Salt immersion

Brining with an aqueous solution of an inorganic salt or acid (or alkali) as a leaching agent, common salt leaching agent is sodium chloride, ferric salts, cupric chloride, sodium hypochlorite, cyanide and the like.
(1) Sodium chloride solution Leaching sodium chloride solution can be used as a leaching agent for certain minerals. It can also be used as an additive in combination with hydrochloric acid or other leaching agents to increase the concentration of chloride ions in the immersion liquid, thereby improving the immersion components. Solubility in the immersion liquid.
Sodium chloride solution as a white lead ore, and adsorption type rare earth ore roasting fumes chloride leaching agent. The reaction of leaching leucite is:
PbSO ₄ +2NaCl ₂ +Na ₂ SO ₄
PbCl ₂ +2NaCl=Na ₂ [PbCl ₄ ]
The adsorbed rare earth ore is a rare earth weathering shell deposit formed by adsorbing rare earth ions in minerals such as weathered kaolin . The adsorbed rare earth component is easily 7% sulfuric acid or 6-7% g sodium solution or 1-2% ammonium sulfate or chlorine. The ammonium salt solution is leached, and the essence thereof is to wash the adsorbed rare earth ions, and then the mixed rare earth oxide is prepared from the immersion liquid by an oxalic acid precipitation method or an alkali precipitation method.
The leaching of the chlorinated roasting soot by the sodium chloride solution essentially converts the poorly soluble lead chloride and silver chloride into a soluble complex and then recovers lead and silver from the immersion liquid.
(2) Leaching of high-priced iron salt solution
As can be seen from the figure below, high-priced iron salts are ideal oxidants for the leaching of a series of sulfide minerals. Ferric chloride is commonly used as a leaching agent in production. It can be seen from the change of the free energy of the above two formulas that the reaction mainly produces sulfate, but the main element is sulfur when it is actually leached, which may be the slower rate of sulfate formation.

Tests showed that the iron salt leaching of sulfide minerals from high order is hard to easy: restrain luminance pyrite ore → → → chalcopyrite pentlandite → brightness → diamond mine sphalerite and galena → → → chalcocite Pyrrhotite. This sequence is slightly different from the standard reduction potential sequence of sulfide minerals, possibly due to differences in dissolution rates. The solution potential and reaction product can be controlled by adjusting the "# value of the immersion liquid and the high-valent iron ion concentration during leaching.
High-priced copper ions are also an oxidant. The order in which copper chloride leaches out sulfide minerals from difficult to easy is: pyrite → chalcopyrite → galena → sphalerite → chalcopyrite. Since cuprous chloride is hardly soluble in water, a mixture of copper chloride and sodium chloride is generally used as a leaching agent to convert low-valent copper ions into complex ions into the immersion liquid.
High iron salts and copper salts when employed as leaching agent, available oxidation (air, chlorine, soft manganese ore, etc.) and the like by electrolytic regeneration reagent.
The hardly oxidized molybdenum ore can be used as a leaching agent with a strong oxidizing agent (nitric acid, sodium hypochlorite, etc.), and then molybdenum is recovered from the immersion liquid in the form of calcium molybdate or ammonium molybdate. This method can be used to treat refractory molybdenum ore.
(3) Cyanide leaching cyanide is an effective leaching agent for gold , silver minerals and copper minerals. Cyanide leaching of gold, silver and copper is based on their ability to form stable soluble complex anions with cyanide, reducing gold, silver, The redox potential of copper makes them readily soluble in cyanide. Gold and silver can be recovered from the immersion liquid by zinc sinking or electrowinning or adsorption-electrowinning.
Leaching of gold and silver, CN ^- concentration is generally 0.03% to 0.25% equivalent to 10 ^-2 mol · L ^-1, the concentration of silver were 2 × 10 ^-3 kg · m ^-3 and 2 × 10 ^-2 kg · m ^-3, corresponding to _{^{a Au + = 10 -5, a}} Ag +10 -4, zinc replaced if the activity is 10 ^-4 mol · l ^-1 cyanide extraction of gold and silver can be plotted Au, Ag- ε--pH diagram of Zn-CN-H ₂ O system (top panel). It can be seen from the graph that when the pCN is the same, the equilibrium potential of gold is lower than that of silver, and gold is more easily leached. At the same time, the equilibrium potential of gold and silver decreases with the increase of free cyanide concentration in the liquid, and the gold and silver are more easily leached. . Impetus cyanide leaching gold and silver at the maximum pH≈9, therefore, often added to produce the protective base (lime) to prevent the chemical decomposition of cyanide and maintaining pH pulp value of 9 to 11.
It is generally believed that the cyanide leaching of gold and silver is a metal galvanic corrosion process. The leaching speed depends on the diffusion rate of oxygen and cyanide. The theoretical derivation is that the ratio of cyanide concentration to dissolved oxygen in the solution (molar ratio) is 6, gold. The dissolution rate reaches the maximum value, and the test value is 4.69 to 7.4, so the theoretical value and the experimental value are in agreement. Therefore, a cyanation leaching method is commonly used to increase the oxygen concentration in the leached slurry.

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