Cleaning Methods of Membrane Filter

The main application of membranes filter is the filtration of air, gases, or chemicals. Membrane filters provided by Hawach have excellent chemical compatibility so that they are also used for the filtration of solvents and acids, to which other filter types are not resistant.

Which of the following separation technique is most suitable to remove particles of size 0.1 -1 µm? It is available in pore sizes from 0.1 um to 10 um and multiple diameters, and therefore excellently suited for particle removal from solvents. Besides, there is no worry about contamination because all of them are made in a cleanroom. Longer lifetime is guaranteed by fresh sterilization and good thermal stability.

Selection Tips for Membranes Filter

There are some tips for type-selection. Nylon membranes filter is fit for filtration of aqueous biological solutions, alcoholic solutions, and non-aqueous HPLC/GC solvents, it is therefore recommended for the chemical industry. Sterile MCE grid membrane filter is not normal mixed cellulose esters membrane, its special color contrast provided by the membrane surface is good for particle detection and bacteria recovery, and the membrane filter provides a high degree of the internal surface area for adsorption of solvents, so it is also suitable for food and beverage test applications.

After a period of use, the membrane filter will be contaminated or blocked, which will decrease the water permeability and the filtration speed. Therefore, it is necessary to clean the membrane filter in time to prolong its separation performance and the water flux. Here below are the two most common and effective cleaning methods.

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Physical Cleaning Method of Membrane Filter

The physical cleaning method is to remove contaminants from the membrane filter surface by mechanical means. It would not bring new contaminants to the membrane filter with simple cleaning steps. It consists of a variety of methods, such as positive direction rinsing, backwashing, hydraulic methods, gas-liquid pulses cleaning, and cycle washing methods.

For instance, the backwashing method is to remove the contaminant on the surface by blowing gas or a liquid from the permeate side of the membrane filter. It should be carried out at a lower operating pressure (about 132kPa) to avoid membrane filter rupture. Generally, it takes 20~30min. However, the physical cleaning method is effective only for the membrane filter at the initial stage of contamination, and the cleaning effect cannot be sustained.

Mechanical Vibration: In some cases, membranes can be mechanically vibrated to shake loose particles and contaminants. This method is especially useful in preventing the buildup of deposits on the membrane surface.

Sponge Cleaning: Soft sponges or cleaning pads can be employed to gently wipe or scrub the membrane surface. This is a manual cleaning method suitable for delicate membranes.

It’s important to note that the suitability of these physical cleaning methods depends on the type of membrane material and the specific fouling or contamination issues encountered. Additionally, care should be taken to avoid damaging the membrane during physical cleaning, and the methods chosen should comply with the manufacturer’s recommendations. Regular monitoring and maintenance help ensure the optimal performance and longevity of membrane filters.

Chemical Cleaning Method of Membrane Filter

The chemical cleaning method employs the reactions between the chemical reagents and deposits and other contaminants that affect flux rates to remove contaminants from the membrane filter. These chemical agents include acids, bases, oxidizing agents, and formulated agents. The acid is effective in removing deposits, like calcium carbonate, iron oxide, and metal sulfide. The alkaline cleaning solution includes phosphates, carbonates, and hydroxides, which can loosen, emulsify, and disperse the deposits easily. When removing deposits such as silicates that are particularly difficult to remove, the alkaline and acid agents are alternately used.

For instance, Acid Cleaning: Purpose: Used to remove mineral scale deposits, metal oxides, and inorganic fouling. Common Acids: Hydrochloric acid (HCl), citric acid, phosphoric acid. Procedure: The acid solution is circulated through the membrane system for a specified period, followed by thorough rinsing.

Alkaline Cleaning: Purpose: Effective against organic fouling, grease, and certain inorganic deposits. Common Alkaline Solutions: Sodium hydroxide (NaOH), potassium hydroxide (KOH). Procedure: The alkaline solution is circulated through the membrane system, and the pH is adjusted to enhance cleaning efficiency. Proper rinsing is crucial to neutralize residual alkalinity.

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