A method for dry mixing and grinding to collaboratively dispose of gypsum slag and strontium / barium slag

Abstract

The present invention relates to a method for dry mixing and grinding to synergistically dispose of gypsum slag and strontium / barium slag, and the specific steps are as follows: strontium slag and / or barium slag are mixed with gypsum slag, put into a ball mill for ball milling, and obtain a carbonate-sulfate complex. The present invention realizes the acid-base neutralization reaction of gypsum slag and barium / strontium slag in the absence of water, avoids the waste of resources and the release of harmful substances in the process of alkali washing of gypsum slag and acid washing of strontium-barium slag by traditional liquid phase precipitation method, and the obtained carbonate-sulfate complex has stable performance, especially acid rain resistance, and can greatly reduce the leaching of strontium / barium ions, solves the stacking problem of industrial by-product solid waste such as phosphogypsum and desulfurized gypsum and the disposal problem of hazardous waste such as strontium-barium slag, and the process is simple and easy to operate, and has strong practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method for dry mixing and grinding coordinated treatment of gypsum slag and strontium / barium slag. Background Art

[0002] In recent years, along with the development and utilization of mineral resources, the stockpile of industrial by-product gypsum slag has increased dramatically. The main component of gypsum slag is calcium sulfate. Gypsum slag is accompanied by acidic substances such as free phosphoric acid and fluoride. Therefore, gypsum slag will cause great damage to the ecological environment during storage. At present, the treatment methods of acidic substances in gypsum slag are mainly water washing and dilution, alkali neutralization treatment and precipitation conversion. These methods can meet the requirements of harmless treatment of gypsum slag. However, they are often accompanied by problems such as high cost, insufficient treatment of gypsum slag and waste of resources. Therefore, it is of great practical significance to study new treatment processes or resource utilization of gypsum slag.

[0003] In addition, after the mining of strontium and barium mines, a large amount of corrosive alkaline waste residue (mainly composed of strontium carbonate, barium carbonate, etc.) will be produced. At the same time, the long-term storage of strontium and barium tailings under certain environmental conditions (such as long-term rainwater immersion, leakage, overflow, etc.) may cause surface geochemical and interfacial chemical reactions, releasing heavy metals strontium and barium to pollute water and soil. At present, the treatment methods for soluble strontium and barium slag are mainly concentrated in terminal treatment methods, including adsorption, ion exchange, chemical precipitation, etc. The adsorption method and ion exchange method are high in cost and low in treatment efficiency, while the chemical precipitation method based on alkali neutralization consumes a large amount of reagents and involves secondary pollution and other problems.

[0004] In view of the different acid-base properties of the above two types of waste residues, many teams have also carried out relevant research on their comprehensive utilization. The Chinese patent (application number 2017108893380) injects water into the ground barium slag and phosphogypsum respectively to obtain water-injected barium slag and water-injected phosphogypsum, and then mixes the two to form a stable barium sulfate precipitate. On this basis, the Chinese patent (application number 2021112964949) treats barium slag and phosphogypsum with a modifier, and finally prepares a gel material by wet mixing and stirring and then aging. Although this type of liquid phase precipitation method can quickly convert soluble barium salts into difficult-to-leach barium sulfate, this method has the disadvantages of complex operation and large residual barium ions in the liquid phase. The filtered waste residue and wastewater need to be treated secondary.

[0005] Based on the above background, the present invention dry-mixes and grinds gypsum slag and strontium / barium slag in the next step of high-energy ball milling, promotes a chemical reaction between strontium / barium carbonate and gypsum in the solid phase, and directly converts strontium / barium carbonate into stable sulfates, thereby achieving the purpose of "treating waste with waste". Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for the coordinated disposal of gypsum slag and strontium / barium slag by dry mixing and grinding in view of the above-mentioned deficiencies in the prior art, wherein alkaline strontium / barium slag is used as an acidic gypsum slag alkaline washing agent, and ball milling is performed in one step by a mechanochemical method. While the acidic substances in the gypsum slag and the alkaline substances in the strontium / barium slag are used for acid-base neutralization, the mechanical energy imparted also promotes the conversion of strontium / barium carbonate ore into sulfate-type minerals to achieve the effect of fixing strontium and barium.

[0007] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0008] A method for dry mixing and grinding to co-dispose gypsum slag and strontium / barium slag is provided, and the specific steps are as follows: strontium slag and / or barium slag are mixed with gypsum slag, and put into a ball mill for ball milling to obtain a carbonate-sulfate complex.

[0009] According to the above scheme, the gypsum slag is phosphogypsum or desulfurized gypsum, and the CaSO4·2H2O content is more than 70wt%.

[0010] According to the above scheme, the strontium slag is the tailings containing strontium carbonate after strontium mining, wherein the strontium content is 20-26wt% calculated as SrO; the barium slag is the tailings containing barium carbonate after barium mining, wherein the barium content is 36-90wt% calculated as BaO.

[0011] According to the above scheme, the ratio of the total molar amount of strontium and barium elements in the strontium slag and / or barium slag to the molar amount of sulfate in the gypsum slag is 1:1-5. When the molar ratio of Ba2+, Sr2+ and sulfate is 1:1-5, the water-leaching and acid-leaching type Sr and Ba are completely fixed as sulfate-type strontium and barium.

[0012] According to the above scheme, the ball milling process conditions are: using zirconium balls as ball milling media, the ball-to-material ratio is 35:1, the grinding speed is 200-600rpm (revolutions / minute), and the grinding time is 2-10h.

[0013] Preferably, the grinding speed is 600 rpm and the grinding time is 2 h.

[0014] The present invention utilizes mechanochemical grinding means to mix and grind strontium slag and / or barium slag with gypsum slag. The mixed slag undergoes a chemical reaction under the action of mechanochemical force to obtain a stable sulfate-carbonate complex, thereby achieving one-step fixation of strontium and barium elements, thereby solving the environmental problems caused by the accumulation of gypsum waste slag and strontium / barium slag and achieving the purpose of fixing heavy metals.

[0015] The beneficial effects of the present invention are as follows: the present invention realizes the acid-base neutralization reaction of gypsum slag and barium / strontium slag without adding water, thereby avoiding the waste of resources and the release of harmful substances in the process of gypsum slag alkaline washing and strontium-barium slag acid washing by the traditional liquid phase precipitation method, and the obtained carbonate-sulfate complex has stable performance, especially resistance to the influence of acid rain, etc., and can greatly reduce the leaching of strontium / barium ions, solves the stacking problem of industrial by-product solid waste such as phosphogypsum and desulfurized gypsum and the disposal problem of hazardous waste such as strontium-barium slag, and the process is simple and easy to operate, and has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The XRD diagrams of the ball-milled products obtained at different grinding speeds in Example 1 of the present invention are shown;

[0017] Figure 2 This is a comparison chart of the barium ion concentration in the liquid phase of the ball-milled product and the raw material barium carbonate at different rotation speeds in Example 1 after acid leaching in an acid leaching solution with an initial pH value of 1.5 over time;

[0018] Figure 3 This is a comparison chart of the barium ion concentration in the liquid phase of the ball milled product and the raw barium carbonate at different rotation speeds in Example 1 after acid leaching in an acid leaching solution with an initial pH value of 3 over time;

[0019] Figure 4 This is a graph showing the pH value change of the acid leaching solution during the acid leaching reaction of the ball milled product and the raw material barium carbonate at different rotation speeds in Example 1 in an acid leaching solution with an initial pH value of 3;

[0020] Figure 5 This is a graph showing changes in pH value of the acid leaching solution during the acid leaching reaction of the ball milled product and the raw material barium carbonate at different rotation speeds in Example 1 in an acid leaching solution with an initial pH value of 1.5;

[0021] Figure 6 This is the XRD pattern of the ball-milled product obtained in Example 2. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0023] The barium carbonate, dihydrate gypsum and other reagents used in the embodiments of the present invention are all from Shanghai Sinopharm Group, and the chemical purity is analytical grade.

[0024] The ball mill used in the following examples is a German Pulverisette 7 planetary mill.

[0025] Example 1

[0026] A method for dry mixing and grinding to synergistically dispose of gypsum slag and barium slag, the specific steps are as follows: 1.067g of barium carbonate and 0.933g of dihydrate gypsum are added into a ball mill for ball milling, the molar ratio of barium carbonate to calcium sulfate in dihydrate gypsum is 1:1, zirconium balls are used as ball milling media, the ball-to-material ratio is 35:1, the ball milling time is 120 min, and the XRD spectra of the ball milling products obtained at different rotation speeds (rotation speeds are 200 rpm, 400 rpm, and 600 rpm, respectively) are as follows: Figure 1 shown.

[0027] from Figure 1 The XRD results clearly show that with the increase of ball milling speed, the phase of barium carbonate gradually changes to barium sulfate. When the ball milling speed reaches 600 rpm, only two phases, barium sulfate and aragonite phase calcium carbonate, appear in the XRD spectrum, indicating that the ball milling process achieves a complete chemical reaction between barium carbonate and dihydrate gypsum.

[0028] In order to compare the acid resistance between the ball milling products at different speeds and the raw barium carbonate, several portions of the same mass of ball milling products at different speeds and several portions of the same amount of raw barium carbonate were weighed, each portion of 0.1g, and placed in a series of acid leaching solutions with different pH values ​​(HNO3 aqueous solution, each portion of 100 mL) for stirring. Samples were taken at regular intervals during stirring, and the leaching concentration of Ba2+ in the solution and the pH value of the solution were measured by atomic absorption spectrometry. Under the condition that the initial pH value of the acid leaching solution was 1.5, the comparison of the barium ion concentration in the liquid phase of each sample after acid leaching over time is shown in the figure below. Figure 2 As shown, it can be seen that the raw barium carbonate gradually dissolved in the acidic solution with an initial pH value of 1.5, and the barium ion concentration in the solution gradually increased until the barium carbonate was almost completely dissolved after 14 days, and the barium ion leaching rate reached 97%. During the acid leaching process, the crystal phase of barium sulfate remained almost unchanged in the product after ball milling with dihydrate gypsum, and even the barium ion leaching concentration in the acid leaching solution of the ball milled product at 200 rpm and 600 rpm decreased. After 14 days of acid leaching, the barium ion leaching rate of the barium sulfate-carbonate composite product produced by ball milling at 600 rpm in the acid leaching solution was as low as 0.5%, which was much lower than the leaching rate of other barium fixation methods, indicating that the barium sulfate-carbonate composite product generated by high-energy ball milling has a more stable acid resistance.

[0029] A similar trend was also shown when the initial pH value of the acid leaching solution was 3. The comparison of the barium ion concentration in the liquid phase of each sample after acid leaching over time is shown in the figure below. Figure 3 As shown, the barium ion leaching of the raw material barium carbonate is relatively large, reaching about 29%, while the acid resistance of the barium sulfate-calcium carbonate composite generated by ball milling has been greatly improved.

[0030] The advantages of the ball milling treatment of the present invention can also be found by comparing the pH values ​​of the acid leaching solution before and after acid leaching. The pH value change of the acid leaching solution during the acid leaching reaction of each sample when the initial pH value of the acid leaching solution is 3 is shown in the figure below: Figure 4 As shown in the figure, it can be seen that as the ball milling speed increases, the pH value of the solution after acid leaching gradually increases. Under the condition of 600 rpm, the pH value of the ball milling product acid leaching solution quickly reaches equilibrium and remains at about 8, indicating that the ball milling product of this embodiment has a certain pH buffering effect on the acidic environment. Under the condition that the initial pH value of the acid leaching solution is 1.5, the pH value change of the acid leaching solution during the acid leaching reaction of each sample is shown in the figure. Figure 5 shown.

[0031] Example 2

[0032] A method for dry mixing and grinding to synergistically dispose of gypsum slag and barium slag, the specific steps are as follows: 1.33g of gypsum slag with a dihydrate gypsum content of 70wt% and 1.1g of witherite with a barium carbonate content of 90wt% are added into a ball mill for ball milling, zirconium balls are used as ball milling media, the ball-to-material ratio is 35:1, and the ball milling is performed at a ball milling speed of 600rpm for 120min to obtain a ball milling product.

[0033] The XRD pattern of the ball-milled product obtained in this example is as follows: Figure 6 As shown, from Figure 6 The XRD results show that when the actual slag is milled at a speed of 600 rpm and a milling time of 120 min, the only observable crystal phase of the product is barium sulfate, indicating that the actual slag can also generate a barium sulfate-calcium carbonate complex and achieve stable solidification under this condition. Therefore, the present invention adopts a one-step dry milling method to achieve good fixation of acidic gypsum slag with barium slag, while achieving the purpose of treating waste with waste and reducing costs.

Claims

1. A method for dry mixing and grinding to co-dispose gypsum slag and strontium / barium slag, characterized in that: The specific steps are as follows: mixing strontium slag and / or barium slag with gypsum slag, placing the mixture in a ball mill for ball milling, and obtaining a carbonate-sulfate complex; The ratio of the total molar amount of strontium and barium elements in the strontium slag and / or barium slag to the molar amount of sulfate in the gypsum slag is 1:1-5; The ball milling process conditions are: using zirconium balls as ball milling media, a ball-to-material ratio of 35:1, a grinding speed of 600 rpm, and a grinding time of 2 hours.

2. The method for dry mixing and grinding to co-dispose gypsum slag and strontium / barium slag according to claim 1, characterized in that: The gypsum slag is phosphogypsum or desulfurized gypsum, and the CaSO4·2H2O content is more than 70wt%.

3. The method for dry mixing and grinding to co-dispose gypsum slag and strontium / barium slag according to claim 1, characterized in that: The strontium slag is tailings containing strontium carbonate after strontium ore mining, wherein the strontium content is 20-26wt% calculated as SrO; the barium slag is tailings containing barium carbonate after barium ore mining, wherein the barium content is 36-90wt% calculated as BaO.

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