American Cyanamid Company

Richard J Boyle

William A Rickelton

Timothy J Brown

Disclosed are processes for the selective extraction of tin from aqueous acidic solutions bearing tin and other metal cations. Branched tertiary phosphine oxides comprising at least two branches per alkyl group show higher extraction coefficients, E, for tin than other metals, e.g. zinc (III), iron (II), iron (III), copper (II) and lead (II). Novel compositions for selectively extracting tin comprising combinations of symmetrical branched phosphine oxides and unsymmetrical phosphine oxides are also disclosed.

Selective recovery of tin by solvent extraction using branched tertiary

A process for the extraction of metals selected from the group consisting of zinc (II), silver (I), cadmium (II), mercury (II), nickel (II), cobalt (II), and copper (II) from an aqueous solution containing, in addition to said metals, metals selected from the group consisting of calcium (II) and magnesium (II) is disclosed. The process comprises contacting the aqueous solution having an equilibrium pH within the range of about 0.2 to about 3 with an extractant. The extractant comprises an organic-soluble dithiophosphinic acid or ammonium, alkali or alkaline earth metal salt thereof represented by the formula: ##STR1## wherein R.sup.1 and R.sup.2 are the same or different and are selected from the group consisting of substituted or unsubstituted alkyl, cycloalkyl, alkoxyalkyl, alkylcycloalkyl, aryl, alkylaryl, aralkyl and cycloalkylaryl radicals having from about 2 to about 24 carbon atoms and X is either hydrogen or an ammonium, alkali or alkaline earth metal salt forming radical.

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Somerville, NJ, United States of America

Richard J Boyle