Supercritical extraction of carob kibbles (Ceratonia siliqua L.)

Carob pulp kibbles, a by-product of carob been gum production, was studied as a source of bioactive agents. Firstly, the carob kibbles were submitted to an aqueous extraction to extract sugars, and supercritical fluid extraction (SFE) was applied to the solid residue of that aqueous extraction, by using compressed carbon dioxide (SC-CO₂) as the solvent and a mixture of ethanol and water (80:20, v/v) as a co-solvent. Pressure and temperature were studied in the ranges 15–22 MPa, and 40–70 °C. Particle diameter, and co-solvent percentage in ranges of 0.27–1.07 mm, and 0–12.4%, respectively, were also studied, as well as the flow rate of SC-CO₂ between 0.28 and 0.85 kg h⁻¹, corresponding, respectively, to 0.0062 and 0.0210 cm s⁻¹ of superficial velocity. The extracts were characterised in terms of antioxidant capacity by DPPH method, and total phenolics content by the Folin–Ciocalteu method. The central composite non-factorial design was used to optimise the extraction conditions, using the Statistica, version 6 software (Statsoft). The best results, in terms of yield and antioxidant capacity, were found at 22 MPa, 40 °C, 0.27 mm particle size, about 12.4% of co-solvent and a flow rate of 0.29 kg h⁻¹ of SC-CO₂. The phenolics profile of the extracts obtained at these conditions was qualitatively evaluated by HPLC-DAD. The solid residue of the supercritical extraction was also studied showing to be a dietary fiber, which can be compared to Caromax™, a carob fiber commercialised by Nutrinova Inc.     

Determination and calculation for solubility of m-nitroaniline and its mixture in supercritical carbon dioxide

Equilibrium solubility of m-nitroaniline and p-nitroaniline in supercritical carbon dioxide (SCCO₂) is essential to design the process of SCCO₂ extraction and to investigate the effect of each solute on the solubility in SCCO₂ ternary system. However, the solubility data is not reported so far. We performed the solubility measurements at the temperatures of 308–328 K and in the pressure range of 11.0–21.0 MPa. The experimental results showed the solubility of m-nitroaniline and p-nitroaniline was enhanced in m-nitroaniline + p-nitroaniline + SCCO₂ ternary system. The improvement factor (i), separation factor (μ) and separation efficiency (HE) in the ternary system were defined and calculated, and the best separation result could be obtained at 21.0 MPa and 328 K using SCCO₂ extraction, where the separation efficiency was up to 90.9%. Based on the chemical association theory, a new model was developed to calculate the solubility of mixed solutes in SCCO₂. The correlation result of the new model was tested by about 500 solubility data from 15 kinds of two solutes mixtures in SCCO₂. The correlated result showed that the new model could achieve much better AARD (%) than those of frequently used Sovova and Sovova-T models.     

Response surface optimization of supercritical CO2 extraction of α-tocopherol from gel and skin of Aloe vera and almond leaves

Supercritical fluid extraction (SFE) was studied as an alternative technology in the pharmaceutical industry for the separation of α-tocopherol from gel and skin of Aloe vera and almond leaves. The influence of operating conditions was investigated on the recovery of supercritical carbon dioxide (SC-CO₂) extraction of α-tocopherol from three-year old Aloe vera (Aloe barbadensis Miller) leaf gel. The obtained results were compared with the conventional Soxhlet extraction. Response surface methodology (RSM) was applied to optimize effective variables on the extracted recovery of α-tocopherol. The maximum α-tocopherol recovery of 53.41% from Aloe vera gel was obtained with employing RSM predicted optimal operating conditions of 32 MPa, 45.91 °C, 0.84 ml SC-CO₂/min and 140 min for extraction. The α-tocopherol extraction yield for gel and skin of Aloe vera and almond leaves at these optimal operating conditions were obtained 1.53, 16.29 and 2.61 mg/100 g dry sample, respectively.     

Supercritical fluid extracts from tamarillo (Solanum betaceum Sendtn) epicarp and its application as protectors against lipid oxidation of cooked beef meat

The possibility of using the tamarillo (Solanum betaceum (Cav.) Sendtn (syn. Cyphomandra betacea)) epicarp as source of compounds with antioxidant activity in cooked beef meat (CBM) was explored. Extracts from tamarillo by supercritical fluid extraction (SFE) and Soxhlet extraction (SE) were obtained. The SFE was performed using pure CO₂ at different temperatures and pressures (40 and 50 °C; 10, 20 and 30 MPa) and CO₂ added with ethanol (CO₂/EtOH) as co-solvent (2, 5 and 8%, w/w). The SFE kinetics and mathematical modeling of the overall extraction curves (OEC) were also investigated. EtOH and hexane were used in the SE. The antioxidant activity (AA) of extracts was evaluated in CBM as well as the protection against lipid oxidation was determined by measuring lipid hydroperoxides (LHP) and thiobarbituric acid reactive species (TBARS). The extract obtained by SFE with CO₂/EtOH (50 °C/30 MPa and 2% of EtOH) showed the highest AA. In SFE, the co-solvent addition improved considerably the AA and the extraction yield. The extracts obtained by SFE with CO₂/EtOH showed a better AA compared with the synthetic antioxidant TBHQ. The highest yield values were achieved by SE with ethanol (7.7 ± 0.4%) and by SFE with 5% EtOH (1.9 ± 0.1%). The results indicate that extracts of tamarillo epicarp are a potential source of antioxidant compounds.     

Extraction of phenolic compounds and anthocyanins from blueberry (Vaccinium myrtillus L.) residues using supercritical CO2 and pressurized liquids

This work explored the potential of subcritical liquids and supercritical carbon dioxide (CO₂) in the recovery of extracts containing phenolic compounds, antioxidants and anthocyanins from residues of blueberry (Vaccinium myrtillus L.) processing. Supercritical CO₂ and pressurized liquids are alternatives to the use of toxic organic solvents or extraction methods that apply high temperatures. Blueberry is the fruit with the highest antioxidant and polyphenol content, which is present in both peel and pulp. In the extraction with pressurized liquids (PLE), water, ethanol and acetone were used at different proportions, with temperature, pressure and solvent flow rate kept constant at 40 °C, 20 MPa and 10 ml/min, respectively. The extracts were analyzed and the highest antioxidant activities and phenolic contents were found in the extracts obtained with pure ethanol and ethanol + water. The highest concentrations of anthocyanins were recovered with acidified water as solvent. In supercritical fluid extraction (SFE) with CO₂, water, acidified water, and ethanol were used as modifiers, and the best condition for all functional components evaluated was SFE with 90% CO₂, 5% water, and 5% ethanol. Sixteen anthocyanins were identified and quantified by ultra performance liquid chromatography (UPLC).     

Large relative cooling power of Bi-doped La0.8−xBixSr0.08(Ca0.55Ba0.45)0.12MnO3 (x=0.0, 0.1 and 0.3) perovskites: Magnetic and magnetocaloric properties

We report magnetic and magnetocaloric properties of La_0.8−xBi_xSr_0.08(Ca_0.55Ba_0.45)_0.12MnO₃ (x=0.0, 0.1 and 0.3) perovskite manganites. Polycrystalline samples have been synthesized in air by the sol gel method at a sintering temperature of 1150 °C. Powder X-ray diffraction data show that samples are phase pure and their cell parameters slightly decrease with increase in Bi content. Scanning electron micrographs show that the average particle size increases with increase in Bi content. The temperature dependent magnetization measurements show that the Curie temperatures decrease from 315 K (x=0.0) to 140 K (x=0.3) with increase in Bi content. The isothermal magnetization data is used to estimate the magnetic entropy changes (−$\Delta S_M$) and their calculated values are 1.12 J kg⁻¹ K⁻¹, 1.96 J kg⁻¹ K⁻¹ and 1.62 J kg⁻¹ K⁻¹ for x=0.0, 0.1 and 0.3 samples respectively under an applied magnetic field of 2.0 T. The corresponding values of relative cooling power (RCP) are 90 J kg⁻¹, 180 J kg⁻¹, 136 J kg⁻¹ for x=0.0, 0.1 and 0.3 samples respectively. These results of magnetocaloric effect in our samples suggest that they are promising materials for the magnetic refrigeration applications.     

Supercritical carbon dioxide extraction of Gac oil

Supercritical carbon dioxide extraction of Gac (Momordica cochinchinensis Spreng) aril was performed at pressures ranging from 200 to 400 bar, temperatures from 313 to 343 K and specific flow rates from 50 to 90 kg h⁻¹ CO₂ kg⁻¹ Gac aril. Total oil recovery and carotenes concentration were investigated in the course of extraction. Mathematical modelling of oil solubility data was also performed. The results showed that at specific flow rate of 70 kg h⁻¹ kg⁻¹, pressure of 400 bar and temperature of 343 K, Gac oil recovery exceeded 95% after 120 min of extraction. Gac oil loading of supercritical carbon dioxide was successfully described by Chrastil's model. Carotenes concentration of extracted Gac oil was found at level of thousands of ppm.     

Optimization of the supercritical fluid coextraction of oil and diterpenes from spent coffee grounds using experimental design and response surface methodology

The reported work aimed at the optimization of operating conditions of the supercritical fluid extraction (SFE) of spent coffee grounds (SCG) using pure or modified CO₂, with particular emphasis on oil enrichment with diterpenes like kahweol, cafestol and 16-O-methylcafestol. The analysis comprised the application of Box–Behnken design of experiments and response surface methodology, and involved three operating variables: pressure (140–190 bar), temperature (40–70 °C) and cosolvent (ethanol) addition (0–5 wt.%). The best conditions to maximize total extraction yield are 190 bar/55 °C/5 wt.% EtOH, leading to 11.97% (g_oil/100 g_SCG). In terms of the concentration of diterpenic compounds in the supercritical extracts, the best operating conditions are 140 bar/40 °C/0 wt.% EtOH, providing 102.90 mg g⁻¹_oil. The measurement of extraction curves near optimized conditions (140 bar/55 °C/0 wt.% EtOH and 190 bar/55 °C/0 wt.% EtOH) confirmed the trends of the statistical analysis and revealed that SFE enhances diterpenes concentration by 212–410% at the expenses of reducing the extraction yield between 39% and 79% in comparison to n-hexane extraction.     

Application of response surface methodology for the optimization of supercritical carbon dioxide extraction and ultrasound-assisted extraction of Capparis spinosa seed oil

Caper (Capparis spinosa) seed oil growing wild in Iran was extracted using supercritical CO₂ and ultrasound-assisted extraction methods. The experimental parameters of SFE and UAE were optimized using a rotatable central composite design. The highest yield for SFE was obtained at a pressure of 355 bar, temperature of 65 °C, modifier volume of 140 μL, static and dynamic extraction time of 10 and 35 min, respectively, and for UAE was gained at solvent volume of 23 mL, sonication time of 45 min and temperature of 40 °C. This resulted in a maximum oil recovery of 25.1% and 27.9% for SFE and UAE, respectively. The extracts with higher yield from both methods were subjected to transesterification and GC–MS analysis. SFE and UAE processes selectively extracted the fatty oils with high percentage of omega-6 and omega-9-fatty acids. The major components of the extracted oils from both methods were linoleic, oleic, its positional isomer cis-vaccenic and Palmitic acid.     

Extraction of curcuminoids from deflavored turmeric (Curcuma longa L.) using pressurized liquids: Process integration and economic evaluation

Pressurized liquid extraction (PLE) of curcuminoids from deflavored turmeric rhizomes was optimized. The rhizomes were initially deflavored by extraction with supercritical CO₂. Immediately after SFE, PLE process was performed using ethanol as the solvent and a static extraction time of 20 min, and the independent variables were the temperature (333–353 K) and pressure (10–35 MPa). The results indicate that the optimum extraction temperature and pressure were 333 K and 10 MPa, respectively. PLE required three and six times less extraction time than low-pressure solvent extraction and Soxhlet extraction, respectively, to produce similar extraction yields. The cost of manufacturing (COM) decreased from US$ 94.92 kg⁻¹ to US$ 88.26 kg⁻¹ when the capacity of the two-extractor system increased from 0.05 m³ to 0.5 m³ and from US$ 94.92 kg⁻¹ to US$ 17.86 kg⁻¹ when the cost of the raw materials decreased from US$ 7.91 kg⁻¹ to US$ 0.85 kg⁻¹ for a two 0.05 m³ extractor system.     

Measurement and correlation of quaternary solubilities of dihydroxybenzene isomers in supercritical carbon dioxide

The equilibrium quaternary solubilities of dihydroxybenzene (resorcinol + pyrocatechol + hydroquinone + SCCO₂) isomers were experimentally determined at 308, 318 and 328 K over a pressure range of 9.8–15.7 MPa by using a saturation method. The effects of temperature, pressure and the components on each other have been thoroughly investigated. The selectivity of SCCO₂ for ternary (resorcinol + pyrocatechol + SCCO₂) and quaternary systems was discussed. A new model equation for quaternary solubilities of solids has been developed by accounting for non-idealities by combining the solution model with Wilson activity coefficient model. The model equation has five adjustable parameters and correlates the quaternary solubilities of current data along with two other quaternary data reported in the literature.     

Structure and dielectric properties of perovskite ceramics in the system Ba(Ni1/3Nb2/3)O3–Ba(Zn1/3Nb2/3)O3

Ceramics in the system Ba(Ni_1/3Nb_2/3)O₃–Ba(Zn_1/3Nb_2/3)O₃ (BNN–BZN) were prepared by the mixed oxide route. Powders were mixed and milled, calcined at 1100–1200 °C then pressed and sintered at temperatures in the range 1400–1500 °C for 4 h. Selected samples were annealed or slowly cooled after sintering. Most products were in excess of 96% theoretical density. X-ray diffraction confirmed that all specimens were ordered to some degree and could be indexed to hexagonal geometry. Microstructural analysis confirmed the presence of phases related to Ba₅Nb₄O₁₅ and Ba₈Zn₁Nb₆O₂₄ at the surfaces of the samples. The end members BNN and BZN exhibited good dielectric properties with quality factor (Qf) values in excess of 25,000 and 50,000 GHz, respectively, after rapid cooling at 240 °C h⁻¹. In contrast, mid-range compositions had poor Qf values, less than 10,000 GHz. However, after sintering at 1450 °C for 4 h and annealing at 1300 °C for 72 h, specimens of 0.35(Ba(Ni_1/3Nb_2/3)O₃)–0.65(Ba(Zn_1/3Nb_2/3)O₃) exhibit good dielectric properties: τ_f of +0.6 ppm °C⁻¹, relative permittivity of 35 and quality factor in excess of 25,000 GHz. The improvement in properties after annealing is primarily due to an increase in homogeneity.     

Novel micromesoporous carbon materials synthesized from tantalum hafnium carbide and tungsten titanium carbide

Nanostructured carbide-derived carbons (CDC) were synthesized from Ta₄HfC₅ and WTiC₂ powders via gas phase chlorination within the temperature range from 800 to 1100 °C. The results of X-ray diffraction, high-resolution transmission electron microscopy and Raman spectroscopy showed that the synthesized CDC materials are mainly amorphous, containing relatively small graphitic crystallites. The scanning electron microscopy data revealed the breaking down of the initial carbide particles into smaller ones. The low-temperature N₂ sorption experiments were performed and the specific micropore surface areas up to 1950 m² g⁻¹ and 1880 m² g⁻¹ were obtained for Ta₄HfC₅-CDC and WTiC₂-CDC, respectively. The energy-related properties of the supercapacitors based on 1 M (C₂H₅)₃CH₃NBF₄ solution in acetonitrile and Ta₄HfC₅-CDC or WTiC₂-CDC as an electrode material were investigated using the cyclic voltammetry, electrochemical impedance spectroscopy, galvanostatic charge/discharge and constant power charge/discharge methods. The Ragone plots (using the total material weight or volume of two electrodes) for the supercapacitors based on the Ta₄HfC₅-CDC and WTiC₂-CDC electrodes have been calculated from constant power tests within the potential range from 3.0 to 1.5 V, demonstrating the high gravimetric (28 Wh kg⁻¹) and volumetric (18 Wh dm⁻³) energy densities at high power density (10 kW kg⁻¹ and 15 kW dm⁻³, respectively).     

Extraction of bioactive enriched fractions from Eruca sativa leaves by supercritical CO2 technology using different co-solvents

Supercritical fluid extraction from freeze-dried Eruca sativa leaves is assessed with the aim of studying the feasibility to obtain bioactive enriched fractions containing different classes of valuable compounds. Total extraction yields and compositions using pure CO₂ and CO₂ + selected co-solvents are compared. Overall extraction curves, fitted by the model of broken and intact cells developed by Sovová, are reported and the influence of the main parameters that affect the extraction process is analysed. The extract with the highest content in glucosinolates and phenols was collected at 30 MPa and 75 °C using 8% (w/w) of water with respect to the CO₂ flow rate, whereas the fraction richest in lipids was obtained using 8% (w/w) of ethanol as co-solvent at 45 °C and 30 MPa. A process including a first step with supercritical CO₂ extraction using water as co-solvent followed by a second step, where a fraction rich in lipids is extracted using ethanol as co-solvent, is proposed. SCCO₂ results are compared with Soxhlet and other methods that combine organic solvents with ultrasounds.     

Enrichment of Nigella damascena extract with volatile compounds using supercritical fluid extraction

β-Elemene, germacrene A and damascenine were extracted from lady-in-a-mist (Nigella damascena L.) seeds with supercritical carbon dioxide at 10–30 MPa and 40–60 °C. The influence of supercritical fluid extraction (SFE) conditions on the yield and concentration of volatiles in the extract and the extraction kinetics were studied. The extraction yields and the apparent solubility of volatile compounds increased with increasing density of CO₂. The highest total yield was obtained at 30 MPa and 40 °C but the selectivity for volatiles was low under these conditions. With respect to both yield of volatiles and their concentration in extract, the best results were at 12 MPa and 40 °C, either with one separator or with additional separator maintained at 5 MPa and 25 °C. The yields of β-elemene, germacrene A and damascenine reached 0.72, 3.31 and 3.65 mg g⁻¹ and their concentration in the extract was 2.62, 12.04 and 13.28 wt.%, respectively. Though the yields of germacrene A and damascenine were by about 20% higher using Soxhlet extraction with hexane than using SFE, their concentration in the extract where fatty oil prevailed was only 1.19 and 1.20 wt.%, respectively. Under the conditions of hydrodistillation, partial conversion of germacrene A to β-elemene occurred and its yield was higher than using the other methods but the composition of volatiles in the SFE extracts better corresponds to the original raw material.     

Production of polyphenol extracts from grape bagasse using supercritical fluids: Yield,extract composition and economic evaluation

The objective of this work was to determine the economic feasibility of large-scale operations of supercritical fluid extraction (SFE) for the recovery of phenolics using grape bagasse from Pisco residues. Experimental data were used to estimate the extraction kinetic parameters, as well as the cost of manufacturing the extracts. Experimental data were obtained using supercritical CO₂ containing 10% ethanol (w/w) at 313 K and 20–35 MPa. The supercritical CO₂/ethanol extraction process produced extracts with higher concentrations of phenolics than extracts produced using conventional techniques. The compounds identified in the extracts were syringic, vanillic, gallic, p-hydroxybenzoic, protocatechuic and p-coumaric acids, as well as quercetin. An evaluation of the economics of the process indicated the feasibility of an industrial SFE plant with a capacity of 0.5 m³ for producing an extract with an expected phenolics concentration of approximately 23 g/kg of extract at an estimated cost of manufacturing of US$ 133.16/kg.     

Sulfonated-polysulfone membrane surface modification by employing methacrylic acid through UV-grafting: Optimization through response surface methodology approach

Membrane surface modification through UV-grafting method was studied and optimized using response surface methodology (RSM) approach. Sulfonated-polysulfone (SPS) membrane was modified through grafting process by employing methacrylic acid (MAA) monomer solution under the exposure of UV light. The parameters used were the concentration of MAA in the range of 0–6 wt% and UV activation time of 0–50 min. The optimized parameters from RSM were 2.61 wt% of MAA and 21.10 min of UV activation time. The optimized water permeability obtained was 8.75 L m⁻² h⁻¹ bar⁻¹, while the rejection percentages for humic acid, NaCl and MgSO₄ solution were 95.0%, 65.7% and 48.3%, respectively.     

High-surface area carbons from renewable sources with a bimodal micro-mesoporosity for high-performance ionic liquid-based supercapacitors

Highly porous materials with a bimodal pore size distribution in the micro-mesopore range have been produced from biomass by adding melamine to the hydrochar/KOH mixture used in the activation process. These carbons are characterized by BET surface areas in excess of ∼3300 m² g⁻¹ and a porosity equally distributed between micropores and mesopores. The use of melamine in the synthesis process not only extends the pore size distribution into the mesopore region, but leads to the incorporation of a certain amount of nitrogen atoms into the carbon framework. These materials combine high ion adsorption capacities (micropores) and enhanced ion-transport kinetics (mesopores) leading to an outstanding capacitive performance in ionic liquid-based supercapacitors. Thus, they have specific capacitances >160 F g⁻¹ at 1 A g⁻¹ and >140 F g⁻¹ at 60 A g⁻¹ in both pure ionic liquid and in acetonitrile-diluted ionic liquid, enabling these materials to store up to a maximum of ca. 60 W h kg⁻¹ in both kinds of electrolytes and deliver ca. 20 W h kg⁻¹ at ∼42 kW kg⁻¹ (discharge time ca. 2 s) in pure ionic liquid and ∼25–30 W h kg⁻¹ at ∼97–100 kW kg⁻¹ (discharge time ∼1 s) in acetonitrile-diluted ionic liquid.     

Development of a continuous dense gas process for the production of liposomes

A new process called Continuous Anti-Solvent (CAS) process was developed for the production of liposomes using supercritical CO₂. Unlike the current dense gas technologies, CAS method is a single step and continuous process. Preliminary experiments were conducted in semi-batch mode to determine the most suitable operating conditions (stirring speed = 225 rpm; water/lecithin mass ratio = 21) to ensure an efficient phase mixing in the autoclave. Then, two procedures were developed for the CAS process in the continuous mode. According to the results, the single exit procedure enhances the phase mixing in the autoclave with the formation of a CO₂-in-water emulsion which is a good precursor to liposome formation. Liposomes prepared with the CAS method (P = 9 MPa; T = 308 K; CO₂ flow rate = 0.3 kg h⁻¹; organic solution flow rate = 240 mL h⁻¹; water flow rate = 180 mL h⁻¹) are spherical and multilamellar with a medium diameter included between 10 and 100 μm.