Copper tailing-based adsorbent, preparation method thereof and treatment method of arsenic and cadmium-containing heavy metal wastewater

Abstract

The invention provides a copper tailing-based adsorbent, a preparation method thereof and a treatment method of arsenic and cadmium-containing heavy metal wastewater, and relates to the field of solid waste treatment. Crushing and drying the copper tailings to obtain pretreated copper tailings; the pretreated tailings and nitric acid are subjected to first mixing and first reaction, and acid modified tailings are obtained; carrying out second mixing and second reaction on the acid modified tailings and sodium hydroxide to obtain alkali modified tailings; the alkali modified tailings and calcium hydroxide are subjected to third mixing and third reaction, and calcium-based reinforced tailings are obtained; and the calcium-based reinforced tailings are washed to be neutral and dried, and the copper tailing-based adsorbent is obtained. The solid waste copper tailings are used as raw materials, an ion exchange-chemical precipitation-multi-element complexing multi-stage synergistic adsorption system is constructed, the preparation process is easy to operate, low in cost and free of secondary pollution, the purpose of treating waste with waste of the copper tailings is achieved, the double benefits of solid waste recycling and heavy metal wastewater treatment are achieved, and the method is suitable for industrial production. And the method has a good engineering application prospect.

Description

Technical Field

[0001] This application relates to the field of solid waste treatment, and in particular to a copper tailings-based adsorbent, its preparation method, and a method for treating wastewater containing arsenic and cadmium heavy metals. Background Technology

[0002] Copper tailings accumulate year after year, not only occupying a large amount of space and posing significant safety hazards, but also easily polluting the air and soil, severely damaging the ecological environment, and even affecting biodiversity. Therefore, the secondary utilization of copper tailings resources is an important aspect of achieving resource recycling. In recent years, my country has made continuous progress in the comprehensive utilization of copper tailings resources, achieving some breakthrough research results, but progress remains slow.

[0003] On the other hand, the non-ferrous metals industry generates large amounts of wastewater containing heavy metals during production. This wastewater is characterized by its reluctance to degrade, long-term accumulation, toxicity, difficulty in metabolism, and concealment, posing a serious threat to the surrounding ecological environment and human health. Therefore, the treatment of heavy metal wastewater is a crucial issue that urgently needs to be addressed. Among these, arsenic (a typical acid radical) and cadmium (a cationic heavy metal) are considered highly toxic and difficult to treat, and both are classified as Group 1 carcinogens. Currently, adsorption is one of the commonly used technologies for treating heavy metal wastewater, attracting widespread attention due to its advantages of being green, rapid, simple, and inexpensive. The key to adsorption research lies in the preparation of adsorbents. Existing research indicates that copper tailings contain abundant silicon and some iron, making them potential raw materials for preparing arsenic and cadmium adsorbents; however, no relevant research reports have been published yet.

[0004] Therefore, under the guidance of the strategic thinking of ecological civilization construction, it is urgent to open up a new way for the comprehensive utilization of copper tailings, help solve the safety and environmental protection problems caused by the storage of copper tailings, and at the same time use the prepared adsorbents for the treatment of heavy metal wastewater to achieve "waste treatment with waste", improve resource utilization efficiency, alleviate resource shortage pressure, promote the green, low-carbon and sustainable development of the copper mining industry, and embark on the path of circular economy, which has important practical significance. Summary of the Invention

[0005] The purpose of this application is to provide a copper tailings-based adsorbent and its preparation method, as well as a method for treating arsenic and cadmium-containing heavy metal wastewater, in order to solve the dual problems of low comprehensive utilization rate of copper tailings and difficulty in simultaneous removal of arsenic and cadmium from water.

[0006] To achieve the above objectives, the first aspect of this application provides a method for preparing a copper tailings-based adsorbent, comprising: The copper tailings are crushed and dried to obtain pretreated copper tailings. The pretreated tailings and nitric acid are first mixed and first reacted to obtain acid-modified tailings; The acid-modified tailings and sodium hydroxide are mixed and reacted in a second way to obtain alkali-modified tailings. The alkali-modified tailings and calcium hydroxide are mixed and reacted in a third way to obtain calcium-based reinforced tailings. The calcium-based reinforced tailings were washed with water until neutral and then dried to obtain a copper tailings-based adsorbent.

[0007] Optionally, the copper tailings comprises silicate minerals and aluminosilicate minerals, and the chemical composition, by mass percentage, includes: SiO2 22.8%-69.3%, Al2O3 5.5%-20.1%, K2O 0.93%-4.87%, SO3 0.96%-27.8%, CaO 0.4%-31.8%, Na2O 0.67%-3.86%, Fe2O3 3.7%-36.4%, and MgO 0.5%-11.9%.

[0008] Optionally, the pretreated copper tailings have a particle size ≤200 mesh and a moisture content ≤5%.

[0009] Optionally, the first reaction takes 60-120 minutes and is carried out at room temperature. And / or, the concentration of the nitric acid is 1-3 mol / L, and the solid-liquid ratio of the copper tailings to the nitric acid is 1 g: 10 mL-30 mL.

[0010] Optionally, the second reaction takes 60-240 min and is carried out at a temperature of 25-100°C. And / or, the concentration of the sodium hydroxide is 1-5 mol / L, and the solid-liquid ratio of the copper tailings to the sodium hydroxide is 1 g: 10 mL-30 mL.

[0011] Optionally, the duration of the third reaction is 30-120 min; And / or, the mass ratio of the copper tailings to the calcium hydroxide is 10:0.5-2.5.

[0012] Optionally, the drying includes vacuum drying; the temperature of the vacuum drying is 60-80°C.

[0013] The second aspect of this application provides a copper tailings-based adsorbent, which is prepared by the method for preparing the copper tailings-based adsorbent.

[0014] The third aspect of this application provides a method for treating wastewater containing arsenic and cadmium heavy metals, using the copper tailings-based adsorbent for adsorption.

[0015] Optionally, the copper tailings-based adsorbent has an adsorption capacity of 7.86-60.82 mg / g for arsenic and 9.98-110.78 mg / g for cadmium.

[0016] Compared with the prior art, the beneficial effects of this application include: The method for preparing copper tailings-based adsorbent provided in this application uses industrial solid waste copper tailings as raw material and is prepared through simple acid-base composite modification. It constructs an ion exchange-chemical precipitation-multi-component complexation multi-level synergistic adsorption system. The preparation process is simple to operate, low in cost, and free from secondary pollution. It realizes the "waste treatment with waste" of copper tailings and has the dual benefits of solid waste resource utilization and heavy metal wastewater treatment, and has good engineering application prospects.

[0017] The copper tailings-based adsorbent provided in this application has excellent simultaneous adsorption performance for arsenic and cadmium.

[0018] The treatment method for arsenic and cadmium-containing heavy metal wastewater provided in this application simultaneously adsorbs arsenic and cadmium in the wastewater, resulting in good treatment effect. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 This is a physical image of the copper tailings-based adsorbent provided in Example 1. Detailed Implementation

[0021] First, the solution provided in this application will be explained in more detail as follows: The first aspect of this application provides a method for preparing a copper tailings-based adsorbent, comprising: The copper tailings are crushed and dried to obtain pretreated copper tailings. The pretreated tailings and nitric acid are first mixed and first reacted to obtain acid-modified tailings; It should be noted that acid modification can increase the specific surface area and porosity of copper tailings by dissolving some mineral components in the tailings. The acid-modified tailings and sodium hydroxide are mixed and reacted in a second way to obtain alkali-modified tailings. It should be noted that alkali modification can break the Si-O bonds of silicates in copper tailings, dissociating them into silicate ions that enter the solution. The specific chemical formula is shown below. 2NaOH + SiO2 → Na2SiO3 + H2O; The alkali-modified tailings and calcium hydroxide are mixed and reacted in a third way to obtain calcium-based reinforced tailings. It should be noted that calcium hydroxide can provide sufficient Ca. 2+ It reacts with Na2SiO3 to form CSH gel; 6Na2SiO3+ 5Ca(OH)2+ 6H2O → Ca5Si6O 16 (OH)₂·4H₂O + 12NaOH; After acid-base composite modification, the porosity and specific surface area of ​​calcium-based enhanced tailings are significantly improved, exposing more silicon-based and calcium-based active sites, providing a basis for the adsorption of arsenic and cadmium. The calcium-based reinforced tailings were washed with water until neutral and then dried to obtain a copper tailings-based adsorbent.

[0022] It is also important to note that the first reaction, acid modification to increase the specific surface area and porosity of copper tailings, helps promote the uniform penetration of sodium hydroxide solution into the particle interior, rather than just remaining on the surface. This enhances the efficiency of the second reaction, alkaline modification, allowing more silicate ions to enter the solution and providing more active silicon sources for the third reaction. This further generates more CSH gels with extremely high specific surface areas and abundant surface hydroxyl groups (Si-OH, Ca-OH), providing active reaction sites for adsorbing arsenic and cadmium in wastewater, thus transforming "inert copper tailings" into "highly efficient adsorption materials." The "nitric acid-sodium hydroxide-calcium hydroxide" modification process set up in this application is progressively advanced; any misstep in any step will disrupt the reaction chain, leading to a decrease in specific surface area or failure to form active sites.

[0023] In some embodiments, the copper tailings comprises silicate minerals and aluminosilicate minerals, and the chemical composition, by mass percentage, includes: SiO2 22.8%-69.3%, Al2O3 5.5%-20.1%, K2O 0.93%-4.87%, SO3 0.96%-27.8%, CaO 0.4%-31.8%, Na2O 0.67%-3.86%, Fe2O3 3.7%-36.4%, and MgO 0.5%-11.9%.

[0024] Optionally, the chemical composition of the copper tailings, by mass percentage, includes: SiO2, which can be any value between 22.8%, 25%, 30%, 40%, 50%, 60%, 69.3%, or 22.8%-69.3%; Al2O3, which can be any value between 5.5%, 10%, 15%, 20.1%, or 5.5-20.1%; K2O, which can be any value between 0.93%, 1%, 2%, 3%, 4%, 4.87%, or 0.93-4.87%; and SO3, which can be 0.96%, 1%, 5%, 10%, 15%, 20%, 27.8%, or 0.96%. The following values ​​are allowed: CaO (0.4%, 1%, 5%, 10%, 15%, 20%, 30%, 31.8%, or 0.4%-31.8%), Na2O (0.67%, 1%, 2%, 3%, 3.86%, or 0.67%-3.86%), Fe2O3 (3.7%, 5%, 10%, 20%, 30%, 36.4%, or 3.7%-36.4%), and MgO (0.5%, 1%, 5%, 10%, 11.9%, or 0.5%-11.9%).

[0025] It should be noted that the heavy metal leaching concentrations in copper tailings are all below the Class III surface water standard, posing no environmental risk.

[0026] In some embodiments, the pretreated copper tailings have a particle size ≤200 mesh and a moisture content ≤5%.

[0027] Optionally, the particle size of the pretreated copper tailings can be any value of 270 mesh, 325 mesh, 400 mesh or ≤200 mesh, and the moisture content can be any value of 5%, 4%, 3%, 2%, 1% or ≤5%.

[0028] In some embodiments, the first reaction time is 60-120 min and the temperature is room temperature; Optionally, the time for the first reaction can be any value between 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, or 60-120 min; And / or, the concentration of the nitric acid is 1-3 mol / L, and the solid-liquid ratio of the copper tailings to the nitric acid is 1 g: 10 mL-30 mL.

[0029] Optionally, the concentration of nitric acid can be any value between 1 mol / L, 2 mol / L, 3 mol / L or 1-3 mol / L, and the solid-liquid ratio of copper tailings to nitric acid can be any value between 1g:10mL, 1g:20mL, 1g:30mL or 1g:1mL-10mL.

[0030] In some embodiments, the second reaction takes 60-240 min and is carried out at a temperature of 25-100°C. Optionally, the time of the second reaction can be any value between 60 min, 90 min, 120, 240 min or 60-240 min, and the temperature can be any value between 25℃, 35℃, 45℃, 55℃, 65℃, 75℃, 85℃, 95℃ or 25-100℃. And / or, the concentration of the sodium hydroxide is 1-5 mol / L, and the solid-liquid ratio of the copper tailings to the sodium hydroxide is 1 g: 10 mL-30 mL.

[0031] Optionally, the concentration of sodium hydroxide can be any value between 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 1-5 mol / L, and the solid-liquid ratio of copper tailings to sodium hydroxide can be any value between 1g:10mL, 1g:20mL, 1g:30mL or 1g:10mL-30mL.

[0032] In some embodiments, the third reaction takes 30-120 minutes; Optionally, the time for the third reaction can be any value between 30 min, 60 min, 90 min, 120 min, or 30-120 min; And / or, the mass ratio of the copper tailings to the calcium hydroxide is 10:0.5-2.5.

[0033] Optionally, the mass ratio of copper tailings to calcium hydroxide can be any value between 10:0.5, 10:1, 10:1.5, 10:2, 10:2.5 or 10:0.5-2.5.

[0034] In some embodiments, the drying includes vacuum drying; the temperature of the vacuum drying is 60-80°C.

[0035] Alternatively, the vacuum drying temperature can be any value between 60°C, 70°C, 80°C, or 60-80°C.

[0036] The second aspect of this application provides a copper tailings-based adsorbent, which is prepared by the method for preparing the copper tailings-based adsorbent.

[0037] The third aspect of this application provides a method for treating wastewater containing arsenic and cadmium heavy metals, using the copper tailings-based adsorbent for adsorption.

[0038] It should be noted that arsenic in wastewater mainly exists as arsenite (AsO3). 3-As(III) and arsenate (AsO4) 3- Cadmium exists primarily as cations (Cd, As(V)). 2+ The presence of both arsenic and cadmium in wastewater presents challenges due to the different potentials and active sites required for their removal. The copper tailings-based adsorbent described in this application, through gradient modification, generates a multifunctional composite structure with CSH gel as its core on the tailings surface. This structure possesses active sites for hydroxyl, silicate, and calcium ions, enabling the simultaneous removal of arsenic and cadmium from wastewater through ion exchange-chemical precipitation and complexation reactions. This provides a feasible one-step deep purification solution for complex heavy metal wastewater.

[0039] In some embodiments, the copper tailings-based adsorbent has an adsorption capacity of 7.86-60.82 mg / g for arsenic and 9.98-110.78 mg / g for cadmium.

[0040] Optionally, the adsorption capacity of arsenic can be any value of 7.86 mg / g, 10.98 mg / g, 30 mg / g, 50 mg / g or 7.86-60.82 mg / g, and the adsorption capacity of cadmium can be any value of 9.98 mg / g, 40 mg / g, 80 mg / g, 100 mg / g or 9.98-110.78 mg / g.

[0041] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0042] Example 1 The first aspect of this embodiment provides a copper tailings-based adsorbent and its preparation method. The copper tailings consist of silicate minerals and aluminosilicate minerals, and their chemical composition, by mass percentage, includes: SiO2 63.29%, Al2O3 15.95%, K2O 4.43%, SO3 4.24%, CaO 3.23%, Na2O 2.96%, Fe2O3 3.85%, and MgO 1.49%. The specific preparation steps are as follows: S1: Using 10 g of the above copper tailings as raw material, crushing and drying are carried out to obtain pretreated copper tailings. The particle size of the pretreated copper tailings is ≤200 mesh and the moisture content is ≤5%. S2: At room temperature, the pretreated tailings and 200 mL of 2 mol / L nitric acid are mixed, wherein the solid-liquid ratio of copper tailings and nitric acid is 1 g: 20 mL, and the reaction is carried out for 120 min to obtain acid-modified tailings. S3: Mix acid-modified tailings with 300 mL of 2 mol / L sodium hydroxide, wherein the solid-liquid ratio of copper tailings to sodium hydroxide is 1 g: 30 mL, react for 240 min at 100 °C to obtain alkali-modified tailings. S4: Mix alkali-modified tailings with 1g of calcium hydroxide, with a mass ratio of copper tailings to calcium hydroxide of 10:1, and react for 60min to obtain calcium-based reinforced tailings; S5: Wash the calcium-based enhanced tailings with water until neutral and dry to obtain a copper tailings-based adsorbent.

[0043] A photograph of the actual copper tailings-based adsorbent is shown below. Figure 1 As shown.

[0044] Example 2 The difference from Example 1 is that in step S2, the solid-liquid ratio of copper tailings and nitric acid is 1g:20mL, and the reaction time is 60min.

[0045] Comparative Example 1 The difference from Example 1 is that the copper tailings are not processed and are used directly.

[0046] Comparative Example 2 The difference from Example 1 is that only steps S1 and S2 are performed, that is, only single nitric acid modification is performed.

[0047] Comparative Example 3 The difference from Example 1 is that only steps S1, S2 and S3 are performed, that is, only the binary modification of nitric acid and sodium hydroxide is performed.

[0048] Comparative Example 4 The difference from Example 1 is that the order of S2 and S3 is changed, with sodium hydroxide modification performed first, followed by nitric acid modification.

[0049] The copper tailings-based adsorbents provided in the above embodiments and comparative examples were subjected to adsorption tests for arsenic and cadmium, respectively. The specific methods are as follows: The laboratory was prepared to simulate arsenic and cadmium co-polluted wastewater with a pH of 6.5, an initial As concentration of 50 mg / L and a Cd concentration of 50 mg / L. Copper tailings-based adsorbents provided in the above examples and comparative examples were added respectively, with an adsorption time of 24 h and a solid-liquid ratio of 1 g / L.

[0050] The adsorption results of the copper tailings-based adsorbents provided in the above examples and comparative examples on arsenic and cadmium were tested, and the specific results are shown in Table 1.

[0051] Table 1. Adsorption capacity (mg / g) test of copper tailings-based adsorbent

[0052] analyze: As shown in Table 1, the adsorption capacities of the copper tailings-based adsorbents described in Examples 1-2 for arsenic and cadmium are significantly higher than those of the comparative examples. The copper tailings-based adsorbent described in Example 1 exhibits the best performance, with an adsorption capacity of 10.98 mg / g for arsenic and 49.90 mg / g for cadmium. Among the comparative examples, Comparative Examples 1, 2, and 4 show lower adsorption capacities, with relatively low adsorption capacities for both arsenic and cadmium. Comparative Example 3 shows slightly better adsorption performance than the other comparative examples, but it is still far lower than that of Example 1. Overall, this demonstrates that the copper tailings-based adsorbent prepared using the process of this invention can significantly improve the adsorption capacity for arsenic and cadmium.

[0053] The copper tailings-based adsorbents described in Examples 1-2, through gradient modification, generate a multifunctional composite structure with CSH gel as the core in situ on the tailings surface. This structure possesses active sites for hydroxyl, silicate, and calcium ions, enabling the simultaneous removal of arsenic and cadmium from wastewater through ion exchange-chemical precipitation and complexation reactions. In Comparative Example 1, the copper tailings consist of five stable mineral phases with very few active reaction sites, making them unable to react effectively with arsenic and cadmium. The adsorbent in Comparative Example 2, modified only with nitric acid, while increasing the specific surface area and porosity, still suffers from a lack of active reaction sites, similarly unable to react effectively with arsenic and cadmium. The adsorbent in Comparative Example 3, modified only with nitric acid and sodium hydroxide, achieves increased specific surface area and activated silicate ions, providing an "active silicon source." Through a certain degree of ion exchange, chemical precipitation, and surface complexation... While achieving the adsorption and removal of arsenic and cadmium, it lacks calcium ion active sites. Therefore, the adsorption capacity for arsenic is lower than that in Examples 1-2, and the adsorption capacity for cadmium is also lower than that in Examples 1 and 2. The adsorbent in Comparative Example 4 was prepared by first modifying it with sodium hydroxide and then with nitric acid. The sodium silicate dissolved by alkali will immediately be converted into neutral silicic acid when acid is added later, and will rapidly polymerize into amorphous silica gel, blocking the pores and resulting in a lower specific surface area of ​​the final product. Therefore, the adsorption capacity for arsenic and cadmium is also lower than that of the copper tailings-based adsorbent described in Examples 1-2.

[0054] The copper tailings-based adsorbent provided in this application has excellent treatment effect on actual arsenic and cadmium co-polluted wastewater, and its engineering application value is significant.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0056] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a copper tailings-based adsorbent, characterized in that, include: The copper tailings are crushed and dried to obtain pretreated copper tailings. The pretreated tailings and nitric acid are first mixed and first reacted to obtain acid-modified tailings; The acid-modified tailings and sodium hydroxide are mixed and reacted in a second way to obtain alkali-modified tailings. The alkali-modified tailings and calcium hydroxide are mixed and reacted in a third way to obtain calcium-based reinforced tailings. The calcium-based reinforced tailings were washed with water until neutral and then dried to obtain a copper tailings-based adsorbent.

2. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The copper tailings consist of silicate minerals and aluminosilicate minerals, and their chemical composition, by mass percentage, includes: SiO2 22.8%-69.3%, Al2O3 5.5%-20.1%, K2O 0.93%-4.87%, SO3 0.96%-27.8%, CaO 0.4%-31.8%, Na2O 0.67%-3.86%, Fe2O3 3.7%-36.4%, and MgO 0.5%-11.9%.

3. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The pretreated copper tailings have a particle size of ≤200 mesh and a moisture content of ≤5%.

4. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The first reaction takes 60-120 minutes at room temperature. And / or, the concentration of the nitric acid is 1-3 mol / L, and the solid-liquid ratio of the copper tailings to the nitric acid is 1 g: 10 mL-30 mL.

5. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The second reaction takes 60-240 minutes and is carried out at a temperature of 25-100°C. And / or, the concentration of the sodium hydroxide is 1-5 mol / L, and the solid-liquid ratio of the copper tailings to the sodium hydroxide is 1 g: 10 mL-30 mL.

6. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The time for the third reaction is 30-120 min; And / or, the mass ratio of the copper tailings to the calcium hydroxide is 10:0.5-2.

5.

7. The method for preparing the copper tailings-based adsorbent according to claim 1, characterized in that, The drying process includes vacuum drying; the temperature of the vacuum drying is 60-80℃.

8. A copper tailings-based adsorbent, characterized in that, It is prepared by the method for preparing copper tailings-based adsorbent according to any one of claims 1-7.

9. A method for treating wastewater containing arsenic and cadmium heavy metals, characterized in that, Adsorption was performed using the copper tailings-based adsorbent as described in claim 8.

10. The method for treating arsenic- and cadmium-containing heavy metal wastewater according to claim 9, characterized in that, The copper tailings-based adsorbent has an adsorption capacity of 7.86-60.82 mg / g for arsenic and 9.98-110.78 mg / g for cadmium.

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