The chemical oxidative decomposition method has extensively studied chlorine, sodium hypochlorite, ozone, persulfate, nitric acid and alkali oxidants to pretreat ore or concentrate to remove carbon, arsenic and sulfur at low temperature, normal pressure and stirring.
First, the chlorination method
Featured tailings Guangdong Lotus tungsten mine is high Arsenic metal sulfide ore, the oxygen pressure - hydrochloric acid leaching of Co, the Ni, Cu, leached 92% -200 mesh particle size, containing As, each about 14% S, Au 9g∕t. Gold is mainly embedded in the intergranular and fissures of the arsenopyrite. The largest particle size is 75μm, the smallest is 0.5μm, 70.59% is monomer or continuous body, and 29.41% is wrapped gold. The blasting cyanide carbon slurry method test, NaCN consumption 12kg ∕t, cyanide leaching time 16 ~ 24h, gold leaching rate only 57% ~ 68%, slag gold still reached 3.3 ~ 4.5g ∕t. Afterwards, oxygen was used as the oxidant. Under the other conditions, the leaching rate of gold increased to 90% to 94%, and the gold content of the slag decreased to 0.5-0.9 g∕t. The NaCN consumption is reduced to 8kg∕t, the leaching rate of gold is still 84%~87%, and the slag contains gold 1.l~1.4g∕t.
American Karin (Carlin) gold and Jie Lite valley (Jerrit Canyon) is a carbon-containing gold, arsenic pyrite gold deposits. A considerable part of the gold is slightly impregnated in the oxidized spherical pyrite. The main minerals affecting the cyanide leaching of gold are carbon and most of the hard-to-oxidize gold-bearing cubic pyrite and monoclinic crystal arsenopyrite. The oxidation of these minerals requires a strong oxidant, so chlorine gas oxidation is used. The Karin gold mine is one of the most difficult ore-treated ores. If only chlorine gas is used for pretreatment, the chlorine consumption may exceed the limit of 200kg∕t ore. Therefore, a section of Na 2 CO 3 liquid should be added before the chlorine gas is oxidized. Inflatable oxidation operation. The use of a two-stage oxidation process saves chlorine and reduces costs compared to a single chlorination process.
Second, the nitrification method
The nitrification method is a method of pretreating a raw material by adding nitric acid or nitrous acid.
Another process of nitrification is the Nitrox process developed by Hydrochem in 1982. It is one year later than Asenaufa and is also proposed for arsenic-containing refractory mines. The advantage of this method is that an air compressor is used to supply air under normal pressure instead of oxygen for oxidation treatment. Working in a sealed kettle at atmospheric pressure and temperature 85 ~ 90 ° C, HNO 3 160g ∕ L, Ca (NO 3 ) 2 form of NO 3 - 100g ∕ L, solid-liquid ratio 1: 5, concentrate size 80% -200 mesh, controlled oxidation reduction potential (for calomel electrode) leaching at 750 mV for ~1 h, almost all of Fe, As, S and other impurities were decomposed. The oxidized slag is mainly composed of gangue, gypsum and S°. It can be added with cyanide after being neutralized by filtration, or can be cyanated after filtering out the acid solution without neutralization. The cyanidation leaching rate of gold can be increased to over 90%, and the leaching rate of silver is also high. Due to the large weight loss of concentrate oxidation and the small amount of slag, it can be filtered by a filter. The ancient gypsum deposit in the slag is beneficial to the filtration operation. As precipitated in the slag with basic iron arsenate. However, due to some problems and difficulties in the process of oxidation treatment, 50% of S may generate S° and hinder the cyanide operation and the generated gypsum in the pulping reactor. It has been reported that only 5kg/h scale has been reported in the literature. In the micro pilot test, the design and investment and production cost estimates for the 10t∕d scale demonstration plant were completed in September 1988. The demonstration plant is intended to oxidize concentrates containing As 10.8%, Fe 27%, S 23.2%, Au 29.6g∕t.
Third, alkaline soaking method
The 3 # vein of Pingjiang Gold Mine is a quartz vein type low sulphide ore. 99% of the gold is encapsulated in arsenopyrite and pyrite. 86% of them are sub-pigmented and 13% are visible gold. The ore is a mixed ore with oxidized ore accounting for 12%. The ore contains Au 4.05g ∕t, Ag 1.5g ∕t, As 0.79%, Fe 2.58%. The ore was broken to 90% -320 mesh for direct cyanidation for 36h, and the gold leaching rate was only 25.93%. The same ore powder was firstly treated with a solution containing 3% of NaOH, and pre-treated for 32 hours at a solid-liquid ratio of 1:2 and normal temperature and normal pressure. After solid-liquid separation, it was washed with water for 3 times, and then with NaCN 0.05%, solid-liquid. The leaching rate of gold increased to 92.59% to 95.06% by stirring cyanidation for 24 hours in a 1:2 immersion liquid. After the alkali immersion liquid and the washing liquid and lime were added to precipitate As as CaAsO 4 , the removal rate of arsenic was 86.39% to 89.12%.
Fourth, the monosulfuric acid method
The method of oxidizing refractory gold-bearing sulfide ore using H 2 SO 5 instead of Cl 2 was invented by the Ontario Research Foundation of Canada. This method is suitable for the treatment of gold-bearing pyrite and arsenopyrite, but does not substantially decompose the pyrite, making its application limited. And H 2 SO 5 needs to be prepared at the production site, which greatly increases the total investment and production costs.
V. Nl113 catalytic oxidation method
Soft manganese ore was added H 2 SO 4 in a medium, the catalyst is added the N113, arsenopyrite and pyrite decomposes at 100 deg.] C and atmospheric pressure conditions. The pyrolusite (or oxidized calcined manganese carbonate) added during the process can be converted to a manganese sulfate product. N113 is not only inexpensive, but the reducing product formed after the reaction is easily oxidized and regenerated by MnO 2 or O 2 .
The raw materials used in the test were arsenic, antimony and sulphur gold concentrates from Longshan Gold Mine, which were denitrified by FeCl 3 and desulphurized by NaS. The main components were As 9.74%, S 16.87%, Fe 20.31%, Sb 0.072%, Au. 76g∕t, Ag 5g∕t. The optimum arsenic removal conditions selected by the condition test were temperature 100 ° C, H 2 SO 4 400 g ∕ L, N113 15 g / L, solid-liquid ratio 1:5, MnO 2 addition amount was 1 times the theoretical amount, leaching time 4 h, The leaching rate of arsenic is stable at 95.5% to 99.7%. The arsenic-depleted sulfur leaching residue is leached with sodium polysulfide, and the gold leaching rate is greater than 98.5%.
This method is used in the system of coexistence of arsenic and sulfur. The removal rate of arsenic is much larger than that of sulfur. It can be separated from pyrite by selective arsenic removal by conditions. In areas where manganese ore resources are scarce, oxygen can be supplied under sealed conditions to replace MnO 2 .
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