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What kind of chemicals are usually used for cleaning microporous membranes

Issuing time:2023-09-07 14:03

The use of microporous filtration membranes will become contaminated by particles, colloids, organic compounds and microbial growth over time. The fouling of pollutants will reduce the performance of the membrane, resulting in a reduction in membrane flux (flow rate through the membrane) or Transmembrane pressure (the pressure required to force fluid through the membrane) increases.

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So, what is the basis for judging membrane cleaning? It is generally judged based on two indicators. One is the transmembrane pressure (TMP). The transmembrane pressure is an indicator that reflects the degree of fouling of the filter membrane. When scaling occurs, the amount of time required to maintain the flow rate is Pressure will increase. The specific threshold at which cleaning is required depends on the system design, the required flow rate, and the acceptable pressure drop across the membrane. Filtration systems themselves are designed with specified operating limits, such as a maximum allowable pressure drop, beyond which the Cleaning, such as a set value of 10%-15%, then a value higher than this indicates the need for cleaning; another indicator is flux. Due to scaling, the permeate flow rate decreases over time, and the cleaning threshold can be based on a predetermined Percentage determination of flux drop. Therefore, regular monitoring of these parameters can help determine the optimal cleaning frequency.

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What chemicals are typically used to clean microfiltration membranes?

1. Acids, such as hydrochloric acid (HCl), citric acid and sulfuric acid (H2SO4), are usually used to remove inorganic dirt and dissolve and remove some inorganic salts or minerals deposited on the membrane surface, such as calcium carbonate (CaCO3) or calcium sulfate. (CaSO4) and other scales; it can also remove some metal oxide scales, such as iron oxide.

2. Alkali, sodium hydroxide (NaOH), potassium hydroxide (KOH) are often used to remove organic matter and biological dirt. Alkali are more effective in removing organic dirt on the filter membrane, including oil, grease, protein, and polysaccharide. or biological materials and other substances, which can decompose and emulsify organic compounds; alkali can help destroy and remove biofilm fouling by degrading EPS matrix and destroying microbial cells.

3. Detergents and surfactants. Some targeted detergents and surfactants are very effective in removing organic dirt on the filter membrane. They can reduce the surface tension of water and disperse and dissolve organic compounds, including oil. , grease, protein, polysaccharide or biological material, some particulate dirt, biofilm and dirt, mineral scaling, etc.

4. Oxidants, such as sodium hypochlorite (chlorine bleach), hydrogen peroxide and peracetic acid, etc. Chlorine, hydrogen peroxide or ozone can be used to decompose organic materials and kill microorganisms, remove organic dirt on the filter membrane, and decompose and oxidize organic compounds. , It can also remove some biofilm and biofouling, as well as iron and manganese dirt.

5. Chelating agents, such as ethylenediaminetetraacetic acid (EDTA) or citric acid, can be used to combine and remove metal ions such as calcium, magnesium or iron or minerals that may be present in the dirt layer, and can form stable complexes with metal ions. , reduce their reactivity and dissolve their compounds, and can also remove metal oxide fouling on filter membranes, etc.

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The above introduces some chemicals used in microporous filtration membrane cleaning. Chemical cleaning can restore membrane performance, but evaluation before cleaning and chemical selection are crucial, because over time, it may also cause membrane deterioration. breakage, so the need for cleaning must be balanced against the potential for membrane damage. It is best practice, of course, to follow the cleaning guidelines and recommendations provided by membrane manufacturers for their products to ensure optimal cleaning results while maintaining the integrity of the membrane. and service life. Hope the above is helpful to you.

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