Baromembrane water treatment methods

Baromembrane water treatment methods

The demineralization of water by ion exchange and thermal demineralization ( distillation ) make it possible to desalinate water, almost completely desalinate it. However, the use of these methods revealed the presence of shortcomings: the need for regeneration , cumbersome and expensive equipment, expensive ion exchangers , etc. In this connection, baromembrane methods of water treatment were quickly spread. The group of baromembrane methods includes:

• Reverse osmosis (pore size 1–15 Å, working pressure 0.5–8.0 MPa) is used to demineralize water, it retains almost all ions by 92–99%, and with a two-stage system, up to 99.9%.
• Nanofiltration (pore sizes of 10–70 Å, working pressure 0.5–8.0 MPa) is used for

separation of dyes , pesticides, herbicides, sucrose , some dissolved salts, organic substances, viruses, etc.

• Ultrafiltration (pore sizes of 30–1000 Å, working pressure 0.2–1.0 MPa) is used for

separation of some colloids ( silicon , for example), viruses (including poliomyelitis ), carbon black, separation of milk into fractions, etc.

• Microfiltration (pore size 500–20000 Å, working pressure from 0.01 to 0.2 MPa) is used to separate some viruses and bacteria , fine pigments, activated carbon dust, asbestos, dyes, separation of water-oil emulsions, etc.

The larger pores formed in the membrane, the more understandable is the process of filtration through the membrane, the more physically it approaches the so-called mechanical filtration.

The intermediate group is formed by so-called track membranes , which are obtained by irradiating polyester terephthalant films on a cyclotron by a stream of heavy ions. After exposure to the film with ultraviolet rays and etching with alkali, pores with a diameter of 0.2–0.4 μm (mainly 0.3 μm) are formed in the film. ^[one]