Floating aggregate

Multinuclear NMR spectroscopy experiments of various 1,3-dialkylimidazolium ILs dissolved in organic solvents have also pointed to the formation of floating aggregates through hydrogen bonds [81-84]. In particular, it has been demonstrated by heteronuclear NMR experiments on [C4CjIm]BF4 that contact ion pairs exist in the presence of small amounts of water and even in dimethyl sulfoxide (DMSO) solution [85]. 

The term flotoflocculation is used to describe the process of aggregating dispersed oil droplets by the aid of polymeric flocculants (flocculation) then subjecting them to conventional flotation. It is also used, genericaHy, to describe situations where particles are first aggregated then floated. 

In a DAF thickening process, air is added at pressures in excess of atmospheric pressure (2.1 to 4.9 kg/cm1 2 3 4 30 to 70psig) either to the incoming sludge stream or to a separate liquid stream. When the pressure is reduced and turbulence is created, air in excess of that required for saturation at atmospheric pressure leaves the solution as very small bubbles of 50 to 100 pm in diameter. The bubbles adhere to the suspended particles or become enmeshed in the solids matrix. As the average density of the solids-air aggregate is less than that of water, the agglomerate floats to the surface. The floated solids build to a depth of several inches at the water surface. Skimmers continuously remove the float.58... 

Flotation temperature was the subject of numerous studies. It was concluded that heating the pulp with collector is the only way to selectively float bastnaesite. Heating the pulp with collector is believed to result in selective aggregation of bastnaesite in the form of repellent droplets, which may result in improved selectivity and in a reduction in slime interference. 

Foam - A fluid aggregate of air filled bubbles, formed by chemical means that will float on the surface of flammable liquids or flow over solid surfaces. The foam functions to blanket and extinguish fires and/or prevent the ignition of the material. 

The problems causing the observed instability of colloids stems from the interface separating the two phases. In French dressing, for example, each oil particle is surrounded with water. The instability of the water-air interface causes the system to minimize the overall area of contact between the two phases, which is most readily achieved by the colloid particles aggregating and thereby forming two distinct phases, i.e. oil floating on water. 

Note When precipitation occurs in sol-gel processing, sol particles have aggregated to a size where gravitational forces cause them to sink or float. Generally, aggregation arises from a change in the sol that reduces the interparticle repulsion. 

Matsuda, Akutsu, et al. [141] carried out chemical fixation of GRGDSP onto a poly(vinyl alcohol) film which had been activated by carbonyl diimidazol in dimethylformamide. For comparison, fibronectin was also immobilized on a poly(vinyl alcohol) film by the same technique. Matsuda et al. found that bovine endothelial cells (ECs) adhered well to the peptide- and fibronectin-immobilized film furthermore, after a three-day incubation, aggregated ECs floated on nontreated PVA film, while the peptide-immobilized surface greatly enhanced cell spreading and growth, which surpassed that on fibronectin-bound PVA. 

Fig. 39 Aggregation of colloids coated with long DNA strands above a sticky surface leads to flying carpets, floating 2D crystals, (a) Confocal microscopy image of a flying carpet (scale bar is 10 pm), (b) Pair correlation function of the structure depicted in (a). The observed peaks match those expected for a perfect hexagonal crystal (black triangles). Reproduced with permission from [165]...

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