GB301342A - Improvements in the recovery of metals and metal compounds which are soluble in ammoniacal liquors - Google Patents

Abstract

301,342. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). Aug. 24, 1927. Ammonium compounds containing metals. - The recovery of metals and their compounds, which are soluble in ammoniacal liquors, is greatly facilitated by a preliminary chlorination at an elevated temperature and subsequent treatment with ammonia, or solutions of ammonium salts or both. The individual metals may then be recovered from the resulting solutions in any known manner, for example, by precipitation or electrolysis. In the chlorination treatment, which may be carried out with any'of the usual reagents, the metals to be recovered, such as silver, nickel, cobalt, copper and zinc, are almost completedy chlorinated before any appreciable amounts of other constituents, such as calcium, aluminium, and magnesium compounds, are attached, with a consequent saving in the use of the chlorinating agent. The temperature should preferably be regulated so that no appreciable amount of the chlorides is volatilized, and the operation may be carried out under pressure. According to the nature of the material the process may be carried out under simultaneous, prior or subsequent oxidizing or reducing conditions which must be, so chosen as not to produce free metals. Before leaching, any base metal present in a low state of oxidation should be oxidized to prevent any precipitation of nobler metals already in solution; also, in the case of sulphur bearing materials, it is necessary to destroy any sulphides already present or formed during the chlorination or other preliminary treatment. The process is improved by leaching the chlorinated materials with water, preferably at an elevated temperature, before further treatment. This removes the chlorides from the materials to be treated with ammonia, and also prevents corrosion of the apparatus employed. In addition, the chlorination agents can be recovered from the aqueous solution in a form in which it can again be employed in the process; this occurs when basic materials, which have not been chlorinated, are present. If necessary, such materials, such as lime, may be added prior to or during the treatment with water, so that no heavy metal passes into solution. Any silver chloride which may remain in the aqueous solution of chlorides may be separated, for example, by cementation.