Supercritical Carbon Dioxide Treatment Research Articles

Influence of Microwave-Assisted Supercritical Carbon Dioxide Treatment on the Pore Structure of Low-Rank Coal

Influence of Microwave-Assisted Supercritical Carbon Dioxide Treatment on the Pore Structure of Low-Rank Coal

Effect of supercritical carbon dioxide on protein structure modification and antimicrobial peptides production of Mongolian cheese and its in vitro digestion

The aim of this research was to investigate the effects of supercritical carbon dioxide (SC-CO2) treatment on protein structure in Mongolian cheese. The peptides during the digestive process of the SC-CO2 treated cheese were also studied. SC-CO2 technology was utilized to treat Mongolian cheese at three temperatures (45, 55 and 65 °C) and three pressures (7.5, 12.5 and 17.5 MPa). The results of fluorescence, ultraviolet–visible, Fourier transform infrared spectroscopy and free sulfhydryl groups showed that SC-CO2, particularly at 65 °C and 17.5 MPa, modified the protein structure in Mongolian cheese effectively. The data of LC-MS/MS-based peptidomics showed that the content of antimicrobial peptides found in the SC-CO2 treated Mongolian cheese was 1.55 times that of the untreated Mongolian cheese; the content of unique antimicrobial peptides in the digested SC-CO2 treated Mongolian cheese was 1.46 times that of the digested untreated Mongolian cheese, which proved that SC-CO2 could help produce antimicrobial peptides in cheese not only during the process of SC-CO2 treatment but during subsequent simulated gastrointestinal digestion as well. In conclusion, SC-CO2 could be considered a promising method to develop cheese products with potential health benefits.

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications.

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Quality properties and nutritional compounds of fresh-cut pumpkin treated with supercritical carbon dioxide

The work aimed to explore the effect of supercritical carbon dioxide (SCCD) treatment on the enzyme activity, color, carotenoid, sugar and phenolic profile, and antioxidant activity of fresh-cut pumpkins. The polyphenol oxidase (PPO) and peroxidase (POD) activities of SCCD-treated pumpkin cubes were reduced by 21% and 18%, respectively. The lightness value of SCCD-treated samples declined compared to the untreated samples, whereas the redness and yellowness values in treated samples were enhanced. The lutein, α-carotene, β-carotene and total carotenoids, glucose, sorbitol, and other polysaccharides in the SCCD-treated samples showed a fluctuation trend. Similarly, the treated sample's total phenolic contents (TPC), ABTS (2,2′- azino-bis(3-ethylbenzothiazoline-6-sulfonic acid, DPPH (2,2-diphenyl-1-picrylhydrazyl), and superoxide radical scavenging activities were increased and then reduced. An enhancement was noted in the coumaryloquinic acid I and II, caffeic acid glucoside, 4-hydroxybenzoic acid, and p-coumaric acid of SCCD-treated samples. The work demonstrated that the SCCD technique at moderate conditions could obtain higher retention of nutritional composition in fresh-cut pumpkins.

Effects of Gamma Irradiation and Supercritical Carbon Dioxide Sterilization on Methacrylated Gelatin/Hyaluronan Hydrogels.

Biopolymer hydrogels have become an important group of biomaterials in experimental and clinical use. However, unlike metallic or mineral materials, they are quite sensitive to sterilization. The aim of this study was to compare the effects of gamma irradiation and supercritical carbon dioxide (scCO2) treatment on the physicochemical properties of different hyaluronan (HA)- and/or gelatin (GEL)-based hydrogels and the cellular response of human bone marrow-derived mesenchymal stem cells (hBMSC). Hydrogels were photo-polymerized from methacrylated HA, methacrylated GEL, or a mixture of GEL/HA. The composition and sterilization methods altered the dissolution behavior of the biopolymeric hydrogels. There were no significant differences in methacrylated GEL release but increased methacrylated HA degradation of gamma-irradiated samples. Pore size/form remained unchanged, while gamma irradiation decreased the elastic modulus from about 29 kPa to 19 kPa compared to aseptic samples. HBMSC proliferated and increased alkaline phosphatase activity (ALP) particularly in aseptic and gamma-irradiated methacrylated GEL/HA hydrogels alike, while scCO2 treatment had a negative effect on both proliferation and osteogenic differentiation. Thus, gamma-irradiated methacrylated GEL/HA hydrogels are a promising base for multi-component bone substitute materials.

Investigating the Effect of Supercritical Carbon Dioxide Treatment on the Rheological, Thermal, and Functional Properties of Plum (Prunus domestica L.) Kernel Protein Isolates

Plum kernels are a promising source of dietary proteins that are irretrievably lost during processing. The recovery of these underexploited proteins could be eminently vital for human nutrition. Plum kernel protein isolate (PKPI) was prepared and exposed to a targeted supercritical carbon dioxide (SC-CO2) treatment to diversify its effectiveness in industrial applications. The impacts of SC-CO2 treatment at different processing temperatures (30-70 °C) on dynamic rheology, microstructure, thermal, and techno-functional characteristics of PKPI were investigated. The results revealed that the dynamic viscoelastic characteristics of SC-CO2-treated PKPIs showed higher storage modulus, loss modulus, and lower tan δ value than native PKPI, indicating greater strength and elasticity of the gels. Microstructural analysis showed that the proteins experienced denaturation at elevated temperatures and resulted in the formation of soluble aggregates, which increased the heat requirement for thermal denaturation of SC-CO2-treated samples. SC-CO2-treated PKPIs demonstrated a decline of 20.74% and 30.5% in crystallite size and crystallinity. PKPIs treated at 60 °C showed the highest dispersibility, which was 1.15-fold higher than the native PKPI sample. SC-CO2 treatment offers a novel path to improve the techno-functional properties of PKPIs and extend its use in food and non-food applications.

Supercritical carbon dioxide treatment of plum (Prunus domestica L) kernel protein isolate: Impact on structural, thermal, physical, and functional properties

The effects of supercritical carbon dioxide (SC–CO2) treatment at varying processing temperatures (30–70 °C) on the physicochemical, structural, thermal, and functional properties of plum kernel protein isolate (PKPI) were investigated. The results revealed that SC-CO2 treatment at 60 °C reduced α-helical content (67.82%) and increased the β-sheet content (33.15%), which resulted in the greater stabilization of the oil-water emulsion (1.29-fold), enhanced foaming capacity (2.08-fold) and improved the solubility (1.23-fold). The fluorescence quenching in SC-CO2 treated PKPIs confirmed the conformational change in protein structure. A significant variation in denaturation temperatures (74.53–66.20 °C) and enthalpy values (133.16–93.98 J/g) of SC-CO2 treated PKPIs, indicates protein denaturation and the formation of new intermolecular bonds between proteins molecules. Furthermore, SC-CO2 treatment reduced the particle size and exerted a greater homogeneity, thereby offering new opportunities to extend its use in food applications.

Structural modification of plum (Prunus domestica L) kernel protein isolate by supercritical carbon-dioxide treatment: Functional properties and in-vitro protein digestibility

The effect of supercritical carbon dioxide (SC-CO2) treatment at different processing temperatures (30–70 °C) on the physico-functional properties, structural features, and in-vitro digestibility (IVPD) of plum kernel protein isolates (PKPI) was examined. The results revealed remarkable changes in the secondary structures of SC-CO2-treated PKPIs, including a decrease in α-helix proportion, a concomitant increase in β-sheet content, and a considerable variation in random coils and β-turn structures. The temperature rise increased the negative zeta potential to a maximum of 31.35 mV at 60 °C, exhibiting the colloidal stability of PKPI dispersions. SDS-PAGE analysis showed variations in the intensities of protein bands, indicating denaturation and aggregation at higher temperatures. These structural and molecular changes improved water-binding capacity (1.22-fold) and oil binding capacity (1.11-fold), wettability (1.12-fold), and the highest value in all the properties was recorded at 60 °C. Moreover, the highest IVPD value (21.58 %) and a distinguishable colour difference (∆E) of 8.11 was also obtained at 60 °C of the processing temperature. Therefore, SC-CO2 treatment-induced modification of PKPI contributed to the enhanced digestibility and techno-functional properties, which offered new prospects to extend its use in food applications.

Scaffold-based tissue engineering: Supercritical carbon dioxide as an alternative method for decellularization and sterilization of dense materials.

Development of ready-to-use biomaterials and scaffolds is vital for further advancement of scaffold-based tissue engineering in clinical practice. Scaffolds need to mimic 3D ultrastructure, have adequate mechanical strength, are biocompatible, non-immunogenic and need to promote tissue regeneration in vivo. Although decellularization of native tissues seems promising to deliver scaffolds that meet these criteria, adequate decellularization of hard, poorly penetrable and poorly diffusible tissues remains challenging whilst being a very time-consuming process. In this study, a method to decellularize hard, dense tissues using supercritical carbon-dioxide preceded by a freeze/thaw cycle and followed by several washing steps is presented, demonstrating decellularisation efficiency and substantially reduced production/handling time. Additionally, supercritical carbon-dioxide treatment was used as sterilization method, further reducing the time required to produce the final scaffold. Histological evaluation showed that, after fine-tuning of the process, a partially acellular scaffold was obtained, with preservation of glycosaminoglycans and collagen fibers, albeit that the amount of residual dsDNA was still higher then chemically decellularized tissue. Biomechanical properties of the scaffold were similar to the native, non-decellularized tissue. After sterilization with supercritical carbon-dioxide the simulated functional outcome was more similar to native trachea, when compared to sterilization using gamma irradiation. Thus, decellularization and sterilization using supercritical carbon-dioxide with washing steps is an effective method for dense cartilaginous materials, and tuneable to meet different demands in other applications, but further optimization may be required. STATEMENT OF SIGNIFICANCE: Further advancement of the use of tissue engineered tracheal constructs is restricted by the lack of the ideal scaffold. Decellularized trachea is considered a promising scaffold, but the hard, poorly diffusible tissue remains challenging while forming a very time consumable process. Decellularization using supercritical carbon dioxide (scCO2) seems promising, resulting in efficient removal of cellular material while reducing production and handling time. Addition of scCO2 as a sterilization method resulted in further time reduction while improving functional outcome in comparison with traditional sterilization methods. This study presents an promising alternative method for decellularization and sterilization of dense materials, which can be tuned to meet different demands in other applications.

Cleaner approach of preparing antibacterial bioaerogel scaffolds using oil palm waste nanocellulose

In this study, cellulose nano fibers (CNF) were isolated from oil palm empty fruit bunch using modified method of supercritical carbon dioxide (ScCO 2 ) treatment of bleached fibers. Bioaerogel scaffolds were prepared from isolated CNF using high-pressure homogenization and freeze-drying techniques. Chitosan (CS) was used to enhance the mechanical properties of bioaerogels, while cinnamon essential oil (CEO) as a natural antibacterial agent and to enhance the biocompatibility of the scaffolds. The results confirm that using ScCO 2 enhanced the yield of CNF isolation and reduced the resulted ash. Scanning Electron Microscopes analysis revealed highly porosity of the bioaerogel architecture that resulted from the excellent homogeneity of the materials. The porosity, density and surface area of the bioaerogels ranged from 90.8% to 99.1%, 8.11–141.2 mg/cm 3 , and 18.7–145.3 m 2 /g respectively. FT-IR analysis confirm the hydrogen bonding between CNFs and CS that enhanced the mechanical properties and reduced the in vitro water up take of the bioaerogels. Although, CEO slightly reduced the hardness and surface area of bioaerogels, it makes the bioaerogels exhibit stronger antibacterial activity against S. aureus and E. coli . CEO also significantly enhanced the proliferation of L929 fibroblast cell compared with pure biopolymeric aerogels. Such novel bioaerogel scaffolds generated from wastes materials have promising potentials in several biomedical applications such as skin regeneration and wound healing. • Nanocellulose from oil palm empty fruit bunch was used to synthesize high porosity bioaerogels scaffolds. • Pure CNF aerogel had the highest porosity, water absorption and surface area. • Chitosan enhanced the mechanical properties of CNF aerogels in addition to reducing its water uptake. • Loading cinnamon essential oil into the aerogel makes it exhibit stronger antibacterial activity and enhanced biocompatibility

Effect of supercritical carbon dioxide on bacterial community, volatile profiles and quality changes during storage of Mongolian cheese

Mongolian cheese was sterilized by using supercritical carbon dioxide (SC–CO2) treatment at three pressures (10, 15 and 20 MPa) and three temperatures (40, 50 and 60 °C). The optimum SC-CO2 condition (20 MPa and 60 °C) could achieve complete inactivation of bacteria. Preservation of Mongolian cheese was assessed at 25 °C for 20 d by analyzing texture, bacterial communities and volatile compounds, after using SC-CO2 (20 MPa and 60 °C). The results indicated that SC-CO2 treatment could maintain texture stability of Mongolian cheese during storage. High throughput sequencing results showed that Clostridium_sensu_stricto and Lysinibacillus were not detected in the SC-CO2 treated cheese and the total abundance of spoilage bacteria in the SC-CO2 treated cheese was much lower than that in untreated cheese after 20 days storage. Nine core functional bacteria such as Clostridium_sensu_stricto, Lysinibacillus, Pseudoclavibacter, Pseudomonas, Acinetobacter, Lactococcus, Aeromonas, Serratia and Buttiauxella that significantly affected the formation of volatile compounds were identified by Spearman correlation analysis. SC-CO2 treatment decreased the contents of volatile compounds (acids and esters) (p < 0.05), avoiding off-flavors development related to the volatile compounds of excess in Mongolian cheese during storage. Overall, SC-CO2 technology could be used as an effective tool to sterilize Mongolian cheese with minimal quality changes.

Evaluation of the biomechanical and structural properties of bone allografts treated with a new cleaning process

The use of allograft bone is becoming increasingly common. The intrinsic mechanical and structural properties of the graft are of major importance for osseointegration. Current cleaning treatments using chemical or physical products increase biosafety but may disturb these bone characteristics. A new cleaning treatment for cancellous and cortical bone by simple mechanical washing (sonication and centrifugation) and supercritical carbon dioxide (scCO2) treatment was developed. The mechanical and structural properties of allografts cleaned with this treatment were compared with those obtained after preservation by freezing at −80°C. Three-point bending, compression and hardness tests were performed for biomechanical analysis. The structural characteristics of the allografts were evaluated by microscanner (histomorphometry) and scanning electron microscopy (surface analysis). All the data showed that the cleaned bone was generally stiffer owing to delipidation but its structure remained similar to that of the frozen bone. Bone cleaned by this new treatment thus displayed mechanical and structural properties close to those of frozen bone.

Effect of supercritical CO2 pre-treatment and kiln-drying of fresh green Pinus radiata sapwood on kiln brown stain and drying stress

High pressure (20 MPa), cyclic, supercritical carbon dioxide (scCO2) treatments can reduce the moisture content of green Pinus radiata sapwood from 150–200% to 35–40%. Such treatments can be used as a dewatering pre-treatment before the kiln-drying of timber. Kiln-drying can utilise various temperature and humidity schedules, targeting around 10% moisture content, with a final stress-relieving steam-conditioning step. After scCO2 treatment and kiln-drying of samples, kiln brown stain was evaluated using the CIE L*a*b* colour space while drying stress was assessed by stress-cup measurements. The most significant results of scCO2 pre-treatment of Pinus radiata sapwood followed by kiln-drying plus steam-conditioning were as follows: Drying from green (36 h from a moisture content (MC) of 164%) using a conventional temperature schedule (90 °C/60 °C) took 2–5 times longer than kiln-drying scCO2 pre-treated boards (37.5% MC) to a target of 10% MC. Colour measurements proved that kiln brown stain does not occur. The use of a steam-conditioning step in reducing internal drying stresses was important irrespective of whether or not there was a scCO2 pre-treatment step. Over all drying schedule combinations, internal drying stress of both green and scCO2 pre-treated timber was similar after kiln-drying plus steam-conditioning. However, using only 90 °C/60 °C schedule data, with steam-conditioning, drying stresses were lower using kiln-drying without the scCO2 pre-treatment. This was surprising since the scCO2 step reduced the moisture content to around 37.5% without significant moisture gradients and so a secondary kiln-drying to 10% moisture content could have been expected to yield lower internal stress levels by preventing large moisture gradients to develop during drying. This result confirms the efficacy of the steam-conditioning step following standard kiln-drying. The colour data demonstrating the prevention of kiln brown stain using kiln-drying schedules offers a path to increasing timber quality for interior applications.

Effect of supercritical carbon dioxide on physicochemical and techno-functional properties of amaranth flour

Amaranth flour is a foodstuff with good quality protein that could be used to manufacture different products. The supercritical carbon dioxide (SC-CO2) treatment allows intensifying the extraction process for obtaining a flour without toxic residues and high-quality oil, replacing the use of organic solvent and reducing the extraction time. In this study, physicochemical and techno-functional properties of amaranth flour (Amaranthus hypochondriacus) defatted with SC-CO2 at different pressure conditions (2900-4350 psi) and temperatures (40-60°C) were determined. It was observed that extraction pressure and temperature had a significant effect (p<0.05) on the extraction yield and protein content, as well as the components present in the flour particles, causing differences in the physicochemical and techno-functional properties. The amaranth flour defatted with SC-CO2 at 50°C/3630 psi was the most outstanding as it had the best extraction performance (70.2 mg oil/g flour), the highest protein content (16.17 g protein/100 g flour), the swelling (SC) (2.263 g H2O/g flour), water absorption (WAC) (126.33 g H2O/100g flour), and oil absorption (OAC) (119.09 g oil/100g flour) capacities, high luminosity (L*) (82.89) and a high total color difference (ΔE*) (5.93). The fatty acid composition of the oils obtained by SC-CO2 showed high content of polyunsaturated fatty acids (PUFA). Physicochemical and techno-functional properties of amaranth flour changed by SC-CO2 treatment, flour defatted by SC-CO2 under intermediate conditions of temperature and pressure (50°C and 3630 psi), was able to produce a high-protein and low-fat amaranth flour as well as with good hydration techno-functional properties, which can be an alternative to defatting process with organic solvents.

Experimental and Simulation of Supercritical Carbon Dioxide PLA Biocomposite Foamed

The use of PLA as a green substitute for conventional plastics has increased considerably as a result of increased awareness of the environmental effect of the use of petroleum-based plastics. However, some of the PLA properties including brittleness and sensitivity to high temperature and humidity, greatly restrict its application. The addition of reinforcement of low-cost natural fibres and foaming are considered to overcome the above disadvantages since it can improve some of PLA’s processing. This paper reported the effects of supercritical carbon dioxide (SCCO2) on the tensile strength of PLA biocomposite films produced via solution casting method. The biocomposite films underwent supercritical carbon dioxide (SCCO2) treatment at temperature of 40°C and pressure at 200 bar. The tensile strength showed that the PLA biocomposite foamed has improved by 16.18%. This is due to a good adhesion interfacial between fiber and polymer matrix. A simulation on tensile strength of the biocomposite foamed was also conducted using COMSOL Multiphysics software. The tensile strength resulted from this simulation is similar to the experimental value. Therefore, the experimental value is valid and satisfy. This also showed that SCCO2 treatment significantly improved the properties of PLA biocomposite films which could be an alternative in packaging industries.

Effect of Supercritical Carbon Dioxide (ScCO2) on the Microstructure of Bituminous Coal with Different Moisture Contents in the Process of ScCO2 Enhanced Coalbed Methane and CO2 Geological Sequestration

Water plays an important role in carbon dioxide (CO2) enhanced coalbed methane exploitation and CO2 geological sequestration at deep geological conditions. We performed mercury intrusion porosimetry, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction analysis on coal samples with different moisture contents after supercritical carbon dioxide (ScCO2) treatment to study the effect of different moisture contents on deep coal seam treatment by ScCO2. Using these experimental techniques, the effects of ScCO2 treatment on the microstructure of coal samples with different moisture contents were obtained. The results showed that the combination of ScCO2 and water in coal samples can cause mineral dissolution, increase the damage degree of coal structural defects, reduce the number of aromatic structures and oxygen-containing functional groups, and then lead to the expansion of the pore and fracture volume, especially the micropore volume. Moreover, with increasing the moisture content, the micropore volume of the coal samples under ScCO2 interaction with the presence of water exhibited an increasing trend. The number of oxygen-containing functional groups in the coal samples decreased. The peak position difference (G – D1) decreased first and then plateaued, and when the moisture content was in the range of 5.85–7.19%, the damage degree reached the maximum. The effect of water and ScCO2 on the dissolution of clay minerals in the coal samples was greater than that on the carbonate minerals.

Rapid fabrication of frescoes using a geomimetic ceramic formation process

Frescoes were developed as religious paintings in medieval Europe before the rise of oil paintings. When coloring with natural pigments on a slaked lime plaster, calcium carbonate gradually forms a coating on the pigments at the surface of the plaster over a period of decades to a hundred years. Many frescoes have been maintained for hundreds of years and have become part of historic heritage. However, the making of frescoes is rarely selected as a general art painting method because it takes a lot of time for complete carbonation to occur. This study demonstrated that a geomimetic ceramic hardening technique using calcium hydroxide and calcium carbonate, followed by subsequent acceleration of carbonation at the surface of the calcium hydroxide with supercritical carbon dioxide, could assist in forming frescoes in a short time. The immobilization of the pigment used on the base calcium hydroxide body was evaluated by a scratch test with emery paper, and pigment color differences were measured by a colorimeter. Furthermore, the micromorphology of the resultant frescoes fabricated by the geomimetic technique in a short time was investigated to evaluate the progress of carbonation. As a result, frescoes could be fabricated in a short time by combining a geomimetic technique and carbonation with supercritical carbon dioxide using a novel pigment that is a mixture of pigment and calcium hydroxide. The pigment in the final sample was completely fixed to the base calcium hydroxide body, and the pigment color was brighter than the original pigment color due to the densification of calcium carbonate after supercritical carbon dioxide treatment.

Extraction and Isolation of Cellulose Nanofibers from Carpet Wastes Using Supercritical Carbon Dioxide Approach.

Cellulose nanofibers (CNFs) are the most advanced bio-nanomaterial utilized in various applications due to their unique physical and structural properties, renewability, biodegradability, and biocompatibility. It has been isolated from diverse sources including plants as well as textile wastes using different isolation techniques, such as acid hydrolysis, high-intensity ultrasonication, and steam explosion process. Here, we planned to extract and isolate CNFs from carpet wastes using a supercritical carbon dioxide (Sc.CO2) treatment approach. The mechanism of defibrillation and defragmentation caused by Sc.CO2 treatment was also explained. The morphological analysis of bleached fibers showed that Sc.CO2 treatment induced several longitudinal fractions along with each fiber due to the supercritical condition of temperature and pressure. Such conditions removed th fiber’s impurities and produced more fragile fibers compared to untreated samples. The particle size analysis and Transmission Electron Microscopes (TEM) confirm the effect of Sc.CO2 treatment. The average fiber length and diameter of Sc.CO2 treated CNFs were 53.72 and 7.14 nm, respectively. In comparison, untreated samples had longer fiber length and diameter (302.87 and 97.93 nm). The Sc.CO2-treated CNFs also had significantly higher thermal stability by more than 27% and zeta potential value of −38.9± 5.1 mV, compared to untreated CNFs (−33.1 ± 3.0 mV). The vibrational band frequency and chemical composition analysis data confirm the presence of cellulose function groups without any contamination with lignin and hemicellulose. The Sc.CO2 treatment method is a green approach for enhancing the isolation yield of CNFs from carpet wastes and produce better quality nanocellulose for advanced applications.

Improvement of water wettability of gray cotton fabric using electron beam irradiation and supercritical CO2 treatment

In this study, the effect of electron beam (EB) and supercritical carbon dioxide (scCO2) treatments on the hydrophilicity of gray cotton pile fabric were investigated. The immersion time, an indicator of the hydrophilicity, was 19 s for a combination of the pre-EB irradiation and the post-scCO2 extraction. In contrast, the values were 13,750–13,990 s after EB irradiation and 65 s post-scCO2 treatment. The addition of a small amount of methanol or polyoxyethylene lauryl ether in scCO2 decreased the immersion time to 4 s or 2 s, which is the water wettability required for a towel product. ATR-FTIR analysis suggested the complete removal of waxy impurities from the gray cotton pile fabric by the combination treatment of EB and scCO2. It was also observed from the FE-SEM images that the visual structure of parallel ridges and grooves covering gray cotton fibers disappeared on fibers with a lower immersion time than 19 s, which suggested dewaxing (the removal of wax). The study reveals that EB irradiation and scCO2 are alternative waterless methods for improving the wettability of gray cotton fabrics.

Supercritical carbon dioxide-based cleaning and sterilization treatments for the reuse of filtering facepiece respirators FFP2 in the context of COVID-19 pandemic

Supercritical Carbon Dioxide treatment of clean and soiled Filtering Face-Piece respirators is shown to meet mandatory requirements for safe reuse of FFP2. Preliminary tests enabled us to select optimal conditions for Supercritical Carbon Dioxide treatment of FFP2, for one hour at 343 K under 7.5 MPa, with a biocide solution. FFP2s from Paul Boyé ® were then tested before and after Supercritical Carbon Dioxide treatment with a soiling solution and a biological indicator (i.e. spores of GeoBacillus stearothermophilus) with respect to three objectives: (i) washing of organic deposits, (ii) sterilization (i.e. spores inactivation) and (iii) preservation of the filtration performances. The proposed Supercritical Carbon Dioxide treatment fulfils these three criterions, with effective decontamination of spores and promising washing preserving FFP2 requirements for filtration efficiency of aerosol (> 94%) with acceptable pressure drop (< 240 Pa). As a simple and low-cost one-step recycling method, Supercritical Carbon Dioxide fits to economical and sustainable development standpoints but also allows one to come back to good practices of face protective equipment use, lowering eventual shortage and tensions for most countries importing these respirators.