Flotation initially originated from the field of mineral processing. The importance of this process to the economy of the whole industrial world is considered to be enormous. Since for many years various particulate solids besides minerals have been extracted by using this effective gravity separation method with many interesting applications in the treatment of wastewater, looking for sustainability. Certain significant activities in flotation research were reviewed in the present, with main focus in the contribution of physical chemistry to flotation; i.e. zeta-potential measurements, contact angle etc., including examining the role of bubble and particle size played with regard to the process. Alternative bubble generation methods were examined, such as electro flotation and dissolved-air flotation-the latter technique is mainly intended for water treatment applications.