Siti Machmudah

Degradation of glycerol using hydrothermal process.

Sub-critical or supercritical water was utilized for the degradation of glycerol in an environmentally benign reaction. The reaction was carried out in a batch reactor in the temperature range of 473-673 K, pressure of 30 MPa, and reaction time of 20-60 min. The effects of temperature and reaction time were observed. The degradation of glycerol produced acetaldehyde, acrolein, allyl alcohol and un-identified products. The highest yield of acrolein, acetaldehyde and allyl alcohol were 0.20, 7.17, 96.69 mol%, respectively. Glycerol conversion was 99.92 mol%. While acetaldehyde was formed only in sub-critical water and allyl alcohol only in supercritical water, acrolein was formed in both. The kinetics of the global reaction displayed a pseudo-first-order. The activation energy at subcritical water was 39.6 kJ/mol. Based on the results, this method could be an efficient method for glycerol degradation because the high conversion of glycerol was obtained.

Extraction of Nigella sativa L. using Supercritical CO2: A Study of Antioxidant Activity of the Extract

Abstract Oil from Nigella sativa seed has been extracted by supercritical CO2 as a solvent at various pressures. In this study, two conditions of separation were used; they were low and high pressure separation. The antioxidant activity of the oil extracted was measured using an ultraviolet-visible spectrum (UV‐Vis) spectrophotometer. There was no effect on the change of extraction pressure in apparatus with low pressure. The essential oil content in the extract from apparatus with high pressure was approximately two times higher than it was with low pressure. The antioxidant activity of Nigella sativa oil showed positive result. The antioxidant activity was obtained by the quantity of thymoquinone and carvacrol.

Extraction of Fucoxanthin from Raw Macroalgae excluding Drying and Cell Wall Disruption by Liquefied Dimethyl Ether

Macroalgae are one of potential sources for carotenoids, such as fucoxanthin, which are consumed by humans and animals. This carotenoid has been applied in both the pharmaceutical and food industries. In this study, extraction of fucoxanthin from wet brown seaweed Undaria pinnatifida (water content was 93.2%) was carried out with a simple method using liquefied dimethyl ether (DME) as an extractant in semi-continuous flow-type system. The extraction temperature and absolute pressure were 25 °C and 0.59 MPa, respectively. The liquefied DME was passed through the extractor that filled by U. pinnatifida at different time intervals. The time of experiment was only 43 min. The amount of fucoxanthin could approach to 390 μg/g dry of wet U. pinnatifida when the amount of DME used was 286 g. Compared with ethanol Soxhlet and supercritical CO2 extraction, which includes drying and cell disruption, the result was quite high. Thus, DME extraction process appears to be a good method for fucoxanthin recovery from U. pinnatifida with improved yields.

Decomposition of methyl orange using pulsed discharge plasma at atmospheric pressure: Effect of different electrodes

One of the new technologies for water treatment is the pulsed discharge plasma method, which utilizes high voltage pulses with a fast rise time and a very short duration. In this study, under argon atmosphere at 313 K, the decoloration of methyl orange was conducted with copper (Cu) and stainless steel #304 (SUS-304) as electrodes in the batch reactor. The performance of pulse discharge plasma generation was observed using an intensified charge coupled device (ICCD) camera. The results show that the intermediate compounds from the degradation of methyl orange consist primarily of aromatic compounds containing nitrogen functional groups. At the same number of plasma discharge times, the percentage conversion of methyl orange with Cu as the electrode is higher than that with SUS as the electrode. However, the percentage degradation of methyl orange is over 90% in both cases when the number of plasma discharge times was 20000.

Generation of PVP fibers by electrospinning in one-step process under high-pressure CO2

BackgroundElectrospinning is a process of electrostatic fiber formation using electrical forces to produce polymer fibers from polymer solution in nano/micrometer scale diameters. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years, mostly in solvent solution and some in melt form. In this work, electrospinning was conducted under high-pressure carbon dioxide (CO2) to reduce the viscosity of polymer solution. The experiments were conducted at 313 K and approximately 8.0 MPa. Polyvinylpyrrolidone in dichloromethane was used as a polymer solution with 4 wt.% of concentration. The applied voltage was 17 kV, and the distance of nozzle and collector was 8 cm. The morphology and structure of the fibers produced were observed by scanning electron microscopy.ResultsWhen the CO2 pressure was 5 MPa, the resultant fibers had an average diameter of 2.28 ± 0.38 to 4.93 ± 1.02 μm. The ribbon-like morphology was formed with increasing pressure of CO2 at 8 MPa with a tip 0.75-mm inside diameter.ConclusionsThe results show that the depressurization of CO2 at the end of experiment assists the removal process of the polymer solvent and produces the porous nature of fibers without collapsing or foaming. These behaviors hold the potential to considerably improve devolatilization electrospinning processes.

Production of nanofibers by electrospinning under pressurized CO2

Electrospinning is one of the simple technical methods for the production of polymer nanoparticles and nanofibers. Various polymers have been successfully electrospun into ultrafine particles and fibers in recent years mostly in solvent solution and some in melt form. In this work, near- and supercritical CO2 were used as media for this process. At these conditions, the solubility can be tuned by controlling the temperature and pressure. Therefore, it is possible to form particles and fibers within a thermodynamic window where the biopolymer has been softened, but not dissolved. The experiments were conducted by using electrospinning under pressurized CO2 system at pressures of ∼ 8.0 MPa and temperature of 313 K to produce several polymers fibers. Polyvinylpyrrolidone was used as the starting material. During the electrospinning process, the applied voltage was 10–17 kV and the distance of nozzle and collector was 8 cm. The concentration of polymer solution was 4 wt%. The morphology- and structure-produced fibers were observed by scanning electron microscopy. The results showed that temperature and pressure affected the morphology of fibers produced by electrospinning in pressurized CO2. This suggests that the thermal behavior of the polymer can be optimized by adjusting the polymer through the adjustment of pressure and temperature by using CO2 as a solvent.

Pulsed Discharge Plasma over a Water Surface Induces Decoloration of Dyes

It was well known that plasma can be defined as a partially ionized gas composed of ions, electrons and neutral species. Recently, plasma-water interaction has attracted growing interest as it may provide experimental chemists with a quite unique reaction medium. In this work, decoloration of dyes in water as a reaction media and the effects of various parameters with pulsed high-voltage discharge plasma are studied. Such as plasma applied under hydrothermal conditions generates high-energy electrons, ions, and radicals, which in turn may generate new reaction fields, leading to effective organic compounds oxidation for both homogeneous and heterogeneous reactions. Here, we utilize pulse discharge plasma over water surface to study the decoloration of Orange G, Orange II, Congo Red, and Naphthol Blue Black. They were directly fed as starting materials without additives. The experiments were conducted under argon atmospheric at 313 K using a batch type reactor. The products were directly analyzed by UV-Vis (ultra violet-visible) spectrophotometer V-550. The decoloration rate increased with increasing peak pulse voltage and pulse numbers, presumably due to the increased electric field energy. Based on these results, the present system may be promising.

Fabrication of gold and silver nanoparticles with pulsed laser ablation under pressurized CO2

Pulsed laser ablation (PLA) has become a promising method for the synthesis of nanoclusters for photonics, electronics and medicine. In this work PLA in pressurized CO2 has been applied for fabrication of gold and silver nanoparticles. Laser ablation was performed with an excitation wavelength of 532?nm under various pressures (0.1?20?MPa), temperatures (40?80??C) of CO2 medium and ablation times (1500?9000?s). On the basis of the experimental result, it follows that structures of gold (Au) and silver (Ag) nanoparticles were significantly affected by the changes in CO2 density. The structures of gold and silver nanoparticles also changed with an increase of ablation time. From a field-emission scanning electron microscopy (FE-SEM) image of the fabricated gold nano-structured particles on silicon wafer, it was seen that a network structure of smaller gold particles was fabricated. A similar morphology of particles fabricated from silver plate was observed. Silver particles contain nanoparticles with large-varied diameter ranging from 5?nm to 1.2??m. The mechanism of nanoparticles fabrication could be observed as follows. Bigger gold/silver particles melted during the ablation process and then ejected smaller spherical nanoparticles, which formed nanoclusters attached on the molten particles.

Wet Extraction of Lipids and Astaxanthin from Haematococcus pluvialis by Liquefied Dimethyl Ether

Recently, a simple method for the extraction of lipids from wet cyanobacterial microalgae using liquefied dimethyl ether (DME) without drying, cell disruption, or heating was proposed. Herein, the versatility of this method was evaluated using Haematococcus pluvialis at 0.59 MPa and 25°C. Direct extraction of lipids from H. pluvialis of moisture-rich microalgae was successfully achieved, in a lipid extraction yield of 30.0% of the dry weight of the microalgae. The astaxanthin concentration in the extracted lipid was 0.33%, which was lower than the 1.82% achieved by the commonly-used acetone extraction, which incorporates drying and cell disruption. The carbon and hydrogen content were improved after DME extraction. In addition, 92% of water in the wet H. pluvialis was removed. Compared with other extractions, liquefied DME combines drying, cell description, and solvent extraction into one step.

Subcritical Water Extraction of Xanthone from Mangosteen (Garcinia Mangostana Linn) Pericarp

Subcritical water extraction of phenolic compounds from mangosteen pericarps was examined at temperatures of 120-180°C and pressures of 1-5 MPa using batch and semi-batch extractor. This method is a simple and environmentally friendly extraction method requiring no chemicals other than water. Under these conditions, there is possibility for the formation of phenolic compounds from mangosteen pericarps from decomposition of bounds between lignin, cellulose, and hemicellulose via autohydrolysis. In both of systems, the total phenolic content inclusive xanthone increased with increasing extraction temperature. In batch-system, the maximum yield of xanthone was 34 mg/g sample at 180°C and 3 MPa with 150 min reaction time. The total phenolic content could approach to 61 mg/g sample at 180°C and 3 MPa with 150 min extraction time. The results revealed that subcritical water extraction is applicable method for the isolation of polyphenolic compounds from other types of biomass and may lead to an advanced plant biomass components extraction technology.