Comprehensive extraction of uranium and molybdenum from a volcanic cryptoexplosive breccia

In addition to uranium and molybdenum symbiosis in a volcanic cryptoexplosive breccia, there are also associated elements such as silver (7.5 g / ton). The uranium grade is 0.150%. The East China Geological Survey Bureau 270 conducted a comprehensive test on the recovery of uranium and molybdenum. Finally, 60.60% of uranium-containing ammonium uranium and 51.5% of molybdenum concentrate containing molybdenum were obtained.
1. Ore characteristics Uranium-molybdenum mineralization is mainly in the fracture contact zone between the block volcanic breccia of the early rock mass and its late breccia-like rough surface. Uranium-molybdenum type ore is constructed.
Metal ore mineral pitchblende, molybdenite, molybdenum blue, molybdenum China, hematite, limonite, pyrite, galena, sphalerite and the like.
The gangue minerals are mainly quartz , fluorite and calcite .
Uranium is mainly in the form of bituminous uranium ore, and most of it exists in the pus of two cryptoexplosive breccia fracture zones. The common radioactive image shows the breccia structure, in addition to the mass, veins and stars. Spotted, fine mesh veins are dyed, the latter is most obvious.
In addition to molybdenum molybdenum, there are blue molybdenum ore and molybdenum, and molybdenum is white powder, radial, fibrous and needle-like. Among them, about 80% of molybdenum oxide and about 20% of molybdenum sulfide.
The structure of the ore is breccia, fine veins, veins, and stars. The chemical composition of the ore is shown in the table below.

Total analysis of ore chemistry

Ingredients

U

Mo

Th

H 2 O

Lost

SiO 2

Fe 2 O 3

FeO

content%

0.15

0.95

0.0032

0.68

3.05

76.07

1.2

0.9

Ingredients

Al 2 O 3

CaO

MgO

MnO

P 2 O 5

S

Na 2 O

K 2 O

content%

9.52

0.54

0.18

0.32

0.09

1.03

0.38

5.41

An important feature of ore is its water absorption and corrosivity. When directly leaching ore with hot water, the leaching solution is weakly acidic (pH=5.7-6.8), uranium is leached by 15%, and molybdenum is leached by 20%.
The sieve analysis shows that the uranium-molybdenum grade gradually increases with the decrease of the fraction, and the fine-grained leaching should be used in the test.
2. Uranium and molybdenum leaching According to the nature of the ore and the form of uranium and molybdenum, uranium and molybdenum are simultaneously leached by conventional acid and alkali methods.
(1) Sulfuric acid leaching The highest valence oxide of uranium and molybdenum is easily dissolved in hot sulfuric acid solution, and a small amount of molybdenum sulfide is also oxidized and leached at a high potential. The leaching of sulfuric acid was carried out according to the orthogonal table L26 (56) when the ore particle size was 0.10 mm, the amount of sulfuric acid (accounting for the ore weight) was 11%, the amount of manganese dioxide was 4%, the leaching temperature was 90 ° C, the leaching time was 3 hours, and the liquid-solid ratio was 2 At 1 o'clock, the uranium leaching rate was 95% and the molybdenum leaching rate was 88%.
Temperature is the main factor affecting the leaching of uranium and molybdenum, followed by the amount of oxidant (more obvious molybdenum). According to the electrochemical principle, when several redox species are present in one system, the potential value is minimized and first oxidized. Since E 0 uo 2 2+ /uo 2 =334 mV, E 0 Mo 6+ /Mo 5+ = 500, E 0 Fe 3+ /Fe 2+ =770 mV, added oxidant (manganese dioxide) The ferrous oxide is first converted into high-iron, and the high-iron oxidizes the uranium to oxidize the low-valent molybdenum. Therefore, the potential of the solution needs to be maintained at 680-750 mV to achieve the best leaching of molybdenum.
In order to increase the leaching rate of molybdenum, to reduce the ore particle size, reduce the liquid-solid ratio, increase the number of pulping, and select different oxidants for testing, the results are shown in the table below.

Effect of oxidant type and dosage on uranium and molybdenum leaching

Conditions and results

Oxidizer type and amount%

pH

Potential mv

Tail slag grade %

Leach rate%

Test number

uranium

molybdenum

uranium

molybdenum

7931-16

MnO 2 , 4

1

673

0.0035

0.056

97.67

94.11

17

HNO 2 , 2.5

1.3

766

0.0029

0.033

98.07

96.53

18

KMnO 4 , 2.0

1.5

672

0.0029

0.079

98.07

91.68

19

KClO 3 , 2.5

1.5

677

0.0037

0.058

97.53

99.8

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Note: ore particle size - 200 mesh accounted for 100%, sulfuric acid dosage 11%, leaching temperature 90 ° C, 3 hours, L / S = 1 pulp three times, each 20 minutes, 50 ° C.
The above table shows that when the ore material is -200 mesh accounts for 100%, the leaching rate of adding 2.5% molybdenum nitrate is significantly improved.
(2) Sodium carbonate leaching test according to the orthogonal table L9 (34) when the ore particle size is 0.1 mm, the alkali content is 6%, the potassium permanganate dosage is 2.5%, the leaching temperature is 90 ° C, the leaching time is 5 hours, and the liquid-solid ratio is Under the condition of 1:1, the uranium leaching rate is 94.67%, and the molybdenum leaching rate is 92.11%.
The verification test was carried out in the case where the ore particle size was -200 mesh and 100%, and the potassium permanganate dosage was increased to 2.5%. (See table below).

Alkali leaching verification test results

(6% Na 2 CO 3 , 3% KMnO, 90.5 hours, L/S=2 pulping three times)

Test number

Sample weight (g)

pH

Potential (millivolt)

Tail slag grade (%)

Leaching rate (%)

uranium

molybdenum

uranium

molybdenum

7931-26

1200

9.8

630

0.0065

0.037

95.67

96.11

Alkali leaching verification test results In summary, whether it is acid leaching or alkaline leaching, uranium and molybdenum leaching results are satisfactory. After comprehensive weighing, the alkali leaching method is proposed as the final solution, and the technological conditions are:
Ore particle size - 200 mesh accounted for 100%, sodium carbonate dosage 6%, sodium bicarbonate dosage 1.2%, potassium permanganate 2.5%, leaching temperature 90 ° C, leaching time 5 hours, liquid-solid ratio 2:1, pulping three times, Each time 30 minutes, 50 ° C, disc wash once.
3. Uranium and molybdenum separation The extraction and separation of molybdenum from uranium containing solutions has been reported. In this experiment, 7201 amine-assisted extractant was used to extract and separate molybdenum under acidic conditions, then uranium was extracted with 7301 most amine, and then uranium and molybdenum concentrate were precipitated from the stripping solution.
After extraction five sections over the next three minutes to obtain (1) a base extraction immersion molybdenum acidified with sulfuric acid to pH = 2.5 with 0.1M7201 + 7% TBP + extractant in kerosene compared 0 / A = 1/4, the oscillation The organic phase has a molybdenum concentration of 8.8 g/l and a uranium content of 0.11 g/l. The raffinate aqueous phase has a molybdenum concentration of about 0.04 g/l and uranium 0.6 g/l. The drinking and organic phases were washed with 1.0 M sulfuric acid solution to remove uranium, then washed with water until neutral, and finally contacted with 12% NH 4 OH + 10% (NH 4 ) 2 CO 3 solution at 0/A = 1/5. Stripping molybdenum in three minutes. After three-stage back extraction, the lean organic phase contains 0.08 g/L of molybdenum and a trace amount of uranium.
The stripping solution was neutralized with a sulfuric acid solution (solution from an acidified organic phase) at 70 ° C to pH = 3, and stirred for 2 hours to obtain a precipitate of molybdic acid, which was burned to obtain molybdenum trioxide having Mo = 51.2%. It contains uranium 0.005%.
(2) Extraction of uranium The uranium-containing aqueous phase after amine extraction of molybdenum is extracted with 0.05M7301+3% mixed alcohol + kerosene at 0/A=1/6, shaking for three minutes, and extracted by five stages. The phase reached the drinking and the organic phase was back-extracted with 1.0 M NaCl + 0.05 MH 2 SO 4 at 0/A = 5/1 for two minutes. The uranium concentration in the three-stage back extraction residual phase was 0.004 g/L. about. The organic phase was washed to neutral with water and a trace of molybdenum remaining in the organic phase was removed with a 5% sodium carbonate solution.
The solution after the stripping was directly neutralized with ammonia water at 70 ° C to pH = 7 hours, and the uranium content of ammonium diuranate was 60.60%.

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