Flotation process

The flotation process is a method for the separation of particles from a mixture by causing some particles to collect on the surface of bubbles. Flotation is a separation technique used widely in the minerals industry, for paper, de-inking, and water treatment amongst others. It can also be used in the food and coal industries. The technique relies upon differences in the surface properties of different particles to separate them. The particles that are to be floated are rendered hydrophobic by the addition of the appropriate chemicals. Air is then bubbled through the mixture and the desired particles become attached to the small air bubbles and move to the surface where they accumulate as a froth and are collected, or if the non-desired particles float to the surface they are collected and discarded. The flotation process was developed on a commercial scale early in the 20th century at Broken Hill in Australia and is widely used for processing of sulphide minerals (copper, lead, zinc, nickel, cobalt etc...). When used in this connection, it is termed froth flotation.

The flotation process is also widely used in industrial waste water treatment plants, where it is applied to remove fats, oil, grease and suspended solids from waste water. These units are called Dissolved air flotation (DAF) units.

In particular, dissolved air flotation units is used in removing oil from the wastewater effluents of oil refineries, petrochemical and chemical plants, natural gas processing plants and similar industrial facilities.

Some important suppliers and innovators of DAF technology are REDOX Water Technology, Veolia and US Filter.