Silica filters

Diatomaceous Silica Filter aids of diatomaceous silica have a dry bulk density of 128 to 320 kg/m (8 to 20 Ib/fU), contain paiiicies mostly smaller than 50 [Lm, and produce a cake with porosity in the range of 0.9 (volume of voids/total filter-cake volume). The high porosity (compared with a porosity of 0.38 for randomly packed uniform spheres and 0.2 to 0.3 for a typical filter cake) is indicative of its filter-aid ability Different methods of processing the crude diatomite result in a series of filter aids having a wide range of permeability. 

Although precipitates which require ignition will usually be collected in porcelain or silica filtering crucibles, there may be some occasions where filter paper has been used, and it is therefore necessary to describe the method to be adopted in such cases. The exact technique will depend upon whether the precipitate may be safely ignited in contact with the filter paper or not. It must be remembered that some precipitates, such as barium sulphate, may be reduced or changed in contact with filter paper or its decomposition products. 

Martens-Lobenhoffer et al. [119] used chiral HPLC-atmospheric pressure photoionization tandem mass-spectrometric method for the enantio-selective quantification of omeprazole and its main metabolites in human serum. The method features solid-phase separation, normal phase chiral HPLC separation, and atmospheric pressure photoionization tandem mass spectrometry. The internal standards serve stable isotope labeled omeprazole and 5-hydroxy omeprazole. The HPLC part consists of Agilent 1100 system comprising a binary pump, an autosampler, a thermo-stated column component, and a diode array UV-VIS detector. The enantioselective chromatographic separation took place on a ReproSil Chiral-CA 5 ym 25 cm x 2 mm column, protected by a security guard system, equipped with a 4 mm x 2-mm silica filter insert. The analytes were detected by a Thermo Scientific TSQ Discovery Max triple quadrupole mass spectrometer, equipped with an APPI ion source with a... 

The modification of silica gel with diethanolamine (DEA) resulted in a stable alkaline filter, capable to collect H2S, COS, CS2, S02, C02 and H20 from contaminated air.56 The presence of odorous mercaptanes and organic sulphides may be selectively determined, as these compounds do not react with the DEA and therefore are not collected on the filter. By means of this scrubber an automatic survey system has been developed allowing the detection and determination of the nature of odour nuisance, caused by industrial emissions of volatile organic sulphur compounds, up to the ppb-level. The system consists of two continuous, highly sensitive and fast responding sulphur analyzers. One of the detectors is equipped with an SO, scrubber and measures the total amount of non-S02 sulphur compounds. The other detects the organic S-compounds, using the amine-silica filter. 

Generation of Standard Reference Silica Filter Samples for Analysis by Colorimetric Methods, Method Number CRL-001, Chemical Reference Laboratory, NIOSH, Issued 2-5-74. 

Add the sintered-glass funnel to the Buchner filter system and attach the vacuum source. Fill the funnel to a depth of 2 cm using anhydrous silica. Filter the aqueous polymer solution through the silica. A blue colour will appear, indicating the Cud I) species that is formed in the presence of oxygen. The solution of polymer must be freeze-dried overnight to remove all water and leave a white solid polymer product. Yields >90% are typical. 

Celite . [Celite] Diatomaceous silica filter aids, catalyst carriers, filler, extender pigment, grinding aid, conditioner, processing aid, flatting agent for paints, agric. chonicals, paper, rubber, polishes, cleaners. 

Talsky 1988 1-6 Optical glass and silica filters, powders, TLC spots, films, crystals 107... 

Collect the precipitate on a sintered silica filter of low porosity which has been ignited and weighed before use. Transfer the barium sulphate (after filtration of the supernatant solution) to the crucible with a jet of hot water and wash with portions of a few mL of warm water until the filtrate gives no opalescence with silver nitrate solution. 

Preparation of Novel Ti02-Silica Filter Photocatalyst Derived from Titanium Alkoxy-Diolate Precursor... 

Preparation of novel Ti02-silica filter photocatalyst derived from titanium... 

Membranes with pores having pore diameters in the nanometer range ean be obtained by pyrolysis. Molecular sieves can be prepared by controlled pyrolysis of thermoset polymers [poly(vinylidene chloride), poly(furfuryl alcohol), cellulose, cellulose triacetate, polyacrylonitrile (PAN), and phenol formaldehyde] to obtain carbon membranes, or of silicone rubbers to obtain silica filters. For example, carbon molecular sieves can be obtained by pyrolysis of PAN hollow fibers in an inert atmosphere, which leads to dense membranes whose pores are opened by oxidation, initially at 400°-500°C and finished at 700°C [15]. These membranes are used to separate O2 /N2 mixtures. Le Carbone-Lorraine deposits a resin into a tubular macroporous substrate and then by pyrolysis creates a thin (< 1 pm) carbon active layer. Silicon rubber tubes can be pyrolyzed in an inert atmosphere at temperatures around 700°C followed by oxidation in air at temperatures from 500° to 900°C [16]. The membranes are composed almost completely of Si02 with pores having a maximum porosity of 50% and diameters fi om 5 to 10 nm. The permeabilities for He, H2, O2, and Ar range from 0.5 to 5 x 10 m s Pa. 

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