Preparation method and application of straw fiber-based aluminum-zinc bimetal salt-absorbing and pollution-reducing composite material

Abstract

The invention belongs to the technical field of environmental functional materials, and discloses a preparation method and application of a straw fiber-based aluminum-zinc bimetal salt-absorbing pollution-reducing composite material. The method comprises the following steps: pretreating straws by using a zinc chloride and lithium chloride composite acid solution to obtain a zinc-containing straw precursor substance, then adding a certain proportion of aluminum chloride, urea and 2-methylimidazole composite solution, fully mixing, adjusting the pH value of the reaction solution, and fully reacting at a certain temperature to obtain the straw fiber-based bimetal salt-absorbing and pollution-reducing composite material. Salt ions and organic pollutants in the environment can be effectively removed. The material is low in cost, easy to obtain, simple in preparation process and suitable for being used as a soil conditioner or a sewage treatment agent.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental functional materials and relates to a preparation method and application of a straw fiber-based aluminum-zinc bimetallic salt-absorbing and pollution-reducing composite material. Background Art

[0002] Bimetallic materials have the advantages of long service life, high reactivity and stable properties, and have been widely studied and applied. Common bimetallic elements include Fe, Cu, Zn, Al, Mn, etc. Bimetallic composite materials can be used as high-efficiency catalysts, ion adsorption exchangers and other highly active environmental remediation agents. Patent CN202111305766.7 discloses a method for promoting nano zero-valent iron manganese bimetallic materials to remove organic pollutants in water bodies, using nano zero-valent iron manganese bimetallic materials as activators, adding biochar, and regulating the catalytic effect of nano zero-valent iron manganese bimetallic materials. Patent CN202211482866.1 discloses a preparation method, copper-based catalyst and application of a copper-based bimetallic catalyst, which fully mixes the raw materials of molecular sieve, copper source, second metal source, ester compound and alcohol compound, and then adds any one of zinc nitrate, gallium nitrate, iron nitrate and indium nitrate, and fully reacts under hydrogen as a reducing agent and solvent-free conditions to obtain a copper-based bimetallic catalyst, which can improve the service life of the catalyst. Although these bimetallic catalysis has efficient catalytic activity, it is easy to form agglomerates, affecting interface contact and reaction. In order to improve its catalytic reaction effect, the catalyst can be loaded on an easily dispersible carrier to improve its environmental mass transfer capacity. Karthikeyan et al. (Karthikeyan et al., Journal of Molecular Liquids 296 (2019) 111766) loaded Zn-Al layered bimetallic composites with banana bag biomass, which improved the catalytic effect of bimetallic active centers and effectively alleviated the deactivation caused by the agglomeration of active centers. However, the composite material needs to be prepared under high temperature and high pressure conditions, and a large amount of energy needs to be consumed. Therefore, finding a material with low preparation cost is an important way to accelerate the application of bimetallic composite materials.

[0003] The present invention uses a zinc chloride and lithium chloride composite acid solution to pretreat straw under ultrasonic conditions to obtain a porous dissolved straw zinc-containing precursor material, then adds a certain proportion of aluminum chloride, urea and 2-methylimidazole composite solution, adjusts the solution pH after sufficient stirring, controls the reaction temperature, continues the reaction for a certain time, centrifuges, fully washes to neutrality, and obtains a straw fiber-based aluminum-zinc bimetallic composite material after drying. The material has the functions of adsorbing salt ions and degrading organic pollutants, can effectively remove salt ions and pollutants in the environment, and is suitable as a soil conditioner or sewage treatment agent. Summary of the invention

[0004] The present invention establishes a preparation method of a straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material through mild reaction between straw and composite salt solution. The method uses zinc chloride and lithium chloride composite acid solution to pretreat straw to obtain zinc-containing straw precursor material, then adds a certain proportion of aluminum chloride, urea and 2-methylimidazole composite solution, and after fully mixing, adjusts the pH of the reaction solution, and fully reacts at a certain temperature to obtain a straw fiber-based bimetallic salt absorption and pollution reduction composite material, which can effectively remove salt ions and organic pollutants in the environment. The material is cheap and easy to obtain and has a simple preparation process, and is suitable as a soil conditioner or sewage treatment agent.

[0005] The technical solution of the present invention:

[0006] A method for preparing a straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material, comprising the following steps:

[0007] (1) Preparation of zinc-containing precursors from straw

[0008] After washing the straw with clean water, drying it naturally in the shade, grinding it into straw powder of 20-100 mesh, and controlling the grinding time to 10-20 minutes; adding lithium chloride and acetic anhydride to the straw powder, the addition amount of lithium chloride and acetic anhydride accounting for 1%-2% and 0.1%-0.5% of the mass of the straw respectively, grinding for 3-5 minutes, then adding zinc chloride and ammonium persulfate, the addition amount of zinc chloride and ammonium persulfate accounting for 5%-10% and 0.1%-2% of the mass of the straw respectively, and continuing to grind for 5-10 minutes, then adding distilled water 3-5 times the mass of the straw, reacting at 50-80°C for 15-20 hours, cooling to room temperature, separating the solid and liquid, washing the material with distilled water until neutral, and fully drying it in a 50-60°C forced air drying oven to obtain a zinc-containing straw precursor;

[0009] (2) Preparation of straw fiber-based bimetallic composites

[0010] The zinc-containing straw precursor obtained in step (1) is added to a composite solution containing aluminum chloride, urea and 2-methylimidazole, and subjected to ultrasonic treatment for 5-10 minutes. Then, 0.1%-1% of the mass of the zinc-containing straw precursor is added with sodium thiosulfate, and the mixture is stirred thoroughly. The pH of the reaction solution is adjusted to 9-10 with 2 mol / L NaOH and 1 mol / L Na2CO3 solution, and ultrasonic treatment is performed for 5 minutes. The mixture is reacted at 70-80°C for 1-3 days, cooled to room temperature, separated from the solid and the liquid, and washed with distilled water until neutral. Substances not participating in the reaction are removed, and the solid material is dried thoroughly at 60-70°C to obtain a straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material.

[0011] The straws include corn straws, wheat straws, rice straws, cotton straws and the like.

[0012] The masses of the aluminum chloride, urea and 2-methylimidazole are controlled within 1%-5%, 0.5%-2% and 3%-8% of the mass of the zinc-containing straw precursor material.

[0013] Screening and application of straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite materials

[0014] Take the straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material, add it to the solution containing salt water or organic pollutants according to the solid-liquid ratio of 1:50 or 1:100 (mass g: volume ml), wherein 0.1%-0.5% of the mass of the solution of the organic pollutant is added to the solution of the organic pollutant, and fully react for 10-20 hours, then measure the residual amount of salt or organic pollutants in the solution, and obtain the removal rate of salt or organic pollutants in the solution. By comparison, the best straw fiber-based bimetallic salt absorption and pollution reduction composite material is screened. The screened composite material is applied to the removal of salt and organic pollutants in the water body or soil adjacent to the farmland according to a certain proportion.

[0015] The salt ions in the brine include Na + , K + , Ca 2+ Mg 2+ , Cl - 、SO4 2- wait.

[0016] The organic pollutants include herbicides, pesticides, fungicides, antibiotics, etc. that are often detected in water and soil.

[0017] The beneficial effects of the present invention are as follows: the present invention uses waste straw, firstly uses acetic anhydride and lithium chloride composite solution to pre-treat the straw, breaks the dense crystalline structure of the straw, and then undergoes ammonium persulfate oxidation to increase the binding force between zinc ions and straw fiber carbon base, thereby obtaining a zinc-containing straw precursor material; then a certain proportion of aluminum chloride and urea composite solution is added, and urea molecules can protect zinc ions and aluminum ions from being attacked by hydronium ions, thereby enhancing the confined spatial stability of zinc ions and aluminum ions, and then 2-methylimidazole solution is added, and the pH of the reaction solution is adjusted, and the reaction is fully reacted at a certain temperature to obtain a straw bimetallic salt absorption and pollution reduction composite material, thereby increasing the dispersion of the active aluminum-zinc bimetallic active center, preventing inactivation due to aggregation under high pollution concentrations, and effectively removing salt ions and organic pollutants in the environment. The material is cheap and readily available, and the preparation process is simple, and can be used to remove salt ions or organic pollutants in water bodies or soil near farmland. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the salt absorption effect of straw fiber-based bimetallic composite materials.

[0019] Figure 2It is the effect of straw fiber-based bimetallic composite materials in degrading organic pollutants. DETAILED DESCRIPTION

[0020] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0021] Example 1 Preparation of straw fiber-based bimetallic composite materials and evaluation of their salt absorption performance

[0022] The discarded straw was retrieved from the farmland, washed with clean water, dried naturally in the shade, 50.0 g was weighed, ground with a grinder for 10 min, 0.5 g lithium chloride and 0.2 g acetic anhydride were added respectively, ground for 3 min, 0.05 g zinc chloride and 0.5 g ammonium persulfate were added in sequence, and grinding was continued for 5 min, then 150 mL distilled water was added, reacted at 50 ° C for 15 h, cooled to room temperature, solid-liquid separation was performed, the material was washed with distilled water until neutral, and fully dried in a 50 ° C forced air drying oven to obtain a zinc-containing straw precursor.

[0023] The zinc-containing straw precursor material was added to a composite solution containing 1.0g aluminum chloride, 0.5g urea and 2.0g 2-methylimidazole, ultrasonicated for 5min, 0.05g sodium thiosulfate was added, stirred thoroughly, and the pH of the reaction solution was adjusted to 9.0 with self-prepared 2mol / L NaOH and 1mol / L Na2CO3 solutions. Ultrasonicated for 5min, reacted at 70°C for 1d, cooled to room temperature, separated from the solid and liquid, washed with distilled water until neutral, substances not participating in the reaction were removed, and the solid material was fully dried at 60°C to obtain the straw fiber-based bimetallic composite material A1.

[0024] According to the above method, the dosage of zinc chloride was changed to 0.1g, 0.5g, and 1.0g respectively, and other reaction conditions remained unchanged to obtain straw fiber-based bimetallic composite materials A2, A3, and A4. Weigh 0.5g of the prepared straw fiber-based bimetallic composite materials in turn, add them to the prepared 10g / L NaCl salt solution at a solid-liquid ratio of 1:50, and fully react for 20h, then measure the salt content in the solution, set a control, and repeat 3 times in each group. The results are shown in the attached figure. Figure 1 As shown, overall, with the increase of zinc chloride dosage, the salt absorption capacity of the composite material gradually increases. When the zinc chloride dosage is 0.5 g, the salt absorption capacity of the composite material reaches a maximum value of 32 mg / g.

[0025] Example 2 Preparation of zinc-containing precursor from straw under different temperature conditions

[0026] The discarded straw was retrieved from the farmland, washed with clean water, dried naturally in the shade, 50.0 g was weighed, ground with a grinder for 15 min, 1.0 g lithium chloride and 0.25 g acetic anhydride were added respectively, ground for 3 min, 0.05 g zinc chloride and 0.5 g ammonium persulfate were added in sequence, and grinding continued for 5 min, then 150 mL distilled water was added, and the reaction was carried out at 50 ° C, 60 ° C, 70 ° C, and 80 ° C for 20 h, cooled to room temperature, solid-liquid separation was performed, the material was washed with distilled water until neutral, and fully dried in a 50 ° C forced air drying oven to obtain zinc-containing straw precursor materials prepared under different conditions. Other preparation conditions were carried out according to Example 1.

[0027] In order to compare the effect of pretreatment, the treatment condition without adding lithium chloride and acetic anhydride was adopted, that is, the discarded straw was retrieved from the farmland, washed with clean water, dried naturally in the shade, 50.0g was weighed, ground with a grinder for 15min, 150mL of distilled water was added, reacted at 50℃ for 20h, cooled to room temperature, solid-liquid separation, the material was washed with distilled water to neutrality, and fully dried in a 50℃ forced air drying oven to obtain zinc-containing straw precursor. By comparison, the differences of zinc-containing straw precursors under different temperature pretreatments were analyzed. The results showed that the zinc-containing precursors prepared under different temperature treatments, and the bimetallic composites prepared by adding a composite solution of aluminum chloride, urea and 2-methylimidazole had higher salt absorption, and the maximum salt absorption reached 46mg / g. At the same time, compared with the treatment conditions without adding lithium chloride and acetic anhydride, the composites prepared under different temperature treatments had higher salt absorption. This further indicates that lithium chloride and acetic anhydride treatment can destroy the dense fiber structure of straw and increase the loading amount of zinc chloride, thereby enhancing the salt absorption capacity of the bimetallic composite material.

[0028] Example 3 Effect of urea addition on straw fiber-based bimetallic composites

[0029] The discarded straw was retrieved from the farmland, washed with clean water, dried naturally in the shade, 50.0 g was weighed, ground with a grinder for 10 min, 0.8 g lithium chloride and 0.2 g acetic anhydride were added respectively, ground for 3 min, 0.05 g zinc chloride and 0.5 g ammonium persulfate were added in sequence, and grinding was continued for 5 min, then 150 mL distilled water was added, reacted at 80 ° C for 15 h, cooled to room temperature, solid-liquid separation was performed, the material was washed with distilled water until neutral, and fully dried in a 50 ° C forced air drying oven to obtain a zinc-containing straw precursor.

[0030] The zinc-containing straw precursor was added to a composite solution containing 1.0g aluminum chloride, 0.25g urea and 2.0g 2-methylimidazole, ultrasonicated for 5min, 0.05g sodium thiosulfate was added, stirred thoroughly, and the pH of the reaction solution was adjusted to 9.0 with self-prepared 2mol / L NaOH and 1mol / L Na2CO3 solution, ultrasonicated for 5min, reacted at 70℃ for 1d, cooled to room temperature, separated solid and liquid, washed with distilled water until neutral, removed substances that did not participate in the reaction, and the solid material was fully dried at 60℃ to obtain a straw fiber-based bimetallic composite material. According to the above steps, the amount of the variable urea was 0.50g and 1.0g respectively, and the other reaction conditions remained unchanged, and the straw fiber-based bimetallic composite materials under different urea dosage conditions were prepared. The results show that under the three urea dosages, when the urea dosage is 1.0g, the prepared straw fiber-based bimetallic composite material has a higher salt absorption capacity, reaching 52mg / g. This further indicates that with the increase in the amount of urea, aluminum ions and zinc ions can combine better with straw, reducing the attack of water molecules on metal ions, thereby increasing the efficiency of the synthesis of straw fiber bimetallic composites.

[0031] Example 4 Preparation of straw fiber-based bimetallic composite materials and their degradation effects on organic pollutants

[0032] The discarded straw was retrieved from the farmland, washed with clean water, dried naturally in the shade, 50.0 g was weighed, ground with a grinder for 10 min, 1.0 g lithium chloride and 0.25 g acetic anhydride were added respectively, ground for 5 min, 0.5 g zinc chloride and 1.0 g ammonium persulfate were added in sequence, and grinding was continued for 5 min, then 150 mL distilled water was added, reacted at 50 ° C for 20 h, cooled to room temperature, solid-liquid separation was performed, the material was washed with distilled water until neutral, and fully dried in a 50 ° C forced air drying oven to obtain a zinc-containing straw precursor.

[0033] The zinc-containing straw precursor material was added to a composite solution containing 0.5g aluminum chloride, 1.0g urea and 4.0g 2-methylimidazole, ultrasonicated for 5min, 0.1g sodium thiosulfate was added, stirred thoroughly, and the pH of the reaction solution was adjusted to 9.0 with self-prepared 2mol / L NaOH and 1mol / L Na2CO3 solutions. Ultrasonicated for 5min, reacted at 70°C for 2d, cooled to room temperature, separated from the solid and liquid, washed with distilled water until neutral, substances not participating in the reaction were removed, and the solid material was fully dried at 60°C to obtain the straw fiber-based bimetallic composite material B1.

[0034] According to the above method, the amount of aluminum chloride was changed to 1.0g, 2.0g, and 2.5g respectively, and other reaction conditions remained unchanged to obtain straw fiber-based bimetallic composite materials B2, B3, and B4. Weigh 0.5g of the prepared straw fiber-based bimetallic composite materials in turn, add them to the prepared 500mg / L chlorpyrifos pesticide solution at a solid-liquid ratio of 1:50, add 0.025g of sodium persulfate, and fully react for 20h, then determine the chlorpyrifos content in the solution, set a control, and repeat 3 times in each group. The results are shown in the attached figure. Figure 2 As shown, overall, with the increase of aluminum chloride dosage, the ability of the composite material to reduce chlorpyrifos pesticides gradually increased. When the aluminum chloride dosage was 2.0 g, the removal rate of the composite material for chlorpyrifos reached a maximum value of 95%.

Claims

1. A method for preparing a straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material, characterized in that: Here are the steps: (1) Preparation of zinc-containing precursors from straw After washing the straw with clean water, drying it naturally in the shade, grinding it into straw powder of 20-100 mesh, and controlling the grinding time to 10-20 minutes; adding lithium chloride and acetic anhydride to the straw powder, the addition amount of lithium chloride and acetic anhydride accounting for 1%-2% and 0.1%-0.5% of the mass of the straw respectively, grinding for 3-5 minutes, then adding zinc chloride and ammonium persulfate, the addition amount of zinc chloride and ammonium persulfate accounting for 5%-10% and 0.1%-2% of the mass of the straw respectively, and continuing to grind for 5-10 minutes, then adding distilled water 3-5 times the mass of the straw, reacting at 50-80°C for 15-20 hours, cooling to room temperature, separating the solid and liquid, washing the material with distilled water until neutral, and fully drying it in a 50-60°C forced air drying oven to obtain a zinc-containing straw precursor; (2) Preparation of straw fiber-based bimetallic composites The zinc-containing straw precursor obtained in step (1) is added to a composite solution containing aluminum chloride, urea and 2-methylimidazole, wherein the addition amounts of aluminum chloride, urea and 2-methylimidazole are controlled at 1%-5%, 0.5%-2% and 3%-8% of the mass of the zinc-containing straw precursor, and ultrasonic treatment is performed for 5-10 minutes. Then, sodium thiosulfate in an amount of 0.1%-1% of the mass of the zinc-containing straw precursor is added, and the mixture is stirred thoroughly. The pH value of the reaction solution is adjusted to 9-10 with 2 mol / L NaOH and 1 mol / L Na2CO3 solution, and ultrasonic treatment is performed for 5 minutes. The mixture is reacted at 70-80°C for 1-3 days, cooled to room temperature, separated from the solid and the liquid, and washed with distilled water until neutral, substances not participating in the reaction are removed, and the solid material is fully dried at 60-70°C to obtain a straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material.

2. The method for preparing the straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material according to claim 1, characterized in that: The straws include corn straws, wheat straws, rice straws and cotton straws.

3. Application of the straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material obtained by the preparation method of claim 1 or 2, characterized in that: Take straw fiber-based aluminum-zinc bimetallic salt absorption and pollution reduction composite material, according to the solid-liquid ratio of 1:50 or 1:100, The solid-liquid ratio is mass g: volume ml, which is added to the solution containing salt water or organic pollutants. The solution of organic pollutants needs to additionally add 0.1%-0.5% of the solution mass of sodium persulfate, and fully react for 10-20 hours. Then the residual salt or organic pollutants in the solution are measured to obtain the removal rate of the salt or organic pollutants in the solution. By comparison, the best straw fiber-based bimetallic salt-absorbing and pollution-reducing composite material is screened; the screened straw fiber-based bimetallic salt-absorbing and pollution-reducing composite materials are used in proportion to remove salt and organic pollutants in water bodies or soil adjacent to farmland.

4. The use according to claim 3, characterized in that: The salt ions in the brine include Na + , K + , Ca 2+ Mg 2 + , Cl - 、SO4 2- .

5. The use according to claim 3, characterized in that: The organic pollutants include herbicides, pesticides, fungicides and antibiotics.

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