Method for extracting rare earth elements from coal gangue

Abstract

The present application provides a kind of extraction method of rare earth elements in coal gangue, the extraction method of rare earth elements in coal gangue includes the following steps: S1: crushing screening: after being treated by crusher, screening machine, coarse particle coal gangue is thrown out, and the screened coal gangue is obtained;S2: ball milling: the screened coal gangue is ball milled;S3: acid leaching: the coal gangue after ball milling is continuously treated by acid leaching and solid-liquid separation, and the rare earth leaching solution is obtained.The present application can scale up to consume coal gangue, can directly save high storage cost, and convert environmental benefits into real gold and silver, and lay a foundation for subsequent extraction of aluminum, silicon and other high value-added products.

Description

Technical Field

[0001] This invention relates to the field of rare earth extraction, and specifically to a method for extracting rare earth elements from coal gangue. Background Technology

[0002] Rare earth elements, hailed as "industrial vitamins" and "the mother of new materials," are core raw materials for strategic industries such as new energy, electronics, and aerospace. Although my country is a major rare earth resource country, long-term over-exploitation has led to a decline in its reserve advantage. Coal gangue contains a considerable amount of rare earth elements, and advanced extraction technologies can achieve a rare earth recovery rate of approximately 80%. Mature extraction pathways for valuable elements from coal-based waste have been established abroad. The occurrence forms of rare earth elements in coal gangue are mainly determined by direct methods (scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA)) and indirect methods (stepwise chemical extraction, Tessier continuous chemical extraction, and BCR sequential extraction). Studies show that rare earth elements and heavy rare earth elements exhibit different occurrence differences; extractable rare earth elements exist in acid-soluble mineral forms and organic complexes, while extractable heavy rare earth elements exist almost exclusively in organic complexes.

[0003] In existing technologies, the extraction of rare earth elements from coal gangue presents a fragmented landscape: some employ roasting-activation-acid leaching processes, while others explore multi-metal synergistic recovery. While diverse technical approaches facilitate innovation, the lack of systematic optimization and process barriers leads to technical problems in actual production, such as inconsistent process parameters, significant differences in extraction efficiency, and high risks of secondary pollution. Existing extraction methods lack relatively stable and efficient standardized processes, indicating a significant weakness in the development of the technical system. Existing industry technologies and research systems primarily address the issues of "how to investigate and classify," but the efficient and environmentally friendly "how to extract" remains a technological gap. Furthermore, existing extraction technologies still have shortcomings in achieving high-value utilization, green process design, and pollution control.

[0004] In summary, the existing technology has the following problems: there is a lack of efficient methods for extracting rare earth elements from coal gangue. Summary of the Invention

[0005] This invention provides a method for extracting rare earth elements from coal gangue, thereby solving the problem of low extraction efficiency of rare earth elements from coal gangue.

[0006] Therefore, this invention proposes a method for extracting rare earth elements from coal gangue, the method comprising the following steps:

[0007] S1: Crushing and Screening: The primary coal gangue is processed by a crusher and a screening machine to remove coarse-sized coal gangue, resulting in screened coal gangue.

[0008] S2: Ball milling: ball milling the screened coal gangue;

[0009] S3: Acid leaching: The ball-milled coal gangue is further subjected to acid leaching and solid-liquid separation to obtain rare earth leachate.

[0010] Furthermore, in step S1, a vibrating screen is used for screening.

[0011] Furthermore, in step S1, the particle size of the screened coal gangue is 0.25mm-0.045mm.

[0012] Furthermore, in step S2, a planetary ball mill is used for ball milling.

[0013] Furthermore, in step S3, the acid leaching uses a mixed acid with a concentration of 1.0-5.0 mol / L, wherein the ratio of hydrochloric acid to sulfuric acid is 1:1.

[0014] Further, in step S3, sodium dodecyl sulfonate surfactant with a mass fraction of 0.001%-0.006% is added to the acid solution.

[0015] Furthermore, in step S3, the liquid-to-solid ratio of the acid leaching solution is controlled to be between 8:1 and 12:1.

[0016] Furthermore, in step S3, the acid leaching temperature is controlled within the range of 65°C to 85°C.

[0017] Furthermore, in step S3, the acid immersion soaking time is 2 to 4 hours.

[0018] This invention achieves a total rare earth leaching rate of ≥60%, enabling large-scale disposal of coal gangue, directly saving on high storage costs, and reducing solid waste environmental taxes, thus converting environmental benefits into tangible economic gains. The acid leaching process activates rare earth elements while laying the foundation for subsequent extraction of high-value-added products such as aluminum and silicon. The combined use of main and byproducts to share reagent and energy consumption significantly reduces the marginal cost of rare earth extraction. Attached Figure Description

[0019] Figure 1 This is a flowchart of the rare earth element extraction process from coal gangue according to the present invention. Detailed Implementation

[0020] To provide a clearer understanding of the technical features, objectives, and effects of this invention, the invention is now described.

[0021] This invention proposes a method for extracting rare earth elements from coal gangue, such as... Figure 1 As shown, the method for extracting rare earth elements from coal gangue includes the following steps:

[0022] S1: Crushing and Screening: The primary coal gangue is processed by a crusher and a screening machine to remove coarse-sized coal gangue, resulting in screened coal gangue.

[0023] S2: Ball milling: ball milling the screened coal gangue;

[0024] S3: Acid leaching: The ball-milled coal gangue is further subjected to acid leaching and solid-liquid separation to obtain rare earth leachate.

[0025] Furthermore, in step S1, a vibrating screen is used for screening.

[0026] Furthermore, in step S1, the particle size of the screened coal gangue is 0.25mm-0.045mm.

[0027] Furthermore, in step S2, a planetary ball mill is used for ball milling.

[0028] Furthermore, in step S3, the acid leaching uses a mixed acid with a concentration of 1.0-5.0 mol / L, wherein the ratio of hydrochloric acid to sulfuric acid is 1:1.

[0029] Further, in step S3, sodium dodecyl sulfonate surfactant with a mass fraction of 0.001%-0.006% is added to the acid solution.

[0030] Furthermore, in step S3, the liquid-to-solid ratio of the acid leaching solution is controlled to be between 8:1 and 12:1.

[0031] Furthermore, in step S3, the acid leaching temperature is controlled within the range of 65°C to 85°C.

[0032] Furthermore, in step S3, the acid immersion soaking time is 2 to 4 hours.

[0033] Specifically, the processing method of the present invention includes the following steps:

[0034] 1. Crushing and Screening: The source coal gangue is processed by a crusher and a vibrating screen to remove coarse coal gangue with a diameter greater than 6mm. The screened coal gangue has a particle size range of 0.25mm-0.045mm. This can reduce the ore processing volume by ≥10% and the impurity removal rate by ≥15%.

[0035] 2. Planetary ball mill: To address the problem of tightly packed minerals in fine particles, the high-energy grinding process of the planetary ball mill generates a mechanical force effect in the coal gangue, breaking down the silicate structure in the coal gangue and improving the release efficiency of rare earth elements.

[0036] 3. Enhanced acid leaching: The activated coal gangue sample was further subjected to acid leaching and solid-liquid separation to obtain rare earth leachate. The solid residue was then subjected to harmless treatment.

[0037] Acid leaching uses a mixed acid with a concentration of 1.0-5.0 mol / L, controlling the liquid-solid ratio between 8:1 and 12:1, and the temperature between 65℃ and 85℃. The soaking time is 2 to 4 hours (which can be extended appropriately); the total rare earth leaching rate is ≥60%; the mixed acid is hydrochloric acid: sulfuric acid = 1:1, and the leaching solution mainly contains La, Sm, Ce, Nd, etc.

[0038] If the extraction rate is low, sodium dodecyl sulfate surfactant with a mass fraction of 0.001%-0.006% can be added to the acid solution to improve the wettability of the coal gangue sample (which can increase it by 8%-10%) and ensure that the acid solution can completely penetrate into the microcracks generated by ball milling.

[0039] Table 1. Composition analysis of coal gangue samples from a coal mine.

[0040] Table 2. Rare earth element content in coal gangue (mg / kg)

[0041] Table 1 shows the composition of coal gangue samples from a coal mine in my country, and Table 2 shows the rare earth element content in the coal gangue from the same coal mine. The method of this invention extracts rare earth elements from coal gangue. The acid leaching process activates the rare earth elements and lays the foundation for the subsequent extraction of high value-added products such as aluminum and silicon. The main and by-products are combined to share the reagent and energy consumption, which greatly reduces the marginal cost of rare earth extraction.

[0042] This invention guides related industries towards high efficiency, cleanliness, and economy by systematically optimizing the core parameters and technical indicators of the extraction process. The invention incorporates pollution control during the extraction process and includes integrated treatment steps for wastewater, waste gas, and waste residue, ensuring that rare earth element extraction is carried out under environmental safety conditions. Implementation will promote the establishment of a technical system for the identification and extraction of rare earth elements found in coal gangue, including element occurrence speciation analysis, extractability evaluation, economic value assessment, and a complete extraction process.

[0043] The tailings from the leaching process of this invention can be converted into environmentally friendly building materials or ecological improvers, creating secondary revenue and establishing a closed loop for "zero emissions" of solid waste. Large-scale disposal of coal gangue can directly save on high storage costs and reduce solid waste environmental taxes, converting environmental benefits into tangible economic gains. The recovered medium and heavy rare earth elements, as key national strategic resources, possess strong long-term appreciation potential.

[0044] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. The various components of the present invention can be combined with each other without conflict. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for extracting rare earth elements from coal gangue, characterized in that, The method for extracting rare earth elements from coal gangue includes the following steps: S1: Crushing and Screening: The primary coal gangue is processed by a crusher and a screening machine to remove coarse-sized coal gangue, resulting in screened coal gangue. S2: Ball milling: ball milling the screened coal gangue; S3: Acid leaching: The ball-milled coal gangue is further subjected to acid leaching and solid-liquid separation to obtain rare earth leachate.

2. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S1, a vibrating screen is used for screening.

3. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S1, the particle size of the screened coal gangue is 0.25mm-0.045mm.

4. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S2, a planetary ball mill is used for ball milling.

5. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S3, the acid leaching uses a mixed acid with a concentration of 1.0-5.0 mol / L, in which the ratio of hydrochloric acid to sulfuric acid is 1:

1.

6. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S3, sodium dodecyl sulfonate surfactant with a mass fraction of 0.001%-0.006% is added to the acid solution.

7. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S3, the liquid-to-solid ratio of acid leaching is controlled between 8:1 and 12:

1.

8. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S3, the acid leaching temperature is controlled within the range of 65°C to 85°C.

9. The method for extracting rare earth elements from coal gangue as described in claim 1, characterized in that, In step S3, the acid immersion soaking time is 2 to 4 hours.

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