CN111229175A

CN111229175A - Immobilized tannin rich in rare-earth metal, preparation method and method for enriching rare-earth metal by using immobilized tannin

Info

Publication number: CN111229175A
Application number: CN202010051085.1A
Authority: CN
Inventors: 张雯雯; 陈赤清; 黄铖; 李坤; 毛业富; 冯运洋; 陈清龙; 张品德; 刘义稳; 张弘
Original assignee: Wufeng Chicheng Biotech Co ltd; Research Institute of Resource Insects of Chinese Academy of Forestry
Current assignee: Wufeng Chicheng Biotech Co ltd; Research Institute of Resource Insects of Chinese Academy of Forestry
Priority date: 2020-01-17
Filing date: 2020-01-17
Publication date: 2020-06-05
Anticipated expiration: 2040-01-17
Also published as: CN111229175B

Abstract

The invention discloses a method for enriching scattered metal immobilized tannin, a preparation method thereof and a method for enriching scattered metal by using the same. The preparation method of the immobilized tannin has the advantages of high conversion rate, strong stability of the prepared immobilized tannin rich in the scattered metal, high adsorption activity, high mechanical strength and the like, is suitable for large-scale popularization and application, reduces the cost of scattered metal enrichment, has the advantages of easiness in solid-liquid separation, insolubility and low residue in mineral acid immersion liquid and the like, has low tannin residue in the solution after adsorption and enrichment of the scattered metal ions, does not cause interference to the subsequent smelting process, and does not cause secondary pollution.

Description

Immobilized tannin rich in rare-earth metal, preparation method and method for enriching rare-earth metal by using immobilized tannin

Technical Field

The invention relates to a scattered metal-enriched tannin, a preparation method and an application method thereof, in particular to a scattered metal-enriched immobilized tannin, a preparation method thereof and a scattered metal-enriching method by using the same, belonging to the field of scattered metal preparation.

Background

Germanium (Ge), gallium (Ga) and indium (In) belong to rare dispersion metals which are also called as rare dispersion metals and are widely applied to the fields of semiconductors, optical fibers, solar panels, medicines and the like. 2015 + 2018, germanium is listed in key mineral catalogues and national strategic resources in the United states, Britain and European Union; due to the high concentration of the world distribution of germanium resources, the method has a remarkable strategic position in the competition of the future major countries. The average content of the rare metal in the earth crust is low, so that an independent rare metal deposit with independent mining value is difficult to form, the rare metal deposit is associated with other minerals in a rare dispersion state, and the rare metal deposit can be comprehensively recovered and utilized only when a main metal deposit is mined.

At present, separation and enrichment from zinc ore leachate are one of the main sources of germanium, gallium and indium, and taking smelting of germanium metal with the most content in germanium-zinc ore as an example, the main purification and enrichment methods comprise: chlorination distillation, extraction, ion exchange, tannin precipitation, etc. The tannin precipitation method has the advantages of simple and easy operation, small equipment investment, high recovery rate and the like, and is a mature and wide method applied at present. The traditional tannin germanium precipitation process adopts free tannin to form germanium, wherein the precipitation efficiency and selectivity of the gallnut tannin are good, however, the residue of the free tannin in the precipitation process not only influences the utilization efficiency of the gallnut tannin, but also causes interference to the subsequent smelting process and causes secondary pollution. The production of the gallnut tannin is relatively complex, needs to simultaneously meet a plurality of factors such as host insects, host trees, climate conditions and the like, and is limited in producing area and yield, so that the gallnut tannin has high price and large market fluctuation. In addition, germanium slag containing a large amount of tannin is difficult to recover and is mostly roasted, so that resource waste and pollution are serious. Therefore, it is significant to explore other tannin types and application forms and to reduce the application cost and pollution load.

Phyllanthus emblica is a fruit of wild plant rich in plant tannin and widely available. Emblic leafflower fruit tannin belongs to complex tannin, contains structural units of hydrolyzed tannin and condensed tannin, and has the characteristics of two kinds of tannin. Abundant hydroxyl groups of the catechol provide sufficient active sites for chelating metal ions, and the research on the precipitation of the scattered metal ions by the phyllanthus emblica tannin is not reported at home and abroad. However, the better water solubility of the emblic leafflower fruit tannin is easy to increase the residual quantity of the emblic leafflower fruit tannin in mineral acid immersion liquid after complexing germanium, and increases the pollution load while increasing the consumption.

The immobilized tannin organically combines the tannin with the high polymer material, so that the tannin has the good physical characteristics of the high polymer material and also still has the selective adsorption performance of the natural tannin on metal ions. The method takes chitosan as a substrate and glutaraldehyde as a cross-linking agent, and the emblic leafflower fruit tannin is immobilized on the chitosan to prepare the solid adsorption material which is applied to the enrichment of metal germanium in the lead-zinc ore pickle liquor.

Disclosure of Invention

The invention aims to provide a loose metal-enriched immobilized tannin, a preparation method thereof and a method for enriching the loose metal by using the immobilized tannin aiming at the technical defects in the existing wet metallurgy process of the loose metal. The immobilized tannin enriched and dispersed metal has the advantages of easy solid-liquid separation, insolubility in mineral acid immersion liquid, low residue and the like.

In order to achieve the purpose of the invention, the invention provides a preparation method of a scattered metal-enriched immobilized tannin, which comprises the steps of uniformly mixing tannin, chitosan and glutaraldehyde, and carrying out a crosslinking reaction under heating conditions, wherein the tannin is selected from emblic leafflower fruit tannin, gallnut tannin or tara tannin.

Wherein the tannin is preferably phyllanthus emblica tannin; the rare-earth metal is one or more of gallium (Ga), indium (In), germanium (Ge), selenium (Se), hoof (Te) or rhenium (Re), and preferably one or more of germanium, gallium and indium.

The immobilized tannin rich in the rare earth metal is used for adsorbing and enriching one or more of rare earth metal germanium, gallium or indium.

In particular, the reaction temperature of the crosslinking reaction is 0 to 90 ℃, preferably 20 to 80 ℃, and more preferably 55 ℃; the crosslinking reaction time is 0.5-10h, preferably 3 h.

Particularly, the weight ratio of the tannin to the chitosan is 1: (0.5-2.5), preferably 1 (1-2), more preferably 1: 1.5; the weight ratio of the glutaraldehyde to the tannin is 1 (2-16), preferably 1 (2-8), and more preferably 1: 2-4.

In particular, the pH of the reaction is controlled to be 1 to 6, preferably 2 to 6, and more preferably 3 to 4 during the crosslinking reaction.

On the other hand, the invention relates to a preparation method of the immobilized tannin rich in the rare metals, which comprises the following steps:

1) respectively adding chitosan and tannin into an acetic acid solution to prepare a chitosan-acetic acid solution and a tannin-acetic acid solution;

2) adding the tannin-acetic acid solution into the chitosan-acetic acid solution, uniformly mixing, and adding a glutaraldehyde solution; then heating to carry out crosslinking reaction;

3) the crosslinking reaction is followed by a filtration treatment after 0.5 to 10h, followed by washing the precipitated product with deionized water at least 2 times (usually 3 to 5 times); then drying the precipitate to obtain the immobilized tannin.

Wherein, the tannin in the step 1) is selected from emblic leafflower fruit tannin, gallnut tannin or tara tannin, and preferably the emblic leafflower fruit tannin.

Particularly, the mass ratio of the chitosan to the acetic acid solution in the step 1) is 1: (20-40), preferably 1: 30; the mass ratio of the tannin to the acetic acid solution is 1 (2-20), preferably 1: 10.

In particular, the concentration of the acetic acid solution in step 1) is 0.2% to 5% by mass, preferably 1% to 3% by mass, and more preferably 2% by mass.

Wherein the ratio of the mass of tannin in the tannin-acetic acid solution to the mass of chitosan in the chitosan-acetic acid solution in step 2) is 1: (0.5-2.5), preferably 1: (1-2), more preferably 1: 1.5.

In particular, the ratio of the mass of emblic leafflower fruit tannin in the tannin-acetic acid solution to the mass of chitosan in the chitosan-acetic acid solution is 1: (0.5-2.5), preferably 1: (1-2), more preferably 1: 1.5.

Wherein the mass ratio of the tannin-acetic acid solution to the chitosan-acetic acid solution in the step 2) is 1: (1.5-7.5), preferably 1:4-5, more preferably 1: 4.2-4.5.

In particular, the mass ratio of the emblic leafflower fruit tannin-acetic acid solution to the chitosan-acetic acid solution is 1: (1.5-7.5), preferably 1:4-5, more preferably 1: 4.2-4.5.

Wherein the ratio of the mass of glutaraldehyde in the glutaraldehyde solution to the mass of tannin in the tannin-acetic acid solution in step 2) is 1:2-16, preferably 1:2 to 8, and more preferably 1:2 to 4.

In particular, the ratio of the mass of glutaraldehyde in the glutaraldehyde solution to the mass of phyllanthus emblica tannin in the tannin-acetic acid solution is 1:2-16, preferably 1:2 to 8, and more preferably 1:2 to 4.

In particular, the glutaraldehyde solution has a mass percentage concentration of 0.2 to 50%, preferably 2 to 15%, and more preferably 5%.

Wherein, the pH of the reaction system is controlled to be 1-6, preferably 2-6, and more preferably 3-4 during the crosslinking reaction in the step 2).

In particular, the temperature of the crosslinking reaction is 0 to 90 ℃, preferably 20 to 80 ℃, and more preferably 55 ℃; the crosslinking reaction time is 0.5-10h, preferably 3 h.

In particular, the drying treatment in the step 3) is vacuum drying treatment, the drying temperature is less than or equal to 60 ℃, and the drying time is at least 24 hours.

In still another aspect, the present invention provides a dilute metal-enriched immobilized tannin prepared according to the above method.

Wherein the immobilized tannin is selected from immobilized emblic leafflower fruit tannin.

In another aspect, the present invention provides a method for enriching a rare earth metal, comprising adding immobilized tannin enriched with a rare earth metal to a solution containing a rare earth metal ion under stirring for adsorption treatment.

Wherein, the adsorption temperature is controlled to be less than or equal to 60 ℃ in the adsorption treatment process, preferably 20-60 ℃, more preferably 20-30 ℃, and even more preferably 30 ℃.

In particular, in the adsorption treatment, the pH of the solution containing the dilute metal ions is controlled to 1 to 5, preferably 2 to 5, and more preferably 4.0 to 4.5.

In particular, the solution containing the rare metal ions comprises Ge⁴⁺、Ga³⁺、In³⁺、Co²⁺、Mn²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Ba²⁺、Al³⁺、Fe³⁺Or Cr³⁺Plasma, preferably Ge⁴⁺、Ga³⁺、In³⁺Ions.

In particular, the adsorption treatment time is not less than 3 hours, preferably 3 to 5 hours, and more preferably 3 hours.

In particular, the concentration of each of the dilute metal ions in the solution containing the dilute metal ions is not more than 400mg/L, preferably 10 to 200mg/L, and more preferably 100 mg/L.

In particular, the solution containing the rare metal ions is the rare metal ions Ge⁴⁺、Ga³⁺、In³⁺The concentration of the ions is less than or equal to 400mg/L, preferably 10-200 mg/L.

In particular, the solution containing the rare metal ions contains the rare metal ions Ge⁴⁺The concentration of (b) is less than or equal to 400mg/L, preferably 10-200mg/L, and more preferably 100 mg/L.

Wherein the solution containing the dilute metal ions is selected from pickle liquor containing the dilute metal ions.

In particular, the pickle liquor containing the scattered metal ions is prepared according to the following steps: collecting the smoke dust after smelting metal lead in the smelting process of non-ferrous metal ores containing scattered metals, soaking the smoke dust in an acid leaching solution, keeping the pH value of the leaching solution at 2.0-4.0 in the leaching process, and then filtering to obtain the lead-free iron-based alloy.

Wherein the non-ferrous metal ore is selected from lead zinc ore, thiogenite, pyrite-ferrogermanium ore or germanite and the like; the acidic leaching solution is selected from sulfuric acid, hydrochloric acid or nitric acid, preferably sulfuric acid.

The pH value of the pickle liquor containing the scattered metal ions is 2.0-4.0, and the composition and concentration range of the metal ions are Ge⁴⁺：67-208mg/L，Ga³⁺：2-67mg/L，In³⁺：52-90mg/L，Li⁺：1-19mg/L，Na⁺：1625-1700mg/L，K⁺：990-1040mg/L，Be²⁺：0.07-0.6mg/L，Mg²⁺：930-11120mg/L，Ca²⁺：20-40mg/L，Mn²⁺：588-8065mg/L，Co²⁺：5-44mg/L，Ni²⁺：5-35mg/L，Cu²⁺：0.2-206mg/L，Zn²⁺：71232-86978mg/L，Sr²⁺：0.5-0.7mg/L，Cd²⁺：550-2297mg/L，Ba²⁺：0.1-8mg/L，Pb²⁺：18-36mg/L，Al³⁺：505-1211mg/L，Cr³⁺：5-55mg/L，Ti^2-4+：1-4mg/L，V^2-5+：2-7mg/L，Fe^2/3+：7637-12296mg/L，As^3/5+：1205-1595mg/L，Se^4/6+：6-10mg/L，Mo^2/4/6+：3-4mg/L，Sn^2/4+：0.1-2mg/L，Re^2/4/6/7+：0-1mg/L，Pt^2-6+：0-1mg/L，Hg^2/4+：0-1mg/L，Bi^3/5+: 0-1mg/L of composite metal ion solution.

When the rare metals are enriched, quantitatively pumping the mineral acid immersion liquid into a mixing reaction tank, and quantitatively adding the immobilized tannin for adsorption reaction; filtering after adsorption is finished, roasting filter residues to obtain germanium concentrate, and performing a germanium metal purification smelting process; and after metal ions such as iron, arsenic and the like are further removed from the filtrate, recovering the metal zinc or other metal ions by adopting an electrolytic deposition method.

In particular, the pH of the pickling liquid containing the dilute metal ions is 1 to 5, preferably 2 to 5, more preferably 4.0 to 4.5.

Particularly, the pickle liquor containing the dilute metal ions comprises Ge⁴⁺、Ga³⁺、In³⁺、Co²⁺、Mn²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Ba²⁺、Al³⁺、Fe³⁺Or Cr³⁺Plasma, preferably Ge⁴⁺、Ga³⁺、In³⁺Ions.

In particular, the concentration of each of the dilute metal ions in the pickle liquor containing the dilute metal ions is less than or equal to 400mg/L, preferably 10-200mg/L, and more preferably 100 mg/L.

In particular, the acid leaching solution containing the dispersed metal ions has the dispersed metal ions Ge⁴⁺、Ga³⁺、In³⁺The concentration of the ions is less than or equal to 400mg/L, preferably 10-200mg/L, and more preferably 100 mg/L.

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

1. the immobilized tannin enriched with the scattered metals prepared by the method has high selectivity on adsorption and enrichment of the scattered metals.

2. The preparation method of the immobilized tannin enriched with the scattered metals is simple, the preparation process steps are short, the process conditions are mild, the operation and the control are easy, the method is suitable for large-scale popularization and application, and the cost of the scattered metals enrichment is reduced.

3. The immobilized tannin prepared by the method has high tannin conversion rate.

4. The immobilized tannin enriched with the scattered metals is used for adsorbing and enriching the scattered metal ions, so that the operation is simple, the adsorption quantity of the scattered metals is high, and the sedimentation efficiency is high; the immobilized tannin enriched with the scattered metals has stronger selective adsorption performance on metal ions with higher valence states, and particularly has better adsorption performance on Ge (IV), Ga (III) and In (III).

5. The immobilized tannin rich in the scattered metals has the advantages of strong stability, high adsorption activity, high mechanical strength and the like.

6. The immobilized tannin enriched with the scattered metals prepared by the invention is used for adsorbing and enriching the scattered metals, and the residual quantity of the tannin in the mineral acid immersion liquid after adsorption is low, so that the method does not cause interference to the subsequent smelting process and secondary pollution.

Drawings

FIG. 1 is an infrared spectrum of chitosan, phyllanthus emblica tannin, and phyllanthus emblica immobilized tannin;

FIG. 2 is a DSC spectra of chitosan, emblic leafflower fruit tannin, immobilized emblic leafflower fruit tannin;

FIG. 3A is a TG curve of chitosan, emblic leafflower fruit tannin, emblic leafflower fruit immobilized tannin;

FIG. 3B is a DTG curve of chitosan, phyllanthus emblica tannin, phyllanthus emblica immobilized tannin;

a in fig. 1, 2, 3A, 3B: chitosan; b: emblic tannin Phyllanthus emblica tanin; c: phyllanthus emblica immobilized tannin immobilized-tannin (PEIT)

FIG. 4 is a graph showing the effect of pH of a dilute metal ion solution to be enriched on the adsorption of metal ions by immobilized Emblica officinalis tannin;

FIG. 5 is a graph showing the effect of temperature on the adsorption capacity of immobilized emblic tannin for Ge (IV), Ga (III) and In (III);

FIG. 6 is a graph showing the effect of adsorption time on adsorption of Ge (IV), Ga (III) and In (III) by immobilized emblic tannin;

FIG. 7 is a graph showing the effect of the initial concentration of the dilute metal solution on the adsorption of Ge (IV), Ga (III) and In (III) by immobilized emblic tannin;

FIG. 8A is a Langmuir isotherm plot of metal ion adsorption by immobilized emblic tannin;

FIG. 8B is a Freundlich isotherm diagram of the adsorption of metal ions by immobilized emblic tannin;

in FIGS. 4-8B, - □ -Ga (III), - ○ -In (III), - △ -Ge (IV).

Detailed Description

The invention will be further described with reference to specific embodiments, and the advantages and features of the invention will become apparent as the description proceeds. These examples are illustrative only and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

Materials, reagents, apparatus

Chitosan (CS, degree of deacetylation not less than 95%, Aladdin reagent Co., Ltd.); emblic tannin (PEL TA, yunnan tianqi biotechnology limited); nitric acid is GR grade reagent; chrome skin powder (the capacity of absorbing tannin is not less than 0.060 g/g); glutaraldehyde, glacial acetic acid, sodium hydroxide, aluminum chloride hexahydrate, barium chloride, cadmium chloride, cobalt chloride hexahydrate, chromium chloride, copper chloride, ferric chloride, manganese chloride, nickel chloride, lead nitrate, zinc nitrate, germanium dioxide, gallium nitrate and indium nitrate are AR-grade reagents.

HH-601 Water bath magnetic stirrer, Waals electric Co., Ltd, Changzhou; testo-206 Portable pH meter, Germany Testo instruments, China subsidiary; AB204-S electronic balance, mettler-tollidodo (china) limit; SHZ-D (III) circulating water type multipurpose vacuum pump, Consumer of Zhihua instruments, City; VOS-300VD vacuum drying oven, Tokyo, Japan, chemical and physical instruments; agilent Cary Seties UV-V, S ultraviolet spectrophotometer, Agilent Technologies Inc.; ICP-MS inductively coupled plasma mass spectrometry, Thermo Fisher Scientific; tensor-27 Fourier Infrared Spectroscopy, Brucker, Germany; DSC200F3 differential scanning calorimeter, STA2500 synchronous thermal analyzer, German Chisco scientific instruments.

EXAMPLE 1 preparation of Chitosan-acetic acid solution, tannin-acetic acid solution

1. Preparing chitosan-acetic acid solution

Adding chitosan into an acetic acid solution, dissolving uniformly, and preparing a chitosan-acetic acid solution for later use, wherein the mass ratio of chitosan to acetic acid solution is 1 (20-40) (preferably 1: 30); the concentration of acetic acid solution is generally 1-3% by mass (preferably 2%);

dissolving accurately weighed chitosan (3g) in 90g of acetic acid solution with the mass percentage concentration of 2%, uniformly dissolving, and preparing chitosan-acetic acid solution (93g) for later use, wherein the mass ratio of the chitosan to the acetic acid solution is 1: 30;

2. preparing tannin-acetic acid solution

Adding emblic leafflower fruit tannin into an acetic acid solution, dissolving uniformly, and preparing a tannin-acetic acid solution for later use, wherein the mass ratio of the emblic leafflower fruit tannin to the acetic acid solution is 1:2-20 (preferably 1: 10); the concentration of acetic acid solution is generally 1-3% by mass (preferably 2%);

accurately weighing phyllanthus emblica tannin (2g), dissolving in 20g of acetic acid solution with the mass percentage concentration of 2%, and uniformly dissolving to prepare tannin-acetic acid solution (22g) for later use, wherein the mass ratio of the phyllanthus emblica tannin to the acetic acid solution is 1: 10;

in the specific embodiment of the invention, the mass percent concentration of the acetic acid solution is 2%, and other concentrations such as 1-3% are all suitable for the invention; the mass ratio of chitosan to acetic acid solution is 1:30, for example, other ratios such as 1:20-40 are suitable for the present invention; the mass ratio of the emblic leafflower fruit tannin to the acetic acid solution is 1:10 for example, and other ratios such as 1:2-20 are all suitable for the present invention.

Example 2 preparation of immobilized emblic tannin (PEIT)

1. Crosslinking reaction

Adding the tannin-acetic acid solution (22g) prepared in example 1 into a chitosan-acetic acid solution (93g) under stirring, uniformly mixing, and adding a glutaraldehyde solution (10g) with a mass percentage concentration of 5% (usually 0.2-5.0%), wherein the mass ratio of the emblic leafflower fruit tannin to the chitosan is 1:1.5 (usually 1 (0.5-2.5), preferably 1 (1-2), and more preferably 1: 1.5); the mass ratio of glutaraldehyde to phyllanthus emblica tannin is 1:4 (generally 1:2 to 16, preferably 1:2 to 8, and more preferably 1:2 to 4);

in the embodiment of the invention, the mass percent concentration of the glutaraldehyde solution is 5%, and other concentrations such as 0.2-5.0% are all suitable for the invention.

Then, the mixture is heated to 55 ℃ (usually 0 to 90 ℃, preferably 20 to 80 ℃) and is adjusted by 0.1mol/L NaOH or/and 0.1mol/L HCl to control the pH value during the reaction to be 4.0 (usually pH is 1 to 6, preferably pH is 2 to 6, and more preferably 3 to 4) to carry out the crosslinking reaction;

2. filtering and drying

After the crosslinking reaction is carried out for 3 hours (usually 0.5-10 hours), filtering, washing the filtered precipitation product with deionized water for 3 times (usually at least 2 times, preferably 3-5 times), and combining the washing solutions to obtain an immobilized tannin washing solution (100mL) for later use; then, the precipitation product is dried for 24 hours in vacuum at the temperature of 60 ℃ to prepare solidified emblic leafflower fruit tannin (5.45 g);

grinding the dried immobilized emblic tannin sample, sieving, and performing adsorption test on particles of 0.150-0.0750 mm.

Performing infrared spectroscopic analysis on the solidified emblic leafflower fruit tannin chitosan and emblic leafflower fruit tannin by adopting a TENSON 27 type Fourier transform infrared spectrometer, and tabletting by using KBr (Kbr) at the wavelength of 4000-400 cm^-1. Infrared spectrum analysis chart ofFIG. 1 shows the spectrum of emblic leafflower fruit tannin at 1720cm^-1The position is a stretching vibration peak of-C ═ O; 1630cm^-1And 1452cm^-1The position is a stretching vibration peak of C ═ C in a benzene ring; 1215cm^-1The peak is the stretching vibration peak of-C-O. Characteristic absorption peaks of these emblic tannin also appear in the immobilized emblic tannin, which indicates the successful progress of the immobilization reaction.

DSC analysis is carried out on chitosan, emblic leafflower fruit tannin and immobilized emblic leafflower fruit tannin by adopting a differential calorimeter, and the DSC test conditions are as follows: the temperature rise speed is 10 ℃/min, and the temperature range is 0-400 ℃. The analysis result is shown in fig. 2, wherein the chitosan has a distinct endothermic peak at about 75 ℃, which is the temperature of water loss of the chitosan. While the exothermic peak at 305 ℃ is caused by the cleavage of the glycosidic bond, the breakage of the pyran ring accompanied by the elimination of the amino group and the intermolecular crosslinking during the thermal decomposition of chitosan. Emblic leafflower fruit tannin is a mixed tannin and the sample is a commercial sample. The DSC curve of the prepared phyllanthus emblica immobilized tannin has a wider endothermic peak at 100 ℃ which is the dehydration temperature of the phyllanthus emblica immobilized tannin and a smaller exothermic peak at 280 ℃ which is the thermal decomposition temperature. As can be seen from the figure, the DSC curve of the emblic leafflower fruit immobilized tannin is similar to that of chitosan, and has the thermal stability which is not possessed by the emblic leafflower fruit tannin.

Adopting a thermogravimetric analyzer to perform TG analysis on chitosan, phyllanthus emblica tannin and immobilized phyllanthus emblica tannin, wherein the TG test conditions are as follows: the temperature rise speed is 10 ℃/min, and the temperature range is normal temperature to 500 ℃. The analysis results are shown in FIGS. 3A and 3B, in which the weight of the sample decreased at about 100 ℃ due to the evaporation of the adsorbed water in the sample. Although the samples were lyophilized prior to testing, it was difficult to remove all water molecules from them due to the interaction of hydrogen bonds. The chitosan is rapidly reduced in mass at 250-320 ℃, and is slowly decomposed after 320 ℃, which is caused by that glycosidic bonds are broken in the thermal decomposition process of the chitosan, pyran rings are broken, meanwhile, amino groups are removed, and intermolecular crosslinking is generated. The mass of the emblic leafflower fruit tannin is rapidly reduced between 140 ℃ and 230 ℃, the emblic leafflower fruit tannin is slowly decomposed after 230 ℃, and the maximum degradation temperature is 185 ℃. The maximum degradation temperature of the prepared emblic leafflower fruit immobilized tannin is 283 ℃, and is very close to the maximum degradation temperature (296 ℃) of chitosan. The major decomposition temperature of the emblic fixed tannins shifts to higher temperatures compared to the prototannins, indicating that the cross-linking between chitosan, emblic tannins and glutaraldehyde improves the thermal stability.

According to the forestry industry standard LY-T1642-2005 of the people's republic of China (tannin analysis and test method), the tannin conversion rate is measured by adopting an ultraviolet method, and the specific method is as follows:

taking 0.1g of an emblic leafflower fruit tannic acid standard sample, dissolving in water, and fixing the volume to 100mL to prepare an emblic leafflower fruit tannic acid standard solution for later use;

diluting the phyllanthus emblica tannic acid standard solution by 100 times to prepare phyllanthus emblica tannic acid standard working solution for later use;

combining the washing solutions collected after the crosslinking reaction in the step 3, diluting to 100mL with constant volume and 100 times to prepare washing working solution for later use;

accurately measuring 50mL of washing working solution, adding 0.18g of chrome skin powder into the washing working solution, adsorbing chromium by phyllanthus emblica tannin in the washing working solution, performing adsorption treatment for 1.0h, and filtering to obtain filtrate (namely non-tannin working solution) for later use;

measuring the absorbances of a tannin standard sample working solution, a washing working solution and a non-tannin working solution by using an ultraviolet spectrophotometer at a wavelength of 276nm and using distilled water as a reference and a 1cm cuvette respectively, and calculating the tannin conversion rate, wherein the specific steps are as follows:

calculating the mass of tannin in the washing liquid according to the formula (1):

in equation (1): m is₂: mass of tannin in washing liquid, g; a. the₀: absorbance of the non-tannin working solution; a. the₂: absorbance of the washing working solution; a. the₁: the absorbance of the working solution of the tannic acid standard sample; m is₁: tannic acid standard sample mass, g;

the tannin conversion was calculated according to equation (2):

in equation (2): θ: tannin conversion,%; m is₀: the method of the invention adds the weight of tannin, g, in the cross-linking reaction process; m is₂: mass of tannin in washing liquid, g;

calculating the percentage content of tannin in the immobilized tannin according to the formula (3):

in equation (3): m is₀: the mass of tannin added initially per g; θ: tannin conversion/%; m is₃: preparing the mass/g of the obtained immobilized tannin; γ: the mass percent of tannin in the immobilized tannin/%.

The measurement results are shown in table 1.

Example 2A preparation of immobilized emblic tannin (PEIT)

1. Crosslinking reaction

Adding a tannin-acetic acid solution (22g) prepared according to the method of example 1 into a chitosan-acetic acid solution (62g) under stirring, wherein the mass ratio of phyllanthus emblica tannin to chitosan is 1:1, and after uniformly mixing, respectively adding 20g, 10g, 5g, 2.5g and 1.25g of glutaraldehyde solution with the mass percentage concentration of 5%, wherein the mass ratios of glutaraldehyde to phyllanthus emblica tannin are respectively 1:2, 1:4, 1:8, 1:16 and 1: 32;

then heating to 55 deg.C (usually 0-90 deg.C, preferably 20-80 deg.C), adjusting with 0.1mol/L NaOH or/and 0.1mol/L HCl, and controlling pH value to 4.0 during reaction to perform crosslinking reaction;

wherein a tannin-acetic acid solution was prepared according to the method of example 1, 2g of emblic leafflower fruit tannin, 20g of acetic acid solution; a chitosan-acetic acid solution was prepared according to the method of example 1, wherein 2g of chitosan was added to 60g of acetic acid solution.

2. Filtering and drying

Same as in example 2.

According to the forestry industry standard LY-T1642-2005 of the people's republic of China (tannin analysis and test method), the tannin conversion rate is measured by adopting an ultraviolet method, and the measurement result is shown in Table 1.

Example 2B preparation of immobilized emblic tannin (PEIT)

1. Crosslinking reaction

Adding the tannin-acetic acid solution (22g) prepared in example 1 into 31g, 62g, 93g, 124g and 155g of chitosan-acetic acid solution prepared according to the method in example 1 under stirring, wherein the mass ratio of the phyllanthus emblica tannin to the chitosan is 1:0.5, 1:1, 1:1.5, 1:2 and 1:2.5 respectively, mixing uniformly, and adding glutaraldehyde solution (10g) with the mass percentage concentration of 5%, wherein the mass ratio of the glutaraldehyde to the phyllanthus emblica tannin is 1:4 respectively;

2. filtering and drying

Same as in example 2.

Example 2C preparation of immobilized emblic tannin (PEIT)

1. Crosslinking reaction

Adding the tannin-acetic acid solution (22g) prepared in example 1 into 93g of chitosan-acetic acid solution respectively under stirring, wherein the mass ratio of phyllanthus emblica tannin to chitosan is 1:1.5 respectively, mixing uniformly, and then adding glutaraldehyde solution (10g) with the mass percentage concentration of 5%, wherein the mass ratio of glutaraldehyde to phyllanthus emblica tannin is 1:4 respectively;

heating to 55 ℃, adjusting by 0.1mol/L NaOH or/and 0.1mol/L HCl, controlling the pH values in the reaction process to be 2, 3, 5 and 6 respectively, and carrying out crosslinking reaction;

2. filtering and drying

Same as in example 2.

TABLE 1 tannin conversion assay results

As shown in Table 1, the tannin conversion rate becomes stable after increasing gradually with the addition of glutaraldehyde, and reaches 96.95% when m (glutaraldehyde): m (phyllanthin) is 1: 4. And as glutaraldehyde continues to increase, the conversion rate of tannin does not increase obviously, and the tannin content in the immobilized tannin is reduced gradually, so that when m (glutaraldehyde) and m (phyllanthus tannin) are 1:4, the curing effect is better. The conversion rate of the emblic leafflower fruit tannin is increased and then reduced along with the increase of the dosage of the chitosan, and when m (chitosan) is 1.5:1, the conversion rate of the tannin reaches a maximum value of 97.45 percent, because the cross-linking polymerization reaction of glutaraldehyde between the amino groups of chitosan molecules is more easily caused by excessive glutaraldehyde and chitosan, ineffective polymerization is generated, and the improvement of the conversion rate of tannic acid is not facilitated. When the initial pH value of the reaction system is 4, namely the initial pH value of the tannin and chitosan mixed solution is maintained, the conversion rate of the phyllanthus emblica tannin reaches the maximum value of 96.5 percent. When the initial pH of the reaction solution is adjusted to a lower or higher value, the tannin conversion rate decreases with the change in pH. The reason is that the immobilization of tannic acid on chitosan substrate comprises two reactions, namely urea-formaldehyde condensation of glutaraldehyde and amino group and phenolic aldehyde condensation of glutaraldehyde and tannin, and due to the difference of the two reaction conditions, when the initial pH value of the system is changed, the reaction equilibrium is easily shifted to one reaction, so that the tannin conversion rate and the cured tannin content are reduced. This view is also evidenced by the trend of the change in the tannin content in the immobilized emblic tannin.

Example 3 preparation of a Dilute Metal-simulated Ore pickle liquor

According to the metal ion type contained in the lead-zinc ore lead-smelting smoke acid leaching solution provided by a certain large-scale nonferrous metal smelting company in Yunnan, the dilute metal simulated ore acid leaching solution is prepared.

Dissolving 14 metal salts of aluminum chloride hexahydrate, barium chloride, cadmium chloride, cobalt chloride hexahydrate, chromium chloride, copper chloride, ferric chloride, manganese chloride, nickel chloride, lead nitrate, zinc nitrate, germanium dioxide, gallium nitrate and indium nitrate in ultrapure water to prepare a simulated mineral acid immersion liquid, adjusting the pH value to 4.5 (usually 1-5, preferably the pH value to 3-5) by using 2% nitric acid solution or 0.1mol/L sodium hydroxide solution, and adjusting the pH value to 14 metal ions Ge in the simulated mineral acid immersion liquid⁴⁺、Ga³⁺、In³⁺、Co²⁺、Mn²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Ba²⁺、Al³⁺、Fe³⁺、Cr³⁺The concentration of (A) is 100mg/L (namely the concentration of 14 metal ions in the simulated mineral acid immersion liquid is 100mg/L respectively) for standby; ICP-MS (inductively coupled plasma mass spectrometer) is used for detecting the concentration C of metal ions in the scattered metal ion mixed liquid₀；

Example 4 immobilized Emblica tannin (PEIT) enrichment of rare metals

1. Preparing dilute metal simulated ore pickle liquor

The same as example 3 except that 2% nitric acid solution or/and 0.1mol/L sodium hydroxide solution is/are used for adjusting the pH value of the dilute metal simulated mineral acid leaching solution to 1, 2, 3, 4 and 5;

besides the prepared diluted metal simulation ore acid immersion liquid, the immobilized tannin is suitable for adsorbing and enriching the acid immersion liquid in the smelting process of non-ferrous metal ores.

2. Adsorption of metal ions by PEIT

Respectively taking 100mL of scattered metal simulated mineral acid immersion liquid with pH values of 1, 2, 3, 4 and 5, respectively, putting into a beaker, respectively adding 0.1g (accurate to 0.0001g) of prepared immobilized tannin under the stirring state, magnetically stirring, and performing scattered metal adsorption enrichment, wherein the adsorption temperature is controlled at 30 ℃, and stirring for 3 hours;

stirring for 3 hr, filtering the mixture with 0.22 μm filter membrane, collecting filtrates, diluting with a certain amount of times (usually about 1000 times until the metal ion concentration in the sample solution is 10-1000 μ g/L), and detecting the metal ion concentration C in the diluted filtrate by ICP-MS_eCalculating the adsorption quantity as follows:

the adsorption amount of the immobilized tannin prepared by the invention is calculated according to the formula (4):

in equation (4): qe: the adsorption capacity of the immobilized tannin is mg/g; c₀: the mass concentration of metal ions in the mineral acid immersion liquid before adsorption is mg/L; ce: the mass concentration of metal ions in the adsorbed mineral acid immersion liquid is mg/L; v: volume of mineral acid leach, L; m is₄: mass of immobilized tannin used in the mineral acid dip added during adsorption, g.

The measurement results are shown in FIG. 4. The pH value of the aqueous solution not only affects the form of metal ions, but also affects the surface charge of the adsorbent, thereby affecting the adsorption process. The effect of the initial pH on the adsorption of Ge (IV), Ga (III) and In (III) by the cured emblic tannin is shown In FIG. 4.

The adsorption at pH values between 1 and 5 is not comparable because it is affected by the hydrolytic precipitation of the metal ions themselves when the pH reaches above 5. As can be seen from FIG. 4, the adsorption amounts of the solidified emblic tannin to three metal ions Ge (IV), Ga (III) and In (III) are highly dependent on pH value. Within the range of pH value 1-5, when the pH value is 1, the immobilized emblic leafflower fruit tannin has no adsorption effect on the three metal ions, and the reason is probably that when the pH value is 1, the dissociation degree of phenolic hydroxyl groups in the emblic leafflower fruit tannin is relatively low, the coordination affinity is not strong, and the adsorption capacity is extremely low. The adsorption capacity of the immobilized emblic tannin to Ge (IV), Ga (III) and In (III) is gradually increased along with the increase of the pH value, because the dissociation degree of the emblic tannin phenolic hydroxyl is increased along with the increase of the pH value of a system solution, the coordination affinity is increased, and the adsorption capacity is increased. When the pH value reaches 3, the adsorption capacity of the emblic leafflower fruit tannin to Ge (IV) and Ga (III) reaches the maximum value. When the pH value reaches 4, the adsorption amount of In (III) by the phyllanthus emblica tannin reaches the maximum value. When the pH value is increased to 5, the content of OH-in the solution is increased, a large amount of metal ions and OH-ions are hydrolyzed, and the metal ions generate flocculent precipitates, so that the adsorption quantity of the immobilized emblic leafflower fruit tannin is greatly reduced.

Example 4A enrichment of Dilute metals by immobilized Emblica tannin (PEIT)

1. Preparing dilute metal simulated ore pickle liquor

The same procedure as in example 3 was repeated, except that 2% nitric acid solution and/or 0.1mol/L sodium hydroxide solution was used to adjust the pH of the diluted metal-containing pseudo-mineral acid leachate to 4;

2. adsorption of metal ions by PEIT

Taking 5 parts of each 100ml of the scattered metal simulated mineral acid immersion liquid, respectively placing the immersion liquid into a beaker, respectively adding 0.1g (accurate to 0.0001g) of prepared immobilized tannin into the immersion liquid under the stirring state, and carrying out magnetic stirring to carry out scattered metal adsorption enrichment, wherein the adsorption temperature is controlled to be 20, 30, 40, 50 and 60 ℃, and the stirring is carried out for 3 hours (generally 2-4 hours, preferably 3-4 hours, and further preferably 3 hours);

stirring for 3 hr, filtering with 0.22 μm filter membrane, collecting filtrates, diluting with a certain amount (usually about 1000 times until the metal ion concentration in the sample solution is 10-1000 μ g/L), and detecting metal ion concentration C in the diluted filtrate by ICP-MS_eThe adsorption amount was calculated, and the measurement results are shown in FIG. 5, in which the adsorption amount was increased to a small extent when the adsorption temperature was increased from 20 ℃ to 30 ℃ and a large adsorption amount was obtained when the adsorption temperature was 20 ℃. And when the temperature continues to rise, the adsorption quantity is basically kept unchanged. The adsorption process of the immobilized emblic leafflower fruit tannin to Ge (IV), Ga (III) and In (III) is not sensitive to temperature, and the adsorption activation energy of the immobilized emblic leafflower fruit tannin is not high. And the optimal adsorption temperature of the immobilized emblic leafflower fruit tannin to Ge (IV), Ga (III) and In (III) is 30 ℃.

Example 4B immobilized Emblica tannin (PEIT) enrichment of Dilute metals

1. Preparing dilute metal simulated ore pickle liquor

Same as example 4A;

2. adsorption of metal ions by PEIT

Adding 0.1g (to the accuracy of 0.0001g) of immobilized tannin into 100mL of diluted metal simulated ore pickle liquor in a beaker under the stirring state, carrying out magnetic stirring to carry out the adsorption and enrichment of the diluted metal, wherein the adsorption temperature is controlled to be 30 ℃, mineral acid extract samples (0.1mL) are respectively extracted from the reaction mixture during the stirring process at 10min, 20min, 30min, 1h, 2h, 3h, 4h, 8h, 12h and 24h, the mineral acid extract samples are respectively filtered by a filter membrane of 0.22 mu m, the respectively collected filtrates are diluted by a certain multiple (usually about 1000 times until the concentration of metal ions in the sample solution is in the range of 10-1000 mu g/L), and ICP-MS is used for detecting the concentration C of the metal ions in the diluted filtrate_eThe adsorption amounts at different time points in the reaction process were calculated, and the analysis results are shown in fig. 6.

Adsorption kinetics is a model of the reaction adsorption rate in the adsorption process, and finally the adsorption mechanism is explored. FIG. 6 shows the change of the adsorption amounts of Ge (IV), Ga (III) and In (III) metal ions by immobilized emblic tannin with time.

The result shows that the adsorption capacity of the immobilized emblic tannin to the 3 metal ions Ge (IV), Ga (III) and In (III) In 10min reaches 70-80% of the equilibrium adsorption capacity. The subsequent adsorption capacity slowly increased with time and reached adsorption equilibrium at 3 h. And as can also be seen from fig. 6, the adsorption amount in all time periods is: in (III) > Ga (III) > Ge (IV). The adsorption rate of the immobilized emblic leafflower fruit tannin for adsorbing metal ions is controlled by a chemical adsorption mechanism, and the adsorption kinetics of the immobilized tannin accord with a quasi-second order kinetic equation.

Example 4C immobilized Emblica tannin (PEIT) enrichment of Dilute metals

1. Preparing a mixture of rare and dispersed metal ions

According to the type of metal ions contained in the lead-zinc ore lead-smelting smoke acid leaching solution provided by a certain large-scale nonferrous metal smelting company in Yunnan, a scattered metal ion mixed solution is prepared.

Respectively taking 14 metal salts of aluminum chloride hexahydrate, barium chloride, cadmium chloride, cobalt chloride hexahydrate, chromium chloride, copper chloride, ferric chloride, manganese chloride, nickel chloride, lead nitrate, zinc nitrate, germanium dioxide, gallium nitrate and indium nitrate for 8 times, dissolving the metal salts in ultrapure water for 8 times, adjusting the pH value to 4.0 by using 2% nitric acid solution and 0.1mol/L sodium hydroxide solution, and respectively preparing the metal salts containing 14 metal ions Ge⁴⁺、Ga³⁺、In³⁺、Co²⁺、Mn²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Ba²⁺、Al³⁺、Fe³⁺、Cr³⁺8 kinds of scattered metal ion mixed liquid with the concentration of each metal ion being 20, 40, 60, 80, 100, 150, 200 and 400mg/L respectively for later use; ICP-MS (inductively coupled plasma-mass spectrometry) is used for detecting metal ion concentration C in scattered metal ion mixed liquor₀；

2. Adsorption of metal ions by PEIT

Respectively taking 100mL of prepared scattered metal ion mixed liquid with different metal ion concentrations, placing the mixed liquid into different beakers, respectively adding 0.1g (accurate to 0.0001g) of prepared immobilized tannin into each beaker under the stirring state, carrying out magnetic stirring, and carrying out scattered metal adsorption and enrichment, wherein the adsorption temperature is controlled to be 30 ℃, and stirring for 3 hours;

stirring for 3 hr, filtering the mixture with 0.22 μm filter membrane, collecting filtrates, diluting with a certain amount of times (usually about 1000 times until the metal ion concentration in the sample solution is 10-1000 μ g/L), and detecting the metal ion concentration C in the diluted filtrate by ICP-MS_eThe adsorption amount was calculated, and the measurement results are shown in fig. 7.

The adsorption isotherm model can be used to describe the interaction between the adsorbent and the substance to be adsorbed. The change of the adsorption quantity of the immobilized emblic leafflower fruit tannin to Ge (IV), Ga (III) and In (III) along with the mass concentration under the conditions that the initial metal ion mass concentration is within the range of 0-400 mg/L and the pH value, the adsorption temperature and the adsorption time are consistent is examined as shown In figure 7. When the initial mass concentration is low, the adsorption amount of the immobilized emblic tannin to Ge (IV), Ga (III) and In (III) is low, which may be that the effective collision frequency of the immobilized emblic tannin and metal ions is low under the condition of low concentration. The adsorption amount of the immobilized emblic tannin gradually increases with the increase of the mass concentration of the metal ions until the saturation is reached. When the mass concentration of the metal ions reaches 100mg/L, the adsorption capacity reaches saturation, namely, the maximum adsorption capacity is reached, and the maximum adsorption capacity of the immobilized emblic leafflower fruit tannin to Ge (IV), Ga (III) and In (III) is 54.11, 67.65 and 70.00mg/g respectively. When the mass concentration is more than 100mg/L, the adsorption capacity tends to decrease, which is probably that when the concentration of the metal ions is higher, the metal ions are desorbed by the immobilized emblic leafflower fruit tannin.

Using Langmuir isotherm model

Freundlich isotherm model

Study on adsorption of Metal ions by Phyllanthus emblica immobilized tannin, q_eMg/g for achieving the adsorption capacity of adsorption equilibrium; c_eIs the equilibrium mass concentration of adsorbate in the solution, mg/L; q. q.s_mThe maximum adsorption capacity of the adsorbent for adsorbing metal ions in unit weight, mg/g; k_LIs a Langmuir adsorption equilibrium constant, L/g, relating to the bond energy between the adsorbent and the adsorbate in the adsorption reaction; k_FAnd n are the Freundlich constants associated with adsorption capacity, adsorption strength, and spontaneity, respectively. The Langmuir isotherm model is based on monolayer adsorption with uniformly distributed adsorption sites on the adsorbent surface, while the Freundlich isotherm model is based on multilayer adsorption with non-uniform adsorption sites on the adsorbent surface.

Adsorption isotherms for adsorbing Ge (iv), Ga (iii) and In (iii) on phyllanthus emblica immobilized tannin are shown In fig. 8A and 8B, and the calculation parameters are shown In table 2.

The results show that the Langmuir model describes the adsorption process better than the Freundlich model for Ge (IV), Ga (III), In (III), R of the Langmuir model²Are all greater than 0.9752, and R of Freundlich model²In the range of 0.61-0.70, and La is usedThe maximum adsorption value (qm) simulated by the ngmuir model is substantially consistent with the actual experimental result (qeexp). The adsorption of the phyllanthus emblica immobilized tannin on the metal ions is more consistent with the Langmuir model. Namely, uniform adsorption sites exist on the surface of the emblic leafflower fruit immobilized tannin, a monomolecular layer adsorbs Ge (IV), Ga (III) and In (III) In water, and the adsorption capacity of the emblic leafflower fruit immobilized tannin is In (III)>Ga(Ⅲ)>And (IV) Ge (IV). For the Freundlich model, the "n" of Ge (IV), Ga (III) and In (III) is 1<n<The content of the tannin is within 10, which indicates that the adsorption process of the emblic leafflower fruit immobilized tannin to Ge (IV), Ga (III) and In (III) is easy to occur.

TABLE 2 Langmuir and Freundlich isotherm model parameters

The preparation method comprises the steps of taking emblic leafflower fruit tannin, chitosan and glutaraldehyde as raw materials, and fixing the emblic leafflower fruit tannin on the chitosan in a cross-linking mode to prepare the high-efficiency scattered metal ion solid adsorbent, namely the immobilized emblic leafflower fruit tannin. The optimal preparation conditions are as follows: the mass ratio of glutaraldehyde to emblic leafflower fruit tannin is 1:4, the mass ratio of chitosan to emblic leafflower fruit tannin is 1.5:1, the initial pH value of the reaction solution is 4.0, and the reaction is carried out for 3.0h at the temperature of 55 ℃.

The phyllanthus emblica immobilized tannin is used for the experiment of adsorbing metal ions, and the result shows that: among 14 metal ions containing Ge (IV), Ga (III), In (III) and other scattered metal ions, the phyllanthus emblica immobilized tannin has good adsorption performance and good adsorption rate on Ge (IV), Ga (III) and In (III), and the adsorption process accords with a quasi-second-order adsorption kinetic model, so that the adsorption rate of the phyllanthus emblica immobilized tannin for adsorbing the metal ions is controlled by a chemical adsorption mechanism. The adsorption isotherm study shows that the emblic fixed tannin also conforms to a Langmuir isotherm model, which indicates that the chitosan solidified emblic tannin surface has uniform adsorption sites, and the monomolecular layer adsorbs Ge (IV), Ga (III), In (III) and other rare metals, and the maximum adsorption amounts are 54.11mg/g, 67.65mg/g and 70.00mg/g respectively.

Example 4D immobilized Emblica tannin (PEIT) enrichment of Dilute metals

1. Preparing dilute metal simulated ore pickle liquor

Same as in example 3;

2. adsorption of metal ions by PEIT

Respectively taking 100mL of the prepared scattered metal simulated mineral acid immersion liquid into a beaker, respectively adding 0.1g (accurate to 0.0001g) of PEIT prepared in examples 2, 2A, 2B and 2C into the beaker under the stirring state, carrying out magnetic stirring, and carrying out scattered metal ion adsorption and enrichment, wherein the adsorption temperature is controlled to be 30 ℃, and stirring for 3 hours; filtering the mixture with 0.22 μm filter membrane, collecting filtrates, diluting with a certain amount of times (usually about 1000 times until the metal ion concentration in the sample solution is 10-1000 μ g/L), and detecting the metal ion concentration C in the diluted filtrate by ICP-MS_eThe adsorption amount of PEIT was calculated according to the formula (4), and the measurement results are shown in tables 3 and 4.

The adsorption effect of the synthesis conditions of the immobilized emblic tannin on the divalent scattered metal ions is shown in table 3.

TABLE 3 influence of PEIT Synthesis conditions on the adsorption of divalent Metal ions by PEIT

The adsorption effect of the synthesis conditions of the immobilized emblic tannin on trivalent scattered metal ions is shown in table 4.

TABLE 4 influence of PEIT Synthesis conditions on adsorption of trivalent and higher metal ions by PEIT

As shown In tables 3 and 4, the prepared immobilized emblic leafflower fruit tannin has stronger selective adsorption performance on metal ions with higher valence states, and particularly has better adsorption performance on Ge (IV), Ga (III) and In (III). The other metal ions existing In the solution to be adsorbed have the action relations of 'synergy', 'salting out' and 'competition' on Ge (IV), Ga (III) and In (III), so that the adsorption process and the adsorption mechanism of the immobilized tannin In a pure germanium ion system are obviously different from those of the immobilized tannin In a complex metal ion solution system, and the adsorption amount is different from that of the pure germanium, gallium and indium system. This also has a corroborative relationship with the previous studies: for example, Zhang et al found that the presence of Zn ions in PGG inhibits germanium deposition during germanium adsorption, but the ability to inhibit germanium deposition gradually decreased with increasing Zn concentration. Shigehiro Kagaya found that indium phosphate was precipitated together with metal ions such as Fe, Cr and Pb in a synergistic manner.

When m (chitosan) and m (emblic leafflower fruit tannin) are 1.5:1, compared with the immobilized tannin synthesized under other horizontal conditions, the adsorption effect on the scattered metal is optimal, the adsorption quantity on the scattered metal and the adsorption quantity on metal ions such as iron, aluminum and the like have the maximum difference, and the tannin is only 35.77% at the moment, so that the tannin utilization rate is high. When the reaction pH value is increased, the adsorption performance of the synthesized immobilized tannin on metal ions is slowly increased, and the adsorption capacity of the synthesized immobilized tannin on the scattered metal is optimal when the pH value is 6. However, when the pH value of the reaction system is 6, the conversion rate of the emblic leafflower fruit tannin is only 88.25 percent at least, and when the pH value of the reaction system is 6, part of chitosan is separated out. In combination with the effect of initial pH on tannin conversion, pH4 was chosen as the preparation condition for immobilized tannins.

In summary, the optimal conditions for preparing the emblic leafflower fruit immobilized tannin are that m (glutaraldehyde), m (emblic leafflower fruit tannin) is 1:4, m (chitosan), m (emblic leafflower fruit tannin) is 1.5:1, and the initial pH value of the reaction is 4.

The above-described embodiments of the present invention are merely exemplary and do not limit the scope of the present invention in any way. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, and that such changes and modifications may be made without departing from the spirit and scope of the invention.

Claims

1. A method for preparing immobilized tannin rich in scattered metals comprises uniformly mixing tannin, chitosan and glutaraldehyde, and performing crosslinking reaction under heating condition, wherein the tannin is selected from emblic leafflower fruit tannin, gallnut tannin or tara tannin.

2. A preparation method of immobilized tannin enriched with scattered metals is characterized by comprising the following steps:

3) after the crosslinking reaction is carried out for 0.5-10h, filtering treatment is carried out, and then the precipitated product is washed by deionized water for at least 2 times; then drying the precipitate to obtain the immobilized tannin.

3. The method as set forth in claim 2, wherein the ratio of the mass of tannin in the tannin-acetic acid solution to the mass of chitosan in the chitosan-acetic acid solution in step 2) is 1: (0.5-2.5), preferably 1: (1-2).

4. The method as set forth in claim 2 or 3, characterized in that the ratio of the mass of glutaraldehyde in the glutaraldehyde solution in step 2) to the mass of tannin in the tannin-acetic acid solution is 1 (2-16), preferably 1 (2-8).

5. A method according to claim 2 or 3, characterized in that in step 2) the pH of the reaction system is controlled to 1-6, preferably 2-6, during the crosslinking reaction.

6. A scatteringly enriched immobilized tannin characterized in that it is prepared by the process as claimed in any one of claims 1 to 5.

7. A method for enriching scattered metal is characterized in that immobilized tannin enriched with scattered metal is added into a solution containing scattered metal ions under the stirring state for adsorption treatment.

8. The method according to claim 7, wherein the adsorption temperature is controlled to be 60 ℃ or less, preferably 20 to 60 ℃ or less during the adsorption treatment.

9. A method according to claim 7 or 8, characterized in that during the adsorption treatment the pH of the solution containing the dilute metal ions is controlled to 1-5, preferably 2-5.

10. The method of claim 7 or 8, wherein the dilute metal ion solution comprises Ge⁴⁺、Ga³⁺、In³⁺、Co²⁺、Mn²⁺、Ni²⁺、Cu²⁺、Zn²⁺、Cd²⁺、Pb²⁺、Ba²⁺、Al³⁺、Fe³⁺Or Cr³⁺One or more of the ions, preferably Ge⁴⁺、Ga³⁺Or In³⁺One or more of ions.