Method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings

Abstract

The invention relates to a method for preparing a silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings, and relates to the technical field of phosphate tailing recycling, the method for preparing the silicon-calcium-potassium-magnesium phosphate fertilizer from the phosphate tailings comprises the following steps: carrying out acidolysis on the phosphate tailings to obtain a leaching residue A and a leaching solution M; an impurity removal agent is added into the leaching slag A, heavy metal elements in the leaching slag A are removed, and leaching slag B is obtained after solid-liquid separation; activating the leaching residue B by hot alkali, and performing solid-liquid separation to obtain a filter residue A; a phosphorus supplement is added into the leachate M, and filter residues B are obtained after solid-liquid separation; and fully mixing the filter residue A and the filter residue B to obtain the silicon-calcium-potassium-magnesium phosphate fertilizer. The method disclosed by the invention is low in energy consumption and high in phosphate tailing recovery rate, and the prepared silicon-calcium-potassium-magnesium phosphate fertilizer has a relatively high adsorption effect on part of main heavy metals.

Description

Technical Field

[0001] The present application relates to the technical field of phosphate tailings recycling and utilization, and in particular to a method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings. Background Art

[0002] Phosphate tailings are solid wastes generated by phosphate mining and beneficiation. The global demand for phosphate fertilizers has led to an expansion in the scale of phosphate mining, and its emissions have also increased. It mainly comes from areas rich in phosphate resources, such as Hubei and Yunnan in China. It is very harmful to the environment, occupies land, and pollutes soil, water and air. At present, it is difficult to effectively utilize it. The complex composition makes it difficult to use technology universally, and the pretreatment cost is high. The problem of phosphate beneficiation tailings has become a global problem for the rapid economic development and environmental protection of phosphorus chemical companies.

[0003] Heavy metals are highly toxic to all living things and are easily transferred in soil and plants. Excessive concentrations of heavy metals in the soil not only harm the growth and development of plants, but also endanger human health through the food chain.

[0004] Preparing phosphate tailings into fertilizers is a new way to recycle phosphate tailings. Currently, there are two main ways to treat phosphate tailings. One is to combine phosphate tailings with potassium feldspar and obtain silicon-calcium-magnesium fertilizer with calcium silicate and magnesium silicate as the main components through high-temperature roasting. The other is to add phosphoric acid to the phosphate tailings for acid hydrolysis to obtain phosphate-calcium-magnesium fertilizer with calcium phosphate and magnesium phosphate as the main components.

[0005] Both of these recovery methods have problems. Method 1 requires high-temperature roasting of phosphate tailings and potassium feldspar, which has the disadvantage of high energy consumption. Method 2 only recovers calcium and magnesium elements in the phosphate tailings, while silicon, which also has a relatively high mass proportion, is not effectively utilized, resulting in a low recovery rate of phosphate tailings. At the same time, the fertilizers formed by both methods have poor adsorption capacity for some major heavy metal elements (such as lead, cadmium, copper, zinc and other heavy metal elements).

[0006] In view of this, there is an urgent need to provide a method to form a composite fertilizer with stronger adsorption capacity for some major heavy metal elements under the premise of low energy consumption and high recovery rate of phosphate tailings. Summary of the invention

[0007] The present application provides a method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings. The method has low energy consumption and high recovery rate of phosphate tailings, and the prepared silicon-calcium-potassium-magnesium phosphate fertilizer has a high adsorption effect on some major heavy metals.

[0008] In the first aspect, the present application provides a method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings using the following technical solution:

[0009] A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings comprises the following steps:

[0010] Acid hydrolyze the phosphate tailings to obtain intrusion slag A and intrusion liquid M;

[0011] Adding an impurity remover to the intruded slag A to remove heavy metal elements in the intruded slag A, and obtaining intruded slag B after solid-liquid separation;

[0012] The residue B is activated by hot alkali, and the residue A is obtained after solid-liquid separation;

[0013] Adding a phosphorus supplement to the intrusion liquid M, and obtaining a filter residue B after solid-liquid separation;

[0014] The filter residue A and the filter residue B are fully mixed to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

[0015] By adopting the above scheme, the main component of the intruded slag B is SiO 2 , which forms silicates after hot alkali activation, and the main components of the intrusion fluid M include Ca 2+ Mg 2+ , and after reacting with a phosphorus supplement, phosphates such as calcium phosphate, magnesium phosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, dicalcium phosphate, and dicalcium phosphate are formed. The three elements of silicon, calcium, and magnesium in the phosphate tailings are effectively utilized, and the recovery rate of the phosphate tailings is high. The two recovered products are mixed to obtain silicon-calcium-potassium-magnesium phosphate fertilizer, which can better absorb some major heavy metal elements such as lead, cadmium, copper, and zinc, and can be used as a soil conditioner, making this method have a higher economic value.

[0016] Furthermore, the phosphorus supplement includes one or more of dipotassium hydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate.

[0017] By adopting the above scheme, phosphorus supplements can better interact with Ca 2+ Mg 2+ The reaction forms phosphate, and the phosphorus supplement can be specifically set according to the actual situation. For example, in one embodiment, dipotassium hydrogen phosphate and disodium hydrogen phosphate can be selected, and in another embodiment, potassium dihydrogen phosphate and sodium dihydrogen phosphate can be selected.

[0018] Furthermore, the concentration of the phosphorus supplement is set to 1-2 mol / L, and the ratio of the exudate M to the phosphorus supplement is set to 1:4-8.

[0019] By adopting the above scheme and setting a reasonable ratio, Ca2+ and Mg2+ in the invading liquid M can be better recovered, and the utilization rate of calcium and magnesium elements can be improved. In one embodiment, the concentration of the phosphorus supplement can be set to 2 mol / L, and the ratio of the invading liquid M to the phosphorus supplement is set to 1:4; in another embodiment, the concentration of the phosphorus supplement can be set to 1 mol / L, and the ratio of the invading liquid M to the phosphorus supplement is set to 1:8.

[0020] Furthermore, the filter residue A and the filter residue B are fully mixed to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer, comprising:

[0021] Dissolve the filter residue A in water to obtain solution N;

[0022] Add a binder to solution N and stir thoroughly to obtain a jelly;

[0023] Add filter residue B to the colloid and mix thoroughly to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

[0024] Wherein, the stirring temperature is set to 55-65°C, and the mixing time is set to 1-3h.

[0025] By adopting the above scheme, phosphate and silicate are prone to stratification during the mixing process, resulting in uneven mixing. By adopting the above scheme, under the stirring condition of 200-400r / min, the mechanical shear force promotes the uniform mixing of silicate colloid and phosphate particles, while destroying the van der Waals force between particles to prevent precipitation. The 60°C heating environment accelerates the polycondensation reaction of silicate ions and promotes the expansion of the three-dimensional network structure. The thermally reversible gel property of the binder further solidifies the network after cooling to form a stable gel skeleton.

[0026] Furthermore, the binder includes one or more of gelatin, yellow gelatin, potassium alginate, and sodium alginate.

[0027] Furthermore, the concentration of the gelatin and the yellow gelatin is set to 1.5-2wt%, and the concentration of the potassium alginate and the sodium alginate is set to 4-6wt%.

[0028] By adopting the above scheme, the stability of the fertilizer is enhanced by the binder, combined with the chemical bonding of silicate and phosphate, and finally a silicon-calcium-potassium-magnesium phosphate fertilizer with both soil improvement and pollution remediation functions is formed. This process realizes the recycling of the three main elements of silicon, calcium and magnesium in phosphate tailings under low temperature and low energy consumption conditions, breaking through the limitations of traditional high-temperature calcination or single acid hydrolysis technology.

[0029] Furthermore, the impurity remover includes one or more of citric acid, sodium sulfite and sodium sulfide.

[0030] Furthermore, the concentration of the impurity remover is set to 3-15wt%, and the liquid-solid ratio of the impurity remover to the intruded slag A is set to 1-5:1mL / g.

[0031] By adopting the above scheme, the impurity remover can treat the heavy metal elements in the eroded slag A, wherein sodium sulfide is used as a reducing agent to reduce Cr 6+ Reduction to Cr 3+ ,Cr 3+ Together with other heavy metal elements, it undergoes a complex reaction with one or more of citric acid and sodium sulfite and is dissolved, thereby improving the purity of the silicon-calcium-potassium-magnesium-phosphate fertilizer and enhancing its effect in adsorbing heavy metals.

[0032] Furthermore, the hot alkali activation of the extruded slag B is configured as follows: adding potassium hydroxide to the extruded slag B;

[0033] The concentration of the potassium hydroxide is set to 10-40 wt %, and the liquid-solid ratio of the potassium hydroxide to the intruded slag B is set to 4-15:1 mL / g.

[0034] By adopting the above scheme, potassium silicate is finally formed after hot alkali activation. While fully recovering the silicon element, potassium element is further added, and the fertility of silicon-calcium-potassium-magnesium-phosphate fertilizer is improved.

[0035] Furthermore, the hot alkali activation time is set to 1.5 to 3 hours, and the hot alkali activation temperature is set to 70 to 90°C.

[0036] By adopting the above scheme, compared with the method of roasting phosphate tailings and potassium feldspar to obtain calcium silicate and magnesium silicate, it has lower energy consumption, low equipment requirements and is more environmentally friendly.

[0037] In summary, the present application includes at least one of the following beneficial technical effects:

[0038] 1. In the present application, a silicon-calcium-potassium-magnesium phosphate fertilizer with silicate and phosphate as main components is prepared by recycling phosphate tailings, and the silicon, calcium and magnesium elements in the phosphate tailings are effectively utilized. The silicon-calcium-potassium-magnesium phosphate fertilizer formed by compounding the silicate and phosphate can effectively absorb heavy metal elements in the soil, and has the characteristics of high recovery rate of phosphate tailings and strong adsorption capacity of some major heavy metal elements.

[0039] 2. In this application, heavy metal elements in phosphate tailings are treated by adding impurity removers, wherein sodium sulfide is used as a reducing agent to reduce Cr 6+ Reduction to Cr 3+ ,Cr 3+Together with other heavy metal elements, it undergoes a complex reaction with one or more of citric acid and sodium sulfite and is dissolved, thereby improving the purity of the silicon-calcium-potassium-magnesium-phosphate fertilizer to enhance its effect of adsorbing some of the main heavy metal elements.

[0040] 3. The present application enhances the stability of silicon-calcium-potassium-magnesium phosphate fertilizer by using a binder, combines the chemical bonding of silicate and phosphate, and finally forms silicon-calcium-potassium-magnesium phosphate fertilizer with both soil improvement and pollution remediation functions. The method realizes the recycling of the three main elements of silicon, calcium and magnesium in phosphate tailings under low temperature and low energy consumption conditions, breaking through the limitations of traditional high-temperature calcination or single acid hydrolysis technology. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present application more clear, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application and are not used to limit the present application.

[0042] Those skilled in the art will appreciate that, unless otherwise stated, the words "said", "the", and "the aforementioned" used in the text of the present application may also include plural forms. It should be further understood that the wording "including" used in the specification of the present application means the presence of the features, steps, and operations, but does not exclude the presence or addition of one or more other features, integers, and steps.

[0043] Those skilled in the art will appreciate that, for any specific experimental steps or conditions not specified in the examples, the experiments may be carried out according to the conventional experimental steps or conditions described in the literature in the art; any raw materials or instruments used without specifying the manufacturer are conventional products that can be purchased commercially.

[0044] Those skilled in the art will understand that, unless otherwise specified in the present application, when a numerical range is given in an embodiment, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this application are consistent with the prior art mastery of those skilled in the art and the records of this application, and any methods, equipment and materials of the prior art similar or equivalent to the methods, equipment and materials described in the embodiments of this application may also be used to implement this application.

[0045] A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings comprises the following steps:

[0046] S1. Acid erosion: Mix hydrochloric acid with a concentration of 36-38wt% with phosphate tailings ground to about 200 meshes, and set the liquid-solid ratio of hydrochloric acid to phosphate tailings to 1.5-2:1mL / g. Stir at a speed of 200r / min at 40-60℃. After reacting for 2h, separate the solid and liquid to obtain leaching residue A and leaching liquid M.

[0047] S2, impurity removal: adding an impurity remover with a concentration of 3 to 15 wt% to the intruded slag A, wherein the impurity remover comprises one or more of citric acid, sodium sulfide and sodium sulfite, and the liquid-solid ratio of the impurity remover to the intruded slag A is set to 1 to 5:1 mL / g; soaking the intruded slag A in the impurity remover to remove impurities, reacting for 1 to 2 hours, and then separating the solid and liquid to obtain the intruded slag B.

[0048] S3, hot alkali activation: add a potassium hydroxide solution with a concentration of 10-40wt% to the intruded slag B, the liquid-solid ratio of the potassium hydroxide solution to the intruded slag B is set at 4-15:1mL / g, react at 70-90℃ for 1.5-3h, and then separate the solid and liquid to obtain the filter residue A.

[0049] S4, precipitation: add a phosphorus supplement with a concentration of 1-2 mol / L to the intrusion liquid M, the phosphorus supplement includes one or more of dipotassium hydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate, and the liquid-solid ratio of the phosphorus supplement to the phosphate tailings is set to 4-8:1 mL / g. The phosphorus supplement and the intrusion liquid M are mixed at room temperature at a speed of 200 r / min, and after reacting for 1-2 hours, the solid-liquid separation is performed to obtain the filter residue B.

[0050] S5, preparing silicon-calcium-potassium-magnesium phosphate fertilizer, specifically:

[0051] S51, dissolving the filter residue A in water, and filtering to obtain a solution N;

[0052] S52, adding a binder to the solution N, wherein the binder includes 1.5-2 wt% of gelatin and yellow gelatin, and 4-6 wt% of potassium alginate and sodium alginate, and stirring the binder and the solution N at 60° C. at a speed of 200-400 r / min to obtain a jelly;

[0053] S53. Add filter residue B to the colloid, mix the colloid and filter residue B at a speed of 200-400 r / min for 1-3 hours at room temperature, and dry until there is no liquid to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

[0054] The phosphate tailings used in the following examples are sourced from Hubei Sanning Chemical Industry Co., Ltd., and its main chemical composition is shown in Table 1.

[0055] Table 1

[0056] Element CaO MgO <![CDATA[SiO 2 ]]> <![CDATA[P 2 THE 5 ]]> <![CDATA[Fe 2 THE 3 ]]> <![CDATA[Al 2 THE 3 ]]> content(%) 33.09 12.71 7.04 6.9 1.97 1.32 Element MnO <![CDATA[TiO 2 ]]> <![CDATA[K 2 The]]> <![CDATA[Na 2 The]]> ZnO SrO content(%) 0.268 0.234 0.704 0.213 0.00528 0.0505

[0057] The present application is further described in detail below in conjunction with embodiments.

[0058] Embodiment 1:

[0059] A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings comprises the following steps:

[0060] S1. Acid erosion: 160 ml of 36 wt% hydrochloric acid was mixed with 100 g of phosphate tailings ground to about 200 meshes. The hydrochloric acid and the phosphate tailings were stirred at 60°C at a speed of 200 r / min. After reacting for 2 hours, the solid and liquid were separated to obtain leaching residue A and leaching liquid M.

[0061] S2. Impurity removal: 10 ml of an impurity remover with a concentration of 15 wt% is added to the intruded slag A. The impurity remover includes citric acid and sodium sulfide. The intruded slag A is immersed in the impurity remover to remove impurities. After reacting for 1 hour, the solid and liquid are separated to obtain the intruded slag B.

[0062] S3, hot alkali activation: add 45 ml of 33 wt% potassium hydroxide solution to the intruded residue B, react at 90° C. for 2 h, and then separate the solid and liquid to obtain the filter residue A.

[0063] S4, precipitation: add 800 ml of 1 mol / L phosphorus supplement to the intrusion liquid M, the phosphorus supplement includes dipotassium hydrogen phosphate and disodium hydrogen phosphate, the phosphorus supplement and the intrusion liquid M are mixed at room temperature at a speed of 200 r / min, and after reacting for 2 hours, solid-liquid separation is performed to obtain filter residue B.

[0064] S5, preparation of silicon-calcium-potassium-magnesium phosphate fertilizer:

[0065] S51, dissolving the filter residue A in 100 ml of water, and filtering to obtain a solution N;

[0066] S52, adding a binder to the solution N, wherein the binder comprises 2 wt% gelatin and 4 wt% potassium alginate, and stirring the binder and the solution N at 60° C. and at a speed of 400 r / min to obtain a jelly;

[0067] S53. Add filter residue B to the colloid, mix the colloid and filter residue B at room temperature at a speed of 400 r / min for 3 hours, and dry until there is no liquid to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

[0068] After testing, the obtained silicon-calcium-potassium-magnesium phosphate fertilizer has Si≥6.0wt%, Ca≥14.0wt%, K≥3.0wt%, Mg≥2.0wt%, pH8.0-10.0, As≤0.0050wt%, Cd≤0.0010wt%, Pb≤0.0200wt%, Cr≤0.0500wt%, Hg≤0.0005wt%, which meets the national standards.

[0069] Embodiment 2:

[0070] A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings comprises the following steps:

[0071] S1. Acid erosion: 200 ml of 36 wt% hydrochloric acid was mixed with 100 g of phosphate tailings ground to about 200 meshes. The hydrochloric acid and the phosphate tailings were stirred at 200 r / min at 40°C. After reacting for 2 hours, the solid and liquid were separated to obtain leaching residue A and leaching liquid M.

[0072] S2, impurity removal: add 50 ml of an impurity remover with a concentration of 3 wt% to the intruded slag A, the impurity remover includes citric acid and sodium sulfide, soak the intruded slag A in the impurity remover to remove impurities, react for 2 hours, separate the solid and liquid, and obtain the intruded slag B.

[0073] S3, hot alkali activation: add 67.5 ml of 33 wt% potassium hydroxide solution to the precipitated residue B, react at 70° C. for 3 h, and then separate the solid and liquid to obtain the filter residue A.

[0074] S4, precipitation: add 400 ml of 2 mol / L phosphorus supplement to the intrusion liquid M, the phosphorus supplement includes dipotassium hydrogen phosphate and disodium hydrogen phosphate, the phosphorus supplement and the intrusion liquid M are mixed at room temperature at a speed of 200 r / min, and after reacting for 1 hour, solid-liquid separation is performed to obtain filter residue B.

[0075] S5, preparation of silicon-calcium-potassium-magnesium phosphate fertilizer:

[0076] S51, dissolving the filter residue A in 100 ml of water, and filtering to obtain a solution N;

[0077] S52, adding a binder to the solution N, wherein the binder includes 1.5 wt% of yellow gelatin and 6 wt% of sodium alginate, and stirring the binder and the solution N at 60° C. and at a speed of 200 r / min to obtain a jelly;

[0078] S53. Add filter residue B to the colloid, mix the colloid and filter residue B at room temperature at a speed of 400 r / min for 3 hours, and dry until there is no liquid to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

[0079] After testing, the obtained silicon-calcium-potassium-magnesium phosphate fertilizer has Si≥6.0wt%, Ca≥14.0wt%, K≥3.0wt%, Mg≥2.0wt%, pH8.0-10.0, As≤0.0050wt%, Cd≤0.0010wt%, Pb≤0.0200wt%, Cr≤0.0500wt%, Hg≤0.0005wt%, which meets the national standards.

[0080] The embodiments of this specific implementation are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. The same components are represented by the same reference. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings, characterized in that: The following steps are involved: Acid hydrolyze the phosphate tailings to obtain intrusion slag A and intrusion liquid M; Adding an impurity remover to the intruded slag A to remove heavy metal elements in the intruded slag A, and obtaining intruded slag B after solid-liquid separation; The residue B is activated by hot alkali, and the residue A is obtained after solid-liquid separation; Adding a phosphorus supplement to the intrusion liquid M, and obtaining a filter residue B after solid-liquid separation; The filter residue A and the filter residue B are fully mixed to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer.

2. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 1, characterized in that: The phosphorus supplement includes one or more of dipotassium hydrogen phosphate, disodium hydrogen phosphate, potassium dihydrogen phosphate, and sodium dihydrogen phosphate.

3. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 2, characterized in that: The concentration of the phosphorus supplement is set to 1-2 mol / L, and the liquid-solid ratio of the phosphorus supplement to the phosphate tailings is set to 4-8:1 mL / g.

4. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 1, characterized in that: The filter residue A and the filter residue B are fully mixed to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer, comprising: Dissolve the filter residue A in water to obtain solution N; Add a binder to solution N and stir thoroughly to obtain a jelly; Add filter residue B to the colloid, mix thoroughly and dry to obtain silicon-calcium-potassium-magnesium-phosphate fertilizer. Wherein, the stirring temperature is set to 55-65°C, and the mixing time is set to 1-3h.

5. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 4, characterized in that: The binder includes one or more of gelatin, yellow gelatin, potassium alginate, and sodium alginate.

6. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 5, characterized in that: The concentration of the gelatin and the yellow gelatin is set to 1.5-2wt%, and the concentration of the potassium alginate and the sodium alginate is set to 4-6wt%.

7. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 1, characterized in that: The impurity remover includes one or more of citric acid, sodium sulfite and sodium sulfide.

8. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 7, characterized in that: The concentration of the impurity remover is set to 3-15wt%, and the liquid-solid ratio of the impurity remover to the intruded slag A is set to 1-5:1mL / g.

9. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 1, characterized in that: The hot alkali activation of the extruded slag B is configured as follows: adding potassium hydroxide to the extruded slag B; The concentration of the potassium hydroxide is set to 10-40 wt %, and the liquid-solid ratio of the potassium hydroxide to the intruded slag B is set to 4-15:1 mL / g.

10. A method for preparing silicon-calcium-potassium-magnesium phosphate fertilizer from phosphate tailings according to claim 9, characterized in that: The hot alkali activation time is set to 1.5 to 3 hours, and the hot alkali activation temperature is set to 70 to 90°C.