Resourceful treatment process for manganese slag field leachate

Abstract

The invention discloses a resourceful treatment process for manganese slag field leachate, which comprises the following steps: adding a carbonate solution, an inorganic alkali solution, a carbonate solution, lime emulsion and a carbonate solution step by step, respectively precipitating to obtain manganese carbonate, manganese dioxide, magnesium carbonate, gypsum and calcium magnesium carbonate, and adding sulfuric acid or nitric acid into the filtrate to obtain nitrogen fertilizer water. The fertilizer is used as fertilizer for greening the surface of the slag yard and does not need to be discharged. Manganese ions, magnesium ions and SO4 < 2-> in the leachate of the manganese slag field are treated and recycled step by step to form available / sold byproducts, and finally tail water is used as fertilizer water for greening the reservoir surface of the manganese slag field, so that resourceful treatment and utilization of the leachate of the manganese slag field are realized to the greatest extent.

Description

Technical Field

[0001] The invention relates to the technical field of environmental protection, and in particular to a resource processing process for leachate from a manganese slag field. Background Art

[0002] Manganese resources are one of the important strategic minerals and are widely used in steel production, non-ferrous metal alloys, aerospace, electronic technology, new energy materials and other fields. Manganese slag yards are the main places for the manganese industry to landfill and dispose of manganese slag, and are also one of the main sources of environmental pollution in the manganese industry. During the landfill period of manganese slag, leachate will continue to be produced. The leachate contains high concentrations of manganese, ammonia nitrogen, magnesium and other ions. If it is not collected and treated, it will seriously pollute the surrounding soil and water.

[0003] Patent application CN 109851084 A discloses a resource-based treatment method for reducing the content of ammonia nitrogen, calcium and magnesium ions in manganese-containing wastewater, comprising: adjusting the pH value of manganese-containing wastewater at a temperature of 35°C-95°C to 9.0-10.5 with lime; slowly adding Mn(H2PO4)2·2H2O to the manganese-containing wastewater under stirring conditions, and performing solid-liquid separation to obtain struvite precipitate MgNH4PO4·6H2O and a first filtrate; adding MnSO4 to the first filtrate, stirring, and performing solid-liquid separation to obtain a second filtrate; the second filtrate is adsorbed and oscillated by adsorption materials such as zeolite, medical stone, coal slag, and vermiculite to obtain a third filtrate; and after the third filtrate is concentrated, crystallized, washed, and dried, a manganese sulfate solid with low content of ammonia nitrogen, calcium and magnesium ions is obtained. This method can obtain struvite precipitate MgNH4PO4·6H2O and manganese sulfate solid, and recover manganese and ammonia resources in wastewater, but the Mn(H2PO4)2·2H2O reagent used is not easy to obtain, and the treated wastewater still needs further treatment.

[0004] Patent application CN 116332436 A discloses a method for treating manganese-containing wastewater, wherein the manganese-containing wastewater is pre-oxidized, and then a manganese removal agent is added to remove manganese ions from the manganese-containing wastewater through a process of coordination reaction, neutralization reaction, flocculation reaction, and solid-liquid separation. This method has many steps, a long process, a large amount of slag, and a low manganese content in the slag, which is not conducive to reuse.

[0005] Patent application CN 107522324 A discloses a process for recovering manganese from electrolytic manganese production wastewater and comprehensive treatment of wastewater and waste gas, including chromium-containing wastewater and polishing wastewater, manganese recovery treatment, and sulfate treatment. The manganese recovery process is to first add sodium hydroxide to the wastewater to adjust the pH to 7-8, then add 1.5 times the chemical reaction amount of ammonium bicarbonate to precipitate Mn 2+, manganese carbonate is generated, and after precipitation and separation, the manganese carbonate slag enters the production system for reuse. After the wastewater is treated to meet the water quality requirements for production water, it is returned to the production system for use. This method uses ammonium bicarbonate, which will increase the subsequent ammonia treatment load of the wastewater. At the same time, the precipitate is a mixture of manganese, magnesium, and calcium. Returning it to the production system for reuse will destroy the salt balance of the ecosystem and affect the stability of the production system. In addition, for the legacy manganese slag sites that have been closed and withdrawn by many production enterprises, the treated wastewater has no production system to accept it and still needs further treatment.

[0006] In summary, the existing methods for treating leachate from manganese slag sites have problems such as the difficulty in obtaining reagents, the low manganese content in the by-products making them difficult to utilize, and the need for further treatment of the treated wastewater. Summary of the invention

[0007] The inventors have found that for the leachate from the manganese slag yard, by adding carbonate solution, non-electrode alkali solution, carbonate solution, lime emulsion and carbonate solution in steps, manganese carbonate, manganese dioxide, magnesium carbonate, gypsum and calcium magnesium carbonate are precipitated respectively, and then sulfuric acid or nitric acid is added to the filtrate to obtain nitrogen fertilizer water, which is used as fertilizer water for greening the slag yard surface without being discharged, thereby maximizing the resource utilization of the leachate from the manganese slag yard, thereby completing the present invention.

[0008] The object of the present invention is to provide a process for resource recovery of leachate from a manganese slag field, comprising the following steps:

[0009] (1) adding sodium carbonate solution to the leachate from the manganese slag field at a uniform rate under stirring until the pH of the reaction solution reaches 8.5-9.0, filtering, and collecting the magnesium carbonate precipitate and the filtrate;

[0010] (2) adding sodium hydroxide solution to the filtrate 1, controlling the pH value of the solution to be stable at 8.7-9.0, aerating the solution, filtering the solution, and obtaining manganese dioxide precipitate and filtrate 2;

[0011] (3) adding sodium carbonate solution to the filtrate 2 at one time, wherein the amount of sodium carbonate is 1.0-1.2 times the chemical reaction equivalent of magnesium in the leachate of the manganese slag field, and filtering by sedimentation to collect the magnesium carbonate precipitate and the filtrate 3;

[0012] (4) Add lime emulsion to the filtrate 3, where the amount of calcium is the SO4 2- 0.9-1.0 times of the chemical reaction equivalent, filtering to obtain gypsum precipitate and filtrate 4;

[0013] (5) Slowly adding sodium carbonate solution to the filtrate 4 under stirring until the pH of the reaction solution is ≥11, filtering to obtain calcium magnesium carbonate and filtrate 5;

[0014] (6) Add sulfuric acid or nitric acid to the filtrate 5 to adjust the pH to 6-9 to obtain nitrogen fertilizer water.

[0015] The leachate from the manganese slag field to be treated by the present invention has a pH of 5-7, a manganese ion content of 800-1500 mg / L, a magnesium ion content of 400-800 mg / L, and NH4 + Content: 600-1000mg / L.

[0016] In a preferred embodiment, in step (1), the mass concentration of the sodium carbonate solution used is 10%-20%, more preferably about 10%, and the stirring rate is 15-30r / min, more preferably about 15r / min, so that the reaction proceeds evenly and the reaction system solution is uniform.

[0017] In step (1), when the pH of the reaction system solution reaches 8.5-9.0, manganese carbonate can be effectively precipitated, the manganese concentration in the filtrate is reduced to below 50 mg / L, and calcium and magnesium ions are not precipitated, which is convenient for full resource utilization.

[0018] At this time, filter as soon as possible to separate the manganese carbonate precipitate and the filtrate. Studies have found that the manganese ions precipitated in the form of manganese carbonate can reach more than 43% of the total manganese ions in the leachate of the manganese slag field, and the obtained manganese carbonate can be sold as an industrial raw material with high resource utilization.

[0019] In a preferred embodiment, in step (2), the pH of the solution is controlled to be stable at 8.7-9.0 by slowly adding sodium hydroxide solution, and the reaction is carried out by explosion. The reaction time is preferably 20-40 minutes, more preferably about 20 minutes. At this time, the manganese in the filtrate 1 is precipitated in the form of manganese dioxide, and the manganese ion concentration in the filtrate 2 is reduced to below 5.0 mg / L, so that manganese is fully precipitated further.

[0020] The study found that manganese ions precipitated in the form of manganese dioxide accounted for more than 39% of the total manganese ions in the leachate of manganese slag field. Manganese dioxide can be sold as an industrial raw material with high resource utilization.

[0021] In a preferred embodiment, in step (3), by adding sodium carbonate in an amount of 1.0-1.2 times the chemical equivalent of magnesium ions, stirring for sufficient reaction, such as 20-60 minutes, and sufficient sedimentation, such as 4-6 hours, the magnesium carbonate is fully precipitated and the manganese ions are further precipitated. At this time, the manganese ion concentration in the filtrate three is reduced to below 2.0 mg / L, and the magnesium ion concentration is reduced to below 20.0 mg / L.

[0022] The study found that the precipitation by-product precipitated in the form of magnesium carbonate, in which magnesium ions account for more than 25% of the total magnesium ions in the leachate of the manganese slag field, is doped with a very small amount of manganese carbonate. The magnesium carbonate by-product can be sold as an industrial raw material with high resource utilization.

[0023] In a preferred embodiment, in step (4), after adding the lime milk, the reaction is continued to be stirred for at least 2 hours, such as 2-3 hours, so that the gypsum is fully precipitated.

[0024] Research has found that the gypsum obtained in step (4) has a CaSO4·2H2O content of more than 90%, and can be directly sold as an industrial raw material.

[0025] In a preferred embodiment, in step (5), sodium carbonate is added to control the pH of the reaction solution to be ≥11, preferably about 11.5-12.0, so that calcium and magnesium in the solution can react and precipitate. Furthermore, in order to promote the full reaction of calcium and magnesium, stirring is continued for at least 4 hours, such as 4-6 hours.

[0026] The calcium magnesium carbonate obtained in step (5) is discharged as solid waste.

[0027] In a preferred embodiment, in step (6), the pH is adjusted to 6-9, preferably about 7, by adding dilute sulfuric acid or dilute nitric acid to obtain nitrogen fertilizer water.

[0028] The nitrogen fertilizer water has good water quality and can be directly used as wastewater for on-site greening of the manganese slag site without discharge, thus maximizing resource utilization.

[0029] Furthermore, the process of the present invention also includes step (7) utilization of nitrogen fertilizer water for irrigation: the nitrogen fertilizer water obtained in step (6) is used as fertilizer water for greening the surface of the manganese slag field, with a single application amount of 480m3 / ha, and each application interval of 7 days, and the greening plants grow well.

[0030] The present invention has the following advantages:

[0031] (1) The present invention recovers manganese ions, magnesium ions, SO4 in the leachate of manganese slag field by step-by-step treatment. 2- , forming usable / saleable by-products, and finally the tail water is used as fertilizer water for greening the manganese slag field reservoir, maximizing the resource utilization of the manganese slag field leachate;

[0032] (2) The tail water treated by the present invention is used as fertilizer water for greening the manganese slag field, and the water quality is good. It does not need to rely on production process for reuse or to be treated to meet standards, and has a wide range of applications;

[0033] (3) The materials used in the present invention are low in price, the process conditions are easy to control and operate, and except for the calcium magnesium carbonate obtained in step (5) which is solid waste, there is almost no other waste, and the environmental protection effect is remarkable. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The preferred embodiment of the process of the present invention is shown DETAILED DESCRIPTION

[0035] The present invention is further described in detail below through the accompanying drawings and preferred embodiments. Through these descriptions, the characteristics and advantages of the present invention will become more clear and distinct.

[0036] Example 1

[0037] (1) 100 L of leachate from a manganese slag field was taken, and a sodium carbonate solution having a mass concentration of 10% was uniformly added to the leachate under stirring at a stirring rate of 15 r / min. When the pH of the reaction solution was 8.5-8.7, the addition of the sodium carbonate solution was stopped, and a first filtration was immediately performed to obtain a manganese carbonate byproduct and a filtrate 1, wherein the manganese concentration in the filtrate 1 was reduced to 48 mg / L;

[0038] (2) slowly adding sodium hydroxide solution to the filtrate 1, controlling the solution pH to be stable at 8.7-9.0, performing an explosion reaction for 20 minutes, and performing secondary filtration to obtain a manganese dioxide byproduct and a filtrate 2, wherein the manganese concentration in the filtrate 2 is reduced to 5.0 mg / L;

[0039] (3) adding sodium carbonate solution to the filtrate 2 at one time, the amount of which is 1.0 times the chemical reaction equivalent of magnesium ions in the leachate from the manganese slag field, stirring the reaction for 20 minutes, transferring the solution to a clarification tank and continuing sedimentation for 4 hours, detecting the manganese ion concentration of 1.7 mg / L and the magnesium ion concentration of 19 mg / L in the supernatant, filtering the solution three times to obtain a magnesium carbonate byproduct and the filtrate 3;

[0040] (4) Add lime emulsion to the filtrate 3, the amount added is equal to the SO4 2- The chemical reaction volume was 1.0 times, and the reaction was continued with stirring for 2 hours. The gypsum byproduct and filtrate 4 were obtained by filtration four times;

[0041] (5) slowly adding sodium carbonate solution to the filtrate 4, stirring the reaction, stopping adding sodium carbonate solution when the pH of the reaction solution is 11.5, continuing stirring the reaction for 4 hours, filtering five times, and obtaining calcium and magnesium solid waste and filtrate 5;

[0042] (6) adding dilute sulfuric acid to the filtrate 5 until the pH reaches 7 to obtain nitrogen fertilizer water;

[0043] (7) Use nitrogen fertilizer water as fertilizer water for greening the slag dump surface, with a single application rate of 480m3 / ha, and an interval of 7 days between each application. In case of rainy weather, the application period will be postponed to prevent the nitrogen fertilizer water from overflowing from the slag dump and entering the river.

[0044] Example 2

[0045] (1) taking 100 L of leachate from a manganese slag field, adding a sodium carbonate solution having a mass concentration of 20% to the leachate at a uniform rate under stirring, with a stirring rate of 20 r / min, and stopping the addition of the sodium carbonate solution when the pH of the reaction solution is 8.7-9.0, and immediately performing a primary filtration to obtain a manganese carbonate byproduct and a filtrate 1, wherein the manganese concentration in the filtrate 1 is reduced to 44 mg / L;

[0046] (2) slowly adding sodium hydroxide solution to the filtrate 1, controlling the solution pH to be stable at 8.7-9.0, performing an explosion reaction for 40 minutes, and performing secondary filtration to obtain a manganese dioxide byproduct and a filtrate 2, wherein the manganese concentration in the filtrate 2 is reduced to 3.2 mg / L;

[0047] (3) adding sodium carbonate solution to the filtrate 2 at one time, the added amount being 1.2 times the chemical reaction equivalent of magnesium ions in the leachate from the manganese slag field, stirring the reaction for 60 minutes, transferring the solution to a clarification tank and continuing sedimentation for 6 hours, detecting the manganese ion concentration of 1.2 mg / L and the magnesium ion concentration of 12 mg / L in the supernatant, and filtering the solution three times to obtain a magnesium carbonate byproduct and a filtrate 3;

[0048] (4) Add lime emulsion to the filtrate 3, the amount added is equal to the SO4 2- The chemical reaction volume was 1.0 times, and the reaction was continued with stirring for 3 hours. The gypsum byproduct and filtrate 4 were obtained by filtration for four times;

[0049] (5) slowly adding sodium carbonate solution to the filtrate 4, stirring the reaction, stopping adding sodium carbonate solution when the pH of the reaction solution is 11.8, continuing stirring the reaction for 6 hours, filtering five times, and obtaining calcium and magnesium solid waste and filtrate 5;

[0050] (6) adding dilute nitric acid to the filtrate 5 until the pH reaches 7 to obtain nitrogen fertilizer water;

[0051] (7) Use nitrogen fertilizer water as fertilizer water for greening the slag dump surface, with a single application rate of 440 m3 / ha, and an interval of 7 days between each application. In case of rainy weather, the application period will be postponed to prevent the nitrogen fertilizer water from overflowing from the slag dump and entering the river.

[0052] Example 3

[0053] (1) taking 100 L of leachate from a manganese slag field, adding a sodium carbonate solution having a mass concentration of 15% to the leachate at a uniform rate under stirring, with a stirring rate of 30 r / min, and stopping the addition of the sodium carbonate solution when the pH of the reaction solution is 8.8-9.0, and immediately performing a primary filtration to obtain a manganese carbonate byproduct and a filtrate 1, wherein the manganese concentration in the filtrate 1 is reduced to 36 mg / L;

[0054] (2) slowly adding sodium hydroxide solution to the filtrate 1, controlling the solution pH to be stable at 8.7-9.0, performing an explosion reaction for 60 minutes, and performing secondary filtration to obtain a manganese dioxide byproduct and a filtrate 2, wherein the manganese concentration in the filtrate 2 is reduced to 2.1 mg / L;

[0055] (3) adding sodium carbonate solution to the filtrate 2 at one time, the added amount being 1.2 times the chemical reaction equivalent of magnesium ions in the leachate from the manganese slag field, stirring the reaction for 60 minutes, transferring the solution to a clarification tank and continuing sedimentation for 6 hours, detecting the manganese ion concentration of 1.6 mg / L and the magnesium ion concentration of 14 mg / L in the supernatant, and filtering the solution three times to obtain a magnesium carbonate byproduct and a filtrate 3;

[0056] (4) Add lime emulsion to the filtrate 3, the amount added is equal to the SO4 2- The chemical reaction volume was 0.9 times, and the reaction was continued with stirring for 3 hours. The gypsum byproduct and filtrate 4 were obtained by filtration for four times;

[0057] (5) slowly adding sodium carbonate solution to the filtrate 4, stirring the reaction, stopping adding sodium carbonate solution when the pH of the reaction solution is 12, continuing stirring the reaction for 4 hours, filtering five times, and obtaining calcium and magnesium solid waste and filtrate 5;

[0058] (6) adding dilute nitric acid to the filtrate 5 until the pH reaches 7 to obtain nitrogen fertilizer water;

[0059] (7) The nitrogen fertilizer water shall be used as fertilizer water for greening the slag dump surface, with a single application rate of 520 m3 / ha, and each application interval of 7 days. In case of rainy weather, the application shall be postponed to prevent the nitrogen fertilizer water from overflowing from the slag dump and entering the river.

[0060] Test example

[0061] The quality of the by-products obtained in Examples 1-3 was tested, and the results are shown in Table 1 below.

[0062] Table 1 Quality of by-products

[0063]

[0064] Comparative Example 1

[0065] (1) 100 L of manganese slag field leachate is taken, and a 15% sodium carbonate solution having a mass concentration of 1.2 times the chemical reaction equivalent of manganese, magnesium and calcium ions in the manganese slag field leachate is added at one time, and the mixture is stirred for reaction for 60 min, and then filtered to obtain a manganese and magnesium byproduct and a filtrate 1, wherein the manganese and magnesium byproduct has a total manganese content of 8%, a divalent manganese content of 4%, and a total magnesium content of 5% (the total manganese content is low, and the divalent manganese and total magnesium contents are high, so it is not suitable for use);

[0066] (2) The filtrate was adjusted to pH 12 using dilute nitric acid (Mn 2+≤2.0mg / L, total concentration of calcium and magnesium ions ≤50.0mg / L), the ammonia nitrogen is treated by air stripping method and then meets the discharge standards.

[0067] Comparative Example 2

[0068] (1) 100 L of manganese slag field leachate was taken, and a 15% sodium carbonate solution with a mass concentration of 1.0 times the chemical reaction equivalent of manganese ions in the manganese slag field leachate was added at one time, and the mixture was stirred for reaction for 60 minutes, and then filtered to obtain a manganese carbonate product (total manganese content 20%, divalent manganese content 14%, total magnesium content 4%) and a filtrate 1;

[0069] (2) adding a 15% sodium carbonate solution having a chemical reaction equivalent of 1.0 times the magnesium ion in the manganese slag field leachate to the filtrate 1 at one time, stirring the reaction for 60 minutes, filtering to obtain a magnesium carbonate byproduct and a filtrate 2, wherein the magnesium carbonate byproduct has a total manganese content of 6% and a total magnesium content of 9% (the total manganese content is low, and the divalent manganese and total magnesium contents are high, so it is not suitable for use);

[0070] (3) The pH of the filtrate 2 was adjusted to 12 with dilute nitric acid (Mn 2+ ≤2.0mg / L, total concentration of calcium and magnesium ions ≤50.0mg / L), the ammonia nitrogen is treated by air stripping method and then meets the discharge standards.

[0071] The present invention has been described in detail above in conjunction with preferred embodiments and exemplary examples. However, it should be noted that these specific embodiments and examples are only illustrative explanations of the present invention and do not constitute any limitation on the protection scope of the present invention. Without exceeding the spirit and protection scope of the present invention, various improvements, equivalent substitutions or modifications may be made to the technical content of the present invention and its implementation methods, all of which fall within the protection scope of the present invention. The protection scope of the present invention shall be subject to the attached claims.

Claims

1. A process for recycling leachate from a manganese slag site, comprising the steps of adding a carbonate solution, an alkali-free solution, a carbonate solution, a lime emulsion and a carbonate solution to precipitate manganese carbonate, manganese dioxide, magnesium carbonate, gypsum and calcium magnesium carbonate, and then adding sulfuric acid or nitric acid to the filtrate to obtain nitrogen fertilizer water, which is used as fertilizer water for greening the slag site without being discharged.

2. The process for recycling leachate from a manganese slag field as claimed in claim 1, comprising the following steps: (1) adding sodium carbonate solution to the leachate from the manganese slag field at a uniform rate under stirring until the pH of the reaction solution reaches 8.5-9.0, filtering, and collecting the magnesium carbonate precipitate and the filtrate; (2) adding sodium hydroxide solution to the filtrate 1, controlling the pH value of the solution to be stable at 8.7-9.0, aerating the solution, filtering the solution, and obtaining manganese dioxide precipitate and filtrate 2; (3) adding sodium carbonate solution to the filtrate 2 at one time, wherein the amount of sodium carbonate is 1.0-1.2 times the chemical reaction equivalent of magnesium in the leachate of the manganese slag field, and filtering by sedimentation to collect the magnesium carbonate precipitate and the filtrate 3; (4) Add lime emulsion to the filtrate 3, where the amount of calcium is the SO4 2- 0.9-1.0 times of the chemical reaction equivalent, filtering to obtain gypsum precipitate and filtrate 4; (5) Slowly adding sodium carbonate solution to the filtrate 4 under stirring until the pH of the reaction solution is ≥11, filtering to obtain calcium magnesium carbonate and filtrate 5; (6) Add sulfuric acid or nitric acid to the filtrate 5 to adjust the pH to 6-9 to obtain nitrogen fertilizer water.

3. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (1), the mass concentration of the sodium carbonate solution used is 10%-20%, more preferably about 10%, and the stirring rate is 15-30r / min, more preferably about 15r / min.

4. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (1), the manganese concentration in the filtrate 1 is reduced to below 50 mg / L.

5. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (2), the pH of the solution is controlled to be stable at 8.7-9.0 by slowly adding sodium hydroxide solution, and the reaction is carried out by explosion. The reaction time is preferably 20-40 minutes, more preferably about 20 minutes.

6. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (2), the manganese ion concentration in the second filtrate is reduced to below 5.0 mg / L.

7. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (3), sodium carbonate in an amount of 1.0-1.2 times the chemical equivalent of magnesium ions is added, and the mixture is stirred for sufficient reaction, such as 20-60 minutes, and allowed to settle sufficiently, such as 4-6 hours, so that magnesium carbonate is fully precipitated.

8. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (3), the manganese ion concentration in the filtrate three is reduced to below 2.0 mg / L, and the magnesium ion concentration is reduced to below 20.0 mg / L.

9. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (4), after adding the lime milk, the reaction is continued with stirring for at least 2 hours, such as 2-3 hours, and the content of CaSO4·2H2O in the obtained gypsum reaches more than 90%.

10. The process for recycling leachate from a manganese slag field as claimed in claim 2, wherein: In step (5), sodium carbonate is added to control the pH of the reaction solution to be ≥11, preferably 11.5-12.0, and stirring is continued for at least 4 hours, such as 4-6 hours.

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