CS257577B1 - A method for neutralizing residual sulfuric acid in leaching leachable ores, especially uranium alumosilicetes - Google Patents

Abstract

The residual mash after leaching of difficultly leachable aluminosilicate type ores is mixed in stirred reactors with a mash of medium leachable ore with a carbonate content in a ratio according to the concentration of residual H2SO4 and neutralization capacity, the resulting mixed mash is mined until the content of free H2SO4 in the liquid phase is reduced to 50 to 250 kg/m^. Medium leachable uranium ores are ores in which the uranium carrier is various forms of titanium oxide of complicated composition.

Description

The invention relates to a process for neutralizing high residual concentrations of sulfuric acid during the treatment of difficult-to-leach uranium ores, especially of the aluminosilicate type, which solves the problem of replacing expensive neutralizing materials.

It has been previously proposed to treat the residual mash after leaching of aluminosilicate ore with waste sludges, intermediate products from physical treatment or ash from uranium-bearing coal in order to neutralize free H ₂ SO^. Here, for example, reference can be made to Czechoslovak Patent Application No. AO 214 476, in which it is proposed to treat the residual mash with ground and thickened waste sludges or intermediate products from physical treatment in a ratio of 0.2 to 0.8 tons of waste sludges or intermediate products per 1 ton of difficult-to-leach ore, to leach the mixed mash until it is in the liquid phase, containing the leached metal from the difficult-to-leach ore and the metal from the sludges or intermediate products, with a free sulfuric acid concentration in the range of 5 to 20 kg/m ³ .

In the later Czechoslovak AO 227 258, it was proposed to treat the residual mash after leaching of difficult-to-leach ore with ground ash obtained by fluidized combustion of uranium-bearing coal, to leach the mixed mash until the concentration of free sulfuric acid in the liquid phase is 5-20 kg/m ³ .

These methods solve the final processing of waste sludges and intermediate products from the physical treatment of ores, the metal content of which is below the economic level of costs for their hydrometallurgical processing. Their use for neutralizing residual acid solves the economical recovery of the metal contained in them. There is also a known method of neutralizing residual acid by adding easily leachable ores, especially uranium, with a high content of calcium carbonate, magnesium, or possibly double magnesium-calcium carbonate and uranium bound in the form of uraninite. The methods described in this way cannot be used if the ore contains, in addition to a high content of carbonates, mineral forms of uranium that are moderately difficult to leach.

An example of such a medium-leachable carbonate ore K is an ore containing 5-15% MgCO^.

. CaCO, and uranium bound to various forms of titanium oxide of complicated composition. The uranium ^J 3 recovery during leaching is only 47 to 49% for such an ore for a residual H ₂ SO ₄ concentration of 5-20 kg/m 3 . When the residual H ₂ SO concentration is increased, the uranium leaching recovery in the mash increases significantly in the area of a residual H ₂ SO^ concentration of 100 kg/m ³ . The uranium recovery for residual concentrations of 100 to

190 kg/m ³ is 88-91 i. With further increase in the concentration of free residual H ₂ SO ₄ in the leached mash, the uranium recovery increases only minimally. For a residual concentration of H ₂ SC> _4,400 kg/m ³ , the uranium recovery of medium-leachable carbonate-type ore increases to only 93%. This distinguishes these ores from the difficult-leachable uranium ores of the A-aluminosilicate type.

During the leaching of these medium leachable uranium ores of the carbonate type, it was observed that a high initial concentration of H ₂ SO ₄ , e.g. 200 kg/μι and a residual concentration of H ₂ SO ₄ below 100 kg/m ³ in this ore causes a part of the leached uranium to be re-deposited towards the end of the leaching in the form of newly formed gel hydrated oxides of complicated composition U-Zr-Ti, which partly form shells of ore grains and thus prevent the action of the leaching agent. For efficient uranium leaching, the optimal residual concentration of H 2 SO 4 for such an ore is in the range of 100-200 kg/m ³ . Separate hydrometallurgical processing of the above medium leachable uranium ore of the carbonate type by an acidic method is not very economical due to the high reaction consumption of H 2 SO ₄ in the leaching (0.2 to 0.3 kg H ₂ SO ₄ ^{per 3} ^9 of ore).

The above-mentioned shortcomings are eliminated by the method of neutralizing residual acid according to the invention, the essence of which lies in the fact that the residual mash after leaching of difficultly leachable aluminosilicate-type ores is mixed in stirred reactors with ground and thickened medium-leachable uranium ore of carbonate type in a ratio according to the neutralization capacity of the medium-leachable uranium ore of carbonate type, the mixed mash is mined until the content of free H ₂ SO ₄ in the liquid phase is reduced to 50-250 kg/m ³ . The free H^SO^ contained in the mash after this neutralization method can be further neutralized to the required value of 5-20 kg of free H ₂ SO ₄ in 1 m ³ of the liquid phase by any of the known methods mentioned above.

The neutralization method according to the invention solves the problem of high residual concentration of H ₂ SO ₄ in the waste mash after leaching of difficult-to-leach ores, especially uranium aluminosilicate type, by using it for leaching of medium-to-leachable uranium ore of carbonate type. The method allows to reduce the consumption of lime for neutralization while simultaneously valuing the residual H 2 SO 4 during leaching of difficult-to-leach ores. The use of residual H 2 SO 4 for leaching of medium-to-leachable ore of carbonate type also solves the problem of processing this ore, which has so far been processed only with low yield and economically unprofitable.

Example

Rinut A is a suspension after leaching of difficult-to-leach uranium ore of the aluminosilicate type with a residual sulfuric acid concentration in the liquid phase C _{u cr} . = 335 kg/m .

^H 2 ^bU 4

Rinut K is a suspension of medium leachable uranium ore of carbonate type, ground to a maximum particle size of 0.15 mm and concentrated to a solids concentration of 50%. The typical composition of medium leachable uranium ore of carbonate type is

60.2% SiO ₂ , 14.90% Al ₂ O ₃ , 2.80% MgO, 4.90% CaO, 6.75% CO ₂ , 0.55% TiO ₂ and 0.1% Zr° ₂ .

3 3

In a stirred reactor, 1 m of mash A is mixed with 0.69 m of mash K. The mixture produces 1.69 m of mash with an initial sulfuric acid concentration of C„ _cn = 200 kg/m in the liquid phase. The mixed mash _of ^H 2 ^bU 4 is mined with constant stirring at a temperature of 85 C for 6 hours, during which the residual uranium is neutralized and leached from the medium-leachable uranium ore with a yield of 90.0%.

The reaction consumption under these conditions is 200 kg per 1,000 kg of ore. The output mash with a residual sulfuric acid concentration in the liquid phase C _u = 125 kg/m ³ is already suitable for further processing in a known manner. In the described example ^, 1,000 kg of medium-leaching uranium ore of ^the carbonate type replaces 80 kg of CaO used for neutralization.

Claims (1)

SUBJECT OF THE INVENTION Process for neutralizing residual sulfuric acid in leaching of hardly leachable ores, in particular uranium alumosilicate type, characterized in that the residual mash after leaching is mixed in stirred reactors with ground and concentrated medium leachable uranium ore of carbonate in proportion to the free H ₂ SO 4 concentration in the liquid phase After the leaching of the hardly leachable uranium ores of the alumosilicate type and, according to the neutralizing ability of the medium leachable uranium ore of the carbonate type, the resulting mixed mash is reduced until the free I 2 SO 4 content in the liquid phase drops to 50-250 kg / m ³ .