A method for recovering humic acid from phosphogypsum

Abstract

The application relates to a method for recovering humic acid from phosphogypsum, belonging to the technical field of humic acid separation and extraction, and the steps are as follows: after phosphogypsum is fully extracted and pretreated in a gypsum phase, tailings obtained are used as raw materials without crushing and screening; the raw materials are configured into a slurry with water, ammonia solution is used as a leaching agent for mixing, heating and stirring, humic acid in the raw materials is dissolved in the ammonia solution, stirring and leaching are carried out, then solid-liquid separation is carried out in a vacuum filtration mode, the obtained solid phase is insoluble tailings, and the filtrate is an ammonium humate solution; the obtained ammonium humate solution is evaporated and concentrated, then cooled and crystallized, centrifugal filtration is carried out to obtain an ammonium humate product and a solution after crystallization, and the solution after crystallization is returned and used as a leaching agent for recycling. The application has high practicability, does not generate waste liquid, is a clean humic acid extraction method with wide application prospect, and can solve the problem that the residual organic phase in the current phosphogypsum is difficult to comprehensively utilize.

Description

Technical Field

[0001] This invention belongs to the field of humic acid separation and extraction technology, specifically relating to a method for recovering humic acid from phosphogypsum. Background Technology

[0002] Humic acid is a complex natural organic substance accumulated from plant and animal remains through microbial decomposition and geochemical processes. Its acidic functional groups, such as carboxyl and phenolic hydroxyl groups, have the ability to complex metal ions, significantly enhancing their bioavailability. my country is rich in humic acid resources, with large reserves, wide distribution, and high quality. As an organic raw material, it is widely used in agriculture, chemical industry, building materials, medicine, and other fields.

[0003] In the comprehensive utilization of humic acid, it is commonly added during the phosphate rock beneficiation process to enhance the composition of apatite. Humic acid and its salts can be used as inhibitors. For example, in the flotation separation of apatite from other minerals, sodium humate can inhibit the flotation of certain gangue or impurity minerals, increasing the difference in floatability between apatite and these minerals, making apatite easier to float and improving the grade of the apatite concentrate. In the phosphate rock beneficiation process, humic acid can also be used as a selective flocculant. It selectively adsorbs onto the surface of apatite particles, causing flocculation, while having a weaker flocculation effect on other minerals. This agglomerates the apatite particles together, facilitating subsequent separation and enrichment, and helping to improve the recovery efficiency of apatite. Therefore, in the process of producing phosphoric acid from phosphate concentrate, humic acid usually enters phosphogypsum entirely, resulting in a humic acid content of over 4%, an amorphous SiO2 content of over 8%, and an unreacted apatite content of approximately 5%, and in some cases even exceeding 10%. This significantly improves the utilization rate of humic acid, SiO2, and apatite in the impurity phase. However, no patents or literature have been reported regarding the recovery of humic acid from phosphogypsum.

[0004] Because humic acid can neutralize with ammonia, converting water-insoluble humic acid into water-soluble ammonium humate salts, this invention utilizes ammonia leaching technology to extract humic acid from the tailings after phosphogypsum extraction using an ammonia solution. The humic acid is released as ammonium humate salts, which are then concentrated, crystallized, and separated to obtain the ammonium humate product. This provides assistance for the comprehensive utilization of phosphogypsum resources.

[0005] In summary, after extracting the gypsum phase from phosphogypsum, the resource utilization of the tailings becomes a technical bottleneck restricting the clean and comprehensive utilization of phosphogypsum. The tailings mainly consist of apatite, amorphous SiO2, and humic acid. Therefore, how to realize their resource utilization is of great practical significance for phosphogypsum. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for recovering humic acid from phosphogypsum. This method is used to extract the organic phase from the remaining tailings (apatite, amorphous SiO2, and humic acid) after the gypsum phase is extracted from phosphogypsum, thereby solving the problem of resource utilization and high-value utilization of humic acid. The process is not only short and low-cost, but also environmentally friendly.

[0007] The main objective of this invention is achieved through the following approach:

[0008] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0009] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained from the phosphogypsum do not need to be crushed or sieved and can be used as raw materials for future use.

[0010] S2. Prepare a slurry by mixing the raw materials with water, then use an ammonia solution as a leaching agent to mix, heat and stir, and then stir to leach the humic acid in the raw materials after it dissolves in the ammonia solution.

[0011] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, and the filtrate is ammonium humate solution.

[0012] S4. The obtained ammonium humate solution is evaporated and concentrated, then cooled and crystallized. After centrifugation and filtration, the ammonium humate product and the crystallized solution are obtained. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0013] in:

[0014] In step S1, the tailings composition, by mass fraction, includes 5%–15% humic acid, 10%–20% apatite, 60%–80% SiO2, and the remaining 5% is organic matter.

[0015] In step S2, the solid-liquid ratio of the raw material to water is 1:(4-10)g / mL, and the mass percentage concentration of the ammonia solution is 5%-15%.

[0016] In step S2, the heating temperature is 20℃~50℃, the stirring speed is 45r / min~120r / min, and the stirring time is 10min~60min.

[0017] In step S2, the leaching temperature for stirring is 20℃~50℃, the leaching time is 20min~60min, the pH value of the solution after leaching is controlled to be 8~9, and the humic acid leaching rate in the tailings is ≥99%.

[0018] In step S3, the insoluble tailings are specifically composed of a silicon-rich phase and a phosphorus-rich phase.

[0019] In step S4, the ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 30% to 40%, the temperature during cooling and crystallization is 10℃ to 20℃, and the stirring speed during centrifugation filtration is 30r / min to 90r / min.

[0020] The ammonium humate product meets the industry standard requirements HG1-1143-78. For the first-grade product, the dry basis content of water-soluble humic acid is not less than 35%, and the dry basis content of available nitrogen is not less than 4%. For the second-grade product, the dry basis content of water-soluble humic acid is not less than 25%, the dry basis content of available nitrogen is not less than 3%, and the recovery rate of humic acid in phosphogypsum tailings is ≥98%.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] (1) The technology provided by this invention saves energy and reduces pollution. Hydrometallurgy is mainly divided into acid leaching and ammonia leaching. Compared with acid leaching, ammonia leaching of this invention has the advantages of good selectivity and low production cost. The tailings separated can be released in the form of ammonium humate through ammonia leaching.

[0023] (2) The present invention uses a direct extraction and separation method to obtain humic acid, which is simple in steps, has a short production cycle, and has a high leaching rate and extraction rate of humic acid in the tailings.

[0024] (3) This invention is based on chemical extraction and utilizes ammonia leaching technology. By controlling the process regime, the leaching rate of humic acid is improved, enabling efficient recovery and utilization of humic acid in phosphogypsum tailings and obtaining high-quality ammonium humate products. The technology provided by this invention is highly practical and generates no waste liquid. It is a clean method for extracting humic acid with broad application prospects and can solve the current problem of the difficulty in comprehensive utilization of residual organic phases in phosphogypsum. Attached Figure Description

[0025] Figure 1 A process flow diagram for recovering humic acid from phosphogypsum according to the present invention. Detailed Implementation

[0026] To make the technical solution, creative purpose and advantages of the present invention clearer, the present invention will be further described below with reference to specific embodiments.

[0027] Example 1

[0028] A method for recovering humic acid from phosphogypsum, the process flow diagram of which is shown below. Figure 1 As shown, the specific steps include:

[0029] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1. by mass fraction include 5% humic acid, 10% apatite and 80% SiO2, and the remaining 5% is organic matter. It does not need to be crushed or screened and can be used as raw material.

[0030] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:4 g / mL. Then, at 50°C, a 15% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 60 minutes at a stirring speed of 120 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 50°C for 20 minutes. The pH of the leached solution was controlled to be 8.5. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.31%.

[0031] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0032] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 35%, and then cooled and crystallized at 20°C. Ammonium humate crystals precipitate in the solution. After centrifugation and filtration, the ammonium humate product and the crystallized solution are obtained. The stirring speed of the centrifugation filtration is 90 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0033] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 41.4%, the dry basis content of available nitrogen is 4.5%, and the recovery rate of humic acid in phosphogypsum tailings is 98.64%.

[0034] Example 2

[0035] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0036] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1. by mass fraction include 6% humic acid, 10% apatite and 79% SiO2, and the remaining 5% is organic matter. It does not need to be crushed or screened and can be used as raw material.

[0037] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:8 g / mL. Then, at 40°C, a 14% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 20 minutes at a stirring speed of 100 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 40°C for 25 minutes. The pH of the leached solution was controlled to be 8. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.64%.

[0038] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0039] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 40%, and then cooled and crystallized at 18°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 50 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0040] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 38.8%, the dry basis content of available nitrogen is 4.2%, and the recovery rate of humic acid in phosphogypsum tailings is 98.93%.

[0041] Example 3

[0042] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0043] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1. are composed of 8% humic acid, 12% apatite and 75% SiO2 by mass fraction, and the remaining 5% is organic matter. They do not need to be crushed or screened and can be used as raw materials.

[0044] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:6 g / mL. Then, at 45°C, a 12% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 10 minutes at a stirring speed of 90 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 45°C for 30 minutes. The pH of the leached solution was controlled to be 9. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.16%.

[0045] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0046] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 30%, and then cooled and crystallized at 20°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 40 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0047] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 36.5%, the dry basis content of available nitrogen is 5.6%, and the recovery rate of humic acid in phosphogypsum tailings is 99.25%.

[0048] Example 4

[0049] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0050] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1.Phosphogypsum, by mass fraction, include 9% humic acid, 18% apatite and 68% SiO2, with the remaining 5% being organic matter. It does not require crushing or sieving and can be used as raw material.

[0051] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:10 g / mL. Then, at 40°C, a 10% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 35 minutes at a stirring speed of 80 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 40°C for 35 minutes. The pH of the leached solution was controlled to be 8. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.53%.

[0052] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0053] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 35%, and then cooled and crystallized at 15°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 80 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0054] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 37.1%, the dry basis content of available nitrogen is 6.1%, and the recovery rate of humic acid in phosphogypsum tailings is 98.52%.

[0055] Example 5

[0056] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0057] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1.Phosphogypsum, by mass fraction, include 10% humic acid, 14% apatite and 71% SiO2, with the remaining 5% being organic matter. It does not require crushing or sieving and can be used as raw material.

[0058] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:8 g / mL. Then, at 35°C, a 9% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 30 minutes at a stirring speed of 70 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 35°C for 40 minutes. The pH of the leached solution was controlled to be 8.5. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.42%.

[0059] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0060] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 30%, and then cooled and crystallized at 15°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 60 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0061] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 39.8%, the dry basis content of available nitrogen is 4.7%, and the recovery rate of humic acid in phosphogypsum tailings is 99.41%.

[0062] Example 6

[0063] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0064] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1. by mass fraction include 12% humic acid, 13% apatite and 70% SiO2, and the remaining 5% is organic matter. It does not need to be crushed or screened and can be used as raw material.

[0065] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:6 g / mL. Then, at 30°C, an 8% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 50 minutes at a stirring speed of 60 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 30°C for 45 minutes. The pH of the leached solution was controlled to be 9. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.71%.

[0066] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0067] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 40%, and then cooled and crystallized at 20°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of the centrifugation and filtration is 40 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0068] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 35.7%, the dry basis content of available nitrogen is 5.9%, and the recovery rate of humic acid in phosphogypsum tailings is 98.39%.

[0069] Example 7

[0070] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0071] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1.Phosphogypsum, by mass fraction, include 14% humic acid, 16% apatite and 65% SiO2, with the remaining 5% being organic matter. It does not require crushing or sieving and can be used as raw material.

[0072] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:4 g / mL. Then, at 50°C, a 10% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 15 minutes at a stirring speed of 50 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 50°C for 40 minutes. The pH of the leached solution was controlled to be 8.5. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.37%.

[0073] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0074] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 35%, and then cooled and crystallized at 10°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 30 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0075] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 40.6%, the dry basis content of available nitrogen is 6.4%, and the recovery rate of humic acid in phosphogypsum tailings is 99.16%.

[0076] Example 8

[0077] A method for recovering humic acid from phosphogypsum specifically includes the following steps:

[0078] S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained by S1.Phosphogypsum, by mass fraction, include 15% humic acid, 20% apatite and 60% SiO2, with the remaining 5% being organic matter. It does not require crushing or sieving and can be used as raw material.

[0079] S2. The raw materials and water were mixed to form a slurry with a solid-liquid ratio of 1:10 g / mL. Then, at 20°C, a 5% (w / w) ammonia solution was added dropwise as the leaching agent, and the mixture was stirred for 40 minutes at a stirring speed of 60 r / min. After the humic acid in the raw materials dissolved in the ammonia solution, leaching was carried out at 20°C for 60 minutes. The pH of the leached solution was controlled to be 8. Under these conditions, the humic acid reacted fully with the ammonia solution to form an ammonium humate solution. The humic acid leaching rate in the tailings was 99.25%.

[0080] S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, specifically composed of silicon-rich and phosphorus-rich phases. The filtrate is an ammonium humate solution.

[0081] S4. The obtained ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 40%, and then cooled and crystallized at 15°C. The ammonium humate product and the crystallized solution are obtained by centrifugation and filtration. The stirring speed of centrifugation and filtration is 50 r / min. The crystallized solution is returned to step S2 as a leaching agent for recycling.

[0082] The obtained ammonium humate product meets the industry standard requirements HG1-1143-78. The dry basis content of water-soluble humic acid in the product is 37.9%, the dry basis content of available nitrogen is 5.3%, and the recovery rate of humic acid in phosphogypsum tailings is 98.47%.

Claims

1. A method for recovering humic acid from phosphogypsum, characterized in that, Specifically, the following steps are included: S1. After the gypsum phase is fully extracted and pretreated, the tailings obtained from the phosphogypsum do not need to be crushed or sieved, and can be used as raw material for future use; The tailings consist of 5% to 15% humic acid, 10% to 20% apatite, 60% to 80% SiO2, and 5% organic matter by mass fraction. S2. Prepare a slurry by mixing the raw materials with water, then use an ammonia solution as a leaching agent to mix, heat and stir, and then stir to leach the humic acid in the raw materials after it dissolves in the ammonia solution. S3. After leaching, solid-liquid separation is carried out by vacuum filtration. The resulting solid phase is insoluble tailings, and the filtrate is ammonium humate solution. S4. The obtained ammonium humate solution is evaporated and concentrated, then cooled and crystallized. After centrifugation and filtration, the ammonium humate product and the crystallized solution are obtained. The crystallized solution is returned to step S2 as a leaching agent for recycling.

2. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, In step S2, the solid-liquid ratio of the raw material to water is 1:(4~10) g / mL, and the mass percentage concentration of the ammonia solution is 5%~15%.

3. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, In step S2, the heating temperature is 20℃~50℃, the stirring speed is 45 r / min~120 r / min, and the stirring time is 10 min~60 min.

4. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, In step S2, the leaching temperature for stirring is 20℃~50℃, the leaching time is 20 min~60 min, the pH value of the solution after leaching is controlled to be 8~9, and the humic acid leaching rate in the tailings is ≥99%.

5. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, In step S3, the insoluble tailings consist of a silicon-rich phase and a phosphorus-rich phase.

6. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, In step S4, the ammonium humate solution is evaporated and concentrated to a mass percentage concentration of 30%~40%, the temperature during cooling and crystallization is 10℃~20℃, and the stirring speed during centrifugation filtration is 30 r / min~90 r / min.

7. The method for recovering humic acid from phosphogypsum according to claim 1, characterized in that, The ammonium humate product meets the national industry standard requirements HG1-1143-78. For the first-grade product, the dry basis content of water-soluble humic acid is not less than 35%, and the dry basis content of available nitrogen is not less than 4%. For the second-grade product, the dry basis content of water-soluble humic acid is not less than 25%, and the dry basis content of available nitrogen is not less than 3%. The recovery rate of humic acid in phosphogypsum tailings is ≥98%.

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