CN114210311A

CN114210311A - Germanium adsorbent, preparation method and method for recovering germanium

Info

Publication number: CN114210311A
Application number: CN202111531537.7A
Authority: CN
Inventors: 赵飞平; 袁睿; 张传龙; 向鸿锐; 胡文吉豪; 柴立元; 闵小波; 林璋; 唐崇俭
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2022-03-22
Anticipated expiration: 2041-12-14
Also published as: CN114210311B

Abstract

The invention provides a preparation method of a germanium adsorbent, which comprises the following steps: s1, swelling chitosan in acetic acid solution to obtain transparent pasty swollen chitosan; s2, mixing EDC, NHS and tartaric acid, and pre-reacting at-8-2 ℃ to obtain a pre-treatment solution; s3, performing modification reaction on the pretreatment solution and the swollen chitosan, and adjusting the pH of the reaction solution to 8.5 +/-0.05 after the modification reaction is completed so as to separate the germanium adsorbent from the reaction solution. The preparation method is green and environment-friendly, is simple and convenient to operate, and has high adsorbability on germanium. Based on the preparation method, the invention also provides a germanium adsorbent and a method for recovering germanium, which are used for efficiently adsorbing and recovering germanium in waste liquid.

Description

Germanium adsorbent, preparation method and method for recovering germanium

Technical Field

The invention relates to the field of germanium recovery, in particular to a germanium adsorbent, a preparation method and a method for recovering germanium.

Background

Germanium (Ge) is a typical rare-earth element, has a relatively high melting point and a relatively brittle texture, is abundant in the earth crust by only 15 ten thousandth, and is an important semiconductor metal. The chemical property of germanium is stable, and can be chemically reacted with strong acid such as aqua regia only under heating condition, and valence electron configuration of germanium atom is 4s²p²It conforms to the copper type ion valence electron configuration. The oxides and sulfides of germanium on earth exist mainly in GeS and GeS₂GeO and GeO₂And the like. In addition, germanium has special properties in many aspects, has wide and important application in the fields of semiconductors, aerospace measurement and control, nuclear physics detection, optical fiber communication, infrared optics, solar cells, chemical catalysts, biomedicine and the like, and is an important strategic resource. Germanium is also widely used in the field of medicine, and can be used for preventing and treating cancer, and organic compounds in germanium compounds can be used as toothpaste, high-efficiency analgesic paste and the like. Therefore, germanium is now a strategic resource that is urgently needed in various countries.

However, the content of germanium in the ore is very small, and the process for extracting germanium element from the ore has high requirements and great difficulty. With the rapid development of technology, the consumption and demand of germanium are increasing day by day, but the germanium resource is lacking and the supply is not sufficient, so that the efficient recycling of germanium becomes important. The traditional germanium recovery technology, such as a precipitation method and an extraction method, has the potential of causing serious pollution to the environment, has high loss rate of extracted germanium, and has a plurality of limitations for practical application.

In order to solve the problems, chitosan is widely concerned as a biomass-based adsorption material for recovering germanium, has rich sources, is green and degradable, and has amino groups with rich structures. There have been studies to adsorb germanium using chitosan to separate and recover germanium. However, although the existing adsorption method using chitosan has simple operation, low treatment cost and wide application range, the original structure of chitosan is not particularly ideal for the recovery performance of germanium, and the adsorption efficiency is still to be improved.

In view of the above, it is desirable to provide a germanium adsorbent, a method for preparing the same, and a method for recovering germanium, which solve or at least alleviate the above-mentioned disadvantages of low germanium adsorption efficiency.

Disclosure of Invention

The invention mainly aims to provide a germanium adsorbent, a preparation method and a method for recovering germanium, and aims to solve the technical problem of low germanium adsorption efficiency.

In order to achieve the above object, the present invention provides a method for preparing a germanium adsorbent, comprising the steps of:

s1, swelling chitosan in acetic acid solution to obtain transparent pasty swollen chitosan;

s2, mixing EDC, NHS and tartaric acid, and pre-reacting at-8-2 ℃ to obtain a pre-treatment solution;

s3, performing modification reaction on the pretreatment solution and the swollen chitosan, and adjusting the pH of the reaction solution to 8.5 +/-0.05 after the modification reaction is completed so as to separate the germanium adsorbent from the reaction solution.

Further, in the step S1, the volume concentration of the acetic acid solution is 2-10%;

in the step S2, the mixing process is performed in a mixed solution of water and ethanol.

Further, in the step S1, the swelling reaction time is 1.5 to 2 hours, and the reaction temperature of the swelling reaction is 25 to 30 ℃.

Further, in the step S2, the pre-reaction is performed under an ice bath condition, and the duration of the pre-reaction is 1 to 1.5 hours;

in the step S3, the modification reaction is carried out at a temperature of 25-30 ℃, and the duration of the modification reaction is 11-13 h.

Further, the swollen chitosan: the tartaric acid: the EDC: the molar ratio of NHS is 1: 1-3: 3: 1.

further, in the step S3, the pH of the reaction liquid is adjusted to 8.5 after the modification reaction is completed.

The invention also provides a germanium adsorbent, which is prepared by adopting the preparation method of any one of the germanium adsorbents.

The invention also provides a method for recovering germanium, which comprises the following steps: mixing the germanium adsorbent of claim 7 with a germanium-containing solution to be treated, controlling the pH of the germanium-containing solution or the mixed solution to be 0.5-7, and oscillating the mixed solution to complete the adsorption of the germanium adsorbent on germanium.

Further, the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated is 0.5-2 mg: 1 mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500 mg/L.

Further, keeping the mixed solution at the temperature of 25-30 ℃, and carrying out shaking adsorption for 5min-24h at a shaking rate of 140-160 rpm.

Compared with the prior art, the invention has the following advantages:

1. the invention has higher adsorbability to germanium, chitosan is swelled by adopting acetic acid, and germanium adsorbent generated by EDC and NHS mediated tartaric acid and the chitosan are adopted, so that the invention has larger adsorbability to germanium in solution under the condition of specific pH value, and the whole adsorption process can reach balance in about 200 min; in addition, the germanium adsorbent can be stably dispersed in a solution after being subjected to specific modification, and can be regenerated and recycled; compared with the original unmodified chitosan, the adsorption capacity of the chitosan grafted and modified by tartaric acid is greatly improved, the adsorption balance time is short, and the adsorption sites are fully utilized.

2. The method is environment-friendly and simple and convenient to operate, the reagents used in the method are non-toxic, no waste liquid is discharged in the whole material synthesis and adsorption process, and no pollution is caused to the environment; in addition, the chitosan is modified and modified by tartaric acid, EDC and NHS through a simple liquid phase synthesis method, the synthesis process is simple and convenient to operate, and mass synthesis can be realized.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a reaction flow diagram illustrating a grafting process in a method for preparing a germanium adsorbent according to the present invention;

FIG. 2 is a schematic diagram of the chemical reaction of germanium sorbent in combination with germanium in accordance with the present invention;

FIG. 3 is a scanning electron micrograph of TA-CS and CS in example 1; wherein a is a 4000-fold scanning electron microscope image of CS, b is a 4000-fold scanning electron microscope image of TA-CS, and c is a 1000-fold scanning electron microscope image of TA-CS;

FIG. 4 is EDS chart of element distribution of TA-CS in example 1;

FIG. 5 is a graph showing the ratio of each element of TA-CS and CS in example 1;

FIG. 6 is a Fourier transform infrared spectrum of TA-CS and CS in example 1;

FIG. 7 is an X-ray photoelectron spectrum of TA-CS and CS in example 1;

FIG. 8 is a graph of the adsorption performance of TA-CS and CS on germanium at different acidity for example 2;

FIG. 9 is a graph of the adsorption performance of TA-CS and CS in example 2 at different germanium concentrations and their isotherm fits;

FIG. 10 is a graph showing adsorption performance of TA-CS and CS in example 2 at different adsorption times.

The implementation, functional features and advantages of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

It should be noted that all the directional indicators (such as the upper and lower … …) in the embodiment of the present invention are only used to explain the relative position relationship, movement, etc. of the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature.

Moreover, the technical solutions in the embodiments of the present invention may be combined with each other, but it is necessary to be able to be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, the combination of the technical solutions should be considered to be absent, and is not within the protection scope of the present invention.

In order to obtain a material with high adsorptivity to germanium, the invention provides a preparation method of a germanium adsorbent, which comprises the following steps:

s1, swelling chitosan in acetic acid solution to obtain transparent pasty swollen chitosan. Wherein, in the process of the swelling reaction, stirring can be continuously carried out so as to ensure that the swelling chitosan is transparent paste. The volume concentration of the acetic acid solution is 2-10%, and specifically can be 5%.

In addition, in order to fully perform the swelling reaction, the swelling reaction time can be 1.5-2 h, and the swelling reaction temperature can be 25-30 ℃.

S2, mixing EDC (1- (3-dimethylaminopropyl) -3-ethylcarbodiimide), NHS (N-hydroxysuccinimide) and tartaric acid, and pre-reacting at-8-2 ℃ to obtain a pre-treatment solution. Wherein the pre-reaction is mainly used for introducing tartaric acid onto the chitosan structure in a grafting manner, so that the modification efficiency of the chitosan is improved.

In addition, the mixing of EDC, NHS and tartaric acid may be performed in a mixed solution of water and ethanol. In order to ensure that the temperature during the reaction is around zero, the pre-reaction is carried out in an ice bath. In order to fully perform the pre-reaction, the pre-reaction time is 1-1.5 h, and the reaction time can be 1 h.

And S3, performing modification reaction on the pretreatment solution and the swollen chitosan, and adjusting the pH of the reaction solution to 8.5 +/-0.05 after the modification reaction is completed, specifically adjusting the pH to 8.5 to separate the germanium adsorbent from the reaction solution to obtain the separated germanium adsorbent.

The chemical structural formula of the germanium adsorbent is as follows:

in order to ensure the full progress of the modification reaction, the modification reaction can be carried out at a temperature of 25-30 ℃, the time duration of the modification reaction can be 11-13 h, and the reaction time duration can be 12 h.

In a preferred embodiment, the ratio of the swollen chitosan: the tartaric acid: the EDC: the molar ratio of NHS may be 1: 1-3: 3: 1. since the swollen chitosan obtained in step S1 is a transparent pasty liquid and contains acetic acid, it should be noted that the swollen chitosan in the above ratio corresponds to the amount of chitosan, and acetic acid and other substances doped in the swollen chitosan are not added in the calculation of the ratio.

In the above embodiment, the hydrogen bonds in the chitosan molecules are broken by the aqueous solution of acetic acid, so that the chitosan is swollen sufficiently and becomes a uniform liquid with a certain viscosity. The obtained swollen chitosan is not separated out and dried by alkali, but the liquid swollen chitosan is directly utilized to quantitatively carry out grafting reaction with tartaric acid by a volume equal ratio method to obtain the germanium adsorbent, so that the germanium adsorbent has uniform components and reliable quantification, and acetic acid molecules can be used as subsequent acetylation promoting reagents. The volume equivalence method is volume substitution mass, and the original solid mass of the liquid swelling chitosan is in proportion to the current liquid volume, so the original calculated mass of the solid chitosan can be substituted by the volume.

In the preparation process of the embodiment, not only is tartaric acid molecules grafted to chitosan by a chemical-mediated method, but also specific steps of chemical-mediated reaction are defined, each step is refined and is specifically carried out in the reaction process, so that the stability and the sufficiency of the reaction can be ensured, and in the pre-reaction stage, the reaction temperature needs to be ensured to be about zero, so that the stable intermediate promotes the acetylation reaction.

It should also be clear that the germanium adsorbent utilizes the good complexation characteristic of tartaric acid to germanium, and is grafted on low-cost biomass-based material chitosan as a monomer molecule, so that good adsorbent capacity can be realized as a modified adsorbent, and on the basis, the germanium adsorbent can be recycled through desorption, thereby reducing cost and being green and environment-friendly.

Referring to FIG. 1, as an illustration of the grafting process described above: the preparation method comprises the following steps of carrying out coupling reaction on complex acid (tartaric acid) containing carboxylate radicals and EDC to generate a lipid substance, wherein the application range of EDC is generally 3-5, the lipid substance generates a protonation phenomenon under an acidic condition, the product reacts with NHS to carry out electron transfer and deprotonation to generate an NHS ester substance, and an intermediate is stabilized through an ice bath, in the process, carboxylate radicals are activated and have high reactivity, an amido bond can be produced when the intermediate is fully reacted with amino-containing chitosan, and tartaric acid can be successfully grafted onto the chitosan and can be removed from the NHS. EDC and NHS are combined in the grafting process to mainly improve the coupling efficiency of the reaction, and the ice bath is mainly used for stably generating an ester intermediate in the process, so that the amide reaction is further promoted.

Based on the preparation method of the germanium adsorbent, the invention also provides the germanium adsorbent which is characterized by being prepared by adopting the preparation method of the germanium adsorbent in any embodiment mode so as to obtain a material with high adsorption effect on germanium.

As an application of the germanium adsorbent, referring to a germanium adsorption process shown in fig. 2, the invention also provides a method for recovering germanium, which comprises the following steps: the method comprises the steps of mixing the germanium adsorbent and a germanium-containing solution to be treated, controlling the pH value of the germanium-containing solution or the mixed solution to be 0.5-7, and then oscillating the mixed solution to complete adsorption of germanium by the germanium adsorbent.

Wherein, in order to improve the germanium adsorption efficiency of the germanium adsorbent, the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated can be 0.5-2 mg: 1 mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500 mg/L.

In addition, in the adsorption process, the mixed solution can be kept at the temperature of 25-30 ℃ and subjected to oscillation adsorption for 5min-24h at the oscillation rate of 140-160 rpm.

To facilitate a further understanding of the invention, reference will now be made to the following examples:

example 1

Preparation and characterization of tartaric acid modified chitosan adsorbent

(I) preparation method

1) Weighing 10g of Chitosan (CS), preparing a 5% acetic acid solution, putting 10g of chitosan into 500mL of 5% acetic acid solution for swelling for two hours, stirring by using a magnetic stirrer, and destroying intermolecular hydrogen bonds through acetic acid to form transparent pasty swelling chitosan liquid (CS-L);

2) stirring and mixing 10mL of water, 10mL of ethanol, 3.568g of EDC, 0.714g of NHS and 2.793g of tartaric acid by a magnetic stirrer, and reacting for 1h in an ice-ice bath manner to obtain a pretreatment solution;

3) taking 50mL of prepared swelling chitosan, adding the prepared pretreatment solution into 50mL of swelling chitosan, stirring and mixing through a magnetic stirrer, and keeping reacting for 12h at 30 ℃; after the reaction is finished, the pH value is adjusted to 8.5, so that the tartaric acid modified chitosan adsorbent (TA-CS) is separated out.

(II) characterization

1. SEM analysis

As shown in FIG. 3, it can be seen that the TA-CS surface is rougher and has a pore structure, so that the TA-CS has a larger specific surface area, which is beneficial to the adsorption treatment.

The distribution of elements of the TA-CS is shown with reference to fig. 4, which is converted from a color map; specifically, as shown in fig. 5, it can be seen that the ratios of C, N, O elements in CS are 94.09%, 0.46% and 5.45%, respectively, the ratios of C, N, O elements in TA-CS are 86.13%, 0.78% and 13.09%, respectively, and the ratio of oxygen elements after tartaric acid modification is significantly increased.

2. ATR analysis

As shown in FIG. 6, in the ATR spectra of CS and TA-CS, 3400cm^-1The adjacent expansion vibration absorption peaks corresponding to N-H bonds and O-H bonds in CS and TA-CS are 1070cm^-1The vicinity corresponds to the characteristic absorption peak of C-O. Compared with CS, the main characteristic peak change of TA-CS and CS is embodied in 1000-2000 cm^-1Range, 1620cm^-1And 1380cm^-1And the nearby stretching vibration peak is attributed to the amido bond in the tartaric acid grafted chitosan, which indicates that the tartaric acid and the chitosan are successfully compounded.

3. XPS analysis

As shown in FIG. 7, FIG. 7 is a general X-ray photoelectron spectroscopy chart of the tartaric acid-modified chitosan adsorbent and the unmodified chitosan adsorbent in example 1. In the C1s diagram of TA-CS, from the fitting results, bonds formed between carbon element and other elements in TA-CS include three types, i.e., 287.69eV is C ═ O, 285.99eV is C — O, and 284.51eV is C — C; the bonds formed between nitrogen and other elements in TA-CS include two, i.e., 401.16eV is-NH⁺ ₃398.97eV is-NH₂。

-NH of TA-CS compared to original CS₂Peak area ratio of-NH of unmodified chitosan₂The peak area is small, and the relative peak area of the C ═ O bond is increased, analysis is probably due to the fact that the density of the C ═ O bond is increased by an amido bond, and tartaric acid is successfully introduced to the chitosan structure in a grafting mode.

The peak areas of the respective peaks are specifically shown in the following table:

example 2

Study on adsorption performance of TA-CS and CS on germanium

Under optimized experimental conditions, preparing a germanium ion solution with the concentration of 1000mg/L, diluting the germanium ion solution to different concentrations (0.5-500mg/L) in a gradient manner, and using HNO₃And NaOH solution to adjust the pH to the desired value (0.5-7). The pH testing instrument is a pH meter (pHS-3G, Shanghai Leimao); the germanium ion concentration is analyzed and measured by an ICP-OES measuring instrument, 3 different adsorption waveband values are taken, and the minimum value of RSDs is selected as data reference.

1. Study on adsorption performance of TA-CS and CS on germanium at different pH values

Fixing the initial germanium concentration to 30mg/L, mixing 7mg of TA-CS and 7mg of CS with 7mL of aqueous solution containing germanium ions respectively, fixing the adsorption temperature to 30 ℃, and oscillating for 24h in an oscillation box of 150 r/min.

As shown by the corresponding relationship between pH and adsorption capacity in FIG. 8, it can be seen that TA-CS has a low adsorption performance on germanium, less than 5mg/g, under peracid or neutral conditions. At pH 0.5-3, the adsorption capacity increased with increasing pH and reached a maximum of 28.19mg/g at pH 3. For CS, the adsorption effect on germanium ions is better under the over-acidic condition and reaches the maximum value at the pH value of 2, analysis is probably that the adsorption on germanate ions is promoted due to the fact that the protonation effect of amino groups on the chitosan structure is intensified under the acidic condition, and the saturated adsorption quantity of CS on germanium is 6.38mg/g under the pH value of 3.

2. Study on adsorption performance of TA-CS and CS on germanium under different germanium concentrations

The pH of the initial germanium solution was fixed at 3, and 7mg of TA-CS and 7mg of CS were each mixed with 7mL of an aqueous solution containing germanium ions, and the mixture was shaken in a shaking chamber at 150r/min at a fixed adsorption temperature of 30 ℃ for 24 hours.

As shown in FIG. 9, data of adsorbing germanium (0.5-500mg/L) with different concentrations by using TA-CS and CS are shown, and it should be noted that in FIG. 9, CS langmuir setting in the figure corresponds to the position relationship of CS in the figure, and TA-CS langmuir setting in the figure corresponds to the position relationship of TA-CS in the figure.

When the concentration of the germanium solution is 0-200mg/L, the adsorption capacity of the TA-CS is increased along with the increase of the concentration of the germanium solution, the TA-CS reaches a saturation state at 200mg/L, the concentration is continuously increased to 500mg/L, and the adsorption capacity of the TA-CS is not increased any more. Fitting is carried out on adsorption isotherms of TA-CS and CS, and fitting data are shown in the following table, the result shows that TA-CS reaches the maximum adsorption capacity of 53.42mg/g, which is about 13 times of original unmodified chitosan (4.04mg/g), the adsorption performance of chitosan on germanium is greatly improved through tartaric acid modification, and the material has good application performance on germanium recovery.

3. Study on adsorption performance of TA-CS and CS on germanium under different adsorption times

Fixing the initial germanium concentration to 30mg/L, adjusting the pH of the initial germanium solution to 3, mixing 7mg of TA-CS and 7mg of CS with 7mL of aqueous solution containing germanium ions respectively, fixing the adsorption temperature to 30 ℃, and oscillating and adsorbing in an oscillation box at 150 r/min.

As shown in FIG. 10, adsorption experiments of TA-CS and CS on germanium were performed at different reaction times (0.5, 1, 2, 5, 10, 30, 60, 240, 480, 960, and 1440 min). The adsorption of TA-CS to germanium is rapidly increased in the first 240min, and the adsorption quantity is basically unchanged from 240min to 1440min, so that the dynamic equilibrium of adsorption reaction is achieved. The maximum adsorption capacity of TA-CS to germanium is 25mg/g, in the initial stage of adsorption, a plurality of adsorption sites on the surface of TA-CS are rapidly occupied by germanium ions, solvent diffusion is shown, then germanium is continuously adsorbed through various actions such as complex coordination and ion exchange, and finally the adsorption equilibrium sites are reached in 240 min.

In the above technical solutions, the above are only preferred embodiments of the present invention, and the technical scope of the present invention is not limited thereby, and all the technical concepts of the present invention include the claims of the present invention, which are directly or indirectly applied to other related technical fields by using the equivalent structural changes made in the content of the description and the drawings of the present invention.

Claims

1. A preparation method of a germanium adsorbent is characterized by comprising the following steps:

2. The method according to claim 1, wherein in step S1, the acetic acid solution has a volume concentration of 2 to 10%;

3. The method of claim 1, wherein in step S1, the swelling reaction time is 1.5-2 h, and the swelling reaction temperature is 25-30 ℃.

4. The method for preparing the germanium adsorbent according to claim 1, wherein in the step S2, the pre-reaction is performed under ice bath conditions, and the pre-reaction time is 1-1.5 h;

5. The method of claim 1, wherein the swelling chitosan: the tartaric acid: the EDC: the molar ratio of NHS is 1: 1-3: 3: 1.

6. the method according to any one of claims 1 to 5, wherein in step S3, the pH of the reaction solution is adjusted to 8.5 after the completion of the modification reaction.

7. A germanium adsorbent, which is produced by the method for producing a germanium adsorbent according to any one of claims 1 to 6.

8. A method of recovering germanium, comprising: mixing the germanium adsorbent of claim 7 with a germanium-containing solution to be treated, controlling the pH of the germanium-containing solution or the mixed solution to be 0.5-7, and oscillating the mixed solution to complete the adsorption of the germanium adsorbent on germanium.

9. The method for recovering germanium from the tartaric acid-modified chitosan adsorbent of claim 8, wherein the solid-to-liquid ratio of the germanium adsorbent to the germanium-containing solution to be treated is 0.5-2 mg: 1 mL; the concentration of germanium in the germanium-containing solution is 0.5mg/L-500 mg/L.

10. The method for recovering germanium from the tartaric acid-modified chitosan adsorbent of claim 8 or 9, wherein the mixed solution is maintained at 25-30 ℃ and is subjected to shaking adsorption at a shaking rate of 140-160 rpm for 5min-24 h.