Supercritical extraction of polychlorinated biphenyls from a solid matrix

Typescript (photocopy).The contaminated soil around the uncontrolled waste sites in the United States is considered to be a potentially hazardous environmental pollution. At present, over 1,000 waste sites are on the National Priorities List (NPL) which are eligible for research funds from the Superfund. The major environmental problem of the NPL sites is that the site ground water is contaminated by the leaching of hazardous pollutants from contaminated soil. Currently, burial and incineration are used to decontaminate soil both of which will not be a viable solution in the future. Burial is banned in 1990 and incineration, on the other hand, is expensive and in many cases it poses an immediate environmental risk because of the highly toxic gaseous products of incomplete combustion of toxic contaminants. The objective of this study was to investigate the feasibility of supercritical fluid extraction as an alternative technology for soil decontamination and to determine the relevant extraction parameters. This project used supercritical carbon dioxide to extract an organic pollutant (hexachlorobenzene) from soil using a dynamic extractor equipment. Three parameters (partition coefficient, mass transfer coefficient, axial dispersion coefficient) were investigated as a function of the temperature, pressure, and flow rate of carbon dioxide. The partition coefficient behavior depended on the temperature and pressure, while it was independent of the flow rate. This result indicated that the carbon dioxide solvent power is directly related to its density. The axial dispersion coefficient, on the other hand, was not only dependent on pressure and temperature, but also on the flow rate. These results suggest that the contribution by convection is more important than molecular diffusion under supercritical conditions. The overall mass transfer coefficient was independent of the pressure and temperature, but it changed with flow rate. Methanol when used as an entrainer, did not offer any significant advantages over that of pure carbon dioxide. This result confirms the fact that polar entrainers do not increase the solubilities of non-polar contaminants in carbon dioxide..

Supercritical extraction of polychlorinated biphenyls from a solid matrix

Typescript (photocopy).The contaminated soil around the uncontrolled waste sites in the United States is considered to be a potentially hazardous environmental pollution. At present, over 1,000 waste sites are on the National Priorities List (NPL) which are eligible for research funds from the Superfund. The major environmental problem of the NPL sites is that the site ground water is contaminated by the leaching of hazardous pollutants from contaminated soil. Currently, burial and incineration are used to decontaminate soil both of which will not be a viable solution in the future. Burial is banned in 1990 and incineration, on the other hand, is expensive and in many cases it poses an immediate environmental risk because of the highly toxic gaseous products of incomplete combustion of toxic contaminants. The objective of this study was to investigate the feasibility of supercritical fluid extraction as an alternative technology for soil decontamination and to determine the relevant extraction parameters. This project used supercritical carbon dioxide to extract an organic pollutant (hexachlorobenzene) from soil using a dynamic extractor equipment. Three parameters (partition coefficient, mass transfer coefficient, axial dispersion coefficient) were investigated as a function of the temperature, pressure, and flow rate of carbon dioxide. The partition coefficient behavior depended on the temperature and pressure, while it was independent of the flow rate. This result indicated that the carbon dioxide solvent power is directly related to its density. The axial dispersion coefficient, on the other hand, was not only dependent on pressure and temperature, but also on the flow rate. These results suggest that the contribution by convection is more important than molecular diffusion under supercritical conditions. The overall mass transfer coefficient was independent of the pressure and temperature, but it changed with flow rate. Methanol when used as an entrainer, did not offer any significant advantages over that of pure carbon dioxide. This result confirms the fact that polar entrainers do not increase the solubilities of non-polar contaminants in carbon dioxide..

Application of response surface methodology for optimization of lead removal from an aqueous solution by a novel superparamagnetic nanocomposite

The present study focuses on the response surface methodology (RSM) for the optimization of lead removal from an aqueous solution by a novel superparamagnetic nanocomposite. A rotatable central composite design and the response surface methodology were used to conduct and to analyze the experiments, respectively. The adsorption process was investigated as a function of the four factors consisting of pH (4.0–6.0), temperature (20℃–60℃), initial lead concentration (10–90 mg/L) and adsorbent dosage (0.2–1.0 g/L). The maximum lead adsorption capacity was obtained to be 124.955 mg/g under the optimal conditions of 5.49, 60℃, 89.08 mg/L, and 0.48 g/L for the solution pH, temperature, initial lead ion concentration, and the adsorbent dosage, respectively. The desirability function was used to find an optimum point where the desired conditions could be obtained. The superparamagnetic nanocomposite could be used as an adsorbent for the removal of toxic heavy metals from water and wastewater

Optimization of supercritical extraction of galegine from Galega officinalis L.: Neural network modeling and experimental optimization via response surface methodology

Supercritical CO2 extraction of galegine from Galega officinalis L. was carried out under different operating conditions of temperature (35-55 °C), pressure (10-30MPa), dynamic extraction time (30-150min), CO2 flow rate (0.5-2.5 mL/min) and constant static extraction time of 20 min. Design of experiment was by response surface methodology (RSM) using Minitab software 17. The response surface analysis accuracy was verified by the coefficient of determination (R2=93.4%) along with modified coefficient of determination (mod-R2=87.7%). The optimum operating conditions were found by using RSM modeling to be 42.8 °C, 22.7MPa, 141.5min and 2.15 mL/min, in which the maximum galegine extraction yield of 3.3932mg/g was obtained. Artificial neural network (ANN) using Levenberg-Marquardt backpropagation training function with six neurons in the hidden layer was implemented for the modeling of galegine extraction such that the coefficient of determination (R2) was 96.6%

Pressure drop behavior and mass transfer properties of a high specific area random type packing in a narrow packed column

In this paper, the comprehensive experimental examinations are conducted to investigate the mass transfer properties of Dixon ring packing. The main aspect of this study is to investigate the characteristics of Dixon ring packing using a narrow packed column. Firstly, the mass transfer properties of the packing were investigated using distillation experiments at total reflux. Afterwards, the pervasive experiments were conducted to plot the generalized pressure drop correlation chart. Finally, the variation of height equivalent to a theoretical plate (HETP) was determined at total reflux operations for various vapour loading factors. Our findings showed that increasing the vapour loading factor up to 0.62 Pa0.5 would eventually decrease the HETP. It was also shown that the further increase in the vapour loading factor results in a sudden increase in the HETP value. According to our findings, the selection of the optimum vapor loading factor would enhance the value of HETP up to more than 57 %

Thyroglossal duct cyst coexisting with a fistulous tract: A rare case report and literature review

An 11-year-old boy was admitted to the hospital complaining of odorous discharge from an opening in the anterior region of the left side of his neck. During physical examinations, we understood that his cyst moved with deglutition and protrusion of the tongue. In order to get a correct diagnosis of the patient problem, fistulography with contrast agent meglumine was done from the patient neck in two projections, anterior-posterior and anterior-posterior-oblique. By information obtained of physical examinations and his neck radiographs, thyroglossal duct cyst coexisting with a fistulous tract was diagnosed. In adolescents and adults, thyroglossal duct cyst is one the most common causes of midline congenital cyst formation in the neck that may appear anywhere between the base of the tongue and the suprasternal region. Thyroglossal duct cyst develops from a persistence of any portion of the thyroglossal tract in the embryonic period. After birthday, infection of cyst can sometimes lead to fistula formation in the neck. Both of them, thyroglossal duct cyst and thyroglossal fistula, are usually diagnosed by imaging techniques. Keywords: Thyroglossal duct cyst, Thyroglossal fistula, Fistulograph