Bio-based adsorbent for removing microcystin-LR in water and application of bio-based adsorbent
By steam explosion and NaOH-STMP modification of rice husks, a highly efficient bio-based adsorbent was prepared, which solved the problem of removing microcystin-LR from water and realized efficient and environmentally friendly resource reuse and removal of microcystin-LR in complex environments.
Patent Information
- Application Number
- CN202510860115.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-25
- Publication Date
- 2025-10-21
AI Technical Summary
Existing technologies are insufficient for the efficient removal of microcystin-LR from water, especially in complex environments during harmful algal blooms, and traditional methods result in resource waste and environmental impact.
Using rice husks as raw material, a bio-based adsorbent was prepared through steam explosion and chemical modification, including the combined modification with NaOH and STMP, to improve the adsorption performance of rice husk powder for efficient removal of microcystin-LR.
It significantly improves the adsorption capacity of rice husk powder, achieving a removal rate of 99.32% in a short time. It also maintains high efficiency in the presence of coexisting ions and natural organic matter, and still has a good removal effect after five cycles, realizing the resource utilization of agricultural waste.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention, belonging to the field of food technology, relates to a biosorbent and its preparation method, particularly a bio-based sorbent capable of removing microcystin-LR from water and its application. This biosorbent can efficiently remove microcystin-LR from water environments and exhibits good adsorption capacity within the pH range of microalgae culture media. Background Art
[0002] Microalgae are rich in protein, polyunsaturated fatty acids, vitamins, and bioactive substances. Driven by the concept of "big food," they are entering the market as a new food product. However, during the cultivation of microalgae, harmful algal blooms are unavoidable. Due to the impacts of eutrophication and climate change, algal blooms are becoming increasingly frequent. Specifically, harmful cyanobacteria proliferate during blooms and release highly toxic microcystins, posing a threat to microalgae-based foods. To date, over 300 microcystin variants have been identified, with microcystin-LR (MC-LR) being one of the most prevalent and dangerous. Exposure to MC-LR can cause severe liver damage, promote tumor growth, and, in extreme cases, lead to death. MC-LR's heptapeptide structure is highly stable, allowing it to survive in aquatic environments for at least 17 days and remain stable for months or even years under low temperatures and darkness. Therefore, the risk of humans and other organisms ingesting MC-LR from water sources or microalgae is steadily increasing. Human exposure to MC-LR can also occur through the food chain, posing serious public health and safety concerns. Therefore, urgent action is needed to develop effective methods to remove MC-LR from contaminated water sources.
[0003] Currently, there is growing interest in developing sustainable and environmentally friendly removal methods. One promising approach is to use agricultural waste products, such as rice husks, as low-cost adsorbents for water purification. Rice husks are a by-product of rice processing, with approximately 120 million tons produced worldwide each year. Millions of tons of rice husks are discarded or incinerated after harvest each year, resulting in carbon emissions and resource waste. Through resource utilization, especially material utilization, they can be converted into valuable materials and reduce environmental impact. Rice husks are rich in cellulose, hemicellulose, and lignin, and have structural properties suitable for adsorption applications. Therefore, using this type of biosorbent to remove microcystin-LR from water is a good way to reuse it.
[0004] The present invention studies the method and conditions for optimizing the adsorption performance of rice husk powder through physical and chemical modification. The obtained bio-based adsorbent can efficiently remove microcystin-LR from water, and has high adsorption performance for microcystin-LR water in the presence of anions and natural organic matter, thereby realizing waste value, reducing resource waste caused by biological waste and the carbon footprint of traditional rice husk processing.
[0005] Through searching, no patent publication documents related to the patent application of the present invention have been found. Summary of the Invention
[0006] The purpose of the present invention is to overcome the shortcomings of the existing technology and, based on the existing technology, provide a bio-based adsorbent and its application that can remove microcystin-LR from water and complex environments. The bio-adsorbent can efficiently remove microcystin-LR from water, making it widely used in environmental protection work such as harmful algal bloom treatment.
[0007] The technical solution adopted by the present invention to solve its technical problem is:
[0008] A bio-based adsorbent for removing microcystin-LR from wastewater, the preparation method of which comprises the following steps:
[0009] (1) soaking rice husks with water, then performing steam explosion treatment, then drying the steam-exploded rice husks, grinding the dried rice husks into rice husk powder and sieving to obtain steam-exploded modified rice husk powder;
[0010] (2) The steam-exploded modified rice husk powder was chemically modified with NaOH and STMP (sodium trimetaphosphate) to obtain physically and chemically modified rice husk powder;
[0011] In step (1), the prepared rice husks are soaked in distilled water at a material-liquid ratio of 1:1-4 for 0.5-2 hours, filtered, and then placed in a steam explosion tank for steam explosion. Preferably, the prepared rice husks are soaked in distilled water at a material-liquid ratio of 1:2 for 1 hour.
[0012] The sieve was passed through a 0.25 mm sieve.
[0013] The steam explosion pressure is 0.5-2 MPa, and the steam explosion time is 5-20 min. Preferably, the steam explosion pressure is 1.0 MPa, and the steam explosion time is 10 min.
[0014] After the steam explosion, the resulting rice husks are dried at 50-70°C for 15-30 hours. Preferably, the rice husks are dried at 60°C for 24 hours. The dried rice husks are then ground into rice husk powder in an oscillating mill and passed through a 0.25 mm sieve. The resulting material is steam-exploded modified rice husk powder.
[0015] The amount of rice husk used during steam explosion is two-thirds of the volume of the steam explosion tank (5L).
[0016] In step (2), after modification, the residual reagent is removed by washing with water and then dried. The steam-exploded modified rice husk powder obtained in step (1) is chemically modified with 2-8% NaOH and 20-40% STMP, and the steam-exploded modified rice husk powder is added to the mixed solution at a material-liquid ratio of 1:30-50, and stirred at 400-1000 rpm at a constant temperature of 30-40°C for 1-4 hours. Preferably, the steam-exploded modified rice husk powder obtained in step (1) is chemically modified with 5% NaOH and 33.25% STMP. Preferably, the steam-exploded modified rice husk powder is added to the mixed solution at a material-liquid ratio of 1:40, and stirred at 500 rpm at a constant temperature of 35°C for 2 hours.
[0017] Subsequently, the residual reagents were removed by washing with distilled water and anhydrous ethanol and the pH was adjusted to neutral, and then filtered. Finally, the mixture was dried at 60°C for 24 hours. The obtained material was the rice husk powder modified by steam explosion, NaOH and STMP.
[0018] The application of the bio-based adsorbent in removing microcystin-LR from water is in a ratio of 1:10 between feed and liquid. The advantages and positive effects achieved by the present invention are as follows:
[0019] 1. The present invention creatively uses agricultural waste rice husks as the raw material for the adsorption of microcystin-LR, thereby achieving effective utilization of agricultural by-products.
[0020] 2. To improve the adsorption performance of rice husks, the modified rice husks were modified to exhibit a significant improvement in adsorption capacity. With an initial concentration of 100 μg / L for the simulated microcystin-LR wastewater, the removal rate of the modified rice husk powder, combined with steam explosion, NaOH, and STMP, increased from 0 to 99.32% over time from 0 to 10 minutes. Adsorption saturation was achieved in 10 minutes, indicating that the original rice husk powder, after a series of modifications, can effectively remove microcystin-LR from water environments in a short period of time. Compared to the original rice husks and steam-exploded rice husks, the adsorption capacity was significantly improved, achieving unexpected technical results.
[0021] 3. The modified rice husk powder of the present invention has a good removal effect of microcystin-LR in the presence of coexisting ions and natural organic matter, achieving unexpected technical effects.
[0022] 4. The modified rice husk powder of the present invention has a good removal effect of microcystin-LR after five cycles of regeneration, achieving unexpected technical effects.
[0023] 5. The raw materials of the rice husk-based biosorbent of the present invention are widely available and inexpensive, and can also provide a method for utilizing agricultural by-products on a practical basis.
[0024] 6. The modification method of the present invention is simple, green, suitable for large-scale production, and has obvious treatment effect. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 Figure 2 shows the adsorption capacity of microcystin-LR by different adsorbents.
[0026] Figure 2 This is a graph showing the effect of different pH values on the removal rate of microcystin-LR by different adsorbents in the present invention;
[0027] Figure 3 This is a graph showing the effect of different adsorption times on the removal rate of microcystin-LR by different adsorbents in the present invention;
[0028] Figure 4 This is a graph showing the effect of different initial concentrations of microcystin-LR on the removal rate of microcystin-LR by different adsorbents in the present invention;
[0029] Figure 5 The first-order kinetic fitting of microcystin-LR removal by different adsorbents in the present invention is shown;
[0030] Figure 6 This is a diagram showing the effect of different concentrations of coexisting ions on the removal rate of microcystin-LR by the modified adsorbent in the present invention;
[0031] Figure 7 This is an effect diagram of the removal rate of microcystin-LR after five cycles of the modified adsorbent in the present invention; DETAILED DESCRIPTION
[0032] The present invention will be further described below with reference to the following examples. The following examples are illustrative rather than restrictive, and the scope of protection of the present invention cannot be limited by the following examples.
[0033] Unless otherwise specified, the raw materials used in the present invention are conventional commercial products; the methods used in the present invention are conventional methods in the art unless otherwise specified.
[0034] Example 1
[0035] A bio-based adsorbent capable of removing microcystin-LR from water, the preparation method of which comprises the following steps:
[0036] (1) The prepared rice husks were soaked in tap water at a material-liquid ratio of 1:1 for 1 hour, wherein the amount of rice husks was half of the volume of the steam explosion tank (5L). The soaked rice husks were filtered and placed in the steam explosion tank for steam explosion. The steam explosion test conditions were a steam explosion pressure of 1.0 MPa and a steam explosion time of 10 min. After the steam explosion treatment, the obtained rice husks were dried at 50°C for 24 hours. The dried rice husks were then placed in an oscillating mill and ground into rice husk powder and passed through a 0.25 mm sieve. The obtained material was the steam explosion modified rice husk powder.
[0037] (2) The steam-exploded modified rice husk powder was chemically modified with 5% NaOH and 33.25% STMP. A mixed solution of 5% NaOH and 33.25% STMP was prepared, and the steam-exploded modified rice husk powder was added to the mixed solution at a solid-liquid ratio of 1:40. The mixture was stirred at 500 rpm for 2 hours at a constant temperature of 35°C. The mixture was then washed with distilled water and anhydrous ethanol to remove residual reagents and adjust the pH to neutral. The mixture was then filtered and dried at 60°C for 24 hours. The resulting material was the steam-exploded, NaOH, and STMP-modified rice husk powder.
[0038] Comparative Example 1
[0039] A bio-based adsorbent capable of removing microcystin-LR from wastewater, the preparation method of which comprises the following steps:
[0040] Rice husk was used as raw material, washed with distilled water, then ground into rice husk powder using an oscillating mill and passed through a 0.25 mm sieve. The obtained material was the original rice husk powder.
[0041] Comparative Example 2
[0042] A bio-based adsorbent capable of removing microcystin-LR from wastewater is prepared by soaking prepared rice husks in tap water at a solid-liquid ratio of 1:1 for 1 hour. The amount of rice husks is half the volume of a 5L steam explosion tank. The soaked rice husks are filtered and then placed in a steam explosion tank for steam explosion. The steam explosion test conditions are a steam explosion pressure of 1.0 MPa and a steam explosion time of 10 minutes. After steam explosion, the resulting rice husks are dried at 50°C for 24 hours. The dried rice husks are then ground into rice husk powder in an oscillating mill and passed through a 0.25mm sieve. The resulting material is steam-exploded modified rice husk powder.
[0043] Comparative Example 3
[0044] A bio-based adsorbent capable of removing microcystin-LR from water, the preparation method of which comprises the following steps:
[0045] (1) The prepared rice husks were soaked in tap water at a material-liquid ratio of 1:1 for 1 hour, wherein the amount of rice husks was half of the volume of the steam explosion tank (5L). The soaked rice husks were filtered and placed in the steam explosion tank for steam explosion. The steam explosion test conditions were a steam explosion pressure of 1.0 MPa and a steam explosion time of 10 min. After the steam explosion treatment, the obtained rice husks were dried at 50°C for 24 hours. The dried rice husks were then placed in an oscillating mill and ground into rice husk powder and passed through a 0.25 mm sieve. The obtained material was the steam explosion modified rice husk powder.
[0046] (2) The steam-exploded modified rice husk powder was chemically modified with 5% NaOH. A 5% NaOH mixed solution was prepared. The steam-exploded modified rice husk powder was added to the mixed solution at a solid-liquid ratio of 1:40. The mixture was stirred at 500 rpm for 2 h at a constant temperature of 35°C. The mixture was then washed with distilled water and anhydrous ethanol to remove any residual reagents and adjust the pH to neutral. The mixture was then filtered and dried at 60°C for 24 h. The resulting material was steam-exploded, NaOH-modified rice husk powder.
[0047] The effects of the bio-based adsorbents of Example 1 and Comparative Examples 1 and 2 on removing microcystin-LR were tested.
[0048] 1. The adsorption capacity of three bio-based adsorbents for microcystin-LR was compared when the adsorbent dosage was 0.005g. The initial concentration of microcystin-LR was 600μg / L and the adsorption time was 60min.
[0049] 2. The effect of pH on the adsorption rate of microcystin-LR by the adsorbent was studied in the pH range of 3-7 (3, 5, 6, 7). 0.005 g of modified rice husk powder was added to a container containing 10 mL of simulated waste liquid with an initial concentration of 100 μg / L of microcystin-LR, and then shaken at room temperature for 60 minutes to reach adsorption equilibrium. The concentration of the supernatant after adsorption was then measured at 238 nm using a high-performance liquid chromatography-ultraviolet detector to obtain the microcystin-LR content in the adsorbed solution.
[0050] 3. The selected adsorption time is 5-60min (5, 10, 20, 30, 45, 60min). At different time intervals, the modified rice husk powder was used to conduct a batch adsorption experiment on the adsorption rate of microcystin-LR in 10mL of waste liquid with an initial concentration of 100μg / L microcystin-LR. The amount of adsorbent was 0.005g, and then it was shaken at room temperature for 60min to reach adsorption equilibrium. The concentration of the supernatant after adsorption was measured at 238nm by high performance liquid chromatography-ultraviolet detector to obtain the content of microcystin-LR in the solution after adsorption;
[0051] 4. The effect of the initial concentration of microcystin-LR on the adsorption rate of the adsorbent was studied within a concentration range of 50-400 μg / L (50, 100, 200, 300, 400 μg / L). 10 mL of simulated wastewater containing microcystin-LR of varying concentrations was added to each container, along with 0.005 g of adsorbent. The mixture was shaken at room temperature for 60 minutes to reach equilibrium. The concentration of the supernatant after adsorption was measured using an HPLC-UV detector at 238 nm to determine the microcystin-LR content in the adsorbed solution.
[0052] 5. In order to determine the rate of adsorption of microcystin-LR by modified rice husk, a pseudo-first-order kinetic equation was used for fitting. 0.005 g of adsorbent was added to 5 mL of a microcystin-LR solution with an initial concentration of 100 μg / L. The reaction time was 60 min. Samples were taken at intervals (1 min, 2.5 min, 5 min, 10 min, 20 min, 30 min, 40 min, 50 min, 60 min). The concentration of the supernatant after adsorption was measured at 238 nm using a high-performance liquid chromatography-ultraviolet detector to obtain the microcystin-LR content in the solution after adsorption. The fitting formula is as follows;
[0053]
[0054] q e : saturated adsorption capacity, μg / g;
[0055] q t : adsorption amount at time t, μg / g;
[0056] t: time, min;
[0057] k1: pseudo-first-order kinetic constant, min -1 ;
[0058] 6. The effects of coexisting ions (NaCl, MgSO4, CaCO3 and Na2HPO4) at concentrations of 50-200 mg / L (50, 100, 150, 200 mg / L) were studied to investigate the effects of coexisting ions on the adsorption of microcystin-LR. Batch adsorption experiments were conducted on the removal of microcystin-LR from 5 mL of simulated microcystin-LR wastewater using modified rice husk powder. The adsorbent dosage was 0.005 g. The concentration of the supernatant after adsorption was measured at 238 nm using a high-performance liquid chromatography-ultraviolet detector to determine the microcystin-LR content in the adsorbed solution.
[0059] 7. The regenerative performance of the modified adsorbent in adsorbing microcystin-LR was studied within the range of five cycles. 0.1 mol / L HCl solution was used as a desorbent. After reaching adsorption equilibrium, the modified adsorbent was mixed with 50 mL of 0.1 mol / L HCl and desorbed under magnetic stirring at 500 rpm for 30 minutes. The modified adsorbent after desorption was dried for 24 hours. Subsequently, the dried modified adsorbent was added to a microcystin-LR solution of the same concentration for adsorption experiments, and then the concentration of the supernatant after adsorption was measured at 238 nm using a high-performance liquid chromatography-ultraviolet detector to obtain the microcystin-LR content in the solution after adsorption. This process was repeated five times to obtain data on the recyclability of the modified rice husk powder;
[0060] The relevant test results of the bio-based adsorbent capable of removing microcystin-LR of the present invention are as follows:
[0061] The adsorption capacities of MC-LR for original rice husk powder, steam-exploded rice husk powder, steam-exploded and NaOH-modified rice husk powder, and phosphorylated rice husk powder were 132.58, 168.12, 240.29, and 1255.48 μg / g, respectively. The phosphorylated rice husk powder significantly exceeded the combined adsorption capacity of the other three rice husk powders, achieving an unexpected result.
[0062] 1. Using 100 μg / L as the initial concentration, the effect of pH on the adsorption rate of microcystin-LR (MC-LR) was investigated. Figure 1 As shown in the figure, as the pH value increases from 3 to 7, the removal rates of original rice husk powder (RH) and modified rice husk powder (PRH) for microcystin-LR reach their maximum values at pH 6 and pH 5-7, reaching 54.31% and 99.32%, respectively. When the adsorption time, adsorbent addition amount, and initial concentration of methyl violet solution remain unchanged, it can be seen that the adsorption rate of modified rice husk powder for microcystin-LR is significantly higher than that of original rice husk powder.
[0063] 2. Taking 100 μg / L as the initial concentration, the effect of time on the adsorption rate of microcystin-LR was investigated. Figure 2 As shown. It can be seen that as time goes from 0 min to 60 min, the removal rate of RH on MC-LR increases from 20.44% to 54.53%, and the removal rate of PRH on MC-LR increases from 98.79% to 99.32%. When the pH value, the amount of adsorbent added and the initial concentration of the microcystin-LR solution remain unchanged, it can be seen that the adsorption rate of the modified rice husk powder on microcystin-LR is significantly higher than that of the original rice husk powder, and the adsorption rate increases with time. After 10 minutes of adsorption, it reaches a saturated state and the adsorption rate no longer increases;
[0064] 4. Effect of initial concentration of MC-LR on removal efficiency of MC-LR Figure 4 The results showed that as the initial concentration of MV dye increased from 50-400 μg / L, the removal rate of MC-LR by RH decreased from 65.30% to 14.45%, and the removal rate of MC-LR by PRH decreased from 99.32% to 99.03%. Under the condition of constant pH value, adsorption time, and adsorbent dosage, it can be seen that the adsorption rate of MC-LR by modified rice husk powder was significantly higher than that of original rice husk powder, and the adsorption rate decreased with increasing initial concentration.
[0065] 5. Taking 100 μg / L as the initial concentration, the adsorption amount of microcystin-LR at different times was fitted, such as Figure 5 As shown in the figure, as time increases from 0 to 60 min, the pseudo-first-order kinetic parameters of RH and PRH for the adsorption of MC-LR are 0.0791 and 2.2687, respectively. The pseudo-first-order kinetic parameter of PRH is about 28.7 times that of RH, indicating that the adsorption rate of PRH is significantly higher than that of RH. It can be seen that the adsorption rate of modified rice husk powder for microcystin-LR is significantly higher than that of original rice husk powder.
[0066] 6. Using 100 μg / L as the initial concentration, the effect of 50-200 mg / L coexisting ions on the adsorption rate of microcystin-LR was investigated. Figure 6 As shown in the figure. In the presence of coexisting ions (NaCl, MgSO4, CaCO3 and Na2HPO4), the adsorption rate of MC-LR remained relatively stable, showing only a slight decrease, with the lowest drop reaching 96.66%. It can be seen that the modified rice husk powder has a strong anti-interference ability to coexisting ions and shows good environmental adaptability.
[0067] 7. Evaluation of the reusability of modified adsorbents is crucial for their sustainable application. The effect of the number of cycles of modified adsorbents on the adsorption of microcystin-LR is as follows: Figure 7 As shown in the figure, the adsorption rate of MC-LR gradually decreased with the increase of the number of cycles. At the fifth cycle, the removal rate was still maintained above 91.63%. This shows that the modified adsorbent is an adsorbent with good regenerative properties and has broad application potential in the removal of microcystin-LR.
[0068] It can be seen that the bio-based adsorbent of the present invention can remove microcystin-LR in water and can be applied to the treatment of water pollution and harmful algal blooms.
Claims
1. A bio-based adsorbent for removing microcystin-LR from wastewater, characterized in that: The steps of the preparation method are as follows: (1) soaking rice husks with water, then performing steam explosion treatment, then drying the steam-exploded rice husks, grinding the dried rice husks into rice husk powder and sieving to obtain steam-exploded modified rice husk powder; (2) The steam explosion modified rice husk powder was chemically modified with NaOH and STMP to obtain physically and chemically modified rice husk powder.
2. The bio-based adsorbent according to claim 1, characterized in that In step (1), the prepared rice husks are soaked in distilled water at a material-liquid ratio of 1:1-4 for 0.5-2 hours, filtered, and then placed in a steam explosion tank for steam explosion.
3. The bio-based adsorbent according to claim 2, characterized in that In step (1), the prepared rice husks are soaked in distilled water at a material-liquid ratio of 1:2 for 1 hour.
4. The bio-based adsorbent according to claim 1, characterized in that The sieve was passed through a 0.25 mm sieve.
5. The bio-based adsorbent according to any one of claims 1 to 4, characterized in that: The steam explosion pressure is 0.5-2MPa, the steam explosion time is 5-20min, and after the steam explosion, the obtained rice husk is dried at 50-70°C for 15-30h, and then the dried rice husk is put into an oscillating grinder to be ground into rice husk powder and sieved. The obtained material is the steam explosion modified rice husk powder.
6. The bio-based adsorbent according to claim 5, characterized in that The steam explosion pressure was 1.0 MPa, the steam explosion time was 10 min, and after the steam explosion, the obtained rice husk was dried at 60° C. for 24 h.
7. The bio-based adsorbent according to any one of claims 1 to 4, characterized in that In step (2), the steam-exploded modified rice husk powder obtained in step (1) is chemically modified with 2-8% NaOH and 20-40% STMP, and the steam-exploded modified rice husk powder is added to the mixed solution at a material-liquid ratio of 1:30-50, and stirred at 400-1000 rpm at a constant temperature of 30-40°C for 1-4 hours. After modification, the mixture is washed with water to remove residual reagents and then dried.
8. The bio-based adsorbent according to any one of claim 7, characterized in that The steam-exploded modified rice husk powder obtained in step (1) is chemically modified with 5% NaOH and 33.25% STMP. Preferably, the steam-exploded modified rice husk powder is added to the mixed solution at a material-liquid ratio of 1:40, and stirred at 500 rpm at a constant temperature of 35°C for 2 hours.
9. Use of the bio-based adsorbent according to any one of claims 1 to 8 in removing microcystin-LR from water.
10. Use of the bio-based adsorbent according to claim 9 in removing microcystin-LR from water, characterized in that: The material-liquid ratio of bio-based adsorbent to water is 1:10.