The cleaning methods for microporous membranes mainly include chemical cleaning and physical cleaning. The following are detailed cleaning steps and precautions:

1、 Chemical cleaning

1. Acid alkali solution cleaning

Acid solution is effective in removing calcium based scales such as calcium carbonate and calcium phosphate, iron oxide, and metal sulfides.

Alkaline cleaning solutions include phosphates, carbonates, and hydroxides. These solutions can loosen, emulsify, and disperse precipitates.

When removing sediment that is particularly difficult to remove, such as silicates, alkaline cleaning agents and acid cleaning agents can be used alternately.

2. Chelating agent cleaning

Common chelating agents include ethylenediaminetetraacetic acid (EDTA), phosphocarboxylic acid, gluconic acid, and citric acid.

Chelating agents are used to remove sediment from contaminated membranes, such as gluconic acid, which is usually effective in chelating iron ions in strong alkaline solutions.

3. Cleaning with oxidants

When sodium bicarbonate or surfactants do not work, chlorine can be used for cleaning, with a suitable pH value of 10-11.

matters needing attention:

Choose appropriate cleaning agents and cleaning time to avoid damage to the microporous membrane.

The concentration of the cleaning agent should be appropriate, as excessive concentration may cause corrosion to the microporous membrane.

After cleaning, thoroughly rinse the surface of the microporous filter membrane to avoid residual cleaning agents.

2、 Physical cleaning

1. Backwash

Blow gas or liquid from the permeate side of the membrane to remove surface contaminants.

It should be carried out at a lower operating pressure (such as around 132kPa), and the recoil time generally takes 20-30 minutes.

2. Static soaking and hydraulic backwashing

For membrane modules that experience a decrease in permeability during long-term continuous operation and are difficult to regenerate, soak them in pure water and let them stand for more than 10 hours before conducting hydraulic backwashing.

3. Mechanical scraping

For tubular components, soft foam plastic balls and sponge balls (with a diameter slightly larger than the inner diameter of the membrane tube) can be used to clean the internal pressure pipe membrane.

This method is particularly suitable for cleaning the surface of contaminated microfiltration membranes mainly composed of organic colloids.

matters needing attention:

Physical cleaning is only effective for membranes in the early stages of contamination, and the cleaning effect cannot be long-lasting.

When mechanically scraping, be careful not to damage the surface of the membrane, especially for hard scale.

3、 Other precautions

High pressure water flushing: Before chemical cleaning, high-pressure water flushing can be used to remove surface dirt.

Temperature control: The temperature of the cleaning solution should be appropriate to avoid damage to the filter membrane caused by excessive temperature.

Use professional tools: During the cleaning process, professional tools such as diluent treatment, high-pressure airflow shaker, etc. can be used to assist in cleaning.

By combining chemical and physical cleaning methods, microporous membranes can be effectively cleaned to ensure their filtration efficiency and lifespan. Meanwhile, the cleaning method and steps can be flexibly selected based on the specific situation and degree of contamination of the filter membrane.