Colloidal Dispersion Systems—Physicochemical Properties

These characteristics will be described here. The size of particles may be considered from the following data  

A colloidal suspension may be unstable and exhibit separation of particles within a very short time. Or it may be stable for a very long time, such as over a year or more. And there will thus be found a metastable state, which would be in between these two. This is an oversimplified example, but it shows that one should proceed to analyze any colloidal system following these three criteria. In fact, the most remarkable finding one can mention about colloidal suspensions is that these systems can exist at all Especially, one finds that some solid suspensions can be stable for a very long time. In pharmaceutical applications, one important example is the use of suspension of insulin in pen injections. The insulin suspension is stable for long enough time for its application, which provides very accurate dosage to the patient. In fact, there exists a wide variety of pharmaceutical products that are based on suspended molecules. Nanoparticles have been applied in various pharmaceutical treatments (Sotiriou et al., 2014). 

FIGURE 1.51 Stability criteria of any colloidal system metastable-unstable-stable states. 

As an example, one may consider the wastewater treatment process (Cherimisinofif, 2002). The wastewater with colloidal particles is found to be a stable suspension. However, by treating it with some definite methods (such as pH control, electrolyte concentration, etc.), one can change the stability of the system. 

The wastewater treatment technology is one of the most important areas of surface chemistry applications. Suspended materials are separated by coagulation and filtered away. Soluble pollutants are removed by other procedures. 

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Use of Ultrasonic Vibration Potential To Monitor Coalescence. The complex chemical nature of crude oils makes it difficult to relate the dispersion behavior to the physicochemical properties at the crude-oil-water interface. In addition, the nonpolar and nontransparent nature of the oleic phase provides significant obstacles for studies of the interactions of the suspended water droplets in real systems. Recent development (28, 29) of electroacoustical techniques has shown considerable promise for electrokinetic measurements of colloidal systems and the direct monitoring of the rate and extent of coagulation (flocculation and coalescence) of water droplets in nontransparent water-in-oil media. The electroacoustic measurement for colloidal systems in nonpolar media is based on the ultrasound vibration potential (UVP) mode, which involves the applica-... 

As discussed in Chapters 1-7, diffusion, Brownian motion, sedimentation, electrophoresis, osmosis, rheology, mechanics, interfacial energetics, and optical and electrical properties are among the general physical properties and phenomena that are primarily important in colloidal systems [1-5]. Chemical reactivity and adsorption often play important, if not dominant, roles. Any physicochemical feature may ultimately govern a specific industrial process and determine final product characteristics, and any colloidal dispersions involved may be deemed either desirable or undesirable based on their unique physicochemical properties. Chapters 9-16 will provide some examples. 

This is a method to obtain colloidal drug delivery systems from preformed, well-defined macromolecular materials with known physicochemical and biological properties. Biodegradable nanoparticles from PLA, PLG, PLGA, and poly(E-caprolactone) have been prepared by dispersing the polymers (Vauthier et al. 1991 Couvreur et al. 1995). 

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