GB959813A - A process for the extraction of a metal value or values - Google Patents

Abstract

Metal values are extracted from aqueous media containing at least one metal salt (other than an alkali metal salt) in solution or suspension by contacting the aqueous medium with a solution of a Koch acid or a carboxylic acid obtained by caustic fusion from an oxo-alcohol, in an inert organic solvent substantially immiscible with the aqueous medium, the latter being extracted at a pH above or substantially at the pH of hydrolysis of an undesired metal salt or salts (and preferably not more than 0.5 of a pH unit below the pH of hydrolysis of the metal salt it is desired to extract). The extraction may be selective if the pH is suitably adjusted, the metal salts which have a pH of hydrolysis at or below the pH of the aqueous medium forming with the carboxylic acid salts insoluble in water but soluble in the organic solvent. Metal values are recovered from the inert solvent solution by treating it with aqueous acid media which form water-soluble salt of the metal, and, by using aqueous media of a suitable pH, metal salts may be selectively stripped from an organic solvent solution containing more than one metal carboxylate. The process of the invention may be carried out using normal techniques of co-current or counter-current liquid liquid extraction. Examples describe the extraction of (1) nickelous ion Ni2+ and cobaltous ion Co2+ are extracted from separate solutions containing nickel sulphate and cobalt sulphate respectively with Koch acids (prepared from a C8 to C18 mixture olefinic hydrocarbons derived from cracked raffinate olefines) in kerosene; (2) nickel ions and copper ions from a mixed solution of copper sulphate and nickel sulphate at pH 5.5; (3) cobalt ions and nickel ions from mixed solutions of cobalt sulphate and nickel sulphate at pH=7.4; (4) copper ions and cobalt ions from mixed solutions of copper sulphate and cobalt sulphate at pH=5.8; (5) cobalt ions from cobalt sulphate solution at pH=8.7 using a mixture of C7 to C20 carboxylic acids derived from sodium hydroxide fusion of oxo-alcohol residues. The recovery of the metal ions from the carboxylic acid salts thereof is accomplished by treating the organic solution with sulphuric acid and separating the aqueous layer. Specifications 743,597, 798,065, 871,278 and 883,143 are referred to.ALSO:Metal values are extracted from aqueous media containing at least one metal salt (other than an alkali metal salt) in solution or suspension by contacting the aqueous medium with a solution of a Koch acid or a carboxylic acid obtained by caustic fusion from an oxo-alcohol, in an inert organic solvent substantially immiscible with the aqueous medium, the latter being extracted at a pH above or substantially at the pH of hydrolysis of an undesired metal salt or salts. Suitably the concentration of any one metal salt in solution or suspension is from 0.01M to 1M, preferably 0.1M, and the pH of this aqueous medium not more than 0.5 of a pH unit below the pH of hydrolysis of the metal salt it is desired to extract. The concentration of carboxylic acid in the inert organic solvent is generally 0.5M to 2M, preferably 1M, and the solvent is generally kerosene or an aliphatic hydrocarbon containing a minor proportion of an aromatic hydrocarbon. According to an embodiment of the invention a metal value is selectively extracted from an aqueous solution containing at least two metal salts by contacting the aqueous medium at a certain pH value with a solution of the carboxylic acid in an inert organic solvent of the type described, when the metal salts which have a pH value of hydrolysis at or lower than the pH of the aqueous medium form with the carboxylic acid salts insoluble in water but soluble in the inert organic solvent. The carboxylic acids may be regenerated for re-use by treating the organic solvent solution of their metal salts with an aqueous acid forming water-soluble salts of the metals. Methods of extracting a metal ion from an aqueous solution containing several metal ions, which involves partial removal of undesired metal ions before forming the desired metal salt of the carboxylic acid, or the complete extraction into the inert organic solvent of all metal ions contained in the aqueous solution are disclosed. The process of the invention may be carried out using normal techniques of co-current or counter-current liquid extraction. Specifications 743,597, 798,065, 871,278 and 883,142 are referred to.