The main raw materials for industrial extraction of vanadium pentoxide are vanadite-containing coal mines and vanadium titanomagnetite. The grade of vanadium pentoxide in vanadite-containing coal mines is generally 0.5-1.5%, and vanadium titanomagnetite is vanadium pentoxide
Grade is generally between 1.0 and 5.0%.
There are two kinds of decomposition methods of vanadium ore, the first is sintering method, the pulverized ore powder mixed with soda ash or sodium salt and sintered at high temperature, so that the low-priced vanadium oxidized and converted into a pentavalent
Sodium vanadate, then soaked in water to dissolve the vanadium into the solution; The second is the acid solution method, the pulverized mineral powder is heated with dilute acid (mainly dilute sulfuric acid) to extract, so that vanadium can be directly decomposed into solution
The sinter was extracted with water, and the vanadium was put into the solution in the form of sodium metavadate, which was filtered and washed. The filtrate was crude sodium metavadate solution, and then the impurities were further purified and separated by chemical precipitation, solvent extraction and other processes, so that the vanadium was enriched to a certain concentration, generally above 15 g/l.
After adjusting the PH value of pure vanadium solution to 6.5-7.5, add four times the theoretical amount of ammonium bicarbonate or ammonium chloride solution as precipitator, control the temperature below 30 ℃, precipitate ammonium bicarbonate precipitation, filter, wash with 5% ammonium bicarbonate solution 2-3 times, then wash with 30% ethanol 1-2 times, dry, get pure ammonium bicarbonate product.
Factors affecting precipitation
In industrial production, the ph value of the leaching solution is about 8-9, and the addition of precipitator ammonium chloride and concentrated sulfuric acid can adjust the ph value to 2-2.5. Vanadium can be settled in the form of partial ammonium vanadate, but the precipitation is affected by the following conditions.
The concentration of vanadium
The higher the concentration of the powder in the original solution, the faster the growth rate of the crystal nucleus during the hydrolysis of vanadium precipitation, the faster the growth rate of the crystal nucleus, so the crystal structure is incomplete, the precipitated particles are not tight, the adsorbed impurities are more water, taste, sometimes bad control is easy to appear adhesive situation. In short, the higher the concentration of vanadium is, the faster the precipitation rate is, and the lower the grade of the precipitate is. Generally, the concentration of the original solution is controlled at 15-20g/L.