Preparing Sodium Tungstate from APT Crystal Mother Liquor
- Details
- Category: Tungsten Information
- Published on Wednesday, 13 January 2016 20:50
APT is short for ammonium paratungstate. It’s mainly white crystal with flake or needle shape. It’s used in the manufacture of tungsten trioxide or blue tungsten oxide. And it’s also used for manufacturing ammonium metatungstate and other tungsten compounds as additives in oil chemical industry.
Using ion exchange method can recycle sodium tungstate from APT crystal mother liquor. Through the experiment, following conclusions can be drawn:
1. The impact of resin form on adsorption: results of using Cl type or OH type resin to exchange pH = 3. 7 of material liquid are as picture. Because D354 resin is a weak base resin with large affinity to OH, it’s difficult to exchange. And Cl resin exchange for tungsten acid is much better. Before this, tungsten trioxide in the effluent concentration is under 0.39 / L. Therefore, the exchange resin should be Cl type.
2. The influence of flow rate: A column of material liquid flow rate for l, 2 m/h, and the turning point of outflow curve differs about one times. This phenomenon may be related to tungsten in acidic solution polymerization into large ion, the resin inside the diffusion rate of restricting the exchange rate, therefore, showed a slower rate of exchange, solution flow rate are requested not to fast.
3. The influence of pH: With the decrease of pH, the exchange of the turning point of curve BVR number increasea, namely through some delay. But when the pH is 2.9, solution has been unstable. Material liquid easily forms precipitation. Therefore, the material liquid is advisable for pH ~ 4.
4. The influence of the desorbed agent concentration on desorption:
Too big alkaline is bad for weak base resin. NaOH is an effective desorption agent of tungsten. At the same time, with NaOH increasing from 5% to 10%, lifting curve is steeper and maximum concentration degree can reach 18.
5. The effect of improving the desorption rate: Increasing the desorption rate from 2 m/h to 4 m/h, better effect of desorption can be received.
In conclusion, using weak alkaline macroporous resin to adsorb APT crystal mother liquor under acidic condition can obtain considerable exchange capacity. Load resin is easy to use NaOH desorption effectively. Sodium tungstate from desorption can obtain larger enrichment degree. Sodium tungstate can be prepared by evaporation and crystallization. Therefore, this method is a simple and feasible way of recycling tungsten and its investment and construction scale is small. Process is short.
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