Adhesion in Beneficiation Processes

Triboadhesive enrichment or beneficiation can be used successfully in two types of applications size classification of powdered materials and the separation of mineral particles from impurities. In the first category we may mention the classification of powders such as quartz, barite, magnetite, hematite, pyrite, feldspar, coal, asbestos, graphite, periclase (crystalline magnesium oxide), pegmatite, and iron ore. As an illustration of an application in the second category we may mention the separation of asbestos fiber ( falling product) from mineral dust that adheres to the drum surface ( retained product) [327]. 

As demonstrated by these examples, the triboadhesive method of enrichment or beneficiation is based on differences in adhesivity of particles due to differences in size or shape. 

Let us now examine changes in mineral adhesion that are related to the choice of drum material [137]. For the separation of powders such as quartz, magnetite, hematite, pyrite, barite, asbestos, and j3-spodumene, the yield of the retained fraction on brass and aluminum surfaces was found to vary from 26 to 50%, and on tin plate and steel from 46 to 66%. The adhesion of these powders to tin plate and steel was greater than the adhesion to brass or aluminum. 

The yields of retained fraction for coal and coal constituents, depending on the drum material, were found to be as follows [137]  

Yield (in %) of retained fraction with indicated drum material brass. 

---

The important beneficial effects that substrate roughness can bring were firmly established in the late sixties and early seventies, principally as a result of work in two areas. The first was associated with the electroless deposition of metals onto plastics such as ABS and polypropylene. In the process the plastics must be etched in a way which produces pits on a micrometre scale. Such a topography had been shown to be a necessary, but not sufficient condition for adequate adhesion [40]. 

Substitution of the side chain with fluorine was shown to be beneficial in improving sensitivity and FBM, polyhexafluorobutyl methacrylate and EBR-9, polytrifluoroethyl a-chloromethacrylate are produced commercially with sensitivities of 1-5 xCcm . Unfortunately most PMMA analogues sacrifice some other property to achieve such sensitivities, e.g. FBM has poor adhesion and its process latitude is small. 

We attempt to extend the Hard-Soft Acid-Base (HSAB) principle for the reactions in solutions to interactions in solids. First we point out the important link between the absolute hardness of acid-and-base and the average energy gap. Then we discuss the electronic band structures of various solids, e.g., metals, semimetals, semiconductors and insulators. On the basis of energy gaps, we elaborate various consequences of the acid-base interactions in solids. The applications of HSAB principle and the frontier orbital concept to the solid adhesion and surface interactions between metals and polymers will be verified by experimental results reported in the literature. The new findings reported in this paper should be beneficial to those who are carrying out research in or processing thin-film microelectronic devices or thick-film multilayer structures. 

The formation of ordered two- and three-dimensional microstructuies in dispersions and in liquid systems has an influence on a broad range of products and processes. For example, microcapsules, vesicles, and liposomes can be used for controlled drug dehvery, for the contaimnent of inks and adhesives, and for the isolation of toxic wastes. In addition, surfactants continue to be important for enhanced oil recovery, ore beneficiation, and lubrication. Ceramic processing and sol-gel techniques for the fabrication of amorphous or ordered materials with special properties involve a rich variety of colloidal phenomena, ranging from the production of monodispersed particles with controlled surface chemistry to the thermodynamics and dynamics of formation of aggregates and microciystallites. 

Volume therapy with etherified starches in trauma patients results in a reduction in circulating adhesion molecules, an effect that is not observed with albumin infusion (51). Continuous infusion of pentoxifylline did not have a beneficial modulating action on circulating adhesion molecules. Adhesion molecules appear to play an important role in tissue damage secondary to the inflammatory process. Besides neutrophil- and endothelium-bound adhesion molecules, soluble forms have been detected in the circulating blood in trauma patients. They seem to be markers of endothelial damage, but they may also have other biological functions. 

---