Method for treating heavy metal wastewater using n-functionalized tourmaline / biochar composite material

Abstract

The application discloses a method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite materials, and the method is to adsorb heavy metals in wastewater by using N-functionalized tourmaline / biochar composite materials, wherein the N-functionalized tourmaline / biochar composite materials are prepared by pyrolysis of biomass, tourmaline and a nitrogen source as precursor raw materials. The method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite materials has the advantages of simple process, convenient operation, low cost, high treatment efficiency, good removal effect and the like, can efficiently remove heavy metals in wastewater, and has high application value and good application prospect. For example, for wastewater containing Pb 2+ and Cd 2+ , adsorption equilibrium can be reached in 60 min, and the adsorption amount of Pb 2+ and Cd 2+ can reach 603.89 mg / g and 143.45 mg / g respectively, and the method has high application value and good application prospect, and has important promoting effect on realizing effective treatment of heavy metal wastewater.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heavy metal wastewater treatment, and relates to a method for treating heavy metal wastewater, in particular to a method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite materials. BACKGROUND

[0002] Biochar is a kind of porous and highly aromatic black solid formed by pyrolysis of biomass under anoxic or anaerobic conditions. Many biomasses including agricultural and forestry wastes, fruit and vegetable wastes and industrial sludge can be used to prepare biochar. Due to the low production cost of biochar, it exhibits good adsorption capacity for heavy metal ions and is widely used in the fields of environmental protection such as agriculture, ecological restoration and soil improvement. Moreover, the composite materials prepared by integrating biochar as a carrier with other materials (nanomaterials, metal oxides and inorganic minerals) can improve the adsorption capacity for heavy metals. Among them, inorganic mineral materials have the advantages of low cost, wide source and self-adsorption of heavy metals, and are gradually favored by more and more scholars for remediation of heavy metal pollution. Common inorganic minerals combined with biochar are silicate minerals such as montmorillonite, kaolin, bentonite and attapulgite, which not only have a certain adsorption capacity for heavy metals, but also can improve the specific surface area, pore structure and surface functional groups of biochar, and the prepared biochar composite materials show good potential in the treatment of heavy metal contaminated water and soil.

[0003] Tourmaline is a complex ring silicate mineral, and its general chemical formula can be represented as XY3Z6[Si6O 18 ][B3O9]W4. X can represent Ca, Na, K or a vacancy; Y can represent Li+, Fe 2+ , Fe 3+ , Al 3+ , Mg 2+ , Cr 3+ , V 3+ ; Z can represent V 3+ , Fe 3+ , Fe 3+ , Al 3+ , Mg 2+ ; W can represent OH, F, O, wherein X, Y and Z are prone to substitution. Tourmaline itself has a permanent spontaneous polarization effect, and its surface is negatively charged, which is beneficial to adsorb various positive metal ions. However, tourmaline has poor dispersibility and fluidity due to the large surface energy caused by spontaneous polarity and the agglomeration between particles, so it has not been fully utilized in the field of environmental remediation.

[0004] The tourmaline and the biochar material are compounded to prepare a composite material, which can improve the agglomeration of the tourmaline to some extent and enhance the adsorption performance of the composite material on heavy metals. However, the existing composite material based on the tourmaline and the biochar still has defects such as a small adsorption amount, a slow adsorption speed, a complex preparation process, a long cycle, a high energy consumption and a high cost, for example, in the prior art, the biochar and the tourmaline are solidified to form composite pellets by using polyvinyl alcohol, sodium alginate and calcium chloride, and then the composite pellets are burned to obtain a biochar / tourmaline adsorbent, and the adsorbent has an adsorption amount of 7.54 mg / g on lead (Pb) when the adsorbent is used to treat Pb wastewater. Moreover, the preparation process of the biochar / tourmaline adsorbent is complex and has a long cycle, the biochar and the tourmaline need to be pretreated, and the biochar and the tourmaline need to be pyrolyzed twice, so the energy consumption is high and the cost is high. Furthermore, in the prior art, the tourmaline or modified tourmaline is mixed with the biochar to perform ball milling, and the heavy metal pollution remediation agent is formed after drying, and the remediation agent has an adsorption amount of 48.55 mg / g on cadmium. Moreover, in the preparation process of the remediation agent, the ball milling has a high requirement on equipment, and the ball milling process has a high energy consumption and needs to consume a large amount of electric power, so the cost is very high. Therefore, how to obtain an adsorbent with a high adsorption amount on heavy metals in wastewater, a fast adsorption speed, a simple process and a low cost is of great significance for quickly and completely removing heavy metals in wastewater. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the shortcomings of the prior art and provide a method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite material, which has a simple process, is convenient to operate, has a low cost, is high in treatment efficiency and good in removal effect.

[0006] To solve the above technical problems, the present application adopts the following technical solutions.

[0007] A method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite material, wherein the method is to adsorb heavy metals in wastewater by using the N-functionalized tourmaline / biochar composite material, and the N-functionalized tourmaline / biochar composite material is prepared from biomass, tourmaline and a nitrogen source as precursor raw materials through pyrolysis.

[0008] The method is further improved, and the preparation method of the N-functionalized tourmaline / biochar composite material comprises the following steps.

[0009] S1, mixing biomass, tourmaline and a solution containing a nitrogen source, stirring, centrifuging, freezing and drying the obtained solid to obtain a precursor;

[0010] S2, pyrolyzing the precursor to obtain the N-functionalized tourmaline / biochar composite material.

[0011] The method is further improved, and in the step S1, the amount of the nitrogen source is 0-200% of the mass of the biomass, but not 0; the nitrogen source is one of urea, ammonium sulfate and ammonium nitrate.

[0012] The method is further improved, and in the step S1, the amount of the tourmaline is 0-10% of the mass of the biomass, but not 0.

[0013] The method is further improved, and in the step S1, the biomass is at least one of orange peel, tangerine peel, grapefruit peel, lemon peel and orange peel; before use, the biomass material is dried, crushed, sieved through a 60-100 mesh sieve, and the biomass powder is obtained.

[0014] The method is further improved, and in the step S1, the stirring time is 12-36 hours; the freezing is carried out at a temperature of-18 to-21 DEG C; the freezing time is 12-24 hours; the drying is carried out under vacuum; the drying is carried out at a temperature of-45 to-60 DEG C; and the drying time is 24-72 hours.

[0015] The method is further improved, and in the step S2, the pyrolysis temperature is 400-800 DEG C; and the pyrolysis time is 1-3 hours.

[0016] The method is further improved, and the N-functionalized tourmaline / biochar composite material is used to adsorb heavy metals in wastewater, and the method comprises the following steps: mixing the N-functionalized tourmaline / biochar composite material with the heavy metal wastewater and oscillating adsorption, so as to complete the treatment of the heavy metal wastewater.

[0017] The method is further improved, and the amount of the N-functionalized tourmaline / biochar composite material added is 0.5 g per liter of heavy metal wastewater.

[0018] The method is further improved, and the heavy metal in the heavy metal wastewater is at least one of Pb 2+ , Cd 2+ ; the initial concentration of Pb 2+ in the heavy metal wastewater is ≤600 mg / L; and the initial concentration of Cd 2+ in the heavy metal wastewater is ≤200 mg / L.

[0019] The method is further improved, and the oscillation adsorption time is 6-48 hours.

[0020] Compared with the prior art, the method has the following advantages:

[0021] (1)In view of the small adsorption amount of heavy metals, slow adsorption speed, complex preparation process, long cycle, high energy consumption and high cost of the existing tourmaline / biochar composite material and the defects caused thereby, such as difficult to quickly and completely remove heavy metals in wastewater, the application creatively proposes a method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite material, and uses the N-functionalized tourmaline / biochar composite material as an adsorbent to adsorb heavy metals in wastewater, wherein the N-functionalized tourmaline / biochar composite material is prepared by pyrolysis of biomass, tourmaline and nitrogen source as precursor raw materials, and has the advantages of many heavy metal adsorption sites on the surface and many nitrogen-containing functional groups, so that the heavy metals in the wastewater can be quickly adsorbed and transferred to the composite material, thereby realizing effective treatment of heavy metals. Taking wastewater containing Pb 2+ and Cd 2+ as an example, in the method, the N-functionalized tourmaline / biochar composite material can reach adsorption equilibrium in 60 min, and the adsorption amount of Pb 2+ and Cd 2+ can reach 603.89 mg / g and 143.45 mg / g, respectively. Compared with the existing conventional adsorption method, the method for treating heavy metal wastewater by using N-functionalized tourmaline / biochar composite material has the advantages of simple process, convenient operation, low cost, high treatment efficiency and good removal effect, can efficiently remove heavy metals in wastewater, has high use value and good application prospect, and plays an important role in promoting effective treatment of heavy metal wastewater.

[0022] (2) In the present application, the preparation method of the N-functionalized tourmaline / biochar composite material comprises the following steps: first, biomass and tourmaline are stirred in a solution containing a N source until they are fully uniform, the solid is centrifuged and separated, and the precursor is obtained by freeze-drying; on this basis, the precursor is pyrolyzed, and the product is an N-functionalized tourmaline / biochar composite material. In the process of pyrolysis into carbon material, tourmaline particles are deposited on the surface of biochar and form many small wrinkles and particles, which increases the number of adsorption sites and the number of surface cations, is beneficial to improve the adsorption rate, and is beneficial to increase the possibility of ion exchange and precipitation. More importantly, the doping of nitrogen elements disturbs the electron distribution on the surface of the material, thereby increasing the complexation of the material to heavy metals and metal-pi interaction. In addition, in the preparation method of the N-functionalized tourmaline / biochar composite material of the present application, the raw material is abundant, cheap and easy to obtain, environmentally friendly, and has the advantages of simple process, convenient operation, no complex chemical reaction and harsh reaction conditions, no special equipment, etc. For large-scale preparation of N-functionalized tourmaline / biochar composite material, it is convenient to realize the industrial application of N-functionalized tourmaline / biochar composite material, and is conducive to promoting the wide application of N-functionalized tourmaline / biochar composite material in heavy metal wastewater treatment. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application.

[0024] Figure 1 Scanning electron microscope images of tourmaline (TM), biochar (BC), tourmaline / biochar composite material (TMBC) and N-functionalized tourmaline / biochar composite material (N-TMBC) prepared in Example 1 of the present application.

[0025] Figure 2 X-ray diffraction analysis graphs of tourmaline (TM), biochar (BC), tourmaline / biochar composite material (TMBC) and N-functionalized tourmaline / biochar composite material (N-TMBC) prepared in Example 1 of the present application.

[0026] Figure 3 Fourier infrared spectrograms of tourmaline (TM), biochar (BC), tourmaline / biochar composite material (TMBC) and N-functionalized tourmaline / biochar composite material (N-TMBC) prepared in Example 1 of the present application.

[0027] Figure 4To compare the adsorption capacity of tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC) and N-functionalized tourmaline / biochar composite (N-TMBC) to Pb 2+ / Cd 2+ in Example 1 of the present application. DETAILED DESCRIPTION

[0028] The present application is further described in conjunction with the accompanying drawings and specific preferred embodiments, but the scope of the present application is not limited by the following examples. The materials and instruments used in the following examples are commercially available.

[0029] Example 1

[0030] A method for treating heavy metal wastewater using N-functionalized tourmaline / biochar composite, specifically, adsorbing heavy metals in wastewater using N-functionalized tourmaline / biochar composite, comprising the following steps:

[0031] According to the amount of N-functionalized tourmaline / biochar composite is 0.5 g / L, 10 mg of N-functionalized tourmaline / biochar composite (N-TMBC) is added to 20 mL of solution containing Pb 2+ and Cd 2+ (the concentration of Pb 2+ in the solution is 500 mg / L, and the concentration of Cd 2+ is 100 mg / L), stirred uniformly, and oscillated on a shaker for 12 h to complete the treatment of heavy metal wastewater.

[0032] Control group 1: tourmaline (TM) is used instead of N-functionalized tourmaline / biochar composite, and other conditions are the same.

[0033] Control group 2: biochar (BC) is used instead of N-functionalized tourmaline / biochar composite, and other conditions are the same.

[0034] Control group 3: tourmaline / biochar composite (TMBC) is used instead of N-functionalized tourmaline / biochar composite, and other conditions are the same.

[0035] In this example, the N-functionalized tourmaline / biochar composite (N-TMBC) is prepared from biomass, tourmaline, and a solution containing N source after freezing, drying, and pyrolysis, and specifically includes the following steps:

[0036] (1) Using pomelo peel as biomass, collect pomelo peel, wash off surface impurities, dry, crush with a crusher, and pass through a 60-100 mesh sieve to obtain pomelo peel powder.

[0037] (2) The grapefruit peel powder and urea were mixed at a mass ratio of 1:1 and the mass of tourmaline powder was 5% of that of grapefruit peel powder. The grapefruit peel powder, tourmaline powder (commercially available), and urea solution (which was prepared by dissolving urea in water) were mixed and stirred for 24 hours. The solid was collected by centrifugation and pre-frozen at -21°C for 12 hours. The solid was then placed in a vacuum freeze dryer and dried at -51°C for 48 hours to obtain the precursor.

[0038] (3) The above precursor was placed in a muffle furnace and pyrolyzed at 600°C for 2 hours to obtain N-functionalized tourmaline / biochar composite material.

[0039] In this embodiment, the preparation method of tourmaline / biochar composite material (TMBC) is basically the same as that of N-functionalized tourmaline / biochar composite material (N-TMBC), except that urea is not added in the preparation method of tourmaline / biochar composite material (TMBC).

[0040] In this embodiment, the biochar (BC) used is prepared by the following method: using grapefruit peel as biomass, grapefruit peel is collected, surface impurities are washed away, dried, pulverized with a pulverizer, and passed through a 60-100 mesh sieve to obtain grapefruit peel powder; the grapefruit peel powder is placed in a muffle furnace and pyrolyzed at 600°C for 2 hours to obtain biochar.

[0041] Figure 1 These are scanning electron microscope (SEM) images of the tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC), and N-functionalized tourmaline / biochar composite (N-TMBC) prepared in Example 1 of this invention. Figure 1 As observed at 9000x magnification, the TM surface mainly exists in a blocky state, the BC surface is relatively loose and smooth, while the TMBC and N-TMBC surfaces are rough and have many small particles deposited, indicating the loading of tourmaline particles on the composite material surface. Furthermore, many small wrinkles and particles are deposited on the surface of the N-functionalized tourmaline / biochar composite material. Therefore, the N-functionalized tourmaline / biochar composite material of this invention has a rougher surface, which is beneficial for the adhesion of heavy metals.

[0042] In addition, from the X-ray energy spectrum element analysis results of the tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC) and N-functionalized tourmaline / biochar composite (N-TMBC), it can be known that the composition on the surface of the BC is relatively simple, the surface composition of the TM is relatively complex and contains multiple elements, and the same complex element composition and Fe and Si elements representing typical elements of tourmaline are also observed on the surface of the composite TMBC and N-TMBC. In addition, the cation Na, K and Ca element content on the surface of the N-TMBC is more than that of the TMBC, which also provides more ion exchange sites for the N-TMBC to adsorb heavy metals Pb and Cd in the aqueous solution, and thus has more excellent adsorption performance.

[0043] Figure 2 The X-ray diffraction analysis chart of the tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC) and N-functionalized tourmaline / biochar composite (N-TMBC) prepared in the embodiment 1 of the application is shown in the figure. Figure 2 It can be known that the phase composition of the TM is relatively complex, and the phase composition of the BC is relatively simple in comparison, and the diffraction is mainly CaCO3 (corresponding to Jade.PDF card #05-0586) and K2Ca(CO3)2 (corresponding to Jade.PDF card #03-0504). The phase composition of the TMBC and N-TMBC is relatively complex, and the characteristic diffraction peaks of the TM, CaCO3 and K2Ca(CO3)2 can basically be observed. In addition, since the TM is a silicate mineral, the peak of SiO2 is observed at a diffraction angle of 26.67°, and the same is also observed on the TMBC and N-TMBC. The existence of the mineral salt and SiO2 provides more ion exchange sites and complex sites for the adsorption of heavy metals on the composite.

[0044] Figure 3 The Fourier infrared spectrum of the tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC) and N-functionalized tourmaline / biochar composite (N-TMBC) prepared in the embodiment 1 of the application is shown in the figure. Figure 3 It can be known that the N-TMBC contains more types of functional groups and more utilizes the adsorption of heavy metals.

[0045] In this embodiment, after the oscillation adsorption is completed, the Pb 2+ / Cd 2+ concentration in the filtrate is measured, the adsorption amount is calculated, and the result is shown in the figure. Figure 4

[0046] Figure 4 ​The effects of tourmaline (TM), biochar (BC), tourmaline / biochar composite (TMBC), and N-functionalized tourmaline / biochar composite (N-TMBC) on Pb in Example 1 of this invention. 2+ / Cd 2+ A comparison chart of adsorption amounts. (From...) Figure 4 It can be seen that N-functionalized tourmaline / biochar composite material (N-TMBC) has a positive effect on Pb. 2+ and Cd 2+ The adsorption capacity of BC can reach 603.89 mg / g and 143.45 mg / g, while BC adsorbs Pb. 2+ and Cd 2+ The adsorption capacities of TMBC were only 439.02 mg / g and 97.55 mg / g, respectively, for Pb. 2+ and Cd 2+ The adsorption capacities were only 492.64 mg / g and 114.05 mg / g. Comparison shows that the N-functionalized tourmaline / biochar composite material (N-TMBC) of this invention, when used as an adsorbent, can achieve effective adsorption of Pb in the aquatic environment. 2+ and Cd 2+ Its highly efficient adsorption is something that other materials cannot achieve.

[0047] In summary, the method for treating heavy metal wastewater using N-functionalized tourmaline / biochar composite materials has advantages such as simple process, convenient operation, low cost, high treatment efficiency, and good removal effect. It can efficiently remove heavy metals from wastewater, especially those containing Pb. 2+ and Cd 2+ Taking wastewater as an example, in the method of this invention, the N-functionalized tourmaline / biochar composite material can reach adsorption equilibrium in 60 minutes, and it is effective against Pb. 2+ and Cd 2+ The adsorption capacities reached 603.89 mg / g and 143.45 mg / g, respectively, indicating high application value and promising prospects. They play an important role in promoting the effective treatment of heavy metal wastewater.

[0048] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for treating heavy metal wastewater using N-functionalized tourmaline / biochar composite material, characterized in that, The method is to use N-functionalized tourmaline / biochar composite material to adsorb heavy metals in wastewater; the N-functionalized tourmaline / biochar composite material is prepared by pyrolysis of biomass, tourmaline, and nitrogen source as precursor raw materials, including the following steps: S1, the biomass, tourmaline, and solution containing nitrogen source are mixed, stirred, centrifuged, and the obtained solid is frozen and dried to obtain a precursor; the freezing is carried out at a temperature of-18 ℃ to-21 ℃; the freezing time is 12h to 24h; the drying is carried out at a temperature of-45 ℃ to-60 ℃; the drying time is 24h to 72h; S2, the precursor is pyrolyzed to obtain N-functionalized tourmaline / biochar composite material.

2. The method of claim 1, wherein, In step S1, the amount of nitrogen source is 0-200% of the mass of biomass, but not 0; the nitrogen source is one of urea, ammonium sulfate and ammonium nitrate.

3. The method of claim 2, wherein, In step S1, the amount of tourmaline is 0-10% of the mass of biomass, but not 0.

4. The method of claim 3, wherein, In step S1, the biomass is at least one of orange peel, tangerine peel, grapefruit peel, lemon peel and orange peel; before use, the biomass also includes the following treatment: drying the biomass material, crushing, passing through a 60-100 mesh screen, and obtaining a biomass powder.

5. The method of claim 1, wherein, In step S1, the stirring time is 12h to 36h; the drying is carried out under vacuum conditions; In step S2, the pyrolysis temperature is 400℃ to 800℃; the pyrolysis time is 1h to 3h.

6. The method according to any one of claims 1 to 5, characterized in that, The N-functionalized tourmaline / biochar composite material is used to adsorb heavy metals in wastewater, including the following steps: mixing the N-functionalized tourmaline / biochar composite material with heavy metal wastewater and oscillating adsorption to complete the treatment of heavy metal wastewater.

7. The method of claim 6, wherein, The addition amount of the N-functionalized tourmaline / biochar composite material is 0.5g per liter of heavy metal wastewater.

8. The method of claim 7, wherein, The heavy metal in the heavy metal wastewater is at least one of Pb 2+ , Cd 2+ ; the initial concentration of Pb 2+ in the heavy metal wastewater is ≤600 mg / L; the initial concentration of Cd 2+ in the heavy metal wastewater is ≤200 mg / L.

9. The method of claim 6, wherein, The oscillation adsorption time is 6h to 48h.

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