Iron-modified cow dung biochar material as well as preparation method and application thereof

Abstract

The invention discloses an iron-modified cow dung biochar material as well as a preparation method and application thereof, and belongs to the technical field of new material and resource recycling. The preparation method comprises the following steps: dipping a cow dung solid waste biomass raw material in a K2FeO4 solution, heating in a water bath, drying to obtain a K2FeO4 composite biomass material, and carbonizing at high temperature in a tubular furnace to obtain the K2FeO4 modified cow dung biochar material (FCBC). The K2FeO4 modified cow dung biochar material (FCBC) provided by the invention has better Cd < 2 + > elimination treatment capacity than unmodified cow dung biochar (CBC), and also has an incomparable Cd < 2 + > adsorption effect compared with traditional modified or unmodified plant-derived biochar. According to the method, the practical scene of the livestock and poultry manure waste is widened, the aims of harmlessness, reduction and recycling of the manure are achieved, and more optimal schemes can be provided for prevention and treatment of water and soil pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of new materials and resource recycling, and specifically relates to an iron-modified cow dung biochar material and a preparation method and application thereof. Background Art

[0002] Heavy metals are mainly found in agricultural soil, lakes, rivers and groundwater. They are non-biodegradable, have a wide range of pollution and are highly harmful, posing a serious threat to the ecological environment and human life and health. Generally, heavy metals are difficult to degrade into less toxic chemicals, but they are easily transferred from water to organisms and eventually enter the human body through the food chain. If you drink or are exposed to water contaminated by heavy metals for a long time, important organs such as the human skin, kidneys and nervous system will be damaged to varying degrees. Global industrial modernization and agricultural modernization have led to increasingly serious water pollution. Among them, the content of heavy metals Hg, Cd and Pb in water bodies exceeds the standard. How to effectively control heavy metals in wastewater and thus ensure the safety of water environment quality and human health has become an important scientific issue that needs to be solved urgently. This will be of great significance to maintaining the safety of water ecosystems and ensuring sustainable economic development.

[0003] At present, most of the research on using biochar to adsorb Cd in wastewater focuses on biochar prepared from plant sources (wood chips, straw, corn cobs, rice husks and fruit shells, etc.) and municipal sludge, and has made some progress. Related reports show that the biochar obtained by direct pyrolysis of raw biomass has a very limited ability to remove pollutants from wastewater, while modified biochar obtained by different modification methods can usually improve its adsorption performance, which is directly related to the biochar raw material and modification method. For example, Zhang et al. (2021) used lobster shell biochar as raw material, and the prepared original biochar and MgCl2-modified biochar had a significant effect on the removal of Cd in solution. 2+ The saturated adsorption capacities of -1 and 93.6 mg g -1 Qiu et al. (2019) used hickory wood as raw material and used biochar prepared by modification with NaOH, citric acid and K2FeO4 to remove Cd in solution. 2+ The saturated adsorption capacities of -1 , 18.5mg·g -1 and 32.5 mg g -1 Among the many modification methods, iron modification is often used to improve the removal capacity of heavy metal ions in wastewater. For example, Cui Zhiwen et al. (2020) found that the specific surface area, aromatic and oxygen-containing functional groups of wheat straw biochar modified with KOH and FeCl3 were significantly increased, and the removal of Cd 2+Yang et al. (2019) revealed that Fe / Zn composite oxide modified biochar can effectively improve the adsorption of Cd in water. 2+ The main adsorption mechanism is Cd 2+ Co-precipitation with carbonates and complexation with oxygen-containing functional groups. Analysis shows that the current iron modification methods are complicated, the raw materials for biochar are numerous, and the modification effects are also mixed. Therefore, it is urgent to explore and develop an iron modification technology and biochar raw materials with simple preparation process and significant heavy metal removal effect. In addition, large-scale livestock and poultry farming is increasing in my country, and its animal manure production is as high as 4 billion tons / year, but the effective utilization efficiency is less than 60% (Zhang et al., 2015; Su et al., 2022). Obviously, if the livestock and poultry manure, which is a common agricultural and animal husbandry waste, is not properly handled, it will cause a series of water and soil environmental pollution problems. Therefore, choosing livestock and poultry manure as a raw material to prepare biochar remediation materials for water and soil pollution control can not only achieve the goals of harmless, reduced and resourceful manure, but also provide more preferred solutions for water and soil pollution prevention and control. Summary of the invention

[0004] To improve the Cd 2+ The present invention provides an iron-modified cow dung biochar material and a preparation method thereof in Cd 2+ Specifically, the present invention is implemented by the following technical solution:

[0005] First, the present invention provides a method for preparing an iron-modified cow dung biochar material, comprising the following steps:

[0006] (1) Weigh the cow dung solid waste biomass raw material and soak it in 0.08-0.12 mol·L -1 The K2FeO4 solution is placed in a beaker, and then the beaker is placed in a water bath at 60-70°C for heating and stirring for 2-6 hours for oxidation modification, and then the beaker is placed in an oven at 80-90°C for drying for 2 hours to obtain a K2FeO4 composite biomass material, so as to change the physical and chemical properties of the cow dung biomass material, so that Fe can be effectively loaded on the biochar in the form of oxides when it is subsequently modified with K2FeO4;

[0007] (2) The K2FeO4 composite biomass material is placed in a tube furnace and heated at 3-8℃·min in an oxygen-free or oxygen-limited environment. -1 The heating rate is increased to 600-800 °C and maintained for 1-3 h, and pyrolysis is performed to obtain K2FeO4 modified cow dung biochar material with a rich surface structure.

[0008] For the above-mentioned preparation method, preferably, the concentration of K2FeO4 solution in step (1) is 0.1 mol·L -1Preferably, in step (1), the beaker is placed in a water bath at 65°C and heated with stirring for 4 hours, and then the beaker is placed in an oven at 85°C for drying. In step (2), the oxygen-free or oxygen-limited environment is a nitrogen or argon atmosphere, and more preferably, the oxygen is heated in a nitrogen atmosphere at 5°C / min. -1 The heating rate is raised to 700° C. and maintained for 2 hours. The cow dung solid waste biomass raw material is the solid matter of cow dung that has been air-dried, sun-dried or baked.

[0009] As a preferred embodiment, a method for preparing an iron-modified cow dung biochar material of the present invention may include the following steps:

[0010] (1) Take the cow dung solid waste biomass raw material and soak it in 0.1 mol·L -1 The K2FeO4 solution was placed in a beaker, and then the beaker was placed in a 65°C water bath for heating and stirring for 4 hours, and then the beaker was placed in an oven at 85°C for drying to obtain a K2FeO4 composite biomass material;

[0011] (2) The K2FeO4 composite biomass material was placed in a tube furnace and heated at 5°C min in a nitrogen atmosphere. -1 The heating rate was raised to 700 °C and maintained for 2 h, then ground and crushed, and passed through a 100-mesh sieve to obtain K2FeO4 modified cow dung biochar material.

[0012] Secondly, the iron-modified cow dung biochar material obtained by the present invention has a rough surface and numerous microporous structures, and iron is loaded on the cow dung biochar in the form of oxides. The BET specific surface area of ​​the biochar was determined by surface area analysis based on the N2 adsorption method using a fully automatic multi-station gas adsorption analyzer. The surface of the unmodified cow dung biochar (CBC) is relatively smooth, with a specific surface area of ​​70-75m 2 ·g -1 , without obvious pore structure, while the surface of the iron-modified cow dung biochar material (FCBC) of the present invention is rougher, with a specific surface area of ​​55-60m 2 ·g -1 This is because the oxidation of biomass raw materials by K2FeO4 promotes the formation of pores. More microporous structures are generated on the surface of FCBC, which can increase the contact area between pollutants and biochar, which is beneficial to the removal of pollutants.

[0013] Third, the iron-modified cow dung biochar material obtained by the present invention can be used in Cd 2+ Elimination treatment is applied in the initial Cd 2+ Concentration: 150mg·L -1 In an environment with high concentrations of iron, the effects of cow dung biochar on Cd 2+ Adsorption capacity can reach 110-120mg·g -1 .

[0014] Table 1 Effect of relevant modified biochar on Cd 2+ Comparison of adsorption performance

[0015]

[0016] References:

[0017] 1. Tichem TM, Wang Y, Gameli RBH, et al. Multicomponent adsorption of pollutants from wastewater using low-cost eco-friendly iron-modified ricehusk biochar in the era of green chemistry [J]. Sustainability, 2023, 15(23).

[0018] 2. Ma Kaiyue, Zhang Hao, Song Ningning, et al. Study on the adsorption mechanism of cadmium by oxidative aged corn straw biochar[J]. Journal of Agro-Environment Science, 2022, 41(06): 1230-1240.

[0019] 3.Qiu Y, Zhang Q, Li M, et al. Adsorption of Cd(II) from aqueous solutions by modified biochars: comparison of modification methods[J]. Water Air and SoilPollution, 2019, 230(4).

[0020] 4.Zuo WQ,Chen C,Cui HJ,et al.Enhanced removal of Cd(II) from aqueoussolution using CaCO3 nanoparticle modified sewage sludge biochar[J].RscAdvances,2017,7(26):16238-16343.

[0021] 5.Li Z,Niu R,Yu J,et al.Removal of cadmium from aqueous solution bymagnetic biochar:adsorption characteristics and mechanism[J].EnvironmentalScience and Pollution Research,2024,31(4):6543-6547.

[0022] 6.Sun L, Gong P, Sun Y, et al. Modified chicken manure biochar enhanced the adsorption for Cd 2+ in aqueous and immobilization of Cd in contaminatedagricultural soil[J].Science of the Total Environment,2022,851.

[0023] 7.Tian H, Peng S, Zhao L, et al.Simultaneous adsorption of Cd(II)anddegradation of OTC by activated biochar with ferrate:Efficiency and mechanism[J].Journal of Hazardous Materials, 2023,447.

[0024] The K2FeO4 modified cow dung biochar material (FCBC) of the present invention has better Cd removal performance than the unmodified cow dung biochar (CBC). 2+ Elimination of treatment capacity, at the same time, compared with traditional modified or unmodified plant-derived biochar, it also has incomparable 2+ The present invention broadens the practical application scenarios of livestock and poultry manure waste, achieves the goals of harmless, reduced and resourceful manure, and can provide more optimal solutions for the prevention and control of water and soil pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the SEM image of biochar.

[0026] Figure 2 This is the FTIR spectrum of biochar.

[0027] Figure 3 Biochar adsorbs Cd 2+ XRD patterns before and after.

[0028] Figure 4 is the Langmuir adsorption isotherm curve. DETAILED DESCRIPTION

[0029] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0030] Example 1

[0031] Preparation of cow dung biochar: The cow dung solid waste biomass raw material (obtained from a farm in Lixin County, Bozhou City, Anhui Province) was dried and crushed at 85 °C, placed in a tubular furnace, and heated at 5 °C min in a nitrogen atmosphere. -1 The heating rate was raised to 700 °C and maintained for 2 h to obtain cow dung biochar (CBC).

[0032] Preparation of K2FeO4 modified biochar: 100 g of cow dung solid waste biomass raw material was weighed and immersed in 0.1 mol·L - 1 The K2FeO4 solution was placed in a beaker, and then the beaker was placed in a 65°C water bath for heating and stirring for 4 hours, and then the beaker was placed in an oven at 85°C for drying to obtain the K2FeO4 composite biomass material. After drying and crushing, it was placed in a tubular furnace and heated at 5°C·min- 1 The heating rate was raised to 700℃ and maintained for 2h to obtain K2FeO4 modified cow dung biochar (FCBC). The prepared biochar was ground and crushed, and passed through a 100-mesh sieve for later use.

[0033] Scanning electron microscopy was used to observe the surface morphology of biochar. Figure 1 .from Figure 1 SEM can be observed that the surface of CBC is relatively smooth and has no obvious pore structure, while the surface of FCBC is rougher. This is because the oxidation of biomass raw materials by K2FeO4 promotes the formation of pores. The surface of FCBC produces more microporous structures, which can increase the contact area between pollutants and biochar, which is conducive to the removal of pollutants.

[0034] Depend on Figure 2 Fourier transform infrared spectroscopy FTIR shows that biochar is at 3500 c m- 1 -OH stretching vibration peak appeared near 1030 cm - 1and 1102 cm - 1 The CO absorption peak appeared at 1625 cm - 1 and 1400 cm - 1 The -C=O stretching vibration peak appeared at 874-796cm- 1 There is a -CH aromatic structure nearby. K2FeO4 modified biochar FCBC has a 580cm- 1 A peak representing Fe-O appears at , indicating that Fe is effectively loaded on the biochar in the form of oxides.

[0035] The crystal phase was measured by X-ray diffractometer (XRD). Figure 3 The XRD spectrum shows that the characteristic peak of SiO2 is detected in CBC and the characteristic peak of CaCO3 is detected in FCBC. Biochar contains carbonate minerals. 2+ When the concentration reaches a certain level, Cd 2+ Will be with CO3 2 -The reaction generates a stable CdCO3 precipitate. Figure 2 It can be observed that upon adsorption of Cd 2+ Afterwards, the diffraction patterns of all biochars showed the characteristic peak of CdCO3.

[0036] Isothermal adsorption experiment

[0037] Weigh 20 mg of biochar sample into a 50 mL centrifuge tube, and add 20 mL of 0, 5, 10, 20, 50, 80, 100, 150, 200, and 300 mg·L- 1 CD 2+ Solution; shake at 25°C, 150 rpm for 24 h, filter, fix volume, measure solution concentration by ICP-MS, and calculate adsorption amount. Set up 3 parallels for each group.

[0038] The adsorption amount was calculated using the following formula:

[0039] Q e =(C0-C e )V / M,

[0040] Q e : The adsorption amount of biochar at adsorption equilibrium, (mg·g- 1 );C e : Cd in solution at adsorption equilibrium 2+ Concentration, (mg·L- 1 ); C0: Cd in solution 2+ Initial concentration, (mg·L- 1); V: solution volume, (L); M is the amount of biochar added, (g).

[0041] The adsorption data were fitted using the following Langmuir model formula:

[0042] Q e =Q m K L C e / (1+K L C e ),

[0043] Q e is the adsorption amount of biochar at adsorption equilibrium, (mg·g- 1 );C e Cd in solution at adsorption equilibrium 2+ Concentration, (mg·L- 1 );Q m is the theoretical maximum adsorption capacity, (mg·g- 1 );K L is the equilibrium constant, (L·mg- 1 ), which is related to the material's adsorption strength and affinity for metal ions.

[0044] Table 2 Parameters of isothermal adsorption Langmuir equation

[0045]

[0046] Depend on Figure 4 , Langmuir model fitting of CBC to Cd 2+ The maximum theoretical adsorption capacity is 25.127 mg·g -1 , while K2FeO4 modified biochar FCBC has a significant effect on Cd 2+ The maximum theoretical adsorption capacity is 112.633 mg·g -1 , which is 348.25% higher than the CBC of the corresponding original biochar, indicating that the physical and chemical properties of the biochar modified by K2FeO4 have been significantly improved, and the adsorption capacity has also been significantly improved.

[0047] It should be noted that the above-mentioned technical contents of the present invention are only for explanation and clarification to enable those skilled in the art to understand the technical essence of the present invention, so the technical contents are not used to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be subject to the claims. Those skilled in the art should know that any modification, equivalent substitution and improvement based on the substantial spirit of the present invention shall be within the substantial protection scope of the present invention.

Claims

1. A method for preparing iron-modified cow dung biochar material, comprising the following steps: (1) Take the cow dung solid waste biomass raw material and soak it in 0.08-0.12 mol·L -1 The K2FeO4 solution is placed in a beaker, and then the beaker is placed in a water bath at 60-70°C for heating and stirring for 2-6 hours, and then the beaker is placed in an oven at 80-90°C for drying to obtain a K2FeO4 composite biomass material; (2) The K2FeO4 composite biomass material is placed in a tube furnace and heated at 3-8℃·min in an oxygen-free or oxygen-limited environment. -1 The heating rate is increased to 600-800 °C and maintained for 1-3 h to obtain K2FeO4 modified cow dung biochar material.

2. The preparation method according to claim 1, characterized in that: Step (1) K2FeO4 solution concentration 0.1 mol·L -1 .

3. The preparation method according to claim 1, characterized in that: Step (1) Place the beaker in a 65°C water bath and heat and stir for 4 hours, then place the beaker in an 85°C oven to dry.

4. The preparation method according to claim 1, characterized in that: Step (2) is carried out in an oxygen-free or oxygen-limited environment at 5°C min -1 The heating rate is increased to 700° C. and maintained for 2 hours, and the oxygen-free or oxygen-limited environment is a nitrogen or argon atmosphere.

5. The preparation method according to claim 1, characterized in that: The steps include: (1) Take the cow dung solid waste biomass raw material and soak it in 0.1 mol·L -1 The K2FeO4 solution was placed in a beaker, and then the beaker was placed in a 65°C water bath for heating and stirring for 4 hours, and then the beaker was placed in an oven at 85°C for drying to obtain a K2FeO4 composite biomass material; (2) The K2FeO4 composite biomass material was placed in a tube furnace and heated at 5°C min in a nitrogen atmosphere. -1 The heating rate was raised to 700 °C and maintained for 2 h, then ground and crushed, and passed through a 100-mesh sieve to obtain K2FeO4 modified cow dung biochar material.

6. The iron-modified cow dung biochar material obtained by the preparation method according to any one of claims 1 to 5 has a rough surface and numerous microporous structures, and the iron is loaded on the cow dung biochar in the form of oxides, with a specific surface area of ​​55-60 m 2 ·g -1 .

7. The iron-modified cow dung biochar material according to claim 6 contains Cd 2+ The processing application is characterized in that At the initial Cd 2+ Concentration: 150mg·L -1 In an environment with high concentrations of iron, the effects of cow dung biochar on Cd 2+ Adsorption capacity is 110-120 mg g -1 .

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