Nickel, cobalt, copper, and iron powders can be manufactured by hydrometallurgical processes. It is possible to use a wide variety of materials, including waste solutions, as the metal-containing feed. Estimates of the capital cost of reduction autoclaves and ancillary equipment show the advantage of increasing the scale of the operation from 2 to 50 tons of metal produced per day. A major factor in the economics of producing the powders is the cost of purifying the solutions to give a liquor from which metal of the desired purity can be precipitated. Liquid–liquid extraction does not appear to have been used so far in a refinery in which metal is precipitated by hydrogen. The possible application of the technique is examined briefly. Metal powders can be precipitated directly by reducing with hydrogen some organic phases produced by liquid–liquid extraction of aqueous solutions containing several metals. A suitable solvent mixture is acarboxylic acid with hydrocarbon diluent. The total pressure necessary for reduction is lower than that required when water is the solvent. An important factor in considering the use of hydrometallurgical methods for producing metal powders is that in some cases the cost of obtaining metal is competitive with any other kind of process, and the fact that it is formed as powder is an added advantage. Also it is possible to make powders with physical characteristics that can be controlled withinnarrow limits over a very wide range. © 1969 Powder Metallurgy.
