Current pressure-driven

Air-pressure-driven active devices. Air-pressure-driven aerosolization is the concept employed in a number of devices currently in different stages of development with drugs for local or systemic action. These devices rely on a small patient-operated air pump. Air is compressed by mechanical means (piston or bellows) and is released on the external trigger given by the patient s inspiratory cycle. Because of the use of this air pump, these devices have an active aerosolization mechanism and are assumed to be less flow-rate-dependent than passive DPI devices. 

Separation of isopropanol (IPA) and water by pervaporation has also reached production scale. Much of the current capacity is devoted to azeotrope breaking and dehydration during IPA synthesis. Recently, anhydrous isopropanol has become a preferred drying solvent in the semiconductor industry, where chip wafers are first washed with ultrapure water, then rinsed with the alcohol to promote uniform drying. The water-laden isopropanol generated can be conveniently reused after dehydration by pervaporation. Unlike with pressure-driven membrane processes such as RO or UF, particulates and nonvolatile substances such as salts are not carried over during pervaporation. This helps maintain the effectiveness of contamination control. 

Two injection techniques currently in use are hydrodynamic injection and electrokinetic injection. Hydrodynamic injection is pressure driven, and therefore all components in the sample are injected simultaneously. In contrast, with electrokinetic injection, the entry of the components of the sample into the column depends on ion mobility, charge, and concentration. 

Advancement in Pressure-Driven Processes and Current World Scenario... 

Since the electrical resistance of the effiuent and parasitic currents are minimal at high level of impurities, specihc interest in electrically assisted membrane processes could increase due to more strict laws and legislation around effluents. The depletion of freshwater resources and the necessity to process brackish or seawater to produce potable water could promote the use of electrically assisted membrane processes in the future. Electrodialysis will have to compete with pressure-driven membrane processes such as reverse osmosis. The growing awareness of the unique cleaning ability of electrically ionized water (EIW) [47], a byproduct of electrodialysis, may be a factor to consider in the choice between ED and RO systems. NMR relaxation measurements were used to determine the water cluster size of electrically ionized water EIW. It is known that the water cluster size of EIW is signihcantly smaller than that of tap water. The smaller water cluster size is believed to enhance the penetration and extractive properties of EIW. Recently, EIW has been produced and used in several cleaning processes [47] in industry. 

In this major section the fundamentals and the main problems of these pressure-driven membrane processes will be summarized. A short overview will then be given of the membrane preparation methods and the most common materials used. Their application in organic media will then be reviewed in more detail, followed by comments on the current commercial membrane market and some perspectives for the future. 

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