Alumina filters

Example 7.8. Steinhart et al. [288] used the formation of a precursor film to fabricate nanotubes of polymers. For this purpose a porous alumina filter with cylindrical holes of defined size is brought into contact with a polymer melt (Fig. 7.17). This is done at a temperature, where the polymer is liquid, which is significantly above room temperature. The precursor film of the polymer wets the walls of the pores within, typically a few seconds. Before the pores are filled completely the filter is removed from the melt, the sample is cooled to room temperature, and the filter material is dissolved in potassium hydroxide. 

Benzoquinone (98%, Aldrich) is purified by slurrying it in CHjClj with two times its weight of basic alumina, filtering the mixture through Celite, concentrating the filtrate, and drying the residue under vacuum. 

Silver hydrosols (10 ml) with chloride anions were filtered by using ANODISC alumina filters (0.02 mm diameter) and a membrane filter holder supplied by Whatman Intern. Ltd. (England). After two successive filtrations, the liquid was free of metal particles, as detected by the total absence of plasmon absorption bands in the UV-vis region. The filter surface resulted coated by a layer of colloidal silver. 

Fig. 20.13 AFM images of alumina filters coated with Ag particles with (left) and without (right) chloride anions...

Porous anodic aluminum oxide (AAO) which characterized by a closely packed regular array of columnar cells is well-established and widely-used material for formation of nanostructures for SERS [2,3]. Particularly, promising SERS-active substrates were prepared by vacuum deposition of silver onto commercially available alumina filters with open pores of 200-300 nm diameters [4], Nanowires and nanorods have been fabricated by filling the AAO pores with transition- or noble-metals. However, due to multistage procedure these nanoarrays being sensitive are rather complicated in fabrication. 

When UDP-2-acetamido-2-deoxy-D-glucose and UDP-N-acetyl-muramyl-pentapeptide are together added to broken bacterial-cell preparations, a new product is formed that contains the sugar and sugar-peptide portions of the precursors. If cells broken by means of a sonic oscillator are used, it is necessary to carry out the incubations on a filter-paper support " the precise function played by the filter paper is not yet known. In contrast, if enzymes are prepared by grinding cells with alumina, filter-paper support is unnecessary and the product contains a linear glycan backbone in which the two sugar residues occur in the alternate sequence expected. ... 

Physical methods involve adsorption of the photosynthetic material on a support or the inclusion in a natural or synthetic gel (Table 1). Various supports were used filter paper discs, alumina filter discs,glass microfibre filters, or a column containing diethylaminoethyl (DEAE)-cellulose. The immobilization was obtained by filtration on the support. After adsorption, the filter containing the biological material can be protected with a thin alginate layer that is hardened with CaCl2 or with another filter disc. The immobilization of photosynthetic material by adsorption on an inert or ion exchanger support is a simple, economic, soft technique that preserves the native activity of the material. However, the interaction forces which intervene are weak, hence desorption of the biocatalyst may be observed. 

Whole cells of Chlorella vulgari Adsorption on an alumina filter disc Oxygen measurement Hg(N03)2, CuSo4... 

A new solution using an alpha-alumina filter deposited by serigraphic depositing has been developed for this application. 

Figure 6.9 Films of SWNTs on alumina filters from the as-purified sample (left) and the separated metallic fraction (right)...

Both the nano alumina and the PAC media can filter virus even though the pore sizes are 2 pm. This capabihty has been conunercialized for sampling vims. A 2.5 diameter, 5 long nano alumina filter (no PAC) is used to collect and concentrate virus for the purpose of assay of pollution at beaches and upstream and downstream of a mnnicipal plant. The vims are extracted using a solution containing beef extract (1.5% or 3%) and glycine (0.05 M) at pH 9. 

There are a number of technologies available for removing lead from drinking water. The most common are distillers, reverse osmosis, carbon, and alumina filters. 

Aerograph. A device for spraying powdered glaze or colour on the surface of pottery by means of compressed air. Aerox. Alumina filter ceramic with uniform micron-sized pores, made by Aerox Ltd, which company was acquired by Doulton Industrial Products, Stone, now part of Fairey Engineering. 

FIGURE 16.19 (a) Films of SWCNTs on alumina filters from the as-purified sample (left) and the separated metallic fraction (right), (b) A direct comparison of surface resistivity values in films of SWCNTs (fabricated via vacuum filtration) from the as-purified sample ( ) and the separated metallic fraction (O). (Adapted from Lu, F. et al., Chem. Phys. Lett., 497,57, 2010.)... 

Similar to treatment protocols of other chemical contaminants including arsenic, fluoride cannot be removed by typical water treatment means. Boiling, UV treatment, most methods of filtration, and most chemical treatment options are ineffective to remove fluoride from water. Synthetic ion exchange and precipitation processes, activated alumina filters, and reverse osmosis are typically used to remove fluoride from water in the developed world [5, 6]. There are no universally accepted used defluoridation techniques in the developing world with long felt need for development of appropriate technologies. 

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