SC-CO2 Method Research Articles

Increased efficiency of peripheral nerve regeneration using supercritical carbon dioxide-based decellularization in acellular nerve graft

Acellular nerve grafts (ANGs) are a promising therapeutic for patients with nerve defects caused by injuries. Conventional decellularization methods utilize a variety of detergents and enzymes. However, these methods have disadvantages, such as long processing times and the presence of detergents that remain on the graft. In this study, we aimed to reduce process time and minimize the risks associated with residual detergents by replacing them with supercritical carbon dioxide (scCO2) and compared the effectiveness to Hudson’s decellularization method, which uses several detergents. The dsDNA and the expression of MHC1 and 2 were significantly reduced in both decellularized groups, which confirmed the effective removal of cellular debris. The extracellular matrix proteins and various factors were found to be better preserved in the scCO2 ANGs compared to the detergent-ANGs. We conducted behavioral tests and histological analyses to assess the impact of scCO2 ANGs on peripheral nerve regeneration in animal models. Compared with Hudson’s method, the scCO2 method effectively improved the efficacy of peripheral nerve regeneration. Therefore, the decellularization method using scCO2 is not only beneficial for ANG synthesis, but it may also be helpful for therapeutics by enhancing the efficacy of peripheral nerve regeneration.

A New Approach for Improving Flame Retardancy of Automotive Interior Upholstery

This study presents the flame retardant (FR) performance of chemically treated automotive upholstery fabrics using two different impregnation methods of Resin Transfer Molding (RTM) and supercritical carbon dioxide (scCO2). Referring to the related standards, untreated seat fabric obtained from seat upholstery of a bus (neat fabric, NF) and treated fabric samples underwent burning rate (BR) and limiting oxygen index (LOI) tests to compare effect of treatment and impregnation methods on FR performance. Thermal analysis was also conducted on the samples considering onset degradation temperatures and char yields. The results showed that BR and LOI of all samples were in acceptable range and treatment provided enhancement in FR performance of NF. The treated sample using scCO2 method gave the highest LOI value of 32% and the lowest BR of 21 mm/min subtending to 18.5% increase in LOI and 30% reduction in BR compared to those of NF. The performance of treatment in RTM was worse than that of scCO2 and better than that of NF. The results confirm that both treatment and methods used in this study give promising results for safety against fire in transportation vehicles.

Drug-impregnated contact lenses via supercritical carbon dioxide: A viable solution for the treatment of bacterial and fungal keratitis

Keratitis is a corneal infection caused by various bacteria and fungi. Eye drop treatment of keratitis involves significant challenges due to difficulties in administration, inefficiencies in therapeutic dosage, and frequency of drug applications. All these are troublesome and result in unsuccessful treatment, high cost, time loss, development of drug resistance by microorganisms, and a massive burden on human health and the healthcare system. Most of the antibacterial and antifungal medications are non-water-soluble and/or include toxic drug formulations. Here, the aim was to develop drug-loaded contact lenses with therapeutic dosage formulations and extended drug release capability as an alternative to eye drops, by employing supercritical carbon dioxide (ScCO2) as a drug impregnation solvent to overcome inefficient ophthalmic drug use. ScCO2, known as a green solvent, has very low viscosity which provides high mass transfer power and could enhance drug penetration into contact lenses much better with respect to drug loading using other solvents. Here, moxifloxacin (MOX) antibiotic and amphotericin B (AMB) antifungal medicines were separately loaded into commercially available silicone hydrogel contact lenses through 1) drug adsorption from the aqueous solutions and 2) impregnation techniques via ScCO2 and their efficacies were compared. Drug impregnation parameters, i.e., 8–25 MPa pressure, 310–320 K temperature, 2–16-hour impregnation times, and the presence of ethanol as polar co-solvent were investigated for the optimization of the ScCO2 drug impregnation process. The highest drug loading and long-term release kinetic from the contact lenses were obtained at 25 MPa and 313 K with 2.5 h impregnation time by using 1 % ethanol (by volume). Furthermore, antibacterial/antifungal activities of the MOX- and AMB-impregnated contact lenses were effective against in vitro Pseudomonas aeruginosa (ATCC 10145) bacteria and Fusarium solani (ATCC 36031) fungus for up to one week. Consequently, the ScCO2 method can be effectively used to impregnate commercial contact lenses with drugs, and these can then be safely used for the treatment of keratitis. This offers a sustainable delivery system at effective dosage formulations with complete bacterial/fungal inhibition and termination, making it viable for real animal/human applications.

Policosanols from grape marc: A new step towards a sustainable biorefinery for the wine industry by SC-CO2 extraction

Supercritical carbon dioxide (SC-CO2) extraction of policosanol (PC) from grape marc was investigated for the first time. Employing the broken plus intact cells (BIC) model (Sovová's model) the investigation focused on analyzing the SC-CO2 process to extract the nonpolar fraction from grape marc efficiently. Operating conditions for SC-CO2 extraction—280 bar pressure, 70 °C temperature, and a flow rate of 10 kgCO2/h—yielded the highest policosanol content. The extracted policosanol ranged between 3922 and 4083 mg/kgDM, constituting approximately 8 % of the total extraction yield. Surprisingly, this amount of PC was of the same order of magnitude found in beeswax yellow, a well-known rich natural source of PC. The primary aliphatic alcohols found in the PC from grape marc were hexacosanol, octacosanol, and triacontanol. These findings were consistent with grape marc samples from other Italian regions. Furthermore, a comparative analysis between SC-CO2 and Soxhlet extraction methods for PC was carried out.

A new class of layered Bi2O2S nanopetals by one-pot supercritical-CO2 approach: A reliable electrocatalyst for analgesic bioflavonoid detection

Nanomaterials frequently draw a lot of interest in a variety of disciplines, including electrochemistry. Developing a reliable electrode modifier for the selective electrochemical detection of the analgesic bioflavonoid i.e., Rutinoside (RS) is a great challenge. Here in, we have explored the supercritical-CO2 (SC–CO2) mediated synthesis of bismuth oxysulfide (SC–BiOS) and reported it as a robust electrode modifier for the detection of RS. For a comparison study, the same preparation procedure was carried out in the conventional approach (C–BiS). The morphology, crystallography, optical, and elemental contribution analyses were characterized to understand the paradigm shift in the physicochemical properties between SC-BiOS and C–BiS. The results exposed the C–BiS had a nano-rod-like structure with a crystallite size of 11.57 nm; whereas the SC-BiOS had a nano-petal-like structure with a crystallite size of 9.03 nm. The B2g mode in the optical analysis confirms the formation of bismuth oxysulfide by the SC-CO2 method with the Pmnn space group. As an electrode modifier, the SC-BiOS achieved a higher effective surface area (0.074 cm2), higher electron transfer kinetics (0.13 cm s−1), and lower charge transfer resistance (403 Ω) than C–BiS. Further, it provided a wide linear range of 0.1–610.5 μM L−1 with a low detection and quantification limit of 9 and 30nM L−1 and an appreciable sensitivity of 0.706 μA μM−1 cm−2. The selectivity, repeatability, and real-time application towards the environmental water sample with a recovery of 98.87% were anticipated for the SC-BiOS. This SC-BiOS unlocks a fresh avenue to construct a design for the family of electrode modifiers utilized in electrochemical applications.

Comparison of Phenolic Compound, Colour Value, and Antioxidant Activity of Roselle Calyces Extract Between Modified Supercritical Carbon Dioxide and Conventional Extraction

Supercritical carbon dioxide (SC-CO2) is a clean and green technology for extracting polyphenols and antioxidants from roselle (Hibiscus Sabdariffa) as nutraceutical ingredients and high-value co-products development. To increase the SC-CO2 fluid affinity towards polar compounds, general regard as a safe (GRAS) solvent, ethanol-water was added in a small amount as a modifier. Dry roselle calyces were extracted using modified SC-CO2 and conventional methods (Soxhlet and Shaking Water Bath) to determine whether the SC-CO2 technology may improve the extraction of phenolic content and antioxidant activity. The results showed that the SC-CO2 extract had a significantly higher yield of total phenolic and flavonoid content than the conventional extraction method. The conventional method produces a redder but lighter extract than SC-CO2 extraction. SC-CO2 also had a higher antioxidant activity as measured by DPPH radical scavenging. These results suggest that SC-CO2 technology increases the quantity and quality of roselle calyces’ extract. The findings increased the reliability of using this technique to produce high-value products from this high-value plant. Roselle as a low-cost sustainable local crop source, as well as SC-CO2 as a clean energy process with low environmental impact, excellent solvent recyclability, and reduced chemical use, could increase the market value of antioxidant-rich extract.

Full physicochemical and biocompatibility characterization of a supercritical CO2 sterilized nano-hydroxyapatite/chitosan biodegradable scaffold for periodontal bone regeneration

Despite bone's innate self-renewal capability, some periodontal pathologic and traumatic defects' size inhibits full spontaneous regeneration. This current research characterized a 3D porous biodegradable nano-hydroxyapatite/chitosan (nHAp/CS, 70/30) scaffold for periodontal bone regeneration, which preparation method includes the final solvent extraction and sterilization through supercritical CO2 (scCO2).Micro-CT analysis revealed the fully interconnected porous microstructure of the nHAp/CS scaffold (total porosity 78 %, medium pore size 200 μm) which is critical for bone regeneration. Scanning electron microscopy (SEM) showed HAp crystals forming on the surface of the nHAp/CS scaffold after 21 days in simulated body fluid, demonstrating its bioactivity in vitro. The presence of nHAp in the scaffolds promoted a significantly lower biodegradation rate compared to a plain CS scaffold in PBS. Dynamic mechanical analysis confirmed their viscoelasticity, but the presence of nHAp significantly enhanced the storage modulus (42.34 ± 6.09 kPa at 10 Hz after 28 days in PBS), showing that it may support bone ingrowth at low-load bearing bone defects. Both scaffold types significantly inhibited the growth, attachment and colony formation abilities of S. aureus and E. coli, enhancing the relevance of chitosan in the grafts' composition for the naturally contaminated oral environment. At SEM and laser scanning confocal microscopy, MG63 cells showed normal morphology and could adhere and proliferate inside the biomaterials' porous structure, especially for the nHAp/CS scaffold, reaching higher proliferative rate at day 14. MG63 cells seeded within nHAp/CS scaffolds presented a higher expression of RUNX2, collagen A1 and Sp7 osteogenic genes compared to the CS samples.The in vivo subcutaneous implantation in mice of both scaffold types showed lower biodegradability with the preservation of the scaffolds porous structure that allowed the ingrowth of connective tissue until 5 weeks. Histology shows an intensive and progressive ingrowth of new vessels and collagen between the 3rd and the 5th week, especially for the nHAp/CS scaffold.So far, the scCO2 method enabled the production of a cost-effective and environment-friendly ready-to-use nHAp/CS scaffold with microstructural, chemical, mechanical and biocompatibility features that make it a suitable bone graft alternative for defect sites in an adverse environment as in periodontitis and peri-implantitis.

Experimental - Theoretical approach for determination of Metformin solubility in supercritical carbon dioxide: Thermodynamic modeling

Metformin, as an anti-hyperglycemic, is the main medicine for treating diabetes of type II. However, its daily dose is high due to its incomplete absorption and short half-life, which leads to digestive problems and patient complaints. Controlled release and increased bioavailability of this drug can be achieved using novel drug delivery systems produced with an appropriate supercritical carbon dioxide (scCO2) method. However, the solubility of Metformin in scCO2 is an essential parameter for this purpose which needs to be evaluated prior to the processing. In the current research, solubility of Metformin in scCO2 was determined at temperatures of 308, 318, 328, and 338 K, and pressures of 140, 170, 200, 230, 260, and 290 bar. It was obtained between 0.39 × 10−6 up to 1.23 × 10−6 (mole fraction). Also, the resulting values were correlated through an equation of state (Peng-Robinson (PR-EoS)) and eight well-known empirical correlations (Chrastil, Sung and Shim, Adachi and Lu, Si-Moussa, Bartle, Jafari Nejad, Keshmiri, and Jouyban). The average AARD% value of 8.24 for the PR-EoS model confirmed its satisfactory precision to predict the Metformin solubility in scCO2. Among the mentioned empirical models, the models defined by Jafari Nejad (AARD% of 4.36 and AICc of −997.07) and Keshmiri (AARD% of 4.73 and AICc of −1048.81) show the highest correlation accuracy. Moreover, the total mixing heat, the vaporization enthalpy, and the solvation enthalpies of the Metformin-scCO2 mixture were computed.

Techno-economic strategies for improving economic viability of β-carotene extraction using natural oil and supercritical solvent: A comparative assessment

Dunaliella salina microalgae is a third-generation feedstock that is both thermophilic and halophilic and can be used to produce nutritious food supplements such as β-carotene. Although several techno-economic studies have been carried out to produce the pigment, most of them considered traditional synthetic chemicals such as hexane, acetone, and petroleum ether as solvents for extracting β-carotene from D. salina. In this study, techno-economic assessment is carried out with the aim of producing food-grade products for human consumption via greener methods of D. salina cultivation, harvesting, and extraction. The techno-economic assessment of the extraction of β-carotene and by-products using natural and edible corn oil and supercritical CO2 reveal that the processes are economically feasible, with a payback time of 5.9 y and 2.7 y (for corn oil and SC-CO2 methods), respectively. The ROIs for both methods are also positive, that is, 16.9 % and 37.1 %, respectively and greater than the prevailing interest rates in most countries. Sensitivity analyses show that the payback time is most sensitive to the yield of β-carotene, its production output, and its selling price. This assessment shows that food-grade β-carotene can be produced in bulk quantity from D. salina (as an alternative to other sources such as carrots, tomatoes, pumpkins, etc.) in order to satisfy the growing demands of nutritional markets.

Malic acid pathway of constructing high-performance Ni anticorrosive coatings using supercritical-CO2 electrodeposition

We presented the fabrication of nickel (Ni) coatings from malic acid-supported Ni electrolyte (M/Ni-E) as an alternative for boric acid by supercritical-CO2 (SC–CO2) electrodeposition. The surface roughness, morphology, and crystal phase structure of the prepared coatings were analyzed with an atomic force microscope (AFM), field emission scanning electron microscope (FESEM), and X-ray diffraction (XRD) techniques. Corrosion resistance was evaluated through standard electrochemical methods such as linear polarization and electrochemical impedance spectroscopy (EIS) techniques with 1 M HCl solution. Based on the FESEM, AFM, and XRD results, the film prepared by a malic acid-supported electrolyte exhibits a compact coating with smaller grains (21.6 nm) and lower surface roughness (RMS = 7.59 nm). The corrosion resistance of the film prepared with M/Ni-E by SC-CO2 method shows a higher corrosion resistance of 570 Ω/cm2. Thereby, malic acid is suggested as a suitable replacement for boric acid and SC-CO2 electrodeposition process as an environmental-friendly approach.

Effects of Supercritical Carbon Dioxide Extraction (SC-CO2) on the Content of Triterpenoids in the Extracts from Ganoderma Lucidum

This research investigates the effect of SC-CO2 extraction parameters on the triterpenoid recovery from G. lucidum. The SC-CO2 parameters included extraction pressure, extraction temperature, and extraction time. The extraction pressure was varied between 200, 400 and 600 bar, the extraction temperature between 30, 55 and 80 °C, and the extraction time between 30, 75 and 120 min. In this study, the SC-CO2 parameters were first optimized using a response surface methodology (RSM) for maximum triterpenoid recovery. The results showed that the optimal RSM-based SC-CO2 conditions were 430 bar extraction pressure, 54.8 °C extraction temperature and 78.90 min extraction time, achieving the maximum triterpenoid recovery of 1.56 mg/100g. The kinetic behavior of SC-CO2 process was subsequently characterized using a second-order kinetic model under variable extraction pressures and extraction temperatures, given a SC-CO2 time interval. The second-order kinetic models represented well the experimental results of triterpenoid extraction by SC-CO2 method. At these conditions, the triterpenoid extract also exhibited strong scavenging activities with IC50 values of 0.49 mg/mL for the DPPH radical scavenging activity and 0.26 mg/mL for ABTS radical scavenging activity. Thus, triterpenoids extracted from G. lucidum could be regarded as a potential agent for medicinal treatment. The results also suggest that the SC-CO2 extraction can be a useful extraction method for triterpenoid extraction from G. lucidum.

Post-supercritical CO2 electrodeposition approach for Ni-Cu alloy fabrication: An innovative eco-friendly strategy for high-performance corrosion resistance with durability

This work focuses on two meaningful points, one is the utilization of supercritical CO2 as a green solvent, and the other is achieving the proper distribution of Ni and copper Cu in the Ni-Cu alloy, as a protective layer to inhibit the corrosion. For the first time, a new post-supercritical carbon dioxide (PSC-CO2) mediated electrodeposition approach has been employed to prepare Ni-Cu alloy film. The use of SC-CO2 eliminates the need for hazardous surfactants. For the electrodeposition of Ni-Cu alloys, in the conventional method, Ni deposition predominates, whereas in the SC-CO2 method Cu deposition predominates. When combining both techniques, a proper proportion of Ni% and Cu% were achieved in Ni-Cu alloys. The physical characteristics were examined using spectroscopic techniques. The findings of electrochemical tests conducted in a 3.5% NaCl corrosive medium demonstrate that Ni-Cu alloy prepared using the PSC-CO2 approach has higher corrosion resistance than alloys prepared using the SC-CO2 and conventional methods. Moreover, it exhibits the enhanced charge transfer resistance (Rct = 1352 Ω) even after the 732 h continuous immersion in the corrosive medium. Therefore, the PSC-CO2 technique for producing Ni-Cu films can be an eco-friendly approach for superior corrosion resistance performance with long-term stability.

Berberis Vulgaris Fruit: Determination of Phenolic Compounds in Extracts Obtained by Supercritical CO2 and Soxhlet Methods Using HPLC.

Recently, research studies on nutraceutically important polyphenolic substances have attracted intensive attention. Berberis vulgaris is an important source of polyphenolic compounds and is often used in traditional medicine. In this study, the extraction of rutin and apigenin rich oil from Berberis vulgaris fruits was evaluated by supercritical carbon dioxide (Sc-CO2) extraction method with and without co-solvent. As valuable antioxidants, rutin and apigenin content of extracts were analyzed by HPLC, and their amounts were maximized via parametric optimization. The rutin compound studied in this research has the potential to be a drug against the COVID-19 virus. The operating conditions were considered in the range of 35–70 °C temperatures, 140–240 bar of pressures, 0.35–1.00 mm of mean particle sizes, 3–7 l/min of CO2 flow rates, and 0–8% w/w co-solvent. As a result of Sc-CO2 extractions, the amounts of rutin and apigenin were found as 173 ± 14.97 µg/g and 2.91 ± 0.11 µg/g, respectively, with the 8% (w/w) co-solvent addition. The amounts of rutin and apigenin obtained by Soxhlet extractions were found as 208.81 ± 8.48 µg/g and 6.55 ± 0.21 µg/g, respectively. When the Sc-CO2 method was compared with the Soxhlet method, it was seen that the fast and eco-friendly Sc-CO2 method was an ideal extraction method by providing 76.89% rutin and 44.53% apigenin recoveries. As a result of this study, the maximum extraction conditions for rutin and apigenin were obtained as 160 bar, 40 °C, 0.35 mm particle size, 3 l/min CO2, 8% w/w co-solvent ratio, and 120 min extraction period.Graphical abstract Supplementary InformationThe online version contains supplementary material available at 10.1007/s12161-021-02136-8.

Optically transparent bio‐based polyamides with microcellular foaming properties derived from renewable difunctional aminoamides

AbstractA green approach for the synthesis of bio‐based polyamides (PAs) with a new macromolecular structure was developed. These bio‐based PAs were synthesized by solvent and catalyst‐free polycondensation combining fatty dimer acid Pripol™ 1009 with new difunctional aminoamides (DAAs). The later DAAs building blocks were synthesized by aminolysis of renewable dimethyl sebacate (DMS) and dimethyl adipate (DMA) with three different aliphatic diamines having diverse chain lengths, 2, 4, and 6 carbons. Bio‐based PAs showedMwup to 30,581 g/mol, initial thermal degradation over 380°C,Tmfrom 168.3–202.4°C,Tgfrom 28.3–37.5°C, strain from 36.4 ± 4.0–313.5 ± 2.0%, and tensile strength up to 27.4 ± 0.1 MPa. Interestingly, all the PAs films had excellent optical transparency with cut‐off wavelengths of 276.0–283.0 nm, transmittance from 82.7%–90.7% at 600 nm. As a proof‐of‐concept of their usage, one of the PA was shown to be form microcellular foam by the green scCO2method. The foams possessed uniform (cell size; 40 μm, foam density; 0.265 g/cm3, expansion rate; 7.2) and bimodal (cell size; 24/38 μm, foam density; 0.302 g/cm3, expansion rate; 6.5) cell textures depending on their foaming temperatures. This is the first report of bio‐based PA foams and transparent films manufacturing without toxic solvents.

Sustained release ketamine-loaded porous silicon-PLGA microparticles prepared by an optimized supercritical CO2 process.

Ketamine in sub-anaesthetic doses has analgesic properties and an opioid-sparing effect. Intrathecal (i.t.) delivery of analgesics bypasses systemic metabolism and delivers the analgesic agent adjacent to the target receptors in the spinal cord and so small doses are required to achieve effective pain relief. In order to relieve intractable cancer-related pain, sustained-release ketamine formulations are required in combination with a strong opioid because frequent i.t. injection is not practical. In this study, ketamine or ketamine-loaded porous silicon (pSi) were encapsulated into poly(lactic-co-glycolic acid) (PLGA) microparticles by a novel supercritical carbon dioxide (scCO2) method, thereby avoiding the use of organic solvent. Multiple parameters including theoretical drug loading (DL), presence of pSi, size of scCO2 vessel, PLGA type, and use of co-solvent were investigated with a view to obtaining high DL and a sustained-release for an extended period. The most important finding was that the use of a large scCO2 vessel (60mL) resulted in a much higher encapsulation efficiency (EE) compared with a small vessel (12mL). In addition, pre-loading ketamine into pSi slightly improved the level of drug incorporation (i.e. EE and DL). Although the in vitro release was mainly affected by the drug payload, the use of the large scCO2 vessel reduced the burst release and extended the release period for PLGA microparticles with 10% or 20% ketamine loading. Together, our findings provide valuable information for optimization of drug delivery systems prepared with the aid of scCO2.

The PLGA Microspheres Synthesized by a Thermosensitive Hydrogel Emulsifier for Sustained Release of Risperidone

Risperidone is an important antipsychotic agent used for treatment of both acute and chronic schizophrenia. The drug has been effective in resolving the disease’s signs while keeping extrapyramidal side effects as low as possible. To achieve a sustained and gradual release of risperidone from PLGA microspheres, we utilized an emulsifying agent; PLGA-PEG-PLGA triblock (M-triblock), instead of PVA (M-PVA), applying ring-opening polymerization of the triblock via supercritical carbon dioxide (scCO2). PVA and PLGA-PEG-PLGA (as emulsifiers) were successfully employed to prepare risperidone-loaded PLGA microspheres. The scCO2 and microwave irradiation methods were used to construct PLGA-PEG-PLGA copolymers. The microspheres were subjected to various analyses to determine the particles’ sizes, morphological characteristics, and structure (via XRD) and in vitro drug release kinetics. Drug loading capacity and encapsulation percentage were also determined. The results showed a mean diameter of 43.34 ± 2.30 µm for M-PVA, and that of the M-triblock was 57.49 ± 1.21 µm. Risperidone encapsulation percentages were 72.8 ± 2.09 for M-PVAs and 73.4 ± 2.41 for the M-triblock. Particle size, risperidone distribution, and drug loading and encapsulation percentages were similar between M-PVAs and the M-triblock. In scanning electron microscopy (SEM), the morphology of the triblock emulsifier was more uniform than PVAs. The triblock emulsifier showed slower initial drug release than PVAs due to the precipitation of the triblock hydrogel around PLGA microspheres. Overall, the triblock used here can be a good alternative to PVA.

Extraction lipids from chlorella vulgaris by supercritical CO2 for biodiesel production

This study investigated the impact of supercritical CO2 lipid extraction method (SCCO2) from Chlorella vulgaris microalgae for biodiesel production. In this research Chlorella vulgaris oil extracted using SCCO2 and conventional solvent (n-hexane and ethanol). Extraction method was carried out using high pressure CO-solvent the extraction experiments were conducted at (12L: 12D) light/dark regime in 8 treatments, including: T1 (without any shock), T2 (acidity shock, pH:11), T3 (salinity shock, 1 molar NaCl), T4 (nutritional shock, depletion of nutrition), T5 (acidity+salinity shock), T6 (acidity+nutritional shock), T7 (salinity+nutritional shock) and T8 (acidity+salinity+nutritional shock). For each experiment used 10 g algae biomass. The results of growth performance indicated that different medium conditions such as salinity, acidity and nutritional terms with light and dark time shocks can enhanced the Chlorella vulgaris biomass productivity (SGR (0.17±0.00), biomass productivity (0.34±0.05) and CO2 consumption rate (629.97±34.62). The major FAME profile of the obtained oils were (C16:0) palmitic, (C18:0) Stearic, (C22:1n9) ercucic, (C24:1n9) nervonic, (C22:6n3) DHA and (C20:3n3) eicosatrieonoic acids. The measured saponification value (SV) and iodine value (IV) showed no significant differences between the experimental samples (P<0.05). The best results of cetane number (CN) and degree of unsaturation (DU) values was recorded in TL7 (5062.04±23.14) and TL8 (40.93±1.20), respectively. At least, fatty acids content and lipid extracted by SCCO2 method under different pressure and temperature had the best results in 370 bar and 40 °C, while lowest restitution was seen in 200 bar and 40 °C, respectively. The results of this study illustrated that SCCO2 method had positive impact on oil extraction from Chlorella vulgaris had desirable properties.

Recent Progress in Waterless Textile Dyeing

Two new processes of waterless textile dyeing known as air-dye and supercritical carbon dioxide (scCO2) assisted dyeing is reviewed and discussed. The conventional textile dyeing industries use freshwater as a solvent and drain them as wastewater. Each year trillions of freshwater and over ten thousand dyes and pigments are used globally. The wastewater from these industries is dumped into the surrounding lakes, agricultural fields, rivers, etc. The impact of textile dyeing is therefore significant because it decreases the freshwater level and polluting the surface water unceasingly. Thus, from decades, researchers have tried to develop a technology that is waterless and pollution-free. Because of researcher’s tremendous efforts, two such waterless dyeing method is in our hand now. These processes have multiple advantages over conventional techniques, such as emission of less waste and less greenhouse gases, shorter operating time, less energy consumption, etc. Moreover, they have good diffusivity, readily available, reusable, non-flammable and non-toxic, making the process economically feasible and environmentally attractive. Several textile converters in Europe, Asia and North America currently use AirDye. scCO2 method has gained the attention of brands such as Nike, Adidas and IKEA, all of whom have used this process to dye their own products. With versatile advantages, there are some drawbacks. Such as the dyeing is only applicable to synthetic fabrics like polyester and the installation of machines are relatively expensive. In this report, the current status of research and development on resolving several issues like this is also summarized.

Preparation of phthalocyanine green nano pigment using supercritical CO2 gas antisolvent (GAS): experimental and modeling

Phthalocyanine green nano pigment was prepared using supercritical gas antisolvent (GAS) process based on the SC-CO2 method. Thermodynamic models were developed to study the volume expansion and operating conditions of the GAS process. Peng-Robinson EoS were applied for binary (CO2 and DMSO) and ternary (CO2, DMSO, and pigment) systems. A Box–Behnken experimental design was used to optimize the process. Influences of temperature (308, 318 and 328 K), pressure (10, 15 and 20 MPa) and solute concentration (10, 40 and 70 mg/mL) were studied on the particles size and their morphology. The fine particles produced were characterized by SEM, DLS, XRD, FTIR and DSC. Experimental results showed a great reduction in size of pigment particles in comparison to the original particles. The mean particle sizes of nanoparticles were obtained to 27.1 nm after GAS based on SC-CO2 method.

Supercritical Carbon Dioxide Extraction of Malaysian Stingless Bees Propolis: Influence of Extraction Time, Co-modifier and Kinetic Modelling

In the present work, the influence of extraction time and co-modifier on the yield of two types of MSB propolis, hard and sticky, using supercritical carbon dioxide extraction technique were evaluated. Different pressure, CO2 flowrate and co-modifier percentage was studied at constant 40°C. SCCO2 extraction was carried out at high (25MPa, 5 ml min−1 CO2, 7% ethanol) and low (15MPa, 3 ml min−1 CO2, 3% ethanol) operating conditions for both hard and sticky MSB propolis. The result shows that 240 minutes was the best and efficient extraction time. Meanwhile, at high operating condition in SCCO2 technique has increased extraction yield of 1.1608g and 0.5656g for both hard and sticky MSB propolis with the addition of co-modifier. Extraction yield without co-modifier addition was 0.3602g and 0.0542g for hard and sticky MSB propolis, respectively. Co-modifier addition to the process had increase the extraction yield as much as 10 folds higher for sticky MSB propolis whilst, 3 folds higher for hard MSB propolis. These findings show that SCCO2 method propose a feasible technique for MSB propolis extraction as it only require short extraction time and complemented with co-modifier application. Brunner and Esquivel model were used to determine the kinetic behaviours in the extraction process. The maximum extraction rate found was 3×10−4 g sec−1 from the fitting the kinetic models.