Scale inhibitor and application thereof in in-situ leaching uranium mining

Abstract

The invention discloses a scale inhibitor and application of the scale inhibitor in in-situ leaching uranium mining, and relates to the technical field of uranium mining, a mixed solution containing 2-phosphate-1, 2, 4-tricarboxylic acid butane (PBTCA) and polymaleic acid (HPMA) with a certain concentration, CO2 and O2 are injected into an ore bed together along with liquid injection holes, efficient leaching of uranium by CO2 and O2 systems in a high-hardness underground water environment is achieved, and the uranium leaching efficiency is improved. By means of dispersion, surface tension reduction, chelation solubilization and the like, production of carbonate series precipitates and accumulation of scales are effectively prevented, and compared with a single CO2 and O2 in-situ leaching uranium mining technology without adding a reagent, the uranium extraction recovery rate is increased by 2-3%, the extraction efficiency is increased by 3-8%, and the mine blocking frequency is reduced by 80%.

Description

Technical Field

[0001] The present invention relates to the technical field of uranium extraction, and particularly to a scale inhibitor and its application in in-situ leaching of uranium. Background Art

[0002] Neutral in-situ uranium leaching technology generally uses a mixed gas of carbon dioxide (CO2) and oxygen (O2) as the core leaching agent. CO2 dissolves in groundwater to form carbonic acid, providing carbonate ions to react with uranium minerals to form soluble uranyl carbonate complexes (such as UO2(CO3)3 4- ). O2 acts as an oxidant to oxidize tetravalent uranium (U 4+ , insoluble) to hexavalent uranium (U 6+ , soluble), improving the leaching efficiency of uranium. As an effective water treatment chemical, scale inhibitors are widely used in water systems in industrial production and have been well applied in fields such as water treatment, oil extraction, and underground mineral leaching, aiming to prevent the deposition and scaling of minerals in water. With the acceleration of the industrialization process and the increasing tension of water resources, the research on scale inhibitors has received more and more attention.

[0003] The mining and leaching process of uranium ore involves complex interactions with water. Especially in sandstone-type uranium deposits, due to high water content and large porosity of the ore layer, the ore layer is often prone to scaling and plugging problems. At this time, as a chemical additive, scale inhibitors can effectively prevent the ore layer from scaling and improve the permeability of the ore layer, thereby improving the stability and continuity of mining. The application of scale inhibitors in oil fields has effectively prevented the formation of scale deposits such as calcium carbonate, but there is less research on their application in uranium mines. Currently, neutral in-situ uranium leaching mines in China are all facing production problems such as mine shaft blockage and heavy well washing work.

[0004] However, scale inhibitors have not been applied in neutral in-situ uranium leaching at present. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art, and to provide a scale inhibitor and its application in in-situ leaching of uranium.

[0006] The technical solution of the present invention is as follows:

[0007] A scale inhibitor, comprising 2-phosphono-1,2,4-tricarboxylic acid butane and polymaleic acid.

[0008] Preferably, the molar ratio of 2-phosphono-1,2,4-tricarboxylic acid butane to polymaleic acid is 2-4:1.

[0009] Preferably, the mass ratio of 2-phosphono-1,2,4-tricarboxylic acid butane to polymaleic acid is 3:1.

[0010] The present invention also discloses an application of the scale inhibitor as described above in in-situ leaching of uranium.

[0011] Preferably, a mixed solution of 2-phosphono-1, 2, 4-tricarboxylic acid butane and polymaleic acid, and CO2 and O2 are injected into the ore layer together with the injection hole.

[0012] Preferably, the concentration of the mixed solution is 100-300 mg / L.

[0013] Preferably, the concentration of the mixed solution is 200 mg / L.

[0014] Preferably, during in-situ leaching of uranium, the CO2 and O2 are injected into the ore layer in equal volume through the injection hole, so that the pH of the leaching solution is 6.0-8.5. When the cumulative concentration of 2-phosphono-1, 2, 4-tricarboxylic acid butane and polymaleic acid in the mixed solution continuously increases and exceeds 500 mg / l, the addition of the mixed solution is stopped.

[0015] The beneficial effects of the present invention are as follows: The present invention provides a composite scale inhibitor composed of 2-phosphono-1, 2, 4-tricarboxylic acid butane (PBTCA) and polymaleic acid (HPMA), and determines that the optimal use concentration of the scale inhibitor is 200 mg / L. Under this condition, the scale inhibition efficiency can reach more than 80%. The function of PBTCA is to form soluble complexes with calcium, magnesium and other ions, inhibit the crystallization process of scale-forming substances, and thus reduce deposition. And HPMA is suitable for alkaline water quality or compound use with other drugs. HPMA mainly disperses mineral particles and reduces their adhesion on the surface of equipment. The complementarity of PBTCA and HPMA in chemical structure enables them to enhance the scale inhibition effect on calcium carbonate. The combination of PBTCA and HPMA can reduce the surface energy of ions in water, making it more difficult for ions to aggregate and form solid precipitates. The carboxyl group of PBTCA can be partially dissociated in water to form negative charges, and the carboxyl group of HPMA can also form negative charges. When the two meet, ionic bonds can be formed between the negatively charged carboxyl groups, further enhancing their interaction.

[0016] In addition, in addition to the dispersion and scale inhibition effects of 2-phosphono-1, 2, 4-tricarboxylic acid butane (PBTCA) and polymaleic acid (HPMA), there is also the effect of reducing the surface tension of the micropores of the ore by the surfactant, and its chemical action concentration is also at the level of 200-500 mg / L. Under this condition, due to the reduction of surface tension, the hexavalent uranyl ions in the ore will be able to combine more fully with calcium carbonate to form the complex anion of uranyl carbonate, so the dissolution and leaching rate of uranium will be increased. In addition, due to the reduction of surface tension, the uranyl ions in some micropores that could not originally contact the solution can also be dissolved smoothly, increasing the overall leaching rate (recovery rate) of uranium. Description of the Drawings

[0017] Figure 1 SEM image of CaCO3 crystals without scale inhibitor added;

[0018] Figure 2 SEM image of CaCO3 crystals with scale inhibitor added;

[0019] Figure 3 Effect of scale inhibitor on the surface potential of minerals;

[0020] Figure 4 Scale inhibition rates of six scale inhibitors;

[0021] Figure 5 Curve of uranium leaching rate varying with time;

[0022] Figure 6 Curve of calcium ion concentration in leaching solution varying with time;

[0023] Figure 7 Curve of daily flow rate of leaching solution. Detailed implementation mode

[0024] The present invention provides a scale inhibitor, which comprises 2-phosphono-1,2,4-tricarboxylic acid butane (PBTCA) and polymaleic acid (HPMA);

[0025] The mass ratio of the PBTCA to the HPMA is (2-4):1.

[0026] Further, the mass ratio of the PBTCA to the HPMA is 3:1.

[0027] The present invention also discloses an application of the scale inhibitor as described above in in-situ leaching of uranium.

[0028] Preferably, a mixed solution of 2-phosphono-1,2,4-tricarboxylic acid butane and polymaleic acid, CO2 and O2 are injected into the ore layer together through the injection hole. Specifically, CO2 and O2 are mixed in an equal volume ratio and then added. The concentrations of carbon dioxide and oxygen in the water are detected to be 100-300 mg / L, and the gas injection pressure is between 0.1-0.8 Mpa. The specific control of CO2 during the uranium extraction process is monitored by the pH value. As long as the pH value of the leaching solution (extracted from the pumping hole) is maintained between 6.0-8.5, if it is found that the pH value continues to rise, the supply of CO2 is increased; if it is found that the pH continues to drop, the supply of CO2 is reduced or even shut down. For O2, the EH value of the solution is monitored to be 560 mv > EH > 400 mv. If it is lower than this value, mixed oxygen needs to be injected. If it is higher than 560 mv, no oxygen doping is required.

[0029] Preferably, the concentration of the mixed solution is 100-300 mg / L.

[0030] Preferably, the concentration of the mixed solution is 200 mg / L.

[0031] Therefore, the present invention applies a scale inhibitor in the in-situ leaching uranium technology. Using carbon dioxide, oxygen, PBTCA, and HPMA as the feed liquid for in-situ leaching uranium as the leaching agent can improve the uranium extraction efficiency and make the uranium extraction production continuous.

[0032] In the present invention, unless otherwise specified, all raw material components are commercially available products well-known to those skilled in the art.

[0033] In summary, the present invention selects two chemical reagents, PBTCA and HPMA, as scale inhibitors for the following main reasons: (1) The two chemical reagents, PBTCA and HPMA, have a scale inhibition effect of complexing and solubilizing the precipitation of calcium, iron, aluminum, etc. in water bodies, as well as dispersing and shielding. Therefore, their selection can prevent the formation of precipitates such as calcium carbonate, iron hydroxide, and aluminum hydroxide when a large amount of carbon dioxide is added during in-situ leaching of uranium, or avoid the formation of large particle precipitate crystals due to the dispersion effect, and the accumulation of a large amount of precipitation to form a scale body that is difficult to peel off. (2) When the concentration of the two chemical reagents, PBTCA and HPMA, is 100 - 500 mg / L, in addition to having a scale inhibition and dispersion effect, they also have the function of reducing the surface tension of the micropores of the ore. By reducing the surface tension of the micropores, the pores that were originally blocked due to excessive surface tension can become unblocked, so there is an effect of expanding the contact surface area of the reagent and increasing permeability. (3) The use environment of the two chemical reagents is suitable for a nearly neutral environment with a pH between 6.5 and 8 (the environment of in-situ leaching of uranium). Moreover, in the presence of the two chemical reagents, it has a promoting effect on the subsequent function of ion exchange resin to adsorb and separate uranium, improving the working adsorption capacity and adsorption efficiency of the resin. (4) The two chemical reagents, PBTCA and HPMA, are not continuously added and consumed. Since the water used for in-situ leaching of uranium is recycled internally without discharge, in the process, as long as the cumulative values of PBTCA and HPMA in the groundwater are controlled, when the concentration in the groundwater continues to rise and exceeds 500 mg / L, the addition of these two chemical reagents is stopped.

[0034] The present invention does not have any special limitations on the preparation method of the scale inhibitor, and it can be mixed by using a physical mixing process well-known to those skilled in the art.

[0035] The present invention also provides the application of the scale inhibitor described in the above technical solution in removing the scale generated by in-situ leaching of uranium.

[0036] In the present invention, the in-situ leaching of uranium is preferably in-situ leaching of uranium with CO2 and O2.

[0037] In the present invention, the scale inhibitor preferably inhibits scale in the form of a scale inhibitor solution;

[0038] The mass concentration of the scale inhibitor solution is preferably 200 mg / L.

[0039] In the present invention, the composition of the scale preferably includes calcium carbonate.

[0040] In the present invention, the concentration ratio of the scale to the scale inhibitor solution is preferably 1:1, and the scale inhibition temperature is preferably room temperature (25 - 35 °C).

[0041] The scale inhibitor and its application provided by the present invention will be described in detail below with reference to the examples, but they should not be construed as limiting the scope of protection of the present invention.

[0042] Examples 1 - 19

[0043] The mass concentration ratios of PBTCA and HPMA in the scale inhibitor are shown in Table 1:

[0044] Table 1 Concentration ratios of PBTCA and HPMA in the scale inhibitor described in Examples 1 - 19

[0045]

[0046]

[0047] Comparative Examples 1 - 6

[0048] The types of scale inhibitors in Comparative Examples 1 - 6 are shown in Table 2:

[0049] Table 2 Types of scale inhibitors described in Comparative Examples 1 - 6

[0050] Comparative example Scale inhibitor type Comparative example 1 Poly maleic acid (HPMA) Comparative example 2 2-Phosphono-1,2,4-tricarboxylic acid butane (PBTCA) Comparative example 3 Poly aspartic acid (PASP) Comparative example 4 Amino trimethylene phosphonic acid (ATMP) Comparative example 5 Sodium polyether sulfonate (PESA) Comparative example 6 Hydroxyethylidene diphosphonic acid (HEDP)

[0051] Test Example 1

[0052] The scale inhibitors of Examples 1 - 19 and Comparative Examples 1 - 6 were prepared into scale inhibitor solutions with a mass concentration of 200 mg / L;

[0053] This test example is for the determination of the scale inhibition rate of calcium carbonate. The scale inhibition rate determination method uses the static deposition method. 0.5 g of calcium chloride, 0.25 g of sodium carbonate and a certain concentration of scale inhibitor were prepared into a 250 mL, 200 mg / L solution. First, calcium chloride was added, then the scale inhibitor was added, and finally sodium carbonate was added, followed by volume fixation and shaking in a volumetric flask. After standing, 1 - 5 mL of the supernatant was taken and titrated with 0.005 mol / L EDTA. The measured data was recorded as C2. Two groups of control groups were set up in the experiment. One group added the same concentration of Ca 2+ , but did not add CO3 2-The ion and scale inhibitor were kept unchanged, and the data obtained by EDTA titration was recorded as C; in another group, no scale inhibitor was added, and the other steps were kept unchanged, and the data obtained by EDTA titration was recorded as C1. The calculation formula for CaCO3 scale inhibition rate is:

[0054]

[0055] Where, η represents the CaCO3 scale inhibition rate;

[0056] C means only Ca is added to the solution 2+ concentration;

[0057] C1 represents the Ca content of the solution without adding antiscalant 2+ concentration,

[0058] C2 indicates the addition of scale inhibitor and CO3 2- Ca in the solution 2+ concentration.

[0059] The scale was characterized by BET and scanning electron microscopy; the surface potential of uranium ore was analyzed by Zeta potential titrator.

[0060] The surface potential of uranium ore was analyzed using a Zeta potential titrator. 0.2 g of uranium ore was weighed, one group was titrated with a composite scale inhibitor, and the other group was titrated with deionized water. The results are as follows: Figure 3 As shown. It can be found that the ore surface potential decreases with increasing pH. In the titration group without the addition of scale inhibitor, the ore surface is positively charged when the pH is less than 4, and negatively charged when the pH is greater than 4, with a maximum negative potential of -35mV. In the titration group with the addition of scale inhibitor, the ore surface potential is negatively charged within the pH range of 2-8, with the overall potential shifting downward, and the maximum negative potential value is -60mV. This proves that after the addition of scale inhibitor, the electronegativity of the ore surface is enhanced, which improves the affinity of the ore surface for the leaching agent, accelerates the liquid film diffusion, and improves the uranium leaching efficiency.

[0061] The scale residue after the scale inhibitor of Example 5 was used for scale inhibition was subjected to SEM test. The test results are as follows: Figure 1 、 Figure 2 As shown by Figure 1 It can be seen that when no scale inhibitor is added, the calcium carbonate crystals present a spherical structure, which is composed of irregular spherical particles and has a relatively rough surface. After magnification, it can be seen that it is composed of many smaller round particles, which are tightly aggregated to form a larger spherical structure. Figure 2 It can be seen that after adding the scale inhibitor, the surface of the calcium carbonate crystals becomes flatter and no longer spherical. When magnified, it can be seen that the surface has more small pores and has become a porous structure.

[0062] Figure 4The column chart of the scale inhibition rate of the scale inhibitors described in Comparative Examples 1-6, from Figure 4 it can be seen that the scale inhibitor of polymaleic acid (HPMA) in Comparative Example 1 has the best scale inhibition efficiency, and the scale inhibition rate reaches 88.9%. Among them, the scale inhibition efficiencies of 2-phosphono-1,2,4-tricarboxylic acid butane (PBTCA), polyaspartic acid (PASP), aminotrimethyl phosphite (ATMP), polyether sulfonate (PESA), and amino triacetic acid hydroxyethyl phosphite (HEDP) scale inhibitors in Comparative Examples 2-6 are 80.09%, 75.71%, 79.89%, 21.41%, and 17.69% respectively.

[0063] Table 3 Scale inhibition rate test results of Examples 1-19

[0064]

[0065]

[0066] As can be seen from Table 3, when the total concentration of PBTCA and HPMA is 200 mg / L and the compounding ratio is 1:1, the scale inhibition rate reaches 85.72%. When the content of PBTCA is increased and the content of HPMA is decreased, the scale inhibition rate increases with the increase of PBTCA; when the content of PBTCA is decreased and the content of HPMA is increased, the scale inhibition rate decreases from 85.72% to 70.45%. As the proportion of HPMA increases, the scale inhibition rate rebounds somewhat, but the upward trend is not obvious. Therefore, when PBTCA:HPMA = 3:1, the compound scale inhibition effect is the best, and the scale inhibition rate reaches the maximum of 95.26%. When the proportion of PBTCA is further increased, the scale inhibition rate begins to show a downward trend.

[0067] Judging from the change of scale inhibition rate, PBTCA plays a major role in the compound reagent. When the concentration of HPMA is fixed, the scale inhibition rate increases with the increase of PBTCA concentration, and the maximum scale inhibition rate is 94.9%. When the concentration of PBTCA is fixed, with the increase of the concentration of HPMA used, the scale inhibition rate also increases, but the growth effect is slow, and the maximum scale inhibition rate is 72.91%. This result may be due to the different main scale inhibition principles of the two. Although HPMA forms colloidal particles in water to wrap calcium ions in water, preventing the precipitation and crystallization of ions in water, and has good dispersion performance, it can effectively disperse solid particles in water to prevent them from aggregating into scale; when PBTCA contacts calcium ions in water, the phosphate group forms a complex with these ions through complexation, and PBTCA has a certain surface activity in water and can adsorb onto the solid surface to form a protective film to prevent the aggregation and deposition of solid particles in water. The similar functions of the two have a synergistic effect on stabilizing the precipitated ions in water. However, PBTCA inhibits scale mainly by the complexation reaction of its own groups with metal ions in water to prevent the precipitation of scale substances, while HPMA mainly relies on its own negative charge to disperse the scale particles in water to prevent the aggregation and growth of scale crystals. Insufficient concentration of PBTCA leads to a weakening of its complexation ability with metal ions and cannot cooperate well with HPMA to prevent the formation of scale substances; while when the concentration of HPMA is small, it can still chelate and disperse the metal ions and particles not captured by PBTCA to achieve a better scale inhibition effect. Therefore, when the total concentration of the scale inhibitor is 200 mg / L, the scale inhibition rate reaches the maximum when PBTCA:HPMA = 3:1.

[0068] Table 4 BET analysis - specific surface area results of scale

[0069]

[0070] Table 5 BET analysis - pore volume of scale

[0071]

[0072]

[0073] Table 6 BET analysis - pore diameter of scale

[0074]

[0075] As can be seen from Table 4-6, if the specific surface area of the calcium carbonate precipitation crystals after adding the scale inhibitor is significantly higher than that of the calcium carbonate precipitation crystals without the scale inhibitor, and the crystal pore diameter is smaller and the surface is smoother after adding the scale inhibitor, for the precipitation, the calcium carbonate precipitation after adding the scale inhibitor has better fluidity and is not easy to form a dense layer on the ore surface. By comparing the changes in the average pore diameter and total pore volume, it further shows that the crystal structure of the calcium carbonate precipitation after adding the scale inhibitor becomes loose and porous. The structure of the calcium carbonate precipitation without the scale inhibitor is relatively thick and the porosity is low, and the molecules are tightly aggregated together, while the changed structure may reduce its adhesion. Taking physical cleaning as an example, ultrasonic waves are more likely to shatter and peel off the crystals after adding the scale inhibitor, improving the operation efficiency.

[0076] Test Example 2

[0077] The test results of calcium ions in the solution containing equal volumes of carbon dioxide and oxygen and added with the solutions of Examples 1-19 are shown in Table 7.

[0078] Table 7 Test Results of Calcium Ions in the Solutions Containing Only Carbon Dioxide and Oxygen and Added with the Solutions of Examples 1-19

[0079]

[0080] It can be seen from Table 7 that pure carbon dioxide and oxygen dissolve in water to form carbonate and bicarbonate ions, and then calcium ions are added. After standing for a period of time, only a small part of calcium ions remain in the solution. After adding the scale inhibitor of the implementation example, with the different scale inhibition effects of the implementation example, the amount of calcium ion concentration contained in the solution is also different, but it is much larger than that of the implementation example without the scale inhibitor. Therefore, the addition of the scale inhibitor effectively inhibits the deposition of calcium ions, and the screening results of the scale inhibition effect are more accurate.

[0081] An experimental simulation evaluation was carried out for in-situ leaching of uranium combined with a scale inhibitor. The device was made of polytetrafluoroethylene, which is corrosion-resistant and high-pressure-resistant. The left liquid inlet is vertically upward and is connected to a peristaltic pump using a silica gel drainage tube; the right is the liquid outlet vertically downward and is connected to a leachate collection bottle using a silica gel drainage tube. In the middle, the crushed and mixed minerals were compacted and filled according to the density data of the original ore sample (uranium-containing) of the target ore deposit. The experiment was divided into two groups. One group of leaching agents contained only 1.5 g / L of bicarbonate ions, and the other group of leaching agents added a scale inhibitor at the same bicarbonate content. The cross-sectional area of the ore sample in the middle compacted section of the experimental device was 19.6 cm 2 , 3 cm wide, and the density was 1.65 g / cm 3, the total weight of the ore sample is 97.02 g. Both ends of the device are filled with liquid, and the liquid volume is 90 mL. The left side is the liquid inlet chamber. After the chamber is filled with the leaching solution by the peristaltic pump, it flows back into the leaching agent through the exhaust hole at the liquid inlet to generate a cycle, ensuring that the left liquid inlet chamber is always filled with the leaching solution. The leaching solution then naturally penetrates through the middle compaction section to the right liquid collection chamber. The leaching solution that naturally penetrates to the right is collected daily, and the calcium ion concentration and uranium content in the leaching solution are tested and recorded by ICP-OES.

[0082] The ion test results of in-situ leaching of uranium combined with scale inhibitor solution are shown in Table 8.

[0083] Table 8 Ion test results of in-situ leaching of uranium combined with scale inhibitor solution

[0084]

[0085]

[0086]

[0087] As can be seen from Table 8, when no scale inhibitor is added, the maximum calcium ion concentration in the leaching solution on the first day of uranium extraction is 6.117 mg / L, and the uranium ion concentration is 6.592 mg / L. After that, as the number of uranium extraction days increases, the concentrations of the two ions in the solution gradually decrease one by one. When the scale inhibitor is added, the maximum calcium ion concentration in the leaching solution on the first day of uranium extraction is 89.581 mg / L, and the uranium ion concentration is 7.35 mg / L. After that, as the number of uranium extraction days increases, the concentrations of the two ions in the solution also gradually decrease one by one. However, the addition of the scale inhibitor makes the calcium ion concentration in the leaching solution of in-situ leaching simulation for uranium extraction much greater than that of the simulation experimental group without the scale inhibitor, and there is also a certain increase in the uranium ion leaching concentration. The Ksp of CaCO3 is 4.8×10 -9 , and after calculation, when the Ca 2+ concentration is greater than 0.68 mg / L, there will be a precipitation risk. The experimental conditions contain a precipitation risk, and the addition of the scale inhibitor avoids this risk, enabling the effective leaching of uranium ions.

[0088] The test results of the leaching rate and scale inhibition rate of in-situ leaching of uranium combined with scale inhibitor are shown in Table 9.

[0089] Table 9 Test results of the leaching rate and scale inhibition rate of in-situ leaching of uranium combined with scale inhibitor

[0090]

[0091]

[0092] As can be seen from Table 9, the uranium leaching rate of the experimental group with scale inhibitor added increased faster than that of the experimental group without scale inhibitor added. The experimental group with scale inhibitor added was basically leached out on the 10th day of uranium extraction, while the experimental group without scale inhibitor added was basically leached out on the 15th day. This indicates that the addition of scale inhibitor shortens the uranium extraction cycle and makes the time to reach the maximum leaching efficiency of uranium ore shorter. In the later stage of leaching, when leaching the difficult-to-leach uranium, the leaching rate curve of the experimental group with scale inhibitor added was still greater than that of the blank group. The maximum uranium leaching rate of the experimental group without scale inhibitor added was more than 1% lower than that of the experimental group with scale inhibitor added. By comparing the differences in the calcium ion leaching concentration in the leaching solution and the changes in the uranium leaching rate, it can be shown that partial precipitation of calcium ions occurs in the ore, hindering the smooth leaching of uranium ions. Therefore, it can be shown that the addition of scale inhibitor can accelerate the leaching of uranium, increase the maximum uranium leaching rate, inhibit the formation of scale, and stabilize the ore permeability.

[0093] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A scale inhibitor, characterized in that, It includes 2-phosphono-1,2,4-tricarboxybutane and polymaleic acid.

2. The scale inhibitor according to claim 1, wherein The mass ratio of 2-phosphono-1,2,4-tricarboxybutane to polymaleic acid is 2 - 4:

1.

3. A scale inhibitor according to claim 1, characterized in that, The mass ratio of 2-phosphono-1,2,4-tricarboxybutane to polymaleic acid is 3:

1.

4. Application of a scale inhibitor as described in any one of claims 1 - 3 in in-situ leaching of uranium.

5. The application according to claim 4, characterized in that, Inject a mixed solution of 2-phosphono-1,2,4-tricarboxybutane and polymaleic acid, along with CO2 and O2, into the ore layer through the injection hole.

6. The application according to claim 5, wherein The concentration of the mixed solution is 100 - 300 mg / L.

7. The application according to claim 5, characterized in that, The concentration of the mixed solution is 200 mg / L.

8. The application according to claim 5, characterized in that, During in-situ leaching of uranium, CO2 and O2 are injected into the ore layer through the injection hole in equal volumes, so that the pH of the leaching solution is 6.0 - 8.

5. When the cumulative concentration of 2-phosphono-1,2,4-tricarboxybutane and polymaleic acid in the mixed solution continuously increases and exceeds 500 mg / l, stop adding the mixed solution.

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