JPS6226838B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for neutralizing a sulfuric acid acidic zinc-containing solution dissolved in mine drainage or the like. Neutralization of zinc-containing solutions dissolved in mine drainage or smelting process water is generally done using slaked lime, which is inexpensive and has good reactivity, but gypsum also precipitates as a neutralization precipitate. The zinc quality of the zinc precipitate produced is low, and it has to be disposed of in dams, etc., resulting in high costs. Therefore, a method of using expensive ammonia or caustic soda as a neutralizing agent to prevent the precipitation of gypsum and the like has been adopted. In addition, when using calcium carbonate as a neutralizing agent,
Calcium carbonate has poor reactivity and the pH of the liquid does not rise easily, so in the past, the liquid temperature had to be heated to a high temperature of 80°C or higher to promote the neutralization reaction, which increased costs and prevented the smelting process. Its usage was limited, such as by utilizing waste heat. The present invention compensates for the conventional drawbacks of low zinc quality in neutralization product precipitates and provides a method that can economically recover zinc precipitates (mainly zinc hydroxide) with high quality. Figure 1 is a graph showing the relationship between temperature and residual zinc concentration in the solution (after 1 hour) when 1 and 2 equivalents of calcium carbonate relative to zinc were added to a zinc sulfate solution containing 1000 mg/Zn. As can be seen from this graph, the neutralization reaction of zinc cannot be satisfied unless the temperature is heated to 80°C or higher. In the present invention, a zinc-containing solution is neutralized with calcium carbonate, and at the time of neutralization, air is blown in to drive out carbon dioxide gas dissolved in the solution, promoting the neutralization reaction, and neutralizing the solution at a relatively low temperature. It is capable of completing neutralization. Figure 2 shows the relationship between the temperature and the concentration of zinc remaining in the solution when air is blown into the same zinc sulfate solution as described in Figure 1 when it is neutralized with calcium carbonate (2 equivalents) (after 1 hour).
As can be seen from this figure, the neutralization reaction progresses even at low temperatures of 50 to 60°C by expelling dissolved carbon dioxide gas by blowing air and improving reaction efficiency. In the present invention, as mentioned above, the liquid temperature is preferably 40 to 70℃.
Neutralization with calcium carbonate can be carried out at relatively low temperatures of 50 to 60°C, expanding the scope of its use. The neutralization reaction using calcium carbonate is as follows. ZnSO ₄ +CaCO ₃ +H ₂ O=Zn(OH) ₂ +CaSO ₄ +CO ₂ ↑ Next, in the present invention, the zinc precipitate mainly composed of zinc hydroxide produced by neutralization with calcium carbonate and gypsum are separated by flotation. . Conventional flotation separation methods for zinc precipitates and gypsum include separating gypsum from floating ore and zinc precipitate from precipitated ore in a weakly acidic region, and separating zinc precipitate from floating ore using sodium naphthenate as a collecting agent. There is a known method of separating gypsum into mineral deposits, but
In the present invention, for the neutralization product precipitate in the weakly acidic to alkaline range, an alkyl amine salt-based cation collector, etc. is used as a collector, starch, etc. is used as a suppressor, and gypsum is used as floating ore. This involves mutual flotation separation using zinc precipitates as precipitates. Example A zinc sulfate solution containing Zn ² +3 g/min was maintained at a temperature of 50°C, and while blowing air at a rate of 5/min, 25 g of calcium carbonate was added to adjust the pH to 6.5.
After the time neutralization reaction, 129 mg/day of cationic DAA (dodecyl ammonium acetate) was added as a scavenger and 90 mg/starch was added as an inhibitor.
was added to perform flotation. The flotation results are shown in the table below.

[Table] From the above table, it can be seen that a mixed slurry of zinc precipitate and gypsum can be separated in high quality by flotation to convert the gypsum into floating ore and the zinc precipitate into precipitate ore. As described above, the present invention can neutralize a zinc-containing sulfuric acid solution using calcium carbonate at a relatively lower temperature than the conventional method, and can separate and recover high-grade zinc and gypsum from the neutralized precipitate produced. It is extremely economical as there is no need to dispose of the neutralized precipitate.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between temperature and residual zinc concentration in the solution when a zinc sulfate solution is neutralized with calcium carbonate, and Figure 2 is a graph showing the relationship between temperature and residual zinc concentration in the solution when air is blown into the solution during the neutralization. It is a graph showing the relationship with the concentration of residual zinc in the liquid.

Claims (1)

[Claims] 1. Maintain the zinc-containing solution at 40 to 70°C, add calcium carbonate as a neutralizing agent while blowing air to generate zinc precipitate and gypsum, and then float the neutralized precipitate to remove zinc. A method for neutralizing a zinc-containing solution, characterized by recovering high-grade zinc precipitates by separating precipitates and gypsum.