Abstract: A process is provided for obtaining high quality high surface area zinc oxide from a roasted zinc sulphide concentrate by leaching with an ammoniacal ammonium carbonate solution. The process utilizes optional preliminary oxidation and water leaching steps to remove soluble impurities and an optional aqueous sulphur dioxide leaching step to selectively remove readily soluble zinc oxide. The process includes an improved source of roasted zinc sulphide concentrate. The process also includes an optional reduced pressure calcining step to produce zinc oxide with further increased surface area.

Abstract: Mixing of two liquid phases can be advantageously conducted when the two phases are supplied at steady flow rates. Variations in the rates of supply of the phases are compensated for by pumping each liquid at a constant flow rate higher than the maximum flow rate provided by the supply, and permitting recirculation of disengaged phase in the amount necessary to meet the demand of the system.