Method and apparatus for separating substances from liquids by flotation

Abstract

A method for separating substances from liquid by flotation using bubbles which comprises adsorbing a substance present in a liquid on bubbles, floating the bubbles adsorbing the substance and separating the substance from the bubbles, characterized by allowing the bubbles adsorbing the substance to ascend through a fluid route in a tube independent of the ambient turbulently flowing liquid and then collecting and separating the substance from the liquid at the upper end of the tube. An apparatus for separating substances from liquids by flotation using bubbles which comprises a vertical column provided at the bottom thereof with a gas-diffusing means and a tube placed inside the vertical column, the tube being smaller in diameter and length than the vertical column and being provided with a means for collecting bubbles at the lower end thereof and a means for accommodating and concentrating the collected bubbles at the upper end thereof. These method and apparatus are useful for the treatment of waste water and industrial effluents or of mineral extracts, especially for the purpose of recovering useful substances from a solution or suspension thereof or removing heavy metals and the like harmful substances from effluents.