阅读说明：本技术 一种高效浸出磷石膏中有价金属杂质并制备高附加值石膏产品的方法 (Method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high-added-value gypsum product ) 是由 管青军 余伟健 卜勇杰 王平 于 2020-06-22 设计创作，主要内容包括：本发明涉及磷石膏的低成本高附加值的综合利用方法,涉及一种用硫酸高效浸出有价金属杂质的同时制备高品质高附加值α-半水石膏的方法。通过优化工艺条件及添加活性添加剂,使磷石膏通过溶解-重结晶形成α-半水石膏,在此过程的溶解过程中磷石膏晶格中的有价金属杂质元素被完全释放出来,同时在重结晶过程中通过调控α-半水石膏的晶体形貌和粒度,降低释放出来的金属元素和α-半水石膏的共晶和吸附作用,促进其向液相中富集,使有价金属杂质的浸出率达到80％以上,同时制备出高品质的石膏产品。本发明实现了磷石膏中有价金属杂质元素高效分离工艺和高品质石膏产品生产工艺的有效结合。(The invention relates to a low-cost high-added-value comprehensive utilization method of phosphogypsum, and relates to a method for efficiently leaching valuable metal impurities by using sulfuric acid and simultaneously preparing high-quality high-added-value alpha-hemihydrate gypsum. By optimizing process conditions and adding an active additive, phosphogypsum forms alpha-semi-hydrated gypsum through dissolution and recrystallization, valuable metal impurity elements in crystal lattices of the phosphogypsum are completely released in the dissolution process, and eutectic and adsorption effects of the released metal elements and the alpha-semi-hydrated gypsum are reduced by regulating and controlling the crystal morphology and the granularity of the alpha-semi-hydrated gypsum in the recrystallization process, so that the enrichment of the released metal elements and the alpha-semi-hydrated gypsum into a liquid phase is promoted, the leaching rate of the valuable metal impurities reaches more than 80 percent, and meanwhile, a high-quality gypsum product is prepared. The invention realizes the effective combination of the high-efficiency separation process of valuable metal impurity elements in the phosphogypsum and the production process of high-quality gypsum products.)

1. A method for efficiently leaching valuable metal impurities in phosphogypsum and preparing a gypsum product with high added value is characterized by comprising the following steps: placing phosphogypsum in sulfuric acid solution containing active additive, and leaching at 90 deg.C or above; after leaching, carrying out solid-liquid separation to obtain a solid and a liquid; washing the solid with water and drying to obtain alpha-semi-hydrated gypsum; the active additive is at least one of a surfactant, a polymer or an organic phosphorus scale and corrosion inhibitor, wherein the surfactant is selected from at least one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide, the polymer is selected from at least one of polyacrylic acid, polyacrylamide, polyethylene glycol and polyvinyl alcohol, the organic phosphorus scale and corrosion inhibitor is selected from at least one of amino trimethylene phosphonic acid, hydroxy ethylidene diphosphonic acid, ethylene diamine tetra methylene phosphonic acid, diethylene triamine pentamethylene phosphonic acid, 2-phosphonic acid butane-1, 2, 4-tricarboxylic acid, polyol phosphate, 2-hydroxy phosphonoacetic acid, hexamethylene diamine tetramethylidene phosphonic acid, polyamino polyether methylene phosphonic acid and bis 1,6 hexamethylene triamine pentamethylene phosphonic acid, and preferably at least one of the polymer or the organic phosphorus scale and corrosion inhibitor, more preferably at least one of aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid.

In the process of leaching valuable metal impurities in phosphogypsum, the leaching rate of the valuable metal impurities is improved by controlling the process conditions and adding the active additive, and a high-quality gypsum product is prepared.

2. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 1 is characterized in that: the method comprises the following specific steps:

(1) adding phosphogypsum into a sulfuric acid aqueous solution, and uniformly mixing to form phosphogypsum suspension slurry;

(2) adding active additive into the phosphogypsum suspension slurry, heating to 90-115 ℃, and stirring for reaction at the temperature;

(3) after reacting for a period of time, carrying out solid-liquid separation on the suspension slurry while the suspension slurry is hot, washing the separated solid phase with boiling water and drying to obtain the alpha-semi-hydrated gypsum, wherein the separated liquid phase is a sulfuric acid solution containing valuable metals, and the leaching rate of the valuable metal impurities in the phosphogypsum can reach more than 80%.

3. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the mass percentage of the calcium sulfate dihydrate in the phosphogypsum main body is more than or equal to 90 percent.

4. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the mass fraction of the sulfuric acid in the sulfuric acid solution is 12-40%, preferably 15-25%.

5. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the solid content (mass percentage content) of the phosphogypsum suspension slurry is 1-25%, preferably 10-20%.

6. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the dosage of the additive is 0.0001 wt% -0.5 wt%, preferably 0.001 wt% -0.05 wt% of the weight of the phosphogypsum.

7. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the stirring reaction temperature is 90-110 ℃, preferably 95-100 ℃.

8. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: the stirring reaction time is 1-24h, and the stirring speed is 50-300 rpm.

9. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that:

the alpha-semi-hydrated gypsum is short column-shaped alpha-semi-hydrated gypsum;

the valuable metal is at least one of rare earth elements, Cr, Cd and Ni.

10. The method for efficiently leaching valuable metal impurities in phosphogypsum and preparing high value-added gypsum products according to claim 2 is characterized in that: and (4) returning the liquid phase separated in the step (3) to the step (1) for use so as to further enrich the concentration of the valuable metals in the liquid phase and facilitate the subsequent purification and recovery of the valuable metals.

Technical Field

The invention relates to a low-cost high-added-value comprehensive utilization method of phosphogypsum, relates to a method for leaching valuable metal impurities in the phosphogypsum by using sulfuric acid and simultaneously preparing a high-added-value gypsum product, and particularly relates to a method for efficiently leaching the valuable metal impurities by using the sulfuric acid and simultaneously preparing high-quality high-added-value alpha-hemihydrate gypsum.

Background

Phosphogypsum is a large amount of industrial solid waste generated in the wet-process phosphoric acid production process, and is used for producing 1 ton of phosphoric acid (P)₂O₅) About 5 tons of phosphogypsum are discharged. The global annual emission of phosphogypsum is about 2.8 hundred million tons, wherein the annual average emission of China reaches 7000 million tons. The high impurity content of the phosphogypsum leads the comprehensive utilization rate to be low, only 15 percent of the phosphogypsum is recycled at present, the accumulated stacking quantity of the phosphogypsum in China in recent years exceeds 5 hundred million tons, and the total stacking quantity of the phosphogypsum in the whole world is estimated to be 70 to 80 hundred million tons by 2025 years. Therefore, how to further improve the utilization rate of the phosphogypsum becomes a problem to be solved urgently.

At present, phosphogypsum products with low added value are the main way to consume phosphogypsum. On one hand, due to the characteristics of the degree of primary treatment and low added value, the utilization range, the economy, the transportation radius and the like of the phosphogypsum products are severely restricted; on the other hand, although the phosphogypsum products are generally pretreated, the soluble phosphorus, fluorine and organic matters in the phosphogypsum products are only eliminated, but the influence on low-content heavy metals (Cr, Cd, Ni and the like) and high-value rare earth in the phosphogypsum products is not large, the quality and the utilization range of the phosphogypsum products are seriously influenced by the existence of the metal impurities, and the metal resources are greatly wasted. Taking rare earth as an example, in nature, besides various rare earth minerals, a considerable part of rare earth elements exist in the rare earth minerals and are symbiotic with phosphorite. The total reserve of world phosphorite is about 1000 hundred million tons, which is estimated according to the average content of rare earth as 0.05%, the total reserve of associated rare earth in the world phosphorite is 5000 ten thousand tons, and more than 70% of rare earth is enriched in phosphogypsum in the process of producing phosphoric acid by the phosphorite wet method, so the phosphogypsum is an important rare earth secondary resource.

The method for preparing the alpha-hemihydrate gypsum with high added value by using the phosphogypsum is an important way for improving the utilization rate of the alpha-hemihydrate gypsum. The alpha-semi-hydrated gypsum crystal is in a hexagonal bipyramidal columnar shape, has complete crystal development and compact structure, particularly short columnar alpha-semi-hydrated gypsum, has the advantages of low water requirement for standard consistency, small hydration heat, high mechanical strength and the like, and is widely applied to the fields of ceramic grinding tools, precision casting, dental ultra-hard gypsum, artistic articles and the like.

The current research only focuses on leaching separation of valuable metals such as rare earth in phosphogypsum (such as patent CN101451200A) or only focuses on preparing alpha-hemihydrate gypsum (CN107746195A, CN111003723A) by using the phosphogypsum, but both of the researches have some problems to be solved in the practical operation process:

1) the grade of valuable metals in the phosphogypsum is often lower (0.01-0.40 wt% in terms of rare earth oxide for example), the independent extraction has no cost advantage, the leaching efficiency is not high, the leaching rate is generally lower than 60%, and meanwhile, the leached solid is still a gypsum product with low added value.

2) Although phosphogypsum is usually pretreated before the alpha-hemihydrate gypsum is prepared, the pretreatment has little influence on metal impurity elements contained in the phosphogypsum, and the existence of the impurities can seriously influence the quality of an alpha-hemihydrate gypsum product, so that the additional value of the alpha-hemihydrate gypsum product is greatly reduced.

If the leaching of valuable metals in the phosphogypsum can be combined with the preparation of the alpha-hemihydrate gypsum with high added value, the leaching cost of the valuable metals can be effectively reduced, the impurity content in the alpha-hemihydrate gypsum product is reduced, the added value of the gypsum product is increased, and the economic benefit and the social benefit of the development and utilization of the phosphogypsum are greatly improved.

Meanwhile, to date; the technology for controlling the crystal form of the alpha-hemihydrate gypsum and improving the leaching rate of metal elements by selecting a proper amount of active additive is rarely reported in related documents.

Disclosure of Invention

The invention aims to provide the method for effectively, reasonably and efficiently leaching the valuable metal impurities in the phosphogypsum and simultaneously preparing the high-value-added gypsum product, aiming at the characteristics of low leaching rate of the valuable metal impurities in the phosphogypsum, low-value-added gypsum product of the leached solid and high comprehensive utilization cost of the phosphogypsum.

The invention relates to a method for efficiently leaching valuable metal impurities in phosphogypsum and preparing a gypsum product with high added value, which is characterized by comprising the following steps: placing phosphogypsum in sulfuric acid solution containing active additive, and leaching at 90 deg.C or above; after leaching, carrying out solid-liquid separation to obtain a solid and a liquid; washing the solid with water and drying to obtain alpha-semi-hydrated gypsum; the active additive is selected from at least one of a surfactant, a polymer or an organic phosphorus scale and corrosion inhibitor, wherein the surfactant is selected from at least one of sodium dodecyl benzene sulfonate, sodium dodecyl sulfonate and hexadecyl trimethyl ammonium bromide, the polymer is selected from at least one of polyacrylic acid, polyacrylamide, polyethylene glycol and polyvinyl alcohol, the organic phosphorus scale and corrosion inhibitor is selected from at least one of amino trimethylene phosphonic acid, hydroxy ethylidene diphosphonic acid, ethylene diamine tetra methylene phosphonic acid, diethylene triamine pentamethylene phosphonic acid, 2-phosphonic acid butane-1, 2, 4-tricarboxylic acid, polyol phosphate, 2-hydroxy phosphonoacetic acid, hexamethylene diamine tetramethylidene phosphonic acid, polyamino polyether methylene phosphonic acid and bis 1,6 hexamethylene triamine pentamethylene phosphonic acid, and preferably at least one of the polymer or the organic phosphorus scale and corrosion inhibitor, more preferably at least one of aminotrimethylenephosphonic acid and hydroxyethylidene diphosphonic acid.

When the active additive is at least one of amino trimethylene phosphonic acid and hydroxy ethylidene diphosphonic acid, the leaching rate of the rare earth is remarkably improved under the same condition; meanwhile, the obtained alpha-hemihydrate gypsum is in a short column shape, and the length-diameter ratio is 1.0-2.0. The invention firstly utilizes the organophosphorus series scale and corrosion inhibitors to realize the efficient control of the crystal form of the alpha-semi-hydrated gypsum and the efficient leaching of the rare earth elements.

The invention relates to a method for efficiently leaching valuable metal impurities in phosphogypsum and simultaneously preparing a high value-added gypsum product; the method comprises the following steps:

(1) adding phosphogypsum into an aqueous solution of sulfuric acid, and uniformly mixing to form phosphogypsum suspension slurry;

(2) adding active additive into the phosphogypsum suspension slurry, heating to 90-115 ℃, and stirring for reaction at the temperature;

(3) after reacting for a period of time, carrying out solid-liquid separation on the suspension slurry while the suspension slurry is hot, washing the separated solid phase with boiling water and drying to obtain a high-quality gypsum product with high added value, wherein the product is alpha-semi-hydrated gypsum, the separated liquid phase is a valuable metal sulfuric acid solution, and the leaching rate of valuable metal impurities in the phosphogypsum can reach more than 80%.

Preferably, the liquid phase separated in the step (3) can be returned to the step (1) for use, so as to further enrich the concentration of the valuable metals in the liquid phase and facilitate the subsequent purification and recovery of the valuable metals.

The main component of the phosphogypsum in the step (1) is calcium sulfate dihydrate (CaSO)₄·2H₂O), the mass percentage content of the calcium sulfate dihydrate in the phosphogypsum is more than or equal to 90 percent. The solid content (mass percentage content) of the phosphogypsum suspension slurry is 1-25%, and preferably 10-20%.

The mass fraction of the sulfuric acid in the sulfuric acid aqueous solution in the step (1) is 12-40%, preferably 15-25%.

The dosage of the active additive in the step (2) is 0.0001-0.5 wt%, preferably 0.001-0.05 wt% of the weight of the phosphogypsum.

The reaction temperature in the step (2) is 90 to 110 ℃, preferably 95 to 100 ℃.

The reaction time in the step (2) is 1-24h, and the stirring speed is 50-200 rpm.

The high value-added gypsum product in the step (3) is alpha-semi-hydrated gypsum, in particular short column-shaped alpha-semi-hydrated gypsum. Short-column alpha-hemihydrate gypsum in the present invention refers to hemihydrate gypsum having an aspect ratio of 1.0 to 17.0. The invention can obtain the alpha-semi-hydrated gypsum with the length-diameter ratio of 1.0-5.0 after the process optimization. After further optimization, the alpha-hemihydrate gypsum with the length-diameter ratio of 1.0-2.5 can be obtained.

The valuable metal impurities in the step (3) mainly refer to Rare Earth Elements (REEs), chromium (Cr), cadmium (Cd) and nickel (Ni).

Principle of

Valuable metal impurities in the phosphogypsum mainly exist in the crystal lattice of the phosphogypsum in a form of isomorphism substitution, and in addition, part of the valuable metal impurities are adsorbed on the crystal surface of the phosphogypsum in a nano phase or amorphous form with poor crystallinity. This occurrence determines that to obtain a higher leaching rate of the valuable metal impurities it is necessary to deconstruct the valuable metal impurities in the lattice, and studies have shown that unless the crystal structure of phosphogypsum is reconstructed, it is not possible to deconstruct all of the valuable metal impurities into solution.

The crystal reconstruction not only can release valuable metal impurities in phosphogypsum crystal lattices, but also can enable dissolved calcium ions to form a new solid phase, reduce the content of the impurity calcium ions in leachate, and relieve the difficulty of subsequent valuable metal element extraction, but the dissolved valuable metal elements enter a newly generated solid phase due to adsorption and eutectic effects in the crystal reconstruction process, so that the leaching rate of valuable metals is reduced, and the well-developed regular crystal can greatly reduce the eutectic and adsorption of the dissolved valuable metal elements in a gypsum phase, so that the valuable metal elements are promoted to be enriched in the liquid phase to improve the leaching rate.

Sulphuric acid is a conventional solution for leaching valuable metal impurities from phosphogypsum, but the leaching rate is low under normal conditions. Meanwhile, the conversion of the dihydrate gypsum to the alpha-hemihydrate gypsum can be realized in the sulfuric acid solution. The alpha-semi-hydrated gypsum prepared by dihydrate gypsum is a crystal reconstruction process of dissolution-recrystallization, valuable metal impurity ions in dihydrate gypsum crystal lattices can be fully released in the crystal transformation process, and the alpha-semi-hydrated gypsum can form regular short columnar crystals by selecting the type of active additives and controlling the dosage of the active additives, so that the aims of reducing eutectic and adsorption of the deconstructed valuable metal ions in an alpha-semi-hydrated gypsum phase are fulfilled, and meanwhile, the short columnar alpha-semi-hydrated gypsum is a gypsum product with high added value. Therefore, the high-quality gypsum product with high added value can be prepared while the valuable metal impurities in the phosphogypsum are efficiently leached out by adjusting the process conditions in the sulfuric acid solution.

Advantages of the invention

1) The sulfuric acid is a raw material for producing the wet-process phosphoric acid, the material is rich and easy to obtain, and the cost advantage is obvious.

2) The process of the invention fully utilizes the dissolving process of phase transition of the dihydrate gypsum to generate the alpha-hemihydrate gypsum, can fully release valuable metal impurities in phosphogypsum crystal lattices, simultaneously controls the crystal form of the alpha-hemihydrate gypsum in the recrystallization process by adding the active additive, reduces the eutectic and adsorption effects of released valuable metals in the newly formed gypsum phase, reduces the enrichment of the released valuable metals to the alpha-hemihydrate gypsum solid phase, and realizes the efficient leaching separation of the valuable metal impurities in the phosphogypsum.

3) The process can effectively remove impurities in the phosphogypsum and obtain a high-quality solid-phase product.

4) The solid phase product after the phosphogypsum is leached is an alpha-hemihydrate gypsum product with high added value.

5) Realizes the high-efficiency leaching of valuable metal impurities in the phosphogypsum and the unification of the preparation of gypsum products with high added values, and greatly improves the economic benefit and the social benefit of the comprehensive utilization of the phosphogypsum.

Description of the drawings:

FIG. 1 is a process flow diagram of the present invention;

FIG. 2 is a scanning electron micrograph of a high value-added gypsum product obtained in example 1;

FIG. 3 is a scanning electron microscope image of the high value-added gypsum product obtained in comparative example 1.1;

FIG. 4 is a scanning electron microscope image of the high value-added gypsum product obtained in comparative example 1.2;

FIG. 5 is a scanning electron micrograph of a high value-added gypsum product obtained in example 2;

FIG. 6 is a scanning electron micrograph of a high value-added gypsum product obtained in example 3;

FIG. 7 is a scanning electron micrograph of a high value-added gypsum product obtained in example 4;

FIG. 8 is a scanning electron micrograph of a high value-added gypsum product obtained in example 5;

FIG. 9 is a scanning electron micrograph of a high value-added gypsum product obtained in comparative example 2.1;

FIG. 10 is a scanning electron micrograph of a high value-added gypsum product obtained in comparative example 2.2;

FIG. 11 is a scanning electron micrograph of a high value-added gypsum product obtained in example 6;

FIG. 12 is a scanning electron micrograph of a high value-added gypsum product obtained in example 7;

FIG. 13 is a scanning electron micrograph of a high value-added gypsum product obtained in example 8;

fig. 14 is a scanning electron micrograph of the high value-added gypsum product obtained in comparative example 3.

Detailed Description

In order to facilitate clear understanding of the technical solution of the present invention, the following detailed description is given with reference to the embodiments.