In this review, we discuss the importance and significant roles of physicochemical principles in aqueous processing of inorganic materials. We highlight how the exploitation of these principles improves the processing steps, namely, leaching, production of suitable intermediates, and precipitation. The role of novel unit processes like ion exchange and solvent extraction in the concentration and purification of leach liquors and the separation of chemically similar elements in the leaching circuit is discussed. Since the entire operation is carried out in aqueous media, the review incorporates a discussion on the stability of water in acidic, alkaline, oxidizing and reducing conditions.