GB626081A - Improvements relating to the recovery of silver from solutions - Google Patents

Abstract

Solutions containing a silver thiosulphate anionic complex are brought into contact with an anion exchange in salt form to cause exchange of the anionic complex, and the silver is removed from the exchanger by treatment with an acid, e.g. nitric acid, or salt, e.g. potassium carbonate, ammonium carbonate or nitrate, sodium sulphate or chloride, or base, e.g. ammonium or sodium hydroxide, or alternatively in metallic form by combustion of the exchanger. The silver solutions employed mostly derive from photographic processes; other solutions containing silver in cationic form are first treated with sodium, e.g. thiosulphate. Suitable exchangers are aniline black, aromatic amine-formaldehyde resins, basic melamine resins and aliphatic amine resins such as prepared from the polyalkylenepolyamines. An example relates to a resin prepared from formaldehyde, acetone and tetraethylene pentamine by the process of Specification 572,836, [Group I]. Hydrochloric acid is suitably used in converting the resins to salt form.ALSO:Solutions containing a silver thiosulphate anionic complex, particularly those deriving from photographic processes, are brought into contact with an anion exchanger in salt form to cause exchange of the anionic complex and the silver is recovered from the exchanger by treatment with an acid, e.g. nitric acid, or salt, e.g. potassium carbonate, ammonium carbonate or nitrate, sodium sulphate or chloride, or base, e.g. ammonium or sodium hydroxide, or alternatively in metallic form by combustion of the exchanger. Suitable exchangers are aniline black, aromatic amine-formaldehyde resins, basic melamine resins, and aliphatic amine resins such as prepared from the polyalkylene-polyamines. An example relates to a resin prepared from formaldehyde, acetone and tetraethylene pentamine by the process of Specification 572,836. Hydrochloric acid is suitably used in converting the resins to salt form.ALSO:Solutions containing a silver thiosulphate anionic complex are brought into contact with an anion exchanger in salt form to cause exchange of the anionic complex, and metallic silver is recovered from the exchanger. The silver solutions employed mostly derive from photographic processes; other solutions containing silver in cationic form are first treated with sodium &c. thiosulphate. Suitable exchangers are aniline black, aromatic amineformaldehyde resins, basic melamine resins and aliphatic amine resins such as prepared from the poly-alkylene-polyamines. Hydrochloric acid is suitably used in converting them to salt form.