|Why does my Silver membrane appear discolored?||Millipore Silver Membranes are composed of 99.97% pure silver; however, they can become tarnished in certain environmental conditions. The formation of extraneous compounds most often results in cosmetic imperfections on the membrane surface and will not affect performance. See below for details on identification and removal of some of the more common contaminates. To minimize contamination of the membrane, store them in sealed packages.
Identification and removal of contaminants:
Examples of colored imperfections on silver membrane surface are as follows:
Ag2CrO4 (dark red)
AgCl or Ag2O (dark brown)
AgBr (light yellow)
Of these, AgCl and Ag2S are the most common compounds that form on the membrane surface. AgCl is a photosensitive sale that can be removed by flushing the membrane with ammonia solution.
Ag2S is a very stable compound which cannot be removed from the membrane without altering the structure. To remove other compounds, a flush with methyl or ethyl alcohol can be used.
The microporous structure of the Membrane Filters causes the disks to appear dull, grayish-white, unlike polished silver. There may be a slight difference in color between the 2 sides of the Membrane as a result of the manufacturing process.
|What is the maximum temperature that silver membranes can be used at?||Silver filters can be used at temperatures up to 550 C.|
|Can Silver Membrane Filters be cleaned and re-used?||Silver Membrane Filters can be cleaned and reused repeatedly. The membranes should be cleaned immediately after each use, and handled carefully to avoid membrane punctures and tears. Various cleaning procedures can be used, depending on the nature, type, and degree of contamination. There are four effective cleaning methods outlined below, that can be used to clean Millipore’s Silver Membrane Filters.
Immerse in a strong alkaline solution, a solvent, or an acid. Do not immerse in nitric acid, sulfuric acid, or cyanide solutions.
Place the silver metal membrane filter in a laboratory muffle furnace for approximately ½ hour to effectively remove organic contaminants from the membrane. Do not exceed 300C.
A combination of chemical and ignition cleaning may be the best method to completely regenerate the membrane. Immerse in a 10 percent concentration of hydrofluoric acid for ten minutes, followed by ignition cleaning in a muffle furnace, following the guidelines given above. This can allow for reuse of membrane up to 10 times.
Low intensity ultrasonics can be used to lean the silver metal membrane. The cleaning intensity and time will depend on the degree and type of contamination encountered. Do not use high intensity ultrasonics.
|What is the shelf life of Silver membranes?||This product is guaranteed from 1 year of purchase. There is no shelf life for Silver membranes, however, you may observe slight discoloration due to the formation of extraneous compounds after prolonged storage.|