Bubble surface, molecular contaminants

At microflotation the process of deposition of disperse particles and molecular contaminants on a bubble surface proceed in parallel. If the rates of these processes are commensurable in the process of microflotation the level of impurities in the bulk decreases. It means that their adsorption on bubbles surfaces decreases too, leading to the increase of the residual mobility. 

Note, that the bubble surface can be covered by an adsorption layer even without the special addition of surfactant due to contaminations in natural, tap, and industrial waters. Thus, the conclusion that wetting films are stable due to the stabilising effect of molecular forces is at least doubtful for natural waters containing traces of surface active compounds which can destabilise the wetting film and can provide contactless flotation. Collectorless microflotation has been observed for example by Goldman et al. (1974). However, they did not perform any colloid-chemical investigations. 

Let us point out two more aspects of this problem, which contribute to the preservation of a noticeable mobility of the bubble surface. It is expected that in the development of microflotation technology, increasingly deeper purification from dispersed particles and therefore from molecular contaminations can be attained under the condition of a remarkable residual mobility. 

The nature of the electrochemical reactions in a cell, especially with d.c. drive, depends amongst other factors on the molecular constitution of the nematic substances, on impurities in the liquid crystal and on the conductivity and orientation additives [84]. Even the electrodes and substrates, their contamination and the drive voltage and its duty cycle can also affect these reactions. The primary failure mechanisms are breakdown of the surface alignment, formation of bubbles, discoloration of the liquid crystal layer or a narrowing of the liquid crystalline temperature range. 

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