An adsorption material for treating thallium-containing wastewater and a preparation method thereof

Abstract

The present invention discloses an adsorption material for treating thallium-containing wastewater and a preparation method thereof. The material comprises the following components by weight: 1-2 parts of coal gangue powder, 2-4 parts of NaOH, 1-4 parts of KMnO4, and 1.5-6 parts of MnCl2. The preparation method includes the following steps: preparing NaX zeolite, preparing nano-manganese dioxide, and preparing the adsorption material. The present invention utilizes a NaOH alkali fusion hydrothermal synthesis method to prepare the NaX zeolite from coal gangue, and then loads the nano-manganese dioxide onto the zeolite. The adsorption capacity of the zeolite and the adsorption and oxidation properties of the nano-manganese dioxide enable the resulting adsorption material to efficiently adsorb thallium from wastewater, achieving excellent water purification effects. The adsorption material can be used to treat thallium-containing wastewater and can also increase the utilization value of coal gangue, achieving the goal of "treating waste with waste."

Description

Technical Field

[0001] The invention relates to the fields of tailings resource utilization and wastewater adsorption material preparation, and in particular to an adsorption material for treating thallium-containing wastewater and a preparation method thereof. Background Art

[0002] Thallium is a highly toxic trace heavy metal element and is considered one of the most toxic metal ions to human health, far exceeding the toxicity of copper, lead, and zinc. Thallium is primarily discharged into the environment through wastewater generated during the mining, beneficiation, and smelting of titanium-containing sulfide ores. In aquatic environments, thallium exists in two oxidation states: monovalent thallium and trivalent thallium. Most thallium present in wastewater is monovalent thallium, and monovalent thallium is more difficult to treat. Adsorption is a common treatment method, and adsorption materials such as activated carbon and diatomaceous earth are commonly used to treat thallium-containing wastewater. However, these adsorption materials do not have a good adsorption effect on thallium. Therefore, the selection of economical and efficient adsorption materials is particularly important.

[0003] Gangue contains small amounts of coal and can burn in dry weather, posing a fire hazard. During periods of strong winds or heavy rain, gangue components can leach into water or form particulate matter, posing a health hazard. Because gangue's primary components are silicon oxide and aluminum oxide, it can be used to produce a variety of high-value-added products, such as zeolites. Zeolites are porous materials with uniform pores, large surface area, and excellent ion exchange capacity. However, due to their small pore size, single zeolite materials have low adsorption efficiency, making it difficult to ensure that thallium-containing wastewater can reach industrial disposal. Manganese dioxide, on the other hand, is considered an economical and readily available adsorbent and oxidant, offering higher adsorption capacity and selectivity than many other adsorbents. However, nano-manganese dioxide readily aggregates in aqueous solutions, losing its adsorption capacity and requiring loading onto other materials for efficient thallium removal from wastewater. Therefore, there is an urgent need to develop a highly efficient adsorbent material for treating thallium-containing wastewater that can simultaneously increase the utilization value of gangue and achieve the goal of "waste treatment with waste."

[0004] Therefore, in order to solve the above problems, this paper proposes an adsorption material for treating thallium-containing wastewater and a preparation method thereof. Summary of the Invention

[0005] The purpose of the present invention is to provide an adsorption material which adopts the NaOH alkaline fusion hydrothermal synthesis method to prepare NaX type zeolite from coal gangue, and then loads nano manganese dioxide on it, so that the final composite material can effectively adsorb thallium in wastewater and achieve good water purification effect.

[0006] In order to achieve the above-mentioned purpose, the present invention is realized through the following technical scheme: an adsorption material for treating thallium-containing wastewater, characterized in that the adsorption material includes the following components in parts by weight: 1 to 2 parts of coal gangue powder, 2 to 4 parts of NaOH, 1 to 4 parts of KMnO4, and 1.5 to 6 parts of MnCl2.

[0007] Another object of the present invention is to provide a method for preparing an adsorbent material for treating thallium-containing wastewater, characterized in that it comprises the following steps:

[0008] S1. Preparation of NaX zeolite: Coal gangue is crushed and calcined in a muffle furnace to remove impurities. The treated coal gangue powder is mixed with NaOH and ground uniformly, then placed in a crucible for calcination. The mixture is cooled to room temperature, mixed with distilled water, and stirred and aged at room temperature. The mixture is then transferred to a 100-200 mL reactor for reaction. After cooling to room temperature, the mixture is centrifuged and filtered, and then washed with distilled water. Finally, the synthesized product is dried to obtain NaX zeolite for later use.

[0009] S2. Preparation of nano-manganese dioxide: under magnetic stirring, KMnO4 solution is dropped into MnCl2 solution to obtain nano-manganese dioxide stock solution with microporous structure;

[0010] S3. Preparation of adsorption material: NaX zeolite was placed in a stoppered glass bottle, and nano manganese dioxide stock solution was added. The mixture was shaken in a water bath for 16 to 20 hours. After cooling to room temperature, the mixture was centrifuged and dehydrated. The dehydrated solid was granulated by extrusion and finally dried to obtain the adsorption material.

[0011] Furthermore, in S1, the coal gangue is crushed specifically by grinding the coal gangue into particles with a particle size not greater than 0.4 mm using a ball mill at a rotation speed of 300 to 500 r / min, and then passing the particles through a 40 to 60 mesh sieve.

[0012] Furthermore, in S1, the reactor is a polyethylene reactor.

[0013] Furthermore, in S1, the calcination conditions in the muffle furnace are: temperature of 750° C. to 850° C., and calcination time of 1.5 to 2 hours.

[0014] Furthermore, in S1, the specific operation of mixing the treated coal gangue powder with NaOH and grinding them evenly and then placing them in a crucible for calcination is: mixing the treated coal gangue and NaOH in a mass ratio of 1-2:2-4, grinding them evenly and placing them in a crucible, calcining them at 500-600°C for 1-2h, cooling to room temperature, adding and mixing with distilled water in a mass ratio of 1:10-15, stirring and aging at room temperature for 6-10h, and then transferring them to a reactor.

[0015] Furthermore, in S2, the specific operation of dripping the KMnO4 solution into the MnCl2 solution is: mixing KMnO4 and MnCl2 in a mass ratio of 1 to 4:1.5 to 6, taking 100 mL of the KMnO4 solution with a concentration of 2 mmol / L and dripping it into 100 mL of the MnCl2 solution with a concentration of 3 mmol / L at a rate of 5 mL / min.

[0016] Furthermore, in S3, the step of placing the NaX zeolite in a stoppered glass bottle and adding the nano-manganese dioxide stock solution is as follows: mixing the NaX zeolite and the nano-manganese dioxide stock solution in a mass ratio of 1-3:30-60 and then placing the mixture in the stoppered glass bottle.

[0017] Furthermore, in S3, the water bath oscillation condition is: oscillation at 150-250 r / min at 55-75°C.

[0018] Furthermore, in S3, the solid particles are granulated into spherical particles, and the drying conditions are: drying at 100-140° C. for 1.5-2.5 hours.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention uses solid waste coal gangue as raw material, which not only reduces the waste of resources, but also alleviates environmental problems such as water pollution. It also allows the conversion and utilization of coal gangue to not only be limited to low-value areas such as mine backfill and roadbed landfill. While bringing higher economic value, it also responds to the national environmental protection concept of "solid waste recycling and reuse";

[0021] (2) Nano-manganese dioxide has a large specific surface area, suitable pore structure and surface structure, but because it is easy to agglomerate, this limits its application as an adsorbent. Therefore, loading nano-manganese dioxide onto the surface of zeolite to form a composite material can solve the defect that nano-manganese dioxide is easy to agglomerate. After loading nano-manganese dioxide onto the surface of zeolite, due to its rich surface hydroxyl groups, polymorphic structure and high specific surface area, it has strong adsorption advantages and oxidation characteristics, which improves the removal efficiency of thallium;

[0022] (3) The adsorbent material can reduce the thallium concentration in thallium-containing wastewater to approximately 2 μg / L, ensuring that the thallium-containing wastewater meets industrial emission standards. Furthermore, the adsorbent material of the present invention has the advantages of a wide range of applications and high efficiency in removing thallium by combining adsorption and oxidation. The preparation method of the adsorbent material of the present invention also has the advantages of simplified steps and convenient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is the overall preparation flow chart of the present invention; DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0026] Example 1

[0027] An adsorption material for treating thallium-containing wastewater is characterized in that the adsorption material comprises the following components in parts by weight: 1 part of coal gangue powder, 2 parts of NaOH, 2 parts of KMnO4, and 3 parts of MnCl2.

[0028] A specific preparation method of an adsorption material for treating thallium-containing wastewater comprises the following steps:

[0029] S1. Preparation of NaX zeolite: The selected coal gangue was ground into particles with a particle size of no more than 0.4 mm by a ball mill at a speed of 400 r / min, then passed through a 50-mesh sieve and calcined in a muffle furnace at 750°C for 1.5 h to remove impurities. The treated coal gangue powder was mixed with NaOH at a mass ratio of 1:2, uniformly ground, and then calcined in a crucible at 550°C for 1.5 h. The mixture was cooled to room temperature, and distilled water was added at a mass ratio of 1:15 to mix. After stirring and aging at room temperature for 8 h, the mixture was transferred to a 100 mL polyethylene reactor for reaction. After cooling to room temperature, the mixture was centrifuged and filtered, and then washed with distilled water. Finally, the synthesized product was dried to obtain NaX zeolite for use.

[0030] S2. Preparation of nano-manganese dioxide: Under magnetic stirring, KMnO4 solution (2 mmol / L, 100 mL) was added dropwise to MnCl2 solution (3 mmol / L, 100 mL) at a rate of 5 mL / min to obtain a MnO2 stock solution containing nano-manganese dioxide with a microporous structure;

[0031] S3. Preparation of adsorption material: 5 g of NaX zeolite was placed in a 250 mL stoppered glass bottle, 150 mL of nano-manganese dioxide colloidal stock solution was added, and the mixture was shaken in a water bath at 65°C and 200 rpm for 18 h. After cooling to room temperature, the mixture was centrifuged and dehydrated. The dehydrated solid was formed into a round shape by extrusion, and finally dried at 120°C for 2 h to obtain the adsorption material.

[0032] In this Example 1, 20 mL of thallium-containing wastewater with a pH value of 7 and a thallium concentration of 4 mg / L was selected and placed in a centrifuge tube; 0.2 g of adsorption material was taken and placed in the centrifuge tube, the temperature of the thallium-containing wastewater was controlled at 25°C, and the thallium-containing wastewater was shaken on a shaker with a speed of 180 r / min. The reaction time was 1 h, and then 1 ml of the reacted thallium-containing wastewater was taken out to measure the thallium concentration. The results are shown in Table 1.

[0033] Example 2

[0034] The difference from Example 1 is that in S1, after passing through a 50-mesh sieve, the product was calcined in a muffle furnace at 800° C. for 1.2 h to remove impurities, that is, the temperature and time of calcination in the muffle furnace were changed, while other conditions remained unchanged. The specific preparation process is as follows:

[0035] S1. Preparation of NaX zeolite: The selected coal gangue was ground into particles with a particle size of no more than 0.4 mm by a ball mill at a speed of 400 r / min, then passed through a 50-mesh sieve and calcined in an 800°C muffle furnace for 1.2 h to remove impurities. The treated coal gangue powder was mixed with NaOH in a mass ratio of 1:2, uniformly ground, and then calcined in a crucible at 550°C for 1.5 h. The mixture was cooled to room temperature, and distilled water was added in a mass ratio of 1:15 to mix. After stirring and aging at room temperature for 8 h, the mixture was transferred to a 100 mL polyethylene reactor for reaction. After cooling to room temperature, the mixture was centrifuged and filtered, and then washed with distilled water. Finally, the synthesized product was dried to obtain NaX zeolite for use.

[0036] S2. Preparation of nano-manganese dioxide colloid: Under magnetic stirring, KMnO4 solution (2 mmol / L, 100 mL) was added dropwise to MnCl2 solution (3 mmol / L, 100 mL) at a rate of 5 mL / min to obtain a MnO2 stock solution containing nano-manganese dioxide with a microporous structure;

[0037] S3. Preparation of adsorption material: 5 g of NaX zeolite was placed in a 250 mL stoppered glass bottle, 150 mL of nano-manganese dioxide colloidal stock solution was added, and the mixture was shaken in a water bath at 65°C and 200 rpm for 18 h. After cooling to room temperature, the mixture was centrifuged and dehydrated. The dehydrated solid was formed into a round shape by extrusion, and finally dried at 120°C for 2 h to obtain the adsorption material.

[0038] In this Example 2, 20 mL of thallium-containing wastewater with a pH value of 7 and a thallium concentration of 4 mg / L was selected and placed in a centrifuge tube; 0.2 g of the adsorption material prepared in Example 2 was placed in the centrifuge tube, the temperature of the thallium-containing wastewater was controlled at 25° C., and the thallium-containing wastewater was shaken on a shaker with a speed of 180 r / min. The reaction time was 1 h, and then 1 ml of the reacted thallium-containing wastewater was taken out to measure the thallium concentration. The results are shown in Table 1.

[0039] Example 3

[0040] The difference from Example 1 is that in S1, the treated coal gangue powder and NaOH are mixed in a mass ratio of 1:1.5, that is, the mixing ratio of coal gangue powder and NaOH is changed, and other conditions remain unchanged.

[0041] Example 4

[0042] The difference from Example 1 is that in S1, the treated gangue powder is mixed and evenly ground with NaOH and then placed in a crucible at 600°C and calcined for 1.7h, that is, the calcination temperature and time are increased after the gangue powder is mixed and evenly ground with NaOH, and other conditions remain unchanged.

[0043] Example 5

[0044] The difference from Example 1 is that in S2, the KMnO4 solution and the MnCl2 solution are uniformly mixed in a mass ratio of 2:2.5, that is, the proportion of the MnCl2 solution is reduced, and other conditions remain unchanged.

[0045] Example 6

[0046] The difference from Example 1 is that in S3, NaX zeolite and nano-manganese dioxide stock solution are mixed at a mass ratio of 1-2:30-60 and then placed in a stoppered glass bottle, that is, the content of NaX zeolite is reduced, and other conditions remain unchanged.

[0047] Example 7

[0048] The difference from Example 1 is that in S3, the dehydrated solid is spherical particles, and is then dried at 100° C. for 1.8 h, that is, the drying temperature and drying time are reduced, and other conditions remain unchanged.

[0049] Example 8

[0050] The difference from Example 1 is that the reaction time is controlled to 20 min, and other conditions remain unchanged.

[0051] Example 9

[0052] The difference from Example 1 is that the reaction time is controlled to 10 min, and other conditions remain unchanged.

[0053] The adsorption materials obtained through the above 9 experiments were reacted in the same thallium-containing wastewater as follows: thallium-containing wastewater with a pH value of 7 and an initial concentration of 4 mg / L was prepared, 20 ml of thallium-containing wastewater was placed in 9 centrifuge tubes respectively, and then the adsorption materials prepared in the above Examples 1-9 were added respectively. The reaction was carried out by shaking on a shaker (shaking speed of 180 r / min, reaction time of 1 h), and then 1 ml of the reacted thallium-containing wastewater was taken out to measure the thallium concentration, and the thallium removal rate was calculated. The results are shown in Table 1.

[0054]

[0055]

[0056] Table 1

[0057] From Table 1 we can see that:

[0058] (1) The composite material prepared in Example 1 can treat the thallium concentration in the thallium-containing wastewater to about 2 μg / L under the conditions that the pH value of the thallium-containing wastewater is 7 and the thallium concentration in the thallium-containing wastewater is 4 mg / L, ensuring that the thallium-containing wastewater meets the industrial emission standards;

[0059] (2) As shown in Example 2, as the temperature of calcining coal gangue in the muffle furnace increases, most of the kaolinite in the coal gangue will be transformed into porous, disordered, and amorphous metakaolinite, which weakens its activity and reduces its adsorption performance; it is impossible to treat the thallium concentration in the thallium-containing wastewater to about 2 μg / L.

[0060] (3) As shown in Example 3, the proportion of NaOH is reduced, the alkali melting of coal gangue is not complete, which affects the subsequent zeolite activity and adsorption; the thallium concentration in the thallium-containing wastewater cannot be treated to about 2 μg / L.

[0061] (4) As can be seen from Example 4, the zeolite was calcined at a high temperature of 600°C in a crucible, which is much higher than the calcination temperature of 550°C in Example 1. This stage belongs to the high-temperature calcination activation stage of the zeolite. The excessively high temperature caused the destruction of the zeolite structure, which greatly reduced the mechanical strength and adsorption capacity of the zeolite. It was impossible to treat the thallium concentration in the thallium-containing wastewater to about 2 μg / L.

[0062] (5) As shown in Example 5, the proportion of MnCl2 is reduced and the KMnO4 reaction is incomplete, resulting in insufficient production of nano-manganese dioxide in the stock solution, and the inability to achieve the optimal adsorption and oxidation amounts; the thallium concentration in the thallium-containing wastewater cannot be treated to about 2 μg / L.

[0063] (6) As shown in Example 6, the amount of zeolite added in the final adsorption material preparation stage is reduced, so that the nano-manganese dioxide cannot be evenly loaded on the zeolite carrier in a small amount, resulting in a decrease in adsorption sites and a decrease in adsorption efficiency; the thallium concentration in the thallium-containing wastewater cannot be treated to about 2 μg / L.

[0064] (7) As can be seen from Example 7, the drying time and temperature of the adsorption material are reduced compared to Example 1, so the material is not firmly formed and easily dispersed in water, affecting the adsorption effect; it is impossible to treat the thallium concentration in the thallium-containing wastewater to about 2 μg / L.

[0065] (8) It can be seen from Examples 8 and 9 that using the same materials as in Example 1 but only controlling the reaction time does not have much effect on the thallium removal efficiency, but the thallium concentration in the thallium-containing wastewater cannot be treated to about 2 μg / L, which does not meet the industrial emission standards for thallium-containing wastewater.

[0066] Considering the comprehensive economic efficiency, adsorption efficiency and time cost, Example 1 is the most preferred adsorption material.

Claims

1. A method for preparing an adsorption material for treating thallium-containing wastewater, characterized in that: The following steps are involved: S1. Preparation of NaX zeolite: The selected coal gangue was ground into particles with a particle size of no greater than 0.4 mm in a ball mill at 400 r / min. The mixture was then passed through a 50-mesh sieve and calcined in a muffle furnace at 750°C for 1.5 h to remove impurities. The treated coal gangue powder was mixed with NaOH at a mass ratio of 1:2, uniformly ground, and calcined in a crucible at 550°C for 1.5 h. The mixture was cooled to room temperature, and distilled water was added at a mass ratio of 1:

15. The mixture was stirred and aged at room temperature for 8 h. The mixture was then transferred to a 100 mL polyethylene reactor for reaction. After cooling to room temperature, the mixture was centrifuged and filtered, and then washed with distilled water. Finally, the synthesized product was dried to obtain NaX zeolite for later use. S2. Preparation of nano-manganese dioxide: Under magnetic stirring, 100 mL of a 2 mmol / L KMnO4 solution was added dropwise to 100 mL of a 3 mmol / L MnCl2 solution at a rate of 5 mL / min to obtain a MnO2 stock solution containing nano-manganese dioxide having a microporous structure. S3. Preparation of adsorption material: 5 g of NaX zeolite was placed in a 250 mL stoppered glass bottle, 150 mL of nano-manganese dioxide colloidal stock solution was added, and the mixture was shaken in a water bath at 65°C and 200 rpm for 18 h. After cooling to room temperature, the mixture was centrifuged and dehydrated. The dehydrated solid was formed into a round shape by extrusion, and finally dried at 120°C for 2 h to obtain the adsorption material.

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