Stepwise process for recovering precious metals from solution

Details Stepwise process for recovering precious metals from solution Stepwise process for recovering precious metals from solution

1976-08-02

1977-08-02

Ozaki, G.

Specialized metallurgical processes, compositions for use therei

Processes

Free metal or alloy reductant contains magnesium

75 5A, 75106, 75118R, C22B 1108

Patent

active

040393275

ABSTRACT:
Precious metals such as gold and silver are recovered from aqueous cyanide solutions thereof by a stepwise process. The pH of the solution is, if necessary, initially adjusted to about 13 and thereafter is adjusted and maintained at 10 or above throughout the process. A "starter" carbonyl compound (e.g., formaldehyde or dextrose) which reacts with free cyanide ions is dissolved in the solution. Following this, an "accelerator" (e.g., hydrogen peroxide or a persulfate) is added and the solution is heated to aid in conversion of free cyanide ions to other chemical species. Finally, a "clarifier" (e.g., hydrazine or a hydrosulfite) is added and the elevated temperature is maintained for at least a brief period after the addition. The solution is then cooled and the elemental precious metal particles formed are allowed to settle and are separated from the supernatant solution.

REFERENCES:
patent: 1479542 (1924-01-01), Hirschkind
patent: 3215524 (1965-11-01), Fetscher et al.
patent: 3271135 (1966-09-01), Davidoff
patent: 3271136 (1966-09-01), Davidoff
patent: 3311468 (1967-03-01), Davidoff
patent: 3957505 (1976-05-01), Homick et al.

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