Presence Of Composite Particles Research Articles

True flotation versus entrainment in reverse cationic flotation for the concentration of iron ore at industrial scale

ABSTRACTThe loss of iron-bearing minerals to the tailings, especially in the finest fractions (−44 μm), is a problem that must be endured due to the depletion of deposits containing high-Fe hematite. The two main mechanisms for iron mineral loss in the froth in reverse cationic flotation are hydrodynamic dragging and true flotation. This last one being attributed to failures in the conditioning processes regarding the depression of iron mineral by starch. In this work, two industrial mechanical flotation circuits located in Minas Gerais—Brazil, namely Conceição Itabiritos II and Pico, operating with mineralogically distinct iron minerals, had their tailings analyzed in order to attribute reasons for the iron-bearing minerals losses. Liberation studies excluded losses due to the presence of composite particles where hematite was combined to silica or goethite. The method known as two-liquid flotation was applied to the several particle fractions present in the tailings to evaluate the particles surfaces hydrophobicity/hydrophilicity. The results indicated that for Conceição Itabiritos II, the loss of iron minerals was due to a combination of true flotation and hydrodynamic dragging. True flotation probably took place because of depression failure. For Pico, the results revealed that most of the iron-bearing particles were lost due to hydrodynamic dragging. The shape factor and terminal velocity, both obtained via permeametry, confirmed the two-liquid flotation results. Two-liquid flotation was shown to be a fast and simple method to qualitatively assess the hydrophobicity of particles in froth flotation, thus allowing quick improvements in the process.

An analysis of the factors contributing to the settling potential of fine fluvial sediment

AbstractThe settling potential of fine sediment is known to be influenced by particle size, shape, density and porosity, and is commonly predicted using Stokes's law, despite its known limitations for modelling the behaviour of natural particles. In order to develop an improved understanding of the potential for fine sediment to settle out of suspension or undergo transport by hydraulic processes, it is important to examine the role of particle structure in detail. In this study, stepwise regression was used to identify which structural properties of particles exert an important control on fine sediment behaviour in river systems. The presence of composite particles and their associated particle size, porosity and fractal dimension were shown to be the most important controls on settling potential. Composite particles that form in the aquatic environment (flocs) were shown to have significantly different form and behaviour from composite particles of terrestrial origin (aggregates). Importantly, it was demonstrated that particle structure and behaviour exhibited consistencies between contrasting river catchments in different locations. An understanding of the mechanisms responsible for the formation of composite particles is viewed as providing a valuable input to efforts to model the mobilisation, transport and fate of fine sediment. Copyright © 2008 John Wiley & Sons, Ltd.

Electrodeposited composite coatings of copper with inert, semiconductive and conductive particles

Data for the codeposition of some types of inert, semiconductive and conductive particles with copper in the electroplating are presented. It is shown that current density and particle concentration in the plating bath strongly affect the particle content in the composites produced. The nature of the particles also has a great influence on the amount of particles entrapped in composites. The presence of particles in composites changes their characteristics, making them better or worse with respect to tensile strength, hardness or surface texture. The particle distribution in electrodeposited composites is uniform across and over the coating.