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Molecular weight cutoff (MWCO)

Molecular weight cutoff (MWCO) is an important term in membrane filtration. It describes the pore size or rejection capability of a membrane. MWCO is in the unit of Dalton, or Da in short, it equals to the molecular weight (MW) of a known compound e.g. dextran, polyethylene glycol, which is 90% retained by the membrane. For example, in Figure 1, the MWCO of this membrane is regarded as 10,000 Dalton.

Because the method of MWCO determination is not standardized, there could be rejection variations between membranes with the same claimed MWCO among different membrane suppliers.

• Membrane type:MF

• MWCO:(MF)> 100 kDa

• Pore size:0.1 – 10 µm

• Species rejected:Suspended solids, bacteria, colloids, fats etc.

Main applications Microfiltration

• Pre-treatment of UF/NF/RO

• Microbial removal

• Algae concentrating  

• Membrane type:Ultrafiltration (UF)

• MWCO:1 – 500 kDa

• Pore size:0.01 – 0.1 µm

• Species rejected:Suspended solids, bacteria, viruses, colloidal silica, polypeptides, proteins, antibiotics, etc.

Main applications Ultrafiltration (UF)

• Pre-treatment of NF/RO

• Drinking water production

• Enzyme/protein/antibiotics separation

• Gelatin/juice concentration

• Membrane type:Nanofiltration (NF)

• MWCO:0.2 – 10 kDa,

• Pore size:1 – 10 nm

• Species rejected:Multivalent ions, organic matters, dyes, sugars, antibiotics, etc

Main applications Nanofiltration (NF)

• Drinking water production

• Organic matter/hardness/sulfate removal in brackish/sea water

• Sugar separation

• Lactose/whey demineralization

• Membrane type:Reverse osmosis (RO)

• MWCO:< 200 Da

• Pore size:< 1 nm

• Species rejected:Salts, sodium ions, micropollutants e.g. PFAS, pharmaceuticals residues, etc.

Main applications Reverse osmosis (RO)

• Seawater/brackish water desalination

• Dewatering /concentrating

• Demineralized water production

• Boiler feed purification

Memtik water and filtration and separation specialists help clients to select the most appropriate membrane based on the particle size or molecular weight of the species need to be filtered out/retained. Please contact us for more information or quotation at memtik@c2csingapore.com, or call us on +65 9127 5988.

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