Demineralisation

Demineralisation in water treatment is a process used to remove mineral salts and other ions from water, producing deionised or highly purified water . This process is crucial in many industrial applications, laboratories and in the production of high quality drinking water.

Demineralisation methods

The main water demineralisation methods include the following.

Ion exchange

• Cation exchange resins: remove cations (positive ions) such as calcium (Ca2+), magnesium (Mg2+), sodium (Na+) and potassium (K+) by replacing them with hydrogen ions (H+).
• Anionic exchange resins: they remove anions (negative ions) such as chlorides (Cl-), sulphates (SO42-), nitrates (NO3-) and bicarbonates (HCO3-) by replacing them with hydroxide ions (OH-).
• Mixed bed resins work in pairs: the cationic resin removes the cations and the anionic resin removes the anions, combining H+ and OH- to form pure water (H2O).

Reverse osmosis (RO)

• Uses semi-permeable membranes to remove most salts and minerals. Water is pushed through the membrane, separating it from contaminants.
• Reverse osmosis is particularly effective in reducing dissolved substances, bacteria, and other micro-contaminants present in water.

Electrodeionization (EDI)

• Combines electrolysis and ion exchange to remove residual ions. EDI uses electric current to continuously regenerate ion exchange resins, eliminating the need for chemical regeneration.

Applications for demineralization

• Pharmaceutical industry: production of ultra-pure water for pharmaceutical formulations and laboratory preparations.
• Power plants: treatment of boiler feed water to prevent scale and corrosion.
• Food and beverage industry: production of water used in beverages and foods, where high purity water is required.
• Electronics and semiconductors: production of ultra-pure water used in the manufacture of electronic components and semiconductors.
• Research laboratories: supply of deionised water for experiments and analyses requiring water without contaminants.