Microfiltration Membrane Cleaning Method—chemical Cleaning

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Chemical cleaning essentially removes contaminants from membranes by reacting chemical reagents with deposits, fouling, corrosion products, and other pollutants that affect flux rates and product water quality. These chemical reagents include acids, alkalis, chelating agents, oxidants, and formulated products.

1. Acid and Alkali Solutions: Acids are effective at removing calcium-based scale such as calcium carbonate and calcium phosphate, iron oxides, and metal sulfides. Alkaline cleaning solutions include phosphates, carbonates, and hydroxides. These solutions loosen, emulsify, and disperse precipitates. Surfactants are often added to enhance the descaling properties of alkaline cleaning agents in order to remove wet oils, greases, dirt, and biological material. When removing particularly difficult-to-remove deposits such as silicates, alkaline and acid cleaning agents are used alternately.

2. Chelating Agents: In addition to strong acids and alkalis, chelating agents are also used to remove deposits from fouled membranes. Commonly used chelating agents include ethylenediaminetetraacetic acid (EDTA), phosphoric acid, gluconic acid, and citric acid. Gluconic acid is generally effective at chelating iron ions in strongly alkaline solutions, while EDTA is commonly used to dissolve alkaline earth metal sulfates.

3. Oxidizing agents: When NaOH or surfactants are ineffective, chlorine can be used for cleaning, with an optimal pH of 10-11.

References

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