<p>We cannot recycle your filters. However, we have used Sims Recycling for many years (https://www.simslifecycle.com/) to recycle our scrap silver. </p>
Q: Can silver membrane filters be sterilized with ethylene oxide (EtO)? A: EtO sterilization is not recommended for silver membrane filters. There is a possibility that residual acetylene in the EtO can produce explosive silver acetylide capable of detonating the EtO vapor.
Silver membrane filters do not have a predetermined shelf life when stored properly. They should be kept sealed in their original packaging until use to minimize environmental exposure.
Over time, surface discoloration or silver compound formation may occur. This is largely cosmetic and does not affect pore structure, filtration efficiency, or membrane performance.
<p><strong>Q. Can silver metal membranes be cleaned?</strong></p>
<p>A. <strong>Sterlitech™ Silver Membranes: Cleaning Guidelines <br /></strong><br />Sterlitech’s <a href="/silver-membranes.html"> Silver Metal Membrane Filters</a> 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 Sterlitech’s silver metal membrane filters. <br /><br /><strong>Chemical Cleaning <br /></strong><br />Immerse in a strong alkaline solution, a solvent, or an acid. Do not immerse in nitric acid, sulfuric acid, or cyanide solutions. <br /><br /><strong>Ignition Cleaning </strong><br /><br />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 the following temperatures. <br /><br /></p>
<table>
<tbody>
<tr class="verdana11">
<td style="text-align: center;" rowspan="2" valign="top" bgcolor="#bdd3de" width="128">
<p><strong>Retention Rating </strong><strong>(microns) </strong></p>
</td>
<td style="text-align: center;" colspan="2" valign="top" bgcolor="#bdd3de">
<p><strong>Maximum Temperature </strong></p>
</td>
</tr>
<tr>
<td style="text-align: center;" valign="top" bgcolor="#bdd3de" width="114">
<p><strong>°C </strong></p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#bdd3de" width="118">
<p><strong>°F </strong></p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>5.0</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>550</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>1020</p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>3.0</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>400</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>750</p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>1.2</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>350</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>660</p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>0.8</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>300</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>570</p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>0.45</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>300</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>570</p>
</td>
</tr>
<tr class="verdana11">
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="128">
<p>0.2</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="114">
<p>250</p>
</td>
<td style="text-align: center;" valign="top" bgcolor="#d6e3ef" width="118">
<p>480</p>
</td>
</tr>
</tbody>
</table>
<p><br /><strong>Combination Cleaning </strong><br /><br />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. <br /><br /><strong>Ultrasonic Cleaning </strong><br /><br />Low intensity ultrasonics can be used to clean 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.</p>
Slight discoloration of a silver membrane filter is normal and typically cosmetic. Although silver metal membranes are made from 99.97% pure silver, they can form surface compounds over time due to environmental exposure, even when not in use.
Common silver compounds that may cause discoloration include silver sulfide (Ag₂S), silver chloride (AgCl), and other silver salts. These surface compounds do not affect pore structure, filtration efficiency, or membrane performance and are usually not a cause for concern.
To minimize discoloration, silver membrane filters should be stored in sealed packaging. In some cases, silver chloride can be removed with a brief rinse or soak in an ammonia solution, while other surface compounds may be reduced using alcohols such as methanol or ethanol.
Do not confuse discoloration with the membrane’s natural grayish-white appearance, which results from its microporous structure. Slight color differences between the two sides of the membrane are normal and are most noticeable in 3 µm and 5 µm pore sizes.
<p><strong>Q. What are the advantages of silver metal membranes over conventional membranes?</strong></p>
<p>A. Sterlitech™ <a href="/silver-membranes.html">Silver Metal Membranes</a> are 99.97% pure, thus unique in their ability to withstand extreme chemical and thermal stress, making them ideal for applications involving aggressive fluids and/or high temperatures. In addition, the purity of the membranes enables users to easily exclude and account for the few chemicals that react with silver, thus making test results and filtering operations more precise than available through traditional membranes.</p>
