Filter borosilicate materials

Filter medium material for the removal of viable organisms from compressed air tends to be either of borosilicate glass microfibres or meltspun fleece or PTFE membranes, supported on 100% glass fibre woven fabric or polysulphone or polypropylene spunbonded textiles. 

A more concentrated (1000 ppm) solution of dibenzo-p-dioxin in methanol was irradiated for 1.5 hours under a 450-watt lamp fitted with a borosilicate glass filter while nitrogen was bubbled continuously through, the solution. Unchanged starting material was recovered to the extent of 85%. The principal photolysis product again was a dark brown insoluble gum similar to that described above. Its mobility on thin layer chromatography (TLC) was very low in the benzene/ethyl acetate (4 1) solvent used to separate the other products. 

Precleaning of material, sampling, and filtration in the field are not very different from the procedures used for the other trace metals described above, except that for Hg borosilicate glass bottles can also be used, and that samples collected for volatile, metallic mercury Hg(0) and dimethylmer-cury (DMHg) species are not filtered. When filtration cannot be carried out in the field, samples should be kept unpreserved, cold, and in the dark. More specific information about our techniques can be found in Baeyens80 and Leermakers et al.47,84... 

Pleated These cartridge filters are typically used in higher-purity applications, such as pharmaceutical and microelectronics. The filters can have a multi-layered construction or be single layer. Typical materials of construction include polypropylene, polyethersulfone, and borosilicate glass fiber. 

There are a variety of different depth filter and membrane filter materials used within the pharmaceutical processes. Depth filter are fibrous materials for example, polypropylene, borosilicate, or glassfibre fleeces (Fig. 3). Borosilicate and glassfibre materials are highly adsorptive and commonly used to remove colloidal substances, like iron oxide from water or colloidal haze from sugar solutions. 

The choice of the system to be used for collecting particulate matter depends on the water volume to be sampled and the expected particle concentration therein. Borosilicate glass microfiber filters proved to be appropriate to separate the suspended material from the aqueous solution for a sample size up to 300 L [14]. A limiting factor may be represented by filter plugging, as demonstrated in a validation study conducted by Uza and coworkers to test the efficiency of an automated preconcentration water sampler (APS) for PCDDs and PCDFs [21]. The APS system is composed of a two-stage particulate filtering unit with coarse and fine filters, and an Amberlite XAD-2 resin column to trap dissolved hydrophobic compoimds. Various filter combinations were tested and, in all runs, filter plugging was observed. 

The plate reactors are often used for photocatalytic oxidation of NOx in the gas phase [81-86]. These types of reactors were described in the previous subsection. Ao et al. studied photocatalytic oxidation of NO2 using plate reactor with inner source of irradiation (6 W UV lamp) [81]. The reactor s surface was coated by a Teflon film. Ti02 powder was coated on the glass fiber filter. Moreover, the plate reactor made of stainless steel with inner source of irradiation was used by Chen et al. for photocatalytic oxidation of NO [60, 82]. Yu et al. used plate reactor with outer source of irradiation for removal of NO [83]. This reactor was made of non-adsorbing plastic material. Top of the reactor was covered with a borosilicate plate. The photocatalyst was illuminated by 25 W cool daylight lamps. Other types of the reactors used for photocatalytic oxidation of inorganic pollutants were described elsewhere [87, 88]. 

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