Ammonium Paratungstate Extraction from Refractory Tungsten Ore

After a variety of ore dressing methods have been obtained to a certain grade of tungsten concentrate, it will also produce tungsten fine slime or tungsten refractory materials about 6 to 10% of the total tungsten (WO₃). This material is characterized by low grade of WO₃, high content of major impurity elements such as Mo, Sn, P, As, Si and so on. It is polluted by a variety of mineral processing agents and it can not return to mineral processing and reprocessing. It is necessary to extract tungsten from these refractory tungsten ores by an effective smelting method, which is the only way to improve the utilization ratio of tungsten resources comprehensively.

Due to the unique physical and chemical properties of tungsten, it is difficult to completely separate the impurity elements such as Mo, Sn, As, P and Si. So far, a simple and effective separation technology of stray tungsten has not been developed for industrial production. At present, the domestic manufacturers of ammonium paratungstate are basically using expensive tungsten concentrates as raw materials, and the production of ammonium paratungstate is achieved by strict control of the crystallization rate of APT, a special process is used to purify the processing junction. Tungsten is recovered from crystal mother liquid.

Some researchers have provided a new technology for the use of additives in the smelting process of tungsten fine mud or tungsten refractory materials to solve the simple and effective separation of stray tungsten, produce high quality ammonium tungstate under the condition of crystallization. The main process is as follows:

Through the process of alkaline boiling of raw materials, crystallization of sodium tungstate, acid removal of acid, tin removing, ion exchange and crystallization of ammonium paratungstate, additives Nany and Hmx are used to remove tin and phosphorus, arsenic and silicon respectively. The impurity removal rate was Sn to 100%, P > 99%, As > 98%, SiO₂ > 98%. The quality of the ammonium paratungstate product is up to APT-0 grade.

(1) Grinding: the size of raw material is 95% above the 320 screen.

Alkaline leaching: NaoH450 ~ 550g/l, S/L (solid / liquid ratio) 1: 0.9 ~ 1.2, 125~150°C, 1.3 ~ 2.0Kg/cm², 1.5 ~ 2.5 hours.

(2) Pressure filtration: separation of alkali leach residue and preparation of crude sodium tungstate solution.

Concentration and crystallization: crystallization temperature 110~120°C, volume evaporation rate 60 ~ 70%, separation of tungsten alkali, preparation of coarse sodium tungstate crystal, WO₃ base mother liquor return to alkali leaching.

(3) Dissolution: dissolve sodium tungstate crystals with tap water containing Ca < 0.025g/l, and prepare WO₃160 ~ 180g/l solution.

(4) In the presence of HmX and Na₂S, MoS₃ precipitation method was used to remove molybdenum, flocculation and filtration, and MoS₃ slag was separated by MoS3 precipitation method, and sodium tungstate solution containing Mo < 0.005g/l containing WO₃ > 150g/l was prepared.

(5) Alkali removing tin: additive Nany and oxidant 10 to 20Kg/TWO₃, NaOH 340 to 360Kg/TWO₃, pH 8.5 ~ 9.5, heat preservation for 30 minutes. Filtration and separation of tin slag to prepare sodium tungstate solution containing Sn < 0.0003g/l and containing WO₃150g/l.

(6) Diluent: dilute the acid with tap water containing Ca<0.025g/l to make the delivery liquid, containing about WO₃20g/l.

(7) Column tower exchange adsorption: resin height / diameter ratio H: D = 4: 1, line speed 15 ~ 20cm/ points, after the liquid contains WO₃ < 0.15g/l.

(8) Single column desorption: linear velocity 3 ~ 5cm/ points, desorption agent concentration 5NNH₄Cl+2NNH₄OH, peak fluid (ammonium tungstate solution) specific gravity 1.07 ~ 1.09g/cm³, containing WO₃180 ~ 210g/l.

(9) Crystallization of ammonium paratungstate: 85~95°C, volume evaporation rate < 50%, WO3 crystallization rate > 99%. The ammonium paratungstate product was washed at 50-60°C with 3% NH₄NO₃ lotion. Finally, the solubility of ammonium salt based on Xm- ion was greater than that of ammonium paratungstate, so that it was separated from tungsten.

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