Membrane filters ultrafilters

A more careful investigation was made by Perry et al. (14). In their experiments, a buffered silver sol prepared by dextrose reduction of ammoniacal silver nitrate was mixed with a solution of hydroquinone in a hydrogen atmosphere. Both solutions were deaerated before mixing. The mixed solution was stirred with hydrogen for one-half hour, then pressed through an ultrafilter under hydrogen pressure. The filtrate was analyzed for hydroquinone, and correction was made for retention of hydroquinone by the filter membrane. A small amount of... 

Acetylated hematoporphyrin (1 part by weight) is dissolved in 0.1 N sodium hydroxide (50 parts by volume) and stirred for 1 h at room temperature. After the stir period the solution is adjusted to pH 9.4 to 9.6 with 1 N hydrochloric acid. It is filtered through a 5 pm filter and then concentrated to (12.5 parts) of its original volume in an ultrafilter with 10,000 molecular weight cut off membranes. The solution is then purified via diafiltration maintaining constant volume with 120 volumes of water and keeping the pH at 9.4 to 9.6 with 0.1 N sodium hydroxide. This is also done at room temperature. After the purification, the solution is removed from the ultrafilter, diluted to 3/8 (18.8 parts) of its original volume and pH adjusted to 7.5 to 7.7 with 1 N hydrochloric acid. The solution is then stored at 4°C for 14 to 21 days. After... 

Many studies have pointed out that a CR ultrafilter can operate at a flux level of 300-400 L/(m h) when white waters are filtered. The reduction in organic compounds (COD, UV absorption at 280 nm, or sugar) using a UF membrane (cutoff 30-200 kg/mol) has been from 10% to 40% depending on the process water. The reduction of anionic trash is usually better (30%-90%) [48]. A pilot study showed that a high-shear filter (CR-nanofiltration unit) could operate without any pretreatment at a flux level of 50-120 L/(m h) when paper null clear filtrate was filtered. Mechanical erosion was a problem with some of the NF membranes used [18]. 

Filtration Traditionally, aquatic chemists have operationally defined dissolved species by filtration through a 0.45 pm pore size membrane. The term dissolved is erroneously used to describe the filterable metal fraction. Filterable and nonfilterable metals are more accurate and appropriate terms. For water samples, filtration through small pore size (0.01-0.45 pm) membranes can be used to separate small particulate and even colloidal species. Ultrafiltration that involves the use of small pore size filters and pressurized filtration has been used to separate macromolecules. Ultrafilters are available with molecular weight cutoffs (MWCO) typically between 1000 and 50 000. Cross-flow ultrafiltration, where water flow is parallel to the surface of the membrane is used for the efficient isolation of colloidal material from large volume samples. Adsorption losses to the large surface area membranes can be an issue and several methods employ correction factors to account for such effects. 

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