Method for comprehensively recovering valuable elements from zirconium smelting waste residues

Abstract

The invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for comprehensively recovering valuable elements from zirconium smelting waste residues. The method sequentially comprises the steps of roasting pretreatment, hydrochloric acid leaching, iron extraction and reverse extraction, uranium extraction and reverse extraction, thorium extraction and reverse extraction and the like. According to the method, valuable elements in the radioactive complex multi-component waste residues are efficiently extracted and recycled, the uranium recycling rate is larger than 95%, the thorium recycling rate is larger than 90%, and the volume of the waste residue leaching residues can be reduced to 35% or below. Compared with the prior art, the method has the advantages that the valuable metal recovery rate is high, the reagent cost is low, and the whole-flow process water is recycled. The method provides an effective method for efficiently extracting and recycling valuable metal elements in the radioactive smelting waste slag.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrometallurgy, and particularly relates to a method for comprehensive recovery of valuable elements in zirconium smelting slag. BACKGROUND

[0002] Uranium is an important nuclear energy raw material. Zirconium has good corrosion resistance and plasticity. Zircon is a typical uranium associated resource, and uranium mainly exists in zircon, thorium stone and other minerals in the form of independent mineral phase (mainly crystal uranium ore) or isomorphism. In the process of producing zirconium oxychloride by using zircon sand as raw material by adopting the "one acid and one alkali" method, about 2 tons of radioactive waste slag are generated per ton of zirconium oxychloride. This radioactive waste slag has the characteristics of high radioactivity and large quantity, and the uranium content is as high as 0.3% to 0.6%. It is the most important environmental pollution link, and the enterprises invest a large amount of manpower, material resources and financial resources in its stacking, storage, supervision and environmental protection, thereby making the related enterprises bear a heavy burden.

[0003] There are relatively few studies on comprehensive recovery of valuable elements in zirconium smelting slag containing radioactive elements. Existing studies are mostly aimed at direct recovery and utilization of the slag or recovery of some elements in the slag. Liu Rongli et al. (Method for recovering radioactive elements from zirconium industrial waste slag, CN 110373556 A) proposed that the zirconium industrial waste slag is calcined with alkali, and the calcined slag is subjected to water immersion, filtration and washing to obtain filter residue containing uranium and thorium. The filter residue is dissolved with concentrated nitric acid, and then the method of extraction-washing impurity removal-stepwise back extraction is adopted. This method basically realizes the recovery of radioactive elements uranium and thorium in the waste slag, but the application of this method is limited by the technical problems such as high requirement for equipment, large amount of reagent used and high cost, incomplete recovery of valuable elements, and great difficulty in treatment and comprehensive utilization of three wastes. Liu Xianjian et al. (Method for high-efficiency recovery and utilization of zirconium and silicon in zirconium slag, CN 112591758 B) proposed that high-activity zirconium and silicon ash is obtained by crushing the zirconium slag, roll extrusion dewatering and calcination treatment; the high-activity zirconium and silicon ash is mixed with liquid alkali and heated to react, and the reaction mixture is subjected to cyclone separation to obtain centrifugal liquid and zirconium slurry; the zirconium slurry is dried and calcined to obtain zirconium silicate; the centrifugal liquid is mixed with microsilicon powder and stirred, and magnesium oxide is added to obtain a liquid ceramic mud slurry defoaming agent. This method does not consider the treatment and recovery of radioactive elements uranium and thorium in high smelting slag, and only considers the recovery and utilization of zirconium and silicon elements in the zirconium slag. The content of zirconium and silicon in the zirconium slag is relatively low, and the economic value is low. Liu Fei et al. (Study on zirconium recovery process from waste slag produced by alkali fusion decomposition of zircon sand, Study on zirconium recovery process from waste slag produced by alkali fusion decomposition of zircon sand, Rare Metals, 2017, 41(7): 831-836) studied the recovery of zirconium element in zirconium metallurgical slag mainly composed of silicic acid and un-decomposed zircon sand, and proposed that under the conditions of hydrochloric acid concentration of 2 mol·L -1 , acid immersion temperature of 50℃ and liquid-solid ratio of 5:1, the recovery rate of zircon which has been decomposed in the alkali fusion process can reach 62%.

[0004] Due to the low content of valuable elements, complex composition and difficult extraction of valuable elements in zirconium smelting slag, related research reports directly prepare mesoporous molecular sieves, cement concrete admixtures and other products by treating zirconium smelting slag. XU Lina et al. (Cement concrete admixture prepared from acid zirconium-silicon slag and its preparation method, CN 103159415B) proposed to prepare cement concrete admixture by calcining treatment of acid zirconium-silicon slag and adding activator. ZHAO Wei et al. (A method for preparing Zr-MSU mesoporous molecular sieve from industrial zirconium-containing waste slag and mesoporous molecular sieve, CN 109694079B) proposed a method for preparing Zr-MSU mesoporous molecular sieve with large pores, high doping amount and high catalytic performance, using industrial zirconium-containing waste slag as raw material and mixed solution of anionic surfactant and cationic surfactant as template agent. The related research reports do not consider the comprehensive recovery and utilization of valuable elements in zirconium slag, and do not consider the extraction and recovery of radioactive elements uranium and thorium. Since the content of zirconia in zirconium slag is about 10% and the content of silicon oxide is about 25%, the content is relatively low, considering the direct treatment and recovery of zirconium smelting slag or the extraction and recovery of part of the elements does not have development and application value.

[0005] That is, the prior art has the following defects:

[0006] (1) For radioactive zirconium smelting slag containing uranium and thorium, the method of alkali roasting-nitric acid dissolution-extraction-washing impurities-stepwise back extraction proposed by LIURongli et al. can basically realize the recovery of uranium and thorium for multi-component complex zirconium smelting slag, but the effect of volume reduction, mass reduction and recovery of other valuable metals of zirconium smelting slag is poor, and the problems of large reagent consumption, high equipment requirement and the like also limit its practical application.

[0007] (2) The existing technology only recovers zirconium and silicon in zirconium smelting slag, or modifies and recovers the whole zirconium smelting slag, without considering the comprehensive recovery and utilization of valuable elements in zirconium smelting slag, especially the treatment and disposal of radioactive elements uranium and thorium.

[0008] (3) The existing extraction and recovery method of radioactive waste slag adopts high-acid leaching method or stepwise leaching method, but the above-mentioned methods have problems of large reagent consumption, long process flow, sensitivity to system acidity and impurity content, large loss of valuable metals, etc., resulting in low overall recovery rate of valuable elements, high investment cost and the like, which are not suitable for multi-metal component system containing radioactive elements.

[0009] In addition, the valuable element extraction and recovery of the high-silicon-content metal smelting waste slag containing uranium and thorium at home and abroad mainly proposes to adopt high-acid dissolution leaching method or stepwise leaching method. The high-acid dissolution leaching method improves the solid-liquid separation by regulating the form of silicon in the solution under high-temperature and high-acid conditions. However, the high-acid dissolution leaching method will make all the elements in the slag dissolve into the solution, and the ammonia neutralization, the cooling ammonium aluminum alum crystallization, the EDTA complexation, or the evaporation concentration, the aluminum ammonium alum method for removing aluminum, and the neutralization for removing iron are used to reduce the impurities of iron and aluminum, and the extraction method is combined to separate and recover uranium and thorium. The above method has the disadvantages of large reagent consumption, long process route, large amount of slag, etc. The stepwise leaching method is based on the different leaching efficiencies of the elements in the waste slag under different leaching conditions, and the selective segmented extraction of the target elements is carried out, and the alkali leaching of uranium, the acid leaching of rare earth, or the concentrated acid leaching of the leaching slag and the countercurrent leaching of the leaching solution are used to carry out the multi-stage stepwise leaching of the waste slag. The above method also has the problems of large reagent consumption, long process flow, sensitivity to the valuable element and impurity content in the slag, limited applicability, etc. SUMMARY

[0010] The present application aims at the deficiencies of the prior art, and provides a method for extracting and recovering valuable elements such as uranium and thorium from zirconium smelting waste slag, which improves the operation condition of the separation process, improves the separation efficiency of the valuable elements, and realizes the efficient extraction of valuable elements from complex multi-component waste slag. The above-mentioned purpose is realized in the design and process control of the zirconium smelting waste slag valuable element efficient leaching and separation process route, so as to realize the comprehensive extraction and efficient separation and recovery of the valuable elements in the zirconium smelting waste slag.

[0011] Therefore, the present application provides a method for comprehensive recovery of valuable elements in zirconium smelting waste slag, which comprises:

[0012] (1) roasting pretreatment:

[0013] The zirconium smelting waste slag is roasted and ground;

[0014] (2) leaching:

[0015] The ground roasted slag is mixed with water for leaching, and then hydrochloric acid solution is added to adjust the pH to 0.5-2.0;

[0016] After the leaching is completed, the solid-liquid separation is carried out, and the leaching slag is countercurrently washed, and the washing liquid is optionally returned as part of the water for leaching;

[0017] (3) iron extraction separation:

[0018] The zirconium smelting waste slag leaching solution is extracted with an iron extraction agent, and is countercurrently extracted;

[0019] The iron-loaded organic phase is back-extracted with HCl solution, and is countercurrently back-extracted to obtain a FeCl3 solution, and the organic phase after back-extraction is returned to the iron extraction cycle for use;

[0020] (4) Uranium extraction separation:

[0021] Uranium is extracted by using a uranium extractant, and countercurrent extraction is performed;

[0022] The uranium-loaded organic phase is back-extracted by using a Na2CO3 solution, and a uranium concentrate product is prepared by circulating precipitation with a NaOH solution;

[0023] The organic phase after back-extraction is returned to the uranium extraction cycle for reuse;

[0024] (5) Thorium extraction separation:

[0025] After the solution is subjected to iron and uranium extraction separation, thorium is extracted, and countercurrent extraction is performed;

[0026] The thorium-loaded organic phase is back-extracted by using a NaOH solution, and countercurrent back-extraction is performed to obtain a thorium residue;

[0027] The organic phase after back-extraction is returned to the thorium extraction cycle for reuse;

[0028] After iron, uranium, and thorium extraction, the raffinate is returned to a zirconium smelting production line to recover zirconium.

[0029] The above technical solution provides a method for extracting and recovering uranium, thorium, iron, and zirconium from zirconium smelting waste residue, improves the existing extraction and separation process, increases the recovery rate of valuable elements, reduces the reagent cost in the recovery process, and realizes efficient extraction and recovery of valuable elements from complex multi-component waste residue containing radioactivity.

[0030] The method of roasting pretreatment-hydrochloric acid leaching is used to realize volume reduction and loss reduction of zirconium smelting waste residue and efficient leaching of valuable elements. By adjusting the phase of zirconium smelting waste residue through roasting and fine control of acid addition and stirring mode during the leaching process, the solid-liquid separation of the leaching slurry is improved, the loss of valuable metals is reduced, and efficient extraction of valuable metals in high-silicon waste residue is realized.

[0031] As a preferred solution, the method for comprehensive recovery of valuable elements of zirconium smelting waste residue satisfies at least one of the following characteristics:

[0032] In step (3), the iron extractant includes 5-10 vt% N235 (trioctyldecyl tertiary amine), 5-20 vt% secondary octanol, and the balance is sulfonated kerosene;

[0033] In step (4), the uranium extractant includes 1-5 vt% N235, 3-10 vt% TBP (Tributyl Phosphate), and the balance is sulfonated kerosene;

[0034] In step (5), the thorium extractant includes 5-15 vt% P204 (D2EHPA), and the balance is sulfonated kerosene.

[0035] In step (3), N235+2-octanol is used to extract iron; in step (4), N235+TBP is used to extract uranium, and through the difference in the separation coefficient of N235 system under different additives for uranium and iron, efficient separation and recovery of iron and uranium are realized through multi-stage extraction.

[0036] In step (4), for the solution after the extraction and separation of iron and uranium, P204 is used to extract thorium, and NaOH solution is used to precipitate and extract thorium, and the raffinate after the extraction of iron, uranium and thorium is returned to the zirconium smelting production line, so that the zirconium and other valuable metals in the solution can be further recovered, the metal recovery rate is improved, and the generation of waste water is avoided.

[0037] In the present application, the zirconium smelting waste slag is a typical zircon sand "one acid and one alkali method" smelting waste slag produced in the production of zirconium oxychloride, and the zirconium smelting waste slag without roasting treatment meets at least one of the following characteristics:

[0038] The water content is 55-70wt%;

[0039] The uranium content is 0.5-1.0wt%, the ThO2 content is 0.3-0.71wt%, the REO content is 8-12wt%, and the SiO2 content is ≥20wt%.

[0040] The main impurity elements of the zirconium smelting waste slag are Si, Na, Fe and Zr.

[0041] As a preferred scheme, step (1) of the method for comprehensive recovery of valuable elements of the above-mentioned zirconium smelting waste slag meets at least one of the following characteristics:

[0042] The roasting is carried out in an air or oxygen atmosphere;

[0043] The heating rate of roasting is 2℃ / min-10℃ / min;

[0044] The roasting temperature is 200℃-500℃;

[0045] The roasting time is 2h-6h;

[0046] The cooling rate after roasting is 5℃ / min-20℃ / min;

[0047] The grinding mode is disc grinding and / or rod grinding;

[0048] The proportion of zirconium smelting slag after grinding of ≤5mm is more than 90%.

[0049] As a preferred scheme, step (2) of the method for comprehensive recovery of valuable elements of the above-mentioned zirconium smelting waste slag meets at least one of the following characteristics:

[0050] The leaching water includes water, and optionally includes a washing liquid;

[0051] The liquid-solid volume mass ratio of the ground roasted slag and the water for leaching is (2.5-5.0 kg):1L;

[0052] The stirring rate of the mixture of the ground roasted slag and the water for leaching is 80r / min-240r / min;

[0053] The concentration of the hydrochloric acid solution is 6mol / L-12mol / L;

[0054] The temperature of the leaching is 60℃-90℃;

[0055] The time of the leaching is 2h-6h;

[0056] The washing ratio of the countercurrent washing is 0.5-1.0:1;

[0057] The number of washing stages is 3-5 stages.

[0058] As a preferred solution, the step (3) of the method for comprehensive recovery of valuable elements from zirconium smelting waste slag satisfies at least one of the following characteristics:

[0059] The temperature of the iron extraction is 20-40℃;

[0060] The iron extraction is carried out by 3-5 stages of countercurrent extraction;

[0061] The concentration of the HCl solution is 3-10g / L;

[0062] The iron-loaded organic phase is subjected to 3-5 stages of countercurrent stripping.

[0063] As a preferred solution, the step (4) of the method for comprehensive recovery of valuable elements from zirconium smelting waste slag satisfies at least one of the following characteristics:

[0064] The temperature of the uranium extraction is 20-40℃;

[0065] The uranium extraction is carried out by 3-5 stages of countercurrent extraction;

[0066] The concentration of the Na2CO3 solution is 100-200g / L;

[0067] The stripping temperature of the uranium-loaded organic phase is 20-40℃;

[0068] The uranium-loaded organic phase is subjected to 3-5 stages of countercurrent stripping.

[0069] As a preferred solution, the step (5) of the method for comprehensive recovery of valuable elements from zirconium smelting waste slag satisfies at least one of the following characteristics:

[0070] The temperature of the thorium extraction is 20-40℃;

[0071] The thorium extraction is carried out by 3-5 stages of countercurrent extraction;

[0072] The concentration of the NaOH solution is 2-5 mol / L;

[0073] The temperature of the thorium-loaded organic phase counter-current stripping is 20-40 DEG C.

[0074] The thorium-loaded organic phase is counter-current stripped for 3-5 stages.

[0075] As a preferred solution, the uranium leaching rate is greater than or equal to 96% and the thorium leaching rate is greater than or equal to 90% after the step (2) of the method for comprehensive recovery of valuable elements from zirconium smelting waste residue.

[0076] As a preferred solution, the iron extraction rate is greater than or equal to 95.0% in the step (3) of the method for comprehensive recovery of valuable elements from zirconium smelting waste residue.

[0077] As a preferred solution, the uranium extraction rate is greater than or equal to 98.0% in the step (4) of the method for comprehensive recovery of valuable elements from zirconium smelting waste residue.

[0078] As a preferred solution, the thorium extraction rate is greater than or equal to 95.0% in the step (5) of the method for comprehensive recovery of valuable elements from zirconium smelting waste residue.

[0079] Compared with the prior art, the present application has at least the following beneficial effects:

[0080] The zirconium smelting waste residue has the characteristics of multiple components, low valuable metal content, high impurity content, high silicon content and radioactive elements, and the prior art has the technical problems of incomplete valuable element recovery from the waste residue, low metal recovery rate and high reagent cost. In view of the problems of the prior art, the present application comprehensively considers the comprehensive extraction of valuable elements, solid-liquid separation, and gradient separation of valuable metals, and proposes a method for comprehensive recovery of valuable elements from zirconium smelting waste residue, which has the following technical advantages:

[0081] The valuable metal recovery rate is high. By using the methods of roasting, intensified leaching, multi-metal gradient extraction and separation, and solution regulation and return recovery, the valuable metals in the zirconium residue are extracted and recovered, the uranium leaching rate is greater than 96%, and the thorium leaching rate is greater than 90%. Compared with the prior art, the process is simple, the types of recovered metals are more, the recovery rate is high, and no three wastes are generated.

[0082] The reagent cost is low. The prior art mostly uses acid-base combined leaching or high-acid dissolution leaching or step-by-step leaching, and in the solution impurity removal process, ammonia is used as a neutralizing agent and sodium chlorate is used as an oxidizing agent to remove iron and aluminum, resulting in high reagent cost. At the same time, due to the high acidity of the solution, the volume of the adjusted solution increases significantly, increasing the cost of subsequent ammonia-containing wastewater treatment. The present application uses hydrochloric acid leaching-extraction method for gradient extraction and separation, and controls the solution acidity and chloride concentration, which significantly reduces the reagent cost.

[0083] The zirconium smelting waste residue has small residue generation amount and no waste water generation. The residue volume of the zirconium smelting waste residue leaching residue is reduced to below 35% through the method, the residual uranium and thorium content in the residue can be reduced to below the radioactivity exemption value, thereby greatly reducing the influence on the environment. The washing water can be returned to preparation of the leaching agent, the extractant can be recycled, the raffinate can be returned to the zirconium smelting production line to recover zirconium and other metals, and no waste water is generated in the whole process.

[0084] The above description is only a summary of the technical scheme of the present application. In order to more clearly understand the technical means of the present application, the specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0085] Figure 1 The process flow chart of the present application is a specific embodiment of the method for comprehensive recovery of valuable elements of zirconium smelting waste residue. DETAILED DESCRIPTION

[0086] In the following description, a large number of specific details are given in order to provide a more thorough understanding of the technical scheme provided by the present application. However, it is obvious to those skilled in the art that the technical scheme provided by the present application can be implemented without one or more of these details.

[0087] In the examples and comparative examples of the present application, the raw materials are obtained from the market.

[0088] In the examples and comparative examples of the present application, the liquid-solid ratio refers to the volume of liquid (L) to the weight of solid (kg)

[0089] Example 1

[0090] A zirconium smelting waste residue, with a moisture content of 60.0%, U content of 0.65% in the waste residue, ThO2 content of 0.50%, REO of about 9.5%, SiO2 of 25.0%, Fe2O3 of 11.2%, and ZrO2 of 10.3%.

[0091] Reference Figure 1 In an air atmosphere, the zirconium smelting waste residue is spread in a crucible with a thickness of 20mm, the heating rate is 2℃ / min, the calcination temperature is 300℃, the calcination time is 2h, and after calcination, the cooling rate is 10℃ / min, and the temperature is reduced to room temperature. After calcination, the residue is ground by disc mill, and the zirconium smelting residue after grinding accounts for 95% of the residue.

[0092] The ground roasted slag is added with washing water at a liquid-solid volume mass ratio of 1.0, water at a liquid-solid volume mass ratio of 1.5, slowly stirred at a stirring rate of 120 r / min, slowly added with 12 mol / L concentrated hydrochloric acid at a rate of 1 mL / min, the leaching pH is controlled at 1.0, the leaching temperature is 90℃, the leaching time is 4 h, after the leaching is completed, solid-liquid separation is performed, and countercurrent washing is performed on the leaching residue, the washing ratio is 1.0:1, the washing section number is 3, and the washing water is returned as leaching water. The leaching residue yield is 29.4%, the uranium content of the leaching residue is 0.008%, the thorium content is 0.01%, the uranium leaching rate is 99.6%, the thorium leaching rate is 99.4%, and the iron leaching rate is 90.7%.

[0093] The zirconium smelting waste residue leaching solution is first used for extracting iron by using 5% v / v N235 + 5% v / v secondary octanol + the rest sulfonated kerosene, the temperature is 20℃, 4-stage countercurrent extraction is performed, the iron extraction rate is 98.4%, the iron-loaded organic phase is back-extracted by using 5 g / L HCl solution, the temperature is 40℃, 4-stage countercurrent back-extraction is performed, and FeCl3 solution is obtained; and the organic phase after back-extraction is returned to the iron extraction for recycling.

[0094] The uranium is extracted by using 5% v / v N235 + 5% v / v TBP + the rest sulfonated kerosene, the temperature is 20℃, 4-stage countercurrent extraction is performed, the uranium extraction rate is 99.2%. The uranium-loaded organic phase is back-extracted by using 100 g / L Na2CO3 solution, the temperature is 20℃, 4-stage countercurrent back-extraction is performed, and uranium qualified liquid is obtained, and uranium concentrate products are prepared through NaOH solution circulation precipitation; and the organic phase after back-extraction is returned to the uranium extraction for recycling.

[0095] After the iron and uranium extraction separation, the solution is subjected to extraction separation of thorium. The thorium is extracted by using 5% v / v P204 + the rest sulfonated kerosene, the temperature is 20℃, 4-stage countercurrent extraction is performed, the thorium extraction rate is 95.8%. The thorium-loaded organic phase is back-extracted by using 2 mol / L NaOH solution, the temperature is 20℃, 4-stage countercurrent back-extraction is performed, and thorium residue is obtained; and the organic phase after back-extraction is returned to the thorium extraction for recycling. The raffinate after the iron, uranium and thorium extraction is returned to the zirconium smelting production line for recycling of zirconium.

[0096] Example 2

[0097] A zirconium smelting waste residue, the water content is 63.1%, the U content in the waste residue is 0.98%, the ThO2 content is 0.69%, the REO is about 9.1%, the SiO2 is 29.5%, the Fe2O3 is 12.3%, and the ZrO2 is 10.6%.

[0098] In an air atmosphere, the zirconium smelting waste residue is spread and placed in a crucible, the thickness is 50 mm, the heating rate is 2℃ / min, the roasting temperature is 500℃, the roasting time is 6 h, after the roasting is completed, the cooling rate is 5℃ / min, and the temperature is reduced to room temperature. The roasted residue is subjected to disc milling, and after the milling, the zirconium smelting residue particle size of-5 mm accounts for 95%.

[0099] The ground roasted slag is added with washing water at a liquid-solid volume mass ratio of 1.0, added with water at a liquid-solid volume mass ratio of 4.0, stirred at a stirring rate of 240 r / min, slowly added with 12 mol / L concentrated hydrochloric acid at a rate of 5 mL / min, the leaching pH is controlled at 0.5, the leaching temperature is 90°C, the leaching time is 6 h, after the leaching is completed, solid-liquid separation is performed, and the leaching residue is countercurrently washed, the washing ratio is 1.0:1, the washing section number is 5, and the washing liquid is returned as the leaching water. The leaching residue yield is 27.5%, the uranium content of the leaching residue is 0.005%, the thorium content is 0.006%, the uranium leaching rate is 99.8%, the thorium leaching rate is 99.7%, and the iron leaching rate is 93.6%.

[0100] The zirconium smelting waste residue leaching solution is first used for extracting iron by using 10 vt% N235 + 15 vt% sec-octyl alcohol + the balance of sulfonated kerosene, the temperature is 40°C, 4-stage countercurrent extraction is performed, the iron extraction rate is 98.9%, the iron-loaded organic phase is back-extracted by using 10 g / L HCl solution, the temperature is 35°C, 5-stage countercurrent back-extraction is performed, and FeCl3 solution is obtained; and the organic phase after back-extraction is returned to the iron extraction for cyclic use.

[0101] Uranium is extracted by using 5 vt% N235 + 5 vt% TBP + the balance of sulfonated kerosene, the temperature is 40°C, 4-stage countercurrent extraction is performed, the uranium extraction rate is 99.2%. The uranium-loaded organic phase is back-extracted by using 200 g / L Na2CO3 solution, the temperature is 35°C, 3-stage countercurrent back-extraction is performed, and uranium qualified liquid is obtained, and uranium concentrate products are prepared through cyclic precipitation by using NaOH solution; and the organic phase after back-extraction is returned to the uranium extraction for cyclic use.

[0102] After the iron and uranium are extracted and separated, the solution is subjected to extraction and separation of thorium. Thorium is extracted by using 15 vt% P204 + the balance of sulfonated kerosene, the temperature is 40°C, 4-stage countercurrent extraction is performed, the thorium extraction rate is 97.5%. The thorium-loaded organic phase is back-extracted by using 3 mol / L NaOH solution, the temperature is 30°C, 3-stage countercurrent back-extraction is performed, and thorium residue is obtained; and the organic phase after back-extraction is returned to the thorium extraction for cyclic use. The raffinate after the extraction of iron, uranium and thorium is returned to the zirconium smelting production line for recycling of zirconium.

[0103] Example 3

[0104] A zirconium smelting waste residue, the water content is 65%, the U content in the waste residue is 0.73%, the ThO2 content is 0.71%, the REO is about 8.7%, the SiO2 is 30.1%, the Fe2O3 is 10.6%, and the ZrO2 is 11.4%.

[0105] The zirconium smelting waste residue is spread in a crucible in an air atmosphere, with a thickness of 40 mm, a heating rate of 5℃ / min, a calcination temperature of 400℃, a calcination time of 4h, and a cooling rate of 15℃ / min after calcination, and the residue is cooled to room temperature. After calcination, the residue is ground with a rod mill, and the particle size of the zirconium smelting residue after grinding is-5 mm, accounting for 96%.

[0106] After the calcined residue is ground, washing water is added at a liquid-solid volume mass ratio of 1.0, and water is added at a liquid-solid volume mass ratio of 2.0, the stirring rate is 200 r / min, 12 mol / L concentrated hydrochloric acid is slowly added at a rate of 2 mL / min, the leaching pH is controlled at 0.8, the leaching temperature is 90℃, the leaching time is 6h, after leaching, the solid-liquid separation is carried out, and the leaching residue is countercurrent washed, the washing ratio is 0.8:1, the washing section number is 5, and the washing liquid is returned as leaching water. The leaching residue yield is 28.4%, the uranium content of the leaching residue is 0.006%, the thorium content is 0.008%, the uranium leaching rate is 99.7%, the thorium leaching rate is 99.6%, and the iron leaching rate is 92.5%.

[0107] The zirconium smelting waste residue leaching solution first extracts iron using 10vt% N235+10vt% sec-octyl alcohol+the rest of sulfonated kerosene, at a temperature of 40℃, through 3-stage countercurrent extraction, the iron extraction rate is 99.1%, the iron-loaded organic phase is back-extracted using 10g / L HCl solution, at a temperature of 40℃, through 4-stage countercurrent back-extraction, FeCl3 solution is obtained; the organic phase after back-extraction is returned to the iron extraction cycle for reuse.

[0108] Uranium is extracted using 3vt% N235+3vt% TBP+the rest of sulfonated kerosene, at a temperature of 40℃, through 5-stage countercurrent extraction, the uranium extraction rate is 99.5%. The uranium-loaded organic phase is back-extracted using 200g / L Na2CO3 solution, at a temperature of 40℃, through 5-stage countercurrent back-extraction, uranium qualified liquid is obtained, and uranium concentrate products are prepared through NaOH solution circulation precipitation; the organic phase after back-extraction is returned to the uranium extraction cycle for reuse.

[0109] After the iron and uranium extraction separation, the solution is subjected to thorium extraction separation. Thorium is extracted using 10vt% P204+the rest of sulfonated kerosene, at a temperature of 30℃, through 3-stage countercurrent extraction, the thorium extraction rate is 96.1%. The thorium-loaded organic phase is back-extracted using 3mol / L NaOH solution, at a temperature of 30℃, through 3-stage countercurrent back-extraction, thorium residue is obtained; the organic phase after back-extraction is returned to the thorium extraction cycle for reuse. After iron, uranium and thorium extraction, the raffinate is returned to the zirconium smelting production line for zirconium recovery.

[0110] Comparative Example 1

[0111] CN202210235185 Method for comprehensive recovery of uranium, thorium, titanium, zirconium and rare earths in green layer silicon cerium titanium ore

[0112] A method for comprehensive recovery of uranium, thorium, titanium, zirconium and rare earths in green layer silicon cerium titanium ore is disclosed, comprising the following steps:

[0113] Step S1: grinding the green layer silicon cerium titanium ore to obtain -1-0 mm coarse ore; wherein, -0.074-0 mm coarse ore is used as slurry into mixed concentrate; -1+0.074 mm coarse ore is used into next step for two-stage magnetic separation;

[0114] Step S2: using magnetic field to perform two-stage magnetic separation on -1+0.074 mm coarse ore to obtain mixed concentrate;

[0115] Step S3: the mixed concentrate is mixed with acid and aged, leached to obtain a first qualified solution; the un-leached part is sequentially subjected to first four-stage countercurrent washing, alkali transformation, acidification, and second countercurrent washing to obtain a second qualified solution;

[0116] Step S4: the first qualified solution is subjected to silicon removal and demulsification treatment, then extraction, crystallization back extraction to obtain a uranium product; the raffinate aqueous phase is precipitated by phosphoric acid to obtain a precipitate of thorium, titanium and zirconium; the second qualified solution is added with ammonia water and polyacrylamide solution, reacted, filtered to obtain a crude product of thorium and other rare earth hydroxides.

[0117] In the comparative example 1, the uranium in the leaching solution is recovered by extraction, and the thorium in the solution is precipitated by phosphonic acid precipitation method to form a radioactive precipitate with titanium and zirconium, which not only wastes the thorium resources, but also brings environmental pressure due to the formation of radioactive slag. The present application realizes the gradient separation and recovery of metals in the solution by extraction method, so that the valuable metals in the zirconium smelting waste slag are recovered in a clean and efficient manner, the radioactive waste slag is reduced in volume and amount, and the radioactive exemption is realized at the same time, and the metals are recycled as secondary resources. Compared with the comparative example 1, the present application has advanced process.

[0118] The above is only a preferred embodiment of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for comprehensive recovery of valuable elements from zirconium smelting waste slag, characterized in that: The method includes: (1) Calcination pretreatment: Roasting and grinding zirconium smelting waste slag; (2) Leaching: The ground calcined slag is mixed with leaching water, and then hydrochloric acid solution is added to adjust the pH to 0.5-2.0; After leaching is completed, the solid and liquid are separated, and the leached residue is washed in countercurrent, and the washing liquid is optionally returned as part of the leaching water; (3) Iron extraction and separation: The zirconium smelting waste residue leachate is extracted with an iron extractant and subjected to countercurrent extraction; The iron-loaded organic phase is back-extracted with HCl solution, and after countercurrent back-extraction, FeCl3 solution is obtained. After back-extraction, the organic phase is returned to the iron extraction cycle for reuse; (4) Uranium extraction and separation: The uranium is extracted using a uranium extractant and subjected to countercurrent extraction; The uranium-loaded organic phase is stripped with Na2CO3 solution and precipitated through a NaOH solution cycle to produce a uranium concentrate product; After stripping, the organic phase is returned to the uranium extraction cycle; (5) Thorium extraction and separation: The solution after the iron and uranium extraction and separation is subjected to thorium extraction and separation by countercurrent extraction; The thorium-loaded organic phase is stripped with NaOH solution and subjected to countercurrent stripping to obtain thorium slag; After back extraction, the organic phase is returned to the thorium extraction cycle; After extracting iron, uranium and thorium, the raffinate is returned to the zirconium smelting production line to recover zirconium.

2. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Satisfy at least one of the following characteristics: In step (3), the iron extractant comprises: 5-10vt% N235, 5-20vt% sec-octanol, and the balance is sulfonated kerosene; In step (4), the uranium extractant comprises: 1-5 wt% N235, 3-10 wt% TBP, and the balance is sulfonated kerosene; In step (5), the thorium extractant includes: 5-15vt% P204, and the balance is sulfonated kerosene.

3. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: The uncalcined zirconium smelting waste slag meets at least one of the following characteristics: The moisture content is 55-70wt%; Uranium content is 0.5-1.0wt%, ThO2 content is 0.3-0.71wt%, REO content is 8-12wt%, and SiO2 content is ≥20wt%.

4. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Step (1) satisfies at least one of the following characteristics: Calcination is carried out in air or oxygen atmosphere; The heating rate of calcination is 2℃ / min~10℃ / min; The calcination temperature is 200°C to 500°C; The roasting time is 2h~6h; The cooling rate after calcination is 5℃ / min~20℃ / min; Grinding method is disc grinding and / or rod grinding; After grinding, zirconium smelting slag with a size of ≤5mm accounts for more than 90%.

5. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Step (2) satisfies at least one of the following characteristics: The leaching water comprises water and optionally a washing liquid; The liquid-solid volume mass ratio of the ground roasted slag to the leaching water is (2.5-5.0 kg):1 L; The stirring rate of mixing the ground roasted slag and the leaching water is 80 r / min to 240 r / min; The concentration of the hydrochloric acid solution is 6 mol / L to 12 mol / L; The leaching temperature is 60℃~90℃; The leaching time is 2h to 6h; The washing ratio of countercurrent washing is 0.5 to 1.0:1; The number of washing sections is 3 to 5.

6. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Step (3) satisfies at least one of the following characteristics: The temperature for extracting iron is 20-40°C; The extracted iron undergoes 3 to 5 stages of countercurrent extraction; The concentration of HCl solution is 3-10 g / L; The iron-loaded organic phase undergoes 3 to 5 stages of countercurrent stripping.

7. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Step (4) satisfies at least one of the following characteristics: The temperature for extracting uranium is 20-40°C; The extracted uranium undergoes 3 to 5 stages of countercurrent extraction; The concentration of Na2CO3 solution is 100-200g / L; The stripping temperature of the uranium-loaded organic phase is 20-40°C; The uranium-loaded organic phase undergoes 3 to 5 stages of countercurrent stripping.

8. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: Step (5) satisfies at least one of the following characteristics: The temperature for thorium extraction is 20-40°C; Thorium extraction undergoes 3 to 5 stages of countercurrent extraction; The concentration of NaOH solution is 2-5 mol / L; The temperature for the reverse extraction of thorium-loaded organic solvents is 20-40°C; The thorium-loaded organic phase undergoes 3 to 5 stages of countercurrent stripping.

9. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: After leaching in step (2), the uranium leaching rate is ≥96%, and the thorium leaching rate is ≥90%; In step (3), the iron extraction rate is ≥95.0%.

10. The method for comprehensive recovery of valuable elements from zirconium smelting waste slag according to claim 1, characterized in that: In step (4), the uranium extraction rate is ≥98.0%; In step (5), the thorium extraction rate is ≥95.0%.

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