Method for preparing heavy metal adsorbent through biomass charcoal modification and heavy metal adsorbent

Abstract

The invention provides a method for preparing a heavy metal adsorbent through biomass charcoal modification and a heavy metal adsorbent, and the method comprises the following steps: selecting a biomass charcoal raw material, crushing, screening the crushed biomass charcoal raw material, and drying the screened biomass charcoal raw material; preparing a modifier solution with the concentration of 0.5 mol / L to 1 mol / L, and uniformly stirring the modifier solution; mixing a modifier solution and the dried biomass charcoal raw material according to a preset mass ratio, uniformly stirring, and carrying out a modification reaction under preset reaction conditions; after the modification reaction, carrying out solid-liquid separation on a reaction mixture to obtain modified biomass charcoal and waste liquid; dehydrating and washing the modified biomass charcoal, and recovering the modifier in the modified biomass charcoal for recycling; and drying the washed and qualified modified biomass charcoal to obtain the heavy metal adsorbent. The method is efficient, energy-saving, environment-friendly and convenient to operate, the modification cost is reduced, and environmental pollution is reduced.

Description

Technical Field

[0001] This invention belongs to the field of heavy metal adsorbent preparation technology, specifically relating to a method for preparing heavy metal adsorbents by modifying biochar and the heavy metal adsorbent itself. Background Technology

[0002] With rapid industrial development, the discharge of heavy metal wastewater (such as wastewater containing heavy metal ions such as Cr, Pb, Cd, and Cu) has been increasing year by year. Heavy metal ions are characterized by high toxicity, difficulty in degradation, and easy accumulation. Once they enter water bodies and soil, they will seriously threaten the ecological environment and human health. Therefore, the treatment of heavy metal wastewater has become an important issue in the field of environmental protection.

[0003] Adsorption is a common method for treating heavy metal wastewater, offering advantages such as simple operation, high treatment efficiency, low cost, and no secondary pollution. The performance of the adsorbent directly determines the effectiveness of the adsorption treatment. Biochar, as a novel adsorbent material, is widely available, inexpensive, and environmentally compatible. However, unmodified biochar has a low number of surface functional groups and low adsorption capacity, resulting in limited adsorption effects on heavy metal ions and making it difficult to meet the requirements for advanced treatment of high-concentration heavy metal wastewater.

[0004] Physical, chemical, or biological modification methods can improve the surface structure of biochar, increase the number of surface functional groups, and enhance its adsorption capacity and selectivity for heavy metal ions. Among these, chemical modification has become the mainstream method for biochar modification due to its significant modification effect, convenient operation, and ease of large-scale application. However, existing biochar chemical modification technologies generally suffer from problems such as low modifier utilization, high energy consumption during the modification process, poor adsorption stability of modified biochar, and secondary pollution caused by modified wastewater, which limit their industrial application.

[0005] The technical solution disclosed in Chinese patent document CN114307957A, which prepares heavy metal ion adsorbents by modifying with dilute sulfuric acid combined with hydrothermal carbonization, can improve the adsorption performance of biochar to a certain extent, but still has the following shortcomings: First, the modification method is singular, only using dilute sulfuric acid immersion modification, which cannot fully activate the active sites on the surface of biochar. Moreover, dilute sulfuric acid can only dissolve some biochar elements, and its effect on improving the pore structure of biochar is limited, resulting in a low adsorption capacity of the prepared adsorbent, which is difficult to meet the needs of deep treatment of high-concentration heavy metal wastewater. Second, the process is cumbersome and energy-intensive, requiring dilute sulfuric acid modification, rinsing and drying, and then high-temperature hydrothermal carbonization at 240℃ for 2 hours. The high-temperature hydrothermal process has high energy consumption, and the multi-step drying process further increases energy consumption, which is not conducive to large-scale energy-saving production. Third, the utilization rate of the modifier is extremely low, with dilute sulfuric acid only used for... The process involves several key aspects: First, the biochar undergoes a single soaking modification without a recycling process. Large amounts of dilute sulfuric acid are discharged with the rinsing wastewater, increasing production costs and causing secondary pollution due to the acidic wastewater, resulting in poor environmental performance. Second, the rinsing and washing process is unreasonable. Only deionized water is used for rinsing until neutral, followed by sequential rinsing with hydrochloric acid solution and deionized water. This consumes a large amount of water resources and fails to completely remove residual dilute sulfuric acid and impurities from the biochar surface. The residual acidic substances affect the adsorption stability of the adsorbent and may even lead to secondary acidification of the water. Third, there is a lack of precise parameter control mechanisms. The precise parameter ranges for dilute sulfuric acid concentration, soaking time, and hydrothermal carbonization are not clearly defined. Parameter fluctuations easily lead to uneven adsorbent quality and poor adsorption stability. Fourth, the rinsing wastewater is not treated, and the acidic wastewater generated during the rinsing and washing process is directly discharged, further exacerbating environmental pollution and failing to meet environmentally friendly production requirements.

[0006] In summary, among the currently disclosed technical solutions for preparing heavy metal adsorbents by modifying biomass char, there is still room for improvement in terms of modification efficiency, modifier utilization rate, environmental friendliness, and product performance stability. Therefore, it is necessary to design a biomass char modification method and a heavy metal adsorbent that is efficient, energy-saving, environmentally friendly, and capable of preparing high-performance heavy metal adsorbents. Summary of the Invention

[0007] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a method for preparing heavy metal adsorbents by modifying biochar and a heavy metal adsorbent.

[0008] One aspect of the present invention provides a method for preparing a high-efficiency heavy metal adsorbent by modifying biochar, the method comprising: Select biochar raw materials, crush them, sieve the crushed biochar raw materials, and then dry the sieved biochar raw materials. Prepare a modifier solution with a concentration of 0.5 mol / L to 1 mol / L, and stir the modifier solution evenly; The modifier solution and the dried biochar raw material are mixed and stirred evenly according to a preset mass ratio, and the modification reaction is carried out under preset reaction conditions. After the modification reaction is completed, the reaction mixture is subjected to solid-liquid separation to obtain modified biochar and waste liquid; The modified biochar is dehydrated and washed to recover the modifiers for recycling. The washed and qualified modified biochar is dried to obtain a heavy metal adsorbent.

[0009] Optionally, the modifier solution may include a hydrochloric acid-ferric chloride mixed modifier or a sulfuric acid-zinc chloride mixed modifier.

[0010] Optionally, the modifier solution and the dried biochar raw material are mixed and stirred evenly according to a preset mass ratio, including: The modifier solution and the dried biochar raw material were mixed at a mass ratio of (3-5):1.

[0011] Optionally, mixing the modifier solution with the dried biochar raw material according to a preset mass ratio and stirring until homogeneous, further includes: The modifier solution and biochar raw material are stirred by a combination of ultrasonic vibration and mechanical stirring. The ultrasonic power is controlled at 250W~300W and the stirring speed is controlled at 60r / min~70r / min to ensure that the biochar and modifier are fully contacted and mixed evenly.

[0012] Optionally, the modification reaction is carried out under preset reaction conditions, including: A water bath temperature control method was used to control the reaction temperature at 50℃~60℃ with a temperature control accuracy of ±2℃. The pH value and temperature of the reaction system were monitored in real time, and the reaction time was controlled at 30 min~60 min for the modification reaction.

[0013] Optionally, the modified biochar may be dehydrated and washed to recover the modifiers for recycling, including: The modified biochar is subjected to pressure filtration and dehydration treatment, while the residual modifier in the modified biochar is squeezed out. The modified biochar after pressure filtration and dehydration is washed with deionized water until the pH value of the washing solution reaches 6.5~7.5. The washing wastewater is collected to recover the residual modifier.

[0014] Optionally, the washed and qualified modified biochar may be dried, including: The washed and qualified modified biochar was dried using a hot air circulation drying method, with the drying temperature controlled at 110℃ and the drying time at 35 minutes.

[0015] Optionally, biochar raw materials are selected, crushed, and then sieved, followed by drying; including: The biochar raw material is crushed to a particle size ≤0.1mm; The crushed biochar raw material is screened to remove impurities and materials with unqualified particle size; The screened biochar raw material is dried at a temperature of 100℃~110℃.

[0016] Optionally, after obtaining the heavy metal adsorbent, the method further includes: Quality testing is conducted on heavy metal adsorbents to ensure their effectiveness against Cr. 6+ Adsorption capacity ≥150mg / g, for Pb 2+ The adsorption capacity is ≥200mg / g.

[0017] Another aspect of the present invention provides a heavy metal adsorbent, which is prepared by the method for preparing a high-efficiency heavy metal adsorbent by modifying biochar as described above.

[0018] The present invention provides a method for preparing a high-efficiency heavy metal adsorbent by modifying biochar. This method is efficient, energy-saving, environmentally friendly and easy to operate. It improves the adsorption capacity and selectivity of biochar for heavy metal ions, reduces modification costs, reduces environmental pollution, meets the needs of deep treatment of heavy metal wastewater, and has important industrial application value and environmental benefits.

[0019] The heavy metal adsorbent prepared by the method for preparing high-efficiency heavy metal adsorbents by modifying biochar provided in this invention has a high efficiency for Cr. 6+ Pb 2+ The adsorption capacity of heavy metal ions is significantly improved, the adsorption selectivity is strong, and the adsorption stability is good, which can meet the requirements of deep treatment of high-concentration heavy metal wastewater. Compared with the existing technology, the modification reaction time is shortened by 70%-80%, the modification efficiency is significantly improved, and the energy consumption per unit product is reduced by more than 40%. Attached Figure Description

[0020] Figure 1 This is a schematic flowchart of a method for preparing a high-efficiency heavy metal adsorbent by modifying biochar according to an embodiment of the present invention. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] This invention addresses the problems of low modification efficiency, low modifier utilization, environmental pollution from modified wastewater, poor adsorption stability of products, and high energy consumption in existing biochar modification technologies. It designs a highly efficient, energy-saving, environmentally friendly, and easy-to-operate method for preparing high-efficiency heavy metal adsorbents by modifying biochar, thereby improving the adsorption capacity and selectivity of biochar for heavy metal ions, reducing modification costs, minimizing environmental pollution, and meeting the needs of deep treatment of heavy metal wastewater.

[0023] like Figure 1 As shown, the present invention provides a method S100 for preparing a high-efficiency heavy metal adsorbent by modifying biochar, the method comprising: S110. Select biochar raw materials, crush them, and then screen the crushed biochar raw materials. After that, dry the screened biochar raw materials.

[0024] Specifically, biochar raw materials are selected and first crushed to a particle size ≤0.1mm to increase the specific surface area of ​​the biochar and improve the subsequent modification effect. The crushed biochar raw materials are then sieved with a sieve efficiency ≥99% to remove impurities and materials with unqualified particle sizes. The sieved biochar raw materials are then dried at a controlled temperature of 100℃~110℃ until the moisture content is ≤5% to avoid moisture affecting the modification reaction effect.

[0025] In this embodiment, the biochar raw material is precisely pretreated by pulverizing, sieving, and drying to ensure that the biochar particle size is uniform and the moisture content meets the standard, thereby improving the modification effect.

[0026] S120. Prepare a modifier solution with a concentration of 0.5 mol / L to 1 mol / L, and stir the modifier solution evenly.

[0027] Specifically, depending on the modification requirements, a modifier solution with a concentration of 0.5 mol / L to 1 mol / L is prepared. This modifier solution can be a hydrochloric acid-ferric chloride mixture or a sulfuric acid-zinc chloride mixture, etc. The prepared modifier solution is stirred until the modifier is completely dissolved, ensuring a uniform modifier concentration.

[0028] S130. Mix the modifier solution with the dried biochar raw material according to the preset mass ratio and stir evenly, and carry out the modification reaction under the preset reaction conditions.

[0029] Specifically, the modifier solution and dried biochar raw material are mixed at a mass ratio of (3-5):1 to avoid waste of the modifier and improve its utilization rate. The modifier solution and biochar raw material are stirred using a combination of ultrasonic vibration and mechanical stirring. The ultrasonic power is controlled at 250W~300W and the stirring speed at 60r / min~70r / min to ensure sufficient contact and uniform mixing between the biochar and the modifier. Preferably, the ultrasonic power is controlled at 250W and the stirring speed at 60r / min. A water bath temperature control method is used to control the reaction temperature at 50℃~60℃ with a temperature control accuracy of ±2℃. The pH value and temperature of the reaction system are monitored in real time, and the reaction time is controlled at 30 min~60 min to promote rapid and complete modification reaction.

[0030] In this embodiment, the synergistic effect of ultrasonic stirring and mechanical stirring ensures uniform mixing of biochar and modifier, stable modification effect, and good product quality consistency. Combined with precise temperature and pH control mechanisms, the modification reaction is carried out quickly and fully, improving modification efficiency and product stability.

[0031] S140. After the modification reaction is completed, the reaction mixture is subjected to solid-liquid separation to obtain modified biochar and waste liquid.

[0032] Specifically, after the modification reaction is completed, the reaction mixture is subjected to solid-liquid separation to obtain modified biochar and waste liquid.

[0033] S150. The modified biochar is dehydrated and washed to recover the modifier from the modified biochar for recycling.

[0034] Specifically, the modified biochar obtained from solid-liquid separation is subjected to pressure filtration dehydration to reduce the water content of the solid product (≤30%), while simultaneously squeezing out the residual modifier from the modified biochar and recycling it in the modifier preparation stage. The modified biochar after pressure filtration dehydration is washed with deionized water until the pH value of the washing liquid reaches 6.5~7.5; the washing wastewater is collected and regenerated to recover the modifier, which is then recycled for the modification reaction, ensuring a modifier recovery rate of ≥85%; the purified washing wastewater can be recycled for subsequent washing stages, ensuring a water resource utilization rate of ≥90%, reducing water resource consumption and environmental pollution.

[0035] In this embodiment, the residual modifier recovery method combining solid-liquid separation and pressure filtration, combined with the regeneration treatment of washing wastewater, realizes the recycling of modifier and water resources, reduces costs and environmental pollution.

[0036] S160. The washed and qualified modified biochar is dried to obtain a heavy metal adsorbent.

[0037] Specifically, the washed and qualified modified biochar is dried using a hot air circulation method, with the drying temperature controlled at 110℃ and the drying time at 35min, until the solid product is dried to a moisture content of ≤5%, thus obtaining dried modified biochar (heavy metal adsorbent); waste heat is recovered by utilizing hot air circulation, with a waste heat utilization rate of ≥70%, reducing drying energy consumption.

[0038] The method further includes, after obtaining the heavy metal adsorbent: The dried modified biochar was subjected to quality testing to ensure its Cr content was within acceptable limits. 6+ Adsorption capacity ≥150mg / g, for Pb 2+ The adsorption capacity is ≥200mg / g, which meets the requirements of high-efficiency heavy metal adsorbents; qualified products are collected and stored, and unqualified products are returned to the modification reaction stage for re-modification.

[0039] In addition, the method for preparing high-efficiency heavy metal adsorbents by modifying biomass char in this invention adopts industrial-grade PLC automated control throughout the entire process. It can display and control the key parameters of each step, such as biomass char pretreatment, modifier preparation, modification reaction, solid-liquid separation, washing and recovery, and drying, in real time. It has functions such as parameter setting, fault alarm, data storage (≥5 years), and remote control. The modification parameters can be flexibly adjusted according to the target adsorption performance to ensure stable product quality.

[0040] In this embodiment, an automated control method for preparing metal adsorbents is adopted. This method is convenient to operate, can achieve fully automated operation, and is suitable for large-scale industrial applications. It is of great significance for promoting the development of heavy metal wastewater treatment technology.

[0041] The method for preparing high-efficiency heavy metal adsorbents by modifying biochar provided by this invention has a modifier recovery rate of ≥85% and a water resource utilization rate of ≥90%, which effectively reduces the modification cost and environmental pollution. It is easy to operate, has high modification efficiency, low cost, and good environmental performance, effectively solving the problems existing in the prior art. The prepared high-efficiency heavy metal adsorbent has excellent performance and has important industrial application value and environmental benefits.

[0042] Another aspect of the present invention provides a heavy metal adsorbent, which is prepared using the method S100 described above for preparing a high-efficiency heavy metal adsorbent by modifying biochar. The specific process of this method S100 for preparing a high-efficiency heavy metal adsorbent by modifying biochar has been described in detail above and will not be repeated here.

[0043] The heavy metal adsorbent prepared by the method for preparing high-efficiency heavy metal adsorbents by modifying biochar provided in this invention has a high efficiency for Cr. 6+ Pb 2+The adsorption capacity of heavy metal ions is significantly improved, the adsorption selectivity is strong, and the adsorption stability is good, which can meet the requirements of deep treatment of high-concentration heavy metal wastewater. Compared with the existing technology, the modification reaction time is shortened by 70%-80%, the modification efficiency is significantly improved, and the energy consumption per unit product is reduced by more than 40%.

[0044] Example 1 This embodiment provides a method for preparing heavy metal adsorbents by modifying biochar, specifically using coconut shell biochar as raw material. First, the coconut shell biochar raw material is pulverized to a particle size ≤0.1mm, sieved to remove impurities and non-compliant particles, and then dried at 105℃. A 0.5mol / L hydrochloric acid-ferric chloride mixed modifier solution is prepared and stirred evenly. The modifier solution is mixed with the dried biochar raw material at a mass ratio of 4:1, and stirred using a combination of ultrasonic vibration and mechanical stirring, controlling the ultrasonic power at 280W and the stirring speed at 65r / min until uniform mixing. A water bath temperature control method is used, controlling the reaction temperature at 55℃ with a temperature control accuracy of ±2℃, and the pH and temperature of the reaction system are monitored in real time. The reaction time is controlled at 45min for the modification reaction. After the modification reaction is completed, the reaction mixture is separated into solid and liquid phases to obtain modified biochar and waste liquid. The modified biochar was subjected to pressure filtration dehydration, simultaneously squeezing out the residual modifier. It was then washed with deionized water until the pH of the washing solution reached 6.5-7.5, and the residual modifier was recovered from the washing wastewater. The washed modified biochar was then dried using a hot air circulation drying method, controlling the drying temperature at 110℃ and the drying time at 35 minutes to obtain a heavy metal adsorbent. Testing showed that the heavy metal adsorbent obtained in this embodiment effectively adsorbed Cr... 6+ The adsorption capacity is 156 mg / g for Pb² + The adsorption capacity is 208 mg / g.

[0045] Example 2 The difference between this embodiment and Example 1 is that the concentration of the modifier solution is adjusted to 1.0 mol / L, while the other steps and parameters are exactly the same as in Example 1. Specifically, coconut shell biochar is used as raw material, crushed to a particle size ≤0.1 mm, sieved, and dried at 105℃. A 1.0 mol / L hydrochloric acid-ferric chloride mixed modifier solution is prepared and mixed with the dried biochar at a mass ratio of 4:1. The mixture is then stirred evenly under ultrasonic power of 280W and stirring speed of 65 r / min. The reaction is carried out in a 55℃ water bath for 45 min. After the reaction, the mixture is subjected to solid-liquid separation, pressure filtration for dehydration, washing with deionized water to a pH value of 6.5~7.5, and finally dried at 110℃ for 35 min to obtain the heavy metal adsorbent. Compared with Example 1, this embodiment only increases the modifier concentration from 0.5 mol / L to 1.0 mol / L, while keeping all other parameters unchanged. The heavy metal adsorbent obtained in this embodiment shows that it is effective against Cr. 6+ The adsorption capacity is 203 mg / g, for Pb² + The adsorption capacity was 267 mg / g. The results indicate that increasing the modifier concentration significantly increases the number of active sites on the biochar surface, thereby increasing the adsorption capacity of Cr. 6+ and Pb² + The adsorption capacities were increased by approximately 30% and 28%, respectively.

[0046] Example 3 The difference between this embodiment and Example 1 is that the reaction temperature is adjusted to 60℃, while the remaining steps and parameters are exactly the same as in Example 1. Specifically, coconut shell biochar is used as raw material, crushed to a particle size ≤0.1mm, sieved, and dried at 105℃. A 0.5mol / L hydrochloric acid-ferric chloride mixed modifier solution is prepared and mixed with the dried biochar at a mass ratio of 4:1, and mixed evenly under ultrasonic power of 280W and stirring speed of 65r / min. A water bath temperature control method is used to control the reaction temperature at 60℃ with a temperature control accuracy of ±2℃, and the reaction time is 45min. Subsequent solid-liquid separation, pressure filtration dehydration, washing, drying, and other steps are the same as in Example 1. Compared with Example 1, this embodiment only increases the reaction temperature from 55℃ to 60℃, while all other parameters remain unchanged. Testing showed that the heavy metal adsorbent obtained in this embodiment effectively adsorbs Cr... 6+ The adsorption capacity is 172 mg / g for Pb² + The adsorption capacity was 226 mg / g. The results indicate that appropriately increasing the reaction temperature is beneficial to the chemical bonding reaction between the modifier and biochar, allowing Cr... 6+ and Pb² + The adsorption capacity was increased by approximately 10% and 9%, respectively.

[0047] Example 4 The difference between this embodiment and Example 1 is that the reaction time is adjusted to 30 minutes, while the remaining steps and parameters are exactly the same as in Example 1. Specifically, coconut shell biochar is used as raw material, crushed to a particle size ≤0.1 mm, sieved, and dried at 105°C. A 0.5 mol / L hydrochloric acid-ferric chloride mixed modifier solution is prepared and mixed with the dried biochar at a mass ratio of 4:1. The mixture is then stirred evenly under ultrasonic power of 280 W and stirring speed of 65 r / min. The reaction is carried out in a 55°C water bath for 30 minutes. Subsequent solid-liquid separation, pressure filtration dehydration, washing, and drying steps are the same as in Example 1. Compared with Example 1, this embodiment only shortens the reaction time from 45 minutes to 30 minutes, while all other parameters remain unchanged. Testing showed that the heavy metal adsorbent obtained in this embodiment effectively adsorbs Cr... 6+ The adsorption capacity is 141 mg / g for Pb² + The adsorption capacity was 186 mg / g. The results indicate that insufficient reaction time leads to incomplete modification, and Cr... 6+ and Pb² + The adsorption capacity decreased by approximately 10% and 11% compared to Example 1, respectively, indicating that a reaction time of 45 min is more conducive to a complete reaction.

[0048] Example 5 The difference between this embodiment and Example 1 is that the mass ratio of the modifier solution to the biochar raw material is adjusted to 3:1, while the remaining steps and parameters are exactly the same as in Example 1. Specifically, coconut shell biochar is used as the raw material, crushed to a particle size ≤0.1mm, sieved, and dried at 105℃. A 0.5mol / L hydrochloric acid-ferric chloride mixed modifier solution is prepared and mixed with the dried biochar at a mass ratio of 3:1. The mixture is then stirred evenly under ultrasonic power of 280W and stirring speed of 65r / min. The reaction is carried out in a 55℃ water bath for 45min. Subsequent solid-liquid separation, pressure filtration dehydration, washing, and drying steps are the same as in Example 1. Compared with Example 1, this embodiment only reduces the mass ratio of the modifier to the raw material from 4:1 to 3:1, while all other parameters remain unchanged. Testing showed that the heavy metal adsorbent obtained in this embodiment effectively adsorbs Cr... 6+ The adsorption capacity is 148 mg / g for Pb² + The adsorption capacity was 197 mg / g. The results showed that reducing the amount of modifier led to insufficient contact between the modifier and the biochar, resulting in Cr... 6+ and Pb² + The adsorption capacity decreased by approximately 5% and 5% respectively compared to Example 1, indicating that a mass ratio of 4:1 is more conducive to obtaining an adsorbent with high adsorption performance.

[0049] Example 6 The difference between this embodiment and Example 1 is that the modifier solution is replaced with a sulfuric acid-zinc chloride mixed modifier at a concentration of 0.5 mol / L. The remaining steps and parameters are exactly the same as in Example 1. Specifically, coconut shell biochar is used as raw material, pulverized to a particle size ≤0.1 mm, sieved, and dried at 105℃. A 0.5 mol / L sulfuric acid-zinc chloride mixed modifier solution is prepared and mixed with the dried biochar at a mass ratio of 4:1. The mixture is then stirred evenly at an ultrasonic power of 280 W and a stirring speed of 65 r / min. The reaction is carried out in a 55℃ water bath for 45 min. Subsequent solid-liquid separation, pressure filtration dehydration, washing, and drying steps are the same as in Example 1. Compared with Example 1, this embodiment only changes the modifier type from hydrochloric acid-ferric chloride to sulfuric acid-zinc chloride; all other parameters remain unchanged. Testing showed that the heavy metal adsorbent obtained in this embodiment effectively adsorbs Cr... 6+ The adsorption capacity is 165 mg / g for Pb² + The adsorption capacity was 219 mg / g. The results indicate that the sulfuric acid-zinc chloride modifier has a strong adsorption capacity for Cr. 6+ The adsorption performance of both is slightly better than that of hydrochloric acid-ferric chloride, and both have good adsorption properties for Pb²⁺. + The adsorption performance is basically the same, and the appropriate modifier can be selected according to the type of target heavy metal pollutant.

[0050] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing heavy metal adsorbents by modifying biochar, characterized in that, The method includes: Select biochar raw materials, crush them, sieve the crushed biochar raw materials, and then dry the sieved biochar raw materials. Prepare a modifier solution with a concentration of 0.5 mol / L to 1 mol / L, and stir the modifier solution evenly; The modifier solution and the dried biochar raw material are mixed and stirred evenly according to a preset mass ratio, and the modification reaction is carried out under preset reaction conditions. After the modification reaction is completed, the reaction mixture is subjected to solid-liquid separation to obtain modified biochar and waste liquid; The modified biochar is dehydrated and washed to recover the modifiers for recycling. The washed and qualified modified biochar is dried to obtain a heavy metal adsorbent.

2. The method according to claim 1, characterized in that, The modifier solution includes a hydrochloric acid-ferric chloride mixed modifier or a sulfuric acid-zinc chloride mixed modifier.

3. The method according to claim 1, characterized in that, The modifier solution and the dried biochar raw material are mixed and stirred evenly according to a preset mass ratio, including: The modifier solution and the dried biochar raw material were mixed at a mass ratio of (3-5):

1.

4. The method according to claim 1, characterized in that, The process of mixing the modifier solution with the dried biochar raw material according to a preset mass ratio and stirring until homogeneous also includes: The modifier solution and biochar raw material are stirred by a combination of ultrasonic vibration and mechanical stirring. The ultrasonic power is controlled at 250W~300W and the stirring speed is controlled at 60r / min~70r / min to ensure that the biochar and modifier are fully contacted and mixed evenly.

5. The method according to claim 1, characterized in that, The modification reaction is carried out under preset reaction conditions, including: A water bath temperature control method was used to control the reaction temperature at 50℃~60℃ with a temperature control accuracy of ±2℃. The pH value and temperature of the reaction system were monitored in real time, and the reaction time was controlled at 30 min~60 min for the modification reaction.

6. The method according to claim 1, characterized in that, The modified biochar is dehydrated and washed, and the modifiers in the modified biochar are recovered for recycling, including: The modified biochar is subjected to pressure filtration and dehydration treatment, while the residual modifier in the modified biochar is squeezed out. The modified biochar after pressure filtration and dehydration is washed with deionized water until the pH value of the washing solution reaches 6.5~7.

5. The washing wastewater is collected to recover the residual modifier.

7. The method according to claim 1, characterized in that, The modified biochar that has passed washing is then dried, including: The washed and qualified modified biochar was dried using a hot air circulation drying method, with the drying temperature controlled at 110℃ and the drying time at 35 minutes.

8. The method according to claim 1, characterized in that, The process involves selecting biochar raw materials, crushing them, sieving the crushed biochar raw materials, and then drying the sieved biochar raw materials; including: The biochar raw material is crushed to a particle size ≤0.1mm; The crushed biochar raw material is screened to remove impurities and materials with unqualified particle size; The screened biochar raw material is dried at a temperature of 100℃~110℃.

9. The method according to claim 1, characterized in that, After obtaining the heavy metal adsorbent, the method further includes: Quality testing is conducted on heavy metal adsorbents to ensure their effectiveness against Cr. 6+ Adsorption capacity ≥150mg / g, for Pb 2+ The adsorption capacity is ≥200mg / g.

10. A heavy metal adsorbent, characterized in that, The high-efficiency heavy metal adsorbent is prepared by the method for modifying biochar according to any one of claims 1 to 9.

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