The treatment of mineral surfaces.

摘要

A treatment method for chemically removing discolouring transition metal oxide contaminants from the surfaces of mineral particles to improve their brightness is provided. The method involves the contacting of the mineral particles with a solution of sulphur dioxide in water whilst simultaneously activating the sulphur dioxide to a reducing sulphur containing species to reduce transition metals and render them soluble. Dissolution of the reduced transition metals is effected by utilising excess sulphur dioxide or by employing a mineral acid such as sulphuric acid in solution.