Amorphous and crystalline calcium carbonate phases during carbonation of nanolimes: implications in heritage conservation

CrystEngComm ◽  
2016 ◽  
Vol 18 (35) ◽  
pp. 6594-6607 ◽  
Author(s):  
Carlos Rodriguez-Navarro ◽  
Kerstin Elert ◽  
Radek Ševčík
Keyword(s):  
Calcium Carbonate ◽  
Crystallization Process ◽  
Heritage Conservation ◽  
First Order ◽  
First Order Kinetics

Alcohol dispersions of Ca(OH)2nanoparticles, the so-called nanolimes, carbonate in air following first order kinetics,viaa multistep, non-classical crystallization process involving amorphous and crystalline CaCO3phases.

Dissipation of Permethrin in Limnocorrals

1985 ◽  
Vol 42 (1) ◽  
pp. 70-76 ◽  
Author(s):  
K. R. Solomon ◽  
J. Y. Yoo ◽  
D. Lean ◽  
N. K. Kaushik ◽  
K. E. Day ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Water Chemistry ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Secchi Disk ◽  
Secchi Disk Depth ◽  
Southern Ontario ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Dissipation

Permethrin (3-phenoxybenzyl(1RS)-cis,trans-3-(2,2-dimethy[-3-dichlorovinyl)-2,2-dimethylcyciopropanecarboxylate) applied to approximately 100-m3 enclosures (limnocorrals) in a small mesotrophic lake in Southern Ontario (47°51′25″N; 77°25′30″W) at concentrations of 500, 50, 5, and 0.5 μ∙L−1 dissipated from the water rapidly and approximated first-order kinetics in the first 8–12 d. Time taken for 50 and 90% dissipation ranged from 1.65 and 3.65 d, respectively, at 0.5 μ∙L−1 to 3.5 and 6.75 d, respectively, at 50 μ∙L−1. Inter- and intra-seasonal replication of dissipation patterns was good. Rate of dissipation varied slightly with depth, normally being slower at greater depth. Absorption of permethrin to sediments was rapid, penetration shallow, and disappearance slow. Permethrin had no effect on water chemistry but there was an increase in the Secchi disk depth in the treated limnocorrals. Dissolved inorganic carbon decreased in all limnocorrals, including controls after treatment, suggesting precipitation of calcium carbonate which may act as a scavenging agent for permethrin in the water. Limnocorrals are a useful tool for evaluating the behavior of pesticides in the aquatic system.

scholarly journals Use of eggshells as a raw material for production of calcium preparations

2016 ◽  
Vol 34 (No. 4) ◽  
pp. 313-317 ◽  
Author(s):  
Dolińska Barbara ◽  
Jelińska Marta ◽  
Szulc-Musioł Beata ◽  
Ryszka Florian
Keyword(s):  
Calcium Carbonate ◽  
Physicochemical Properties ◽  
Calcium Release ◽  
Calcium Salt ◽  
Raw Material ◽  
Calcium Citrate ◽  
Half Time ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of

The kinetics of calcium release from tablets obtained from modified eggshells in the form of calcium citrate and calcium carbonate was investigated. Calcium release showed the first-order kinetics. After 30 min of the experiment, 79.93% of calcium was released from tablets obtained from modified eggshells in the form of calcium citrate, reaching ~100% after 3 hours. For tablets produced with calcium carbonate, these values were 7 and 60%, respectively. The half-time of calcium release from tablets containing calcium citrate was t<sub>50% </sub>= 0.5 h and for tablets containing calcium carbonate it was t<sub>50% </sub>= 2.2 h, so calcium in the form of calcium citrate was released 4 times faster. These results can be connected with different solubility of calcium salts. The hardness of tablets with calcium carbonate was by 30 N lower than the hardness of tablets with calcium citrate. It is associated with particular physicochemical properties of calcium salt. Calcium citrate can exist in several states of hydration while calcium carbonate is anhydrous. These properties have an influence on the hardness of tablets.

Photo-catalytic degradation of gaseous pollutants in paper mills of southern China

TAPPI Journal ◽  
2018 ◽  
Vol 17 (03) ◽  
pp. 167-178 ◽  
Author(s):  
Xin Tong ◽  
Jiao Li ◽  
Jun Ma ◽  
Xiaoquan Chen ◽  
Wenhao Shen
Keyword(s):  
Degradation Rate ◽  
Southern China ◽  
Catalytic Degradation ◽  
Pulp And Paper ◽  
Gaseous Pollutants ◽  
Pulp And Paper Mills ◽  
Paper Mills ◽  
Initial Concentration ◽  
First Order ◽  
First Order Kinetics

Studies were undertaken to evaluate gaseous pollutants in workplace air within pulp and paper mills and to consider the effectiveness of photo-catalytic treatment of this air. Ambient air at 30 sampling sites in five pulp and paper mills of southern China were sampled and analyzed. The results revealed that formaldehyde and various benzene-based molecules were the main gaseous pollutants at these five mills. A photo-catalytic reactor system with titanium dioxide (TiO2) was developed and evaluated for degradation of formaldehyde, benzene and their mixtures. The experimental results demonstrated that both formaldehyde and benzene in their pure forms could be completely photo-catalytic degraded, though the degradation of benzene was much more difficult than that for formaldehyde. Study of the photo-catalytic degradation kinetics revealed that the degradation rate of formaldehyde increased with initial concentration fitting a first-order kinetics reaction. In contrast, the degradation rate of benzene had no relationship with initial concentration and degradation did not conform to first-order kinetics. The photo-catalytic degradation of formaldehyde-benzene mixtures indicated that formaldehyde behaved differently than when treated in its pure form. The degradation time was two times longer and the kinetics did not reflect a first-order reaction. The degradation of benzene was similar in both pure form and when mixed with formaldehyde.

Kinetic of oxidation of methyl orange by vanadium(V) under conditions VO2+ and decavanadates coexist: Catalysis by Triton X-100 micellar medium

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Methyl Orange ◽  
Solution Ph ◽  
Vanadium Concentration ◽  
Limiting Behavior ◽  
First Order ◽  
First Order Kinetics ◽  
Ph Range ◽  
Kinetic Pattern ◽  
Triton X ◽  
Kinetics Of

The kinetics of oxidation of methyl orange by vanadium(V) {V(V)} has been investigated in the pH range 2.3-3.79. In this pH range V(V) exists both in the form of decavanadates and VO2+. The kinetic results are distinctly different from the results obtained for the same reaction in highly acidic solution (pH &lt; 1) where V(V) exists only in the form of VO2+. The reaction obeys first order kinetics with respect to methyl orange but the rate has very little dependence on total vanadium concentration. The reaction is accelerated by H+ ion but the dependence of rate on [H+] is less than that corresponding to first order dependence. The equilibrium between decavanadates and VO2+ explains the different kinetic pattern observed in this pH range. The reaction is markedly accelerated by Triton X-100 micelles. The rate-[surfactant] profile shows a limiting behavior indicative of a unimolecular pathway in the micellar pseudophase.

Biodegradation rates of aromatic contaminants in biofilm reactors

1995 ◽  
Vol 31 (1) ◽  
pp. 117-128 ◽  
Author(s):  
Jean-Pierre Arcangeli ◽  
Erik Arvin
Keyword(s):  
Aromatic Hydrocarbons ◽  
Competitive Inhibition ◽  
Removal Rate ◽  
First Order ◽  
Biofilm Reactors ◽  
First Order Kinetics ◽  
Reducing Conditions ◽  
Low Concentrations ◽  
Degradation Rates ◽  
Order Surface

This study has shown that microorganisms can adapt to degrade mixtures of aromatic pollutants at relatively high rates in the μg/l concentration range. The biodegradation rates of the following compounds were investigated in biofilm systems: aromatic hydrocarbons, phenol, methylphenols, chlorophenols, nitrophenol, chlorobenzenes and aromatic nitrogen-, sulphur- or oxygen-containing heterocyclic compounds (NSO-compounds). Furthermore, a comparison with degradation rates observed for easily degradable organics is also presented. At concentrations below 20-100 μg/l the degradation of the aromatic compounds was typically controlled by first order kinetics. The first-order surface removal rate constants were surprisingly similar, ranging from 2 to 4 m/d. It appears that NSO-compounds inhibit the degradation of aromatic hydrocarbons, even at very low concentrations of NSO-compounds. Under nitrate-reducing conditions, toluene was easily biodegraded. The xylenes and ethylbenzene were degraded cometabolically if toluene was used as a primary carbon source; their removal was influenced by competitive inhibition with toluene. These interaction phenomena are discussed in this paper and a kinetic model taking into account cometabolism and competitive inhibition is proposed.

In-vitro Kinetic Hydrolysis Study of Metronidazole Derivatives with Carvacrol and Eugenol Using Validated RP-HPLC Method

2020 ◽  
Vol 16 ◽  
Author(s):  
M. Alarjah
Keyword(s):  
Half Life ◽  
Hplc Method ◽  
Hydrolysis Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Rp Hplc ◽  
Pharmacokinetic Properties ◽  
Pseudo First Order ◽  
Kinetic Hydrolysis

Background: Prodrugs principle is widely used to improve the pharmacological and pharmacokinetic properties of some active drugs. Much effort was made to develop metronidazole prodrugs to enhance antibacterial activity and or to improve pharmacokinetic properties of the molecule or to lower the adverse effects of metronidazole. Objective: In this work, the pharmacokinetic properties of some of monoterpenes and eugenol pro metronidazole molecules that were developed earlier were evaluated in-vitro. The kinetic hydrolysis rate constants and half-life time estimation of the new metronidazole derivatives were calculated using the validated RP-HPLC method. Method: Chromatographic analysis was done using Zorbbax Eclipse eXtra Dense Bonding (XDB)-C18 column of dimensions (250 mm, 4.6 mm, 5 μm), at ambient column temperature. The mobile phase was a mixture of sodium dihydrogen phosphate buffer of pH 4.5 and methanol in gradient elution, at 1ml/min flow rate. The method was fully validated according to the International Council for Harmonization (ICH) guidelines. The hydrolysis process carried out in an acidic buffer pH 1.2 and in an alkaline buffer pH 7.4 in a thermostatic bath at 37ºC. Results: The results followed pseudo-first-order kinetics. All metronidazole prodrugs were stable in the acidic pH, while they were hydrolysed in the alkaline buffer within a few hours (6-8 hr). The rate constant and half-life values were calculated, and their values were found to be 0.082- 0.117 hr-1 and 5.9- 8.5 hr., respectively. Conclusion: The developed method was accurate, sensitive, and selective for the prodrugs. For most of the prodrugs, the hydrolysis followed pseudo-first-order kinetics; the method might be utilised to conduct an in-vivo study for the metronidazole derivatives with monoterpenes and eugenol.

Decomposition of 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenezenesulfonic Acid) in Solutions ofFD&C Red No. 40

1984 ◽  
Vol 67 (4) ◽  
pp. 844-845
Author(s):  
Naomi Richfield-Fratz
Keyword(s):  
Liquid Chromatography ◽  
Aqueous Solutions ◽  
Borate Buffer ◽  
Sodium Borate ◽  
First Order ◽  
First Order Kinetics ◽  
Color Additive ◽  
Sodium Borate Buffer

Abstract 4,4'-(Diazoamino)-bis(5-methoxy-2-methylbenzenesuIfonic acid), when present as a reaction by-product in FD&C Red No. 40, is shown to decompose rapidly in aqueous solutions of the color additive. The decomposition is halted by the addition of sodium borate buffer. Quantitationly liquid chromatography shows that decomposition is nonlinear with time and follows approximate first order kinetics.

scholarly journals Comparative Study of Chemical Stability of Two H1Antihistaminic Drugs, Terfenadine and ItsIn VivoMetabolite Fexofenadine, Using LC-UV Methods

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Rafał Pietraś ◽  
Izabela Kozak ◽  
Karolina Lejwoda ◽  
...  
Keyword(s):  
Comparative Study ◽  
Chemical Stability ◽  
First Order ◽  
First Order Kinetics ◽  
Kinetics Of Degradation ◽  
Effects Of Temperature ◽  
High Doses ◽  
Antihistaminic Drugs ◽  
Kinetics Of

A comparative study of chemical stability of terfenadine (TER) and itsin vivometabolite fexofenadine (FEX) was performed. Both TER and FEX were subjected to high temperature at different pH and UV/VIS light at different pH and then quantitatively analyzed using new validated LC-UV methods. These methods were used to monitor the degradation processes and to determine the kinetics of degradation for both the compounds. As far as the effects of temperature and pH were concerned, FEX occurred more sensitive to degradation than TER. As far as the effects of UV/VIS light and pH were concerned, the both drugs were similarly sensitive to high doses of light. Using all stress conditions, the processes of degradation of TER and FEX followed the first-order kinetics. The results obtained for these two antihistaminic drugs could be helpful in developing their new derivatives with higher activity and stability at the same time.

The conversion of ethylene to ethylidyne on Pt(111): non-first order kinetics and ensemble effects

1994 ◽  
Vol 301 (1-3) ◽  
pp. 177-196 ◽  
Author(s):  
W. Erley ◽  
Y. Li ◽  
D.P. Land ◽  
John C. Hemminger
Keyword(s):  
First Order ◽  
First Order Kinetics ◽  
Ensemble Effects
Sign in / Sign up

Export Citation Format

Share Document