Deep sea rare earth sediment flotation-leaching combined treatment device system and method

Abstract

The invention provides a flotation-leaching combined treatment device system and method for deep sea rare earth deposits, and the method comprises the following steps: firstly, carrying out desliming screening on the deep sea rare earth deposits to obtain pretreated minerals with the particle size being greater than or equal to 5 microns; the pretreated minerals are graded with the grain size being 20 microns as the boundary and then treated through different flotation methods, then two-stage acid leaching is conducted through different acid solutions, light rare earth elements and heavy rare earth elements are extracted respectively, and low-cost and efficient recovery of the rare earth is achieved; and carrying out electrodialysis membrane separation on the leaching waste liquid to recover free acid, and mixing and neutralizing the treated residual acid liquid and the residual deep sea clay after desliming and screening to generate silicate colloid. The method has the characteristics of efficient recovery, low cost and environmental friendliness, and is suitable for large-scale development of deep sea rare earth resources.

Description

Technical Field

[0001] The present invention relates to the technical field of deep-sea mineral resource development, and particularly to a combined flotation-leaching treatment device system and method for deep-sea rare earth sediments. Background Art

[0002] The existing flotation processes for rare earth minerals (such as bastnasite and monazite) generally face problems such as high energy consumption, complex processes, and low recovery rates. For example, the "high-temperature flotation method" adopted by the Mountain Pass Mine in the United States needs to heat the pulp to above 90°C and go through six times of stirring and multiple reagent additions. Although it can obtain concentrates with a REO (rare earth oxide) grade of 60% - 62% and a recovery rate of 65% - 70%, it has the defects of high energy consumption and a long process. Domestic processes use hydroxamic acid collectors and reagents such as water glass to treat bastnasite at 40°C, but the concentrate grade is only 50% - 62%, the recovery rate is less than 70%, and the tailing slurry water is difficult to precipitate, resulting in great environmental protection pressure. As an emerging rare earth resource, deep-sea sediments have complex occurrence states (such as adsorbed on bioapatite or Fe-Mn nodules). Although the direct acid leaching method can extract rare earths, the acid consumption is huge (such as high consumption of sulfuric acid and hydrochloric acid), and a large amount of waste liquid and waste residue are generated, with high environmental governance costs. For example, the direct acid leaching of deep-sea clay in the Pacific Ocean requires high-concentration acid solution, with an acid consumption of hundreds of kilograms per ton of raw ore, and the rare earth recovery rate is only 84% - 94%. At the same time, the dissolution rates of impurity ions such as aluminum and iron are high, and the subsequent separation is difficult. Existing technologies have tried to combine flotation pretreatment to reduce acid consumption. For example, the "classified flotation - high-intensity magnetic separation - low-temperature phosphoric acid leaching" process can increase the rare earth recovery rate to 84.11%, but it still requires multi-stage flotation and high-intensity magnetic separation, with a high process complexity. In addition, flotation reagents (such as salicylhydroxamic acid collectors) have poor selectivity for fine-grained minerals, and the reagent dosage is large (0.8 - 3 kg per ton of ore), resulting in increased costs. In traditional processes, ammonia nitrogen pollution (such as ammonium salt leaching of ion-adsorbed rare earth ores) and tailing water treatment problems are prominent. For example, although the use of magnesium chloride leaching for land rare earth ores avoids ammonia nitrogen pollution, the extraction and enrichment of low-concentration rare earth leaching solutions still require complex steps and high reagent costs.

[0003] CN115094230A discloses a method for extracting rare earth, phosphorus, and manganese elements from deep-sea rare earth-rich sediments, including the following steps: S1. Pre-enrich the deep-sea rare earth-rich sediments to obtain a pre-enriched concentrate; S2. Separate the pre-enriched concentrate obtained in step S1 by first high-intensity magnetic separation to obtain a high-intensity magnetic concentrate and a phosphorus-containing rare earth high-intensity magnetic tailing; S3. Subject the phosphorus-containing rare earth high-intensity magnetic tailing obtained in step S2 to phosphoric acid leaching to obtain a leaching solution and a leaching residue. The leaching solution is subjected to extraction and back-extraction to obtain an extraction raffinate and a crude rare earth residue.

[0004] CN109234548A discloses a method for extracting rare earths from deep-sea sediments by self-heating and aging in a sulfuric acid bath. The deep-sea sediments are naturally air-dried or dried to a moisture content of more than 5%. The deep-sea sediments with a moisture content of 5%-50% are mixed with a certain amount of 98% sulfuric acid and placed in a leaching tank. By utilizing the certain water content, phase characteristics and chemical composition of the deep-sea sediments, a large amount of sulfuric acid dilution heat and chemical reaction heat are generated during the mixing process with sulfuric acid, realizing the low-energy consumption extraction of rare earths by self-heating and aging of sulfuric acid. After the aged material in the leaching tank is kept warm for a certain time, it is leached by spraying water or stirring, so that the rare earths enter the solution, and then the rare earths are recovered by one or more of the methods of extraction, ion exchange adsorption, precipitation, and crystallization.

[0005] CN111748705A discloses a method for extracting rare earth elements from deep-sea sediments, which specifically includes the following steps: preparing a leaching device, the leaching device includes a leachate outlet, a feeding pipeline connecting the outside and the reaction tank, and a reaction tank with a stirring component inside; adding acid solution, flocculant and deep-sea sediments into the leaching device through the feeding pipeline, turning on the stirring component, and collecting the leachate from the leachate outlet after stirring and leaching by the leaching device.

[0006] However, the above-mentioned methods for extracting deep-sea rare earths have not well solved the problems of energy consumption and pollution. Therefore, it is necessary to develop a method for extracting deep-sea rare earth resources that has the characteristics of high-efficiency recovery, low cost and environmental friendliness. Summary of the Invention

[0007] In view of the problems existing in the prior art, the present invention provides a flotation-leaching combined treatment device system and method for deep-sea rare earth sediments. Through the collaborative innovation of classification flotation, gradient acid leaching, acid solution circulation and in-situ dehydration technologies, the problems of low rare earth recovery rate, high acid consumption, high environmental pollution risk and poor adaptability to the deep-sea extreme environment in the prior art are solved, and it can meet the industrial application requirements of a mining system with a water depth of 3000-6000m.

[0008] To achieve this purpose, the present invention adopts the following technical solutions:

[0009] In the first aspect, the present invention provides a flotation-leaching combined treatment method for deep-sea rare earth sediments, and the flotation-leaching combined treatment method for deep-sea rare earth sediments includes the following steps:

[0010] (a) Dewatering and screening the deep-sea rare earth sediments to obtain a pretreated mineral with a particle size ≥ 5μm;

[0011] (b) Classifying the pretreated mineral with a particle size of 20μm as the boundary to obtain a coarse-grained mineral with a particle size > 20μm and a fine-grained mineral with a particle size of 5-20μm;

[0012] (c) The coarse-grained minerals are subjected to microbubble flotation to obtain a first flotation concentrate; the fine-grained minerals are subjected to nano-collector flotation to obtain a second flotation concentrate;

[0013] (d) After the first flotation concentrate and the second flotation concentrate are mixed and subjected to two-stage acid leaching, the leaching waste liquid is separated and recovered for free acid by electrodialysis membrane, and the treated residual acid liquid is mixed and neutralized with the deep-sea clay remaining after the mud removal and screening in step (a) to generate a silicate colloid;

[0014] In the two-stage acid leaching, in the first-stage acid leaching, hydrochloric acid with a concentration of 1-2 mol / L is used to extract light rare earth elements;

[0015] In the second-stage acid leaching, a mixed acid solution with a pH of 1.0-1.5 formed by sulfuric acid and oxalic acid is used to extract heavy rare earth elements.

[0016] The combined flotation-leaching treatment method for deep-sea rare earth sediments of the present invention realizes the efficient recovery of rare earth resources in deep-sea rare earth sediments through mud removal and screening, classification flotation and gradient acid leaching of deep-sea rare earth sediments. The leaching rate of light rare earths > 85% and the leaching rate of heavy rare earths > 95%, and the acid consumption is greatly reduced; the electrodialysis membrane separation is also used to recover free acid from the leaching waste liquid, and the H + recovery rate ≥ 80%, reducing the acid consumption by more than 40%; the treated residual acid liquid is mixed and neutralized with the deep-sea clay remaining after mud removal and screening to generate a silicate colloid, and the heavy metal leaching concentration is lower than the national standard limit, solving the problem of large environmental pollution risk existing in the existing treatment process of deep-sea rare earth sediments.

[0017] The combined flotation-leaching treatment method for deep-sea rare earth sediments of the present invention is applicable to the efficient enrichment and clean extraction of rare earth elements in low-grade (rare earth oxide REO content 0.05%-0.3%), ultra-fine particle size (mineral particle size < 10 μm) deep-sea clay (water depth 3000-6000 m).

[0018] The combined flotation-leaching treatment method for deep-sea rare earth sediments of the present invention first performs mud removal and screening on deep-sea rare earth sediments to obtain pre-treated minerals with a particle size ≥ 5 μm, which can enrich target components, reduce the pulp volume, and improve the subsequent separation efficiency; the pre-treated minerals are classified with a particle size of 20 μm as the boundary and then treated by different flotation methods, which is beneficial to improving the recovery rate of rare earths; then different acid solutions are used for two-stage acid leaching to extract light rare earth elements and heavy rare earth elements respectively, realizing the low-cost and efficient recovery of rare earths.

[0019] The pre-treated minerals with a particle size ≥ 5 μm obtained in step (a) of the present invention can be, for example, 5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 50 μm or 70 μm, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0020] The coarse-grained minerals with a particle size > 20 μm obtained in step (b) can be, for example, 21 μm, 28 μm, 30 μm, 40 μm, 50 μm, 60 μm or 70 μm, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0021] and the fine-grained minerals with a particle size of 5 - 20 μm can be, for example, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm or 20 μm, etc., but are not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] In the first-stage acid leaching in step (d), hydrochloric acid with a concentration of 1 - 2 mol / L is used. For example, it can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] In the second-stage acid leaching, a mixed acid solution with a pH of 1.0 - 1.5 formed by sulfuric acid and oxalic acid is used to extract heavy rare earth elements. For example, it can be 1.0, 1.1, 1.2, 1.25, 1.3, 1.4 or 1.5, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, the deep-sea rare earth sediment in step (a) is also subjected to dehydration treatment before desliming and screening; the dehydration treatment is carried out in a hydrocyclone dehydration device.

[0025] Preferably, the classification in step (b) is carried out in a hydrocyclone classification device.

[0026] Preferably, the inlet flow rate of the hydrocyclone classification device is 6 - 9 m / s. For example, it can be 6 m / s, 6.3 m / s, 6.5 m / s, 7 m / s, 7.5 m / s, 8 m / s or 9 m / s, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] Preferably, during the microbubble flotation in step (c), the bubble diameter is 50 - 100 μm. For example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 85 μm, 90 μm or 100 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In the present invention, it is preferred that the bubble diameter during the microbubble flotation process is 50 - 100 μm to achieve efficient flotation of coarse-grained minerals. When the bubble diameter is small, the binding force between the coarse-grained minerals and the bubbles will be insufficient, and the coarse-grained minerals attached to the bubbles cannot float to the foam layer, reducing the flotation effect. Moreover, if the bubble stability is too high, it is difficult to break due to excessive surface tension, affecting subsequent processing. When the bubble diameter is large, the rising speed is fast, and the coarse-grained minerals cannot be fully attached and float up, also reducing the flotation effect. Moreover, it will increase the impurity content.

[0029] Preferably, a collector is used during the microbubble flotation process.

[0030] Preferably, the collector comprises H2O5 and XQ107 with a mass ratio of 3:1 - 6:1. For example, it can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1 or 6:1, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0031] Preferably, the dosage of the collector is 500 - 700 g / t of coarse-grained minerals. For example, it can be 500 g / t, 520 g / t, 550 g / t, 580 g / t, 600 g / t, 630 g / t, 650 g / t or 700 g / t, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable, and preferably it is 200 - 300 g / t of coarse-grained minerals.

[0032] Preferably, an inhibitor is also used during the microbubble flotation process.

[0033] Preferably, the inhibitor comprises sodium silicate and sodium hexametaphosphate with a mass ratio of 1:(0.5 - 2). For example, it can be 1:0.5, 1:0.8, 1:1, 1:1.2, 1:1.5, 1:1.7, 1:1.8 or 1:2, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0034] Preferably, the microbubble flotation is carried out under the condition that the pulp concentration is 15% - 20%. For example, it can be 15%, 15.5%, 16%, 17%, 18%, 19% or 20%, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0035] Preferably, the microbubble flotation time is 5 - 10 min. For example, it can be 5 min, 6 min, 7 min, 7.5 min, 8 min, 9 min or 10 min, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0036] Preferably, the nano collector in step (c) is prepared by the following method: Mix H2O5 and SiO2 nanoparticles in a mass ratio of 1:(0.1 - 0.3), for example, it can be 1:0.1, 1:0.13, 1:0.15, 1:0.2, 1:0.25, 1:0.28, 1:0.29 or 1:0.3, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0037] Under the condition of pH = 8 - 9, for example, it can be 8, 8.2, 8.3, 8.5, 8.8 or 9, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; Ultrasonically disperse for 20 - 40 min, for example, it can be 20 min, 22 min, 25 min, 30 min, 33 min, 35 min or 40 min, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable; A nano collector with a surface coating structure is formed.

[0038] Preferably, the particle size of the SiO2 nanoparticles < 100 nm, for example, it can be 99 nm, 90 nm, 80 nm, 70 nm, 50 nm, 30 nm or 20 nm, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0039] Preferably, the zeta potential of the nano collector ≥ +20 mV, for example, it can be +20 mV, +22 mV, +25 mV, +28 mV, +30 mV, +35 mV, +40 mV or +50 mV, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0040] Preferably, the dosage of the nano collector is 50 - 100 g / t of fine - grained minerals, for example, it can be 50 g / t of fine - grained minerals, 55 g / t of fine - grained minerals, 60 g / t of fine - grained minerals, 70 g / t of fine - grained minerals, 80 g / t of fine - grained minerals, 90 g / t of fine - grained minerals or 100 g / t of fine - grained minerals, etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0041] Preferably, the liquid - to - solid ratio of the first - stage acid leaching in step (d) is (2 - 5):1 (mL / g), for example, it can be 2:1 (mL / g), 2.2:1 (mL / g), 2.5:1 (mL / g), 3:1 (mL / g), 3.5:1 (mL / g), 4:1 (mL / g) or 5:1 (mL / g), etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable;

[0042] The temperature is 40 - 50°C. For example, it can be 40°C, 42°C, 44°C, 45°C, 48°C, 49°C, 50°C, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable;

[0043] The leaching time is 30 - 60 min. For example, it can be 30 min, 33 min, 35 min, 40 min, 45 min, 50 min, 60 min, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0044] Preferably, the liquid - to - solid ratio of the first - stage acid leaching in the present invention is (2 - 5):1 (mL / g) to achieve efficient leaching of light rare - earth elements. When the liquid - to - solid ratio of the first - stage acid leaching is small, the mass transfer rate will decrease, and the viscosity of the flotation concentrate will increase, thus affecting the leaching rate of light rare - earth elements; when the liquid - to - solid ratio of the first - stage acid leaching is large, the acid concentration will decrease, the reaction rate will decline, and the leaching efficiency of light rare - earth elements will be reduced; the amount of waste liquid will increase, and the subsequent treatment cost will increase.

[0045] Preferably, the sulfuric acid concentration in the second - stage acid leaching is 2 - 3 mol / L. For example, it can be 2 mol / L, 2.1 mol / L, 2.3 mol / L, 2.5 mol / L, 2.7 mol / L, 2.9 mol / L, 3 mol / L, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable;

[0046] The oxalic acid concentration is (0.4 - 0.6) mol / L. For example, it can be 0.4 mol / L, 0.43 mol / L, 0.45 mol / L, 0.5 mol / L, 0.55 mol / L, 0.58 mol / L, 0.6 mol / L, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0047] Preferably, the temperature of the second - stage acid leaching is 60 - 80°C. For example, it can be 60°C, 63°C, 65°C, 70°C, 75°C, 80°C, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable;

[0048] The ultrasonic - assisted leaching time is 60 - 90 min. For example, it can be 60 min, 63 min, 65 min, 70 min, 80 min, 85 min, 90 min, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable;

[0049] The ultrasonic frequency is 20 - 40 kHz. For example, it can be 20 kHz, 22 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable;

[0050] The power density is 0.5 - 1.0 W / cm 3 , for example, it can be 0.5 W / cm 3 , 0.55 W / cm 3 , 0.6 W / cm 3 , 0.7 W / cm 3 , 0.8 W / cm 3 , 0.9 W / cm 3 or 1.0 W / cm 3 etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable.

[0051] Preferably, the second - stage acid leaching of the present invention adopts ultrasonic - assisted leaching, which can enhance the leaching rate of heavy rare - earth elements by more than 2.3 times.

[0052] Preferably, the electrodialysis membrane described in step (d) includes a perfluorosulfonic acid cation - exchange membrane.

[0053] Preferably, the operating current density in the electrodialysis membrane separation process is 20 - 40 A / m 2 , for example, it can be 20 A / m 2 , 22 A / m 2 , 25 A / m 2 , 30 A / m 2 , 35 A / m 2 , 38 A / m 2 or 40 A / m 2 etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable.

[0054] Preferably, the mass ratio of the residual acid solution to the deep - sea clay mixed in step (d) is 1:3 - 1:5. For example, it can be 1:3, 1:3.2, 1:3.5, 1:4, 1:4.3, 1:4.5, 1:4.8, or 1:5, etc., but it is not limited to the listed values, and other unlisted values within this range are also applicable.

[0055] As a preferred technical solution of the present invention, the combined flotation - leaching treatment method for deep - sea rare - earth sediments includes the following steps:

[0056] (a) The dehydrated deep - sea rare - earth sediments are subjected to desliming screening to obtain a pre - treated mineral with a particle size ≥ 5 μm;

[0057] (b) The pre-treated minerals are classified in a hydrocyclone classifier with a particle size limit of 20 μm, obtaining coarse-grained minerals with a particle size > 20 μm and fine-grained minerals with a particle size of 5 - 20 μm; the inlet flow rate of the hydrocyclone classifier is 6 - 9 m / s;

[0058] (c) The coarse-grained minerals are subjected to microbubble flotation for 5 - 10 min to obtain a first flotation concentrate; the fine-grained minerals are subjected to nano-collector flotation to obtain a second flotation concentrate;

[0059] During the microbubble flotation process, the bubble diameter is 50 - 100 μm; a collector is used during the microbubble flotation process; the collector includes H2O5 and XQ107 with a mass ratio of 3:1 - 6:1; the dosage of the collector is 500 - 700 g / t of coarse-grained minerals; an inhibitor is also used during the microbubble flotation process; the inhibitor includes sodium silicate and sodium hexametaphosphate with a mass ratio of 1:(0.5 - 2); the microbubble flotation is carried out under the condition of a pulp concentration of 15% - 20%;

[0060] The nano-collector is prepared by the following method: mixing H2O5 and SiO2 nanoparticles in a mass ratio of 1:(0.1 - 0.3), and ultrasonically dispersing for 20 - 40 min under the condition of pH = 8 - 9 to form a nano-collector with a surface coating structure; the particle size of the SiO2 nanoparticles < 100 nm; the zeta potential of the nano-collector ≥ +20 mV; the dosage of the nano-collector is 50 - 100 g / t of fine-grained minerals;

[0061] (d) After the first flotation concentrate and the second flotation concentrate are mixed and subjected to two-stage acid leaching, the leaching waste liquid is separated and recovered for free acid by electrodialysis membrane, and the treated residual acid liquid is mixed and neutralized with the deep-sea clay remaining after desliming and screening in step (a) according to a mass ratio of 1:3 - 1:5 to generate a silicate colloid;

[0062] In the two-stage acid leaching, the first-stage acid leaching uses hydrochloric acid with a concentration of 1 - 2 mol / L to extract light rare earth elements; the liquid-solid ratio of the first-stage acid leaching is (2 - 5):1 (mL / g), the temperature is 40 - 50 °C, and the leaching time is 30 - 60 min;

[0063] The second-stage acid leaching uses a mixed acid solution of sulfuric acid and oxalic acid to extract heavy rare earth elements; in the second-stage acid leaching, the sulfuric acid concentration is 2 - 3 mol / L, and the oxalic acid concentration is (0.4 - 0.6) mol / L; the pH of the mixed acid solution is 1.0 - 1.5; the temperature of the second-stage acid leaching is 60 - 80 °C, the ultrasonic-assisted leaching time is 60 - 90 min, the ultrasonic frequency is 20 - 40 kHz, and the power density is 0.5 - 1.0 W / cm 3 .

[0064] In a second aspect, as a combined flotation-leaching treatment device system for deep-sea rare earth sediments provided by the present invention, the combined flotation-leaching treatment device system for deep-sea rare earth sediments performs the combined flotation-leaching treatment method for deep-sea rare earth sediments described in the first aspect;

[0065] The combined flotation-leaching treatment device system for deep-sea rare earth sediments includes a classification flotation module, a gradient acid leaching module, and an acid circulation module connected in sequence;

[0066] The classification flotation module includes a desliming and screening device, a hydrocyclone classification device, a microbubble flotation device, and a nano-collector spraying device; the desliming and screening device and the hydrocyclone classification device are arranged in series; the hydrocyclone classification device is respectively connected to the microbubble flotation device and the nano-collector spraying device;

[0067] The gradient acid leaching module includes a first acid leaching reactor and a second acid leaching reactor arranged in parallel; wherein an ultrasonic transducer device is built in the second reactor;

[0068] The acid circulation module includes an electrodialysis stack and a neutralization tank connected in sequence.

[0069] The combined flotation-leaching treatment device system for deep-sea rare earth sediments of the present invention realizes desliming and screening, classification flotation, and gradient acid leaching of deep-sea rare earth sediments through a classification flotation module, a gradient acid leaching module, and an acid circulation module connected in sequence, and has the characteristics of high-efficiency recovery, low cost, and environmental friendliness, and can be widely applied to the large-scale development of deep-sea rare earth resources.

[0070] Preferably, the microbubble flotation device adopts a Venturi tube structure.

[0071] Preferably, the bubble generation efficiency in the microbubble flotation device is ≥5m 3 / h·m 2 , for example, it can be m 3 / h·m 2 , m 3 / h·m 2 , m 3 / h·m 2 , m 3 / h·m 2 , m 3 / h·m 2 , m 3 / h·m 2 , m 3 / h·m 2 or m 3 / h·m 2 etc., but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0072] Preferably, the pressure of the nano - collector spraying device is 0.5 - 1.0 MPa. For example, it can be 0.5 MPa, 0.55 MPa, 0.6 MPa, 0.65 MPa, 0.7 MPa, 0.8 MPa or 1.0 MPa, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0073] Preferably, the electrodialysis stack is connected to the gradient acid leaching module through an acid solution reflux pipeline.

[0074] The number of the electrodialysis stacks in the present invention is 2 groups, namely the first electrodialysis stack and the second electrodialysis stack; the number of the acid solution reflux pipelines is 2, namely the first acid solution reflux pipeline and the second acid solution reflux pipeline;

[0075] The first acid leaching reactor is connected to the first electrodialysis stack, and free acid is recovered through the first electrodialysis membrane separation. The recovered free acid returns to the first acid leaching reactor through the first acid solution reflux pipeline;

[0076] The second acid leaching reactor is connected to the second electrodialysis stack, and free acid is recovered through the second electrodialysis membrane separation. The recovered free acid returns to the second acid leaching reactor through the second acid solution reflux pipeline.

[0077] The residual acid solutions after the treatment of the first electrodialysis stack and the second electrodialysis stack are mixed, and jointly mixed and neutralized with the deep - sea clay remaining after the sludge removal and screening in step (a) to generate silicate colloid.

[0078] Preferably, the deep - sea rare - earth sediment flotation - leaching combined treatment device system further includes a deep - sea mining integration interface connected to the classification flotation module.

[0079] Preferably, the deep - sea mining integration interface includes a micro - disturbance crawler - type suction head and a hydrocyclone dewatering device connected in sequence. The micro - disturbance crawler - type suction head collects seabed sediments, reduces the diffusion of suspended solids, with a turbidity < 50 NTU, and realizes the on - ship continuous operation of the processes of mineral collection - pretreatment - dehydration.

[0080] Preferably, the cone angle of the hydrocyclone dewatering device is 10° - 15°. For example, it can be 10°, 10.5°, 11°, 11.5°, 12°, 13°, 14° or 15°, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0081] Preferably, the ceramic lining thickness of the hydrocyclone dewatering device is 5 - 8 mm. For example, it can be 5 mm, 5.5 mm, 5.8 mm, 6 mm, 6.5 mm, 7 mm or 8 mm, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0082] Preferably, the ceramic lining of the hydrocyclone dehydration device of the present invention has a thickness of 5-8 mm and a pressure resistance of ≥60 MPa, and can be used in the extreme deep-sea environment of 3000-6000 m, eliminating the risk of mineral property variation caused by the traditional land-sea transportation mode; the hydrocyclone dehydration device can make the moisture content of the deep-sea rare earth sediment after dehydration ≤40%.

[0083] Compared with the prior art, the present invention has at least the following beneficial effects:

[0084] (1) The flotation-leaching combined treatment method for deep-sea rare earth sediments provided by the present invention realizes effective particle size stratification of deep-sea rare earth sediments through a three-stage particle size control system of "mud removal - hydraulic classification - differential flotation"; for coarse-grained minerals, microbubble flotation is used to enhance the particle-bubble collision efficiency, and for fine-grained minerals, the surface charge of the nano-collector is regulated to enhance selective adsorption, successfully solving the problem of low separation efficiency caused by the ultra-fine particle size and low grade of minerals in the traditional process, and forming an accurate adaptation to the occurrence state of deep-sea rare earths.

[0085] (2) The flotation-leaching combined treatment method for deep-sea rare earth sediments provided by the present invention constructs a closed-loop process system of "gradient leaching - acid solution regeneration - in-situ neutralization". Through the staged leaching strategy of light / heavy rare earths, selective extraction is achieved by using the acid concentration gradient and the difference in rare earth complexation characteristics; the electrodialysis membrane separation technology is introduced to establish a dynamic acid solution balance mechanism in the leaching system, and the heavy metals are in-situ solidified by generating silicate colloids with the natural alkaline substances in deep-sea clay; this method fundamentally changes the linear mode of "high consumption - high emission" of the traditional acid leaching method and constructs a self-purification process chain for the deep-sea environment.

[0086] (3) The flotation-leaching combined treatment method for deep-sea rare earth sediments provided by the present invention includes three major synergistic mechanisms: material synergy between classification enrichment and gradient leaching to reduce the subsequent treatment load; energy synergy between microbubble flotation and ultrasonic leaching to improve the interfacial reaction efficiency; ecological synergy between acid solution circulation and clay neutralization to form environmental self-sustaining ability. The multiplication effect generated by this multi-dimensional technology coupling makes the overall efficiency of the system significantly exceed the effect of simple superposition of each unit technology, creating a new mode for the clean development of deep-sea rare earths. Description of the Drawings

[0087] Figure 1 is the flow chart of the flotation-leaching combined treatment method for deep-sea rare earth sediments in Embodiment 1 of the present invention.

[0088] Figure 2 is the schematic diagram of the module connection of the flotation-leaching combined treatment device system for deep-sea rare earth sediments in Embodiment 1 of the present invention. Detailed Embodiments

[0089] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and through specific embodiments.

[0090] The present invention will be further described in detail below. However, the following examples are merely simple examples of the present invention and do not represent or limit the scope of the protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0091] It should be understood that in the description of the present invention, terms such as "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0092] It should be noted that in the description of the present invention, unless otherwise clearly specified and defined, the terms "arranged", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0093] Those skilled in the art should understand that the present invention necessarily includes necessary pipelines, conventional valves, and general pump equipment for realizing the complete process. However, the above contents do not belong to the main inventive points of the present invention. Those skilled in the art can add and arrange them by themselves based on the process flow and equipment structure selection. The present invention has no special requirements and specific limitations on this.

[0094] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0095] Example 1

[0096] This example provides a combined flotation-leaching treatment method for deep-sea rare earth sediments, and its flow chart is as Figure 1 shown. The combined flotation-leaching treatment method for deep-sea rare earth sediments includes the following steps:

[0097] (a) The dehydrated deep-sea rare earth sediments are subjected to desliming screening by a vibrating screen with a screen hole of 5 μm to remove deep-sea clay with a particle size < 5 μm, and pretreated minerals with a particle size ≥ 5 μm are obtained; after screening, the proportion of deep-sea clay is about 40%, and the moisture content of the pretreated minerals is reduced to 50%;

[0098] (b) The pre-treated minerals are classified in a hydrocyclone classifier with a particle size limit of 20 μm, obtaining coarse-grained minerals with a particle size > 20 μm, accounting for 45%, and fine-grained minerals with a particle size of 5 - 20 μm, accounting for 55%; the inlet flow rate of the hydrocyclone classifier is 8 m / s;

[0099] (c) 400 g / t of sodium silicate, 200 g / t of sodium hexametaphosphate and the coarse-grained minerals are mixed, the pulp concentration is adjusted to 18%, and they are injected into a microbubble flotation device for microbubble flotation for 8 min, obtaining a first flotation concentrate with a REO grade of 1.5% and a recovery rate of 62%;

[0100] During the microbubble flotation process, the bubble diameter is 80 μm; a collector is used during the microbubble flotation process; the collector includes H2O5 and XQ107 with a mass ratio of 3:1; the dosage of the collector is 700 g / t of coarse-grained minerals;

[0101] The fine-grained minerals are subjected to nano-collector flotation, obtaining a second flotation concentrate with a REO grade of 1.1% and a recovery rate of 58%;

[0102] The nano-collector is prepared by the following method: H2O5 and SiO2 nanoparticles are mixed at a mass ratio of 1:0.3, and ultrasonic dispersion is carried out for 40 min under the condition of pH = 8 to form a nano-collector with a surface coating structure; the particle size of the SiO2 nanoparticles is 80 nm; the zeta potential of the nano-collector is +25 mV; the dosage of the nano-collector is 80 g / t of fine-grained minerals;

[0103] (d) The first flotation concentrate and the second flotation concentrate are mixed, and then the REO grade reaches 1.3% and the comprehensive recovery rate is 60%; two-stage acid leaching is carried out;

[0104] In the two-stage acid leaching, the first-stage acid leaching uses hydrochloric acid with a concentration of 1.5 mol / L to extract light rare earth elements; the liquid-solid ratio of the first-stage acid leaching is 3:1 (mL / g), the temperature is 45 °C, and the leaching time is 45 min; the leaching rate of light rare earths (La, Ce) is 86%, and the acid consumption is 0.25 t / t of concentrate;

[0105] The second-stage acid leaching uses a mixed acid solution of sulfuric acid and oxalic acid to extract heavy rare earth elements; the leaching rate of heavy rare earths (Y, Dy) reaches 96%; the comprehensive recovery rate of total rare earths: 85% for light rare earths and 95% for heavy rare earths;

[0106] In the second-stage acid leaching, the sulfuric acid concentration is 2.5 mol / L and the oxalic acid concentration is 0.8 mol / L; the pH of the mixed acid solution is 1.2; the temperature of the second-stage acid leaching is 70 °C, the ultrasonic-assisted leaching time is 75 min, the ultrasonic frequency is 30 kHz, and the power density is 0.7 W / cm 3 ;

[0107] The leaching waste liquid is separated and recycled for free acid through electrodialysis membrane, and the residual acid liquid after treatment is mixed and neutralized with the deep-sea clay remaining after sludge removal and screening in step (a) according to a mass ratio of 1:4 to generate a silicate colloid.

[0108] 85% of the free acid is recovered, and the H + recovery rate is 82%. After solidification, the leaching concentrations of heavy metals (As, Pb) in the tailings are 0.08 mg / L and 0.3 mg / L respectively, which are lower than the limits of the Marine Sediment Quality Standard (GB18668-2002) (As ≤ 0.5 mg / L, Pb ≤ 1.0 mg / L).

[0109] This embodiment also provides a combined flotation-leaching treatment device system for deep-sea rare earth sediments. The schematic diagram of the module connection of the device system is as Figure 2 shown. The combined flotation-leaching treatment device system for deep-sea rare earth sediments performs the above-mentioned combined flotation-leaching treatment method for deep-sea rare earth sediments;

[0110] The combined flotation-leaching treatment device system for deep-sea rare earth sediments includes a deep-sea mining integrated interface, a classification flotation module, a gradient acid leaching module, and an acid circulation module connected in sequence;

[0111] The deep-sea mining integrated interface includes a micro-disturbance crawler-type suction head and a hydrocyclone dewatering device connected in sequence; the operating pressure of the micro-disturbance crawler-type suction head is 0.08 MPa; the cone angle of the hydrocyclone dewatering device is 10°; the ceramic inner lining thickness of the hydrocyclone dewatering device is 6 mm, and the pressure resistance is 60 MPa. The moisture content at the outlet of the hydrocyclone dewatering device is 38%, and the volume of the pulp is reduced by 60%.

[0112] The classification flotation module includes a sludge removal and screening device, a hydrocyclone classification device, a microbubble flotation device, and a nano-collector injection device; the sludge removal and screening device and the hydrocyclone classification device are arranged in series; the hydrocyclone classification device is respectively connected to the microbubble flotation device and the nano-collector injection device;

[0113] The gradient acid leaching module includes a first acid leaching reactor and a second acid leaching reactor arranged in parallel; an ultrasonic transducer device is built in the second reactor;

[0114] The acid circulation module includes an electrodialysis stack and a neutralization tank connected in sequence.

[0115] The microbubble flotation device adopts a Venturi tube structure; the bubble generation efficiency in the microbubble flotation device is 6 m 3 / h·m 2 ;

[0116] The pressure of the nano-collector injection device is 0.8 MPa;

[0117] The electrodialysis stack is connected to the gradient acid leaching module through an acid solution reflux pipeline.

[0118] Example 2

[0119] This example provides a combined flotation-leaching treatment method for deep-sea rare earth sediments. The combined flotation-leaching treatment method for deep-sea rare earth sediments is the same as that of Example 1 except that ultrasonic assistance is not carried out in the second-stage acid leaching.

[0120] In this example, since ultrasonic assistance is not carried out in the second-stage acid leaching, the leaching rate of heavy rare earth elements will decrease; furthermore, the overall rare earth comprehensive recovery rate will decrease.

[0121] Example 3

[0122] This example provides a combined flotation-leaching treatment method for deep-sea rare earth sediments. The combined flotation-leaching treatment method for deep-sea rare earth sediments is the same as that of Example 1 except that the liquid-solid ratio in the first-stage acid leaching is 1:1 (mL / g).

[0123] Example 4

[0124] This example provides a combined flotation-leaching treatment method for deep-sea rare earth sediments. The combined flotation-leaching treatment method for deep-sea rare earth sediments is the same as that of Example 1 except that the liquid-solid ratio in the first-stage acid leaching is 7:1 (mL / g).

[0125] From a comprehensive comparison of Example 1 with Example 3 and Example 4, it can be seen that in Example 3, due to the relatively small liquid-solid ratio in the first-stage acid leaching, the mass transfer rate decreases, and the leaching rate of light rare earth elements decreases; in Example 4, due to the relatively large liquid-solid ratio in the first-stage acid leaching, the acid concentration decreases, the reaction rate decreases, and the leaching efficiency of light rare earth elements decreases; the amount of waste liquid will increase, and the subsequent treatment cost will increase.

[0126] Comparative Example 1

[0127] This comparative example provides a combined flotation-leaching treatment method for deep-sea rare earth sediments. The combined flotation-leaching treatment method for deep-sea rare earth sediments is the same as that of Example 1 except that step (b) is not carried out, and all pretreated minerals are directly subjected to step (c) microbubble flotation.

[0128] In this comparative example, since the classification of pretreated minerals is not carried out and all pretreated minerals are directly subjected to microbubble flotation, the flotation effect of the minerals is poor, and the minerals containing rare earths are not well flotated. Then, two-stage acid leaching is continued, and finally the overall rare earth comprehensive recovery rate is greatly reduced.

[0129] Comparative Example 2

[0130] This comparative example provides a deep-sea rare earth sediment flotation-leaching combined treatment method, which is the same as Example 1 except that step (d) adopts primary acid leaching, that is, all flotation concentrates are acid leached only with hydrochloric acid.

[0131] Comparative Example 3

[0132] This comparative example provides a deep-sea rare earth sediment flotation-leaching combined treatment method, which is the same as Example 1 except that step (d) adopts primary acid leaching, that is, all flotation concentrates are acid-leached using only a mixed acid solution with a pH of 1.2 formed by sulfuric acid and oxalic acid.

[0133] It can be seen from Example 1 and Comparative Examples 2 to 3 that in Comparative Example 2, all flotation concentrates were acid-leached with hydrochloric acid only, which resulted in a significant reduction in the leaching rate of heavy rare earth elements; in Comparative Example 3, all flotation concentrates were acid-leached with a mixed acid solution of pH=1.2 formed by sulfuric acid and oxalic acid, which resulted in a significant reduction in the leaching rate of light rare earth elements. Comparative Examples 1 and 2 only used the primary acid leaching method, resulting in a significant reduction in the final total rare earth comprehensive recovery rate.

[0134] In summary, the deep-sea rare earth sediment flotation-leaching combined treatment method provided by the present invention has created a new model for the clean development of deep-sea rare earths through the three-in-one method of "three-level particle size classification-gradient leaching cycle-deep-sea in-situ treatment", and the step-by-step extraction efficiency of light / heavy rare earths is improved by more than 40%; the sorting and leaching loads are linked to reduce by 50%, the ultrasonic enhanced leaching rate is increased by 2.3 times, and the acid-soil cycle reduces the environmental risk by 90%, forming a deep-sea rare earth development method with both efficient recovery and ecological self-sustainability, which is suitable for large-scale promotion and application.

[0135] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A combined flotation-leaching treatment method for deep-sea rare earth sediments, characterized in that, The combined flotation-leaching treatment method for deep-sea rare earth sediments comprises the following steps: (a) Dewatering and screening the deep-sea rare earth sediments to obtain pretreated minerals with a particle size ≥ 5 μm; (b) Classifying the pretreated minerals with a particle size of 20 μm as the boundary to obtain coarse-grained minerals with a particle size > 20 μm and fine-grained minerals with a particle size of 5 - 20 μm; (c) Conducting microbubble flotation on the coarse-grained minerals to obtain a first flotation concentrate; conducting nano-collector flotation on the fine-grained minerals to obtain a second flotation concentrate; (d) Mixing the first flotation concentrate and the second flotation concentrate and conducting two-stage acid leaching. After that, the leaching waste liquid is separated by an electrodialysis membrane to recover free acid, and the treated residual acid liquid is mixed and neutralized with the deep-sea clay remaining after the dewatering and screening in step (a) to generate a silicate colloid; In the two-stage acid leaching, the first-stage acid leaching uses hydrochloric acid with a concentration of 1 - 2 mol / L to extract light rare earth elements; The second-stage acid leaching uses a mixed acid solution with a pH of 1.0 - 1.5 formed by sulfuric acid and oxalic acid to extract heavy rare earth elements.

2. The combined flotation-leaching treatment method for deep-sea rare earth sediments according to claim 1, characterized in that, Before the dewatering and screening in step (a), the deep-sea rare earth sediments are also subjected to dehydration treatment; Preferably, the classification in step (b) is carried out in a hydrocyclone classifier; Preferably, the inlet flow rate of the hydrocyclone classifier is 6 - 9 m / s.

3. The combined flotation-leaching treatment method for deep-sea rare earth sediments according to claim 1 or 2, characterized in that, During the microbubble flotation in step (c), the bubble diameter is 50 - 100 μm; Preferably, a collector is used during the microbubble flotation; Preferably, the collector comprises H2O5 and XQ107 with a mass ratio of 3:1 - 6:1; Preferably, the dosage of the collector is 500 - 700 g / t of coarse-grained minerals, preferably 200 - 300 g / t of coarse-grained minerals; Preferably, an inhibitor is also used during the microbubble flotation; Preferably, the inhibitor comprises sodium silicate and sodium hexametaphosphate with a mass ratio of 1:(0.5 - 2); Preferably, the microbubble flotation is carried out under the condition that the pulp concentration is 15% - 20%; Preferably, the time of the microbubble flotation is 5 - 10 min.

4. The combined flotation and leaching treatment method for deep-sea rare earth sediments according to any one of claims 1 to 3, characterized in that, The nano-collector in step (c) is prepared by the following method: mixing H2O5 and SiO2 nanoparticles with a mass ratio of 1:(0.1 - 0.3), and ultrasonically dispersing for 20 - 40 min under the condition of pH = 8 - 9 to form a nano-collector with a surface coating structure; Preferably, the particle size of the SiO2 nanoparticles < 100 nm; Preferably, the zeta potential of the nano-collector ≥ +20 mV; Preferably, the dosage of the nano-collector is 50 - 100 g / t of fine-grained minerals.

5. The combined flotation-leaching treatment method for deep-sea rare earth sediments according to any one of claims 1 to 4, characterized in that In the first-stage acid leaching in step (d), the liquid-solid ratio is (2 - 5):1 (mL / g), the temperature is 40 - 50 °C, and the leaching time is 30 - 60 min; Preferably, in the second-stage acid leaching, the sulfuric acid concentration is 2 - 3 mol / L, and the oxalic acid concentration is (0.4 - 0.6) mol / L; Preferably, the temperature of the second-stage acid leaching is 60-80 °C, the ultrasonic-assisted leaching time is 60-90 min, the ultrasonic frequency is 20-40 kHz, and the power density is 0.5-1.0 W / cm 3 .

6. The combined flotation-leaching treatment method for deep-sea rare earth sediments according to any one of claims 1 to 5, characterized in that, The electrodialysis membrane in step (d) comprises a perfluorosulfonic acid cation exchange membrane; Preferably, the operating current density of the electrodialysis membrane separation process is 20 - 40 A / m 2 .

7. The combined flotation-leaching treatment method for deep-sea rare earth sediments according to any one of claims 1 to 6, characterized in that, The mass ratio of the residual acid liquid to the deep-sea clay in step (d) for mixing is 1:3 - 1:

5.

8. A combined flotation-leaching treatment device system for deep-sea rare earth sediments, characterized in that, The deep-sea rare earth sediment flotation-leaching combined treatment device system performs the deep-sea rare earth sediment flotation-leaching combined treatment method according to any one of claims 1 to 7; The deep-sea rare earth sediment flotation-leaching combined treatment device system includes a classification flotation module, a gradient acid leaching module, and an acid circulation module connected in sequence; The classification flotation module includes a desliming and screening device, a hydrocyclone classification device, a microbubble flotation device, and a nano-collector spraying device; the desliming and screening device and the hydrocyclone classification device are arranged in series; the hydrocyclone classification device is respectively connected to the microbubble flotation device and the nano-collector spraying device; The gradient acid leaching module includes a first acid leaching reactor and a second acid leaching reactor arranged in parallel; an ultrasonic transducer device is arranged inside the second reactor; The acid circulation module includes an electrodialysis stack and a neutralization tank connected in sequence.

9. The flotation-leaching combined treatment device system for deep-sea rare earth sediments according to claim 8, characterized in that, The microbubble flotation device adopts a Venturi tube structure; Preferably, the bubble generation efficiency in the microbubble flotation device is ≥ 5 m 3 / h·m 2 ; Preferably, the pressure of the nano-collector spraying device is 0.5 to 1.0 MPa; Preferably, the electrodialysis stack is connected to the gradient acid leaching module through an acid liquid reflux pipeline.

10. The flotation-leaching combined treatment device system for deep-sea rare earth sediments according to claim 8 or 9, characterized in that, The deep-sea rare earth sediment flotation-leaching combined treatment device system further includes a deep-sea mining integration interface connected to the classification flotation module; Preferably, the deep-sea mining integration interface includes a micro-disturbance crawler suction head and a hydrocyclone dehydration device connected in sequence; Preferably, the cone angle of the hydrocyclone dehydration device is 10° to 15°; Preferably, the ceramic lining thickness of the hydrocyclone dehydration device is 5 to 8 mm.

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