Preparation of pure molybdenum compound (3)

A ion exchange ion exchange purification process and related indicators as follows ammonium molybdate solution.

Brief Process and Index of Purification of Ammonium Molybdate Solution by Ion Exchange

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B with AH-80-7II mother liquor from the nitric acid decomposition luminance recovering molybdenite molybdenum mother liquor composition: Mo15.6g / L; Fe: 14.2g / L; SO 4 2- 65 ~ 67g / L; HN0 3 205g / L, and to a certain pH value stream through N0 ₃ ^- type ion exchange column effluent containing molybdenum to 1 ~ 1.4g / L, a molybdenum-containing resin case of 115 ~ 136g / L, H ~ adsorption rate 92.7% 92.8%. The loaded resin is rinsed with iron having a pH of 2.5 to 3, and desorbed with a 10% to 15% NH ₄ OH solution to obtain an ammonium molybdate solution containing 60 to 155 g/L of molybdenum. The desorbed resin is converted to N0 ₃ ^- type with 50 to 60 g/L HN0 ₃ .
The effluent containing 1 to 1.4 g/L of molybdenum is neutralized with NH ₄ OH to pH = 7 to 8, so that Fe ^{3+ is} precipitated as Fe(OH) ₃ , and the supernatant is adsorbed and recovered by AH-80-7II. Finally, the effluent contains 30 mg/L of molybdenum, and the total recovery of the process is 99.4% to 99.6%.
Extraction method
A separate amine extractant with a tertiary or quaternary salt from the mother liquor by the pressurized decomposition of oxygen luminance key ore mother liquor contained almost all of the rhenium starting material and 15% to 20% molybdenum, rhenium, molybdenum, and about 400g / L H ₂ S0 ₄ . Wherein the primary molybdenum and rhenium To ^{_{Mo 8 O 26 4-, MoO 2}} (SO 4) 2 2-, ReO 4 - and other forms exist. The effects of different amine extractants and sulfuric acid concentration on the extraction of molybdenum and niobium are shown in the following two tables.

Note: Organic phase: 5% different extractant - aromatic thinner (flash point 47. 2 °C );Liquid: 34g /L Mo , 0.24g /L Re , 380g /LH ₂ SO ₄ . [next]

It can be seen from the table that the tertiary amine or the quaternary amine can effectively extract the ruthenium in a wide range of sulfuric acid concentration, but the extraction rate of the molybdenum decreases remarkably with the increase of the sulfuric acid concentration.
CAS Institute of Chemical metallurgical raw rhenium, molybdenum extraction and separation were studied and found that a mixed solvent system of a primary amine with a neutral phosphorus weakly alkaline aqueous solution from high-concentration separation factor of molybdenum, rhenium, molybdenum extraction efficiency Up to 104, and the synergistic coefficient of neutral phosphorus for primary amine extraction is as high as 10 ³ .
In order to extract and separate molybdenum and niobium, the principle flow of the following figure is generally adopted, that is, firstly extracting molybdenum, niobium and separating with Cu by using an amine or a quaternary ammonium salt, and stripping with NH ₄ OH to make the molybdenum and zinc simultaneously collide. The liquid, the control conditions are selectively extracted from the stripping solution, and the molybdenum remains in the raffinate, and the opposite phase is extracted from the organic phase with perchloric acid. However, some of them are first extracted with a low concentration of tertiary amine (N235), and then extracted with a high concentration of tertiary amine. [next]

For example, the calcined mother liquor contains 8 to 11 g/L Mo, 0.1 to 0.2 g/L Re, 1.8 to 2.5 mol/L H ₂ SO ₄ , and 2.5% N235-10% octanol-kerosene in comparison (o/a ) = 1:5, first extract, use ammonia to back-extraction, add KCl to the extract to make potassium perrhenate. The extracted aqueous phase was extracted with 20% N235 -10%-sec-octanol-kerosene under the condition of (o/a) = 1:5, and the molybdate was obtained by stripping molybdenum with ammonia water. [next]
b The recovery of molybdenum and ruthenium from the mother liquor of the nitric acid-decomposing molybdenite by the combination of tertiary amine extraction and strong base cation resin exchange is shown in the following figure.

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The mother liquor contained: Mo 23 g/L; Re 0.O1 g/L: Cu 8.1 g/L; Fe 10.6 g/L; H ₂ SO ₄ 312.5 g/L. The organic phase was extracted with a mixture of 20% trioctylamine and tridecylamine-10% tridecyl alcohol-kerosene. When the ratio was 1, the distribution ratios of molybdenum and niobium were 7.30 and above, respectively. After the 4-stage countercurrent extraction in the mixing clarification tank, the extraction ratio of molybdenum was 99%, and the extraction ratio of rhodium was 100%. The supported organic phase was washed with 0.01 mol/L of H ₂ S0 ₄ 2 to remove the co-extracted copper and iron, and then the molybdenum and rhodium were back-extracted with 3 mol/L of NH ₄ OH 3 . The stripping solution is passed through a strong base anion exchange column, the hydrazine is adsorbed, and the hydrazine is desorbed with perchloric acid. The adsorbed ruthenium solution was subjected to evaporative crystallization to recover ammonium paramolybdate with a purity of 99.94%, and the highest content of impurities was iron (0.01%).
B P204 extraction In a weakly acidic medium, molybdenum (VI) can exist as MoO ₂ ²⁺ , so it is suitable for extracting molybdenum with an acidic phosphorus extractant:

MoO ₂ ²⁺ (aq)+2(HR ₂ PO ₄ ) ₂ (org)==== MoO ₂ (R ₂ PO ₄ ) ₂ (org)+2H ⁺ (aq)

As can be seen from the figure below, the high pH value of molybdenum can exist as an anion such as Mo ₇ 0 ₂₄ ^6- , which is not conducive to extraction; generally, equilibrium pH=2 is preferred. Fe ³⁺ in the solution is extracted simultaneously with MoO ₂ ²⁺ , and Cu ²⁺ is not extracted even when it reaches 2 g/L.

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