Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Potassium Compounds”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64Linked to original sources
PubMed2004

Synthesis and characterization of vegetable oil derived esters: evaluation for their diesel additive properties.

Trans-esterification of four vegetable oils; canola oil, greenseed canola oil from heat-damaged seeds, processed waste fryer grease and unprocessed waste fryer grease, was carried out using methanol, and KOH as catalyst. The methyl esters of the corresponding oils were separated from the crude glycerol, purified, and characterized by various methods to evaluate their densities, viscosities, iodine values, acid numbers, cloud points, pour points and gross heat of combustion, fatty acid and lipid compositions, lubricity properties, and thermal properties. The fatty acid composition suggests that 80-85% of the ester was from unsaturated acids. Substantial decrease in density and viscosity of the methyl esters compared to their corresponding oils suggested that the oils were in their mono or di glyceride form. The lubricity of the methyl esters, when blended at 1 vol% treat rate with ISOPAR M reference fuel, showed that the canola methyl ester enhanced the fuel's lubricity number. From the analyses performed, it was determined that the ester with the most potential for being an additive or a substitute for diesel fuel is the canola methyl ester, whose physical and chemical characteristics are similar to diesel fuel.

Calorimetry, Differential Scanning↗
PubMed2004

Integrated biodiesel production: a comparison of different homogeneous catalysts systems.

The most common catalysts for biodiesel production are homogeneous basic catalysts. In the present paper, a comparison is made of different basic catalysts (sodium methoxide, potassium methoxide, sodium hydroxide and potassium hydroxide) for methanolysis of sunflower oil. All the reactions were carried out under the same experimental conditions in a batch stirred reactor and the subsequent separation and purification stages in a decanter. The analytical methods included gas chromatography and the determination of fat and oil conventional parameters. The biodiesel purity was near 100 wt.% for all catalysts. However, near 100 wt.% biodiesel yields were only obtained with the methoxide catalysts. According to the material balance of the process, yield losses were due to triglyceride saponification and methyl ester dissolution in glycerol. Obtained biodiesel met the measured specifications, except for the iodine value, according to the German and EU draft standards. Although all the transesterification reactions were quite rapid and the biodiesel layers achieved nearly 100% methyl ester concentrations, the reactions using sodium hydroxide turned out the fastest.

Bioreactors↗
PubMed2004

Pb2+ removal from aqueous solution using crab shell treated by acid and alkali.

In order to investigate the process of Pb(2+) removal by crab shell, the effects of pretreatment of crab shell with acid and alkali on Pb(2+) removal by crab shell were examined. In acid treatment of crab shell with HCl for the demineralization of crab shell, Ca(2+) and Mg(2+) in crab shell were largely extracted during the acid treatment and the Pb(2+) removal by acid treated crab shell was very low. The total released Ca(2+) and Mg(2+) amounts in the alkali treated crab shell during Pb(2+) removal were not greatly different from those in the untreated crab shell. However, the times to reach an equilibrium state were quite shortened by alkali treatment and the reason was explained by transmission electron microscope.

Adsorption↗
PubMed2005

Preparation of biodiesel from crude oil of Pongamia pinnata.

Biodiesel was prepared from the non-edible oil of Pongamia pinnata by transesterification of the crude oil with methanol in the presence of KOH as catalyst. A maximum conversion of 92% (oil to ester) was achieved using a 1:10 molar ratio of oil to methanol at 60 degrees C. Tetrahydrofuran (THF), when used as a co-solvent increased the conversion to 95%. Solid acid catalysts viz. Hbeta-Zeolite, Montmorillonite K-10 and ZnO were also used for this transesterification. Important fuel properties of methyl esters of Pongamia oil (Biodiesel) compare well (Viscosity = 4.8 Cst @ 40 degrees C and Flash point = 150 degrees C) with ASTM and German biodiesel standards.

Biotechnology↗
PubMed2005

Effect of culture media and conditions on polyunsaturated fatty acids production by Mortierella alpina.

To improve the polyunsaturated fatty acid (PUFA) production by Mortierella, culture media and conditions were investigated. M. alpina ATCC 32222 had the highest yield of arachidonic acid, gamma-linolenic acid and linoleic acid among 11 test microbes. Soluble starch at 10% and the mixture of KNO3 and yeast extract at 2:1 (w/w) was the best carbon and nitrogen sources for arachidonic acid and total PUFAs production, respectively. The optimal C/N ratio ranged from 5.1 to 9.0. Each gram of carbon produced 17.4 mg of linoleic acid, 17.0 mg of gamma-linolenic acid, 103.0 mg of arachidonic acid and 194.2 mg of total PUFAs at 20 degrees C, while it yielded 21.4 mg of linoleic acid, 25.6 mg of gamma-linolenic acid, 2.6 mg of gamma-linolenic acid, 110.3 mg of arachidonic acid, 4.3 mg of eicosapentaenoic acid and 218.4 mg of total PUFAs at 12 degrees C. A high degree of unsaturation was found at low temperature incubation. Linseed oil supplementation (1%, w/v) increased the PUFAs production and each gram of carbon produced 403.4 mg of alpha-linolenic acid, 123.1 mg of arachidonic acid, 33.6 mg of eicosapentaenoic acid, 1.68 mg of docosahexaenoic acid and 943.2 mg of total PUFAs. From the optimization of culture media and conditions, PUFAs production increased from 30% to 5 times that was optimal for practical use.

Analysis of Variance↗
PubMed2005

Process effects on activated carbon with large specific surface area from corn cob.

The main factors that affect the large specific surface area (SSA) of the activated carbon from agricultural waste corn cobs were studied by chemically activated method with solution of KOH and soap which acted as surfactant. The experiment showed that not only the activation temperature, activation time and the mass ratio of KOH to the carbonized material, but also the activated methods using activator obviously influenced the SSA of activated carbon. The experimental operating conditions were as follows: the carbonized temperature being 450 degrees C and keeping time being 4 h using N2 as protective gas; the activation temperature being 850 degrees C and holding time being 1.2 h; the mass ratio of KOH to carbonized material being 4.0; the time of soaking carbonized material in the solution of KOH and soap being 30 min. Under the optimal conditions, the SSA of activated carbon from corn cobs reached 2700 m2/g. And the addition of the soap as surfactant may shorten the soaking time. The structure of the activated carbon prepared had narrow distribution of pore size and the micro-pores accounted for 78%. The advantages of the method described were easy and feasible.

Carbon↗
PubMed2005

High surface area activated carbon prepared from cassava peel by chemical activation.

Cassava is one of the most important commodities in Indonesia, an agricultural country. Cassava is one of the primary foods in our country and usually used for traditional food, cake, etc. Cassava peel is an agricultural waste from the food and starch processing industries. In this study, this solid waste was used as the precursor for activated carbon preparation. The preparation process consisted of potassium hydroxide impregnation at different impregnation ratio followed by carbonization at 450-750 degrees C for 1-3 h. The results revealed that activation time gives no significant effect on the pore structure of activated carbon produced, however, the pore characteristic of carbon changes significantly with impregnation ratio and carbonization temperature. The maximum surface area and pore volume were obtained at impregnation ratio 5:2 and carbonization temperature 750 degrees C.

Charcoal↗
PubMed2005

Optimization of alkali-catalyzed transesterification of Pongamia pinnata oil for production of biodiesel.

Studies were carried out on transesterification of Karanja oil with methanol for the production of biodiesel. The reaction parameters such as catalyst concentration, alcohol/oil molar ratio, temperature, and rate of mixing were optimized for production of Karanja oil methyl ester (KOME). The fatty acid methyl esters content in the reaction mixture were quantified by HPLC and 1H NMR method. The yield of methyl esters from Karanja oil under the optimal condition was 97-98%.

Biotechnology↗
PubMed2006

Soybean oil methyl esters preparation using NaX zeolites loaded with KOH as a heterogeneous catalyst.

The transesterification of soybean oil with methanol to methyl esters was carried out using NaX zeolites loaded with KOH as a solid base catalyst. Best result was obtained with NaX zeolite loaded with 10% KOH, followed by heating at 393 K for 3 h. When the transesterification reaction was carried out at reflux of methanol (338 K), with a 10:1 molar ratio of methanol to soybean oil, a reaction time of 8 h and a catalyst amount of 3 wt.%, the conversion of soybean oil was 85.6%.

Catalysis↗
PubMed2006

NH(4)OH-KOH pulping mechanisms and kinetics of rice straw.

The mechanisms and kinetics of NH(4)OH-KOH mixture pulping rice straw were studied. When aqueous ammonia was mixed with a small amount of caustic potash (ratio of 1:5), three distinct delignification phases were observed in the pulping process: a bulk delignification phase from the beginning of the cooking period to 100 degrees C, a supplementary delignification phase from 100 degrees C to 155 degrees C lasting a further 45 min, and a residual delignification phase until the end of the cooking period. There were two silica removal phases; the first phase was from the beginning of the cooking period to 100 degrees C and the second phase was from 100 degrees C to the end of the cooking period. The rate of delignification reaction was first order with respect to residual lignin and 0.3 order with respect to [OH(-)]. The silica removal was pseudo-first-order with respect to residual silica and 0.6 order with respect to [OH(-)]. The activation energies of the delignification and removal of silica reactions were 35.6 and 30.9 kJ/mol, respectively.

Ammonium Hydroxide↗
PubMed2006

Optimisation of integrated biodiesel production. Part II: a study of the material balance.

A study was made of the material balance for the fatty acid methyl ester (biodiesel) synthesis from sunflower oil using potassium hydroxide as the catalyst. A factorial design of experiments and a central composite design have been used to evaluate the influence of operating conditions on the process material balance. The responses chosen were the biodiesel yield and the yield losses due to triglyceride saponification and methyl ester dissolution in glycerol, while the variables studied were temperature, initial catalyst concentration and the methanol:vegetable oil molar ratio. The biodiesel yield increased and therefore the yield losses decreased by decreasing catalyst concentration and temperature. However, the methanol:sunflower oil molar ratio did not affect the material balance variables significantly. Second-order models were obtained to predict the biodiesel yield and both yield losses. Within the experimental range studied, these models largely matched the results from the experiments.

Biotechnology↗
PubMed2006

Optimisation of integrated biodiesel production. Part I. A study of the biodiesel purity and yield.

This study consists of the development and optimisation of the potassium hydroxide-catalysed synthesis of fatty acid methyl esters (biodiesel) from sunflower oil. A factorial design of experiments and a central composite design have been used. The variables chosen were temperature, initial catalyst concentration by weight of sunflower oil and the methanol:vegetable oil molar ratio, while the responses were biodiesel purity and yield. The initial catalyst concentration is the most important factor, having a positive influence on biodiesel purity, but a negative one on biodiesel yield. Temperature has a significant positive effect on biodiesel purity and a significant negative influence on biodiesel yield. The methanol:vegetable oil molar ratio is only significant for the biodiesel purity, having a positive influence. Second-order models were obtained to predict biodiesel purity and yield as a function of these variables. The best conditions are 25 degrees C, a 1.3%wt for the catalyst concentration and a 6:1 methanol:sunflower oil molar ratio.

Bioreactors↗
PubMed2006

The effect of agitation intensity on alkali-catalyzed methanolysis of sunflower oil.

The sunflower oil methanolysis was studied in a stirred reactor at different agitation speeds. The measurements of drop size, drop size distribution and the conversion degree demonstrate the effects of the agitation speed in both non-reaction (methanol/sunflower oil) and reaction (methanol/KOH/sunflower oil) systems. Drop size distributions were found to become narrower and shift to smaller sizes with increasing agitation speed as well as with the progress of the methanolysis reaction at a constant agitation speed. During the methanolysis reaction, the Sauter-mean drop diameter stays constant in the initial slow reaction region, rapidly decreases during the fast reaction period and finally reaches the equilibrium level. Due to the fact that the interfacial area increases, one can conclude that the rate of reaction occurring at the interface will also be enhanced progressively. The "autocatalytic" behavior of the methanolysis reaction is explained by this "self-enhancement" of the interfacial area, due to intensive drop breakage process.

Emulsions↗
PubMed2006

Amperometric detection of insulin at renewable sol-gel derived carbon ceramic electrode modified with nickel powder and potassium octacyanomolybdate(IV).

A renewable three-dimensional chemically modified carbon ceramic electrode (CCE) containing nickel powder and K4[Mo(CN)8] was constructed by sol-gel technique. The electrochemical properties and stability of modified electrode was evaluated by cyclic voltammetry in pH range 4-10. The redox couple of [Mo(CN)8] (4-/3-) was shown both as a solute in electrolyte solution and as a component of a carbon based conducting composite electrode. The apparent electron transfer rate constant (ks) and transfer coefficient (alpha) were determined by cyclic voltammetry and they were about 17.1 and 0.57 s(-1), respectively. The catalytic activity of the modified CCE toward insulin oxidation was investigated at pH range of 3-8 by cyclic votammetry. The modified electrode showed excellent electrocatalytic activity toward insulin electroxidation at physiological pH value. The modified electrode was used for insulin detection chronoamperometrically at pH 7. Under optimized condition in amperometry method, the concentration calibration range, detection limit and sensitivity were 0.5-500 nM, 0.45 nM and 6140 nA/microM, respectively. Flow injection amperometric determination of insulin at pH 7.4, at this modified electrode yielded a calibration curve with the following characteristics, linear dynamic range 100-500 pM; sensitivity 8.1 nA/nM and detection limit 40 pM (based on S/N = 3). The inherent stability at wide pH range, high sensitivity, low detection limit, low cost and ease of preparation are of advantageous of this insulin sensor. This sensor indicates great promise for monitory insulin in chromatographic effluents.

Animals↗
PubMed2006

Antibiotic-conjugated polyacrylate nanoparticles: new opportunities for development of anti-MRSA agents.

This report describes the preparation of polyacrylate nanoparticles in which an N-thiolated beta-lactam antibiotic is covalently conjugated onto the polymer framework. These nanoparticles are formed in water by emulsion polymerization of an acrylated antibiotic pre-dissolved in a liquid acrylate monomer (or mixture of co-monomers) in the presence of sodium dodecyl sulfate as a surfactant and potassium persulfate as a radical initiator. Dynamic light scattering analysis and electron microscopy images of these emulsions show that the nanoparticles are approximately 40 nm in diameter. The emulsions have potent in vitro antibacterial properties against methicillin-resistant Staphylococcus aureus and have improved bioactivity relative to the non-polymerized form of the antibiotic. A unique feature of this methodology is the ability to incorporate water-insoluble drugs directly into the nanoparticle framework without the need for post-synthetic modification. Additionally, the antibiotic properties of the nanoparticles can be modulated by changing the length or location of the acrylate linker on the drug monomer.

Acrylic Resins↗
PubMed2006

Ion solvation and water structure in potassium halide aqueous solutions.

The structure of water and the nature of ionic hydration is explored in aqueous solutions of potassium fluoride, chloride, bromide and iodide over a range of concentrations up to 4.8 ion pairs per 100 water molecules, using the combined techniques of neutron diffraction with hydrogen isotope substitution. The diffraction data are interpreted using the method of empirical potential structure refinement, which attempts to build a three-dimensional model of the scattering system consistent with the diffraction data. The water structure is strongly perturbed in the first hydration shells of both anion and cation, but is found to be only mildly perturbed outside of this region, with the largest effects occurring with the smallest anion and highest concentrations. For the potassium ion there are strong orientational correlations in the first hydration shell, with the water molecules lying with their dipole moments pointing almost directly away from the cation on average, but with an angular spread of approximately +/-60 degrees which is mildly dependent on the anion type present. For all the anions the water molecules in the first shell are strongly oriented with one O-H vector pointing directly towards the anion on average, with an angular spread of approximately +/-10 degrees for F(-), increasing to approximately +/-22 degrees for I(-). For both anions and cations the second hydration shell is much more disordered than the first, but there is a weak pattern of orientational correlation which becomes more pronounced with the larger anions. There is some evidence that the fluoride ion structures water significantly in its first hydration shell, but not beyond. The findings throw further light on recent findings that the orientational relaxation time for water outside the first shell of dissolved ions is the same as in the bulk liquid.

Halogens↗
PubMed2004

FT-IR study of the Chara corallina cell wall under deformation.

Fourier-transform infrared (FT-IR) microspectroscopy was used to investigate both the chemical composition of, and the effects of an applied strain on, the structure of the Chara corallina cell wall. The inner layers of the cell wall are known to have a transverse cellulose orientation with a gradient through the thickness to longitudinal orientation in the older layers. In both the native state and following the removal of various biopolymers by a sequential extraction infrared dichroism was used to examine the orientation of different biopolymers in cell-wall samples subjected to longitudinal strain. In the Chara system, cellulose microfibrils were found to be aligned predominantly transverse to the long axis of the cell and became orientated increasingly transversely as longitudinal strain increased. Simultaneously, the pectic polysaccharide matrix underwent molecular orientation parallel to the direction of strain. Following extraction in CDTA, microfibrils were orientated transversely to the strain direction, and again the degree of transverse orientation increased with increasing strain. However, the pectic polysaccharides of the matrix were not detected in the dichroic difference spectra. After a full sequential extraction, the cellulose microfibrils, now with greatly reduced crystallinity, were detected in a longitudinal direction and they became orientated increasingly parallel to the direction of strain as it increased.

Carbonates↗