A flotation separation apparatus for separating particles in suspensions, feeds slurry containing the particles through an inlet into a contactor where gas is fed through an inlet to mix with the slurry, for example in a downwardly plunging jet, to form a gas-liquid bubbly two-phase mixture under pressure from an outlet restriction in a throttling duct. The mixture is passed through a flow manipulator configured to induce a high energy dissipation rate, for example by way of a Shockwave formed in a diverging section of the throttling duct reducing the size of the bubbles and brining those bubbles into intimate contact with particles in the mixture which is released into a separation cell where a flow manipulating draft tube is provided to reduce turbulence in the mixture. Alternative apparatus and methods for inducing the high energy dissipation rate and for reducing turbulence in the mixture are also described and claimed.