SC-CO2 Flow Rate Research Articles

Precipitation of advanced nanomedicines (curcumin) using supercritical processing; experimental study, design and optimizing operating conditions

Curcumin is a known herbal medicine with numerous therapeutic effects and low bioavailability. Reducing the particle size of this medicine is a confirmed solution to increase its dissolution rate and bioavailability. To do so, Curcumin nanoparticles were produced in the present work by the supercritical gas anti-solvent (GAS) method. First, the minimum GAS operating pressure (Pmin) required to precipitate fine Curcumin particles from two solvents DMSO and ethanol was estimated using Peng-Robinson equation of state (PR-EoS). Then, Curcumin nanoparticles were precipitated from these two solvents under different operating conditions, specified by the Box–Behnken design method. Given the desired operating variables including pressure (120, 180, and 240 bar), temperature (308, 328, and 348 K), initial concentration (5, 35, and 65 mg/ml), flow rate of the supercritical carbon dioxide (scCO2) (10, 50, and 90 ml/min), and stirring rate (500, 1500, and 2500 rpm), their influence on the particle size of Curcumin was investigated, and optimum conditions were determined. At 240 bar and 328 K, nano Curcumin particles with the size of 230 nm and 81 nm were precipitated from DMSO and ethanol solutions with the initial concentration of 5 mg/ml and stirring rate of 1500 rpm, respectively. Results show that scCO2 flow rate is not a significant parameter.The remarkable reduction in the particle size of Curcumin from 28 ± 10 μm of the original sample to nano-scale confirms GAS efficiency. Also, the dissolution rate of the nanoparticles, produced in the optimal condition is much higher than the original sample, which can be due to their nano-metric size and lower degree of crystallinity.

Wet Extraction of By-Product Samples and Fractionation of Valuable Compounds using Supercritical CO2 Extraction: An Innovative Approach for Sustainable Resource Utilization

This research explores an innovative method for extracting and fractionating valuable compounds from by-product samples through the utilization of supercritical carbon dioxide (SC-CO2) extraction. By-products generated from various industrial processes often contain untapped reservoirs of valuable compounds, necessitating environmentally sustainable and economically viable extraction techniques. SC-CO2 extraction, known for its unique properties such as low toxicity, non-flammability, and tunable solubility, presents a promising avenue for efficient and selective extraction of target compounds.The study focuses on wet extraction, emphasizing the extraction of valuable compounds from by-products in their natural, moisture-laden state. This approach not only enhances the sustainability of the extraction process by minimizing pre-treatment steps but also broadens the scope of potential target compounds. The study further explores the critical parameters of SC-CO2 extraction, including pressure, temperature, and flow rate, to optimize the extraction efficiency and selectivity for different classes of compounds.

Alpaca fiber impregnated with alizarine and indigo dyes in a process using supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) is an alternative medium for a drastic reduction of water for the impregnation of synthetic and natural fibers, especially azoic dyes. In this study, we evaluated the impregnation of alpaca fibers with alizarine and indigo dyes in a process with scCO2, using DMSO as a cosolvent for the dyes. The scCO2 flow rate ranged from 8 to 17.0 g/min over 90 min through a 1000 mL impregnation autoclave, and the amounts of dye:Al2(SO4)3 loaded were 15%:55% of the fiber weight, respectively. Impregnation was evaluated between 308.15 −363.15 K and 22.40 −13.37 MPa, and the products were characterized by FTIR spectroscopy. The highest impregnation obtained was 142.05 mg alizarine/g fiber at 311.15 K and 17.9 MPa and 260.80 mg indigo/g fiber at 329.15 K and 17.5 MPa. Color fastness analysis revealed that the colored fibers were resistant to water washing in the range of 4–5, a commercially accepted level for the fiber.

Generation of Spherical Microparticles of Moringa Leaves through a Supercritical Antisolvent Extraction Process

The objective of this work was evaluation of the supercritical antisolvent extraction (SAE) process to generate microparticles with antioxidant activity from Moringa leaves. A biodegradable polymer was used as an inductor of particle precipitation. An ethanolic extract of 25 mg/mL was used in the SAE process, during which the influences of pressure (100–200 bar), temperature (35–55 °C) and extract–polymer ratio (0.11–0.33) on particle size and antioxidant activity were evaluated. An extract flow rate of 3 mL/min, a supercritical CO2 (scCO2) flow rate of 30 g CO2/min and a nozzle diameter of 100 µm were kept constant. The identification of several compounds of Moringa leaves, namely, coumaric acid and quercetin 3D glucoside, were determined with ultra-performance liquid chromatography coupled with mass spectrometry. The antioxidant activity of the extract and the precipitates was measured with 2,2-Diphenyl-1-picrylhydrazyl. Spherical microparticles with diameters in the range of 2–5 µm were obtained, with moderate antioxidant activity.

Particle preparation of pharmaceutical compounds using supercritical antisolvent process: current status and future perspectives.

The low aqueous solubility and subsequently slow dissolution rate, as well as the poor bioavailability of several active pharmaceutical ingredients (APIs), are major challenges in the pharmaceutical industry. In this review, the particle engineering approaches using supercritical carbon dioxide (SC CO2) as an antisolvent are critically reviewed. The different SC CO2-based antisolvent processes, such as the gas antisolvent process (GAS), supercritical antisolvent process (SAS), and a solution-enhanced dispersion system (SEDS), are described. The effect of process parameters such as temperature, pressure, solute concentration, nozzle diameter, SC CO2 flow rate, solvent type, and solution flow rate on the average particle size, particle size distribution, and particle morphology is discussed from the fundamental perspective of the SAS process. The applications of the SAS process in different formulation approaches such as solid dispersion, polymorphs, cocrystallization, inclusion complexation, and encapsulation to enhance the dissolution rate, solubility, and bioavailability are critically reviewed. This review highlights some areas where the SAS process has not been adequately explored yet. This review will be helpful to researchers working in this area or planning to explore SAS process to particle engineering approaches to tackle the challenge of low solubility and subsequently slow dissolution rate and poor bioavailability.

Optimization of Oil Recovery from Japonica Luna Rice Bran by Supercritical Carbon Dioxide Applying Design of Experiments: Characterization of the Oil and Mass Transfer Modeling

This study presents an optimization strategy for recovery of oil from Japonica Luna rice bran using supercritical carbon dioxide (scCO2), based on design of experiments (DoE). Initially, a 24−1 two level fractional factorial design (FFD) was used, and pressure, temperature, and scCO2 flow rate were determined as the significant variables; while the yield, total flavonoids content (TFC), and total polyphenols content (TPC) were the response functions used to analyze the quality of the extracts recovered. Subsequently, central composite design (CCD) was applied to examine the effects of the significant variables on the responses and create quadratic surfaces that optimize the latter. The following values of pressure = 34.35 MPa, temperature = 339.5 K, and scCO2 flow rate = 1.8 × 10−3 kg/min were found to simultaneously optimize the yield (6.83%), TPC (61.28 μmol GAE/g ext), and TFC (1696.8 μmol EC/g ext). The fatty acid profile of the oils was characterized by GC-FID. It was demonstrated that the acids in largest quantities are C16:0 (15–16%), C18:1 (41%), and C18:2 (38–39%). Finally, three mass transfer models were applied to determine the mass transfer coefficients and assess the cumulative extraction curves, with an AAD% of 4.16, for the best model.

Effect of Flow Rate on the Corrosion Behavior of API 5L X80 Steel in Water-Saturated Supercritical CO2 Environments

The effect of the water-saturated supercritical carbon dioxide (scCO2) flow rate on the corrosion behavior of API 5L X80 steel at a temperature of 35°C and pressure of 80 bar was investigated. Tests were performed with the samples attached to a rotating shaft inside an autoclave. Results indicate that increasing the scCO2 flow rate had no significant influence on the general/localized corrosion rate under the various dynamic conditions considered. The average general corrosion rate was 0.064 mm/y, while the average measured pitting penetration rates were one order of magnitude higher. The size of the corrosion features on the surface of the samples, which were believed to provide an indication as to the size of the condensed water droplets, was much smaller than the calculated critical droplet size needed to be displaced by the flow, supporting the theory as to why flow rate had little effect on the corrosion response.

Fabrication of wrinkled thermoplastic polyurethane foams by dynamic supercritical carbon dioxide foaming

Precise control and regulation of the cell structure in supercritical CO2 (scCO2) foaming is the key to boost the performance and extend the application of polymer foams. In this work, dynamic scCO2 foaming method is proposed to fabricate thermoplastic polyurethane (TPU) foams with unique wrinkly structures by introducing a continuous scCO2 flow field during scCO2 saturation. The scCO2 flow field applied on the TPU matrix generated intramolecular stress and resulted in the formation of wrinkles on the surface of cells. The structure of wrinkles was controlled by pivotal processing factors including foaming temperature, pressure, scCO2 flow rate, and scCO2 flow time. Attributing to the wrinkly structure, the wrinkled foams possessed superior compressive modulus, strength, recoverability, and energy absorption performance than conventional TPU foams, which make them a promising material for buffering and energy absorption applications. The dynamic scCO2 foaming method opens avenue for scCO2 foaming process involves dynamic field.

Supercritical carbon dioxide as a tool for improving the biocompatible properties of biopolymer and tissue specific scaffolds for tissue engineering

Objective: to investigate the efficacy of supercritical carbon dioxide (sc-CO2) for enhancштп the biocompatibility of biopolymer scaffolds from biodegradable materials and tissue-specific scaffolds from decellularized porcine liver slices (PLSs) or fine porcine cartilage particles (FPCPs).Materials and methods. Biopolymer scaffolds of a polyoxy(butyrate-co-valerate) and gelatin copolymer composition, 4 mm in diameter and 80 mm in length, were formed by electrospinning (NANON-01A, MECC CO, Japan) and stabilized by incubation in glutaraldehyde vapor for 48 hours at room temperature. For decellularization, PLSs and FPCPs were incubated under periodic stirring in buffer (pH = 7.4) solutions of sodium dodecyl sulfate (0.1%) and Triton X-100 with increasing concentrations (1, 2, and 3%). Treatment in a sc-CO2 atmosphere was done at 150–300 bar pressure, 35 °C temperature, and 0.25–2.5 mL/min flow rate of sc-CO2 for 8–24 hours. 10% ethanol was introduced as a polarity modifier. Cytotoxicity was studied according to GOST ISO 10993-5-2011. The growth of NIH/3T3 in the presence of samples was studied using an interactive optical system IncuCyte Zoom.Results. The effect of the sc-CO2 flow rate and pressure, and the effect of addition of ethanol, on the biocompatibility of scaffolds was investigated. It was found that treatment at a low sc-CO2 flow rate (0.25 mL/min) does not achieve the required cytotoxicity. Complete absence of cytotoxicity in biopolymer scaffolds was achieved in the presence of 10% ethanol, at a sc-CO2 flow rate of 2.5 mL/min, 300 bar pressure and 35 °C temperature after 8 hours of treatment. Effective removal of cytotoxic detergents from decellularized liver occurs already at a 150-bar pressure and does not require the addition of ethanol. Adding ethanol to sc-CO2 eliminates not only the cytotoxic, but also the cytostatic effect of tissue-specific scaffolds.Conclusion. Sc-CO2 treatment is an effective way to enhance the biocompatibility of three-dimensional porous matrices produced using cytotoxic substances: bifunctional crosslinking agents for biopolymer scaffolds and surfactants in the case of tissue-specific matrices. Addition of ethanol as a polarity modifier improves the treatment efficiency by eliminating both cytotoxic and cytostatic effects.

Process Intensification for Enzyme Assisted Turmeric Starch Hydrolysis at Hydrotropic and Supercritical Condition

The turmeric rhizome (Curcuma longa) contains curcuminoids embedded in the starch matrix. It is important to target starch removal by hydrolysis to enhance the rate and extent of extraction of curcuminoids. Enzymes are green catalysts and their activity can be enhanced by working on certain parameters. In the case of starch hydrolysis, α- amylase is more efficient when the starch is in the gelatinized form than when it is in its natural form. α-Amylase activity improves under supercritical carbon dioxide (scCO2) conditions. Certain surfactants improve α- amylase activity. Hydrotropes are a mild form of the surfactants. However, there are no reports on hydrolysis of turmeric starch in hydrotropic or supercritical (SFC) conditions. The work in this report shows beneficial effect of hydrotrope on the enzymatic reactions. There is marked enhancement in the diffusion coefficient (De) for curcuminoid extraction. The increased starch hydrolysis also improves the solid filtration rates after hydrotropic extraction of the curcuminoids. In the case of hydrotropic extraction of curcuminoids alone otherwise the filtration rate decreases due to the sticky nature of the extraction mass, caused by swelling of the starch. The present work includes hydrolysis of turmeric starch in its natural and gelatinized forms using α-amylase in hydrotrope solution (HS) and scCO2.The starch hydrolysis parameters include α-amylase concentration, solid loading concentration, scCO2 flow rate, presence of modifier in scCO2, residence time and scCO2 backpressure. The optimum hydrolysis parameters are 200 IU.cm-3 of α-amylase, at 328 K, 10 % (w/w) of turmeric loading concentration, 6.5 reaction pH, 900 rpm agitation speed for hydrotropic hydrolysis while the optimum conditions are 5 % w/w turmeric loading concentration, 40 min of scCO2 residence time, 15 cm3 of scCO2 phase modifier and 15 MPa as the scCO2 backpressure. The De for hydrolysis in the HS for turmeric starch in gelatinized form (A) was 4.1 x 10-11 m2s-1 and De for starch hydrolysis methods including in HS for turmeric starch in natural state (B), SFC condition for turmeric starch in natural state (C) and SFC for turmeric starch in gelatinized (D) were approximately 4.1 x 10-12 m2s-1. De for native turmeric starch in the absence of hydrotrope and SFC (E), and in case of gelatinized turmeric starch hydrolysis in absence of SFC and hydrotrope were 4.1x 10-14 and 4.1x 10-13 m2s-1, respectively. The filtration rates for (A), (D), (B), (C), (E) were 2 x 10-4, 1.25 x 10-11, 1.4 x 10-11, 7.3 x 10-11, 8.2 x 10-11 kgm2s-1 respectively. The De and filtration rate were noted in order (A) > (D) > (B) > (C) > (E) > (F). The 2.5 h SFC and 2.15 h HS enzyme treated turmeric powder gave 6.56 and 2.44 x 106 times increased filtration rate for curcuminoid extraction compared to untreated turmeric powder.

Optimization of process variables using response surface methodology for tocopherol extraction from Roselle seed oil by supercritical carbon dioxide

Hibiscus sabdariffa L. (Roselle) seeds are rich in proteins, carbohydrates and unsaturated fatty acids, and are a good source of minerals and antioxidants. Supercritical carbon dioxide (SC-CO2) extraction was applied for extraction of oil from Roselle seed at temperatures of 40 °C to 80 °C and pressures of 20 MPa to 30 MPa. The effects of temperature and pressure on the extraction yield and solubility of oil were determined. Process optimization was carried out using response surface methodology (RSM). A particle size of 300 μm, SC-CO2 flow rate of 5 mL/min and extraction time of 180 min were held constant throughout this study. The overall oil yield increased as pressure and temperature was increased, while a reverse effect was observed at higher temperatures. The optimum extraction conditions for Roselle seed oil corresponded to a pressure of 30 MPa and temperature of 40 °C. According to the analysis of variance (ANOVA), the coefficient of determination R2 for oil yield and gamma tocopherol concentration were 0.9723 and 0.9754, respectively, indicating a good correlation and agreement between the experimental and predicted values.

Generation of potent antioxidant nanoparticles from mango leaves by supercritical antisolvent extraction

The objective of this work was the obtaining of nanoparticles with potent antioxidant activity by supercritical antisolvent extraction process (SAE) using different methods of antioxidants extraction: subcritical fluid extraction (SFE), pressurized liquid extraction (PLE) and enhanced solvent extraction (ESE) with different operating conditions. The employed conditions in SAE process were 20 mg/mL of the extract concentration, 150 bar of pressure and temperatures of 35 and 50 °C into the vessel, extract flow rate of 5 mL/min and supercritical CO2 (scCO2) flow rate of 30 g CO2/min. The quantification of polyphenols of mango leaves was determined by HPLC and the antioxidant activity was measured by DPPH. Spherical nano- and microparticles with diameters in the range of 0.01–1.34 μm were obtained with much stronger antioxidant activity than the extracts (SFE, PLE, ESE). The major compound found in the extracts and the SAE precipitates was iriflophenone 3-C-β-d-glucoside.

Optimization of Supercritical Extraction of Coriander (Coriandrum sativum L.) Seed and Characterization of Essential Ingredients

Super critical fluid extraction (SC-CO2) of essential oil from coriander (Coriandrum sativum L.) seeds was performed. The effects of various parameters such as pressure (200-350 bar), temperature (30-45°C) and SC-CO2 flow rate (10-16 g/min) were investigated. The optimum condition was observed at pressure of 350 bar, temperature of 35°C and SC-CO2 flow rate of 14 g/min. The maximum extraction yield 4.55% was obtained under optimized conditions. ANOVA analysis showed that extraction pressure was the most significant factor on the essential oil yield. The morphology of coriander seeds was examined by SEM technique. The functional groups and chemical composition of coriander oil was analyzed by FT-IR and GC-MS. Petroselinic acid, myristic acid, linalool, 4-bromo-2-adamantanol, cis-isoapiole and (-)-carvone were the major components in the essential oil of coriander seed.

Optimisation of Process Parameters for Supercritical Carbon Dioxide Extraction of Oil from Gac Seed Kernel Powder

This study aimed to maximize the oil yield from Gac seed kernels using supercritical carbon dioxide (SC-CO2) extraction. Gac seed kernel powder (4 g) with particle diameters <500 μm was extracted for 32 min. Response surface methodology with central composite design was used to optimize the SC-CO2 extraction parameters: temperature (60-80°C), pressure (5,000-7,000 psi (34,474-48,263 kPa)) and SC-CO2 flow rate (1-2.5 mL/min). The oil yield, accurately represented by a second order equation (R2 = 0.99, p<0.0001), was predicted to be most substantially and significantly influenced by temperature (p<0.0001), followed by pressure (p<0.02) but not by the CO2 flow rate (p = 0.20). The optimum conditions were predicted to be: temperature of 73°C, pressure of 5,900psi (40,679kPa) and CO2 flow rate of 1.5 mL/min. The optimum oil yield was predicted to be 34.1±0.8% (g oil/100 g Gac seed kernel powder) and experimentally validated at 33.9±0.5%. The oil was likely high in saturated fat, being solid at room temperature and having a low iodine value, with 33.2±1.1% being unsaponifiable matter.

Response surface optimization of Safranal and Crocin extraction from Crocus sativus L. via supercritical fluid technology

Safranal (2,3-Dihydro-2,2,6-trimethylbenzaldehyde) and Crocin (Crocetin digentoboisyl ester) were experimentally extracted from saffron (Crocus sativus L.) via supercritical carbon dioxide (SC-CO2) and modified SC-CO2 with methanol as entrainer, respectively. The extracted samples were analyzed by high performance liquid chromatography (HPLC). The response surface methodology (RSM) was applied to evaluate the effects of four independent variables (temperature, pressure, SC-CO2 flow rate, and dynamic extraction time) on the recovery of Safranal and Crocin. The recovery results indicated that the data adequately fitted into a second-order polynomial model. The optimal values of variables for Safranal extraction were determined by RSM to be 92°C, 21.3MPa, 0.9cm3min−1 and 122.0min for the optimum predicted recovery of 91.76w/w%. Optimum Recovery of Crocin (32.67w/w%) was obtained at 44°C, 19.3MPa, 1.0cm3min−1 and 110.0min. The accuracy of the modeling optimal Safranal and Crocin recovery was validated with triplicate experiments giving the average extraction recovery of 90.03 and 33.05 respectively.

Supercritical extraction of sunflower oil: A central composite design for extraction variables

Supercritical carbon dioxide (SC-CO2) extraction of sunflower seed for the production of vegetable oil is investigated and compared to conventional methods. The effects of extracting variables, namely pressure, temperatures, particle size, SC-CO2 flow rate and co-solvent, on SC-CO2 extraction are investigated. The maximum yield for sunflower oil is found to be about 54.37wt%, and is obtained when SC-CO2 extraction is carried out at 80°C, 400bar, 0.75mm particle and 10g/min solvent flow with 5% co-solvent. A central composite design is used to develop the model and also to predict the optimum conditions. At optimum conditions obtained based on desirability function, 80.54°C, 345bar, 1.00mm, 10.50g/min and 7.58% ethanol, SC-CO2 extraction has performed and found that extraction yield dropped by 2.88% from the predicted value. Fatty acid composition of SC-CO2 and hexane extracted oil shows negligible difference and found high source of linoleic acid.

Experimental investigation of carbon dioxide trapping due to capillary retention in saline aquifers

AbstractCapillary trapping is a physical mechanism by which carbon dioxide (CO2) is naturally immobilized in the pore spaces of aquifer rocks during geologic carbon sequestration operations, and thus a key aspect of estimating geologic storage potential. Here, we studied capillary trapping of supercritical carbon dioxide (scCO2), and the effect of initial scCO2 saturation and flow rate on the storage/trapping potential of Berea sandstone. We performed two‐phase, scCO2‐brine displacements in two samples, each subject to four sequential drainage–imbibition core‐flooding cycles to quantify end‐point saturations of scCO2 with the aid of micro‐ and macro‐computed tomography imaging. From these experiments, we found that between 51% and 75% of the initial CO2 injected can be left behind after the brine injection. We also observed that the initial scCO2 saturation influenced the residual scCO2 saturation to a greater extent than the rate of brine injection under the experimental conditions examined. In spite of differences in the experimental conditions tested, as well as those reported in the literature, initial and residual saturations were found to follow a consistent relationship.

Experimental and theoretical investigation of supercritical drying of silica alcogels

Extraction of ethanol from pores of cylindrical silica alcogel samples using supercritical CO2 (scCO2) in a tubular extraction vessel was investigated both by experiments and simulations. Partial differential equations representing mass transfer within the cylindrical silica alcogel phase and in the external scCO2 phase were developed and solved using finite difference method. The percent removal data as a function of time were found to be in good agreement with model results using mass transfer coefficients regressed from the experimental data. The mass transfer coefficients were found to be higher by about a factor of three from two of the correlations tested which were developed for supercritical extraction. Effect of scCO2 flow rate on the drying was investigated through experiments and simulations. Increasing flow rate led to a decrease in effluent concentration at a specific time but did not significantly affect rate of extraction of ethanol. Effects of the magnitude of the effective diffusion coefficient and alcogel thickness on drying were investigated through simulations. Drying time of the alcogel decreased with decreasing gel thickness and increasing effective diffusion coefficient.

Scalable organic solvent free supercritical fluid spray drying process for producing dry protein formulations

In this study, we evaluated the influence of supercritical carbon dioxide (scCO2) spray drying conditions, in the absence of organic solvent, on the ability to produce dry protein/trehalose formulations at 1:10 and 1:4 (w/w) ratios. When using a 4L drying vessel, we found that decreasing the solution flow rate and solution volume, or increasing the scCO2 flow rate resulted in a significant reduction in the residual water content in dried products (Karl Fischer titration). The best conditions were then used to evaluate the ability to scale the scCO2 spray drying process from 4L to 10L chamber. The ratio of scCO2 and solution flow rate was kept constant. The products on both scales exhibited similar residual moisture contents, particle morphologies (SEM), and glass transition temperatures (DSC). After reconstitution, the lysozyme activity (enzymatic assay) and structure (circular dichroism, HP-SEC) were fully preserved, but the sub-visible particle content was slightly increased (flow imaging microscopy, nanoparticle tracking analysis). Furthermore, the drying condition was applicable to other proteins resulting in products of similar quality as the lysozyme formulations. In conclusion, we established scCO2 spray drying processing conditions for protein formulations without an organic solvent that holds promise for the industrial production of dry protein formulations.

Controlled graft copolymerization of lactic acid onto starch in a supercritical carbon dioxide medium

This work presents a new approach for the synthesis of a starch-g-poly L-lactic acid (St-g-PLA) copolymer via the graft copolymerization of LA onto starch using stannous 2-ethyl hexanoate (Sn(Oct)2) as a catalyst in a supercritical carbon dioxide (scCO2) medium. The effects of several process parameters, including the pressure, temperature, scCO2 flow rate and reaction time, on the polymerization yield and grafting degree were studied. Amorphous graft St-g-PLA copolymers with increased thermal stability and processability were produced with a high efficiency. The maximum grafting degree (i.e., 52% PLA) was achieved with the following reaction conditions: 6h, 100°C, 200bar and a 1:3 (w/w) ratio of St/LA. It was concluded that these low cost biobased graft biopolymers are potential candidates for several environment-friendly applications.