Zinc-rich biochar based on sedum plumbizincicola as well as preparation method and application of zinc-rich biochar

Abstract

The invention relates to zinc-rich biochar based on sedum plumbizincicola as well as a preparation method and application thereof, and the method comprises the following steps: 1) drying and crushing sedum plumbizincicola to obtain sedum plumbizincicola powder; (2) the treated sedum plumbizincicola powder is added into a pyrolyzing furnace and pyrolyzed in an oxygen-free environment, the pyrolysis heating rate is 8-12 DEG C / min, the pyrolysis temperature is 400-800 DEG C, and the heat preservation time is 40-80 min; and 4) cooling the pyrolyzed solid residues to room temperature along with the furnace temperature, grinding and screening, and drying to obtain zinc-rich charcoal powder. Compared with the prior art, the method has the advantages that the endogenous heavy metal minerals of the hyperaccumulator are efficiently recycled, and the adsorption capacity of the prepared zinc-rich biochar to ciprofloxacin reaches 254.1 mg / g, which is superior to that of most conventional zinc salt modified biochar.

Description

Technical Field

[0001] The present invention belongs to the field of environmental functional materials and biomass resource utilization, and specifically relates to a preparation method and application of zinc-rich biochar based on ore-associated sedum. Background Art

[0002] As an environmentally friendly soil heavy metal remediation technology, phytoremediation technology has attracted much attention due to its advantages such as simple operation and low cost. However, if the heavy metal-enriched plant residues produced during the phytoremediation process are not properly handled and directly discharged into the environment, it may lead to the release of pollutants in the soil and water, and then cause serious secondary pollution to environmental media such as groundwater and soil. In addition, as a typical plant enriched in Zn, Cd and Pd, the heavy metal minerals and biomass components contained in Sedum sutchuenensis have resource potential. If properly handled, it can not only solve the problem of environmental pollution, but also turn waste into treasure.

[0003] In the prior art, high-temperature pyrolysis is considered to be an effective way to treat phytoremediation residues, which can significantly reduce the volume and amount while producing biochar materials with high added value. In addition, the preparation process can effectively enrich heavy metals in biochar, which is a relatively safe and environmentally friendly disposal method. However, the potential risk of heavy metals enriched in biochar has become an important factor limiting the further resource utilization of phytoremediation residue biochar.

[0004] CN201910888640.3 discloses a super-enriched plant-based biochar and its preparation method and application. Super-enriched plants such as Sedum sedum are naturally air-dried, crushed and pyrolyzed at 500-800℃ without oxygen to obtain super-enriched plant-based biochar, and the obtained super-enriched plant-based biochar is applied to the adsorption and solidification of heavy metal ions. However, this method is to carry out pyrometallurgy of ore in an oxygen-free atmosphere, and the burning process will produce harmful gases and dust, and the reaction of the preparation process not only includes pyrolysis, but also involves melting, reduction and other reactions, resulting in more impurities in the generated biochar, affecting the purity and quality of the biochar. The above-mentioned biochar material has the defects of complicated preparation process and high cost, which is not conducive to the resource utilization of super-enriched plants. At the same time, the prepared biochar material is mainly for heavy metals.

[0005] Fluoroquinolone antibiotics are widely used in the treatment of various infections due to their broad spectrum, high efficacy, long duration of action and ease of use. However, their residues in the environment are difficult to degrade, and their large-scale use causes the continuous accumulation of such antibiotics in the environment. High concentrations of antibiotics not only affect the ecology of water bodies, but also lead to an increase in antibiotic-resistant bacteria and antibiotic-resistant genes, posing a major risk to global public health.

[0006] Adsorption is an important means of removing fluoroquinolone antibiotics. Biochar, as a porous carbon material produced by pyrolysis of biomass, has rich surface functional groups, large specific surface area and developed pore structure, so it has attracted much attention in the field of adsorption. The adsorption performance of biochar can be further improved by physical, chemical or biological modification. CN202410729884.8 and CN201910549244.8 proposed methods for loading zinc ions on biochar to achieve efficient removal of antibiotic pollutants, but these methods require the use of zinc salts such as basic zinc carbonate and zinc chloride as exogenous loading raw materials, and there are problems such as complex synthesis process, high manufacturing cost and potential risk of heavy metal leaching. Therefore, it is of great significance to develop and utilize biomass raw materials rich in endogenous minerals and organic components to prepare biochar in order to achieve the goal of low-cost and efficient removal of pollutants. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a zinc-rich biochar based on Sedum sedum and its preparation method and application, which can solidify heavy metals while showing excellent adsorption performance for fluoroquinolone antibiotics, providing a new idea for the disposal and reuse of hyperaccumulator plants.

[0008] The purpose of the present invention can be achieved by the following technical scheme: a method for preparing zinc-rich biochar based on ore-bearing sedum, the method comprising the following steps:

[0009] 1) drying and crushing the sedum sedum to obtain sedum sedum powder;

[0010] 2) adding the treated sedum powder to a pyrolysis furnace and performing pyrolysis in an oxygen-free environment, with a pyrolysis heating rate of 8 to 12° C. / min, a pyrolysis temperature of 400 to 800° C., and a holding time of 40 to 80 min;

[0011] 3) The solid residue after pyrolysis is cooled to room temperature along with the furnace temperature, then ground and sieved, and dried to obtain zinc-rich biochar powder.

[0012] Furthermore, in step 1), the moisture content of the dried Sedum sedum is controlled to be less than 2wt%.

[0013] Furthermore, after the step 1) is crushed, the powder is sieved to obtain a uniform powder of the associated mineral sedum with a particle size of 0.15 to 0.25 mm.

[0014] Furthermore, the enrichment concentration of Zn in the associated sedum in step 1) is 10-20 mg / g.

[0015] Furthermore, in step 2), the pyrolysis atmosphere is nitrogen, and the nitrogen flow rate is 150 to 450 mL / min.

[0016] Furthermore, the pyrolysis furnace in step 2) is a fixed bed pyrolysis reactor, and the container for holding the associated sedum powder is a quartz crucible.

[0017] Furthermore, step 3) grinds and screens the biochar, specifically comprising: grinding the cooled solid residue in an agate mortar and screening it to <0.15 mm.

[0018] The present invention also provides zinc-rich biochar based on Sedum sedum prepared by the method.

[0019] The present invention also provides an application of zinc-rich biochar based on Sedum sedum, and the zinc-rich biochar based on Sedum sedum is used as an adsorbent to treat fluoroquinolone antibiotics in sewage.

[0020] Furthermore, the amount of zinc-rich biochar added to the sewage is 0.1-0.6 g / L.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0022] (1) The present invention is the first to use the pyrolysis of the hyperaccumulator plant Sedum sedum to prepare zinc-rich biochar. By regulating the pyrolysis temperature, more than 95% of the zinc can be effectively fixed in the biochar, which reduces the pollution risk caused by the escape of heavy metals during the disposal of hyperaccumulator plants and realizes the transformation of heavy metals into treasure. The heavy metal minerals enriched in Sedum sedum can interact with organic matter during pyrolysis, catalyzing the generation of more functional oxidized groups (such as carboxyl, hydroxyl, ketone, etc.), greatly improving the adsorption capacity of biochar for antibiotics; in addition, the zinc ions on the zinc-rich biochar are easy to coordinate with the nitrogen heterocycles and carbonyl groups on the antibiotics, providing more active sites for adsorption.

[0023] (2) The adsorption capacity of ciprofloxacin by the biochar PBC500 prepared at 500°C of the present invention reached 254.1 mg / g, which is better than most conventional zinc salt modified biochars. In addition, in a wide pH range (4-11), the leaching concentrations of Zn, Cd and Pb in the solution after PBC500 adsorption all meet the drinking water safety standards, indicating that the biochar has excellent environmental safety and can be used as an efficient and environmentally friendly adsorption material.

[0024] (3) The present invention provides a simple method for preparing zinc-rich biochar. Compared with the traditional biochar preparation method, this method does not require complicated steps such as co-precipitation or impregnation sintering, and can be achieved through only one-step pyrolysis, which greatly reduces the production cost. The prepared biochar has excellent adsorption performance for fluoroquinolone antibiotics, and the raw material source is wide, which provides a new solution for the disposal of plant remediation residues, and has the dual attributes of pollution control and resource utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a flow chart of the preparation method of zinc-rich biochar based on the associated mineral Sedum sedum in an embodiment of the present invention;

[0026] Figure 2 It is the surface morphology and surface element distribution diagram of the zinc-rich biochar based on the associated mineral Sedum sedum in the embodiment of the present invention;

[0027] Figure 3 This is a comparison diagram of surface functional groups based on zinc-rich biochar from Sedum ore in an embodiment of the present invention;

[0028] Figure 4 This is a comparison chart of the adsorption capacity of ciprofloxacin based on the zinc-rich biochar of Sedum sedum in the embodiments of the present invention;

[0029] Figure 5 This is a relationship diagram between the adsorption capacity of ciprofloxacin by zinc-rich biochar based on Sedum sedum in an embodiment of the present invention and the pH of the initial solution. DETAILED DESCRIPTION

[0030] The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate the same or corresponding components and features.

[0031] like Figure 1 As shown, it is a flow chart of a zinc-rich biochar based on Sedum ore and a preparation method thereof according to an embodiment of the present invention, comprising the following steps:

[0032] Step 1) Drying the mineral-associated sedum: subjecting the mineral-associated sedum to hot air drying;

[0033] Step 2) crushing the mineral companion sedum: mechanically crushing the dried mineral companion sedum, and sieving to obtain uniform mineral companion sedum powder after crushing;

[0034] Step 3) adding the ore-bearing sedum powder into a pyrolysis furnace, adjusting the pyrolysis temperature, and performing pyrolysis in an oxygen-free environment;

[0035] Step 4) After the pyrolysis is completed, the cooled solid residue is ground and sieved, and hot air dried to obtain zinc-rich biochar powder.

[0036] Unless otherwise specified, the reagents used in the present invention are all commercially available. In the specific embodiment of the present invention, the mineral companion sedum was collected from a heavy metal contaminated plot in Jiangsu Province, and its dry basis chemical composition is shown in Table 1. The heavy metal analysis results show that each gram of dry sample contains 18.515 mg Zn, 0.535 mg Cd and 0.165 mg Pb, respectively.

[0037] Table 1 Chemical composition of the dry base of Sedum sedum

[0038] Elemental analysis wt.% Proximate analysis wt.% Heavy metal concentration mg / g C 29.76 Ash 32.18 Cd 0.535 H 3.78 Volatile Matter 57.6 Pd 0.165 N 2.11 Fixed Carbon 10.22 Zn 18.515 S 0.22 O 3.32

[0039] In the present invention, during pyrolysis, the container used for containing the associated ore sedum is a quartz boat, which can withstand high temperatures and has stable performance.

[0040] In the present invention, the pyrolysis furnace is preferably a fixed bed pyrolysis reactor. Before the fixed bed pyrolysis reactor is used, the air tightness and air exhaust of the fixed bed pyrolysis reactor are checked. The specific operation is: after putting the material, nitrogen is introduced into the furnace body, the nitrogen flow rate is 300-450mL / min, and the ventilation time is 15min.

[0041] Example 1

[0042] A method for preparing zinc-rich biochar based on sedum ore, comprising the following steps:

[0043] (1) 300 g of the collected Sedum sedum was placed on a tray, placed in an oven, and dried at 105° C. until the moisture content was less than 2 wt %;

[0044] (2) placing the dried Sedum sedum into a crusher to obtain a powder with a particle size of 0.15 to 0.25 mm, and performing secondary drying to keep the moisture content of the Sedum sedum powder less than 2 wt %;

[0045] (3) 5 g of Sedum sedum powder was placed in a fixed bed pyrolysis reactor with a nitrogen flow rate of 200 mL / min. The pyrolysis reaction temperature was 400 °C, the heating rate was 10 °C / min, and the pyrolysis was continued for 60 min after reaching the target temperature;

[0046] (4) The solid residue after pyrolysis was cooled to room temperature along with the furnace temperature. The cooled biochar was ground and sieved in an agate mortar, and then dried in an oven at 105°C overnight to obtain biochar powder with a particle size of <0.15 mm. The powder was stored in a desiccator for later use and named PBC400.

[0047] Example 2

[0048] The only difference from Example 1 is that the pyrolysis reaction temperature in step (3) is 500° C. and the resulting biochar is named PBC500.

[0049] Example 3

[0050] The only difference from Example 1 is that the pyrolysis reaction temperature in step (3) is 600° C. and the obtained biochar is named PBC600.

[0051] Example 4

[0052] The only difference from Example 1 is that the pyrolysis reaction temperature in step (3) is 700° C. and the resulting biochar is named PBC700.

[0053] Example 5

[0054] The only difference from Example 1 is that the pyrolysis reaction temperature in step (3) is 800° C. and the resulting biochar is named PBC800.

[0055] In order to illustrate the technical effect of the present invention, the following experiment is carried out:

[0056] 1. The surface morphology and surface element analysis of PBC500, PBC700 and PBC800 prepared in Examples 2, 4 and 5 were analyzed by scanning electron microscopy and EDS. Figure 2 As shown in the figure, it can be seen that the surface morphology of the biochar PBC obtained in each embodiment presents a porous honeycomb structure, and the pore size gradually increases with the increase of the pyrolysis temperature. The EDS analysis results show that the surface of the biochar contains elements such as C, O, and Zn, indicating that there are abundant zinc ions on the surface of the biochar, which provides potential active sites for the adsorption of CIP.

[0057] 2. Analyze the surface functional groups of PBC400-800 prepared in Examples 1-5 by infrared spectroscopy. Figure 3 As shown in the figure, it can be seen that the PBC surface contains a large number of functional groups located at 3431cm -1 The broad and strong absorption peak near 1630cm is attributed to the stretching vibration of hydroxyl (-OH), indicating that there are a large number of hydroxyl groups on the surface of biochar. -1 、1401cm -1 、1032cm -1 The nearby peaks are attributed to the stretching vibrations of carbon-carbon double bonds (C=C), carboxyl groups (-COOH), and ether bonds (COC). These functional groups can interact with the active sites on the surface of biochar through π-π electrons, hydrogen bonds, and protonation reactions, thereby improving the adsorption performance of biochar.

[0058] 3. The toxicity characteristic leaching procedure (TCLP) was used to simulate the heavy metal leaching behavior of PBC400-800 prepared in Examples 1-5 in the environment. The test results are shown in Table 2. Among them, the leaching concentrations of Zn, Cd, and Pd of PBC500, PBC700, and PBC800 are far lower than the threshold values ​​specified by the US EPA and the Chinese national standards (Table 3), indicating that the pyrolysis process effectively reduces the bioavailability of heavy metals in biochar.

[0059] Table 2 Concentrations and percentages of Zn, Cd and Pb in TCLP extracts of PBC under different conditions

[0060] sample Zn(mg / L) Zn(%) Cd(mg / L) Cd(%) Pb(mg / L) Pb(%) PBC400 223.8 12.426 0.23 0.541 0.02 0.110 PBC500 36.99 1.750 0.01 0.255 0.01 0.047 PBC600 579.4 34.604 ND ND ND ND PBC700 0.53 0.035 ND ND ND ND PBC800 0.05 0.032 ND ND ND ND

[0061] Table 3 TCLP leaching concentration limit standards

[0062] Limit Standard Zn(mg / L) Cd(mg / L) Pb(mg / L) USA (40CFR.261.24) / 1 5 China (GB 5085.3-2007) 100 1 5

[0063] 4. The adsorption capacity of PBC500, 700 and 800 prepared in Examples 2, 4 and 5 for ciprofloxacin was tested by batch adsorption experiment. The specific contents are as follows: 2 mg of biochar was placed in a polypropylene centrifuge tube containing 50 mL of CIP solution with different initial concentrations (40-200 mg / L), and oscillated in a constant temperature oscillator (180 rpm) for 24 hours to reach adsorption equilibrium. After the adsorption, 5 mL of supernatant was taken, filtered through a 0.45 μm filter membrane, and the residual CIP concentration was measured at a wavelength of 273 nm using a UV-visible spectrophotometer (Perkin-Elmer Lambda 365, China). The test results are as follows: Figure 4 As shown, the isotherm adsorption curve fitting parameters are listed in Table 4. The theoretical maximum adsorption capacity of PBC500 for CIP can reach 254.1 mg / g, which is better than most conventional zinc salt modified biochars. For example, the maximum adsorption capacity of modified Alternaria japonica reported in existing public literature is 200.8 mg / g and the maximum adsorption capacity of modified nut shell is 198.13 mg / g.

[0064] Table 4 Adsorption isotherm model fitting parameters

[0065]

[0066] 5. A batch adsorption experiment was conducted to detect the adsorption of ciprofloxacin by PBC500 prepared in Example 2 at different initial pH values. The specific contents are as follows: The pH value of the solution containing ciprofloxacin was adjusted to between 3 and 11 by titration with 0.1 mol / L NaOH or HCl solution, 2 mg of biochar was placed in a polypropylene centrifuge tube containing 50 mL of an initial CIP solution of 40 and 200 mg / L, and oscillated in a constant temperature oscillator (180 rpm) for 24 hours to achieve adsorption equilibrium. After the adsorption was completed, 5 mL of the supernatant was taken, filtered through a 0.45 μm filter membrane, and the residual CIP concentration was determined at a wavelength of 273 nm using a UV-visible spectrophotometer. The test results are as follows: Figure 5 As shown in the figure, PBC500 exhibits the best adsorption capacity under weakly acidic conditions of pH = 6-7, which is similar to the pH range of natural water bodies and has good practical application prospects.

[0067] The precipitation concentrations of Zn, Cd and Pb in the solution after the PBC500 adsorption prepared in Example 2 are shown in Table 5. In a wide pH range (4-11), the precipitation concentrations of Zn, Cd and Pb are much lower than the limit values ​​specified in the "Sanitary Standard for Drinking Water" (GB 5749-2006), which once again verifies the environmental safety of the zinc-rich biochar prepared by the present invention for adsorption.

[0068] Table 5 Precipitation concentrations of Zn, Cd and Pb in the solution after adsorption at different pH values

[0069]

[0070] The present invention prepares zinc-rich biochar by pyrolysis of Sedum sedum, and by precisely controlling the pyrolysis temperature, heavy metals can be effectively fixed in the biochar, reducing the pollution risk caused by the escape of heavy metals in the preparation process while achieving efficient recycling of heavy metal resources. The heavy metal minerals enriched in Sedum sedum can interact with organic matter during pyrolysis, catalyzing the generation of more functional oxidized groups (such as carboxyl, hydroxyl, ketone, etc.), which can greatly improve the adsorption capacity of antibiotics; in addition, the zinc ions on the zinc-rich biochar are easy to coordinate with the nitrogen heterocycles and carbonyl groups on the antibiotics, providing more active sites for adsorption; compared with zinc salt modification, this method avoids the introduction of additional chemical substances, and the naturally enriched zinc element is tightly combined with the biomass matrix, and after pyrolysis, it forms a variety of existence forms in the biochar, further improving the stability of zinc, reducing secondary pollution to the environment, and having the dual attributes of pollution control and resource utilization.

[0071] The present invention provides a method and application idea for preparing zinc-rich biochar materials based on mineral-bearing sedum. There are many methods and ways to implement the technical solution. The above-mentioned specific implementation cases are only preferred implementation cases of the present invention, and are not used to limit the scope of implementation of the present invention. That is, all equivalent changes and modifications made according to the content of the patent application scope of the present invention should be regarded as the technical scope of the present invention.

Claims

1. A method for preparing zinc-rich biochar based on ore-bearing sedum, characterized in that: The method comprises the following steps: 1) drying and crushing the sedum sedum to obtain sedum sedum powder; 2) adding the treated sedum powder to a pyrolysis furnace and performing pyrolysis in an oxygen-free environment, with a pyrolysis heating rate of 8 to 12° C. / min, a pyrolysis temperature of 400 to 800° C., and a holding time of 40 to 80 min; 3) The solid residue after pyrolysis is cooled to room temperature along with the furnace temperature, then ground and sieved, and dried to obtain zinc-rich biochar powder.

2. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: Step 1) controlling the moisture content of the dried Sedum sedum to be less than 2wt%.

3. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: Step 1) After crushing, sieving is performed to obtain uniform sedum powder with a particle size of 0.15 to 0.25 mm.

4. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: The enrichment concentration of Zn in the associated sedum in step 1) is 10-20 mg / g.

5. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: Step 2) The pyrolysis atmosphere is nitrogen, and the nitrogen flow rate is 150-450 mL / min.

6. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: Step 2) The pyrolysis furnace is a fixed bed pyrolysis reactor, and the container for holding the associated sedum powder is a quartz crucible.

7. The method for preparing zinc-rich biochar based on Sedum sedum according to claim 1, characterized in that: Step 3) grinding and screening the biochar, specifically comprising: grinding the cooled solid residue in an agate mortar and screening to <0.15 mm.

8. A zinc-rich biochar based on Sedum sedum obtained by any one of the methods of claims 1 to 7.

9. An application of zinc-rich biochar based on Sedum ore-bearing plant as claimed in claim 8, characterized in that: The zinc-rich biochar based on Sedum sedum is used as an adsorbent to treat fluoroquinolone antibiotics in sewage.

10. The use of zinc-rich biochar based on ore-bearing Sedum according to claim 9, characterized in that: The zinc-rich biochar is added to the sewage in an amount of 0.1 to 0.6 g / L.

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