A renewable adsorbent for heavy metal ion removal and its preparation method

Abstract

The present invention relates to the technical field of heavy metal adsorbents, and specifically relates to a renewable adsorbent for removing heavy metal ions and a preparation method thereof. The renewable adsorbent comprises the following raw materials in parts by weight: 10-15 parts of modified loofah sponge, 8-12 parts of salicylaldehyde thiosemicarbazide triazine; the preparation raw materials of the modified loofah sponge are made from loofah sponge, epichlorohydrin and pentaerythritol tetra(3-mercaptopropionate), and the preparation raw materials of the salicylaldehyde thiosemicarbazide triazine comprise the following components in parts by weight: 2-3 parts of 5-chloromethyl salicylaldehyde, 1.2-1.6 parts of thiosemicarbazide, 6.5-9.7 parts of cyanuric chloride. The renewable adsorbent prepared by the present invention has a high adsorption capacity and good cycling performance.

Description

Technical Field

[0001] The present invention relates to the technical field of heavy metal adsorbents, and particularly relates to a renewable adsorbent for removing heavy metal ions and a preparation method thereof. Background Art

[0002] With the rapid development of industrialization, heavy metal ions enter the environment through different channels and continuously accumulate. Heavy metal pollution has become one of the main pollutants in water pollution. Wastewater discharged from industries such as electroplating, mining, metallurgy, and chemical engineering contains toxic heavy metal ions such as lead (Pb²⁺), cadmium (Cd²⁺), mercury (Hg²⁺), and arsenic (As³⁺). Due to their non-degradability and bioaccumulation, they pose a serious threat to the ecological environment and human health. Traditional water treatment technologies such as chemical precipitation, membrane separation, and electrolysis have certain effects, but generally have problems such as high cost, high energy consumption, or secondary pollution. Among them, the adsorption method is widely used because of its simple operation and controllable cost, but its core bottleneck lies in the performance and regeneration ability of the adsorbent. Currently, commonly used adsorbents include activated carbon, zeolite, ion exchange resin, and biomass materials. Although activated carbon has a relatively high adsorption capacity, its regeneration requires high-temperature calcination or strong acid treatment, resulting in structural collapse and performance degradation; synthetic resins are costly and have low regeneration efficiency; while natural clay or agricultural waste (such as rice husks, straw) are widely sourced, but the raw materials without modification have poor adsorption selectivity and low mechanical strength, making it difficult to be recycled. In recent years, although nanomaterials (such as graphene, metal-organic frameworks) have shown high adsorption efficiency, their complex preparation process, environmental risks, and difficulty in recovery limit their large-scale application. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a renewable adsorbent for removing heavy metal ions and a preparation method thereof.

[0004] The present invention is achieved through the following technical solutions:

[0005] A renewable adsorbent for removing heavy metal ions, comprising the following raw materials in parts by weight: 10 - 15 parts of modified loofah sponge, 8 - 12 parts of salicylaldehyde thiosemicarbazide triazine.

[0006] Further, the preparation method of the modified loofah sponge comprises the following steps:

[0007] A1: Cut the loofah sponge into blocks with a size of 2×2 cm, soak it in water, change the water every 2 h, wash it repeatedly, after 24 h, immerse it in a 5% (w / v) NaOH solution, continuously stir at 60 °C and 200 - 300 rpm for 3 h, wash it with ultrapure water until neutral, and dry it under vacuum at 80 °C to obtain pretreated loofah sponge;

[0008] A2: Add the pretreated loofah sponge obtained in step A1 into a 3 mol / L NaOH solution, add epichlorohydrin and absolute ethanol, keep it in a constant temperature water bath at 50 °C, stir and react for 3 h, wash it with ethanol, and dry it to obtain epoxidized loofah sponge.

[0009] A3: Under N2 protection, add the epoxidized loofah sponge and pentaerythritol tetra(3-mercaptopropionate) obtained in step A2 into ethanol, disperse them by ultrasonic wave at 300 - 400 W for 20 - 30 min, add triethylamine, stir and react at room temperature for 3 - 4 h, wash it with absolute ethanol, and dry it under vacuum to obtain modified loofah sponge.

[0010] Furthermore, in step A2, the dosage ratio of the pretreated loofah sponge, NaOH solution, epichlorohydrin and absolute ethanol is 1 g:50 mL:15 mL:10 mL.

[0011] Furthermore, in step A3, the dosage ratio of the epoxidized loofah sponge, pentaerythritol tetra(3-mercaptopropionate), ethanol and triethylamine is 1 g:2 g:40 - 60 mL:6 - 10 mL.

[0012] Furthermore, the preparation raw materials of the salicylaldehyde thiosemicarbazide triazine include the following components in parts by weight: 6 - 9 parts of 5-chloromethyl salicylaldehyde, 4 - 6 parts of thiosemicarbazide, and 2 - 3 parts of cyanuric chloride.

[0013] Furthermore, the preparation method of the salicylaldehyde thiosemicarbazide triazine includes the following steps:

[0014] B1: Dropwise add the ethanol solution of 5-chloromethyl salicylaldehyde into the ethanol solution of thiosemicarbazide, heat under reflux for 4 - 5 h, cool to room temperature, filter by suction, wash the filter cake with ethanol, and dry it under vacuum at 60 - 70 °C to obtain chloromethyl salicylaldehyde thiosemicarbazone.

[0015] B2: Add cyanuric chloride into 1,4-dioxane and mix well to obtain a mixed solution. Add the chloromethyl salicylaldehyde thiosemicarbazone obtained in step B1 and potassium carbonate into 1,4-dioxane and mix well. Dropwise add the mixed solution under an ice-water bath, stir evenly, heat to 80 - 90 °C, and react for 8 - 12 h.

[0016] B3: After the reaction in step B2 is completed, cool to room temperature, filter by suction, wash the filter cake with absolute ethanol and deionized water, and dry it under vacuum at 60 - 70 °C to obtain salicylaldehyde thiosemicarbazide triazine.

[0017] Furthermore, in step B1, the mass concentration of 5-chloromethyl salicylaldehyde in the ethanol solution of 5-chloromethyl salicylaldehyde is 40 - 50 mg / mL.

[0018] Further, in step B1, the mass concentration of thiosemicarbazide in the ethanol solution of thiosemicarbazide is 20 - 25 mg / mL in ethanol.

[0019] Further, in step B2, the mass concentration of cyanuric chloride in 1,4 - dioxane is 20 - 40 mg / mL.

[0020] Further, in step B2, the mass concentration of chloromethyl salicylaldehyde thiosemicarbazone in 1,4 - dioxane is 10 - 15 mg / mL.

[0021] Further, in step B2, the mass ratio of chloromethyl salicylaldehyde thiosemicarbazone to potassium carbonate is 1:3.

[0022] Further, the present invention also provides a preparation method of the renewable adsorbent for heavy metal ion removal, comprising the following steps:

[0023] S1: Under nitrogen protection, take modified loofah sponge, K2CO3 and salicylaldehyde thiosemicarbazide triazine and add them into ethyl acetate, and react at 80 °C for 24 h;

[0024] S2: After the reaction in step S1 is completed, cool to room temperature, filter by suction, wash the filter cake with deionized water and absolute ethanol, and dry it under vacuum to obtain the renewable adsorbent for heavy metal ion removal.

[0025] Further, in step S1, the dosage ratio of salicylaldehyde thiosemicarbazide triazine, K2CO3 to ethyl acetate is 1 g:2 g:20 mL.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a renewable adsorbent for heavy metal ion removal and its preparation method. Using loofah sponge as the base material, making full use of its natural three-dimensional porous structure, through chemical modification, the heavy metal ion adsorption performance and regeneration efficiency are significantly improved. The present invention grafts epoxy groups on the surface of loofah sponge using epichlorohydrin, introducing active epoxy groups on the surface of loofah sponge through epoxidation treatment, providing uniform anchoring sites for subsequent mercapto-functionalization, avoiding uneven distribution of functional groups, and undergoing a selective ring-opening reaction with pentaerythritol tetra(3-mercaptopropionate) to form a stable thioether bond connection, forming a covalent bond connection. The grafted layer is not easily detached under acidic elution conditions, providing abundant mercapto groups (-SH), and forming stable coordination bonds with heavy metal ions through soft acid-soft base; the present invention conducts a condensation reaction between 5-chloromethylsalicylaldehyde and thiosemicarbazide, reacting the aldehyde group of 5-chloromethylsalicylaldehyde with the amino group of thiosemicarbazide to form a Schiff base bond, obtaining an intermediate chloromethylsalicylaldehyde thiosemicarbazide containing a chloromethyl group and a Schiff base bond. The amino group of the intermediate undergoes a nucleophilic substitution reaction with cyanuric chloride, the -NH2 of the intermediate attacks one chlorine atom of cyanuric chloride to generate a substitution product, and the remaining active chlorine atom is used for subsequent functionalization grafting. The prepared salicylaldehyde thiosemicarbazide triazine contains a triazine ring, a Schiff base bond, and a thiosemicarbazide group, and its nitrogen, sulfur and other atoms can chelate or ion-exchange with metal ions. The remaining active chlorine atom provides a reaction site for subsequent bonding with the mercapto group of modified loofah sponge; at the same time, the hydroxyl groups of the natural cellulose skeleton of loofah sponge further enhance the capture ability of heavy metals through electrostatic adsorption. The synergistic effect of the above functional groups significantly improves the saturated adsorption capacity of the adsorbent for heavy metal ions. The salicylaldehyde thiosemicarbazide triazine of the present invention forms a covalent bridge with the mercapto group of modified loofah sponge through a nucleophilic substitution reaction, and the salicylaldehyde thiosemicarbazide triazine binds to the mercapto group on the surface of modified loofah sponge, and the chemical bonding endows the adsorbent with structural stability. The acidic eluent can protonate the mercapto group, weakening the coordination with metals, and at the same time competitively displacing the metal ions bound by the Schiff base bond. Experiments show that after 5 adsorption-desorption cycles, the removal rate of Pb²⁺ by the adsorbent is still >85%. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0029] Figure 1 It is the scanning electron microscope image of the adsorbent described in Example 1 of the present invention;

[0030] Figure 2 It is the chemical structural formula of the salicylaldehyde thiosemicarbazide triazine described in Example 1 of the present invention;

[0031] Figure 3 1H NMR spectrum of salicylaldehyde thiosemicarbazide triazine described in Example 1 of the present invention;

[0032] Figure 4 Desorption effect of the adsorbents described in Examples 1-3 and Comparative Examples 1-2 of the present invention;

[0033] Figure 5 Cycling performance of the adsorbents described in Example 1 and Comparative Examples 1-2 of the present invention. Detailed implementation manners

[0034] To make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are purchased through commercial channels.

[0035] Example 1: A renewable adsorbent for removing heavy metal ions, comprising the following raw materials in parts by weight: 15 parts of modified loofah sponge and 12 parts of salicylaldehyde thiosemicarbazide triazine.

[0036] Preparation method of the modified loofah sponge, comprising the following steps:

[0037] A1: Cut the loofah sponge into blocks of 2×2 cm in size, soak it in water, change the water every 2 h, wash it repeatedly by rubbing. After 24 h, immerse it in 5% (w / v) NaOH solution, continuously stir at 60 °C and 300 rpm for 3 h, wash it with ultrapure water until neutral, and dry it in vacuum at 80 °C to obtain pretreated loofah sponge;

[0038] A2: Add 50 g of the pretreated loofah sponge obtained in step A1 into 2500 mL of 3 mol / L NaOH solution, add 750 mL of epichlorohydrin and 500 mL of absolute ethanol, keep it in a water bath at 50 °C, stir and react for 3 h, wash it with ethanol, and dry it to obtain epoxidized loofah sponge;

[0039] A3: Under N2 protection, add 50 g of the epoxidized loofah sponge obtained in step A2 and 100 g of pentaerythritol tetra(3-mercaptopropionate) into 3000 mL of ethanol, ultrasonically disperse it at 400 W for 30 min, add 500 mL of triethylamine, stir and react at room temperature for 4 h, wash it with absolute ethanol, and dry it in vacuum to obtain the modified loofah sponge.

[0040] Preparation raw materials of salicylaldehyde thiosemicarbazide triazine, comprising the following components in parts by weight: 9 parts of 5-chloromethyl salicylaldehyde, 6 parts of thiosemicarbazide, and 3 parts of cyanuric chloride.

[0041] Preparation method of salicylaldehyde thiosemicarbazide triazine, comprising the following steps:

[0042] B1: Prepare an ethanol solution of 5-chloromethylsalicylaldehyde at a ratio of 9 g of 5-chloromethylsalicylaldehyde to 50 mg / mL, and dropwise add it to an ethanol solution of thiosemicarbazide prepared at a ratio of 6 g of thiosemicarbazide to 25 mg / mL. Heat under reflux for 5 h, cool to room temperature, filter by suction, wash the filter cake with ethanol, and dry it under vacuum at 70 °C to obtain 5-chloromethylsalicylaldehyde thiosemicarbazone;

[0043] B2: Add 3 g of cyanuric chloride to 75 mL of 1,4-dioxane and mix well to obtain a mixed solution. Mix the 5-chloromethylsalicylaldehyde thiosemicarbazone obtained in step B1 and potassium carbonate in 1,4-dioxane. The mass ratio of 5-chloromethylsalicylaldehyde thiosemicarbazone to potassium carbonate is 1:3, and the mass concentration of 5-chloromethylsalicylaldehyde thiosemicarbazone in 1,4-dioxane is 15 mg / mL. Add the mixed solution dropwise under an ice-water bath, stir evenly, and heat to 90 °C for 12 h;

[0044] B3: After the reaction in step B2 is completed, cool to room temperature, filter by suction, wash the filter cake with absolute ethanol and deionized water, and dry it under vacuum at 70 °C to obtain salicylaldehyde thiosemicarbazone triazine.

[0045] This example also provides a preparation method of the renewable adsorbent for removing heavy metal ions, including the following steps:

[0046] S1: Under nitrogen protection, take 15 g of modified loofah sponge, 24 g of K2CO3 and 12 g of salicylaldehyde thiosemicarbazone triazine, add them to 240 mL of ethyl acetate, and react at 80 °C for 24 h;

[0047] S2: After the reaction in step S1 is completed, cool to room temperature, filter by suction, wash the filter cake with deionized water and absolute ethanol, and dry it under vacuum to obtain a renewable adsorbent for removing heavy metal ions.

[0048] Example 2: A renewable adsorbent for removing heavy metal ions, including the following raw materials in parts by weight: 10 parts of modified loofah sponge, 8 parts of salicylaldehyde thiosemicarbazone triazine.

[0049] The preparation method of the modified loofah sponge includes the following steps:

[0050] A1: Cut the loofah sponge into blocks of 2×2 cm, soak it in water, change the water every 2 h, rub it repeatedly. After 24 h, immerse it in a 5% (w / v) NaOH solution, stir continuously at 60 °C and 200 rpm for 3 h, wash it with ultrapure water until neutral, and dry it under vacuum at 80 °C to obtain pretreated loofah sponge;

[0051] A2: Add 20 g of the pretreated loofah sponge obtained in step A1 into 1000 mL of 3 mol / L NaOH solution, add 300 mL of epichlorohydrin and 200 mL of absolute ethanol, keep it in a constant temperature water bath at 50 °C, stir and react for 3 h, wash it with ethanol, and dry it to obtain epoxidized loofah sponge;

[0052] A3: Under N2 protection, add 20 g of the epoxidized loofah sponge obtained in step A2 and 40 g of pentaerythritol tetra(3-mercaptopropionate) into 800 mL of ethanol, ultrasonically disperse it at 300 W for 20 min, add 120 mL of triethylamine, stir and react at room temperature for 3 h, wash it with absolute ethanol, and dry it under vacuum to obtain modified loofah sponge.

[0053] The preparation raw materials of salicylaldehyde thiosemicarbazide triazine include the following components in parts by weight: 6 parts of 5-chloromethylsalicylaldehyde, 4 parts of thiosemicarbazide, and 2 parts of cyanuric chloride.

[0054] The preparation method of salicylaldehyde thiosemicarbazide triazine includes the following steps:

[0055] B1: Prepare an ethanol solution of 5-chloromethylsalicylaldehyde at a ratio of 6 g of 5-chloromethylsalicylaldehyde to 40 mg / mL, and dropwise add it to an ethanol solution of thiosemicarbazide prepared at a ratio of 4 g of thiosemicarbazide to 20 mg / mL, heat and reflux for 4 h, cool to room temperature, filter by suction, wash the filter cake with ethanol, and dry it under vacuum at 60 °C to obtain chloromethylsalicylaldehyde thiosemicarbazone;

[0056] B2: Add 2 g of cyanuric chloride into 100 mL of 1,4-dioxane and mix well to obtain a mixed solution. Mix the chloromethylsalicylaldehyde thiosemicarbazone obtained in step B1 and potassium carbonate in 1,4-dioxane. The mass ratio of chloromethylsalicylaldehyde thiosemicarbazone to potassium carbonate is 1:3, and the mass concentration of chloromethylsalicylaldehyde thiosemicarbazone in 1,4-dioxane is 10 mg / mL. Dropwise add the mixed solution under an ice-water bath, stir evenly, heat to 80 °C, and react for 8 h;

[0057] B3: After the reaction in step B2 is completed, cool to room temperature, filter by suction, wash the filter cake with absolute ethanol and deionized water, and dry it under vacuum at 60 °C to obtain salicylaldehyde thiosemicarbazide triazine.

[0058] This example also provides a preparation method of the renewable adsorbent for heavy metal ion removal, including the following steps:

[0059] S1: Under nitrogen protection, take 10 g of modified loofah sponge, 16 g of K2CO3 and 8 g of salicylaldehyde thiosemicarbazide triazine, add them into 160 mL of ethyl acetate, and react at 80 °C for 24 h;

[0060] S2: After the reaction in step S1 is completed, cool to room temperature, perform suction filtration, wash the filter cake with deionized water and absolute ethanol, and dry it under vacuum to obtain a renewable adsorbent for heavy metal ion removal.

[0061] Example 3: A renewable adsorbent for heavy metal ion removal, comprising the following raw materials in parts by weight: 12 parts of modified loofah sponge and 10 parts of salicylaldehyde thiosemicarbazide triazine.

[0062] The preparation method of the modified loofah sponge comprises the following steps:

[0063] A1: Cut the loofah sponge into blocks of 2×2 cm in size, soak it in water, change the water every 2 h, wash it repeatedly by rubbing, after 24 h, immerse it in a 5% (w / v) NaOH solution, stir continuously at 60 °C and 250 rpm for 3 h, wash it with ultrapure water until neutral, and dry it under vacuum at 80 °C to obtain pretreated loofah sponge;

[0064] A2: Add 30 g of the pretreated loofah sponge obtained in step A1 into 1500 mL of a 3 mol / L NaOH solution, add 450 mL of epichlorohydrin and 300 mL of absolute ethanol, keep the temperature in a water bath at 50 °C, stir and react for 3 h, wash it with ethanol, and dry it to obtain epoxidized loofah sponge;

[0065] A3: Under N2 protection, add 30 g of the epoxidized loofah sponge obtained in step A2 and 60 g of pentaerythritol tetra(3-mercaptopropionate) into 1500 mL of ethanol, disperse it by ultrasonic wave at 350 W for 25 min, add 240 mL of triethylamine, stir and react at room temperature for 3.5 h, wash it with absolute ethanol, and dry it under vacuum to obtain modified loofah sponge.

[0066] The preparation raw materials of salicylaldehyde thiosemicarbazide triazine comprise the following components in parts by weight: 7.2 parts of 5-chloromethylsalicylaldehyde, 4.8 parts of thiosemicarbazide, and 2.5 parts of cyanuric chloride.

[0067] The preparation method of salicylaldehyde thiosemicarbazide triazine comprises the following steps:

[0068] B1: Prepare an ethanol solution of 5-chloromethylsalicylaldehyde at a ratio of 7.2 g of 5-chloromethylsalicylaldehyde per 48 mg / mL and dropwise add it to an ethanol solution of thiosemicarbazide prepared from 4.8 g of thiosemicarbazide at 24 mg / mL, heat under reflux for 4.5 h, cool to room temperature, perform suction filtration, wash the filter cake with ethanol, and dry it under vacuum at 65 °C to obtain chloromethylsalicylaldehyde thiosemicarbazone;

[0069] B2: Add 2.5 g of cyanuric chloride to 100 mL of 1,4-dioxane and mix well to obtain a mixed solution. Add the chloromethyl salicylaldehyde thiosemicarbazone obtained in step B1 and potassium carbonate to 1,4-dioxane and mix well. The mass ratio of chloromethyl salicylaldehyde thiosemicarbazone to potassium carbonate is 1:3, and the mass concentration of chloromethyl salicylaldehyde thiosemicarbazone in 1,4-dioxane is 12 mg / mL. Dropwise add the mixed solution under an ice-water bath, stir evenly, heat to 85 °C, and react for 10 h;

[0070] B3: After the reaction in step B2 is completed, cool to room temperature, filter by suction, wash the filter cake with absolute ethanol and deionized water, and dry in vacuo at 65 °C to obtain salicylaldehyde thiosemicarbazone triazine.

[0071] This example also provides a preparation method of the renewable adsorbent for heavy metal ion removal, including the following steps:

[0072] S1: Under nitrogen protection, take 12 g of modified loofah sponge, 20 g of K2CO3 and 10 g of salicylaldehyde thiosemicarbazone triazine, add them to 200 mL of ethyl acetate, and react at 80 °C for 24 h;

[0073] S2: After the reaction in step S1 is completed, cool to room temperature, filter by suction, wash the filter cake with deionized water and absolute ethanol, and dry in vacuo to obtain a renewable adsorbent for heavy metal ion removal.

[0074] The difference between Comparative Example 1 and Example 1 is only that salicylaldehyde thiosemicarbazone triazine is not added, that is, modified loofah sponge is used to replace the renewable adsorbent.

[0075] The difference between Comparative Example 2 and Example 1 is only that pretreated loofah sponge is used to replace the renewable adsorbent.

[0076] Experimental Example 1: Observe the renewable adsorbent prepared in Example 1 by scanning electron microscope, and the scanning electron micrograph is as Figure 1 shown. Figure 1 The results show that the adsorbent of the present invention retains the natural three-dimensional porous framework structure of the loofah sponge, the fiber surface is relatively rough, and there are grooves, which is beneficial to the adsorption of heavy metal pollutants.

[0077] Experimental Example 2: Prepare salicylaldehyde thiosemicarbazone triazine according to the method of Example 1, and its chemical structural formula is as Figure 2 shown, Figure 2 The results show that the aldehyde group of 5-chloromethyl salicylaldehyde reacts with the amino group of thiosemicarbazide to form a Schiff base reaction, 5-chloromethyl salicylaldehyde and thiosemicarbazide are covalently bonded, and chloromethyl salicylaldehyde thiosemicarbazone is prepared. The obtained product contains an amino group and reacts with the chlorine atom group of cyanuric chloride. Chloromethyl salicylaldehyde thiosemicarbazone replaces the chlorine atom in cyanuric chloride to prepare salicylaldehyde thiosemicarbazone triazine. The nuclear magnetic resonance hydrogen spectrum is asFigure 3 as shown 1 1H NMR (300 MHz, DMSO-d6), chemical shift δ: 11.67 (3H), 11.55 (3H), 11.11 (3H), 8.74 (3H), 7.69 (3H), 7.22 (3H), 6.95 (3H), 4.64 (6H).

[0078] Experimental Example 3: Take 20 mL of a simulated wastewater sample with an initial lead ion concentration of 200 mg / L, add 10 mg of the renewable adsorbents of Examples 1-3 and Comparative Examples 1-2, shake and adsorb at 180 r / min at room temperature for 6 h, take the supernatant to measure the concentration of lead ions, and calculate the adsorption capacity. The results are as Figure 4 shown

[0079] Figure 4 The results show that the adsorption capacities and adsorption rates of the adsorbents in the groups of Examples 1-3 for lead ions are significantly higher than those in Comparative Examples 1-2. Among them, in Comparative Example 1, only modified loofah sponge is used as the adsorbent, and salicylaldehyde aminothiourea triazine is not grafted. In Comparative Example 2, pretreated loofah sponge is used as the adsorbent. In Comparative Examples 1-2, the groups capable of coordinating with heavy metals are significantly reduced, and the adsorption performance for heavy metal ions decreases.

[0080] Experimental Example 4: Dry the adsorbent after adsorption reaches saturation, prepare an HAC solution with a concentration of 0.1 mol / L, add 20 mg of the adsorbent that has reached the saturated adsorption capacity, shake at 180 r / min at room temperature for 6 h, rinse with distilled water and dry, perform desorption, conduct 5 cycles of adsorption-desorption tests, and calculate the removal rate of lead ions after each adsorption of lead ions. The results are as Figure 5 shown

[0081] Figure 5 The results show that the adsorbent prepared in Example 1 can maintain a removal rate of more than 85% for lead ions after 5 adsorption-desorption cycles. After cycling, the removal rates in Comparative Examples 1-2 decrease significantly compared with Example 1. Due to the lack of active sites in Comparative Examples 1-2, after multiple uses, the original sites are passivated, and their cycling ability decreases rapidly, and the cycling stability decreases.

[0082] Those of ordinary skill in the art should understand that: The discussion of any above embodiment is only exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, and they are not provided in detail for the sake of brevity.

Claims

1. A regenerable adsorbent for heavy metal ion removal, characterized in that: The method comprises the following raw materials in parts by weight: 10-15 parts of modified loofah sponge and 8-12 parts of salicylaldehyde thiosemicarbazide triazine; The preparation method of the modified loofah comprises the following steps: A1: Soaking and scrubbing a loofah with clean water, immersing the loofah in a NaOH solution, stirring, washing, and drying to obtain a pretreated loofah; A2: Add the pretreated loofah obtained in step A1 to a NaOH solution, add epichlorohydrin and anhydrous ethanol, place in a constant temperature water bath, stir to react, wash, and dry to obtain an epoxidized loofah; A3: Under N2 protection, the epoxidized loofah obtained in step A2 and pentaerythritol tetrakis(3-mercaptopropionic acid) ester are added to ethanol, ultrasonicated, triethylamine is added, stirred for reaction, washed, and dried to obtain a modified loofah; The preparation method of salicylaldehyde thiosemicarbazide triazine comprises the following steps: B1: adding the ethanol solution of 5-chloromethyl salicylaldehyde dropwise to the ethanol solution of thiosemicarbazide, heating to reflux, cooling, suction filtering, washing, and drying to obtain chloromethyl salicylaldehyde thiosemicarbazide; B2: Add cyanuric chloride to 1,4-dioxane and mix well to obtain a mixed solution, add the chloromethyl salicylaldehyde thiosemicarbazone obtained in step B1 and potassium carbonate to 1,4-dioxane and mix well, add the mixed solution dropwise in an ice water bath, stir well, heat, and react; B3: After the reaction in step B2 is completed, the mixture is cooled to room temperature, filtered, the filter cake is washed, and dried to obtain salicylaldehyde thiosemicarbazide triazine; The method for preparing the regenerable adsorbent for removing heavy metal ions comprises the following steps: S1: Under nitrogen protection, take modified loofah, K2CO3 and salicylaldehyde aminothiourea triazine and add them to ethyl acetate for reaction; the dosage ratio of salicylaldehyde aminothiourea triazine, K2CO3 and ethyl acetate is 1 g:2 g:20 mL; S2: After the reaction in step S1 is completed, the mixture is cooled, filtered, washed and dried to obtain a regenerable adsorbent for removing heavy metal ions.

2. The regenerable adsorbent for heavy metal ion removal according to claim 1, characterized in that: In step A2, the amount ratio of the pretreated loofah, NaOH solution, epichlorohydrin and anhydrous ethanol is 1 g: 50 mL: 15 mL: 10 mL; in step A3, the amount ratio of the epoxidized loofah, pentaerythritol tetrakis(3-mercaptopropionic acid), ethanol and triethylamine is 1 g: 2 g: 40-60 mL: 6-10 mL.

3. The regenerable adsorbent for heavy metal ion removal according to claim 2, characterized in that: In step B1, the mass concentration of 5-chloromethyl salicylaldehyde in ethanol is 40-50 mg / mL; the mass concentration of thiosemicarbazide in ethanol is 20-25 mg / mL.

4. The regenerable adsorbent for heavy metal ion removal according to claim 3, characterized in that: In step B2, the mass concentration of cyanuric chloride in 1,4-dioxane is 20-40 mg / mL; the mass concentration of chloromethyl salicylaldehyde thiosemicarbazone in 1,4-dioxane is 10-15 mg / mL; and the mass ratio of chloromethyl salicylaldehyde thiosemicarbazone to potassium carbonate is 1:3.

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