Phosphate adsorbent, method of preparation and use

Abstract

The present application relates to the technical field of high polymer materials, and discloses a phosphate adsorbent, a preparation method and application. The present application uses industrial waste enzymatic hydrolysis lignin for producing ethanol as a base material, uses phytic acid as a phosphate precursor, uses phenolic hydroxyl groups of the enzymatic hydrolysis lignin as active sites, combines the phytic acid and the enzymatic hydrolysis lignin through grafting means, and prepares a phosphate adsorbent. The adsorbent has uniform surface pore distribution, large specific surface area, high adsorption site density, and excellent adsorption performance. The phosphate adsorbent is used for adsorption treatment of nuclides in nuclear waste water. The adsorbent is resistant to radiation and has good selectivity, and the nuclide removal rate can reach 99%.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a phosphate adsorbent, its preparation method, and its application. Background Technology

[0002] The non-renewable nature of fossil fuels and the pollution caused by their massive consumption have forced humanity to develop new energy sources to replace traditional fossil fuels. Nuclear energy, due to its advantages such as being pollution-free and having high energy density, has been extensively studied, resulting in large quantities of radioactive nuclear wastewater. During the generation, discharge, or collection of nuclear wastewater, as well as its subsequent treatment, it may leak into the soil or be released into the atmosphere or aquatic environment through other sources of radioactive nuclides. This not only severely pollutes the environment but also threatens human health. Furthermore, recovering unused nuclides from nuclear wastewater can effectively alleviate the increasingly serious energy crisis and promote the green and sustainable development of the nuclear industry.

[0003] Currently, there are numerous research reports on the extraction, recovery, and removal of radionuclides from radioactive wastewater, including technologies such as coordination precipitation, evaporation, extraction, ion exchange, membrane separation, adsorption, and bioengineering. Among these, adsorption is considered one of the most promising and easily implemented methods for treating radioactive wastewater due to its simplicity, low cost, large processing capacity, and the availability of diverse materials. However, the core of adsorption technology is the adsorption material, and current adsorption materials used for treating radioactive wastewater still face problems such as weak radiation resistance, low selectivity, and low adsorption efficiency.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] To address the aforementioned problems, the primary objective of this invention is to provide a method for preparing a phosphate adsorbent, using industrial ethanol waste as a substrate and natural biomass phytic acid as the phosphate source, by grafting phosphate onto enzymatically hydrolyzed lignin.

[0006] The second objective of this invention is to provide a phosphate adsorbent prepared by the above method, which has a uniform pore distribution on its surface, a large specific surface area, a high density of adsorption sites, and excellent adsorption performance.

[0007] A third objective of this invention is to provide the application of the above-mentioned phosphate adsorbent in the treatment of radionuclides in radioactive wastewater.

[0008] To achieve the above-mentioned objectives of the present invention, the first technical solution of the present invention provides a method for preparing a phosphate adsorbent, comprising the following steps:

[0009] Enzymatic hydrolysis of lignin is carried out with a cross-linking agent to obtain a mixed solution of enzymatically hydrolyzed lignin.

[0010] Under a nitrogen atmosphere, an initiator was added to the above-mentioned enzymatically hydrolyzed lignin mixture to carry out the first reaction, followed by the addition of phytic acid to carry out the second reaction.

[0011] Furthermore, the amounts of each reactive component added, by weight, are as follows:

[0012] Enzymatic hydrolysis of lignin: 1-5 parts

[0013] 1-3 parts of crosslinking agent

[0014] 1-5 parts of initiator

[0015] Phytic acid 5-10 parts.

[0016] Furthermore, the crosslinking reaction is carried out at a temperature of 40 °C for 1 h.

[0017] Furthermore, the first reaction temperature is 35-40 ℃, and the reaction time is 1-2 h.

[0018] Furthermore, the second reaction temperature is 60-80 ℃, and the reaction time is 3 h.

[0019] The second technical solution of the present invention provides a phosphate adsorbent prepared according to the above preparation method.

[0020] The third technical solution of the present invention provides the application of the above-mentioned phosphate adsorbent in the treatment of radionuclides in radioactive wastewater.

[0021] Furthermore, the nuclides are cerium and lanthanum.

[0022] Furthermore, the initial pH of the radioactive wastewater is 1-5.

[0023] Furthermore, the dosage of the phosphate adsorbent is 0.02-0.1 g / L.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) The present invention uses enzymatic hydrolysis of lignin from industrial ethanol production waste as the base material and natural biomass phytic acid as the phosphate precursor to prepare phosphate adsorbent. The phenolic hydroxyl groups in the enzymatic hydrolysis of lignin are used as active sites. Phytic acid is combined with enzymatic hydrolysis of lignin by grafting, so that the phosphate in phytic acid is stably fixed on the enzymatic hydrolysis of lignin, which does not easily cause phosphorus loss and metal leaching.

[0026] (2) The phosphate adsorbent prepared by the present invention has a significantly more uniform surface pore distribution, increased specific surface area, changed chemical structure, and greatly increased adsorption site density due to the addition of phosphate. The adsorbent has excellent adsorption performance.

[0027] (3) The phosphate adsorbent prepared by the present invention is used in the treatment of radioactive nuclear wastewater. The adsorbent is radiation resistant and has good selectivity. The removal rate of nuclides can reach more than 99%, which solves the problem of low adsorption efficiency of nuclides in radioactive nuclear wastewater and is conducive to the separation and recovery of nucleic acids in nuclear wastewater. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 These are surface structure diagrams of Example 1 and the comparative sample of the present invention;

[0030] Figure 2 The diagram shows the adsorption effect of cerium and lanthanum on radioactive wastewater in Example 1 and the comparative sample of the present invention. Detailed Implementation

[0031] To better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments. The ways to implement the present invention include, but are not limited to, the following embodiments. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the test methods in the following embodiments are conventional methods.

[0032] In the embodiments of the present invention, "parts" refers to the mass parts of the corresponding substance, such as "20 parts" indicating that its mass parts are 20 parts.

[0033] The first embodiment of the present invention provides a method for preparing a phosphate adsorbent, comprising the following steps:

[0034] Enzymatic hydrolysis of lignin is carried out with a cross-linking agent to obtain a mixed solution of enzymatically hydrolyzed lignin.

[0035] Under a nitrogen atmosphere, an initiator was added to the above-mentioned enzymatically hydrolyzed lignin mixture to carry out the first reaction, followed by the addition of phytic acid to carry out the second reaction.

[0036] It should be noted that the enzymatically hydrolyzed lignin described in this invention is a waste product from the straw-based ethanol production industry. It is generally difficult to recycle and is mostly directly incinerated or discharged into the environment, wasting resources and causing environmental pollution. However, the enzymatically hydrolyzed lignin structure contains various functional groups such as aromatic groups, methoxy groups, phenolic (alcoholic) hydroxyl groups, carbonyl groups, carboxyl groups, and unsaturated double bonds. These groups can be easily introduced through reactions such as methylation, amination, nitration, and sulfonation, improving the selectivity and treatment capacity for various pollutants and demonstrating excellent application prospects in wastewater treatment. This invention uses enzymatically hydrolyzed lignin as a substrate to prepare a phosphate adsorbent, achieving sustainable development through waste-to-waste treatment.

[0037] Furthermore, it should be noted that the affinity and capacity of adsorbent materials for nuclides in water depend on the properties of the functional groups on the adsorbent surface. Based on the fundamental principles of coordination chemistry, phosphorus-containing compounds can form highly stable complexes with nuclides, potentially exhibiting good selectivity for nuclide adsorption. In fact, phosphorus-containing compounds are the most commonly used nuclide extractants, and grafting phosphorus-containing groups has a theoretical basis and application potential for improving the selective adsorption of nuclides. The phytic acid described in this invention is a saturated cyclic acid extracted from renewable plants. One phytic acid molecule can decompose into six negatively charged phosphate groups. Compared to other phosphate substances, phytic acid is a more environmentally friendly natural biomass, an environmentally friendly bio-based compound, and conforms to the carbon neutrality and development concepts. This invention achieves stable fixation of the phosphate groups in phytic acid onto enzymatically hydrolyzed lignin through a grafting reaction, minimizing phosphorus loss and metal leaching in practical applications.

[0038] Understandably, the present invention uses enzymatic hydrolysis of lignin to crosslink with a crosslinking agent to obtain an enzymatic hydrolyzed lignin mixture. The purpose of this invention is to provide crosslinkability to the enzymatic hydrolyzed lignin, so that the enzymatic hydrolyzed lignin maintains high reactivity in subsequent reactions.

[0039] In a specific embodiment, the crosslinking agent is glutaraldehyde.

[0040] Specifically, the crosslinking reaction is carried out at a temperature of 40 °C for 1 h.

[0041] Furthermore, it is understood that an initiator is first added to the enzymatic hydrolysis lignin mixture of the present invention to carry out the first reaction. The purpose of this is to generate active groups on the phenolic hydroxyl groups on the enzymatic hydrolyzed lignin, which is more conducive to the grafting reaction with phytic acid.

[0042] In a specific embodiment, the initiator is cerium ammonium nitrate.

[0043] Specifically, the first reaction temperature is 35-40 ℃, and the reaction time is 1-2 h.

[0044] In a further embodiment, the second reaction is an enzymatic process of hydrolyzing the combination of lignin and phytic acid.

[0045] Specifically, the second reaction temperature is 60-80 ℃, and the reaction time is 3 h.

[0046] In a specific embodiment, the process after the second reaction is completed includes washing and drying, by washing to remove reagents from the adsorbent and by drying to remove moisture from the surface of the adsorbent.

[0047] The second embodiment of the present invention provides a phosphate adsorbent prepared by the above preparation method. Due to the presence of phosphate, the surface pores are evenly distributed, the specific surface area is large, the adsorption potential density is high, and the adsorbent has excellent adsorption performance.

[0048] The third embodiment of the present invention provides the application of the above-mentioned phosphate adsorbent in the treatment of radionuclides in radioactive wastewater.

[0049] In a specific implementation, the nuclides are cerium and lanthanum.

[0050] It should be noted that currently, functionalized adsorbents using phytic acid as a phosphorus source have been explored for extracting radionuclides from aqueous solutions. However, in the process of treating nuclear wastewater, there are still problems such as difficulty in resisting the influence of interfering ions, and the complexity of the real environment increases the difficulty of radionuclide extraction. The phosphate adsorbent of this invention has phosphate ions stably grafted onto lignin, ensuring its selectivity and radiation resistance in radioactive nuclear wastewater, and exhibiting a high removal rate of radionuclides in radioactive nuclear wastewater.

[0051] Furthermore, it should be noted that the specific conditions for the phosphate adsorbent of the present invention to treat radionuclides in radioactive nuclear wastewater can be reasonably adjusted by those skilled in the art according to the specific conditions of the nuclear wastewater, such as the initial pH and radionuclide concentration. The present invention does not impose any special limitations, but only provides some preferred embodiments.

[0052] In a preferred embodiment, the initial pH of the radioactive wastewater is 1-5.

[0053] In a further preferred embodiment, the concentration of nuclides in the radioactive wastewater is 10-50 mg / L.

[0054] Specifically, the phosphate dosage is 0.02-0.1 g / L.

[0055] Specifically, the processing conditions are: atmospheric pressure, reaction temperature 10-60℃, reaction time 60-240 min, and rotation speed 150-250 rpm.

[0056] To make the present invention clearer, specific embodiments and comparative examples are provided below for further illustration. However, it should be understood that these embodiments are merely for more detailed illustration and should not be construed as limiting the present invention in any way.

[0057] Example 1

[0058] Dissolve 2 parts of glutaraldehyde in 150 mL of deionized water, add 3 parts of enzymatically hydrolyzed lignin while stirring, and crosslink the mixture at 40 °C for 1 h to obtain a crosslinked enzymatically hydrolyzed lignin mixture.

[0059] Under a nitrogen atmosphere, 3 parts of cerium ammonium nitrate were added to the enzymatic hydrolysis lignin mixture, and the first reaction was carried out at 37 °C for 1.5 h; then 7 parts of phytic acid were added, and the second reaction was carried out at 70 °C for 3 h. After washing and drying, phosphate adsorbent was obtained.

[0060] Example 2

[0061] Dissolve 1 part of glutaraldehyde in 100 mL of deionized water, add 1 part of enzymatically hydrolyzed lignin while stirring, and crosslink at 40 °C for 1 h to obtain a crosslinked enzymatically hydrolyzed lignin mixture.

[0062] Under a nitrogen atmosphere, 1 part of cerium ammonium nitrate was added to the enzymatic hydrolysis lignin mixture, and the first reaction was carried out at 35 °C for 2 h; then 5 parts of phytic acid were added, and the second reaction was carried out at 60 °C for 3 h. After washing and drying, the phosphate adsorbent was obtained.

[0063] Example 3

[0064] Dissolve 3 parts of glutaraldehyde in 200 mL of deionized water, add 5 parts of enzymatically hydrolyzed lignin while stirring, and crosslink at 40 °C for 1 h to obtain a crosslinked enzymatically hydrolyzed lignin mixture.

[0065] Under a nitrogen atmosphere, 5 parts of cerium ammonium nitrate were added to the enzymatic hydrolysis lignin mixture, and the first reaction was carried out at 40 °C for 1 h; then 10 parts of phytic acid were added, and the second reaction was carried out at 80 °C for 3 h. After washing and drying, the phosphate adsorbent was obtained.

[0066] Comparative Example

[0067] The enzymatic hydrolysis of lignin from industrial ethanol solid waste was provided by Nanjing Yihuan Technology Co., Ltd.

[0068] Experimental Example 1

[0069] The structural characteristics of the material were tested using a nitrogen adsorption-desorption apparatus, and the test results are as follows: Figure 1 As shown, PA-EHL is the sample of Example 1, and EHL is the comparative sample.

[0070] Depend on Figure 1The results show that the nitrogen adsorption-desorption curves of the samples in Example 1 and Comparative Example 1 belong to type IV of H3, indicating the formation of a narrow-slit porous structure. Furthermore, from... Figure 1 The built-in graph shows that the comparative sample exhibits two distinct pore size distribution peaks, at 1-5 nm and 15-20 nm, indicating that its surface pore structure is a mixture of micropores and mesopores. In contrast, the sample from Example 1 shows a broad peak in the range of 10-25 nm, indicating that its surface has a uniform mesoporous structure. Furthermore, according to... Figure 1 The BET specific surface area of ​​the two samples can be calculated using nitrogen adsorption-desorption plots. The calculated specific surface area of ​​the sample in Example 1 is 12.36 m². 2 / g, which is much higher than that of the comparative sample (specific surface area 2.35 m²). 2 The above results indicate that the incorporation of phosphate groups can effectively promote the formation of superior pore structure and high specific surface area on the lignin surface, thereby improving the adsorption performance of the adsorbent.

[0071] Experimental Example 2

[0072] At a dosage of 0.06 g / L, the samples from Example 1 and the comparative example were added to radioactive nuclear wastewater with a concentration of 20 mg / L for cerium nitrate and lanthanum nitrate, respectively. After reacting at 25 °C for 240 min, the adsorption rates of cerium and lanthanum for the two samples were measured.

[0073] Measurement method: The concentration of cerium or lanthanum in the solution was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES), and the adsorption rate was calculated according to the following formula:

[0074] ,

[0075] Where: R—adsorption rate at equilibrium (%)

[0076] C e —The concentration of cerium or lanthanum in the solution at equilibrium (mg / L).

[0077] C0 — Initial concentration of cerium or lanthanum in the solution (mg / L).

[0078] The measurement results are as follows Figure 2 As shown, PA-EHL is the sample of Example 1, and EHL is the comparative sample.

[0079] Depend on Figure 2 The experimental results show that the phosphate adsorbent in Example 1 achieved an adsorption rate of 99% for both cerium and lanthanum in radioactive wastewater, while the adsorbent in the comparative example had an adsorption rate of 41% for cerium and an even lower adsorption rate of only 24% for lanthanum.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of phosphate adsorbents in the treatment of radionuclides in radioactive wastewater, characterized in that, The nuclides are cerium and lanthanum; The preparation method of the phosphate adsorbent includes the following steps: Enzymatic hydrolysis of lignin followed by cross-linking reaction with glutaraldehyde yields a mixed solution of enzymatically hydrolyzed lignin. Under a nitrogen atmosphere, cerium ammonium nitrate was added to the above-mentioned enzymatically hydrolyzed lignin mixture to carry out the first reaction, followed by the addition of phytic acid to carry out the second reaction.

2. The application according to claim 1, characterized in that, The amounts of each reactant added, by weight, are as follows: Enzymatic hydrolysis of lignin: 1-5 parts 1-3 parts of glutaraldehyde 1-5 parts of cerium ammonium nitrate Phytic acid 5-10 parts.

3. The application according to claim 1, characterized in that, The crosslinking reaction was carried out at a temperature of 40 °C for 1 h.

4. The application according to claim 1, characterized in that, The first reaction temperature is 35-40 ℃, and the reaction time is 1-2 h.

5. The application according to claim 1, characterized in that, The second reaction temperature is 60-80 ℃, and the reaction time is 3 hours.

6. The application according to claim 1, characterized in that, The initial pH of the radioactive wastewater is 1-5.

7. The application according to claim 1, characterized in that, The dosage of the phosphate adsorbent is 0.02-0.1 g / L.

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