Molybdenum intermediate treatment - ammonium molybdate production

In the process of molybdenum ore beneficiation , some processes produce a low-grade molybdenum ore that is difficult to recover by flotation; some have too high levels of impurities to obtain qualified molybdenum concentrates (or low-grade molybdenum concentrates). The use of these unqualified molybdenum concentrates and molybdenum ore to produce ammonium molybdate is one way to recover this portion of molybdenum.
1. Chemical beneficiation of molybdenum ore deposits Yangjiazhangzi molybdenum ore produces a molybdenum ore with 0.6 to 0.8% molybdenum in the beneficiation process. The process for producing ammonium molybdate as raw material is as follows:
First, the molybdenum ore is concentrated to a concentration of 60% solids, and leached by adding sodium hypochlorite solution. The reaction formula is as follows:

MoS ₂ +9NaClO+6H ₂ O → Na ₂ MoO ₄ +2Na ₂ SO ₄ +9NaCl+3H ₂ O

The sodium hypochlorite solution contains 130-140 g/L of NaClO and 50-60 g/L of NaOH. The leaching temperature is 45 to 55 ° C, and the fineness of the ore in the molybdenum is 0.074 mm or less.
The sodium molybdate solution formed by leaching is added to hydrochloric acid to have a pH of 5 to 6, and then calcium chloride is added and boiled with steam to form a calcium molybdate precipitate. The reaction formula is as follows:

Na ₂ MoO ₄ +CaCl ₂ → CaMoO ₄ ↓ +2NaCl

After the precipitate was filtered calcium molybdate, calcium molybdate added a sodium carbonate solution to remove an exploded wherein heteroaryl flat heavy metal ions, the following reaction formula:

CaMoO ₄ +Na ₂ O ₃ ←→ Na ₂ MoO ₄ +CaCO ₃ ↓

Then, hydrochloric acid is added to make the pH of the solution = 0.5, and the reaction is carried out at 95 ° C to form a molybdic acid precipitate, and the reaction formula is as follows:

Na ₂ MoO ₄ +2HCl → H ₂ MoO ₄ ↓ +2NaCl
[next]

After separating the molybdic acid, it is directly dissolved in the ammonia water to form ammonium molybdate. The active product was decolorized, and then hydrochloric acid was added to adjust the pH to 2.5 to obtain white crystals of ammonium tetramolybdate dihydrate [(NH ₄ ) ₂ O•4MoO ₄ • 2H ₂ O]. Filtration, drying and pulverization to obtain a finished ammonium molybdate. The entire production process is shown below.

[next]

2. Low-grade molybdenum concentrate to produce ammonium molybdate
Some, such as processing plant and Tongshan Jinkouling concentrator, due to the influence of mineral-containing carbonaceous, molybdenum concentrate containing molybdenum flotation obtained only 20 to 35%. The plant uses chemical beneficiation to make ammonium molybdate. The production process is as follows: First, the low-grade molybdenum concentrate is dried and calcined into molybdenum trioxide, and the reaction formula is as follows:

2MoS ₂ +7O ₂       4.5 hours   →   2MoO ₃ +4SO ₂ ↑
600 ～ 650 °C

Then, the molybdenum trioxide is leached with ammonia water to form ammonium orthobewate, and the reaction formula is as follows:

MoO ₃ +2NH ₄ OH    3 hours   → ( NH ₄ ) ₂ MoO ₄ +H ₂ O

Iron hydroxide was removed by filtration and the like insolubles. The filtrate is added with sodium sulfide (or ammonium sulfide), and the copper ammonia complex in the leachate is converted into copper sulfide precipitate and separated from ammonium orthob molybdate. The solution of heavy metal ions is removed, nitric acid is added to make pH=2.5, and ammonium ortho molybdate is converted into ammonium tetramolybdate crystal, and the reaction formula is as follows:

4 ( NH ₄ ) 2MoO ₄ +6HNO ₃ →( NH ₄ ) ₂ O · 4MoO ₃ ↓ +6NH ₄ NO ₃ +3H ₂ O

The crystals were filtered and dried at 120 ° C for 3 hours to obtain white crystals of ammonium tetramolybdate. The production process is shown in the figure below. [next]