scholarly journals KINETICS OF POLYMER CARRIER IMPREGNATION BY TRIALKYLAMINE

2019 ◽  
Vol 16 (31) ◽  
pp. 729-737
Author(s):  
I. D TROSHKINA ◽  
J. A OBRUCHNIKOVA ◽  
O. A VESELOVA ◽  
S. M PESTOV
Keyword(s):  
Second Order ◽  
Polymer Carrier ◽  
Rate Limiting Step ◽  
Correlation Degree ◽  
Macroporous Carrier ◽  
Pseudo Second Order ◽  
Volume Method ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Extraction Agent

The immediacy of the problem under study is due to the lack of data on the kinetics of polymer carrier impregnation with extraction agents. The article is aimed at obtaining the kinetic characteristics of the impregnation of a polymeric macroporous carrier—a weakly acidic cation resin with carboxyl groups—with trialkylamine and its solutions in acetone. The integral kinetic curves of the extraction agent adsorption on the carrier were obtained. This allowed estimating the time of equilibrium by the limited solution volume method. This time was 25-30 hours, decreasing with the application of a dilution agent and with the increase in temperature. The kinetic impregnation characteristics were calculated by means of the pseudo-second-order, Elovich, and internal diffusion models. The pseudo-second-order model describes the experimental kinetic data with a high correlation degree (R2 0.995-0.997) and points out that interaction with two sorption centres possibly takes place with the adsorption of a single trialkylamine molecule. The impregnation rate constants via an extraction agent were calculated using all kinetic models. Based on the apparent activation energy magnitude (37±14 kJ/mol), it can be assumed that diffusion is the rate-limiting step of the impregnation process. This article can be useful for creating impregnates containing extraction agents of various classes.

scholarly journals Kinetics and thermodynamics of adsorption of congo red on cellulose

2010 ◽  
Vol 8 (4) ◽  
pp. 906-912 ◽  
Author(s):  
Babak Samiey ◽  
Mohammad Dargahi
Keyword(s):  
Congo Red ◽  
Kinetics Of Adsorption ◽  
First Order ◽  
Rate Limiting Step ◽  
Pseudo Second Order ◽  
Initial Adsorption ◽  
Initial Adsorption Rate ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Cellulose Surface

AbstractThermodynamics and kinetics of adsorption of congo red (CR) on cellulose are studied at 308–328 K. In the used concentration range of CR, interaction of CR with cellulose is exothermic and CR molecules adsorb chemically on cellulose surface. The effects of contact time, temperature and initial concentration of CR on kinetics of its adsorption on cellulose were investigated. The process proceeds according to the pseudo-second-order equation. Initial adsorption rate of adsorption is first-order in CR and the intraparticle diffusion of CR molecules within cellulose is identified as the main rate-limiting step.

scholarly journals ADSORPTION KINETICS OF Pb(II), Cd(II) AND Cr(III) ON ADSORBENT PRODUCED BY PROTECTED-CROSSLINKING OF HUMIC ACID-CHITOSAN

2010 ◽  
Vol 10 (1) ◽  
pp. 80-87
Author(s):  
Dewi Umaningrum ◽  
Uripto Trisno Santoso ◽  
Radna Nurmasari ◽  
Rahmat Yunus
Keyword(s):  
Humic Acid ◽  
Adsorption Kinetics ◽  
Metal Ion ◽  
Second Order ◽  
Adsorption Rate ◽  
Ion Concentration ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Rate Limiting ◽  
Kinetics Of

Study on adsorption kinetics of of Pb(II), Cd(II) and Cr(III) on adsorbent which was produced by protected-crosslinking of humic acid-chitosan has been done. The Langmuir-Hinshelwood, pseudo first- and second-order kinetics models were used to describe the kinetic data, and the rate constants of adsorption were also evaluated. The experimental data fitted well the second-order kinetics model, indicating that the chemical sorption is the rate-limiting step, instead of mass transfer. The initial metal ion concentration significantly affects the adsorption rate. An increase in initial metal ion concentration results in the decrease in adsorption rate of the metals.   Keywords: kinetics, adsorption, crosslinking, humic acid, chitosan

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Kinetics and mechanism of cyclization of N-(2-methoxycarbonylphenyl)-N’-methylsulphonamide to 3-methyl-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide

1991 ◽  
Vol 56 (8) ◽  
pp. 1701-1710 ◽  
Author(s):  
Jaromír Kaválek ◽  
Vladimír Macháček ◽  
Miloš Sedlák ◽  
Vojeslav Štěrba
Keyword(s):  
Potassium Hydroxide ◽  
Acid Catalysis ◽  
Potassium Hydroxide Solution ◽  
Hydroxide Solution ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Cyclization Kinetics ◽  
Rate Limiting ◽  
Kinetics Of

The cyclization kinetics of N-(2-methylcarbonylphenyl)-N’-methylsulfonamide (IIb) into 3-methyl-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide (Ib) has been studied in ethanolamine, morpholine, and butylamine buffers and in potassium hydroxide solution. The cyclization is subject to general base and general acid catalysis. The value of the Bronsted coefficient β is about 0.1, which indicates that splitting off of the proton from negatively charged tetrahedral intermediate represents the rate-limiting and thermodynamically favourable step. In the solutions of potassium hydroxide the cyclization of dianion of the starting ester IIb probably becomes the rate-limiting step.

Removal of Mg from spring water using natural clinoptilolite

Clay Minerals ◽  
2012 ◽  
Vol 47 (1) ◽  
pp. 81-92 ◽  
Author(s):  
S. Tomić ◽  
N. Rajić ◽  
J. Hrenović ◽  
D. Povrenović
Keyword(s):  
Ion Exchange ◽  
Kinetic Studies ◽  
Spring Water ◽  
Zeolite A ◽  
Zeolitic Tuff ◽  
Rate Limiting Step ◽  
Intra Particle Diffusion ◽  
Pseudo Second Order ◽  
Natural Clinoptilolite ◽  
Rate Limiting

AbstractNatural zeolitic tuff from Brus (Serbia) consisting mostly of clinoptilolite (about 90%) has been investigated for the reduction of the Mg concentration in spring water. The sorption capacity of the zeolite is relatively low (about 2.5 mg Mg g-1for the initial concentration of 100 mg Mg dm-3). The zeolitic tuff removes Mg from water solutions by ion exchange, which has been demonstrated by energy dispersive X-ray analysis (EDS). The extent of ion exchange was influenced by the pH and the initial Mg concentration. Kinetic studies revealed that Lagergen's pseudo-second order model was followed. Intra-particle diffusion of Mg2+influenced the ion exchange, but it is not the rate-limiting step. Rather than having to dispose of the Mg-loaded (waste) zeolite, a possible application was tested. Addition to a wastewater with a low concentration of Mg showed that it could successfully make up for the lack of Mg micronutrient and, accordingly, enabled the growth of phosphate-accumulating bacteriaA. Junii, increasing the amount of phosphate removed from the wastewater.

High field 1H NMR Studies of Sol-Gel Kinetics

1986 ◽  
Vol 73 ◽  
Author(s):  
Bruce D. Kay ◽  
Roger A. Assink
Keyword(s):  
Equilibrium Distribution ◽  
Sol Gel ◽  
Nmr Studies ◽  
H Nmr ◽  
Rate Limiting Step ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Product Species ◽  
Rate Limiting ◽  
Kinetics Of

ABSTRACTHigh resolution 1H NMR spectroscopy at high magnetic fields is employed to study the reaction kinetics of the Si(OCH3)4:CH3OH:H2O sol-gel system. Both the overall extent of reaction as a function of time and the equilibrium distribution of species are measured. In acid catalyzed solution, condensation is the rate limiting step while in base catalyzed solution, hydrolysis becomes rate limiting. A kinetic model in which the rate of hydrolysis is assumed to be independent of the adjacent functional groups is presented. This model correctly predicts the distribution of product species during the initial stages of the sol-gel reaction.

scholarly journals Exploitation of the IDO Pathway in the Therapy of Rheumatoid Arthritis

2013 ◽  
Vol 6s1 ◽  
pp. IJTR.S11737 ◽  
Author(s):  
Richard O. Williams
Keyword(s):  
Rheumatoid Arthritis ◽  
Anthranilic Acid ◽  
Kynurenine Pathway ◽  
Gene Encoding ◽  
Rate Limiting Step ◽  
Tryptophan Metabolites ◽  
Synthetic Derivative ◽  
Rate Limiting ◽  
Kinetics Of ◽  
Draining Lymph Nodes

Indoleamine 2,3-dioxygenase (IDO) is the first and rate-limiting step along the kynurenine pathway and is thought to play a key role in immune homeostasis through depletion of tryptophan and accumulation of kynurenines. In this review we summarize recent research into the possibility of harnessing the IDO pathway for the therapy of rheumatoid arthritis. Inhibition of IDO activity, or knockout of the gene encoding IDO, was shown to cause an increase in the severity of collagen-induced arthritis, an animal model of rheumatoid arthritis. The increased severity of disease was associated with elevated numbers of pathogenic Th1 and Th17 cells in the joints and draining lymph nodes. In another study, analysis of the kinetics of expression of downstream kynurenine pathway enzymes during the course of arthritis revealed a potential role for tryptophan metabolites in resolution of arthritis. Furthermore, the therapeutic administration of L-kynurenine or [3,4-dimethoxycinnamonyl]-anthranilic acid (a synthetic derivative of 3-hydroxy-anthranilic acid) significantly reduced both clinical and histological progression of experimental arthritis. These findings raise the possibility of exploiting the IDO pathway for the therapy of autoimmune disease.

Sign in / Sign up

Export Citation Format

Share Document