Kinetic Modeling of Malonylgenistin and Malonyldaidzin Conversions under Alkaline Conditions and Elevated Temperatures

2007 ◽  
Vol 55 (9) ◽  
pp. 3408-3413 ◽  
Author(s):  
Nirupama A. Vaidya ◽  
Kevin Mathias ◽  
Baraem Ismail ◽  
Kirby D. Hayes ◽  
Carlos M. Corvalan
Keyword(s):  
Kinetic Modeling ◽  
Elevated Temperatures ◽  
Alkaline Conditions

scholarly journals Research on Mechanical Performance & Behaviour of Geopolymer Concrete Subjected to Elevated Temperatures

2019 ◽  
Vol 8 (2S8) ◽  
pp. 883-887
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Elevated Temperatures ◽  
Mechanical Performance ◽  
Geopolymer Concrete ◽  
Sem Images ◽  
Before And After ◽  
Alkaline Conditions ◽  
Compressive Strength Of Concrete

The investigative studies on mechanical performance & behaviour, of Geopolymer Concrete (GPC) before and after the exposure to elevated temperatures (of 200 0 C -1000 0 C with an increment of 100 0 C). Indicate that the GPC Specimens Exhibited better Compressive strength at higher temperatures than that of those made by regular OPC Concrete with M30 Grade. The chronological changes in the geopolymeric structure upon exposure to these temperatures and their reflections on the thermal behaviour have also been explored. The SEM images indicate GPC produced by fly ash , metakaolin and silica fume, under alkaline conditions form Mineral binders that are not only non-flammable and but are also non-combustible resins and binders. Further the Observations drawn disclose that the mass and compressive strength of concrete gets reduced with increase in temperatures.

Laminar flame characteristics and kinetic modeling study of methanol-isooctane blends at elevated temperatures

Fuel ◽  
2016 ◽  
Vol 184 ◽  
pp. 836-845 ◽  
Author(s):  
Qianqian Li ◽  
Weijie Zhang ◽  
Wu Jin ◽  
Yongliang Xie ◽  
Zuohua Huang
Keyword(s):  
Kinetic Modeling ◽  
Elevated Temperatures ◽  
Laminar Flame ◽  
Modeling Study

Destruction of Iron-Complexed Cyanide by Alkaline Hydrolysis

1989 ◽  
Vol 21 (6-7) ◽  
pp. 547-558 ◽  
Author(s):  
Stephen J. Robuck ◽  
Richard G. Luthy
Keyword(s):  
Alkaline Hydrolysis ◽  
Elevated Temperatures ◽  
Appropriate Technology ◽  
Industrial Wastes ◽  
Hydrolysis Reaction ◽  
Hydrolysis Rate ◽  
Aluminum Reduction ◽  
Metal Cyanide ◽  
Alkaline Conditions ◽  
Cyanide Complexes

Iron-complexed cyanide compounds are found in various industrial wastes, and are resistant to destruction by conventional technologies used to treat cyanide-bearing wastes. This study evaluated hydrolytic destruction of iron-complexed cyanide in leachates from land disposal of spent carbonanceous material used to line aluminum reduction cells. The investigation showed that iron-cyanide complexes may be hydrolyzed under alkaline conditions at elevated temperatures and pressures, e.g. in the range of 165-180 °C and 100-150 psig. The hydrolysis reaction is apparently first-order with respect to total cyanide. The reaction yields stoichiometric amounts of ammonia and formate, and Fe3O4(s). The rate of the reaction is especially temperature dependent, and for the case of spent potlining leachate, the hydrolysis rate may be estimated by an Arrhenius kinetic expression for hydrolysis of simple cyanide. The rate of the hydrolysis reaction for iron-complexed cyanide is compared to that for other metal-cyanide complexes. It is shown that waste composition may affect the hydrolysis rate, and that the instability of certain metal-cyanide complexes with respect to alkaline chlorination does not correlate with instability with respect to alkaline hydrolysis. Alkaline hydrolysis is an appropriate technology for destruction of iron- and other metal-cyanide compounds in wastes at high concentrations.

scholarly journals Phosphorus Fractions and Release Factors in Surface Sediments of a Tailwater River in Xinmi City, a Case Study

2021 ◽  
Vol 13 (10) ◽  
pp. 5417
Author(s):  
Shanheng Huang ◽  
Hongbin Xu ◽  
Dan Shang ◽  
Junzhao Liu ◽  
Qiuju Tang ◽  
...  
Keyword(s):  
Total Phosphorus ◽  
Elevated Temperatures ◽  
Organic Phosphorus ◽  
Paper Industry ◽  
Phosphorus Release ◽  
Overlying Water ◽  
Sewage Plant ◽  
P Content ◽  
Hydrodynamic Disturbance ◽  
Alkaline Conditions

The Shuangji River in Xinmi City is a tailwater-type river. Its main water sources are the effluent from the domestic sewage plant, the effluent from the paper industry sewage plant and the coal well. The construction of wastewater treatment facilities in Xinmi city has significantly reduced the amount of total phosphorus (TP) discharged into Shuangji River. However, phosphorus control in rivers where the overlying waters are predominantly tailwaters is still a challenge, especially as the sediment–water interface’s phosphorus exchange mechanism needs to be investigated in detail. In this study, the content and proportion of each phosphorus fraction in the sediment of a tailwater-type river, the Shuangji River, were determined. It was found that the organic phosphorus (OP) and iron-bound phosphorus (Fe-P) content and proportion were high, and the risk of release was relatively high in the section of the river where the overlying water was the tailwater of a sewage plant. Temperature, pH, dissolved oxygen, and hydraulic disturbance were also found to control phosphorus forms’ transformation and release in the sediment. Elevated temperatures mainly stimulated the release of OP and Fe-P from the sediments. The dissolution of calcium-bound phosphorus (Ca-P) is the main pathway for phosphorus release under acidic conditions, whereas, under alkaline conditions, phosphorus release is mainly controlled by ion exchange between OH− and Fe-P and metal oxide-bound phosphorus (Al-P). Aerobic versus anaerobic conditions cause changes in Fe-P content in the sediment mainly by changing Fe ions’ chemical valence. Hydrodynamic disturbance accelerates labile-P release, but once the hydrodynamic disturbance stops, the overlying water dissolved total phosphorus (DTP) concentration rapidly decreases to a similar concentration as before.

scholarly journals Stability of gamma-valerolactone under pulping conditions as a basis for process optimization and chemical recovery

Cellulose ◽  
2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Leena Pitkänen ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Treatment Time ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
Ph Range ◽  
Spent Liquor

AbstractThis study focuses on the investigation of the extent of the γ-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of a 50 wt% GVL solution to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2 × 10–5 wt% to 6 wt%) at elevated temperatures (150–180 °C) and reaction times between 30 and 180 min caused the formation of 4 mol% 4-HVA. However, with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at a constant time (30 min) and temperature (180 °C) with the variation of the NaOH concentration (0.2 × 10–6 wt% to 7 wt%). The addition of less than 0.2 wt% of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The degree of decomposition after treatment was determined by NMR analysis. To verify the GVL stability under practical conditions, Betula pendula sawdust was fractionated in 50 wt% GVL with and without the addition of H2SO4 or NaOH at 180 °C and a treatment time of 120 min. The spent liquor was analyzed and a 4-HVA content of 5.6 mol% in a high acidic (20 kg H2SO4/t wood) and 6.0 mol% in an alkaline (192 kg NaOH/t wood) environment have been determined.

Alkali-based pre-treatment may prevent ochratoxin A in grapes

2016 ◽  
Vol 9 (4) ◽  
pp. 517-523 ◽  
Author(s):  
S. Özcan ◽  
V. Gökmen
Keyword(s):  
Ochratoxin A ◽  
Potassium Carbonate ◽  
High Performance ◽  
Elevated Temperatures ◽  
Alkali Treatment ◽  
Good Manufacturing Practice ◽  
Amide Bond ◽  
Aspergillus Ochraceus ◽  
Alkaline Conditions ◽  
Pre Treatment

In traditional raisin production process in Turkey, one of the major raisin producers in the world, grapes undergo an alkali treatment prior to drying. This procedure involves dipping grapes in a potassium carbonate solution for 10-15 seconds to remove the wax layer on the surface to accelerate the drying process. In this study, we aimed to investigate the effect of alkali treatment on ochratoxin A (OTA), an important risk factor for grapes and grape-derived products. First, the stability of the OTA was examined under variable pH (4-12), ion type (Na+, K+), ionic strength (0.1-10%) and temperature (4-60 °C). Then, Aspergillus ochraceus contaminated grapes were treated with an alkaline solution and a subsequent OTA analysis was performed through a high performance liquid chromatography-fluorescence detection. OTA started to decompose at pH values exceeding 10.0. The degradation followed a first order kinetics. Although both sodium carbonate and potassium carbonate solutions were at the same alkali pH and they both triggered the OTA degradation at increasing concentrations, potassium carbonate was more effective even at low concentrations. Elevated temperatures were also found to effect degradation. The degradation rate constant at 40 °C was approximately 5 times greater than the one at 25 °C. Furthermore, OTA levels dropped up to 50% in contaminated grapes after the alkali treatment. Our results confirmed that the amide bond of OTA rapidly hydrolysed to a non-toxic ochratoxin-alpha and phenylalanine under strong alkaline conditions. The results suggest that the alkaline pre-treatment unintentionally offers a great advantage to reduce OTA levels in raisins and it could be a viable approach for other dried fruits through the application of good manufacturing practice.

scholarly journals Stability of Gamma-valerolactone Under Pulping Conditions as a Basis for Process Optimization and Chemical Recovery

2021 ◽  
Author(s):  
Marianna Granatier ◽  
Inge Schlapp-Hackl ◽  
Huy Quang Lê ◽  
Kaarlo Nieminen ◽  
Herbert Sixta
Keyword(s):  
Elevated Temperatures ◽  
Reaction Times ◽  
Chemical Recovery ◽  
Wide Ph Range ◽  
Alkaline Conditions ◽  
Naoh Solution ◽  
Hydroxyvaleric Acid ◽  
The Stability ◽  
Ph Range ◽  
Spent Liquor

Abstract This study investigates the extent of the g-valerolactone (GVL) hydrolysis forming an equilibrium with 4-hydroxyvaleric acid (4-HVA) in aqueous solutions over a wide pH range. The hydrolysis of pure 50 wt% GVL to 4-HVA (3.5 mol%) was observed only at elevated temperatures. The addition of sulfuric acid (0.2×10-5 wt% to 6 wt%) at elevated temperatures (150 – 180°C) and reaction times between 30-180 min caused the formation of 4 mol% 4-HVA but with decreasing acidity, the 4-HVA remained constant at about 3 mol%. The hydrolysis reactions in alkaline conditions were conducted at constant time (30 min) and temperature (180 °C) with variation of the NaOH concentration (0.2×10-6 wt% to 7 wt%). The addition of less than 0.2 wt % of NaOH resulted in the formation of less than 4 mol% of sodium 4-hydroxyvalerate. A maximum amount of 21 mol% of 4-HVA was observed in a 7 wt% NaOH solution. The stability after synthesis was determined by NMR analysis. To verify the GVL stability results obtained under practical conditions, Betula pendula sawdust was fractionated in 50% GVL with and without addition of H2SO4 or NaOH at 180°C and 120 min, and spent liquor was analyzed. The spent liquor contained 5.6 mol% and 6.0 mol% of 4-HVA in a highly acidic (20 kg H2SO4/t wood) and alkaline (192 kg NaOH/ t wood) environment, respectively.

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

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