Preparation method and application of a zirconium- and erbium-codoped aluminum-based defluorination electrode material

Abstract

The present invention belongs to the technical field of high-fluoride wastewater treatment, and relates to a preparation method and application of a zirconium- and erbium-codoped aluminum-based fluoride removal electrode material. It provides a method for preparing an aluminum-based fluoride removal material co-modified with zirconium oxide and erbium oxide, and preparing it into an electrode material through carbon nanotubes, as well as the application of this electrode material. The electrode material prepared in this application can achieve a fluoride removal efficiency of more than 90% within 60 minutes, with the fluoride ion concentration in the effluent being lower than 1 mg / L, and it is not interfered by other anions, having high selectivity and high treatment efficiency, and low operating costs. In addition, this electrode material can also well achieve fluoride ion desorption and regeneration, and has high reusability.

Description

Technical Field

[0001] The present invention relates to the technical field of high-fluoride wastewater treatment, and particularly to a preparation method and application of a zirconium-erbium co-doped aluminum-based fluoride removal electrode material. Background Art

[0002] Fluorine is an essential trace element for the human body. However, long-term excessive intake of high-fluoride water will have serious adverse effects on the gastrointestinal tract, liver, kidneys, nervous system, muscles, reproductive and immune systems, and DNA structure, and even cause skeletal fluorosis, leading to permanent disability and cancer. In addition to threatening human health, fluorine pollution also has serious harm to the ecological environment. Excessive fluorine content will inhibit the nitrification of soil and the activity of acid phosphatase, change the structure and pH of the soil protozoan community, and affect the normal growth of plants.

[0003] The drinking water standard stipulates that the fluoride concentration shall not exceed 1 mg / L. Therefore, in key control areas, the fluoride-containing wastewater generated must be reasonably treated and discharged after reaching the standard. The methods for treating fluoride-containing wastewater mainly include chemical precipitation method, coagulation precipitation method, adsorption method and crystallization method. In addition, there are also membrane separation, ion exchange and electrocoagulation methods. At present, domestic photovoltaic module production enterprises often adopt the combined use of chemical precipitation method and coagulation precipitation method to purify the water quality after mixing different sources of fluoride-containing wastewater. The most commonly used precipitant in the chemical precipitation method is calcium salt, such as lime, calcium chloride, calcium carbonate and carbide slag. The calcium salt has a good effect on fluoride removal. However, the disadvantage in actual engineering is that the calcium fluoride formed by the calcium salt and fluorine will wrap on the surface of calcium hydroxide, which is not conducive to the complete progress of the reaction, resulting in a large dosage of calcium salt (the dosage is often 3 to 4 times the theoretical value), high sludge yield and complex composition, and low calcium fluoride content and low reuse value. In addition, the effluent of the simple chemical precipitation method cannot meet the discharge standard, and generally a coagulant is needed for deep fluoride removal. The commonly used inorganic coagulants are iron salts and aluminum salts, and the organic flocculant is mostly polyacrylamide (PAM). The disadvantage of using aluminum salts is that it will introduce aluminum elements harmful to the human body and cause excessive chloride ions; while the iron salt needs to be carried out smoothly under a higher pH condition, which will increase the water treatment cost.

[0004] In recent years, the capacitive defluorination technology has developed rapidly. This technology does not require the addition of chemical agents, can avoid secondary pollution, and the electrode material can be reused, with the advantages of low long-term operation cost, low energy consumption and suitability for large-scale application. The capacitive defluorination technology is applicable to water bodies with different fluoride concentrations, can flexibly cope with various water quality conditions, has high selectivity for fluoride ions, can reduce the interference of other ions, and improve the treatment effect. However, at present, there is still a lack of capacitive defluorination electrode materials with high adsorption capacity, high defluorination efficiency and high selectivity, which hinders the further development and practical application of this technology.

[0005] Chinese Invention Patent CN103641201A (Publication Date: March 19, 2014) discloses a preparation method of a lanthanum-loaded electrode for defluorination of drinking water and a defluorination electrode. The composite electrode prepared by this invention has strong defluorination adsorption capacity, high strength, does not break after long-term use, has small mass loss, no dissolution, no secondary pollution problems, and is safe and reliable.

[0006] Chinese Invention Patent CN107324459A (Publication Date: November 7, 2017) discloses a preparation method of a fishbone charcoal defluorination electrode. The main component of the fishbone charcoal in this invention is hydroxyapatite and it has a porous structure, and can remove fluorine by means of ion exchange, adsorption, dissolution precipitation, etc. The fishbone charcoal defluorination electrode can effectively remove fluoride ions with low energy consumption.

[0007] Although the above-mentioned prior arts can effectively improve the defluorination efficiency to a certain extent, they do not completely solve the problems of low adsorption capacity, poor selectivity, and high effluent concentration existing in the existing defluorination electrodes. Based on this, the present invention provides a preparation method and application of a zirconium-erbium co-doped aluminum-based defluorination electrode material to overcome the shortcomings of the prior art. Summary of the Invention

[0008] To solve the above-mentioned shortcomings of the prior art, the present application provides a preparation method and application of a zirconium-erbium co-doped aluminum-based defluorination electrode material, and the specific technical solutions are described as follows.

[0009] A preparation method of a zirconium-erbium co-doped aluminum-based defluorination electrode material includes the following steps:

[0010] Step S1: Prepare ZrO2-ErAlO2 / Al2O3 composite material;

[0011] Step S2: Prepare ZrO2-ErAlO2 / Al2O3 / CNT powder;

[0012] Step S3: Prepare electrode material.

[0013] Further, the step S1 includes the following steps;

[0014] Step S11: Mix α-Al2O3, Er2O3 and ZrO2 powders and ball mill them in agate medium using a planetary ball mill for 1-2 h;

[0015] Step S12: Calcinate the powder mixture obtained in step S11 and conduct a second grinding to eliminate possible agglomeration to obtain ZrO2-ErAlO2 / Al2O3 composite material.

[0016] Further, step S2 is specifically as follows: Mix the ZrO2-ErAlO2 / Al2O3 composite material and CNT in an excessive ethanol solution, fully stir and ultrasonically treat them, and then dry the ethanol at a high temperature to obtain ZrO2-ErAlO2 / Al2O3 / CNT powder; the excessive ratio of the ethanol solution to the mixture is 1.5 to 2.

[0017] Further, in step S11: The mass ratio of the α-Al2O3 and Er2O3 powders is 4 to 4.5:1, and the mass ratio of the Er2O3 and ZrO2 powders is 1:1 to 1.5.

[0018] Further, in step S12, the calcination conditions are: the temperature is 1200 to 1500 °C, and the time is 9 to 11 h.

[0019] Further, the mass ratio of the ZrO2-ErAlO2 / Al2O3 composite material and CNT is 1:10 to 100.

[0020] Further, the stirring time is 2 to 4 h, the ultrasonic treatment time is 2 to 3 h, and the temperature for drying the ethanol is 80 to 90 °C.

[0021] Further, step S3 is specifically as follows: Press the ZrO2-ErAlO2 / Al2O3 / CNT powder obtained in step S2 onto a titanium mesh using a roller press to prepare an electrode material.

[0022] The present invention also provides an aluminum-based defluorination electrode material prepared by the above-mentioned preparation method.

[0023] The present invention also provides an application of the above-mentioned aluminum-based defluorination electrode material in promoting fluoride ion desorption and regeneration.

[0024] Compared with the prior art, the advantages and effects of this application are as follows:

[0025] 1. The present invention provides an aluminum-based defluorination material co-modified with zirconia and erbium oxide, which is prepared into an electrode material through carbon nanotubes. This electrode material can achieve a defluorination efficiency of more than 90% within 60 min, has a high adsorption capacity and defluorination efficiency, the fluoride ion concentration in the effluent is lower than 1 mg / L, is not interfered by other anions, has high selectivity and high treatment efficiency, excellent electrical conductivity, and low operating cost.

[0026] 2. The aluminum-based defluorination electrode material provided by the present invention can well achieve fluoride ion desorption and regeneration, has little performance degradation after repeated use, and the surface modification and structure can reduce the attachment of organic substances or impurities, and has high repeated utilization performance.

[0027] 3. The preparation method of the zirconium-erbium co-doped aluminum-based defluorination electrode material provided by the present invention is environmentally friendly, the required raw materials are easily obtainable, the synthesis process is simple, suitable for large-scale production, and takes into account both performance and economy.

[0028] The above description is only an overview of the technical solution of this application. In order to be able to understand the technical means of this application more clearly, so as to be implemented in accordance with the content of the specification, and in order to make the above and other purposes, features and advantages of this application more obvious and understandable, the following takes the preferred embodiments of this application and combines with the drawings to describe in detail as follows.

[0029] According to the following detailed description of the specific embodiments of this application in combination with the drawings, those skilled in the art will understand the above and other purposes, advantages and features of this application more clearly. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of this application. For those skilled in the art, without creative efforts, other drawings can also be obtained according to these drawings. In all the drawings, similar elements or parts are generally marked with similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to actual scale.

[0031] Wherein:

[0032] Figure 1 is the microscope image of the ZrO2-ErAlO2 / Al2O3 crystal structure;

[0033] Figure 2 is the XRD pattern of the mixture of α-Al2O3, Er2O3 and monoclinic ZrO2 before and after calcination;

[0034] Figure 3 is the bar chart of the defluorination efficiency of ZrO2-ErAlO2 / Al2O3 at different calcination temperatures;

[0035] Figure 4 is the microscope image of the ZrO2-ErAlO2 / Al2O3 / CNT powder;

[0036] Figure 5 is the bar chart of the influence of the doping ratio of ZrO2-ErAlO2 / Al2O3 and CNT on the defluorination efficiency;

[0037] Figure 6 is the line chart of the defluorination efficiency of different electrode materials changing with time;

[0038] Figure 7It is a line graph showing the influence of different anions on the defluorination efficiency;

[0039] Figure 8 It is a schematic diagram of the recycling and regeneration performance of an aluminum-based defluorination electrode material. Detailed implementation manners

[0040] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. In the following description, specific details such as specific configurations and components are provided only to assist in a comprehensive understanding of the embodiments of the present application. Therefore, those skilled in the art should understand that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the present application. In addition, descriptions of known functions and structures are omitted for clarity and conciseness.

[0041] It should be understood that the "one embodiment" or "this embodiment" mentioned throughout the specification means that a specific feature, structure or characteristic related to the embodiment is included in at least one embodiment of the present application. Therefore, the "one embodiment" or "this embodiment" that appears throughout the specification does not necessarily refer to the same embodiment. In addition, these specific features, structures or characteristics can be combined in one or more embodiments in any suitable manner.

[0042] In addition, the present application may repeat reference numerals and / or letters in different examples. This repetition is for the purpose of simplicity and clarity and does not in itself indicate the relationship between the various embodiments and / or settings discussed.

[0043] The term "and / or" in this document is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A exists alone, B exists alone, and A and B exist simultaneously. The term " / and" in this document is a description of another association object relationship, indicating that two relationships can exist. For example, A / and B can represent: A exists alone, and A and B exist alone. In addition, the character " / " in this document generally indicates that the associated objects before and after are in an "or" relationship.

[0044] The term "at least one" in this document is merely a description of the association relationship of associated objects, indicating that three relationships can exist. For example, at least one of A and B can represent: A exists alone, A and B exist simultaneously, and B exists alone.

[0045] It should also be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion.

[0046] Example 1

[0047] This example introduces a preparation method of a zirconium-erbium co-doped aluminum-based defluorination electrode material, which includes the following steps:

[0048] Step S1: Prepare ZrO2-ErAlO2 / Al2O3 composite material;

[0049] Step S2: Prepare ZrO2-ErAlO2 / Al2O3 / CNT powder;

[0050] Step S3: Prepare the electrode material.

[0051] Preferably, the step S1 includes the following steps;

[0052] Step S11: Mix α-Al2O3, Er2O3 and ZrO2 powders and ball mill them in agate medium using a planetary ball mill for 1-2 h;

[0053] Step S12: Calcinate the powder mixture obtained in step S11 and perform secondary grinding to eliminate possible caking, to obtain ZrO2-ErAlO2 / Al2O3 composite material.

[0054] Preferably, the step S2 is specifically: Mix the ZrO2-ErAlO2 / Al2O3 composite material and CNT in an excessive ethanol solution, after sufficient stirring and ultrasonic treatment, then dry the ethanol at high temperature to obtain ZrO2-ErAlO2 / Al2O3 / CNT powder; wherein the excessive ratio of the ethanol solution to the mixture is 1.5-2.

[0055] Preferably, in step S11: The mass ratio of the α-Al2O3 and Er2O3 powders is 4-4.5:1, and the mass ratio of the Er2O3 and ZrO2 powders is 1:1-1.5.

[0056] Preferably, in the step S12, the calcination conditions are: the temperature is 1200-1500 °C and the time is 9-11 h.

[0057] Preferably, the mass ratio of the ZrO2-ErAlO2 / Al2O3 composite material and CNT is 1:10-100.

[0058] Preferably, the stirring time is 2 - 4 h, the ultrasonic treatment time is 2 - 3 h, and the temperature for drying ethanol is 80 - 90 °C.

[0059] Preferably, step S3 is specifically as follows: Press the ZrO2-ErAlO2 / Al2O3 / CNT powder obtained in step S2 onto a titanium mesh using a roll press to prepare an electrode material.

[0060] The technical effect achieved in this embodiment is as follows: This embodiment provides an aluminum-based defluorination material co-modified with zirconia and erbium oxide. An electrode material is prepared through carbon nanotubes. This electrode material can achieve a defluorination efficiency of over 90% within 60 min, the fluoride ion concentration in the effluent is lower than 1 mg / L, and it is not interfered by other anions, having high selectivity, high treatment efficiency, and low operating cost.

[0061] Example 2

[0062] Based on the above Example 1, this example introduces a preparation method of ZrO2-ErAlO2 / Al2O3 with a specific ratio, including the following steps:

[0063] Step S11: Mix 65.9 mol% of α-Al2O3, 15.5 mol% of Er2O3, and 18.6 mol% of ZrO2 powders and ball mill them in agate medium using a planetary ball mill for 1 h; among them, the α-Al2O3, Er2O3, and ZrO2 powders are all high-purity commercial powders with a purity of 99.99%.

[0064] Step S12: Calcinate the powder mixture obtained in step S11 and perform secondary grinding to eliminate possible caking to obtain a ZrO2-ErAlO2 / Al2O3 composite material; for its crystal structure and morphology, please refer to the appendix Figure 1 ,

[0065] Preferably, in step S12, the calcination conditions are: the temperature is 1200 - 1500 °C and the time is 10 h. It can be seen from the appendix Figure 2 that before calcination, both Er2O3 and monoclinic ZrO2 exist in the form of independent crystal structures. After calcination, monoclinic ZrO2 is transformed into cubic ZrO2, and Er2O3 and α-Al2O3 form a eutectic crystal ErAlO2; at the same time, it can be seen from the appendix Figure 3 that the ZrO2-ErAlO2 / Al2O3 obtained by calcination at 1400 °C has the highest defluorination efficiency, that is, 1400 °C is the optimal calcination temperature.

[0066] Example 3

[0067] Based on the above-mentioned Embodiments 1 and 2, this embodiment further introduces a preparation method of an aluminum-based defluorination electrode material, specifically: mixing ZrO2-ErAlO2 / Al2O3 composite material and CNT in mass ratios of 1:10, 1:20, 1:50, and 1:100 in an excessive ethanol solution, where the excessive ratio of the ethanol solution to the mixture is 1.5 - 2, then fully stirring for 2 h and performing ultrasonic treatment for 2 h, and then drying the ethanol at 80 °C to obtain ZrO2-ErAlO2 / Al2O3 / CNT powder. For its morphological structure, please refer to the appendix Figure 4 Press the ZrO2-ErAlO2 / Al2O3 / CNT powder on the titanium mesh using a roller press to prepare the electrode material.

[0068] Please refer to the appendix Figure 5 , it can be seen that when the mass ratio of the ZrO2-ErAlO2 / Al2O3 composite material to CNT is 1:20, the defluorination efficiency of the obtained ZrO2-ErAlO2 / Al2O3 / CNT powder is the highest, that is, the optimal mass ratio when the ZrO2-ErAlO2 / Al2O3 composite material and CNT are mixed is 1:20.

[0069] Embodiment 4

[0070] Based on the above-mentioned Embodiments 1 - 3, this embodiment introduces the application of a zirconium- and erbium-codoped aluminum-based defluorination electrode material. Treat the 10 mg / L fluoride-containing wastewater with this electrode material, CNT, and ZrO2-ErAlO2 / Al2O3 composite material respectively. Please refer to the appendix Figure 6 , it can be seen that the electrode material provided in this application can achieve a defluorination efficiency of more than 90% within 60 min, and the fluoride ion concentration in the effluent is less than 1 mg / L, indicating that it has a high defluorination efficiency.

[0071] This embodiment conducts an experiment on the influence of different anions on the defluorination efficiency. Please refer to the appendix Figure 7 . Under the condition of coexistence of other anions, the electrode material provided in this application can still achieve a high defluorination efficiency. Among them, the greatest interference comes from HCO3- ions, and the fluoride ion concentration in the effluent increases from 0.51 mg / L to 1.05 mg / L. The influence degrees of chloride ions and nitrate ions are very small, and the effluent concentration can be maintained below 1.0 mg / L, indicating that the electrode material provided in this application has good selectivity for fluoride ions and is less affected by other anions.

[0072] Please refer to the appendix Figure 8, after 100 h of continuous defluorination test using the electrode material provided in this embodiment, it is found that the defluorination efficiency has decreased, but still remains above 80%. The desorption rate of fluoride ions during the regeneration process of this electrode material can be maintained above 90%, showing good stability and regeneration ability. This experiment shows that the electrode material provided in this application can achieve fluoride ion desorption and regeneration well, and has good reuse performance.

[0073] The above are only the preferred embodiments of the present invention, and it does not limit the protection scope of the present invention. For those skilled in the art, various changes and modifications can be made to the present invention. Any changes, modifications, substitutions, integrations, and parameter changes made to these embodiments by means of conventional substitutions or capable of achieving the same functions without departing from the principle and spirit of the present invention fall within the protection scope of the present invention.

Claims

1. Application of an aluminum-based defluorination electrode material in promoting fluoride ion desorption and regeneration, characterized in that, A preparation method of a zirconium- and erbium-codoped aluminum-based fluoride-removing electrode material, comprising the following steps: Step S1: Prepare a ZrO2-ErAlO2 / Al2O3 composite material; Step S2: Mix the ZrO2-ErAlO2 / Al2O3 composite material and CNT in an excessive ethanol solution, stir and ultrasonically treat it, and then dry the ethanol at a high temperature to obtain ZrO2-ErAlO2 / Al2O3 / CNT powder; the mass ratio of the ZrO2-ErAlO2 / Al2O3 composite material to CNT is 1:20; Step S3: Prepare the electrode material; The said Step S1 includes the following steps; Step S11: Mix α-Al2O3, Er2O3 and ZrO2 powders and grind them, where the mass ratio of α-Al2O3 to Er2O3 powders is 4-4.5:1, and the mass ratio of Er2O3 to ZrO2 powders is 1:1-1.5; Step S12: Calcinate the powder mixture obtained in Step S11 and conduct a second grinding to obtain the ZrO2-ErAlO2 / Al2O3 composite material, where the calcination conditions are: temperature is 1400 °C and time is 9-11 h; The said electrode material has a fluoride removal rate of ≥90% for fluoride-containing wastewater with an initial concentration of 10 mg / L within 60 min, and a fluoride ion desorption rate of ≥90% after regeneration.

2. Application of an aluminum-based defluorination electrode material according to claim 1 in promoting fluoride ion desorption and regeneration, characterized in that, In the said Step S2, the excessive ratio of the ethanol solution to the mixture is 1.5-2.

3. Use of an aluminum-based defluorination electrode material according to claim 1 in promoting fluoride ion desorption and regeneration, characterized in that, In the said Step S2, the stirring time is 2-4 h, the ultrasonic treatment time is 2-3 h, and the temperature for drying the ethanol is 80-90 °C.

4. Use of an aluminum-based defluorination electrode material according to claim 1 or 3 in promoting fluoride ion desorption and regeneration, characterized in that, The said Step S3 is specifically: Press the ZrO2-ErAlO2 / Al2O3 / CNT powder obtained in Step S2 onto a titanium mesh to prepare the electrode material.

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