Oxidative hydrolysis of Fe(Ⅱ) in the process of hydrothermal synthesis of hematite

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Fuxian Yang ◽  
Yubo Xing ◽  
Zhigan Deng ◽  
Chang Wei ◽  
Xingbin Li ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Oxidation Kinetic ◽  
Economic Benefits ◽  
Ion Concentration ◽  
Hydrolysis Rate ◽  
Second Order Reaction ◽  
Oxidation Rates ◽  
Application Potential ◽  
Zinc Hydrometallurgy ◽  
Hydrolysis Of

Abstract Iron removal is an important step in zinc hydrometallurgy, and hematite process not only can effectively remove iron, but also is environmentally friendly and has certain economic benefits, so it has great application potential in zinc hydrometallurgy. The oxidative hydrolysis of Fe(Ⅱ) was studied by the change of ions in solution with different initial ferrous ion concentration. Meanwhile, the oxidation rates of Fe(Ⅱ) at different initial Zn(Ⅱ) concentrations were also studied. The results show that temperature has an important influence on the oxidative hydrolysis of Fe(Ⅱ). Increasing the temperature can inhibit the formation of complex and make more Fe(Ⅱ) precipitate directly in the form of hematite, which is not limited by the hydrolysis rate of Fe(Ⅲ). The oxidation reaction of Fe(Ⅱ) approximately conforms to the second order reaction rate. Zinc sulfate can promote the oxidation of Fe(Ⅱ). When the initial Zn(Ⅱ) concentration was 20, 40, 60 and 80 g/L, the oxidation kinetic constants of Fe(Ⅱ) were 2.433, 4.492, 10.106 and 14.857 L·mol−1·min−1, respectively.

scholarly journals Stability of unimolecular films of 32P-labelled lecithin

1967 ◽  
Vol 105 (1) ◽  
pp. 401-407 ◽  
Author(s):  
H. Hauser ◽  
R. M. C. Dawson
Keyword(s):  
Pressure Change ◽  
Ion Concentration ◽  
Hydrolysis Rate ◽  
Ion Distribution ◽  
Rapid Perfusion ◽  
Poisson Boltzmann ◽  
Rate Of Hydrolysis ◽  
Poisson Boltzmann Equation ◽  
The Stability ◽  
Hydrolysis Of

1. The stability of monolayers of a highly unsaturated yeast lecithin labelled with 32P has been investigated by a surface radioactivity technique. 2. Lecithin films on distilled water at all surface pressures between 6 and 48dynes/cm. were completely stable on rapid perfusion of the subphase and on addition of ionic amphipathic substances to the film. 3. Ultrasonically treated lecithin added to the subphase caused a slow loss of surface radioactivity but little pressure change. 4. The addition of proteins to the subphase caused negligible changes in the film even when conditions were favourable for electrostatic heterocoagulation and penetration. 5. Lecithin films were not hydrolysed by a strongly acid subphase at room temperature. The very low rate of hydrolysis produced by alkali was proportional to the subphase OH−ion concentration: the apparent activation energy and temperature coefficient (Q10) of the reaction were 14250 cal. and 2·37 respectively. 6. Alkaline hydrolysis of lecithin monolayers was markedly stimulated by adding methanol (10–20%, v/v) to the subphase. The addition of ionic amphipaths to the monolayer had the expected type of effect on the hydrolysis rate, but its magnitude was far less than that suggested by an application of the Poisson–Boltzmann equation for ion distribution at a charged interface (Davies & Rideal, 1963).

Effect of OH- Concentration on Alkaline Hydrolysis of Diphenyl (4-Nitrophenyl) Phosphate Catalyzed by 2-Iodosobenzoic and 3-Iodoso-2-naphthoic Acids

1994 ◽  
Vol 59 (5) ◽  
pp. 1137-1144 ◽  
Author(s):  
Aleš Ptáček ◽  
Jiří Kulič
Keyword(s):  
Alkaline Hydrolysis ◽  
Reaction Rate ◽  
Ion Concentration ◽  
Molar Ratio ◽  
Hexadecyltrimethylammonium Bromide ◽  
Ph Values ◽  
Nitrophenyl Phosphate ◽  
Naphthoic Acid ◽  
Iodosobenzoic Acid ◽  
Hydrolysis Of

The hydrolysis of diphenyl (4-nitrophenyl) phosphate catalyzed by 2-iodosobenzoic and 3-iodoso-2-naphthoic acids has been studied at different pH values in the presence of hexadecyltrimethylammonium bromide as a micellar agent. It was found that 3-iodoso-2-naphthoic acid is better catalyst than 2-iodosobenzoic acid. At amounts of the acids higher than stoichiometric, the reaction is independent of pH in the 8.00 to 10.00 region while on using substoichiometric amounts, the reaction rate depends on OH- ion concentration only when the acid to diphenyl (4-nitrophenyl) phosphate molar ratio amounts to 12.5 : 1 for 2-iodosobenzoic acid and 6.25 : 1 for 3-iodoso-2-naphthoic acid.

Upgrading to nutrient removal by means of internal carbon from sludge hydrolysis

1994 ◽  
Vol 29 (12) ◽  
pp. 31-40 ◽  
Author(s):  
Pia Prohaska Brinch ◽  
Kim Rindel ◽  
Kathryn Kalb
Keyword(s):  
Reaction Rate ◽  
Wastewater Treatment Plants ◽  
Secondary Treatment ◽  
N Removal ◽  
Sludge Hydrolysis ◽  
Speed Up ◽  
On Line ◽  
Full Scale Tests ◽  
Biological Phosphorus ◽  
Hydrolysis Of

Due to the introduction of stricter nutrient effluent standards, many existing wastewater treatment plants performing only primary or secondary treatment are about to be upgraded. As the space available at the plants is, however, often limited, processes are required which will accommodate the need for increased treatment capacity without requiring much more space. In the hydrolysis of primary or pre-precipitated sludge direct-degradable organic carbon is produced which can speed up the reaction rate and increase both biological phosphorus and nitrogen removal. Full-scale tests with dosing of hydrolysate for biological P and N removal, respectively, have shown that this is a most viable process. The use of on-line monitoring has improved the process further.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

scholarly journals Novel activity of angiotensin-converting enzyme. Hydrolysis of cholecystokinin and gastrin analogues with release of the amidated C-terminal dipeptide

1989 ◽  
Vol 262 (1) ◽  
pp. 125-130 ◽  
Author(s):  
P Dubreuil ◽  
P Fulcrand ◽  
M Rodriguez ◽  
H Fulcrand ◽  
J Laur ◽  
...  
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Chloride Ion ◽  
Peptide Bond ◽  
Major Product ◽  
Enzyme Hydrolysis ◽  
Ion Concentration ◽  
Converting Enzyme ◽  
Rabbit Lung ◽  
Hydrolysis Of

ACE (angiotensin-converting enzyme; peptidyl dipeptidase A; EC 3.4.15.1), cleaves C-terminal dipeptides from active peptides containing a free C-terminus. We investigated the hydrolysis of cholecystokinin-8 [CCK-8; Asp-Tyr(SO3H)-Met-Gly-Trp-Met-Asp-Phe-NH2] and of various gastrin analogues by purified rabbit lung ACE. Although these peptides are amidated at their C-terminal end, they were metabolized by ACE to several peptide fragments. These fragments were analysed by h.p.l.c., isolated and identified by comparison with synthetic fragments, and by amino acid analysis. The initial and major site of hydrolysis was the penultimate peptide bond, which generated a major product, the C-terminal amidated dipeptide Asp-Phe-NH2. As a secondary cleavage, ACE subsequently released di- or tri-peptides from the C-terminal end of the remaining N-terminal fragments. The cleavage of CCK-8 and gastrin analogues was inhibited by ACE inhibitors (Captopril and EDTA), but not by other enzyme inhibitors (phosphoramidon, thiorphan, bestatin etc.). Hydrolysis of [Leu15]gastrin-(14-17)-peptide [Boc (t-butoxycarbonyl)-Trp-Leu-Asp-Phe-NH2] in the presence of ACE was found to be dependent on the chloride-ion concentration. Km values for the hydrolysis of CCK-8, [Leu15]gastrin-(11-17)-peptide and Boc-[Leu15]gastrin-(14-17)-peptide at an NaCl concentration of 300 mM were respectively 115, 420 and 3280 microM, and the catalytic constants were about 33, 115 and 885 min-1. The kcat/Km for the reactions at 37 degrees C was approx. 0.28 microM-1.min-1, which is approx. 35 times less than that reported for the cleavage of angiotensin I. These results suggest that ACE might be involved in the metabolism in vivo of CCK and gastrin short fragments.

scholarly journals Vinyl ether hydrolysis. XIV. 2-Methoxy-2,3-dihydropyran: concurrent reaction of vinyl ether and acetal functional groups

1980 ◽  
Vol 58 (21) ◽  
pp. 2199-2202 ◽  
Author(s):  
R. A. Burt ◽  
Y. Chiang ◽  
A. J. Kresge
Keyword(s):  
Vinyl Ether ◽  
Isotope Effect ◽  
Reaction Rate ◽  
Functional Group ◽  
Minor Amount ◽  
Cyanoacetic Acid ◽  
Buffer Solutions ◽  
Hydrogen Isotope Effect ◽  
A Minor ◽  
Hydrolysis Of

The hydrolysis of 2-methoxy-2,3-dihydropyran shows a normal isotope effect (kH/kD > 1) under catalysis by the hydrogen ion and gives an accurately linear dependence of reaction rate upon undissociated acid concentration in cyanoacetic acid and formic acid buffer solutions. This substrate, therefore, unlike its higher homolog, 9-methoxyoxacyclonon-2-ene, provides no evidence in support of an anything but a normal mechanism for vinyl ether hydrolysis. Analysis of the hydrogen isotope effect suggests that a minor amount (8%) of this hydrolysis occurs via reaction of the acetal functional group.

scholarly journals Kinetics of Enzymatic Hydrolysis of Southeast Sulawesi Sago Starch

2020 ◽  
pp. 53-61
Author(s):  
Ansharullah Ansharullah ◽  
Muhammad Natsir
Keyword(s):  
Enzymatic Hydrolysis ◽  
Maximum Velocity ◽  
Enzyme Concentration ◽  
Hydrolysis Rate ◽  
Sago Starch ◽  
Optimum Conditions ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations ◽  
Menten Constant

The aims of this study were to characterize the kinetics of enzymatic hydrolysis of sago starch, obtained from Southeast Sulawesi Indonesia. The enzyme used for hydrolysis was bacterial ∝-amylase (Termamyl 120L from Bacillus licheniformis, E. C. 3.2.1.1).  The method to determine the initial velocity (Vo) of the hydrolysis was developed by differentiation a nonlinear equation (NLE).  The Vo of the hydrolysis was measured at various pH (6.0, 6.5,and 7.0), temperatures (40, 60, 75 and 95oC), enzyme concentrations (0.5, 1.0, 1.5 and 2.0 µg per mL) and in the presence of 70 ppm Ca++. The optimum conditions of this experiment were found to be at pH 6.5 – 7.0 and 75oC, and the Vo increased with increasing enzyme concentration. The Vo values at various substrate concentrations were also determined, which were then used to calculate the enzymes kinetics constant of the hydrolysis, including Michaelis-Menten constant (Km) and maximum velocity (Vmax) using a Hanes plot.  Km and Vmax values were found to be higher in the measurement at pH 7.0 and 75oC. The Km values  at four  different combinations of pH and temperatures (pH 6.5, 40oC; pH 6.5, 75oC; pH 7.0, 40oC; pH 7.0, 75oC) were found to be 0.86, 3.23, 0.77 and 3.83 mg/mL, respectively; and Vmax values were 17.5, 54.3, 20.3 and 57.1 µg/mL/min, respectively. The results obtained showed that hydrolysis rate of this starch was somewhat low.

scholarly journals The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate

2000 ◽  
Vol 65 (12) ◽  
pp. 857-866
Author(s):  
Mladjen Micevic ◽  
Slobodan Petrovic
Keyword(s):  
Kinetic Data ◽  
Reaction Rate ◽  
Frequency Factor ◽  
Reaction Rate Constant ◽  
Order Reaction ◽  
Activation Entropy ◽  
Second Order Reaction ◽  
Third Order ◽  
First Order ◽  
Kinetics Of

The alcoholysis of 1,2,2-trimethylpropyl-methylfluorophosphonate (soman) was examined with a series of alkoxides and in corresponding alcohols: methanol, ethanol, 1-propanol, 2-propanol, 2-methoxyethanol and 2-ethoxyethanol. Soman reacts with the used alkoxides in a second order reaction, first order in each reactant. The kinetics of the reaction between 1,2,2-trimethylpropyl-methylfluorophosphonate and ethanol in the presence of diethylenetriamine was also examined. A third order reaction rate constant was calculated, first order in each reactant. The activation energy, frequency factor and activation entropy were determined on the basis of the kinetic data.

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