Organic-inorganic compound liquid fertilizer based on manganese ore smelting solid waste resource utilization and preparation method and application thereof

Abstract

This invention discloses an organic-inorganic composite liquid fertilizer based on the resource utilization of solid waste from manganese ore mining, its preparation method, and its application, belonging to the technical field of industrial solid waste resource utilization and novel fertilizer preparation. This invention uses the decoupling solution obtained from the decoupling electrolysis of manganese slag with ammonium persulfate as raw material, and magnesium manganese ammonium sulfate double salt crystals to supplement Mg. 2+ Mn 2+ NH4 + The process employs a two-step purification method: hydrolysis with NH4OH at pH 5.0 to remove iron and aluminum, and deep precipitation of heavy metals with (NH4)2S. This achieves removal rates of 99.67% for Fe and 99.99% for Al, meeting agricultural standards for heavy metals. A complexation system is constructed using organic acids such as citric acid and malic acid to improve fertilizer stability and nutrient utilization. The resulting liquid fertilizer has the following composition: total nitrogen 5.0 g / L, Mg 25.4 g / L, Mn 5.2 g / L, pH 6.58. This invention features a gentle, thorough, and balanced process that not only improves corn leaf growth rate and SPAD value but also enhances microbial community richness. It combines the functions of solid waste resource utilization, crop growth promotion, and soil remediation, making it suitable for large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field of industrial solid waste resource utilization and water-soluble fertilizer preparation, specifically relating to an organic-inorganic composite liquid fertilizer based on the resource utilization of manganese mining solid waste, its preparation method, and its application. Background Technology

[0002] Electrolytic manganese slag is a large-scale acidic industrial solid waste generated during the electrolytic production of metallic manganese. It is characterized by massive emissions, large storage areas, and high environmental risks. Because it contains heavy metals, ammonium salts, and sulfates, long-term storage can easily lead to heavy metal leakage, ammonia nitrogen loss, soil acidification, and water pollution, seriously threatening the ecological environment and the health of surrounding populations. It is a prominent issue hindering the green development of the manganese industry. At the same time, electrolytic manganese slag is rich in essential plant nutrients such as manganese, magnesium, ammonium, and sulfur, possessing the potential for resource utilization in the preparation of agricultural fertilizers. Rational utilization can achieve the dual goals of reducing solid waste and increasing agricultural efficiency.

[0003] Currently, the preparation of liquid fertilizer from electrolytic manganese slag has become an important direction for resource utilization, but existing technologies have many shortcomings. Leachates obtained from traditional extraction processes generally suffer from insufficient synergistic supply and imbalanced ratios of magnesium, manganese, and nitrogen nutrients, making it difficult to meet crop growth needs. Furthermore, harmful impurities such as iron, aluminum, cadmium, and lead in the leachate are difficult to remove completely, resulting in fertilizer safety failing to meet agricultural standards. Unstabilized metal ions are prone to hydrolysis and precipitation, leading to poor storage stability, easy stratification, and nutrient fixation by the soil, resulting in low plant utilization. In addition, existing products have limited functionality, providing only basic nutrients and lacking ecological functions such as improving soil structure, enhancing aggregate stability, regulating microbial communities, and remediating acidified soils, resulting in low added value.

[0004] Magnesium manganese ammonium sulfate double salt crystals are another type of solid waste generated during the electrolytic manganese production process. In the electrolytic manganese production process, when a solution containing manganese, magnesium, and ammonium ions is circulated, enriched, and cooled, the ions in the solution precipitate out in the form of double salt mixed crystals, the main components of which are magnesium, manganese, and ammonium sulfate double salts. Magnesium manganese ammonium sulfate double salt crystals are a typical "problem resource" facing the electrolytic manganese industry; improper disposal can lead to significant environmental pressure and production burden.

[0005] Ammonium persulfate oxidation decoupling technology can effectively disrupt the crystal lattice of manganese slag, significantly improving nutrient dissolution rate and providing a new pathway for resource utilization. However, the decoupling solution still suffers from insufficient nutrients, excessive impurities, and system instability, making it unsuitable for direct agricultural use. The resource utilization of magnesium manganese ammonium sulfate double salt crystals has also become an urgent need for the sustainable development of the industry. However, existing technologies have not yet formed a complete process integrating nutrient replenishment, impurity removal, complexation, and functionalization, making it difficult to prepare liquid fertilizers that are nutrient-balanced, stable, safe, and possess both growth-promoting and repairing functions. Therefore, developing an efficient and feasible organic-inorganic composite liquid fertilizer preparation technology is of great significance for promoting the high-value utilization of electrolytic manganese waste and the green development of agriculture. Summary of the Invention

[0006] One objective of this invention is to provide a method for preparing an organic-inorganic composite liquid fertilizer based on the resource utilization of solid waste from manganese ore mining, comprising the following steps:

[0007] (1) Compound supplementation: Add 1000g of magnesium manganese ammonium sulfate double salt crystals to every 3000mL of decoupling solution obtained by ammonium persulfate oxidation and decoupling electrolytic manganese slag to supplement Mg. 2+ Mn 2+ NH4 + This yields a qualified liquid, solving the problem of insufficient synergistic supply of magnesium, manganese, and nitrogen in traditional electrolytic manganese slag-based fertilizers, and achieving a balanced nutrient ratio.

[0008] (2) Deep purification: A two-step chemical precipitation method was used to deeply purify the decoupling solution. The pH of the qualified solution was adjusted to 5.0 with NH4OH and stirred for 30 min. After standing for 15 min, the precipitate was removed by filtration, so that Fe 3+ Al 3+ After thorough hydrolysis and precipitation, the removal rates reached 99.67% and 99.99%, respectively. Then, 300% of the theoretical dosage of (NH4)2S was added, and the reaction was carried out at 50℃ for 45 min. After cooling to room temperature, the solution was filtered to remove heavy metal ions such as Cd and Pb, yielding a purified solution that meets the safety standards for agricultural fertilizers. (The theoretical consumption value was calculated based on a 1:1 stoichiometric ratio of total heavy metals to (NH4)2S precipitation reaction. To offset the loss from oxidative impurities and to deeply remove trace amounts of complexed heavy metals, the actual molar amount added was three times the theoretical value.)

[0009] (3) Organic acid complexation: Add natural organic acid to the purified solution so that its total mass fraction in the final mixture is 4%, and carry out a complexation reaction at 25–45℃ for 20–90 min to form a stable complexation system, so that the Mg in the solution is reduced. 2+ Mn 2+ Ca 2+ Fe 2+ Zn 2+Metal ions form stable complexes, which significantly improves the storage stability and nutrient absorption and utilization rate of liquid fertilizer;

[0010] (4) Formulation: Adjust the pH of the complexing solution to 5.5–7.0, and make up the volume with water to obtain organic-inorganic compound liquid fertilizer. The volume of the make-up is calculated as 5L per 3000mL of decoupling solution.

[0011] Preferably, the natural organic acid is one or more of citric acid, malic acid, tartaric acid, and oxalic acid.

[0012] The second objective of this invention is to provide an organic-inorganic composite liquid fertilizer based on the resource utilization of solid waste from manganese ore mining, wherein the organic-inorganic composite liquid fertilizer is prepared by the above-mentioned method.

[0013] The third objective of this invention is to provide an application of the above-mentioned organic-inorganic compound liquid fertilizer in promoting plant leaf growth and / or promoting plant chlorophyll synthesis and / or promoting soil microbial species richness.

[0014] Preferably, the plant is corn.

[0015] The fourth objective of this invention is to provide a method for applying the above-mentioned organic-inorganic compound liquid fertilizer to promote plant leaf growth and / or promote plant chlorophyll synthesis and / or promote soil microbial species richness, comprising the following steps:

[0016] (1) Fill the flowerpot with 2.8 kg of air-dried soil, mix in 3.0 g of base fertilizer, and sow seeds at a depth of 2.5 cm;

[0017] (2) When applying the fertilizer once, take 10 mL of organic-inorganic compound liquid fertilizer, dilute it with water 1000 times to form a working solution, add at least one of methionine aqueous solution and magnesium manganese ammonium sulfate double salt crystal aqueous solution to the working solution to form a mixed solution; the amount of methionine aqueous solution added is 10.5 mL, and the amount of magnesium manganese ammonium sulfate double salt crystal aqueous solution added is 9 mL.

[0018] (3) Apply the above mixed solution to the roots of the plant by drip irrigation.

[0019] Preferably, the concentration of the methionine aqueous solution is 1.0% (w / v, unit g / mL), and the magnesium manganese ammonium sulfate double salt crystal aqueous solution is prepared by mixing 1000 g of magnesium manganese ammonium sulfate double salt crystals with 3000 mL of water.

[0020] Preferably, the method further includes foliar spraying of the above-mentioned mixed solution during the seedling stage of the plant.

[0021] Preferably, the plant is corn.

[0022] Beneficial effects:

[0023] This invention features a simple preparation process, mild reaction conditions, thorough impurity removal, and no secondary pollution. The resulting organic-inorganic composite liquid fertilizer is nutrient-balanced, safe, stable, and widely applicable. It not only significantly improves the growth rate of corn leaves and the chlorophyll SPAD value but also promotes the enrichment of the microbial community. This invention achieves an organic combination of the resource utilization of electrolytic manganese slag and green agricultural production, possessing significant economic, environmental, and social benefits, and is suitable for large-scale production and widespread application. Attached Figure Description

[0024] Figure 1 Schematic diagram of the process flow for preparing liquid fertilizer from electrolytic manganese slag through oxidation and decoupling.

[0025] Figure 2 XRD pattern of magnesium manganese ammonium sulfate double salt crystals;

[0026] Figure 3 Curves showing the changes in iron and aluminum ion content in the decoupling solution under different pH conditions;

[0027] Figure 4 The effect of different fertilizers on the number of corn leaves;

[0028] Figure 5 The effects of different fertilizers on SPAD;

[0029] Figure 6 The effect of different fertilizers on the abundance index. Detailed Implementation

[0030] The present invention will be described in detail below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of application of the present invention. The present invention is not limited to the following embodiments or examples. Any modifications and variations made without departing from the spirit of the present invention should be included within the scope of the present invention. Unless otherwise specified, the experimental materials or reagents used in the following embodiments are commercially available.

[0031] Experimental materials:

[0032] 1. Ammonium persulfate oxidation decoupling solution for electrolytic manganese slag:

[0033] The electrolytic manganese slag described in this example is fresh waste residue from the filter press workshop of Guizhou Jinrui New Materials Co., Ltd. The main chemical components of the electrolytic manganese slag, by mass percentage, are: Mn 4.2%, SiO2 32.5%, CaO 18.3%, MgO 2.1%, Fe2O3 3.6%, Al2O3 2.8%, SO3 24.7%, NH4+ + 1.8%.

[0034] Pretreatment of electrolytic manganese slag: The above electrolytic manganese slag is placed in an oven at 105℃ and dried to constant weight. After being crushed by a pulverizer, it is passed through a 100-mesh sieve to obtain electrolytic manganese slag powder, which is then placed in a desiccator for later use.

[0035] Weigh the pretreated electrolytic manganese slag powder and place it in a reaction vessel. Add deionized water at a ratio of 6 mL of deionized water per gram of electrolytic manganese slag powder, and then add ammonium persulfate to make the concentration of ammonium persulfate in the solution 30 g / L. Place the vessel in a constant temperature water bath and leach at a leaching temperature of 80°C with stirring for 3 hours. After the reaction is complete, perform solid-liquid filtration to separate the slurry. Collect the filtrate as the ammonium persulfate oxidation decoupling solution for subsequent experiments.

[0036] 2. Magnesium manganese ammonium sulfate double salt crystals:

[0037] The magnesium manganese ammonium sulfate double salt crystals described in this example are byproducts of the closed-loop recycling process of the electrolytic manganese production line at Guizhou Jinrui New Materials Co., Ltd. The crystals are grayish-white solid powders, mainly composed of ammonium sulfate, manganese sulfate, and magnesium sulfate. XRF results show that SO3, MgO, and MnO are the absolute main components of the magnesium manganese ammonium sulfate double salt crystals, accounting for a total of 98.42% (Table 1). XRD patterns show that the magnesium manganese ammonium sulfate double salt crystals are (NH4)2Mg(SO4)2 6H2O and (NH4)2Mn(SO4)2 6H2O undergoes isomorphic mixed crystallization, SO4 2- Mg 2+ Mn 2+ The composition of the crystal core is completely consistent with the quantitative results of major elements obtained by XRF. Figure 2 ).

[0038] Table 1. XRF results of magnesium manganese ammonium sulfate double salt crystals

[0039]

[0040] Example 1: Citric Acid Single Complex Organic-Inorganic Compound Liquid Fertilizer

[0041] Take 1000 g of magnesium manganese ammonium sulfate double salt crystals and dissolve them in 3000 mL of electrolytic manganese slag ammonium persulfate oxidation decoupling solution. Stir at room temperature for 30 min until completely dissolved to obtain a qualified solution. Slowly adjust the pH of the qualified solution to 5.0 with NH4OH solution (different pH values ​​are excluded depending on iron and aluminum content, etc.). Figure 3(As shown), continue stirring for 30 min, let stand for 15 min, and filter to remove Fe(OH)5 and Al(OH)3 precipitates; add 300% of the theoretical amount of (NH4)2S to the filtrate (the theoretical consumption value is calculated based on the stoichiometric relationship between total heavy metals and (NH4)2S in a 1:1 precipitation reaction. In order to offset the loss of oxidative impurities in the system and to deeply remove trace amounts of complexed heavy metals, the actual molar amount added is 3 times the theoretical value). The mixture was placed in a 50℃ constant temperature water bath for 45 min, cooled to room temperature, and filtered to obtain a purified solution (the heavy metal content in the purified solution met the requirements of "NY 1110-2010 Limits for Mercury, Arsenic, Cadmium, Lead, and Chromium in Water-Soluble Fertilizers": Hg≤5 mg / kg, As≤10 mg / kg, Cd≤10 mg / kg, Pb≤50 mg / kg, Cr≤50 mg / kg). Citric acid was added to the purified solution to make its total mass fraction in the final mixture 4%, and the mixture was stirred at 35℃ for 60 min. The pH was adjusted to 6.58, and the volume was adjusted to 5L with water to obtain a citric acid single complex organic-inorganic compound liquid fertilizer.

[0042] Example 2: Malic acid-tartaric acid binary complex organic-inorganic compound liquid fertilizer

[0043] 1000 g of magnesium manganese ammonium sulfate double salt crystals were dissolved in 3000 mL of electrolytic manganese slag ammonium persulfate oxidation decoupling solution. The solution was stirred at room temperature for 30 min until completely dissolved to obtain a qualified solution. The pH of the qualified solution was slowly adjusted to 5.0 with NH4OH solution, and stirring was continued for 30 min. After standing for 15 min, the solution was filtered to remove Fe(OH)3 and Al(OH)3 precipitates. 300% of the theoretical dosage of (NH4)2S was added to the filtrate, and the solution was reacted in a 50℃ constant temperature water bath for 45 min. After cooling to room temperature, the solution was filtered to obtain a purified solution. Malic acid and tartaric acid were added to the purified solution so that their total mass fraction in the final mixture was 2.0%. The solution was reacted at 40℃ for 50 min. The pH was adjusted to 6.58, and the solution was diluted to 5 L with water to obtain a malic acid-tartaric acid binary complex organic-inorganic compound liquid fertilizer.

[0044] Example 3: Citric acid-malic acid-oxalic acid ternary complex organic-inorganic compound liquid fertilizer

[0045] Take 1000 g of magnesium manganese ammonium sulfate double salt crystals and dissolve them in 3000 mL of electrolytic manganese slag ammonium persulfate oxidation decoupling solution. Stir at room temperature for 30 min until completely dissolved to obtain a qualified solution. Slowly adjust the pH of the qualified solution to 5.0 with NH4OH solution, continue stirring for 30 min, let stand for 15 min, and filter to remove Fe(OH)3 and Al(OH)3 precipitates. Add 300% of the theoretical dosage of (NH4)2S to the filtrate, place it in a constant temperature water bath at 50℃ for 45 min, cool to room temperature, and filter to obtain a purified solution. Add citric acid, malic acid, and oxalic acid to the purified solution so that their total mass fractions in the final mixture are 1.5%, 1.5%, and 1.0%, respectively, and react at 30℃ for 70 min. Adjust the pH to 6.58 and make up to 5 L with water to obtain a ternary organic acid complex organic-inorganic compound liquid fertilizer.

[0046] Example 4: Effects of liquid fertilizer on corn growth and soil properties

[0047] Test crop: Maize;

[0048] Experimental treatments: J, J+M, J+Y, J+A, J+M+Y, J+M+A, J+Y+A, J+M+Y+A.

[0049] (1) J: Base fertilizer;

[0050] (2) J+M: Base fertilizer + magnesium manganese ammonium sulfate double salt crystals;

[0051] (3) J+Y: Base fertilizer + liquid fertilizer of this invention;

[0052] (4) J+A: Base fertilizer + methionine;

[0053] (5) J+M+Y: Base fertilizer + magnesium manganese ammonium sulfate double salt crystals + liquid fertilizer of this invention;

[0054] (6) J+M+A: Base fertilizer + magnesium manganese ammonium sulfate double salt crystals + methionine;

[0055] (7) J+Y+A: Base fertilizer + liquid fertilizer of this invention + methionine;

[0056] (8) J+M+Y+A: Base fertilizer + magnesium manganese ammonium sulfate double salt crystals + liquid fertilizer of this invention + methionine.

[0057] Experimental methods:

[0058] The base fertilizer was a commercially available general-purpose compound fertilizer for corn (ordinary N15-P15-K15 ternary fertilizer) from Jiajiajia Co., Ltd. Eight experimental groups were designed. Before the experiment, high-quality corn seeds of uniform appearance were selected, soaked in water to promote germination, and then used. 3L round plastic flowerpots of uniform size (18cm top diameter, 13cm bottom diameter, 16cm height) were used. Each pot was filled with 2.8kg of air-dried soil pre-mixed with 3.0g of base fertilizer, and 5 seeds were sown in each pot at a depth of 2.5cm.

[0059] Take 10 mL of organic-inorganic compound liquid fertilizer stock solution for a single drip irrigation, and dilute it 1000 times with water to prepare the Y component reference dilution working solution;

[0060] Methionine was prepared in advance as a 1.0% (w / v, g / mL) methionine aqueous solution. For each drip irrigation of the methionine treatment group, 10.5 mL of this methionine stock solution was taken and mixed into the working solution.

[0061] Magnesium manganese ammonium sulfate double salt crystals were prepared by dissolving 1000g of magnesium manganese ammonium sulfate double salt crystals in 3000mL of water to form an aqueous solution of magnesium manganese ammonium sulfate double salt crystals. For each drip irrigation, 9mL of the aqueous solution of magnesium manganese ammonium sulfate double salt crystals was taken and mixed into the drip irrigation working solution.

[0062] The eight treatment groups were administered the corresponding components according to their factor combinations: Group J was administered only with an equal volume of water; Group J+M was administered 9 mL of magnesium manganese ammonium sulfate double salt crystals aqueous solution; Group J+Y was administered 10 mL of the working solution diluted 1000 times to the original solution; Group J+A was administered 10.5 mL of 1.0% (w / v, g / mL) methionine aqueous solution; and the composite groups were administered the corresponding components according to their combinations.

[0063] All experimental groups used deionized water to bring the total solution for drip irrigation to the same volume to achieve equal-volume irrigation. The base fertilizer uniformly provided phosphorus and potassium nutrients. This experiment investigated the factor effects of magnesium manganese ammonium sulfate double salt crystals, liquid fertilizer, and methionine, without deducting nitrogen, magnesium, and manganese element balances. Methionine, as a biostimulant, did not include the nitrogen and sulfur it introduced in the fertilizer nutrient statistics. Foliar spraying could be used as an auxiliary treatment during the seedling stage, with the foliar spraying volume remaining consistent across groups. This experiment used the organic-inorganic compound liquid fertilizer prepared in Example 3 to conduct a pot experiment on maize.

[0064] Indicator measurement methods:

[0065] Corn leaf count: Regular observations will be conducted from the date when the corn seedlings have stabilized. The number of functional leaves unfolded in each pot of corn will be counted every 7 days. The criteria for judging a valid leaf are that the ligule of the leaf is fully exposed and the leaf is fully unfolded. Curled, withered, and aged lower leaves will not be included in the count.

[0066] Leaf SPAD value: The SPAD-502 chlorophyll meter was used for in vivo non-destructive testing, without the need to collect leaves. For each leaf measurement, the second fully unfolded functional leaf from the top of the corn plant was selected, avoiding the main vein. Measurements were taken at three locations: the leaf base, the middle of the leaf, and the leaf tip. The average of the three readings for a single leaf was taken as the SPAD value of that leaf.

[0067] Microbial richness index: After corn harvest, rhizosphere soil was collected, microbial DNA was extracted and high-throughput sequencing was performed, and the Chao1 richness index was calculated through Alpha diversity to evaluate the regulatory effect of each group of fertilizers on the level of soil microbial species richness.

[0068] Experimental results:

[0069] 1. The effects of different fertilizers on the number of corn leaves, such as... Figure 4 As shown, the effects of different treatments on leaf number gradually became apparent over time, with significant differences appearing on day 35, and these differences gradually increasing. All treatment groups were superior to the basal fertilizer group. Final seedling stage results: The single-treatment groups (J+M, J+Y, J+A) showed no significant difference compared to group J; the pairwise treatment groups (J+M+Y, J+Y+A) were superior to group J, with group J+Y+A being the best; the treatment group (J+M+Y+A) was significantly superior to group J and also superior to all other treatment groups. Therefore, combined treatment is most beneficial for promoting plant growth.

[0070] 2. The effects of different fertilizers on SPAD, such as Figure 5 As shown: In the early seedling stage, chlorophyll content gradually increases, reaching its highest level on day 21, and gradually decreases in the later stages, possibly related to plant growth and changes in environmental conditions. Single-addition groups: In the first 21 days, compared to group J (with basal fertilizer), adding liquid organic fertilizer (J+Y) promoted chlorophyll synthesis, while the groups adding magnesium manganese ammonium sulfate double salt crystals and methionine showed no significant difference from the basal fertilizer group; however, as time progressed, the magnesium manganese ammonium sulfate double salt crystals group also showed a better enhancement effect. Paired-addition groups: In the first 21 days, group J+M+A showed the best effect, significantly higher than groups J and J+Y, meaning that the combined application of magnesium manganese ammonium sulfate double salt crystals and methionine significantly promoted chlorophyll synthesis; however, as time progressed, group J+Y+A also showed a good promoting effect.

[0071] 3. The effects of different fertilizers on the richness index, such as... Figure 6As shown: Individual addition groups: Compared with single application of basal fertilizer (J), soil microbial species richness was increased under individual addition of M, Y, and A treatments, but the differences were not statistically significant. Paired treatment groups: In the paired application treatments, the microbial species richness of the J+M+A and J+M+Y treatments was significantly higher than that of the J treatment, while the J+Y+A treatment showed an upward trend, but the difference was not statistically significant. Overall, paired application enhanced the promoting effect on microbial species richness to some extent. Complete addition group: The microbial species richness of the three-factor combined application (J+M+Y+A) treatment was significantly higher than that of the J treatment, and the results were similar to those of the J+M+A and J+M+Y groups, indicating that the combined application of magnesium manganese ammonium sulfate double salt crystals has a certain promoting effect on improving microbial community richness. Correlation analysis results showed that there was a highly significant correlation between alkaline available nitrogen and richness; the combined application of magnesium manganese ammonium sulfate double salt crystals significantly increased alkaline available nitrogen, thus significantly affecting the change of this index.

[0072] This invention features a simple and gentle process that thoroughly removes impurities without secondary pollution. The resulting organic-inorganic compound liquid fertilizer is nutrient-balanced, safe, and stable. Under certain application conditions, it not only significantly improves the growth rate of corn leaves and the SPAD value of chlorophyll but also promotes the enrichment of the microbial community. It achieves the harmless, reduced-volume, and high-value utilization of electrolytic manganese slag, combining the triple functions of solid waste resource utilization, crop growth promotion, and soil ecological restoration. Suitable for integrated water and fertilizer application, it possesses significant economic, environmental, and social benefits and is suitable for large-scale production and promotion.

[0073] The conventional techniques and solutions not described in detail in the above embodiments are all well known in the art, and therefore will not be elaborated upon here. The above embodiments and / or experimental examples describe the preferred embodiments of the present invention in detail. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing an organic-inorganic composite liquid fertilizer based on the resource utilization of solid waste from manganese ore mining, characterized in that, Includes the following steps: (1) Compound supplementation: Add 1000g of magnesium manganese ammonium sulfate double salt crystals to every 3000mL of decoupling solution obtained by oxidizing and decoupling manganese slag with ammonium persulfate to obtain a qualified solution; (2) Deep purification: Adjust the pH of the qualified solution to 5.0 with NH4OH and stir for 30 min. After standing for 15 min, filter to remove the precipitate. Then add 300% of the theoretical amount of (NH4)2S, react at 50℃ for 45 min, cool to room temperature, filter, and obtain the purified solution. (3) Organic acid complexation: Add natural organic acid to the purified liquid so that its total mass fraction in the final mixture is 4%, and carry out the complexation reaction at 25–45℃ for 20–90 min to form a stable complexation system; (4) Formulation: Adjust the pH of the complexing solution to 5.5–7.0, and make up the volume with water to obtain organic-inorganic compound liquid fertilizer. The volume of the make-up is calculated as 5L per 3000mL of decoupling solution.

2. The method as described in claim 1, characterized in that, The natural organic acid is one or more of citric acid, malic acid, tartaric acid, and oxalic acid.

3. An organic-inorganic composite liquid fertilizer based on the resource utilization of solid waste from manganese ore mining, characterized in that, The organic-inorganic compound liquid fertilizer is prepared by the method described in claim 1 or 2.

4. The application of the organic-inorganic compound liquid fertilizer according to claim 3 in promoting plant leaf growth and / or promoting plant chlorophyll synthesis and / or promoting soil microbial species richness.

5. The method of applying the organic-inorganic compound liquid fertilizer according to claim 3 in promoting plant leaf growth and / or promoting plant chlorophyll synthesis and / or promoting soil microbial species richness, characterized in that, Includes the following steps: (1) Fill the flowerpot with 2.8 kg of air-dried soil, mix in 3.0 g of base fertilizer, and plant the seeds; (2) When applying the fertilizer once, take 10 mL of organic-inorganic compound liquid fertilizer, dilute it with water 1000 times to form a working solution, add at least one of methionine aqueous solution and magnesium manganese ammonium sulfate double salt crystal aqueous solution to the working solution to form a mixed solution; the amount of methionine aqueous solution added is 10.5 mL, and the amount of magnesium manganese ammonium sulfate double salt crystal aqueous solution added is 9 mL. (3) Apply the above mixed solution to the roots of the plant by drip irrigation.

6. The method as described in claim 5, characterized in that, The concentration of the methionine aqueous solution is 1.0% (w / v), and the magnesium manganese ammonium sulfate double salt crystal aqueous solution is prepared by mixing 1000g of magnesium manganese ammonium sulfate double salt crystal with 3000mL of water.

7. The method as described in claim 5, characterized in that, It also includes foliar spraying of the mixed solution during the seedling stage of the plant.

8. The method as described in claim 5, characterized in that, The plant in question is corn.

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