Sharif Digital Repository

Ultrafine particles of paracetamol were produced by Rapid Expansion of Supercritical Solution (RESS). The experiments were conducted to investigate the effects of extraction temperature (313353K), extraction pressure (1018MPa), preexpansion temperature (363403K), and postexpansion temperature (273323 K) on particles size and morphology of paracetamol particles. The characterization of the particles was determined by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Liquid Chromatography/Mass Spectrometry (LC-MS) analysis. The average particle size of the original paracetamol was 20.8m, while the average particle size of paracetamol after nanonization via the... 

In this research, organic solvent composed of hexane and methanol was used for lipid extraction from dry and wet biomass of Chlorella vulgaris. The results indicated that lipid and fatty acid extraction yield was decreased by increasing the moisture content of biomass. However, the maximum extraction efficiency was attained by applying equivolume mixture of hexane and methanol for both dry and wet biomass. Thermodynamic modeling was employed to estimate the effect of hexane/methanol ratio and moisture content on fatty acid extraction yield. Hansen solubility parameter was used in adjusting the interaction parameters of the model, which led to decrease the number of tuning parameters from 6... 

In the present study, the solubility of paracetamol in supercritical CO2 is measured at temperatures between 311 and 358 K and pressures between 95 and 265 bar. It was shown that the solubility of paracetamol through a static solubility measurement method was between 0.3055 × 10−6 to 16.3582 × 10−6 based on mole fraction. The obtained experimental solubility data revealed the direct effect of pressure on the paracetamol experimental data, while the temperature has a dual effect of both increasing and decreasing effect considering the shifting point known as crossover pressure which was measured to be around 110 bar for paracetamol. Besides, two theoretical approaches were applied to predict... 

In the present work, a new micro-solid phase extraction (μ-SPE) sorbent as an extracting medium based on core-shell nanofibers was synthesized by electrospinning. The core-shell nanofibers of polyvinylpyrrolidone-Polybutylene terephthalate/polypyrrole (PVP-PBT/PPy) were electrospun and subsequently, modified hollow nanofibers were prepared by removing the central PVP moiety. Moreover, conventional PBT/PPy was also prepared for the comparison purposes. The homogeneity and the porous surface structure of the core-shell nanofibers were confirmed by scanning electron microscopy (SEM). The applicability of the fabricated nanofibers-coating was examined by immersed μ-SPE of some selected triazine... 

A solution of polyamide (PA) containing polyethylene glycol (PEG) as a side low-molecular-weight polymer was electrospun. After synthesizing the PA-PEG nanofibers, the constituent was subsequently removed (modified PA) and confirmed by Fourier transform infrared spectroscopy. The scanning electron microscopy images showed an average diameter of 640 and 148 nm for PA and PA-PEG coatings, respectively, while the latter coating structure was more homogeneous and porous. The extraction efficiencies of PA, PA-PEG, and the modified PA fiber coatings were assayed by headspace solid-phase microextraction of a number of chlorophenols from real water samples followed by their determination by gas... 

Novel unbreakable solid phase microextraction (SPME) fiber coatings were fabricated by electrospinning method in which the polymeric solution was converted to nanofibers using high voltages. Four different polymers, polyurethane (PU), polycarbonate (PC), polyamide (PA) and polyvinyl chloride (PVC) were prepared as the fiber coatings on thin stainless steel wires. The extraction efficiencies of new coatings were investigated by headspace solid-phase microextraction (HS-SPME) of some environmentally important chlorobenzenes from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Among them, PU showed a prominent efficiency. Effects of coating time and polymer... 

Extraction of the essential oil from a medicinal plant called Dracocephalum kotschyi Boiss was performed by green technology of supercritical carbon dioxide (SC-CO2) extraction. A Taguchi orthogonal array design with an OA16 (45) matrix was used to evaluate the effects of five extraction variables: pressure of 150-310bar, temperature of 40-60°C, average particle size of 250-1000μm, CO2 flow rate of 2-10ml/s and dynamic extraction time of 30-100min. The optimal conditions to obtain the maximum extraction yield were at 240bar, 60°C, 500μm, 10ml/s and 100min. The extraction yield under the above conditions was 2.72% (w/w) which is more than two times the maximum extraction yield that has been... 

A novel solid phase microextraction (SPME) fiber was fabricated by electrospinning method in which a polymeric solution was converted to nanofibers using high voltages. A thin stainless steel wire was coated by the network of polymeric nanofibers. The polymeric nanofiber coating on the wire was mechanically stable due to the fine and continuous nanofibers formation around the wire with a three dimensional structure. Polyamide (nylon 6), due to its suitable characteristics was used to prepare the unbreakable SPME nanofiber. The scanning electron microscopy (SEM) images of this new coating showed a diameter range of 100-200nm for polyamide nanofibers with a homogeneous and porous surface... 

A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the... 

Here, a three dimensional nickel–based metal organic framework (MOF) was synthesized via solvothermal and room temperature protocols. In order to study the effects of the synthesis conditions on the physical properties such as pore sizes and shapes of the prepared MOFs, their extraction capabilities were examined. Both MOFs were characterized by Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller and thermogravimetric analyses. Brilliant properties such as porous structure, high surface area and considerable thermal stability make them reasonable candidates to be employed as efficient extractive phases. The efficiency of the... 

Herbal medicine wastes (HMWs) are byproducts of medicine factories, which are mainly landfilled for their environmental problems. Only bearing in mind the contamination and concerns caused by the COVID-19 pandemic and environmental emissions, the worth of herbal medicine wastes management and conversion to green products can be understood. In this work, subcritical water treatment was carried out batch-wise in a stainless tube reactor in the pressure range of 0.792–30.0 MPa, varying the temperature (127–327 °C) and time (1–60 min) of extraction. This resulted in new and green material sources, including organic acids, amino acids, and sugars. Amazingly, at very low extraction times (below 5...