Spherical schwertmannite-lignocellulose composite adsorption material as well as preparation method and application thereof

Abstract

The invention discloses a spherical Schwertmannite-lignocellulose composite adsorption material and a preparation method and application thereof, and the spherical Schwertmannite-lignocellulose composite adsorption material is prepared from Schwertmannite and bagasse lignocellulose through an embedding method. The problems that a biomass adsorbent is low in Cr (VI) adsorption performance under the alkaline condition and a Schwertmannite adsorbent is prone to loss are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorption materials, and in particular relates to a spherical Schmidt mineral-lignocellulose composite adsorption material and a preparation method and application thereof. Background Art

[0002] Hexavalent chromium (Cr(VI)) is a typical toxic and harmful heavy metal pollutant in water, and its pollution control has always attracted much attention. At present, the main methods for removing Cr(VI) from water include chemical reduction precipitation, adsorption, and biological methods. Adsorption is fast and effective, with little secondary pollution, and is most suitable for the treatment of medium and low concentration Cr(VI) polluted water. Among them, the use of low-cost lignocellulosic biomass materials to adsorb heavy metal pollutants such as Cr(VI) in water has been one of the research hotspots in the adsorption field in recent years, which is called biosorption. On the one hand, studies have reported that biomass and its modified biosorption materials have a good removal effect on Cr(VI) under acidic conditions. The main reason is that Cr(VI) is more easily reduced and converted into Cr(III) under acidic conditions; and as the pH of the solution increases to alkaline conditions, the adsorption removal effect gradually weakens. On the other hand, studies have found that Schmidt mineral materials rich in sulfate and iron ions have good adsorption properties for Cr(VI) in water under alkaline conditions, but Schmidt mineral is a powder material and is easily lost in water as an adsorbent, making it difficult to recycle and reuse. Summary of the invention

[0003] The object of the present invention is to provide a spherical Schreiber mineral-lignocellulose composite adsorption material and a preparation method and application thereof. The spherical Schreiber mineral-lignocellulose composite adsorption material is prepared by an embedding method, which improves the problems of low adsorption performance of biomass adsorbent for Cr(VI) under alkaline conditions and easy loss of Schreiber mineral adsorbent.

[0004] The technical solution of the present invention is as follows:

[0005] A method for preparing a spherical Schmidt mineral-lignocellulose composite adsorption material comprises the following steps:

[0006] (1) Cleaning, drying and crushing bagasse to obtain bagasse powder, mixing 1-allyl-3-methylimidazolium chloride, N,N-dimethylformamide, bagasse powder and NaHCO3 in a mass ratio of 10:8-12:0.5-0.7:0.05-0.07, and stirring at 110°C for 1 hour to obtain a sugarcane lignocellulose viscose solution with all components dissolved;

[0007] (2) mixing the Schmidt mineral with the sugarcane lignocellulose viscose solution, stirring continuously at 105-115° C. for 0.8-1.2 h to obtain a composite solution, wherein the mass ratio of the Schmidt mineral to the sugarcane bagasse powder is 4-6:3;

[0008] (3) In a coagulation bath, the composite solution was dropped into 0.1 mol·L -1 The spherical Schmidt mineral-lignocellulose composite adsorption material is obtained by aging the spherical Schmidt mineral-lignocellulose composite adsorption material in an aqueous solution of HCl for 3.4-4.5 hours, washing and freeze-drying, and the temperature of the coagulation bath is not more than 40°C.

[0009] In some possible implementations, the preparation method of Schroeder mineral comprises the following steps: slowly dripping a 30 wt % H2O2 solution into Fe 2+ Concentration is 2g·L -1 The ferrous salt solution is stirred at room temperature for 24 hours, the solid is retained, and freeze-dried. The volume ratio of H2O2 solution to ferrous salt solution is 1:160-240.

[0010] In some possible implementations, the ferrous salt is ferrous sulfate and / or ferrous sulfate heptahydrate.

[0011] In some possible implementations, the dripping speed of the H2O2 solution is 1 drop every 2 minutes.

[0012] In some possible implementations, the drying temperature in step (1) is 55-60° C., and the drying time is 24 hours.

[0013] In some possible implementations, the particle size of bagasse powder is less than 100 mesh, and the particle size of Schroeder mineral is less than 200 mesh.

[0014] A spherical Schmidt mineral-lignocellulose composite adsorption material is prepared by the above preparation method.

[0015] An adsorbent comprises the spherical Schreiberite-lignocellulose composite adsorbent material.

[0016] Application of the spherical Schottky mineral-lignocellulose composite adsorption material or the adsorbent in adsorbing Cr(VI) in water.

[0017] The present invention has at least the following beneficial effects:

[0018] The spherical Schmitt mineral-lignocellulose composite adsorption material (Sch@LCB) prepared by the present invention is in the form of ocher yellow small spheres, with complete shape, uniform particle size, average particle size of about 2 mm, not easy to break and good mechanical strength; it shows good adsorption effect under alkaline conditions, i.e., pH=8-9, and has good regeneration performance, and has the potential for repeated utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the preparation process of spherical Schmidtite-lignocellulose composite adsorbent (ScH@LCB);

[0020] Figure 2 This is the appearance photo of the spherical Schmidt mineral-lignocellulose composite adsorbent (ScH@LCB);

[0021] Figure 3 is the adsorption performance of Sch@LCB under different pH conditions;

[0022] Figure 4 The adsorption performance of Sch@LCB under different dosage conditions;

[0023] Figure 5 For Sch@LCB regeneration adsorption research;

[0024] Figure 6 The effect of coexisting ions on the adsorption of hexavalent chromium by Sch@LCB;

[0025] Figure 7 This paper studies the stability performance of Sch@LCB adsorbent. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0027] In the following examples, the water used can be one or more of distilled water, purified water, and drinking water; unless otherwise specified, the detection methods in the following examples are conventional detection methods; unless otherwise specified, the reagents in the following examples are purchased from commercial channels. The Schmidt mineral in Example 1 is obtained by reacting ferrous sulfate heptahydrate with hydrogen peroxide. In other possible implementations, the Schmidt mineral can also be purchased directly from commercial channels.

[0028] In step (4) of Example 1, 0.1 mol·L -1 The HCl aqueous solution as a reagent in the coagulation bath has no proportional relationship with the composite solution, and only needs to be able to submerge the spherical Schreiberite-lignocellulose composite adsorption material.

[0029] Example 1

[0030] according to Figure 1 The preparation method of the spherical Schröss mineral-lignocellulose composite adsorbent (Sch@LCB) comprises the following steps:

[0031] (1) The bagasse was washed with tap water, dried in an air drying oven at 60° C. for 24 hours, crushed with a ball mill, and passed through a 100-mesh sieve to obtain bagasse powder.

[0032] Weigh 10 g of ionic liquid (1-allyl-3-methylimidazolium chloride) into a three-necked flask, and weigh 10 g of N,N-dimethylformamide (DMF), 0.6 g of bagasse, and 0.06 g of NaHCO3 and slowly add them. Stir and react at 110 °C for 1 h to obtain a sugarcane lignocellulose viscose solution with all components dissolved.

[0033] (2) Add 10 g of FeSO4·7H2O to 1 L of ultrapure water, stir with a magnetic stirrer until completely dissolved to obtain a ferrous salt solution, then add 5 mL of a 30 wt% H2O2 solution to the ferrous salt solution at a rate of 1 drop every 2 minutes, and continue stirring the mixed solution at room temperature for 24 hours. Finally, separate the solid and liquid by suction filtration to obtain a solid, which is Schroeder mineral. After freeze-drying the above-mentioned Schroeder mineral, collect the Schroeder mineral powder under the sieve through a 200-mesh sieve and store it at low temperature for later use.

[0034] (3) The powder of the Schmidt mineral was mixed with the sugarcane lignocellulose viscose solution, and the mixture was stirred at 100 rpm for 1 h at 110° C. to obtain a composite solution, wherein the mass ratio of the Schmidt mineral to the sugarcane bagasse powder was 5:3.

[0035] (4) While the fully mixed composite solution is still hot, add 0.1 mol·L -1 The spherical product was solidified into a spherical shape in an HCl aqueous solution (control the coagulation bath temperature not higher than 40°C). After standing for 4 hours, the spherical product was washed with deionized water for 3 times and freeze-dried to obtain a spherical Schmidt mineral-lignocellulose composite adsorption material, the morphology of which is as follows: Figure 2 As shown, the spherical Schmidt mineral-lignocellulose composite adsorption material is in the shape of ochre yellow small spheres with complete shape, uniform particle size, an average particle size of about 2 mm, not easy to break and good mechanical strength.

[0036] Performance Testing

[0037] (1) Adsorption performance test of Sch@LCB under different pH conditions

[0038] Prepare Cr(VI) at a concentration of 50 mg·L -1 , a series of solutions with pH values ​​of 2, 3, 4, 5, 6, 7, 8, 9, and 10 were added with Sch@LCB at a dosage of 2 g·L -1 , reacted at 298K for 24h, the adsorption results are as follows Figure 3 As shown in Figure 2, it can be seen that with the increase of pH, the equilibrium adsorption amount (q e ) gradually increased. Under alkaline conditions, i.e., pH = 8-9, the adsorbent Sch@LCB showed a good adsorption effect.

[0039] (2) Adsorption performance test of Sch@LCB at different dosages

[0040] The initial Cr(VI) concentration was 50 mg·L -1 Sch@LCB (dosages were 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 g·L -1 ), reacted at 298K for 24h, the adsorption results are as follows Figure 4 As shown in the figure, with the increase of the dosage of Sch@LCB during the adsorption process, the adsorption amount of the adsorbent material per unit mass decreased, and the adsorption removal rate of Cr(VI) in water gradually increased.

[0041] (3) Recycling performance

[0042] Four adsorption-desorption experiments were carried out on Sch@LCB (C 0Cr =50mg·L -1 , pH = 8.00, dosage = 2 g·L -1 , t = 24h), the adsorption rate data are as follows Figure 5 As shown in the figure, after four adsorption-desorption experiments, the adsorption rate of Sch@LCB for Cr(VI) still remained at about 40%, indicating that Sch@LCB has good regeneration performance and has the potential for reuse.

[0043] (5) Coexisting ion experiment

[0044] In the binary system, the cations Ni(Ⅱ) and Cu(Ⅱ) and the anion SO4 2- and Cl - Effect of coexistence conditions on the adsorption performance of Sch@LCB material for Cr(VI) removal. The concentration of each coexisting ion was set to 0.4mmol / L, pH=8, temperature 298K, and contact time 24h. Figure 6 As shown, Cl - The coexistence of Ni(Ⅱ) and SO(VI) had little effect on the adsorption and removal of Cr(VI). The coexistence of Ni(Ⅱ) promoted the adsorption and removal of Cr(VI). 2 4 - , copper ions (Cu(Ⅱ)) will inhibit the adsorption of Cr(VI) to a certain extent.

[0045] (6) Stability test

[0046] Freshly prepared Sch@LCB and Sch@LCB stored for one year were used to adsorb Cr(VI) (pH=8.00, C 0Cr =50mg·L -1 ,T=298K,t=24h) Figure 7 As shown in Figure 2, the adsorption capacities of the two are 13.52 mg·g -1 and 11.89 mg·g -1, indicating that the Sch@LCB adsorbent has a stable structure and is effective for a long time.

[0047] The above description is only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a spherical Schmidt mineral-lignocellulose composite adsorption material, characterized in that: The steps include: (1) washing, drying and crushing bagasse to obtain bagasse powder, mixing 1-allyl-3-methylimidazolium chloride, N,N-dimethylformamide, bagasse powder and NaHCO3 in a mass ratio of 10:8-12:0.5-0.7:0.05-0.07, and stirring continuously at 105-115° C. for 0.8-1.2 h to obtain a sugarcane lignocellulose viscose solution with all components dissolved; (2) mixing the Schmidt mineral with the sugarcane lignocellulose viscose solution, stirring continuously at 105-115° C. for 0.8-1.2 hours to obtain a mixed liquid, wherein the mass ratio of the Schmidt mineral to the sugarcane bagasse powder is 4-6:3; (3) In a coagulation bath, the composite solution was dropped into 0.1 mol·L -1 The spherical Schmidt mineral-lignocellulose composite adsorption material is obtained by aging the spherical Schmidt mineral-lignocellulose composite adsorption material in an aqueous solution of HCl for 3.5-4.5 hours, washing and freeze-drying, wherein the temperature of the coagulation bath is not greater than 40°C.

2. The preparation method according to claim 1, characterized in that The preparation method of the Schmidtite comprises the following steps: slowly dripping a 30 wt % H2O2 solution into the Fe 2+ Concentration is 2g·L -1 The ferrous salt solution is stirred at room temperature for 24 hours, and the solid is retained to obtain the Schmidt mineral, and the volume ratio of the H2O2 solution to the ferrous salt solution is 1:160-240.

3. The preparation method according to claim 2, characterized in that: The ferrous salt is ferrous sulfate and / or ferrous sulfate heptahydrate.

4. The preparation method according to claim 2, wherein the H2O2 solution is added at a rate of 1 drop every 2 minutes.

5. The preparation method according to claim 1, characterized in that: The drying temperature of step (1) is 55-60°C and the drying time is 24h.

6. The preparation method according to claim 1, characterized in that: The particle size of the bagasse powder is less than 100 meshes, and the particle size of the Schmidtite is less than 200 meshes.

7. A spherical Schmidt mineral-lignocellulose composite adsorption material, characterized in that: Prepared by the preparation method described in any one of claims 1 to 6.

8. An adsorbent, characterized in that The invention comprises the spherical Schmidt mineral-lignocellulose composite adsorption material as described in claim 8.

9. Use of the spherical Schottky mineral-lignocellulose composite adsorption material according to claim 7 or the adsorbent according to claim 8 in adsorbing Cr(VI) in water.

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