I work at a precious metal refinery. We extract gold using aqua regia. However, sometimes Gold does not dissolve in AR. Sometimes it precipitates due to cold weather? Is there a way to make sure all of the gold dissolves in AR/
Dear Dr. Garg,
gold occurs in wide range of minerals and textures from invisible gold through electrum to Au tellurides and not to forget different silicates as hostrock minerals. Therefore, my recommendation first clarify which type of gold and host(rock) you are faced with. Then decide which grade of comminuton you have to apply. More then any other commodity gold needs a good mineralogical/petrograhic preparatory work prior to processing.
See below:
•Au element
-native Au (100 % Au)
-electrum (> 30 % Ag)
•Au tellurides
–Calaverite: AuTe2veins (43.56 % Au)
–Sylvanite: Au0.75Ag0.25Te2 (34.4 % Au)
–Nagyagite: AuPbSb0.75Bi0.25Te2.5S6 (18.6 % Au)
•In mesothermal gold ores sulphide ore types can be subdivided broadly into pyritic (pyrite±pyrrhotite) and arsenical types (pyrite+arsenopyrite±pyrrhotite).
•Arsenopyrite in highly refractory ores is finer grained,
–As-deficient (27–32.5 at.% As),
–contains high average concentrations of submicroscopic gold (60–270 ppm),
–but does not contain inclusions of particulate gold.
•Arsenopyrite in free-milling ores is coarser grained,
–less As-deficient to slightly As-rich (30–35 at.% As),
–contains low or negligible concentrations of submicroscopic gold,
–but contains inclusions and fracture fillings of particulate gold.
•Pyrite also contains moderately high levels of submicroscopic gold (20–40 ppm), the concentration of which is directly related to As content of the pyrite.
•Reasons for refractory behaviour in pyritic ores include very
–fine-grained native gold inclusions in pyrite, or the
–presence of gold-bearing tellurides.
With kind regards
H.G.Dill
Dear Dr. Garg,
gold occurs in wide range of minerals and textures from invisible gold through electrum to Au tellurides and not to forget different silicates as hostrock minerals. Therefore, my recommendation first clarify which type of gold and host(rock) you are faced with. Then decide which grade of comminuton you have to apply. More then any other commodity gold needs a good mineralogical/petrograhic preparatory work prior to processing.
See below:
•Au element
-native Au (100 % Au)
-electrum (> 30 % Ag)
•Au tellurides
–Calaverite: AuTe2veins (43.56 % Au)
–Sylvanite: Au0.75Ag0.25Te2 (34.4 % Au)
–Nagyagite: AuPbSb0.75Bi0.25Te2.5S6 (18.6 % Au)
•In mesothermal gold ores sulphide ore types can be subdivided broadly into pyritic (pyrite±pyrrhotite) and arsenical types (pyrite+arsenopyrite±pyrrhotite).
•Arsenopyrite in highly refractory ores is finer grained,
–As-deficient (27–32.5 at.% As),
–contains high average concentrations of submicroscopic gold (60–270 ppm),
–but does not contain inclusions of particulate gold.
•Arsenopyrite in free-milling ores is coarser grained,
–less As-deficient to slightly As-rich (30–35 at.% As),
–contains low or negligible concentrations of submicroscopic gold,
–but contains inclusions and fracture fillings of particulate gold.
•Pyrite also contains moderately high levels of submicroscopic gold (20–40 ppm), the concentration of which is directly related to As content of the pyrite.
•Reasons for refractory behaviour in pyritic ores include very
–fine-grained native gold inclusions in pyrite, or the
–presence of gold-bearing tellurides.
With kind regards
H.G.Dill
Have you tried the bacterium C. metallidurans which apparently has the specialty of attracting metal grains?
- Badges
- Science topic
- Similar topics
- Phytochemistry
- Extracts