Stability of Colloidal Dispersions: A Thermodynamic Approach

1993 ◽  
Vol 27 (10) ◽  
pp. 117-129 ◽  
Author(s):  
Raj Rajagopalan
Keyword(s):  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Colloidal Dispersions ◽  
Chemical Parameters ◽  
Interaction Forces ◽  
Colloidal Forces ◽  
Stability Diagrams ◽  
The Stability ◽  
Physical And Chemical ◽  
Interparticle Collisions

The classical theory of coagulation relies on relating the rate of interparticle collisions to the interaction forces, and thus to the physical and chemical parameters of the dispersion, through kinetic arguments, and is restricted to dilute systems. Here, we present a modern, thermodynamic theory capable of predicting stability diagrams for dense as well as dilute dispersions. Although based on statistical thermodynamics, the method is simple to use and requires only the second virial coefficient of osmotic pressure of the dispersion. All the information necessary for applying the model to arbitrary dispersions is given. The method is illustrated for a model colloidal potential, and it is shown how static light scattering measurements can be used for predicting the stability diagrams when information about the colloidal forces are not known in advance.

Intermolecular forces in gaseous ammonia and in ammonia – nonpolar gas mixtures

1970 ◽  
Vol 48 (19) ◽  
pp. 2993-3001 ◽  
Author(s):  
C. S. Lee ◽  
J. P. O'Connell ◽  
C. D. Myrat ◽  
J. M. Prausnitz
Keyword(s):  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Entropy Change ◽  
Intermolecular Forces ◽  
Intermolecular Potential ◽  
Gaseous Ammonia ◽  
Viscosity Data ◽  
Vibrational Entropy ◽  
Ammonia Transport ◽  
Physical And Chemical

Intermolecular potential parameters for ammonia have been determined for the Stockmayer–Kihara function using experimental second virial coefficient, diffusivity and viscosity data of binary mixtures with argon, methane, nitrogen, and oxygen. The parameters U0/k = 215 °K, σ(core-to-core) = 2.70 Å and a* = 0.2 reproduce essentially all of the data nearly within experimental error and accurately reproduce pure ammonia transport properties. Upon considering both physical and chemical contributions to the second virial coefficient of ammonia, the apparent standard-state hydrogen-bond enthalpy for chemical dimerization is −3.2 kcal/mole while the vibrational entropy change is 20.2 cal/mole °K, indicating weak association.

scholarly journals Stability assessment of Lanette Lotion of a magistral pharmacy in the region of Curitiba

2020 ◽  
Vol 13 (5) ◽  
pp. 69
Author(s):  
A. C. Santos ◽  
B. K. Souza ◽  
A. F. T. Souza ◽  
N. C. Lubi ◽  
T. F. B. X. Silva
Keyword(s):  
Room Temperature ◽  
Heterogeneous Systems ◽  
Slight Modification ◽  
Stability Study ◽  
Chemical Parameters ◽  
Product Quality Control ◽  
Organoleptic Characteristics ◽  
Accelerated Stability ◽  
The Stability ◽  
Physical And Chemical

Emulsions are heterogeneous systems, thermodynamically unstable, formed by the combination of hydrophilic and lipophilic substances through agents of surface tension. The product quality control is handled as the most important to study the stability of the final product which determines the length of time that can be considered stable, that means, able to keep up with the same characteristics which have been developed. The study aimed to evaluate the physical and chemical parameters, by determining the pH, viscosity and organoleptic characteristics (color, odor and appearance) of the lotion Lanette used in a magistral pharmacy in Curitiba. The formulation commonly used in the pharmacy was stored at temperatures of 4 ° C ambient and 45 ° C over a period of 90 days which was divided into 6 times to carry out aspects of analysis. In the preliminary stability study there was no change, but in the accelerated there was a slight modification in appearance, this change was more intense in the formulation conditioned at room temperature and 4 ° C. The pH has had a significant change at all temperatures. Concluding that against accelerated stability tests Lanette lotion, even with the changes, showed good stability.

The influence of gelatin and starter culture on the physical and chemical parameters of cheeses with different fat content

2018 ◽  
Vol 6 (10) ◽  
pp. 123-130
Author(s):  
Yaroslava Zhukova ◽  
◽  
Pylyp Petrov ◽  
Olena Boloba ◽  
Tetiana Ohrimenko ◽  
...  
Keyword(s):  
Starter Culture ◽  
Fat Content ◽  
Chemical Parameters ◽  
Physical And Chemical Parameters ◽  
Physical And Chemical

Life in Glacial and Alpine Rivers in Central Iceland in Relation to Physical and Chemical Parameters

2000 ◽  
Vol 31 (4-5) ◽  
pp. 411-422 ◽  
Author(s):  
Gísli Már Gíslason ◽  
Jón S. Ólafsson ◽  
Hákon Adalsteinsson
Keyword(s):  
Chemical Properties ◽  
Chemical Parameters ◽  
Invertebrate Fauna ◽  
Glacial Meltwater ◽  
Biological Communities ◽  
Relative Contribution ◽  
Glacial River ◽  
Alpine Rivers ◽  
Physical And Chemical ◽  
And Chemical Properties

The characteristics of stream and river ecosystems in arctic and alpine areas are determined mainly by the relative contribution of glacial meltwater, snowmelt, rainfall and groundwater. Each source generates a particular seasonal hydrological signature, affecting physical and chemical properties, and hence biological communities. The relative contribution of each source is sensitive to climate change. The study was concentrated on the glacial River W-Jökulsá and some non-glacial rivers in the central highlands of Iceland. The water in the glacial river was entirely glacial meltwater at the glacier margin, but the glacial contribution was about 20% 40 km downstream. However, its tributaries and non-glacial reference rivers were mainly springfed. The invertebrate fauna was confined to Chironomidae of the genus Diamesa close to the glacier, but other taxa (species and groups of species) occupied the river further downstream, where their diversity was close to that found in the reference rivers.

Interpretation of Preferential Adsorption Using Random Phase Approximation Theory

1995 ◽  
Vol 60 (10) ◽  
pp. 1641-1652 ◽  
Author(s):  
Henri C. Benoît ◽  
Claude Strazielle
Keyword(s):  
Approximation Theory ◽  
Random Phase Approximation ◽  
Virial Coefficient ◽  
Random Phase ◽  
Second Virial Coefficient ◽  
Solvent Mixture ◽  
Gyration Radius ◽  
Thermodynamic Quantities ◽  
Phase Approximation ◽  
Preferential Adsorption

It has been shown that in light scattering experiments with polymers replacement of a solvent by a solvent mixture causes problems due to preferential adsorption of one of the solvents. The present paper extends this theory to be applicable to any angle of observation and any concentration by using the random phase approximation theory proposed by de Gennes. The corresponding formulas provide expressions for molecular weight, gyration radius, and the second virial coefficient, which enables measurements of these quantities provided enough information on molecular and thermodynamic quantities is available.

scholarly journals Ultrafiltration Process in Disinfection and Advanced Treatment of Tertiary Treated Wastewater

Membranes ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 221
Author(s):  
Rafał Tytus Bray ◽  
Katarzyna Jankowska ◽  
Eliza Kulbat ◽  
Aneta Łuczkiewicz ◽  
Aleksandra Sokołowska
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Microscopic Analysis ◽  
Fecal Coliforms ◽  
Treated Wastewater ◽  
Chemical Parameters ◽  
Virus Particles ◽  
E Coli ◽  
The One ◽  
Physical And Chemical

The paper presents the results of research on the use of ultrafiltration, using membranes of 200 and 400 kDa separation, for disinfection of municipal treated wastewater. The research was conducted on a fractional technical scale using real municipal treated wastewater from two large wastewater treatment plants treating most of the wastewater over the one-million polycentric Gdańsk agglomeration (1.2 million inhabitants). UF 200 kDa and UF 400 kDa processes enabled further improvement of the physical and chemical parameters of treated wastewater. Total phosphorus (to below 0.2 mg/L–UF 200 kDa, 0.13 mg/L–UF 400 kDa) and turbid substances (to below 0.2 mg/L, both membranes) were removed in the highest degree. COD was reduced efficiently (to below 25.6 mgO2/L–UF 200 kDa, 26.8 mgO2/L–UF 400 kDa), while total nitrogen was removed to a small extent (to 7.12 mg/L–UF 200 kDa and 5.7 mg/L–UF 400 kDa. Based on the reduction of indicator bacteria; fecal coliforms including E. coli (FC) and fecal enterococci (FE) it was found that the ultrafiltration is an effective method of disinfection. Not much indicator bacterial were observed in the permeate after processes (UF 200 kDa; FC—5 CFU/L; FE—1 CFU/L and UF 400 kDa; FC—70 CFU/L; FE—10 CFU/L. However, microscopic analysis of prokaryotic cells and virus particles showed their presence after the application of both membrane types; TCN 3.0 × 102 cells/mL–UF 200 kDa, 5.0 × 103 cells/mL–UF 400 kDa, VP 1.0 × 105/mL. The presence of potentially pathogenic, highly infectious virus particles means that ultrafiltration cannot be considered a sufficient disinfection method for treated wastewater diverted for reuse or discharged from high load wastewater treatment plants to recreational areas. For full microbiological safety it would be advisable to apply an additional disinfection method (e.g., ozonation).

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