Aydin Akgerman

Active growth factor delivery from poly(d,l-lactide-co-glycolide) foams prepared in supercritical CO2

A method for the production of microporous poly(D, L-lactide-co-glycolide) foams containing encapsulated proteins using supercritical carbon dioxide is described. Foams generated as aqueous protein emulsions in a polymer-solvent solution were saturated with carbon dioxide at supercritical conditions, and then suddenly supersaturated at ambient conditions causing bubble nucleation and precipitation of the polymer. Proteins contained in the water phase of the emulsion were encapsulated within the foams, including basic fibroblast growth factor (bFGF), an angiogenic factor of interest in tissue engineering applications. The release and activity of bFGF from these foams was determined in vitro and compared with similar porous scaffolds prepared by traditional solvent casting-salt leaching techniques. Total protein release rate was greater from structures made in CO(2) than those made by the salt leaching technique, however a large initial burst of bFGF was released from the salt leached structures. This initial burst was not observed from the polymer foams processed in CO(2) and active bFGF was released at a relatively constant rate. Residual methylene chloride levels were measured in the foams made with CO(2) and were found to be above the limits imposed by the US Pharmacopoeia implying that further solvent removal would be required prior to in vivo use.

Biodegradation of phenolic wastes

Phenolic biodegradation kinetics were determined in bioreactors with large solids retention times (SRT). Long term kinetic experiments were conducted in pulse-fed batch reactors for single substrate (phenol) and multiple substrates (combinations of glucose, phenol and pentachlorophenol). Short term initial rate experiments were also conducted on the single and multiple substrate reactors. Results indicate that phenol is metabolized at a maximum rate of 0.55 h−1 with a half saturation coefficient of 10 mg/1. Phenol concentrations in excess of 50 mg/1 inhibit the biodegradation rate. Our results also indicate that pentachlorophenol is cometabolized in the presence of phenol. It can be concluded that biodegradation of phenolic waste is a viable treatment option because the organisms, through their metabolic processes, reduced the waste concentrations below our detection limits.

Catalytic wet oxidation of phenol over a Pt/TiO catalyst

Wet oxidation of phenol by air or oxygen over a Pt/TiO2 catalyst is studied in a batch reactor in the temperature range 150–200°C, pressure range 34–82 atm, and a catalyst loading range of 0–4 g catalyst L−1. The catalyst was powdered 4.45% Pt/TiO2 with a maximum particle size of 105 μm. Results show complete oxidation of phenol and almost complete total organic carbon (TOC) removal. Small amounts of stable organic acids are formed in side reactions of the phenol degradation pathway and are not readily degraded. Experimental results show that the reaction rate decreases by increased oxygen concentration. Theoretical rate expressions are derived, based on postulated oxidation and TOC reduction mechanisms.

Mordant dyeing of wool by supercritical processing

Abstract Few studies have reported the use of supercritical fluids as solvents in dyeing of textile fibers. Studies on synthesis of new dyestuff that can be used in this technique and their solubility in the supercritical fluid are attracting increasing attention. In this study, wool fibers were dyed with mordant dyes dissolved in supercritical carbon dioxide. We used three mordant dyes that have chelating ligand properties, 2-nitroso-1-naphthol (C.I. Mordant Brown), 5-(4-aminophenylazo) salicylic acid (C.I. Mordant Yellow 12) and 1,2-dihydroxyanthraquinone (C.I. Mordant Red 11 also called Alizarin) which were dissolved in supercritical carbon dioxide, and five different mordanting metal ions, Cr(III), Al(III), Fe(II), Cu(II) and Sn(II). Wool fibers were mordanted by the metal using conventional techniques and dyed at 333-353 K temperature and at 150–230 atm pressure. Dyed materials had excellent wash fastness properties.

Hot water extraction with in situ wet oxidation: PAHs removal from soil

We are reporting the results of a small-scale batch extraction with and without in situ wet oxidation of soils polluted with polycyclic aromatic hydrocarbons (PAHs) using subcritical water (liquid water at high temperatures and pressures but below the critical point as the removal agent). Two types of soil; one spiked with four PAHs, and an aged sample were used. Experiments were carried out in a 300 ml volume reactor in the batch mode. In each experiment, the reactor was filled with 45-50 g of soil and 200-220 ml of double distilled water. For extraction without oxidation, the reactor was pressurized with nitrogen, while for those with the oxidation, an oxidizing agent (air, oxygen or hydrogen peroxide) was used. The extraction only experiments were carried out at 230, 250 and 270 degrees C for spiked soil samples, and at 250 degrees C for aged soil samples, while all of the combined extraction and oxidation experiments were carried out at 250 degrees C. Removal of PAHs from spiked soil in extraction-only experiments was from 79 to 99+% depending on the molecular weight of the PAH. This was in the range of 99.1% to excess of 99.99% for the combined extraction and oxidation. While 28-100% of extracted PAHs can be found in water phase in case of extraction alone, this reduces to a maximum of 10% if the extraction is combined with oxidation. With aged soil similar or comparable results were obtained. Based on these results, extraction with hot water, if combined with oxidation, would probably reduce the cost of post treatment for the water and can be used as a feasible alternative technique for remediation of contaminated soils and sediments.

Catalytic wet oxidation of phenol in a trickle bed reactor over a Pt/TiO2 catalyst.

Catalytic wet oxidation of phenol was studied in a batch and a trickle bed reactor using 4.45% Pt/TiO2 catalyst in the temperature range 150-205 degrees C. Kinetic data were obtained from batch reactor studies and used to model the reaction kinetics for phenol disappearance and for total organic carbon disappearance. Trickle bed experiments were then performed to generate data from a heterogeneous flow reactor. Catalyst deactivation was observed in the trickle bed reactor, although the exact cause was not determined. Deactivation was observed to linearly increase with the cumulative amount of phenol that had passed over the catalyst bed. Trickle bed reactor modeling was performed using a three-phase heterogeneous model. Model parameters were determined from literature correlations, batch derived kinetic data, and trickle bed derived catalyst deactivation data. The model equations were solved using orthogonal collocations on finite elements. Trickle bed performance was successfully predicted using the batch derived kinetic model and the three-phase reactor model. Thus, using the kinetics determined from limited data in the batch mode, it is possible to predict continuous flow multiphase reactor performance.

Extraction of phenol from water with supercritical carbon dioxide

Abstract Recent attention has been directed to supercritical extraction as a viable method for removing organic contaminants from water. The fundamental thermodynamic parameter of interest for the extraction of contaminants form water is the distribution coefficient, defined as the ratio of the mole fraction of con taminant in the supercritical phase to the mole fraction of contaminant in the water phase. We have conducted static equilibrium supercritical extractions of phenol (a common waste water pollutant from coal-coking processes used by the steel industry and those used by coal gasification plants) as a function of pressure and temperature using carbon dioxide as the solvent. Samples of the water phase were analyzed before and after extraction to determine the distribution coefficient. Values of the distribution coefficient ranged from 0.4 to 1.4. Vapor-liquid equilibrium calculations were performed using three cubic equations-of-state (with quadratic mixing rules) to correlate the data at each experimental condition studied. Due to variations in the binary interaction parameters as a function of pressure, further prediction of the distribution coefficient for conditions where experimental data does not exist does not seem feasible with these models. In addition, to develop a methodology to relate the extraction parameters to a viable parameter of interest we have monitored toxic activity via a short term bioassay to validate the extraction process and (through calibration of the test) provide an alternative method of determining the distribution coefficient. Specifically, the cytotoxic effects of phenol has been targeted.

Synthesis and characterization of {((COD)Rh(bis-(2R,3R)-2,5-diethylphospholanobenzene)) + BARF − } for use in homogeneous catalysis in supercritical carbon dioxide

Reaction of [(COD)2Cl2Rh] (COD: cyclo-octadiene) with sodium tetrakis((3,5-trifluoromethyl)phenyl)borate (NaBARF) in the presence of an excess of COD yields [(COD)2Rh] + BARF − . The COD ligands are readily displaced by the bidentate ligand 1,2-bis((2R,5R)-2,5-diethylphosphalono)benzene (Et-DuPHOS) to form [(COD)Rh(Et-DuPHOS)]BARF, the structure of which has been determined by X-ray crystallography. BARF was selected as the counterion in order to achieve solubility in supercritical carbon dioxide for use in asymmetric hydrogenation and hydroformylation reactions. Density-functional theory calculations were used to study the intermediates in asymmetric hydroformylation of styrene. The energies of the two-enantiomer models differ by 11.3 kcal mol −1 .

Fundamentals of Solids Extraction by Supercritical Fluids

The theory and advantages of supercritical extraction are discussed and the applications of supercritical extraction from solid matrices are reviewed in detail. The thermodynamic equilibrium of supercritical extraction is examined and the adsorption/desorption phenomena in presence of supercritical fluids are explained. Various models, proposed in the literature, to interpret the extraction phenomena from solid matrices are reviewed. The importance of the fundamental parameters like adsorption equilibrium constants, mass transfer coefficients, axial dispersion coefficients and effective diffusivities of the solutes in the solid pore space are emphasised. The last section reviews the novel extraction processes proposed for the remediation of environmental matrices.

Supercritical extraction of phenol from soil

Abstract The distribution coefficients for phenol between soil and both sub- and supercritical carbon dioxide were measured by static experiments in the temperature range 297–349 K and the pressure range 9–30 MPa. The effects of soil organic content, soil moisture, temperature, and pressure on the distribution co efficients were investigated. Simple thermodynamic models were developed for temperature and pressure dependency of the distribution coefficients which successfully represent the data. In addition, methanol was tested as an entrainer and experiments were conducted with benzene to investigate the effects of co-pollutants. The results show that the presence of chemicals in the system other than phenol affect the distribution coefficients.