The method of extraction of rare earth and radioactive metals from oxidized technologically resistant materials

 

(57) Abstract:

The invention relates to the field oxide technologically resistant materials, in particular to the processing of ash waste from coal burning, with the purpose of extraction of rare earth and radioactive metals. From the ash wastes and sulfuric acid are produced sludge is then subjected to processing in the cathode area of the cell under conditions that support the selection at the cathode hydrogen. In the process prepare a slurry with a ratio of T : W = 1 (5 - 10) and using a sulfuric acid concentration of 50 to 30 g/l, electroisolative conducted within a 0.25 - 1.5 h at a cathode current density of 0.5 and 5 mA/cm2and a temperature of 18 - 80oC. the Invention improves the efficiency of the process, to simplify the instrumentation and to reduce the retrieval time. 3 C.p. f-crystals, 5 tab., 3 Il.

The invention relates to the field oxide technologically resistant materials, in particular, to the processing of ash waste from coal burning to extract rare earth and radioactive metals.

One of the distinguishing features of such waste is the low content redkozemel, iron and calcium are formed at high temperatures (1200 - 1700oC), and, therefore, chemically passive. The above features lead to the extraction of rare earth and radioactive metals with high enough, high output, you must use special techniques: large processing time, increased temperatures, increased concentrations of reagents for processing or special equipment.

The known method [1] hydrometallurgical extraction of rare metals from technologically resistant materials. In this way a matrix of refractory raw materials are crushed, placed in a sealed vessel containing a solution of a halogen acid, nitrous acid and complexing agents for rare metals. In the vessel from the outside serves oxygen. The process is conducted at a certain pH value of the reaction mixture, the pressure and the half-wave potential for the recovery of oxidants sufficient time, which is chosen from the condition of opening of the matrix raw material for maximum oxidation and extraction of rare metals from the matrix and education of the mother liquor, containing dissolved complexes and oxides of rare metals. The extraction of rare metals from the mother liquor about the crystals from the matrix it is necessary to control such process parameters as an indicator of the acidity, the potential recovery of oxidants and pressure. For such control requires complex and expensive equipment, which significantly reduces the economic effect of the implementation of this method, especially for the processing of such poor materials rare metals, in particular, rare earth and radioactive as ash wastes from the combustion of coal.

The known method and device for the extraction of precious metals [2] of the poor and refractory raw materials and waste mining companies, which have nedosvechennye metals. In this way to increase the completeness of extraction of valuable components and effectively separating them from the surrounding rocks crushed material together with the electrolyte in the form of suspension is treated in the electrode unit under the influence of an electric direct current and ultrasonic fields, resulting in leaching of the host rocks and the release of particles useful component of these revenues to the electrode unit, the suspension undergoes additional processing in the ultrasonic field, where the solid material is subjected to mechanical and cavitational destruction with simultaneous activiations characteristics of electrochemical reactions at the electrode unit, treatment of the suspension is carried out at a pressure of 5-10 kg/cm2.

The above-described techniques, including ultrasonic treatment and/or working under excessive pressure need not be applied in the extraction of rare earth and radioactive metals from oxidized technologically resistant materials, in particular, ash waste, as compounds of these metals are chemically more active than color. In addition, ultrasonic treatment leads to additional wear and tear of the equipment, which significantly reduces the economic effect of the implementation of this method.

Closest to the claimed is a method of separation of scandium from the evils of coal (b, kites and other Scandium. M.: Metallurgy, 1987. S. 150-151), based on acid leaching. After alkaline intrusion ash, coal and processing of the obtained water solution of 18% hydrochloric acid is conducted subsequent ion concentration and deposition in the form of hydroxides. How, in particular, is carried out as follows.

The ash of brown coal containing, %: Sc2O30,012; SiO265,8; Al2O318,8; Fe2O312,1; MgO 1.0; TiO20,88; Ca0 to 0.7, scry is W = 1: 5 separates the bulk aluminum and part of the silicon. The residue contains, %: Sc2O30,011 (90% original); Na2O 4,2; Al2O32,55; MgO 1,40; TiO21,22; CaO 0,95; base - SiO2and Fe2O3. The next operation is the handling of the suspension of balance of CO2. In carbonate solution together with scandium pass the basic quantities of calcium and magnesium, as well as Ti, Al, Ga, Fe, Si, si, Y and REE. The solution is acidified with sulfuric acid to pH = 1 and carry out ion-exchange preconcentration of scandium on phosphorylated cellulose. Desorbed scandium 10% solution of ammonium carbonate. After acidification of the resulting solution with hydrochloric acid and boiling precipitated hydroxides in an aqueous solution of ammonia. In the calcined oxide of scandium is contained 94,4% of the basic substance, 3% TiO2, tenths of a percentage Y2O3and SiO2. The output of scandium is 64%.

The main disadvantage of this method is the operation of pre-sintering of ash with alkali to separate the aluminum from fly ash. This leads to the necessity to use additional equipment - kilns for fusing, as well as to additional consumption rather expensive reagent alkali. In addition, the degree of extraction of scandium in this way is sufficiently low output scandium sostegni materials, but require different measuring devices for monitoring process parameters, special devices baselaceltli working under excessive pressure and/or ultrasonic field, and in some cases, and preliminary operations on opening ash, in particular, by fusing with caustic.

The present invention is the creation of a more economical and simple in hardware performance, but effective method for leaching of rare earth and radioactive metals from oxidized technologically resistant materials, in particular, ash waste produced by the combustion of coal, allowing to extract the above-mentioned metals operations pre-opening ash in a short processing time.

This technical result is achieved in that in the method of extraction of radioactive and rare-earth metals from oxidized technologically resistant materials, including acid leaching, the last (leaching) is carried out by preparing slurry of ash and slag waste, taken as a source of raw materials, and solution of sulfuric acid and its processing at the cathode of low hydrogen evolution overpotential at a constant paramesh what about it was installed, what if this begins the most effective selection of rare and radioactive metals from the matrix, that allows to do a fairly simple equipment without losing the efficiency of leaching. This effect, as suggested by the authors, associated with the recovery of oxides of rare earth metals contained in the raw materials, eye-catching and/or adsorbed on the cathode, hydrogen is one of the mechanisms [3]:

mechanism 1 - e mechanism is a direct discharge of solid particles: for oxides (where Mn+- or radioactive rare earth metal)

[Mn++ (n/2)O2-] + ne + (n/2)H2+= M + (n/2)-< / BR>
The electron transfer occurs between the electrolyte and insoluble substance.

the mechanism 11 is involved in the electron transfer intermediate substance (X) formed on the electrode during the process:

for oxides (where Mn+- or radioactive rare earth metal, X is eye-catching and/or adsorbed on the cathode hydrogen)

[Mn++(n/2)O2-]+nX +nH+= M+nX-+(n/2) H2O

The best results on leaching achieved on metals with a low hydrogen evolution overpotential, for example of platinum, copper, Nickel, titanium and others; naillon affects the mechanism of hydrogen, best known from the electrode material.

In the process prepare a slurry with a ratio of T:W = 1: (5-10) and use a sulfuric acid concentration of 50-300 g/l, electroisolative conducted within a 0.25 - 1.5 h at a cathode current density of 0.5 to 5.0 mA/cm2and temperature 18-80oC.

The purpose of concentration of rare earth and radioactive metals and improve access to the sulfuric acid solution, the ash can be pre-prepared by treating an alkaline solution under the following conditions:del= 150 - 250 g/l, T = 80-90oC = 2 -3 h, T:W = 1:5. Such processing leads to the destruction of the structure of the ash particles and the concentration of rare earth and radioactive elements and, consequently, to reduce the volume of ash for electrochemical leaching and improve the economic performance of the process.

If necessary, the maximum concentration of rare earth and radioactive metals from pre-ash, you can extract almost all of the silicon and aluminum, ash sintering with sodium carbonate and decomposing the obtained sintered alkaline solutions, and then leaching of rare earth metals by the method proposed by the authors of this is logicheskie resistant materials, containing accommodated in the housing of the electrode unit, equipped with a stirrer to maintain the particles of raw material in suspended form and is surrounded by the aperture of the anode or the anode without the diaphragm and the cathode, preferably made of titanium, copper, platinum, Nickel, cobalt, chromium or their alloys. The cathode may be made cylindrical or in the form of several rows of spirals surrounding the anode. The anode may be made hollow to accommodate axis mechanical stirrer. The mixer can also be carried out with a magnetic drive.

The method of extraction of rare earth and radioactive metals from oxidized technologically resistant materials is illustrated by drawings, where:

in Fig. 1 is a diagram of electrophysiologically laboratory performance (magnetic stirrer) (top and side view),

in Fig. 2 is a diagram of electrophysiologically with a mechanical stirrer and a hollow anode (top and side view);

in Fig. 3 is a diagram of electrophysiologically spiral hollow cathode and the anode (top and side view).

Device for extraction of rare earth metals from oxidized technologically resistant materials and device for its implementation contains an electrode unit including an anode 1, done the ne and anodic reactions or the electrode without diaphragm, and the cathode 3 made of copper, titanium, platinum, Nickel, cobalt, chromium or their alloys and having the form of a cylinder (Fig. 1,2) or several rows of spirals surrounding the anode (Fig. 3). The device is equipped with a stirrer 4, with block 5 magnetic drive agitators (Fig. 1) or driven by mechanical means with an axis passing through the hollow anode 1 (Fig. 2, 3). The electrode unit placed in the housing 6 that supports the desired temperature (Fig. 1,2,3).

The device operates as follows: in the electrode space pour the pulp to the required temperature, prepared in the ratio T:W = 1: (5-10), connect the electrodes to the DC source and include drive agitators. The process is carried out at the parameters (temperature, current density, acid concentration and time) indicated in the examples to achieve the necessary degree of leaching. After the treatment the pulp is separated by filtration on a solution and residue. The extraction of rare earth and radioactive metals from the resulting solution can be conducted by known methods.

The authors have studied the dependence of the extraction of rare earth metals (for example, cerium) from ash-slag wastes from the combustion of coal from CLASS="ptx2">

The invention is illustrated with specific examples of processing of oxidized technologically resistant materials, in particular, for example, fly ash Ekibastuz coal.

All experiments took the required weight of ash was placed in a pre-thermostated solution of sulfuric acid and included DC. The required current density exhibited by the milliammeter, the solution temperature with a thermostat. As the cathode in the present examples were used copper foil as the anode lead. After treatment, the suspension was filtered under vacuum to increase the rate of filtration. Source cerium content in the ash was 0,019%. The cerium content in the solution was determined by a spectrophotometric method.

Since the chemical properties of actinides are similar to the properties of the lanthanides, in conditions of maximum REE extraction were carried out determination of uranium and thorium, which are present in the ash in the amount of 3 and 10 g/t, respectively.

Example 1.

To study the influence of the concentration of sulfuric acid leaching of cerium processing was conducted under the conditions shown in the table. 1.

Thus, the increase in con the spine of the environment. The decrease in the concentration of below 50 g/l reduces the degree of leaching. The content of radioactive metals in solution at a concentration of sulfuric acid 100 g/l is 910-5g/l for uranium and 2,210-4g/l for thorium, which corresponds to the degree of extraction 30 and 32%, respectively.

Example 2.

To study the influence of current density on the leaching of cerium from ash treatment was carried out with the parameters given in table. 2.

Thus, the reduction current density of 0.25 mA/cm2reduces the degree of leaching of up to 0.2% without current. The increase in current density of 5.0 mA/cm2does not increase the degree of leaching, but increases power consumption. The content of radioactive metals in solution at a cathode current density of 5.0 mA/cm2is 9,610-5g/l for uranium and 2,310-4g/l for thorium, which corresponds to the degree of extraction 32, and 33%, respectively.

Example 3.

To study the effect of temperature on the leaching of cerium processing was conducted under the conditions shown in the table. 3.

Thus, the temperature rise of more than 80oC will lead to the complication of the apparatus due to significant evaporation process is neigh radioactive metals in solution at a temperature of 80oC is 2,010-4g/l for uranium and 5,110-4g/l for thorium, which corresponds to the degree of extraction of 68 and 73%, respectively.

Example 4. To study the effect of time on the leaching of cerium processing was conducted under the conditions shown in the table. 4.

Thus, the increase in processing time over 1.5 h will only slightly increase the degree of leaching of cerium, and reduce processing time to a high enough degree of leaching, i.e. the loss of a significant amount of cerium with waste ash. The content of radioactive metals in solution when the processing time of 1.5 h at 2,810-4g/l for uranium and 6,710-4g/l for thorium, which corresponds to the degree of extraction 93 and 94%, respectively.

Example 5.

The purpose of concentration of rare-earth metals in the ash, as well as improving the access of reagents to the oxides of rare earth metals ash was pre-treated with caustic soda under optimum conditions established experimentally:del= 250 g/l, T = 855oC = 3 h, T:W = 1: 5. After processing the obtained suspension was filtered under vacuum, ash was dried in a drying Cabinet at a temperature of 80 -90oC. Test ash SRM the ILO being 0.036%.

Processing was conducted under the conditions shown in the table. 5.

Thus, the preliminary obestsenivaya ash reduces the electrochemical treatment of ash, at the same time, without compromising the degree of leaching. It can be expected that additional extraction of other components, such as aluminum, will also lead to the concentration of REE and does not worsen the degree of extraction. Increasing the processing time more than 1.0 h will only slightly increase the degree of leaching of cerium, but will cost the heated suspension. The content of radioactive metals in solution when the processing time of 1.0 h is 3,010-4g/l for uranium and 6,910-4g/l for thorium, which corresponds to the degree of extraction of 99 and 99%, respectively.

The list of used literature

1. RF patent N 2114196. IPC: 22 IN 3/04. Method for the hydrometallurgical extraction of rare metals from technologically resistant material.

2. Application 97115398/02 EN, IPC 6 C 22 B 11/00, C 25 C 1/12, 7/00, B N 20, 20.07.99.

3. Dausheva M. R. Sangna O. A. Behavior of the suspensions trudnorastvorimykh compounds on the electrode. // USP. 1973. So-42, vol. 2. C. 323-342.

1. The method of extraction of rare earth and radioactive metals from oxidized technologically advanced portolani slurry of ash and slag waste, taken as a source of raw materials, and solution of sulfuric acid and its processing at the cathode of low hydrogen evolution overpotential with constant stirring.

2. The method according to p. 1, characterized in that the prepared slurry at a ratio of T : W = 1 : (5-10) and use a sulfuric acid concentration of 50-300 g/l, the leaching is carried out for 0.5-1.5 h at a cathode current density of 0.5 to 5.0 mA/cm2and temperature 18-80oC.

3. The method according to p. 1, characterized in that saleslady waste pre-treated with an alkaline solution under the following conditions: concentration of 150-250 g/l, a temperature of 80-90oC, time of 2.0 to 3.0 h and T : W = 1 : 5.

4. The method according to any of paragraphs.1-3, characterized in that the cathode is made of titanium, copper, platinum, Nickel, cobalt, chromium or their alloys.

 

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