The Methods For Cleaning Tangential Flow Filter Membrane
The methods for cleaning tangential flow filter membrane
In the field of biopharmaceutical, tangential flow filter membrane cassettes or hollow fibers are widely used in clarifying, concentrating, desalting, and removing endotoxins. As a kind of precision filtration membrane, they can effectively and quickly separate the target object and impurities, but after use, various pollutants will accumulate in the membrane, resulting in reduced membrane performance and shortened membrane life. In order to restore the performance of the filter membrane, protect the filter membrane from contamination and blockage, and avoid cross-contamination between batches, cleaning the filter membrane after use is a very important part of daily maintenance.
Therefore, it is of practical significance to discuss the technical means to restore the pollution of filter membrane. This article will introduce several cleaning technologies of filter membrane.
The purpose of membrane cleaning is to adopt reasonable cleaning methods to clean and regenerate the polluted membrane, destroy the solute adsorption layer on the surface of the membrane, remove the impurities in the membrane pores, and restore the membrane to the original flux as much as possible. Filter membrane cleaning technology mainly includes physical cleaning, chemical cleaning and biological cleaning.
Physical cleaning
The common technology of physical cleaning is hydraulic cleaning technology and gas-liquid pulse technology, which is the basic cleaning method for the initial stage of filter membrane pollution, mainly used to eliminate reversible pollution of filter membrane. Hydraulic cleaning technology mainly includes low-pressure high-speed flow method, reverse pressure cleaning method, isobaric cleaning method and negative pressure cleaning method, etc., usually refers to the method of removing membrane pollutants by using gas, water or a mixed fluid of water and air in reverse or tangent direction. Gas-liquid pulse cleaning technology is to direct high pressure gas into the gap of the membrane filter device to expand the membrane hole, and then the pollutants are washed away by the liquid. In addition, physical cleaning technologies such as ultrasonic cleaning, mechanical vibration, sponge ball cleaning and pulsed electric field cleaning have also been applied.
Chemical cleaning
When the effect of physical cleaning is not good, chemical cleaning can be used, and this method is the most commonly used method for cleaning biological contaminants. Chemical cleaning is the use of reaction between cleaning agents and membrane pores and surface pollutants to remove physical cleaning difficult to remove the pollution. Chemical cleaning should also consider factors such as cleaning time, temperature and drug types. In the actual operation of the filter membrane system, the non-toxic and harmless cleaning agent with good cleaning effect should be selected according to the material and membrane material treated.
Principles for selecting chemical cleaning agents:
No chemical reactions can occur with the ultrafiltration membrane and other materials of the component.
The selection of drugs to avoid secondary pollution ultrafiltration membrane cleaning.
Acid solution cleaning: commonly used acid solutions are hydrochloric acid, citric acid, oxalic acid, etc., the PH of the prepared solution is 2-3 (the specific PH value depends on the material type), cycle cleaning 0.5-1h or soak 0.5-1h before cycle cleaning, that can effectively remove pollutants (DNA, polysaccharide, bacterial cells and inorganic dirt).
Alkali solution cleaning: The main commonly used alkali is NaOH, the concentration of the prepared solution is 0.5M, PH=10-12 (the specific concentration and PH value depend on the type of material), cycle cleaning 0.5-1h or soak 0.5-1h before cycle cleaning, that can effectively remove pollutants (protein, lipid and polysaccharide compounds).
Surfactant: Commonly used surfactants are SDS (sodium dodecyl sulfonate), Tween 80, Triton X-100 (non-ionic surfactant), cycle cleaning 0.5-1h or soak 0.5-1h before cycle cleaning, that can effectively remove pollutants (proteins, oils and other biopolymers), but the use of surfactants alone is not good. Need to be combined with other cleaning agents.
Oxidant cleaner: When acid-base solution and surfactant do not work, 200-400mg/L active chlorine (500-1000mg/L NaClO aqueous solution) can be used, PH=10-11, cyclic cleaning 0.5-1h or soaking 0.5-1h before cyclic cleaning. In addition, 1-3% H2O2 and potassium permanganate also shows a good cleaning effect in some occasions. H2O2 and NaClO are commonly used fungicides.
0.5M NaOH+200-400 PPM NaClO (25-45 ℃), which is the best cleaning agent for biological contaminants. NaOH can effectively hydrolyze most proteins, lipids and polysaccharide compounds. Adding NaClO to NaOH solution can enhance the cleaning ability. NaClO reagent can oxidize and degrade protein dirt and other organic dirt without affecting the surface of stainless steel. The normal cleaning procedure is cycle cleaning 0.5-1h or soak 0.5-1h and then cycle cleaning.
Cleaning condition
Operating conditions such as operating pressure difference, operating time, operating temperature and inlet flow rate are important factors affecting the cleaning effect during the cleaning process.
Under normal circumstances, the inlet flow rate is controlled at 4-8L/min/m², the cleaning temperature is controlled at 20-50℃, and the cleaning time is controlled at 0.5-1.0h. For cleaning pressure difference, it is generally recommended to reach 30-50% of the inlet flow rate through the flow rate. Because the pore size of the filter membrane is different, and with the increase of the use of the filter membrane, the cleaning pressure difference is uncertain, so do not take examples in detail. Note: In general, TMP should not exceed 1.5bar and inlet pressure should not exceed 2bar. If during the first cleaning, the feed pressure can be controlled below 1bar, and the return pressure can be controlled at about 0.5bar.
Recommended methods for biological contamination cleaning
Under normal circumstances, most biological products can be cleaned completely at room temperature by using 0.5M NaOH solution for 0.5-10h.
Here are some special cleaning methods.
Biological cleaning
Biological cleaning refers to the removal or decomposition of pollutants such as polysaccharides and proteins in the polluted substances of the filter membrane through biological agents or enzymes with high biological activity.
Enzyme detergent: such as 0.5-1.5% pepsin, trypsin, etc., can effectively remove protein, polysaccharide, oil pollution substances. Because the enzyme reaction takes a certain time, and usually the reaction is incomplete, and it is also a protein, it will produce new pollution, so it is necessary to clean again with other cleaning agents, and therefore, the use of enzyme cleaners is the least recommended among all cleaning agents.
About Guidling
Guidling Technology is a national high-tech enterprise focusing on biopharmaceuticals, cell culture, purification and concentration of biomedicine, diagnosis and industrial fluids. We have successfully developed centrifugal filter devices, ultrafiltration & microfiltration cassettes, virus filter, TFF system, depth filter, hollow fiber, etc. Which fully meet the application scenarios of biopharmaceuticals, cell culture, and so on. Our membranes and membrane filters are widely used in concentration, extraction and separation of pre-filtration, microfiltration, ultrafiltration and nanofiltration. Our many product lines, from small, single-use laboratory filtration to production filtration systems, sterility testing, fermentation, cell culture and more, meet the needs of testing and production. Guidling Technology is looking forward to cooperating with you!
