Compared with Other Membranes, RO Membranes Can Get Water of Higher Quality

Filtration Accuracy

• The filtration accuracy of MF membrane is 0.1–10 μm, and the permeate meets reclaimed water reuse standards.
• The filtration accuracy of UF membrane is 10–100 nm, and the permeate meets drinking water standards.
• The filtration accuracy of NF membrane is 1–10 nm, and the permeate meets direct drinking water standards.
• The filtration accuracy of RO membrane is less than 1 nm, and the permeate meets pure water standards.

Molecular Weight Cut-Off

• The molecular weight cut-off of MF membrane is 500000 Dalton and above.
• The molecular weight cut-off of UF membrane is 500–500000 Dalton.
• The molecular weight cut-off of NF membrane is 200–500 Dalton.
• The molecular weight cut-off of RO membrane is 100 Dalton and above.

Material

• MF membrane materials are divided into organic materials and inorganic materials (rarely used). Among them, organic materials include cellulose esters, polyamides, polysulfones, fluorinated materials, polycarbonates, polyesters, and polyolefins;
• UF membranes are mainly constructed of cellulose and its derivatives, polyolefins, polysulfones, fluorine-containing materials, etc.
• NF membrane are mainly made of polyamide composite membranes.
• RO membranes are mainly made of cellulose acetate membranes, aromatic polyamide membranes or polyamide composite membranes (frequently used).

Working Principle

MF, UF, NF and RO membranes filter feed water under the action of pressure. And the retained impurity varies as the pore size varies. However, the NF member differs from other membrane elements. Mostly NF membrane carries negative charges on the surface. Under the action of electrostatic, it can hinder the penetration of multivalent ions, which makes the rejection rate of multivalent ions is greater than that of univalent ions.

Operating Pressure

• The operating pressure of MF membrane is 0.3–7 bar.
• The operating pressure of UF membrane is 2–10 bar
• The operating pressure of NF membrane is 3.5–30 bar.
• The operating pressure of RO membrane is 12–70 bar.

Range of Application

• MF membranes are mainly used in the removal of pathogenic bacteria, the pretreatment of reverse osmosis and nanofiltration processes, the removal of algae and granular impurities in surface water such as reservoirs, lakes and rivers and the production of drinking water, etc.
• UF membranes are mainly used in mineral water, mountain spring water, drinking water processing; the pretreatment or post treatment of reverse osmosis membrane, the reuse of condensed water and reclaimed water, the treatment of municipal water, urban and rural drinking water, sand filter backwashing water and wastewater filtration, etc.
• NF membranes are mainly used in the pretreatment of RO process, the purification of drinking water and industrial water, wastewater purification treatment, the concentration of valuable components in the process, etc.
• RO membranes are mainly used in the preparation of purified water, industrial ultrapure water and medical ultrapure water, the desalination of salt water, the concentration, separation and purification of water and preparation of pure water in chemical process, the reuse of industrial waste water, etc.