Pretreatment and valuable element extraction method of deep-sea polymetallic nodule on the seabed

Abstract

The present application belongs to the field of mineral resource processing, and particularly relates to a pretreatment and valuable element extraction method for seafloor polymetallic nodules, which comprises the following steps: rapidly heating and heat-insulating pretreatment of a mixture containing seafloor polymetallic nodules, carbon material and additives by means of electric resistance heating, to obtain pretreated material; wherein the heating rate of rapid heating is 100-500 DEG C / s; the pretreatment temperature is 800-1000 DEG C; and the additives contain at least one of alkali metal salt, alkaline earth metal salt or ammonium salt. The seafloor polymetallic nodules, carbon material and additives are innovatively instantaneously heated and pretreated, which can optimize the physicochemical structure of seafloor polymetallic nodules, and further optimize the subsequent leaching behavior, and improve the extraction rate of valuable elements.

Description

Technical Field

[0001] This invention belongs to the field of metal mineral resource processing, specifically relating to the extraction of valuable elements from deep-sea polymetallic nodules. Background Technology

[0002] Deep-sea polymetallic nodules are rich in valuable metals such as manganese, iron, copper, nickel, and cobalt. They are mainly supported by high-valence manganese oxide / hydroxide phases and iron oxide / hydroxide phases, exhibiting a layered growth structure and complex mineral co-existence. Since manganese primarily exists in the high-valence state of Mn(IV) / Mn(III), Cu, Co, Ni, etc., are often strongly coupled to the manganese-iron oxide framework phase through adsorption, complexation, or isomorphic mechanisms, making this framework phase a typical difficult-to-treat phase. Without controlled reduction to disrupt its structure and promote the conversion of Mn(IV) to Mn(II), valuable metals are difficult to fully release. Conventional leaching exhibits problems such as slow kinetics, high acid consumption, poor selectivity, co-dissolution of impurities, and a heavy burden on subsequent purification.

[0003] For the treatment of polymetallic nodules in the deep sea, existing industrial and laboratory routes can be broadly divided into two categories: pyrometallurgical-hydrometallurgical combined processes and pure hydrometallurgical processes. The pyrometallurgical-hydrometallurgical combined process is represented by the INCO smelting-leaching route: the nodules are reduced, roasted, and smelted in an electric furnace to produce manganese-rich ferromanganese slag and an alloy containing Cu, Ni, and Co. The alloy is then sulfided to form matte, which is leached with sulfuric acid and combined with extraction / electrolysis / hydrogen reduction to separate the metals. The slag can be further used for the production of ferromanganese alloys. Based on this, existing technologies have improved the alloy hydrometallurgical process through steps such as iron precipitation purification. For example, systems such as H₂SO₄–H₂SO₃ are used to selectively dissolve Ni / Co and precipitate Cu as CuS, thereby improving process adaptability and recovery efficiency. Pure wet processes typically use strong acids such as sulfuric acid as a medium, supplemented by reducing agents such as SO2, molasses, and pyrite to achieve the reduction and dissolution of Mn(IV), and combine selective precipitation and ion exchange / solvent extraction to complete metal separation; existing technologies also propose high-pressure sulfuric acid leaching combined with resin separation and sulfide precipitation to achieve cascade recovery.

[0004] However, the fire-wet process generally suffers from high energy consumption, large equipment investment and maintenance costs, and significant process emissions; while the pure wet process often faces challenges such as high acid consumption, severe co-dissolution of impurities, high equipment corrosion and safety pressures, and long reaction times. To achieve the comprehensive goal of "high recovery, low energy consumption, low acid consumption, and low emissions," there is an urgent need for a pretreatment technology that can effectively achieve phase change activation and structural pyrolysis in a very short time, in order to reduce the acidity and time costs of subsequent leaching and reduce the pressure of end-of-pipe treatment. Summary of the Invention

[0005] To address the problems existing in the prior art, the primary objective of this invention is to provide a pretreatment method for deep-sea polymetallic nodules (also referred to as polymetallic nodules or manganese nodules in this invention), which aims to effectively modify the polymetallic nodules and thereby improve the extraction of valuable elements therein.

[0006] The second objective of this invention is to provide a method for extracting valuable elements from deep-sea polymetallic nodules, aiming to effectively improve the extraction efficiency and effectiveness of the metals.

[0007] Valuable metals (Cu, Co, Ni, etc.) in deep-sea polymetallic nodules typically exist in a high-valence manganese iron oxide / hydroxide framework phase via adsorption, complexation, or isomorphic mechanisms. This framework phase is predominantly Mn(IV) and Fe(III), exhibiting stable structure and low reactivity, making it a typical difficult-to-treat phase. Without effective disruption of the high-valence manganese iron oxide structure, valuable metals such as Cu, Co, and Ni are tightly bound to the framework, making it difficult to achieve sufficient dissociation and efficient release through conventional leaching or thermal treatment. This often results in slow leaching kinetics, poor selectivity, and high reagent consumption. To address the characteristics and treatment challenges of deep-sea polymetallic nodules, this invention provides the following solution:

[0008] A pretreatment method for deep-sea polymetallic nodules involves rapidly heating and holding a mixture containing deep-sea polymetallic nodules, carbon materials, and additives using an electric resistance heating method to obtain a pretreated material.

[0009] The rapid heating rate is 100~500℃ / s; the pretreatment temperature is 800~1000℃.

[0010] The additive contains at least one of an alkali metal salt, an alkaline earth metal salt, or an ammonium salt.

[0011] This invention innovatively pre-treats deep-sea polymetallic nodules, carbon materials, and additives with instantaneous heating, which optimizes the physicochemical structure of deep-sea polymetallic nodules, thereby optimizing their subsequent leaching behavior and improving the extraction rate of valuable elements.

[0012] In this invention, the deep-sea polymetallic nodules are nodular mineral aggregates mainly composed of manganese oxide / hydroxide phases and iron oxide / hydroxide phases, exhibiting a concentric layered or banded structure. Preferably, the main elements in the dry basis of the deep-sea polymetallic nodules are Mn, Fe, Cu, Ni, and Co, wherein the Mn content is 5-50 wt%, the Fe content is 2-20 wt%, the Cu content is greater than 0.05 wt%, the Ni content is greater than 0.02 wt%, and the Co content is greater than 0.02 wt%. Further, in the deep-sea polymetallic nodules, the Mn content is 20-45 wt%, the Fe content is 5-100 wt%, the Cu content is 0.1-1.5 wt%, the Ni content is 0.5-1.5 wt%, and the Co content is 0.1-0.5 wt%.

[0013] In this invention, the carbon material is a component containing all-carbon, preferably at least one of graphite powder, activated carbon, or carbon black.

[0014] In the additive, the salt of alkali metal salt, alkaline earth metal salt or ammonium salt can be at least one of the halides or carbonates of their respective cations (alkali metal cation, alkaline earth metal cation, ammonium ion); the halide can be at least one of chloride or bromide.

[0015] In this invention, the additive includes at least one of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, calcium chloride, magnesium chloride, and ammonium chloride.

[0016] In this invention, the additive comprises additive A and additive B, wherein additive A includes at least one of sodium chloride and potassium chloride; and additive B includes at least one of sodium carbonate and potassium carbonate; wherein the mass ratio of additive A to additive B is 1~4:1~4; preferably 1~3:1~3.

[0017] In this invention, the weight ratio of deep-sea polymetallic nodules, carbon materials and additives is 100:(2~15):(0.1~2); preferably 100:5~10:0.5~1.

[0018] In this invention, the rapid heating pretreatment process of the resistance heating is carried out in a graphite instantaneous heating furnace; the average heating rate of the pretreatment is 200~500℃ / s.

[0019] In this invention, the temperature is rapidly increased to 850~1000℃.

[0020] Preferably, the heat preservation pretreatment time is 5~20 s.

[0021] The present invention also provides a method for extracting valuable elements from deep-sea polymetallic nodules. The deep-sea polymetallic nodules are pretreated using the aforementioned pretreatment method to obtain a pretreated material. The pretreated material is then subjected to acid leaching to obtain a leachate containing valuable elements.

[0022] The acid solution used in the pickling process includes aqueous solutions of organic acids and / or inorganic acids;

[0023] Preferably, the inorganic acid includes at least one of hydrochloric acid, nitric acid, or sulfuric acid;

[0024] Preferably, the concentration of hydrogen ions in the acid solution is 0.8~4M.

[0025] The liquid-to-solid ratio during the acid leaching process is 5~20mL / g;

[0026] Preferably, the acid leaching temperature is 50~100℃;

[0027] Preferably, the acid leaching time is 30 minutes to 2 hours.

[0028] Beneficial effects

[0029] This invention innovatively pre-treats deep-sea polymetallic nodules, carbon materials, and additives with instantaneous heating, which optimizes the physicochemical structure of deep-sea polymetallic nodules, thereby optimizing their subsequent leaching behavior and improving the extraction rate of their valuable elements.

[0030] Compared with long-term roasting / reduction or long-term leaching at high acidity, this invention achieves effective activation and valence state control of high-valence manganese iron oxide phases through rapid pretreatment by second-level resistance heating. It can obtain higher leaching rates of Cu, Ni, Co, Mn, etc. under lower acidity and shorter leaching time conditions, thereby reducing energy consumption and acid consumption and reducing the burden of subsequent purification. Attached Figure Description

[0031] Figure 1 The image shows the XRD pattern of the deep-sea polymetallic nodule 1 from Example 1. Detailed Implementation

[0032] XRD pattern of deep-sea polymetallic nodules 1 is shown in the figure. Figure 1 ,like Figure 1 As shown, the X-ray diffraction peaks of manganese nodules are weak, and the main components are amorphous minerals. The presence of manganese hydrous minerals and zeolite minerals can be observed.

[0033] The contents of deep-sea polymetallic nodules 1-3 are shown in Table 1;

[0034]

[0035] Example 1

[0036] (1) Mixing: Crush the deep-sea polymetallic nodule 1 to -100 mesh; add carbon black and additives according to the weight ratio of deep-sea polymetallic nodule 1: carbon material (carbon black): additive = 100: 10: 0.5, and mix well to obtain a mixture; wherein the additive is a compound of additive A and additive B, additive A is sodium chloride, additive B is sodium carbonate, and the mass ratio of A:B is 1:1.

[0037] (2) Pretreatment: The mixture from step (1) is placed in a graphite instantaneous heating furnace and rapidly heated to 900℃ (heating rate of 400±10℃ / s) under resistance heating and held for 10 s to obtain the pretreated product.

[0038] (3) Acid leaching: The pretreated product from step (2) is leached in hydrochloric acid solution. The H+ in the hydrochloric acid solution... + The concentration was 2 mol / L, the liquid-to-solid ratio was 10 mL / g, the leaching temperature was 80℃, and the leaching time was 1 h.

[0039] (4) Results: The leaching rates of Ni, Co, Mn, Fe and Cu were 99.76%, 99.76%, 99.89%, 99.88% and 99.97%, respectively.

[0040] Comparative Example 1

[0041] Compared with Example 1, the only difference is that in step (2), the heating method is conventional electric heating, the heating temperature is 900℃, the heating rate is 10℃ / s, and the holding time is 2h; the other conditions are the same.

[0042] The leaching results were as follows: Ni, Co, Mn, Fe, and Cu leaching rates were 95.25%, 94.61%, 91.37%, 95.48%, and 96.17%, respectively.

[0043] Comparative Example 2

[0044] Compared with Example 1, the only difference is that no additives were added in step (1), while the other operations and parameters are the same as in Example 1.

[0045] The leaching effect was that the leaching rates of Ni, Co, Mn, Fe and Cu were 91.35%, 90.27%, 88.59%, 90.44% and 92.05%, respectively.

[0046] Example 2

[0047] Compared with Example 1, the only difference is that in step (1), additive B (sodium carbonate) is used as the additive, and the total amount of additive and other operations and parameters are the same as in Example 1.

[0048] The leaching effect was that the leaching rates of Ni, Co, Mn, Fe and Cu were 96.21%, 95.58%, 93.28%, 97.17% and 96.05%, respectively.

[0049] Example 3

[0050] Compared with Example 1, the only difference is that the additive is only additive A, and the total amount of additive and other operations and parameters are the same as in Example 1.

[0051] The leaching results were as follows: Ni, Co, Mn, Fe, and Cu leaching rates were 97.22%, 96.15%, 94.31%, 97.61%, and 97.11%, respectively.

[0052] As can be seen from Examples 1-3, the use of combined additives can unexpectedly achieve better synergy, which helps to obtain better treatment results.

[0053] Example 4

[0054] Compared with Example 1, the only difference is that the ratio of deep-sea polymetallic nodules 1: carbon material (carbon black): additives is 100:8:0.8, the pretreatment temperature is 950℃ (heating rate is 350±10℃ / s), the holding time is 15s, and other operations and parameters are the same as in Example 1.

[0055] The leaching effect was that the leaching rates of Ni, Co, Mn, Fe and Cu were 99.12%, 99.69%, 98.99%, 98.63% and 99.95%, respectively.

[0056] Example 5

[0057] (1) Mixing: Crush the deep-sea polymetallic nodules 2 to -100 mesh; add carbon black and additives according to the weight ratio of deep-sea polymetallic nodules: carbon materials: additives = 100: 5: 0.5, and mix well; wherein the additives are a compound of additives A and additives B, additives A is sodium chloride, additives B is potassium carbonate, and the mass ratio of A:B is 1:3.

[0058] (2) Pretreatment: The temperature is rapidly increased to 1000℃ in a graphite instantaneous heating furnace by resistance heating (heating rate is 300±10℃ / s) and held for 5 s.

[0059] (3) Acid leaching: Leaching is carried out using sulfuric acid solution. The H+ of the sulfuric acid solution... + The concentration was 4 mol / L, the liquid-to-solid ratio was 5 mL / g, the leaching temperature was 100℃, and the leaching time was 0.5 h.

[0060] (4) Results: The leaching rates of Ni, Co, Mn, Fe and Cu were 99.98%, 99.47%, 99.60%, 99.68% and 99.14%, respectively.

[0061] Comparative Example 3

[0062] Compared to Example 5, the only difference is that the pretreatment method is changed to conventional long-term carbothermal reduction: the reduction temperature is 600℃, the heating rate is 15℃ / s, and the holding time is 4 h; in addition, in step 3, the leaching stage uses sulfuric acid H + The concentration was increased to 7 mol / L and the leaching time was extended to 2 h.

[0063] Results: The leaching rates of Ni, Co, Mn, Fe, and Cu were 99.14%, 99.62%, 67.94%, 87.62%, and 93.24%, respectively.

[0064] As can be seen from Example 5 and Comparative Example 3, even with extended reduction time and increased acid leaching concentration and time, the synchronous recovery effect of valuable elements is not as good as the solution of the present invention.

[0065] Example 6

[0066] (1) Mixing: Crush the deep-sea polymetallic nodules 3 to -100 mesh; add carbon black and additives according to the weight ratio of deep-sea polymetallic nodules: carbon materials: additives = 100: 2: 0.5, and mix well; wherein the additives are a compound of additives A and additives B, additives A is sodium chloride, additives B is sodium carbonate, and the mass ratio of additives A to additives B is 2: 1.

[0067] (2) Pretreatment: The temperature is rapidly increased to 800℃ in a graphite instantaneous heating furnace by resistance heating (heating rate is 250±10℃ / s) and held for 20 s.

[0068] (3) Acid leaching: Leaching is carried out using sulfuric acid solution. The H+ of the sulfuric acid solution... + The concentration was 1 mol / L, the liquid-to-solid ratio was 15 mL / g, the leaching temperature was 100℃, and the leaching time was 1 h.

[0069] (4) Results: The leaching rates of Ni, Co, Mn, Fe and Cu were 99.36%, 99.93%, 95.14%, 97.92% and 99.88%, respectively.

[0070] Comparative Example 4

[0071] Compared with Example 6, the only difference is that in step (1), the pretreatment method is changed to conventional long-term carbothermal reduction: the reduction temperature is 1000℃ (heating rate is 10℃ / s), and the holding time at the reduction temperature is 3 h. In addition, in step (3), the leaching time is extended to 2 h; the other conditions are the same. Results: The leaching rates of Ni, Co, Mn, Fe, and Cu are 90.83%, 92.73%, 74.52%, 68.81%, and 96.12%, respectively.

[0072] This invention innovatively pre-treats deep-sea polymetallic nodules, carbon materials, and additives with instantaneous heating, which optimizes the physicochemical structure of deep-sea polymetallic nodules, thereby optimizing their subsequent leaching behavior and improving the extraction rate of their valuable elements.

Claims

1. A pretreatment method for deep-sea polymetallic nodules, characterized in that, A mixture containing deep-sea polymetallic nodules, carbon materials, and additives was rapidly heated and kept at a constant temperature to obtain a pretreated material by using an electric resistance heating method. The rapid heating rate is 100~500 ℃ / s; the pretreatment temperature is 800~1000℃; and the heat preservation pretreatment time is 5~20 s. The additives include at least one of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, calcium chloride, magnesium chloride, and ammonium chloride.

2. The pretreatment method for deep-sea polymetallic nodules as described in claim 1, characterized in that, The deep-sea polymetallic nodules contain 5-50 wt% Mn, 2-20 wt% Fe, greater than 0.05 wt% Cu, greater than 0.02 wt% Ni, and greater than 0.02 wt% Co.

3. The pretreatment method for deep-sea polymetallic nodules as described in claim 1, characterized in that, The carbon material is at least one of graphite powder, activated carbon, or carbon black.

4. The pretreatment method for deep-sea polymetallic nodules as described in claim 1, characterized in that, The additives include additive A and additive B; Additive A includes at least one of sodium chloride and potassium chloride; Additive B includes at least one of sodium carbonate and potassium carbonate; The mass ratio of additive A to additive B is 1~4:1~4.

5. The pretreatment method for deep-sea polymetallic nodules as described in any one of claims 1 to 4, characterized in that, The weight ratio of deep-sea polymetallic nodules, carbon materials, and additives is 100:(2~15):(0.1~2).

6. The pretreatment method for deep-sea polymetallic nodules as described in claim 1, characterized in that, Electrical resistance heating is carried out in a graphite instantaneous heating furnace.

7. A method for extracting valuable elements from deep-sea polymetallic nodules, characterized in that, The deep-sea polymetallic nodules are pretreated using the pretreatment method described in any one of claims 1 to 6 to obtain pretreated material; The pretreated material is subjected to acid leaching to obtain a leachate containing valuable elements.

8. The method for extracting valuable elements from deep-sea polymetallic nodules as described in claim 7, characterized in that, The acid solution used in the pickling process includes aqueous solutions of organic acids and / or inorganic acids; The hydrogen ion concentration in the acid solution is 0.8~4 M.

9. The method for extracting valuable elements from deep-sea polymetallic nodules as described in claim 7 or 8, characterized in that, The liquid-to-solid ratio during the acid leaching process is 5~20 mL / g; The acid leaching temperature is 50~100℃; The acid leaching time is 30 min to 2 h.

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