PNIPAM-based heteroarm star-graft quarterpolymers: synthesis, characterization and pH-dependent thermoresponsiveness in aqueous media

2015 ◽  
Vol 6 (21) ◽  
pp. 3942-3955 ◽  
Author(s):  
Zacharoula Iatridi ◽  
M. M. Soledad Lencina ◽  
Constantinos Tsitsilianis
Keyword(s):  
Ionic Strength ◽  
Aqueous Media ◽  
Grafting Density ◽  
Ph Dependent

We report the design of PSn(P2VP-b-PAA-g-PNIPAM)n heteroarm star-graft quarterpolymers, the thermoresponsiveness of which is strongly dependent on pH ionic strength, and their macromolecular features, e.g. arm number and grafting density.

Formation and nucleophilic capture of N-nitrosiminium ions

1999 ◽  
Vol 77 (5-6) ◽  
pp. 1148-1161 ◽  
Author(s):  
Latifa Chahoua ◽  
Alain Vigroux ◽  
Yvonne Chiang ◽  
James C Fishbein
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Aqueous Media ◽  
Laser Flash ◽  
Azide Ion ◽  
Iminium Ions ◽  
Nucleophilic Trapping

A study of the solvolysis of a series of (N-nitrosomethylamino)arylmethyl esters and azides and the products of nucleophilic trapping of the corresponding N-nitrosiminium ion intermediates in aqueous media, 25°C, ionic strength 1 M is reported. Structure-reactivity data for the forward and reverse reactions have been obtained. In three cases, the rate constants for reactions of the cations with nucleophiles have been measured directly by laser flash photolysis. The data allow a comparison of the degree to which the N-methyl-N-nitroso functionality enhances cation stability from a thermodynamic and kinetic perspective. It has been possible to deduce that the carbon basicity of azide ion is less than 1 kcal/mol greater than that of acetate ion.Key words: nitrosiminium ions, α-acetoxynitrosamines, carbocations, iminium ions, nucleophilicity.

Why is the hydrolytic activity of acetylcholinesterase pH dependent? Kinetic study of acetylcholine and acetylthiocholine hydrolysis catalyzed by acetylcholinesterase from electric eel

2018 ◽  
Vol 73 (9-10) ◽  
pp. 345-351 ◽  
Author(s):  
Alena Komersová ◽  
Markéta Kovářová ◽  
Karel Komers ◽  
Václav Lochař ◽  
Alexander Čegan
Keyword(s):  
Catalytic Activity ◽  
Ionic Strength ◽  
Ph Value ◽  
Hydrolytic Activity ◽  
Initial Substrate ◽  
Electric Eel ◽  
Value Range ◽  
Ph Dependent ◽  
Ph Range ◽  
Initial Substrate Concentration

AbstractThe dependence of the activity of acetylcholinesterase from electric eel at a pH value range of 4.8–9.8 (phosphate buffer), regarding acetylcholine and acetylthiocholine hydrolysis, was determined at 25 °C, ionic strength of 0.11 M, and initial substrate concentration of 4 mM. At a pH range of 4.8–9.8, the dependencesA(pH) form a sigmoid increasing curve with the maximum catalytic activity at a pH range 8–9.5. For acetylcholine hydrolysis, the kinetic reason for such an increase inAconsists mainly of an increase in the rate constantk2(Michaelis-Menten) model with increasing pH of the reaction mixture. For acetylthiocholine hydrolysis, the kinetic explication of the determined dependenceA(pH) is more complicated.

Adsorption of Phenol on Natural Sediment from Liaohe River, China

2011 ◽  
Vol 356-360 ◽  
pp. 252-258
Author(s):  
Ying Zhang ◽  
Jian Xu ◽  
Yuan Zhang ◽  
Lei Li ◽  
Jiang Ying Zhang
Keyword(s):  
Ionic Strength ◽  
River Sediment ◽  
Adsorption Process ◽  
Adsorption Equilibrium ◽  
Intraparticle Diffusion ◽  
Natural Sediment ◽  
Phenol Adsorption ◽  
Intraparticle Diffusion Model ◽  
Liaohe River ◽  
Ph Dependent

In this study, the adsorption behavior of phenol onto natural sediments from Liaohe River was studied. The effect of pH, temperature, ionic strength, and surfactants on the adsorption process was also investigated. Results showed that it took 48 h for the phenol to achieve adsorption equilibrium on sediment. Kinetic analysis indicated that the process fit well with the intraparticle diffusion model. The phenol adsorption process was pH dependent with the maximum adsorption at pH 4.58. With respect to the Freundlich and Langmuir models, the DR isotherm can describe the adsorption process better. Thermodynamic parameters revealed that phenol adsorption was physisorption. The coexistent salt and surfactants at relatively higher concentrations inhibited the phenol adsorption on Liaohe River sediment.

scholarly journals Marble Waste Sludges as Effective Nanomaterials for Cu (II) Adsorption in Aqueous Media

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2305
Author(s):  
Ventura Castillo Ramos ◽  
José Rivera Utrilla ◽  
Antonio Ruiz Sánchez ◽  
María Victoria López Ramón ◽  
Manuel Sánchez Polo
Keyword(s):  
Ionic Strength ◽  
Aqueous Medium ◽  
Aqueous Media ◽  
Real Life ◽  
Intraparticle Diffusion ◽  
Surface Complexes ◽  
X Ray ◽  
Adsorption Sites ◽  
Life Conditions ◽  
Marble Waste

This study evaluated the waste generated by a Spanish marble-producing company as adsorbent for the removal of copper (Cu [II]) from aqueous media. Six marble waste sludge samples were studied, and the following operational parameters were analyzed in discontinuous regime, including pollutant concentration, pH, temperature, nature of aqueous medium, and ionic strength. The applicability of the adsorbent material was assessed with experiments in both continuous and discontinuous regimes under close-to-real-life conditions. A pseudo-second order model yielded a better fit to the kinetic data. Application of the intraparticle diffusion model revealed two well-differentiated adsorption stages, in which the external material transfer is negligible and intraparticle diffusion is the controlling stage. The equilibrium study was better fitted to a Freundlich-type isotherm, predicting elevated maximum adsorption values (22.7 mg g−1) at a relatively low initial Cu (II) concentration (25 ppm), yielding a highly favorable chemisorption process (n >> 1). X-ray fluorescence study identified calcite (CaCO3) as the main component of marble waste sludges. According to X-ray diffraction analysis, Cu (II) ion adsorption occurred by intercalation of the metallic cation between CaCO3 layers and by the formation of surface complexes such as CaCO3 and Cu2(CO3)(OH)2. Cu (II) was more effectively removed at medium pH, lower temperature, and lower ionic strength of the aqueous medium. The salinity and dissolved organic matter in surface, ground-, and waste-waters negatively affected the Cu (II) removal process in both continuous and discontinuous regimes by competing for active adsorption sites. These findings demonstrate the applicability and effectiveness of marble-derived waste sludges as low-cost and readily available adsorbents for the treatment of waters polluted by Cu (II) under close-to-real-life conditions.

pH dependent Cu(II) and Pd(II) ions detection and removal from aqueous media by an efficient mesoporous adsorbent

2014 ◽  
Vol 236 ◽  
pp. 100-109 ◽  
Author(s):  
Md. Rabiul Awual ◽  
Ismail M.M. Rahman ◽  
Tsuyoshi Yaita ◽  
Md. Abdul Khaleque ◽  
M. Ferdows
Keyword(s):  
Aqueous Media ◽  
Mesoporous Adsorbent ◽  
Ph Dependent

The aggregation behavior of cellulose micro/nanoparticles in aqueous media

RSC Advances ◽  
2015 ◽  
Vol 5 (12) ◽  
pp. 8770-8777 ◽  
Author(s):  
Wenhui Qi ◽  
Hua-Neng Xu ◽  
Lianfu Zhang
Keyword(s):  
Ionic Strength ◽  
Microcrystalline Cellulose ◽  
Aqueous Media ◽  
Aggregation Behavior

Cellulose micro/nanoparticles were obtained from cotton microcrystalline cellulose. The effect of ionic strength on the aggregation behavior of the cellulose micro/nanoparticles in aqueous media has been investigated by means of rheo-SALS.

Dual Effects of Ionic Strength on Klebsiella aerogenes Urease: pH-Dependent Activation and Inhibition

2001 ◽  
Vol 394 (2) ◽  
pp. 280-282 ◽  
Author(s):  
Scott Mulrooney ◽  
Tatiana Zakharian ◽  
Ruth A. Schaller ◽  
Robert P. Hausinger
Keyword(s):  
Ionic Strength ◽  
Klebsiella Aerogenes ◽  
Ph Dependent

scholarly journals Ionic strength and pH dependent multi-site sorption of Cs onto a micaceous aquifer sediment

2014 ◽  
Vol 40 ◽  
pp. 32-42 ◽  
Author(s):  
Adam J. Fuller ◽  
Samuel Shaw ◽  
Caroline L. Peacock ◽  
Divyesh Trivedi ◽  
Joe S. Small ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Ph Dependent
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