Peanut shell-based heavy metal adsorbent, preparation method and application thereof

Abstract

The application discloses a peanut shell-based heavy metal adsorbent and a preparation method and application thereof. The preparation method comprises the following steps: pretreating peanut shell to obtain alkaliized peanut shell powder; under the catalysis of an organic base, the alkaliized peanut shell powder and a methyl vinyl ether / maleic anhydride copolymer are subjected to grafting reaction in a solvent I to prepare a peanut shell-methyl vinyl ether / maleic anhydride copolymer grafting product; under the catalysis of the organic base, the grafting product and a hydroxyl-terminated hyperbranched polyester are subjected to reaction in a solvent II, so that the peanut shell-based heavy metal adsorbent is obtained. The peanut shell-based heavy metal adsorbent prepared by the application has strong adsorption capacity, and the saturated adsorption capacity can reach 1185.50 mg.g 2+ . ‑1 .

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heavy metal wastewater treatment, and particularly relates to a peanut shell-based heavy metal adsorbent and a preparation method and application thereof. BACKGROUND

[0002] With the rise of the electroplating and battery industries, the discharge of heavy metal wastewater is causing more and more pollution to groundwater resources, seriously threatening human health. In the prior art, heavy metal wastewater treated by the chemical precipitation method cannot meet the discharge standard; although the membrane filtration method has excellent heavy metal removal effect, it needs to be replaced regularly with expensive permeable membranes; the removal effect of the high-molecular heavy metal adsorbent is good, but its monomer is highly toxic, difficult to degrade, expensive in raw materials, and high in treatment cost, and thus difficult to be used on a large scale. Therefore, it is urgent to develop a low-cost and efficient heavy metal adsorbent.

[0003] Agricultural waste is cheap and abundant in resources, and the heavy metal adsorbent developed based on agricultural waste has become one of the research directions of scientific researchers. However, the hydroxyl-terminated hyperbranched polymer has a large number of adsorption functional groups and unique internal nanoscale pores in the molecule, and can efficiently adsorb heavy metal ions. If the hyperbranched polymer of this type is functionally modified to agricultural waste, the number of adsorption groups can be significantly increased. On the other hand, the hyperbranched polymer has a structure without chain entanglement, and a large number of adsorption points are exposed on the surface of the molecule, which is more conducive to the full adsorption of heavy metal ions, and is expected to endow it with extremely high adsorption capacity. SUMMARY

[0004] In view of the above background, the present application provides a peanut shell-based heavy metal adsorbent and a preparation method and application thereof. The present application improves the adsorption capacity of the adsorbent by grafting a hydroxyl-terminated hyperbranched polymer onto the surface of peanut shell, and solves the problems of insufficient number of adsorption groups on the surface of peanut shell and low adsorption capacity for heavy metal ions in the prior art.

[0005] To achieve the above object, the technical scheme adopted by the present application is as follows:

[0006] On the one hand, the present application provides a preparation method of a peanut shell-based heavy metal adsorbent, comprising the following steps:

[0007] (1) pretreating peanut shell to obtain alkali-treated peanut shell powder;

[0008] (2) preparing a peanut shell-methyl vinyl ether / maleic anhydride (PVM / MA) copolymer grafting product:

[0009] Under the catalysis of an organic base, the alkali-treated peanut shell powder and the methyl vinyl ether / maleic anhydride (PVM / MA) copolymer are subjected to grafting reaction in a solvent I;

[0010] (3) preparing a peanut shell-based heavy metal adsorbent:

[0011] The grafting of the peanut shell powder obtained in step (1) with a hydroxyl-terminated hyperbranched polyester in a solvent II under the catalysis of an organic base to obtain the peanut shell-based heavy metal adsorbent.

[0012] As a preferred embodiment, the specific operation of step (1) is to obtain the alkaliized peanut shell powder by soaking the peanut shell powder in an alkaline solution.

[0013] Preferably, the alkaline solution is a NaOH solution, a KOH solution or a mixture of both.

[0014] Preferably, the concentration of the alkaline solution is 0.5-1 mol / L.

[0015] Preferably, the soaking time is 24-36 h.

[0016] Preferably, step (1) further comprises a post-treatment operation of washing with water until the pH of the filtrate is neutral and drying.

[0017] In some specific embodiments, the preparation process of the peanut shell powder comprises: crushing, sieving and then soaking in water for at least 24-72 h after washing and drying the peanut shell, and drying.

[0018] Preferably, the sieving is through a 170-230 mesh sieve; further preferably, a 200 mesh sieve.

[0019] As a preferred embodiment, in step (2), the mass ratio of the alkaliized peanut shell powder to the methyl vinyl ether / maleic anhydride (PVM / MA) copolymer is 1:1-3.

[0020] Preferably, in step (2), the organic base is pyridine or 4-dimethylaminopyridine.

[0021] Preferably, in step (2), the solvent I is toluene or xylene.

[0022] Preferably, in step (2), the mass ratio of the organic base to the total mass of the alkaliized peanut shell powder and the methyl vinyl ether / maleic anhydride (PVM / MA) copolymer is 2.0-6.0:1, for example 2.0:1, 2.5:1, 3.0:1, 3.5:1, 4.0:1, 4.5:1, 5.0:1, 5.5:1, 6.0:1 or any ratio therebetween.

[0023] As a preferred embodiment, in step (2), the temperature of the grafting reaction is 60-100°C.

[0024] Preferably, in step (2), the time of the grafting reaction is 15-150 minutes.

[0025] Preferably, step (2) further comprises a pretreatment of swelling operation on the alkali-treated peanut hull powder; the swelling operation is to disperse the alkali-treated peanut hull powder in solvent I, and stir for 0.25-0.5 h.

[0026] Preferably, in the swelling operation, 0.2 g of the alkali-treated peanut hull powder is dispersed in 5-10 mL of solvent I.

[0027] Preferably, step (2) further comprises a post-treatment operation; the post-treatment operation comprises suction filtration, acetone extraction and oven drying and grinding.

[0028] As a preferred embodiment, in step (3), the organic base is triethylamine, triethylenediamine or 4-dimethylaminopyridine.

[0029] Preferably, in step (3), the mass ratio of the grafting product to the hyperbranched polyester with terminal hydroxyl groups is 1:0.5-3, for example 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3 or any ratio therebetween.

[0030] Preferably, in step (3), the mass ratio of the organic base to the total mass of the grafting product and the hyperbranched polyester with terminal hydroxyl groups is 0.1-0.4:1, for example 0.1:1, 0.2:1, 0.3:1, 0.4:1 or any ratio therebetween.

[0031] As a preferred embodiment, in step (3), the temperature of the reaction is 60-100°C.

[0032] Preferably, in step (3), the time of the reaction is 15-150 minutes.

[0033] Preferably, step (3) further comprises a pretreatment of swelling operation on the grafting product; the swelling operation is to disperse the grafting product in solvent II, and stir for 0.5-2 h.

[0034] Preferably, the solvent II is at least one of dioxane, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0035] Preferably, the use amount of the grafting product and solvent II is 1 g of the grafting product corresponding to 15-20 mL of solvent II.

[0036] In certain specific embodiments, step (3) further comprises a post-treatment operation; the post-treatment operation comprises water extraction, oven drying and grinding.

[0037] In another aspect, the present application provides the peanut shell-based heavy metal adsorbent prepared by the above method.

[0038] In another aspect, the present application provides the use of the above peanut shell-based heavy metal adsorbent in the treatment of heavy metal wastewater.

[0039] Preferably, the heavy metal is Cu 2+ , Pb 2+ and / or Cd 2+ , and more preferably Pb 2+ .

[0040] The above technical solution has the following advantages or beneficial effects:

[0041] The present application introduces the methyl vinyl ether / maleic anhydride copolymer chain containing a large number of anhydride groups on the peanut shell through esterification reaction, and further carries out functionalization reaction with the hydroxyl-terminated hyperbranched polyester (Hyper H102) rich in adsorption functional groups by taking the anhydride group as an active point, so that the modified peanut shell has super strong adsorption function for heavy metal ions. The heavy metal adsorbent provided by the present application greatly increases the number of adsorption groups introduced on the surface of the peanut shell, and significantly improves the adsorption capacity of the modified peanut shell for heavy metal wastewater, especially Pb 2+ . The adsorption capacity is as high as 1185.50 mg·g -1 when the initial concentration of Pb 2+ is 800 mg·L -1 at 25℃ and pH 4. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 is the adsorption capacity test result graph of the adsorbent prepared in Example 1 of the present application for different initial concentrations of Pb 2+ . DETAILED DESCRIPTION

[0043] The following examples are only a part of the embodiments of the present application, but not all the embodiments. Therefore, the detailed description of the embodiments of the present application provided below is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0044] In the present application, all the equipment and raw materials, etc. can be purchased from the market or commonly used in the industry, unless otherwise specified. The methods in the following examples are all conventional methods in the art, unless otherwise specified.

[0045] Example 1

[0046] The preparation process of the heavy metal adsorbent in this embodiment is as follows:

[0047] Wash, dry, and crush the discarded peanut shells, sieve out the powder that passes through a 200-mesh sieve, soak it in deionized water for 24 hours, and dry it; soak it in a 1 mol / L NaOH solution for alkalization for 24 hours, then wash it with distilled water several times until it is neutral, and dry it to obtain alkalized peanut shell powder;

[0048] 0.2 g of alkalized peanut shell powder was weighed into a four-necked flask containing 10 mL of toluene and swollen under magnetic stirring for 30 minutes. 0.6 g of methyl vinyl ether / maleic anhydride (PVM / MA) copolymer (purchased from Hubei Chengfeng Chemical Co., Ltd., brand AP13) and 2.5 mL of pyridine were then added in sequence. The mixture was reacted at a constant temperature of 90°C for 45 minutes. The resulting solid product was filtered and extracted with acetone for 48 hours. The peanut shell grafted product was dried and ground for later use.

[0049] 1.0 g of the peanut shell graft prepared above was weighed into a four-necked flask, 20 mL of dioxane was added, and the mixture was swollen under magnetic stirring for 2 hours. At 100°C, 1.0 g of terminal hydroxyl hyperbranched polyester (Hyper H102) was slowly added, and 1.0 mL of triethylamine catalyst was added, and the mixture was reacted for 30 minutes. The reaction product was filtered, extracted with deionized water for 48 hours, dried to constant weight, and ground to obtain a peanut shell-based heavy metal adsorbent.

[0050] Detection of the peanut shell-based heavy metal adsorbent for different initial concentrations of Pb 2+ The adsorption performance of wastewater is studied as follows: prepare different concentrations of Pb at pH 4. 2+ Solutions with concentrations of 0, 100, 200, 300, 400, 500, 600, 700, and 800 mg·L -1 ; Weigh 40mL of each into the reaction vessel, then add 0.01g of each of the above adsorbents; keep the temperature at 25℃ and the oscillator speed at 160r·min -1 The solution was shaken for 2 hours, and a portion of the solution was centrifuged for 20 minutes. The supernatant was taken and the Pb content was detected by atomic absorption spectrometry. 2+ Concentration, test results such as Figure 1 As shown. Figure 1 It can be seen that the adsorption capacity of the peanut shell-based adsorbent increases with the increase of Pb 2 + The initial concentration of Pb increases. 2+ The initial concentration was 800 mg·L -1 When the adsorption capacity reaches 1185.50 mg·g -1 , showing that it has strong adsorption capacity.

[0051] Example 2

[0052] The preparation process of the heavy metal adsorbent in this embodiment is as follows:

[0053] The waste peanut shells are washed, dried, broken, and sieved to obtain powder passing through a 200-mesh sieve. Then, the powder is soaked in deionized water for 24 hours and dried. The peanut shell powder is soaked in a 1 mol / L NaOH solution for 24 hours, washed with distilled water until neutral, and dried to obtain the alkali-treated peanut shell powder.

[0054] 0.2 g of the alkali-treated peanut shell powder is placed in a four-necked flask containing 10 mL of toluene, and magnetically stirred for swelling for 30 minutes. Then, 0.6 g of PVM / MA copolymer and 2.5 mL of pyridine are sequentially added. The reaction is carried out at 90°C for 45 minutes. The solid product obtained by the reaction is subjected to suction filtration, extracted with acetone for 48 hours, and dried to obtain the peanut shell grafted product, which is ground for later use.

[0055] 1.0 g of the peanut shell grafted product prepared above is placed in a four-necked flask, and 20 mL of dioxane is added. The mixture is magnetically stirred for swelling for 2 hours. Then, 2.0 g of hydroxyl-terminated hyperbranched polyester (Hyper H102) is slowly added at 80°C, and 1.5 mL of triethylamine is added as a catalyst. The reaction is carried out for 60 minutes. The reaction product is subjected to suction filtration, and then extracted with deionized water for 48 hours. After drying to a constant weight, the product is ground to obtain the peanut shell-based adsorbent.

[0056] Example 3

[0057] The preparation process of the heavy metal adsorbent in this embodiment is as follows:

[0058] The waste peanut shells are washed, dried, broken, and sieved to obtain powder passing through a 200-mesh sieve. Then, the powder is soaked in deionized water for 24 hours and dried. The peanut shell powder is soaked in a 1 mol / L NaOH solution for 24 hours, washed with distilled water until neutral, and dried to obtain the alkali-treated peanut shell powder.

[0059] 0.2 g of the alkali-treated peanut shell powder is placed in a four-necked flask containing 10 mL of toluene, and magnetically stirred for swelling for 30 minutes. Then, 0.6 g of PVM / MA copolymer and 2.5 mL of pyridine are sequentially added. The reaction is carried out at 90°C for 45 minutes. The solid product obtained by the reaction is subjected to suction filtration, extracted with acetone for 48 hours, and dried to obtain the peanut shell grafted product, which is ground for later use.

[0060] The graft 1.0 g prepared above was weighed into a four-necked flask, 20 mL of dioxane was added, and the mixture was stirred magnetically for 2 hours to swell. Then, 1.5 g of hydroxyl-terminated hyperbranched polyester (Hyper H102) was slowly added at 60°C, and 0.5 mL of triethylamine was added as a catalyst. The reaction was carried out for 150 minutes. The reaction product was filtered, and then extracted with deionized water for 48 hours. After drying to constant weight, the product was ground to obtain a peanut shell-based heavy metal adsorbent.

[0061] The above merely describes the preferred embodiments of the present application. It should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for preparing a peanut shell-based heavy metal adsorbent, characterized in that: The following steps are involved: (1) pre-treating peanut shells to obtain alkalized peanut shell powder; (2) Preparation of peanut shell-methyl vinyl ether / maleic anhydride copolymer grafts: Under the catalytic action of an organic base, alkalized peanut shell powder and methyl vinyl ether / maleic anhydride copolymer are subjected to a grafting reaction in solvent I; the mass ratio of the alkalized peanut shell powder to the methyl vinyl ether / maleic anhydride copolymer is 1:1-3; and the grafting reaction temperature is 60-100°C; (3) Preparation of peanut shell-based heavy metal adsorbent: Under the catalytic action of an organic base, the graft obtained in step (2) is reacted with the terminal hydroxyl hyperbranched polyester in solvent II to obtain the peanut shell-based heavy metal adsorbent; the mass ratio of the graft to the terminal hydroxyl hyperbranched polyester is 1:0.5-3; and the reaction temperature is 60-100°C.

2. The preparation method according to claim 1, characterized in that The specific operation of step (1) is: soaking the peanut shell powder in an alkaline solution to obtain the alkalized peanut shell powder; The alkaline solution is NaOH solution, KOH solution or a mixture of the two; The concentration of the alkaline solution is 0.5 to 1 mol / L; The soaking time is 24 to 36 hours; Step (1) also includes post-treatment operations of washing with water until the pH of the filtrate is neutral and drying.

3. The preparation method according to claim 2, characterized in that The peanut shell powder preparation process includes: washing and drying the peanut shells, crushing and sieving, then soaking them in water for at least 24 to 72 hours, and drying them; The sieving is through a 170-230 mesh sieve.

4. The preparation method according to claim 3, characterized in that The sieving is through a 200-mesh sieve.

5. The preparation method according to claim 1, characterized in that In step (2), the organic base is pyridine or 4-dimethylaminopyridine; In step (2), the solvent I is toluene or xylene; In step (2), the ratio of the mass of the organic base to the total mass of the alkalized peanut shell powder and the methyl vinyl ether / maleic anhydride (PVM / MA) copolymer is 2.0 to 6.0:

1.

6. The preparation method according to claim 1, characterized in that In step (2), the grafting reaction time is 15 to 150 minutes; Step (2) further includes pre-treatment of the alkalized peanut shell powder by performing a swelling operation; the swelling operation comprises dispersing the alkalized peanut shell powder in solvent I and stirring for 0.25 to 0.5 hours; In the swelling operation, 0.2 g of the alkalized peanut shell powder is dispersed in 5 to 10 mL of solvent I; Step (2) also includes post-processing operations; the post-processing operations include filtration, acetone extraction and drying and grinding.

7. The preparation method according to claim 1, characterized in that In step (3), the organic base is triethylamine, triethylenediamine or 4-dimethylaminopyridine; In step (3), the ratio of the mass of the organic base to the total mass of the grafted product and the terminal hydroxyl hyperbranched polyester is 0.1 to 0.4:

1.

8. The preparation method according to claim 1, characterized in that In step (3), the reaction time is 15 to 150 minutes; Step (3) further comprises pre-treatment of the grafted material by a swelling operation; the swelling operation comprises dispersing the grafted material in solvent II and stirring for 0.5 to 2 hours; The solvent II is at least one of dioxane, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide; The relationship between the amount of the graft and the solvent II is: 1g of the graft corresponds to 15-20mL of the solvent II.

9. The preparation method according to claim 1, characterized in that Step (3) also includes post-processing operations; the post-processing operations include water extraction, drying and grinding.

10. A peanut shell-based heavy metal adsorbent obtained by the preparation method according to any one of claims 1 to 9.

11. Use of the peanut shell-based heavy metal adsorbent according to claim 10 in the treatment of heavy metal wastewater, characterized in that: The heavy metal is Cu 2+ , Pb 2+ and / or Cd 2+ .

12. The use according to claim 11, characterized in that The heavy metal is Pb 2+ .

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