Youn-Woo Lee

Seoul National University | SNU · School of Chemical and Biological Engineering

A novel method of determining diffusivity in supercritical carbon dioxide is proposed based on the principle of particle dissolution. The dissolution rate of disperse blue 14 (DB14) was measured by in situ UV-vis spectroscopy and compared with a pseudo-steady-state diffusion-driven dissolution model. By minimizing the error between the experimental...

This work proposes to utilize supercritical CO2 as a reaction medium for the acetylation of Hanji, a traditional Korean cellulose textile, to enhance its water repellency while retaining the other properties. We first examined the phase behavior of acetic anhydride and CO2 mixtures, then a series of experiments were performed and statistically anal...

Purifying diamonds after high-pressure and high-temperature synthesis is essential for their industrial applications, but classical purification methods usually generate a massive amount of toxic liquid wastes or cannot achieve good separation efficiency in a short time. This work proposes to utilize a catalytic supercritical water oxidation proces...

Polyethylene terephthalate (PET) foams were prepared at different saturation temperatures using two supercritical foaming methods. The average cell size, cell number density, and porosity of PET foams obtained using each foaming method were compared. The crystallinity of the PET samples after the saturation step in the two-step foaming process was...

Biodiesel, termed as Fatty Acid Methyl Esters (FAMEs), has an essential role in reducing greenhouse gases by replacing fossil fuel and is needed to be partially hydrogenated to enhance its fuel properties. In this study, biodiesel was synthesized by the simultaneous reaction of transesterification and partial catalytic transfer hydrogenation (CTH)...

A kinetic study of the simultaneous supercritical transesterification and partial hydrogenation (SSTPH) process using soybean oil with Pd/Al2O3 catalyst was conducted. In addition, process design and economic analysis were conducted to investigate the profitability of three different continuous biodiesel production processes, each with a production...

The dissolution behavior of dye in supercritical carbon dioxide influences the overall mass transfer that controls a supercritical dyeing process. Increasing the dissolution rate of the dye leads to shortening of the dyeing process time and can improve the efficiency of the process. Controlling the properties of the carbon dioxide flow is a good me...

Solubility is an essential thermodynamic property that affects the efficiency of the supercritical dyeing process. There are many methods for measuring solubility in supercritical carbon dioxide. However, for substances with low solubility, there is a significant difference between the various methods, and some methods require additional quantitati...

Defatted sesame meal (DSM) is a source rich in glycosylated lignans and bioactive compounds. Hydrothermal (HT) processes with and without added CO2 were applied to recover these bioactive compounds. The extractions were performed from 120 to 180 °C with a solid-to-solvent ratio of 1:20 (w/w). The bioactivities, expressed in terms of the total pheno...

Kinetic study of the thermal conversion of ginsenosides was carried out in steaming, hydrothermal reactions, and CO2-assisted hydrothermal reactions. Since these are complex reactions involving various ginsenosides, the components are divided into three lumped groups according to their structure. Meanwhile, the conventional series reaction model ca...

Waste artificial marble powder (AMP), a composite material of poly(methyl methacrylate) (PMMA) and aluminum tri hydroxide (ATH; Al(OH)3), was recycled using supercritical fluids, in which the depolymerization and thermal decomposition of organic materials and the dehydration of inorganic substances occur simultaneously. For PMMA depolymerization in...

Kinetic study of upgrading extra-heavy oil in supercritical water conditions with and without a zinc nitrate precursor was investigated. Reactions were carried out at 653 K, 673 K, 693 K, and 713 K in a batch reactor. Kinetic parameters including reaction rate constants were calculated based on a phase separation kinetic (PSK) model. Compared to py...

We report the efficiency of green subcritical water extraction (SWE) for the recovery of bioactive compounds from Allium hookeri root (AHR). The highest extraction yield (88 wt%) and highest contents of bioactive compounds including total phenolic content (29.4 mg of gallic acid equivalent/g of dry AHR), total flavonoid content (30.6 mg of querceti...

Mesenchymal stem cells (MSCs) culture fluids are frozen and thawed for long-term storage when needed for medical purposes. However, stresses accompanied with freezing and thawing can disrupt the tertiary structures of proteins, which need to be in a certain state to show their therapeutic effect, by affecting their internal interactions. Supercriti...

Desulfurization of hexyl sulfide and hexanethiol using supercritical water (SCW) was investigated by combining experimental and computational methods to study the desulfurization of alkyl sulfides and thiols in SCW. Desulfurization was conducted for 0 ∼ 30 min at 400 °C using thermal decomposition and SCW decomposition (24.7 ∼ 25.6 MPa), and the re...

This study examined a possibility of commercial Pd/Al2O3, Ni, and Cu as a catalyst for one-pot reaction combining transesterification and partial hydrogenation in supercritical methanol without H2 to produce methyl oleate for bio-refinery or biodiesel with improved fuel quality. The one-pot reaction at different reaction conditions (temperature, pr...

The diffusive behavior of dye molecules in a polymer were typically observed during the impregnation of the dye in a polymer, and this method combines phenomena that occurs in both the fluid and polymer phases. However, the dissolution of the dye in a fluid can cause inadequate resistance in the overall mass transfer, leading to errors in observing...

Synthetic polymer-based gradient foams have considered as promising category of functionally graded materials with unique properties. In this study, the carbon dioxide (CO2) foaming technology has used for PET-PEN (Polyethylene Terephthalate - Polyethylene Naphthalate) copolymer towards porous functional materials with thermal insulation with reaso...

Isomorph theory is one of the promising theories for understanding the quasiuniversal relationship between thermodynamic, dynamic, and structural characteristics. Based on the hidden scale invariance of the inverse power law potentials, it rationalizes the excess entropy scaling law of dynamic properties. This work aims to show that this basic idea...

The structural information of nanomaterials obtained from the microscopy is essential to interpret the crystal morphology, growth, and reaction kinetics. Transmission electron microscopy (TEM) is one of the most popular tools for the characterization of nanomaterials. This study reveals that conventional preparation methods for the TEM analysis lar...

A fluid particle changes its dynamics from diffusive to oscillatory as the system density increases up to the melting density. Hence the notion of the Frenkel line was introduced to demarcate the fluid region into rigid and nonrigid liquid subregions based on the collective particle dynamics. In this work, we apply a topological framework to locate...

The cover image is based on the Review Feasibility of unsaturated fatty acid feedstocks as green alternatives in bio‐oil refinery by Jong Yeol Jeon et al., DOI: 10.1002/bbb.1979. Designed by Kyung Ha Hwang.

Supercritical dyeing proceeds in a sequence of multiple phenomena such as dissolution, adsorption, and diffusion involving different timescales. The aim of this work is to highlight the significant role of the dissolution rates of dyes into the supercritical solution. For this purpose, the dissolution rates of different-sized dyestuffs in the super...

Mesenchymal stem cell (MSC) culture supernatant solutions were dried under sub- and supercritical conditions using the precipitation with compressed antisolvent (PCA) process. Of the supernatant components, vascular endothelial growth factor (VEGF) was selected as the target protein. N-Methyl-2-pyrrolidone (NMP) was used as a co-solvent to enhance...

This work proposes a classification algorithm based on the radical Voronoi tessellation to define the Widom delta, supercritical gas-liquid coexistence region, of polyatomic molecules. Specifically, we use a weighted mean-field classification method to classify a molecule into either gaslike or liquidlike. Classical percolation theory methods are a...

The semiconductor etching process, which is the most important part of the semiconductor manufacturing process, requires higher sophistication as 10 nm semiconductors are mass produced. Etching methods utilizing plasma are getting increasingly popular with the miniaturization of the etching process. As the process performance depends on the state o...

Kinetics of extra heavy oil upgrading in supercritical methanol with and without zinc nitrate hexahydrate as a precursor of a catalyst was studied. The reactions were carried out at 633 K, 653 K, 673 K and 693 K in a batch reactor. Reaction rate constants were calculated based on a four-lumped kinetic model, and activation energy and pre-exponentia...

Bio‐oil contains plant, animal, fish, and micro‐algae oil, and more than 200 million tons are produced annually. However, many edible and non‐edible bio‐oils are still under development, and their value and feasibility have yet to be determined. The vast majority of bio‐oils produced in the world have a very high unsaturated fatty acid content (70–...

In this study, a single paragraph of acrylonitrile-butadiene-styrene (ABS)/recycled polyethylene terephthalate (R-PET) polymeric foams is prepared using CO2 as a blowing agent. First, the sorption kinetics of subcritical and supercritical CO2 are first studied at saturation temperatures from –20 to 40 °C and a pressure of 10 MPa, in order to estima...

Natural gas (NG) is an environment-friendly energy source with low CO 2 and SO x emission. NG is usually liquefied during processing for transportation and storage, and then vaporized before consumption for multiple purposes. Usually, cold energy from the vaporization process is not utilized and hence wasted. One of the means of utilizing the cold...

Isomorph theory is a promising theory to understand the quasi-universal relationship between thermodynamic, dynamic and structural characteristics of simple fluids. This work aims to provide a direct link between the structural characteristics and the transport properties of a system based on the isomorph theory by defining and calculating the Voro...

Thermodynamic anomalies of near-critical fluid are deeply related to its inhomogeneous structure. The inhomogeneous structure of monatomic fluid can be analyzed based on the simple Voronoi tessellation methods. Here we provide a classification algorithm based on the radical Voronoi tessellation to define the Widom delta, supercritical gas-liquid co...

A fluid particle changes its dynamics from diffusive to oscillatory as the system density increases up to the melting density. Hence, the notion of the Frenkel line was introduced to demarcate the fluid region into rigid and nonrigid liquid subregions based on the collective particle dynamics. In this work, we apply a topological framework to locat...

The dynamics of supercritical fluids, a state of matter beyond the gas-liquid critical point, changes from diffusive to oscillatory motions at high pressure. This transition is believed to occur across a locus of thermodynamic states called the Frenkel line. The Frenkel line has been extensively investigated from the viewpoint of the dynamics, but...

We report the synthesis of water-soluble and environmentally friendly fluorescent carbon dots (CDs) using the renewable resource lignin as a precursor, which is a waste emitted from pulp and paper industries and lignocellulosic biofuel production, using a compressed liquid CO 2 antisolvent method followed by carbonization and chemical oxidation wit...

The thermodynamic properties of interests for many physical or chemical processes are closely related to the relative stabilities and distributions of the different metastable states. These statistical data are described by the underlying free energy surfaces, which are typically embedded in a high-dimensional space that often appears incomprehensi...

Fatty-acid-adsorbed γ-alumina was regenerated via transesterification using methanol with sulfuric acid as a catalyst. The fatty acids adsorbed on γ-alumina were converted to fatty acid methyl esters (FAME) and desorbed from the γ-alumina during the acid-catalyzed methanol regeneration process. A series of experiments studied the effect of the oper...

Multiscale structured polymers have been considered as a promising category of functional materials with unique properties. We combined rapid prototyping and gas foaming technologies to fabricate multiscale functional materials of superior mechanical and thermal insulation properties. Through scanning electron microscope based morphological charact...

The Frenkel line, a crossover line between rigid and nonrigid dynamics of fluid particles, has recently been undergoing intense debate on its relevance as a partitioning line of supercritical phase, where the main criticism comes from the theoretical treatment of collective particle dynamics. From an independent point of view, this letter suggests...

The dynamics of supercritical fluids, a state of matter beyond the gas-liquid critical point, changes from diffusive to oscillatory motions at high pressure. This transition is believed to occur across a locus of thermodynamic states called the Frenkel line. The Frenkel line has been extensively investigated from the viewpoint of the dynamics, but...

We present a probabilistic classification algorithm to understand the structural transition of supercritical Lennard-Jones (LJ) fluid. The classification algorithm is designed based on the exploratory data analysis on the nearest Voronoi neighbors of subcritical vapor and liquid. The algorithm is tested and applied to LJ type fluids modeled with th...

The Frenkel line, a crossover line between rigid and nonrigid dynamics of fluid particles, has recently been undergoing intense debate on its relevance as a partitioning line of supercritical phase, where the main criticism comes from the theoretical treatment of collective particle dynamics. From an independent point of view, this letter suggests...

In this study, the rate of xylan hydrolysis was investigated. The hydrolysis of tulip poplar was conducted in subcritical water from 180 to 220 °C for 1–240 min. An equation for estimating the hydrolysis of ether bonds in both xylan and xylooligosaccharide from the yield of xylan and xylooligosaccharide was derived, and the rate constant of ether b...

At sufficiently low supersaturations such that the spiral growth mechanism dominates, β-cyclotetramethylenetetranitramine (HMX) grows from acetone into a polyhedron surrounded mainly by the (020) and (011) faces. In order to elucidate the morphology, a generalized form of the interfacial structure analysis model is suggested. In this method, the mo...

We briefly overview the theoretical advances for the fundamental description on the supercritical fluids since the late 1980s. The concept of supercritical gas-liquid boundary and its importance are introduced. The current state of the state-of-art theories about supercritical gas-liquid boundary (Integral Equation Approximation, Fluctuation Theory...

Biomass forms a complex interwoven structure containing cellulose, hemicellulose and lignin that hinders enzymatic hydrolysis of cellulose. Enzymatic hydrolysis of the cellulose within yellow poplar (tulip tree) particles released only 9% of the total glucose in this study. To increase the accessibility of the cellulose component, wood particles we...

The crude oil upgrading was conducted in supercritical methanol (scMeOH) using batch reactors. The influence of temperature (653–693 K), reaction time (0–120 min) on product distribution was investigated. The crude oil was upgraded into the light oil with more saturate and less aromatic, resin in scMeOH. The higher the temperature, the faster the a...

Molecular Dynamics (MD) simulations were performed to understand the solvation structure and the mechanistic nature of the divergence of partial molar volume ( ) near the critical point. Isothermal-isobaric (NpT) simulations were carried out at Tr = 1.03 from pr = 0.87 to pr = 3.72 with the truncated and shifted Lennard-Jones and the Weeks-Chandler...

Hydrochlorothiazide (HCT) and HCT/polyvinylpyrrolidone (PVP) mixtures were processed using precipitation with compressed fluid antisolvent process under sub- and supercritical conditions. When HCT was precipitated alone, severely agglomerated and irregular microparticles were obtained. On the other hand, coprecipitates were produced as spherical na...

Monte Carlo (MC) simulations were performed to understand the statistical aspects of the local density distributions of sub- and supercritical CO2 along the VLE line and at Tr = 1.02 which were obtained from the Voronoi tessellation. From the statistical analysis, the local density distribution of CO2 (v) and CO2 (l) along the VLE line was assumed...

In this work, micro- and nanocellular acrylonitrile-butadiene-styrene (ABS) foams were prepared by using sub- and supercritical CO2 as blowing agents. The sorption kinetics at 10 MPa was first measured. The sorption amount depended on the saturation temperature Arrheniusly. The diffusivities did not follow the Arrhenius relation. This relation was...

Adipic acid crystals grown from aqueous solutions have a hexagonal plate morphology with a dominant (100) face, where the hydrogen-bonding carboxylic acid groups are exposed. In the present work, the crystal morphology was investigated by interfacial structure analysis to obtain the relative growth rates for the spiral growth model. The concentrati...

Background Panax ginseng Meyer is cultivated because of its medicinal effects on the immune system, blood pressure, and cancer. Major ginsenosides in fresh ginseng are converted to minor ginsenosides by structural changes such as hydrolysis and dehydration. The transformed ginsenosides are generally more bioavailable and bioactive than the primary...

Carbon nanoparticles with hierarchical micro/mesoporous structure were developed from a commercial kraft lignin using a facile, one-pot green technology of a compressed liquid CO2 antisolvent treatment, followed by thermostablization and carbonization processes. The as-synthesized carbon nanoparticles were systematically characterized by investigat...

A novel method for regeneration of fatty acid-adsorbed γ-alumina using supercritical methanol was developed. This method is based on a difference in the affinity of a fatty acid and the corresponding fatty acid methyl ester (FAME) for γ-alumina. Palmitic acid was selected as a model fatty acid. Batch-type reactors were used to investigate the effec...

Indium oxide (In2O3) and indium tin oxide (ITO; Sn-doped In2O3) nanoparticles are synthesized via a solvothermal method using surfactant-free supercritical methanol. X-ray diffraction analysis of the products indicates that crystalline indium oxide is formed within 2 minutes at temperatures as low as 250 °C. Transmission electron microscopy shows t...

Lignocellulosic biomass, a promising renewable resource, can be converted into numerous valuable chemicals post enzymatic saccharification. However, the efficacy of enzymatic saccharification of lignocellulosic biomass is low; therefore, pretreatment is necessary to improve the efficiency. Here, a kinetic analysis was carried out on xylan hydrolysi...

For the first time, a kinetic study on the supercritical decrosslinking reaction of silane-crosslinked polyethylene (S-XLPE) in a continuous process was conducted. The decrosslinking reaction in a continuous process was corresponding to the first-order reaction model in which the reaction rate was linearly proportional to the gel content. The resid...

To evaluate the optimum operating conditions for the micronization of cyclotrimethylenetrinitramine (RDX) crystals using the Supercritical Anti-Solvent (SAS) process, a predictive approach incorporating the Hansen solubility parameters and jet behavior analysis has been suggested. The crystals were characterized by field emission scanning electron...

Nanoparticles from commercial kraft lignin were developed using a facile, one pot green technology of a compressed CO2 antisolvent. N,N-Dimethylformamide (DMF) was employed as an organic solvent to prepare the lignin solution. The effects of various process parameters: temperature, pressure, solution flow rate and initial solution concentration, on...

Novel crystallization processes that use supercritical fluids have recently attracted considerable attention because they can overcome the problems associated with conventional crystallization processes. The gas antisolvent (GAS) process is one of the promising techniques and has been applied to many applications. However, control of the GAS proces...

Physical properties and characteristics of a solid particle highly depend on the particle shape and size. The Gas AntiSolvent (GAS) process is a recently developed process that can control the size and morphology of solid particles using supercritical fluids as an antisolvent to resrystallize desired products in solution. Though many lab-scale expe...

De-crosslinking of silane-cross-linked polyethylene (S-XLPE) in supercritical methanol was investigated. Changes in gel content and molecular weight with reaction temperature and reaction time were analyzed in a batch reactor, and kinetic parameters were calculated from the experimental data. The reaction time for de-crosslinking shortened as the r...

Tetracycline has been obtained as amorphous agglomerates in the supercritical antisolvent process. This phenomenon has been postulated to occur due to weak solvent/antisolvent interaction. In order to verify the hypothesis and prevent the coalescence of nanoparticles, we micronized tetracycline hydrochloride using supercritical and liquid CO2 in th...

The hydrolysis of defatted rice bran using near-critical water was performed, and the feasibility of consequent hydrolyzate as a growth medium was investigated by the cultivation of Saccharomyces cerevisiae. The near-critical water hydrolysis was carried out through a series of batch experiments, and the contents of total carbohydrates, disaccharid...

Supercritical (sc) fluids are considered to be a promising alternative to toxic organic solvents in a variety of processes. In this work, a study of the synthesis of terephthalic acid (TPA) from p-xylene (PX) using supercritical carbon dioxide (scCO2) as a reaction medium was performed. The effects of various process parameters were investigated, i...

Continuous supercritical water gasification (SCWG) of various feedstocks of C1-C16 was conducted to produce hydrogen-rich gas. These feedstocks represent model compounds of biomass such as methanol/ethanol (alcohol-type), glucose and glycerol (byproducts of biodiesel synthesis), and model compounds of petroleum fuels such as iso-octane/n-octane (ga...

The present invention is directed to a method for effectively separating HMX and RDX from HMX/RDX-included explosives, respectively, without using a harmful organic solvent, the method capable of respectively separating HMX and RDX from HMX/RDX-included explosives by selectively dissolving RDX included in explosives by using a difference between so...

Metal and metal oxide nanoparticles were synthesized using supercritical water (SCW) as a reaction medium and glycerol as a reducing agent at 400 degrees C and 300 bar. X-ray diffraction (XRD) patterns confirmed that silver, copper and nickel nitrates were reduced to zero-valent metal nanoparticles. On the other hand, cobalt, iron and manganese nit...

The present invention relates to a method for recrystallizing fine spherical cyclotrimethylenetrinitramine (Research Department Explosive, hereinafter, referred to as “RDX”) particles, and the method for recrystallizing fine spherical RDX particles according to the present invention may include (a) introducing a powder material containing RDX into...

With a view to promoting dispersion of lycopene in water, the precipitation of an inclusion complex of lycopene and β-cyclodextrin was investigated using the solution-enhanced dispersion by supercritical fluids (SEDS) process. The inclusion complex, which was prepared in N,N-dimethylformamide (DMF), was dissolved in the same solvent and then micron...

We have attempted to study the formation of BaTiO3 by hydrothermal synthesis and our experiments reveal the reaction by dissolution–precipitation as the dominant operating mechanism. Two major formation mechanisms of BaTiO3 by hydrothermal synthesis involving either in situ transformation or dissolution–precipitation have been previously proposed....

Waste cooking oil (WCO) was purified by supercritical carbon dioxide (scCO2) extraction and catalytic hydrodeoxygenation of fresh soybean oil, WCO and scCO2-purified oil were studied for the synthesis of diesel-like hydrocarbons. The chemical compositions of the scCO2-purified oils were very similar to those of fresh oil. Hydrotreating of WCO over...

The co-precipitation of loperamide hydrochloride (LPM) and polyethylene glycol (PEG) using aerosol solvent extraction system (ASES) was examined. Scanning electron microscopy — energy dispersive X-ray spectroscopy (SEM-EDS) analysis showed that the co-precipitation was achieved in various LPM-PEG mass ratios with changes in its morphology. In 10–50...

This study investigates the effect of various process parameters during continuous synthesis in supercritical water on the physicochemical and electrochemical properties of lithium iron phosphate (LiFePO4) for use in large-scale lithium 2nd battery applications. The process parameters include reaction temperature (300-400 °C), precursor solution co...

The aim of this work was to understand the agglomeration phenomenon and to predict the agglomeration behavior of materials in the supercritical antisolvent (SAS) process. Carbon dioxide-induced melting point depression is believed to be one of the major causes of the formation of agglomerates during the SAS process. Here, we attempted to observe th...

Biodiesel and zinc oxide nanoparticles were synthesized simultaneously using supercritical methanol. Zinc nitrate was used as the source of zinc for the formation of the zinc oxide nanoparticles, which acted as a catalyst during the transesterification of rapeseed oil. In addition, the in situ formed zinc oxide nanoparticles led to a reduction in t...

The effect of various solvents on the de-cross-linking reaction of cross-linked polyethylene under subcritical and supercritical conditions was studied. The gel content of the de-cross-linked polyethylene decreased from 60 to 0.8–2.5% at 380 °C within 5 min in all of the solvents tested in this study. When water, ethanol, and 2-propanol were used,...

A novel method was developed for fractionating cellulose microfibrils from forest residue (tulip tree sawdust) to enhance cellulose digestibility, particularly at minimum enzyme loadings. This method involved three main stages: selective hemicellulose solubilization by subcritical water (SCW) pretreatment, delignification of the SCW-pretreated soli...

This work studies optimization of a Cyclotetramethylenetetranitramine (HMX) recrystallization process by precipitation. HMX is a powerful and relatively insensitive explosive. Since the shape and particle size are important properties for explosive materials, there have been many efforts to control those properties. Due to their vulnerability to he...

Carbon dioxide emission and nitrogen pollution caused by nitrogen-containing wastes have become global environmental issues in recent years. To simultaneously reduce the discharge of carbon dioxide and reactive nitrogen during the conventional supercritical water oxidation (SCWO), we have developed an advanced SCWO process involving the treatment o...

Hydrothermal synthesis of cerium oxide nanocrystals was performed with in-situ surface modification using soybean oil and palm oil as capping agents. The synthesized nanocrystals were examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analysis (TGA). TEM...

Carbon coating on lithium iron phosphate (LiFePO4) plays a crucial role in determining its electrochemical performance. This study investigates the effect of carbon coating on lithium iron phosphate particles synthesized using a continuous supercritical hydrothermal synthesis (SHS) method and a conventional solid-state (SS) method, with sucrose as...

Ceria is one of the most important catalytic materials which can be used in three-way catalysts, waste water treatment, petroleum refining, etc. So far, many methods have been studied to produce ceria nanoparticles. In this study, ceria nanoparticles were prepared via solvothermal synthesis using supercritical methanol in short reaction time using...

Physical cleaning and/or chemical cleaning have been generally used to control biofouling in the reverse osmosis (RO) process. However, conventional membrane cleaning methods to control biofouling are limited due to the generation of by-products and the potential for damage to the RO membranes. In this study, supercritical carbon dioxide (SC CO(2))...

Industrial wastes of crosslinked polymers have been burned or disposed of in landfills because there is no recycling technology due to their insoluble and infusible network chain structure. However, recycling of cross-linked polymers has been taken a growing attention because of issues of environmental pollution and of resources conservation. In th...

Surface-modified cerium oxide (CeO2) nanoparticles, dispersible in either a hydrophilic or a hydrophobic medium, are synthesized continuously in supercritical methanol using methoxy polyethylene glycol (PEG350, H(OCH2CH2)nOCH3, MW = 350 g/mol) or α,ω-Bis(2-carboxymethyl)polyethylene glycol (PEG600, HOOCCH2(OCH2CH2)nOCH2COOH, MW = 600 g/mol) as a su...

Decrosslinking of crosslinked polypropylene(XLPP) in supercritical methanol was investigated compared with that of crosslinked polyethylene(XLPE). Effect of reaction temperature and initial gel contents was studied using a batch reactor. Gel contents of samples before and after reaction were measured for quantitative analysis. As reaction temperatu...

This study examined whether supercritical CO2 and N2O fluids are effective in inactivating Ascaris suum eggs, which were chosen as a model for parasite eggs. The treatments were carried out in a multibatch apparatus, in which, the eggs could be placed atop a solid surface (non-immersed condition) or in aqueous solution (immersed condition). Various...

Crystallization processes are widely used in various applications such as polymers, dyes, pharmaceuticals, and explosives. Novel crystallization processes using supercritical fluids have recently attracted much attention due to the environmental advantage of using environmentally benign carbon dioxide as a solvent. Gas anti-solvent (GAS) process is...

A gas anti-solvent process (GAS) was used to recrystallize cyclotetramethylenetetranitramine (HMX). A series of experiments were carried out, changing key operating parameters such as the solvent type, temperature, CO2 addition rate, initial solute concentration, and agitation rate. It was observed that the crystal structure and the crystal phase o...

In this study, the recrystallization of valsartan by ASES (Aerosol Solvent Extraction System), a supercritical micronization process, using compressed CO2 was carried out to improve the bioavailability of valsartan through preparation of micro sized particles without excessive agglomeration. Fine valsartan particles from an ethyl acetate (EA) solut...

The aim of this study is to investigate the bactericidal effect of supercritical nitrous oxide (SC N(2)O) on both typical Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli while varying the operating conditions including the suspending medium (nutrient broth, phosphate buffered saline, phosphate buffer, phosphate buffer contain...

This study investigated the micronization of HMX (cyclotetramethylenetetranitramine) using two types of recrystallization methods with supercritical carbon dioxide as an antisolvent, namely, the aerosol solvent extraction system (ASES) and gas antisolvent (GAS) processes. The effects of experimental variables on the recrystallization of β-HMX parti...