The present invention relates to an apparatus and a process for efficient hydrophobic particles to gas bubble attachment in a slurry is provided. The process comprises: tangentially introducing a slurry stream into a cylindrical chamber having a cylindrical inner wall with sufficient volume and pressure to develop a vortex in the flowing slurry; introducing gas into the flowing slurry during at least a portion of its travel in the chamber, the gas being introduced orthogonally to the stream through means located at the chamber inner wall and for developing gas bubbles which move into the slurry. The apparatus comprises of: a cylindrical chamber having a cylindrical inner wall, the chamber being oriented in any direction, enclosed at both ends, and with an entry port to introduce the stream of slurry to develop a spiral flow of the stream along the chamber inner wall toward the output end, a porous wall to permit the introduction of gas orthogonally into the stream to develop gas bubbles within the stream, and an exit port to discharge the mixture of slurry and gas bubbles.