First, leaching The solvent to be leached may be neutral, acidic or basic depending on the source and nature of the vanadium slag. (1) Neutral leaching of roasted clinker After clinker calcined by sodium oxide at a high temperature, vanadium has been converted into a sodium salt of pentavalent vanadium, which is easily soluble in water. Therefore, most of the vanadium can be dissolved. Since a small amount of alkali remains in the clinker, the solution is alkaline and has a pH of about 7.5 to 9. Some soluble ions such as Fe 2 + , Fe 3 + , Cr 3 + , Mn 2 + , Al 3 + and the like will be hydrolyzed to form a precipitate. The hydrolysis pH of each of the above ions is as follows: ion Fe 2 + Fe 3 + Mn 2 + Cr 3 + Hydrolyzed pH 6.5 to 7.5 1.5 to 2.3 7.8 to 8.8 3.3 to 4 4 to 4.9 (2) Acid leaching of roasted clinker When the acidity is increased, low-priced vanadates such as Ca(VO 3 ) 2 , Mn(VO 3 ) 2 , Fe(VO 3 ) 2 , and Fe(VO 3 ) 3 are partially dissolved. For this purpose, the residue will be acid leached during the second stage of leaching to increase the vanadium leaching rate. When tetravalent vanadium is leached with sulfuric acid, a stable VOSO 4 can be formed: VO 2 +H 2 SO 4 =VOSO 4 +H 2 O Although the acidity is increased, the vanadium leaching rate is increased, but the impurities in the leachate are also increased correspondingly, which increases the difficulty in the purification process. (3) Alkali leaching and carbonation leaching of roasted clinker The calcium-containing raw material and the clinker to which the calcium oxide is calcined may be leached with an alkaline solution. E.g: Since the solubility product of CaCO 3 is smaller than Ca(VO 3 ) 2 , in the above metathesis reaction, Ca(VO 3 ) 2 is decomposed to form a CaCO 3 precipitate, and (4) Direct acid leaching Direct acid leaching of vanadium-containing raw materials, mainly used to treat vanadium-bearing uranium ore, while recovering uranium and vanadium. An oxidizing agent such as manganese dioxide or sodium chlorate is added simultaneously with the leaching. Dilute with near sulfuric acid using concentrated sulfuric acid. The leaching rates of uranium and vanadium can reach 98% and 85%, respectively. (5) Pressurized alkali soaking The direct alkali leaching of the vanadium-containing raw material can be carried out by introducing compressed air under high pressure at a temperature of about 200 ° C to dissolve the low-valent vanadium into pentavalent vanadium. Finally, it was recovered by crystallization of Na 3 VO 4 ·(5-12)H 2 O. If vanadium in the vanadium-containing raw material exists in the form of pentavalent vanadium, it can also be extracted by ammonia leaching. The leaching can be carried out under the conditions of 50 to 300 ° C, 0.1 to 20 MPa, and NH 3 to 8 mol/L. Second, the leaching equipment Sintering and agglomeration occur during the roasting process, and fine rinsing is still required for leaching to increase the leaching rate. Usually, the clinker is first water quenched, then wet milled, and finely ground to below -100 mesh, thereby significantly increasing the leaching rate of vanadium and shortening the leaching time of vanadium. Usually after the wet ball milling, the slurry is completely leached and sent to a thickener for solid-liquid separation. Alkali leaching of the calcined clinker, after the wet ball milling, carbonation leaching is required, usually in a mechanical agitation tank, and CO 2 gas (burning clinker tail gas or lime kiln gas) is blown into the bottom of the tank. It is also possible to use a gas agitation tank, commonly known as a Baqika tank. If the feedstock is loose porous lump or calcined pellets, a percolating leacher can be used. See Figure 1 above for the above. Figure 1 Dip tank A-gas agitation tank (Baqiuka tank); b-dip leaching tank Carbon Fiber Cutting,Carbon Composite Material Cutting,Carbon Fiber Composite Material Cutting Machine,Carbon Fiber Cutting Machine Jinan Zhuoxing Intelligent Technology Co., Ltd. , https://www.zxtcuttingsystem.com
Being immersed. The CO 2 can reduce the pH of the solution, which is more favorable for the decomposition and leaching of Ca(VO 3 ) 2 .