A method for treating coal gangue

Abstract

The invention discloses a method for treating coal gangue, and belongs to the technical field of coal gangue resource utilization. The method for treating coal gangue disclosed by the invention comprises the following steps: 1) pretreatment with sodium carbonate and hydrochloric acid; 2) primary modification by calcination; 3) secondary modification by mixed acid; 4) chitosan solidification. The modified coal gangue obtained by the invention has a good removal effect on metals in industrial wastewater, and its removal rate for copper can reach 98.95%, the removal rate for zinc can reach 98.05%, the removal rate for chromium can reach 99.98%, the removal rate for cadmium can reach 99.98%, the removal rate for lead can reach 99.94%, and the removal rate for mercury can reach 99.99%.

Description

Technical Field

[0001] The invention belongs to the technical field of coal gangue resource utilization, and particularly relates to a method for processing coal gangue. Background Art

[0002] With the development of mining, smelting, chemical industry, electronics and other industries, as well as the unreasonable landfill and stacking of civilian solid waste, various heavy metals have entered the water. Heavy metals are highly stable and difficult to degrade in water. When they accumulate to a certain limit in the water, they will cause serious harm to the water.

[0003] Coal gangue is a kind of black muddy rock with high ash content, low carbon content, low calorific value, and harder than coal, which is produced with coal seams during the coal formation process and removed during the production of raw coal in coal mines. Coal gangue is abandoned and piled in the open air to form gangue mountains. The escape or leaching of harmful substances in it will pollute the atmosphere, farmland and water bodies, causing environmental pollution, and can also enter the human body through environmental media, threatening human health.

[0004] Coal gangue contains a large amount of carbon, silicon, aluminum and other elements, which makes it possible for coal gangue to absorb heavy metals in water and achieve "waste treatment with waste". However, the structure of coal gangue is dense and cannot directly absorb heavy metals. Therefore, further processing of coal gangue has become the key to using coal gangue to absorb heavy metals in water. Summary of the invention

[0005] In order to solve the above problems in the prior art, the present invention provides a method for processing coal gangue.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention: a method for treating coal gangue, comprising the following steps:

[0008] 1) Pretreatment: Mixing coal gangue with sodium carbonate to obtain a coal gangue-sodium carbonate mixture, and subjecting the coal gangue-sodium carbonate mixture to low-temperature calcination and hydrochloric acid impurity removal to obtain pretreated coal gangue;

[0009] 2) primary modification: calcining the pretreated gangue obtained in step 1) at high temperature to obtain primary modified gangue;

[0010] 3) Secondary modification: the primary modified coal gangue obtained in step 2) is subjected to mixed acid modification in a mixed acid modification solution to obtain secondary modified coal gangue;

[0011] 4) Solidification: Spray the chitosan solution onto the surface of the secondary modified coal gangue prepared in step 3), and calcine to obtain modified coal gangue.

[0012] Furthermore, in step 1), the mass ratio of the coal gangue to sodium carbonate is 10:(3-4).

[0013] Furthermore, in step 1), the low-temperature calcination is to control the water content of the gangue-sodium carbonate mixture to 20% to 30%, and calcine at 100 to 140° C. for 30 to 40 minutes.

[0014] Furthermore, in step 1), the hydrochloric acid impurity removal is to mix the low-temperature calcined coal gangue-sodium carbonate mixture with hydrochloric acid, and wash the precipitate with water.

[0015] Furthermore, the concentration of the hydrochloric acid is 4 mol / L, and the mass volume ratio of hydrochloric acid to coal gangue is 1 g: 5-10 mL; and the water washing is water washing until the pH value of the water washing liquid is 7.

[0016] Furthermore, step 2) is carried out in a nitrogen protective atmosphere.

[0017] Furthermore, in step 2), the high temperature calcination is calcined at 700-1000° C. for 20-50 min.

[0018] Furthermore, in step 3), the mixed acid modification solution is prepared by mixing 3 mol / L sulfuric acid solution and 6 mol / L acetic acid solution in a volume ratio of 3:5.

[0019] Furthermore, in step 3), the mixed acid modification is mixed acid reflux modification at 100-130° C. for 1-2 hours.

[0020] Furthermore, in step 4), the chitosan solution is prepared by dissolving chitosan in 0.2 mol / L acetic acid solution at a solid-liquid ratio of 1 mg:5 mL.

[0021] Furthermore, in step 4), the calcination is carried out at 300-500° C. for 10-20 min.

[0022] The second technical solution of the present invention: modified coal gangue obtained by the above-mentioned method for treating coal gangue.

[0023] The third technical solution of the present invention: application of the modified coal gangue in adsorbing heavy metals in water.

[0024] Modification principle of the present invention:

[0025] The present invention mixes sodium carbonate with coal gangue before the primary modification, and calcines the coal gangue-sodium carbonate mixture while controlling the water content after the mixture; the addition of sodium carbonate and the water-containing calcination can effectively remove the impurity in the coal gangue, namely pyrite, and the sulfur element in the pyrite is first converted into sulfur dioxide or sulfur trioxide through calcination, and then converted into sulfurous acid or sulfuric acid by combining sodium carbonate and water, so as to achieve the removal of pyrite. Since pyrite has a dense structure and is not easy to modify, and calcination is easy to generate volatile harmful gases, if the pyrite is not removed, the pore volume of the modified coal gangue will be small, the specific surface area will be small, and the adsorption performance will eventually decrease.

[0026] After removing the pyrite, the present invention further removes impurities from the coal gangue using hydrochloric acid, and removes metals such as iron, calcium, zinc, and nickel in the coal gangue using the acidity of the hydrochloric acid, so that more pores are formed inside the coal gangue and the specific surface area of ​​the coal gangue is further increased.

[0027] The one-time modification of the present invention utilizes calcination to expand the structure of the coal gangue, increase the microporous structure of the coal gangue, and make the structure of the coal gangue loose, thereby improving the adsorption performance of the coal gangue.

[0028] The secondary modification of the present invention utilizes a mixed acid of sulfuric acid + acetic acid for reflux modification, wherein sulfuric acid is a non-volatile oxygen-containing acid and acetic acid is a volatile oxygen-containing acid, and the gaseous acid and liquid acid act together to efficiently etch the surface of the gangue to form micropores. Moreover, the acids used in the present invention are all oxygen-containing acids, and the gaseous oxygen-containing acid and liquid oxygen-containing acid act together to more efficiently introduce oxygen-containing functional groups on the surface of the gangue.

[0029] The invention also sprays a small amount of chitosan solution on the surface of the coal gangue after two modifications. The introduction of chitosan can not only solidify the powdered coal gangue to a certain extent, but also further improve the adsorption performance of the coal gangue because chitosan has a large number of hydroxyl groups and amino groups.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The modified coal gangue obtained by the invention has a good removal effect on metals in industrial wastewater, and its removal rate for copper can reach 98.95%, the removal rate for zinc can reach 98.05%, the removal rate for chromium can reach 99.98%, the removal rate for cadmium can reach 99.98%, the removal rate for lead can reach 99.94%, and the removal rate for mercury can reach 99.99%. DETAILED DESCRIPTION

[0032] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0033] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] 1. Preprocessing:

[0039] 1) 100 g of coal gangue and 30 g of sodium carbonate were mixed evenly, and the mixture was ground and passed through a 20-mesh sieve to obtain a coal gangue-sodium carbonate mixture;

[0040] 2) calcining the gangue-sodium carbonate mixture obtained in step 1) at 100° C. for 30 min, during which the water content of the gangue-sodium carbonate mixture is controlled to be 20%;

[0041] 3) mixing the gangue-sodium carbonate mixture calcined at low temperature in step 2) with 500 mL of 4 mol / L hydrochloric acid, stirring, filtering the solid precipitate, washing with water until the pH value of the washing liquid is 7, drying at 70° C. for 10 min, grinding through a 20-mesh sieve, and obtaining pretreated gangue powder;

[0042] 2. One-time modification:

[0043] In a nitrogen atmosphere, the pretreated gangue powder obtained in step 1 is calcined at 700° C. for 20 min to obtain a primary modified gangue;

[0044] 3. Secondary modification:

[0045] 1) Take 30 mL of 3 mol / L sulfuric acid solution and 50 mL of 6 mol / L acetic acid solution, mix them evenly to obtain a mixed acid modified solution;

[0046] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), refluxing the mixed acid for modification at 100° C. for 1 hour, and then drying at 70° C. for 10 minutes to obtain secondary modified coal gangue;

[0047] 4. Curing:

[0048] 1) dissolving 2 mg of chitosan in 10 mL of 0.2 mol / L acetic acid solution to obtain a chitosan solution;

[0049] 2) The chitosan solution prepared in step 1) is uniformly sprayed on the surface of the secondary modified coal gangue prepared in step 3 by using a sprayer, and calcined at 300° C. for 10 min to obtain modified coal gangue.

[0050] Example 2

[0051] 1. Preprocessing:

[0052] 1) 100 g of coal gangue and 35 g of sodium carbonate were mixed evenly, and the mixture was ground and passed through a 20-mesh sieve to obtain a coal gangue-sodium carbonate mixture;

[0053] 2) calcining the gangue-sodium carbonate mixture obtained in step 1) at 120° C. for 35 min, during which the water content of the gangue-sodium carbonate mixture is controlled to be 25%;

[0054] 3) mixing the gangue-sodium carbonate mixture calcined at low temperature in step 2) with 700 mL of 4 mol / L hydrochloric acid, stirring, filtering the solid precipitate, washing with water until the pH value of the washing liquid is 7, drying at 70° C. for 10 min, grinding through a 20-mesh sieve, and obtaining pretreated gangue powder;

[0055] 2. One-time modification:

[0056] In a nitrogen atmosphere, the pretreated gangue powder obtained in step 1 is calcined at 850° C. for 30 min to obtain a primary modified gangue;

[0057] 3. Secondary modification:

[0058] 1) Take 30 mL of 3 mol / L sulfuric acid solution and 50 mL of 6 mol / L acetic acid solution, mix them evenly to obtain a mixed acid modified solution;

[0059] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), performing mixed acid reflux modification at 115° C. for 1.5 h, and then drying at 70° C. for 10 min to obtain secondary modified coal gangue;

[0060] 4. Curing:

[0061] 1) dissolving 2 mg of chitosan in 10 mL of 0.2 mol / L acetic acid solution to obtain a chitosan solution;

[0062] 2) The chitosan solution prepared in step 1) is uniformly sprayed on the surface of the secondary modified coal gangue prepared in step 3 by using a sprayer, and calcined at 400° C. for 15 minutes to obtain modified coal gangue.

[0063] Example 3

[0064] 1. Preprocessing:

[0065] 1) 100 g of coal gangue and 40 g of sodium carbonate were mixed evenly, and the mixture was ground and passed through a 20-mesh sieve to obtain a coal gangue-sodium carbonate mixture;

[0066] 2) calcining the gangue-sodium carbonate mixture obtained in step 1) at 140° C. for 40 min, during which the water content of the gangue-sodium carbonate mixture is controlled to be 30%;

[0067] 3) mixing the gangue-sodium carbonate mixture calcined at low temperature in step 2) with 1000 mL of 4 mol / L hydrochloric acid, stirring, filtering the solid precipitate, washing with water until the pH value of the washing liquid is 7, drying at 70° C. for 10 min, grinding through a 20-mesh sieve, and obtaining pretreated gangue powder;

[0068] 2. One-time modification:

[0069] In a nitrogen atmosphere, the pretreated gangue powder obtained in step 1 is calcined at 1000° C. for 50 min to obtain a primary modified gangue;

[0070] 3. Secondary modification:

[0071] 1) Take 30 mL of 3 mol / L sulfuric acid solution and 50 mL of 6 mol / L acetic acid solution, mix them evenly to obtain a mixed acid modified solution;

[0072] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), reflux modification with mixed acid at 130° C. for 2 h, and then drying at 70° C. for 10 min to obtain secondary modified coal gangue;

[0073] 4. Curing:

[0074] 1) dissolving 2 mg of chitosan in 10 mL of 0.2 mol / L acetic acid solution to obtain a chitosan solution;

[0075] 2) The chitosan solution prepared in step 1) is uniformly sprayed on the surface of the secondary modified coal gangue prepared in step 3 by using a sprayer, and calcined at 500° C. for 20 min to obtain modified coal gangue.

[0076] Comparative Example 1

[0077] Same as Example 2, except that the pretreatment in step 1 is:

[0078] 1) Grind 100g of coal gangue and pass it through a 20-mesh sieve;

[0079] 2) The coal gangue ground in step 1) was mixed with 700 mL of 4 mol / L hydrochloric acid, and the solid precipitate was filtered after stirring and washed with water until the pH of the washing liquid was 7, dried at 70° C. for 10 min, and ground through a 20-mesh sieve to obtain pretreated coal gangue powder.

[0080] Comparative Example 2

[0081] Same as Example 2, except that the pretreatment in step 1 is:

[0082] 1) 100 g of coal gangue and 35 g of sodium carbonate were mixed evenly, and the mixture was ground and passed through a 20-mesh sieve to obtain a coal gangue-sodium carbonate mixture;

[0083] 2) calcining the gangue-sodium carbonate mixture obtained in step 1) at 120° C. for 35 min, during which the water content of the gangue-sodium carbonate mixture is controlled to be 25%;

[0084] 3) The coal gangue-sodium carbonate mixture calcined at low temperature in step 2) is washed with water until the pH value of the washing liquid is 7, dried at 70° C. for 10 min, and ground through a 20-mesh sieve to obtain pretreated coal gangue powder.

[0085] Comparative Example 3

[0086] Same as Example 2, except that the modification of step 2 is omitted.

[0087] Comparative Example 4

[0088] Same as Example 2, except that the secondary modification in step 3 is:

[0089] 1) Take 30 mL of 3 mol / L sulfuric acid solution and 50 mL of 6 mol / L hydrochloric acid solution, mix them evenly to obtain a mixed acid modified solution;

[0090] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), performing mixed acid reflux modification at 115° C. for 1.5 h, and then drying at 70° C. for 10 min to obtain secondary modified coal gangue.

[0091] Comparative Example 5

[0092] Same as Example 2, except that the secondary modification in step 3 is:

[0093] 1) Take 30 mL of 3 mol / L sulfuric acid solution and 50 mL of 6 mol / L phosphoric acid solution, mix them evenly to obtain a mixed acid modified solution;

[0094] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), performing mixed acid reflux modification at 115° C. for 1.5 h, and then drying at 70° C. for 10 min to obtain secondary modified coal gangue.

[0095] Comparative Example 6

[0096] Same as Example 2, except that the secondary modification in step 3 is:

[0097] 1) Take 30 mL of 3 mol / L nitric acid solution and 50 mL of 6 mol / L acetic acid solution, mix them evenly to obtain a mixed acid modified solution;

[0098] 2) adding the primary modified coal gangue obtained in step 2 to the mixed acid modification solution obtained in step 1), performing mixed acid reflux modification at 115° C. for 1.5 h, and then drying at 70° C. for 10 min to obtain secondary modified coal gangue.

[0099] Comparative Example 7

[0100] Same as Example 2, except that step 4, curing, is omitted.

[0101] Effect verification:

[0102] Under laboratory conditions, simulated industrial wastewater was prepared, in which the copper content was 20 mg / L, the zinc content was 20 mg / L, the chromium content was 10 mg / L, the cadmium content was 5 mg / L, the lead content was 5 mg / L, and the mercury content was 5 mg / L.

[0103] According to the addition standard of 1g of modified coal gangue per 10mL of simulated industrial wastewater, the modified coal gangue prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were added to 10 groups of simulated industrial wastewater. After adsorption for 30 minutes, the total amount of each metal ion in the simulated industrial wastewater was measured. The test was repeated three times. The results are shown in Table 1.

[0104] Table 1 Determination of total metal ion content in simulated industrial wastewater

[0105]

[0106] It can be seen from the data in the above table that the modified coal gangue prepared by the present invention is used to treat simulated industrial wastewater, and the treated industrial wastewater can meet the functional standards of Class IV water areas in GB 3838-2002 "Surface Water Environmental Quality Standards".

[0107] The above description is only a preferred specific implementation manner of the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, and they should be covered by the protection scope of the present invention.

Claims

1. An application of modified coal gangue in adsorbing heavy metals in water, characterized in that: The heavy metals include one or more of copper, zinc, chromium, cadmium, lead and mercury; The modified coal gangue is obtained by treating coal gangue; The method for treating coal gangue comprises the following steps: 1) Pretreatment: Mixing coal gangue with sodium carbonate to obtain a coal gangue-sodium carbonate mixture, and subjecting the coal gangue-sodium carbonate mixture to low-temperature calcination and hydrochloric acid impurity removal to obtain pretreated coal gangue; 2) primary modification: calcining the pretreated gangue obtained in step 1) at high temperature to obtain primary modified gangue; 3) Secondary modification: the primary modified coal gangue obtained in step 2) is subjected to mixed acid modification in a mixed acid modification solution to obtain secondary modified coal gangue; 4) solidification: spraying the chitosan solution onto the surface of the secondary modified coal gangue prepared in step 3), and calcining to obtain modified coal gangue; In step 1), the mass ratio of the coal gangue to the sodium carbonate is 10:(3-4); In step 1), the low-temperature calcination is to control the water content of the gangue-sodium carbonate mixture to 20% to 30%, and calcine at 100 to 140° C. for 30 to 40 minutes; In step 1), the hydrochloric acid impurity removal is to mix the low-temperature calcined coal gangue-sodium carbonate mixture with hydrochloric acid, and wash the precipitate with water; The concentration of the hydrochloric acid is 4 mol / L, and the mass volume ratio of hydrochloric acid to coal gangue is 1 g: 5-10 mL; the water washing is to wash with water until the pH of the water washing liquid is 7; Step 2) is carried out in a nitrogen protective atmosphere; in step 2), the high temperature calcination is calcined at 700-1000° C. for 20-50 min; In step 3), the mixed acid modification solution is a mixture of 3 mol / L sulfuric acid solution and 6 mol / L acetic acid solution in a volume ratio of 3:5; the mixed acid modification is a mixed acid reflux modification at 100-130° C. for 1-2 hours; In step 4), the chitosan solution is prepared by dissolving chitosan in a 0.2 mol / L acetic acid solution at a material-liquid ratio of 1 mg:5 mL; and the calcination is carried out at 300-500° C. for 10-20 min.

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