Membrane technology offers other new techniques for combining reaction and separation activities when the product molecules are smaller than the reactant molecules. Removal of
product also makes membrane reactors advantageous if the product can react with a reactant to form a waste. Membranes are important in modern separation processes, because they work on continuous flows, are easily automated, and can be adapted to work on several physical parameters, such as molecular size, ionic character of compounds, polarity, and hydrophilic/ hydrophobic character of components.
Microfiltration, ultrafiltration, and reverse osmosis differ mainly in the size of the molecules and particles that can be separated by the membrane (Table 6). Liquid membrane technology offers a novel membrane separation method in that separation is affected by the solubility of the component to separate into a liquid membrane rather than by its permeation through pores, as is the case in conventional membrane processes, such as ultrafiltration and reverse osmosis. The component to be separated is extracted from the continuous phase to the surface of the liquid membrane, through which it diffuses into the interior liquid phase. Promising results have been reported for a variety of applications, and it is claimed to offer distinct advantages over alternative methods, but liquid membrane extraction is not yet widely available.
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