface of the particles of the dispersed carrier. Such materials may be of interest for (electro)catalysis tasks.

Rapid Expansion Supercritical Solution (RESS) of Carbon Dioxide as a Green Technology Method for Leucaena Leucocephala Solid Oil Particle Formation

Rapid expansion supercritical solution (RESS) is a technology introduced that produces a small solid oil particle with organic solvent free particle. RESS method is a better method compared to the traditional method due to many advantages such are produce clean extraction yields, obtain free solvent traces, environmental friendly and short processing time can be used in various industries such as cosmetic and pharmaceutical. Therefore, RESS technique is applied in order to produce direct solid oil particle from Luecaena leucocephala (L.leucocephala) pods instead of oil. In this study, the operating condition that applied during the RESS process in order to obtain the highest solid oil particle from the L.leucocephala pods sample are extraction temperature of 40 ºC, 45 ºC, 50 ºC, 55 ºC and 60 ºC and extraction pressure of 3000 psi, 4000 psi, 5000 psi, 6000 psi and 7000 psi at the constant extraction time of 40 minutes. The highest yield of L.leucocephala solid oil particles that obtained is about 0.65% at 60 oC and 7000 psi. The major components that obtained from the highest yield are 2,2,3-trimethyldecane, Cyclopentanone, propanoic acid and Cyclobutane, 1,2-diphenyl- by as identified by using Gas Chromatography Mass Spectrometry (GCMS).