In this study, the process of membrane cleaning by supercritical fluid extraction was investigated. Polypropylene microfiltration membranes, contaminated with oils, were treated in a batch process with a supercritical fluid (SCF). As extractant, pure supercritical carbon dioxide or supercritical carbon dioxide with admixtures of methanol, ethanol and isopropanol were used. Single-stage and multi-stage extraction was carried out and process efficiency was determined. The obtained results showed that addition of organic solvents significantly enhances the cleaning performance, which increases with increase of organic solvent concentration and decreases with increasing temperature. All three solvents showed a comparable effect of efficiency enhancement. The results confirmed that supercritical fluid extraction can be applied for polypropylene membrane cleaning.
The techniques of micro and nano structurization of surfaces of various materials are utilized in electronics and medicine. Such procedure as wet and dry etching allows to fabricate protruded or recessed micro and nanostructures on the surface. In the paper some examples of utilization of a surface structurization, known from literature, are described. Some structurization methods and experimental results for fabrication of the arrays of sharp microtips are presented. Wet and/or dry etching, and thermal oxidation process were used to form the arrays of sharp gated and non-gated, protruded or recessed silicon microtips on silicon wafer. For the first time, the arrays of silicon carbide (SiC) microtips on glass wafer have been produced by use of the transfer mold technique. Arrays of sharp microtips are used as field electron emission cathodes for vacuum microelectronics devices. Some electron emission measurements for these cathodes have been carried out. New application of silicon microtips array in biochemistry has been tested with satisfactory results.