The hot press leaching in a closed vessel can increase the reaction rate, and a gas or a volatile matter can be used as the leaching agent. At present, industrially, hot pressing technology can be used to leach mineral raw materials such as uranium , tungsten, molybdenum , copper , nickel , cobalt , zinc , manganese , aluminum , vanadium and gold .
(1) Hot pressure and anaerobic leaching
The boiling point of the solution increases with the increase of vapor pressure. The relationship between the boiling point of pure water and the vapor pressure is shown in Figure 1. The critical temperature of water is 374 Â° C. Therefore, the hot pressing leaching temperature is generally lower than 300 Â° C. Otherwise, The vapor pressure of water is greater than 10.13 MPa (100 atmospheres).
Hot-pressure and oxygen-free leaching is to increase the solubility of the immersed components in the immersion liquid, such as bauxite, tungsten ore, and potassium uranium ore, without using oxygen or other oxidants. Dip.
(2) Hot pressure oxygen immersion
Metal sulfides are almost insoluble in water, even when heated to 400 Â° C, but are readily soluble when present in the presence of oxygen. When the temperature is 110 Â° C, the oxygen pressure is 1.01 MPa, and the concentration of metal and sulfur in the liquid is 0.1 mol / liter, the Îµ--pH diagrams of SHO, MHO (M is Ni, CoZn, Cu, Fe) are as shown in the figure. 2 to Figure 7. The curves and tests in the figure show that the hot pressed oxygen immersion sulfide minerals generally follow the following rules:
(1) In an acidic medium with a temperature less than 120 Â°C, the metal enters the liquid in an ionic state, and the sulfur is precipitated as elemental sulfur, but the potential and pH of the elemental sulfur precipitated in the acidic medium are different, such as hot-pressure oxygen immersion yellow. iron ore, pH <2.5 to elemental sulfur, pH> 2.5 is mainly generated when sulfate.
(2) In a neutral medium with a temperature less than 120 Â°C, both metal and sulfur enter the liquid, and sulfur exists in the form of sulfate.
(3) In alkaline medium, both metal and sulfur enter the liquid, sulfur is mainly oxidized to sulfate, and some are low-oxide (such as SO 3 2- , S 2 O 3 2- , S 3 O 4 2- , SO 2 2-, etc. exist, the metal exists as a simple ion or a complex ion, or is precipitated by hydrolysis, and the amphoteric metal may exist in an anion form.
(4) When the temperature is lower than 120 Â° C, the reaction rate of oxidation of elemental sulfur to sulfuric acid is slow, and the reaction accelerates when the temperature is higher than 120 Â° C. Therefore, elemental sulfur can be obtained by hot pressing oxygen leaching of sulfide ore in a low temperature acid medium, otherwise sulfur is oxidized to a low oxide of sulfate or sulfur.
(5) When hot-pressure oxygen leaching of low-valent metal sulfides, the leaching is staged. For example, the reaction of low-temperature hot-pressure oxygen Cu 2 S and Ni 3 S 2 is:
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