Solvent adsorption thermal effects

The dynamic moisture adsorption isotherm is another useful tool, exemplified by the water sorption/desorption of DMP 728 zwitterion as shown in Figure 16. DSC may not be helpful unless the technique is modified by punching a tiny hole in the pneumatic sample cap, from which the moisture or solvent may escape with a narrow thermal peak. Another method is to place the sample in silicon oil on the sample pan. The thermal effect of solvent boiling out is observed in the thermograph. 

In order to prevent the irrevisible adhesion of MEMS microstructures, several studies have been performed to alter the surface of MEMS, either chemically or physically. Chemical alterations have focused on the use of organosilane self-assembled monolayers (SAMs), which prevent the adsorption of ambient moisture and also reduce the inherent attractive forces between the microstructures. Although SAMs are very effective at reducing irreversible adhesion in MEMs, drawbacks include irreproducibility, excess solvent use, and thermal stability. More recent efforts have shifted towards physical alterations in order to increase the surface roughness of MEMS devices. 

The general properties of supercritical fluids make them an attractive alternative to liquid solvents in column operations where transport effects come into play. If supercritical CO2 is employed as the solvent, this advantage is further supplemented by the non-flammable, non-toxic nature of the fluid, and the relative ease of solvent recovery. Supercritical solvents also offer the potential to greatly enhance thermally driven separations through dramatic changes in component solubility, adsorptive characteristics, and thermal conductivity near the critical region. 

Chlorine is also harmful in most cases in which catalytic incineration rather than thermal incineration is used. It clearly makes Httle sense in the removal of VOC and the process odours sometimes associated with them if the organic molecules are recaptured from the air by carbon adsorption, only for the material that is removed from the bed during regeneration to be incinerated to waste. Thermal or catalytic incineration of the contaminated air is an effective way of cleaning it, and the solvent vapour present in the air makes an appreciable contribution to achieving the temperatures required. 

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