A process for the treatment of aqueous acidic liquors containing dissolved aluminium and/oriron compounds to produce an aluminium and/or iron sulphate water-treatment product is characterized by the combination of steps comprising contacting the liquor with a basic material capable of reacting with the dissolved aluminium and/or iron compound to precipitate aluminium and/or iron values, separating the precipitate in the form of a cake or slurry from the remaining liquor, treating the cake or slurry with sulphuric acid to re-dissolve aluminium and/or iron values and to produce a solution of aluminium and/or iron sulphate and separating suspended solid matter from the solution. The liquor may be a waste product from industrial processes or may be a mine effluent and the process avoids the need to dispose of these to waste. Where the liquor is derived from the acid activation of an aluminosiliceous mineral, the product contains dissolved silica, and a substantial quality of an oil bleaching agent is produced as a byproduct. The product may be mixed with a low molecular weight cationic polymer to give an enhanced flocculation performance.