阅读说明：本技术 一种高寒高海拔地区尾矿放射性元素转移与吸附方法 (Method for transferring and adsorbing radioactive elements in tailings in alpine high-altitude areas ) 是由 翁仁贵 黄鑫 旦增 吕学斌 于 2021-06-17 设计创作，主要内容包括：本发明涉及放射性污染物清除领域,尤其涉及一种高寒高海拔地区尾矿放射性元素转移与吸附方法,包括以下步骤：(S.1)将含有放射性元素钍的尾矿进行加热烘干,经过研磨后加水配制成尾矿浆；(S.2)将尾矿浆浸入到氢氟酸-硫酸体系中,使得尾矿中放射性元素的浸出；(S.3)滤出尾矿后,向浸出液投加吸附微球,对射性元素进行吸附；(S.4)滤出吸附微球,完成对射性元素的转移；其中,所述步骤(S.3)中吸附微球为纳米氧化铁/氧化石墨烯/壳聚糖复合微球。本发明通过氢氟酸-硫酸双酸体系能够加快射性元素钍浸出,同时采用纳米氧化铁/氧化石墨烯/壳聚糖微球吸附材料能够大大提升对于浸出液中钍的吸附率,实现了对放射性元素钍的高效吸附。(The invention relates to the field of radioactive pollutant removal, in particular to a method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas, which comprises the following steps: (S.1) heating and drying the tailings containing the radioactive element thorium, grinding the tailings, and adding water to prepare tailing slurry; (S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system to leach radioactive elements in the tailings; (S.3) after the tailings are filtered out, adding adsorption microspheres into the leaching solution to adsorb the radioactive elements; (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements; wherein, the adsorption microspheres in the step (S.3) are nano iron oxide/graphene oxide/chitosan composite microspheres. According to the invention, the leaching of the radioactive element thorium can be accelerated through a hydrofluoric acid-sulfuric acid double-acid system, and meanwhile, the adsorption rate of thorium in the leachate can be greatly improved by adopting a nano iron oxide/graphene oxide/chitosan microsphere adsorption material, so that the efficient adsorption of the radioactive element thorium is realized.)

1. A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas is characterized by comprising the following steps:

(S.1) heating and drying the tailings containing the radioactive element thorium, grinding the tailings, and adding water to prepare tailing slurry;

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system to leach radioactive elements in the tailings;

(S.3) after the tailings are filtered out, adding adsorption microspheres into the leaching solution to adsorb the radioactive elements;

(S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements;

wherein, the adsorption microspheres in the step (S.3) are nano iron oxide/graphene oxide/chitosan composite microspheres.

2. The method for transferring and adsorbing radioactive elements in tailings of alpine and high-altitude areas according to claim 1, wherein the drying temperature in the step (S.1) is 100-105 ℃, and the drying treatment time is 12-24 hours.

3. The method for transferring and adsorbing radioactive elements in tailings of high-cold high-altitude areas according to claim 1 or 2, wherein the particle size of the tailings after grinding in the step (S.1) is less than 0.45mm, and the concentration of the tailings slurry obtained by configuration is 60-70 wt%.

4. The method for transferring and adsorbing radioactive elements in tailings of alpine and high-altitude areas according to claim 1, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system in the step (s.2) is 1: (1-10), wherein the ratio of the mass of the tailing slurry to the volume of hydrofluoric acid is 1 g: (4-15) ml.

5. The method for transferring and adsorbing radioactive elements in tailings of high-cold high-altitude areas as claimed in claim 1 or 3, wherein the pH value during leaching in the step (S.2) is controlled to be 3-5, the leaching time is 2-4 h, and the leaching temperature is 70-90 ℃.

6. The method for transferring and adsorbing radioactive elements in tailings of high-cold high-altitude areas according to claim 1, wherein the addition amount of the adsorption microspheres in the step (S.2) is 0.1-0.25 g/L, the pH value of the leachate during adsorption is controlled to be 4-6, and the adsorption reaction time is 4-6 hours.

7. The method for transferring and adsorbing radioactive elements in tailings of alpine and high-altitude areas according to claim 1 or 6, wherein the preparation method of the nano iron oxide/graphene oxide/chitosan composite microspheres comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural flake graphite and potassium permanganate;

(b) adding nano iron oxide into the suspension, performing ultrasonic dispersion, and stirring for reaction for a certain time to obtain a graphene oxide suspension loaded with the nano iron oxide;

(c) dissolving a certain amount of chitosan into glacial acetic acid to obtain a chitosan solution;

(d) and mixing the modified graphene oxide turbid liquid and the chitosan solution according to a certain proportion, continuously stirring for reaction, pouring the mixed solution into a mold, standing for aging, and then placing in vacuum freeze drying to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

8. The method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas according to claim 7, wherein the addition amount of the nano iron oxide in the step (b) is 0.2-0.5% of the mass of the graphene suspension, the ultrasonic dispersion time is 5-30 min, the reaction temperature of the reaction and stirring is 40-45 ℃, and the stirring time is 18-24 h.

9. The method for transferring and adsorbing radioactive elements in tailings of high-cold high-altitude areas as claimed in claim 7, wherein the concentration of glacial acetic acid in the step (c) is 5-7%, and the mass fraction of the chitosan solution is 2-3%.

10. The method for transferring and adsorbing radioactive elements in tailings of high-cold high-altitude areas according to claim 7, wherein the volume ratio of the modified graphene oxide suspension to the chitosan solution in the step (d) is (2-4): (3-5), stirring for 6-8 h, standing for 12-18 h, and freeze-drying for 24-48 h in vacuum.

Technical Field

The invention relates to the field of radioactive pollutant removal, in particular to a method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas.

Background

The tailings are waste discharged by mining enterprises under certain technical and economic conditions, but are potential secondary resources at the same time. The tailings are residual substances after the ore is sorted and treated, so that the valuable metal elements are low in grade, the mineral phases are complex, the utilization of the tailings is large in investment and low in return benefit, and the tailings are a difficult problem faced by the resource industry in China at present. The comprehensive recovery treatment of the tailings can eliminate the serious pollution to the environment, effectively utilize the secondary resources in the tailings and is an important method for realizing the circular economy of the mining industry in China.

Thorium is a natural radioactive element and widely distributed in thorium ore, uranium ore and rare earth ore. Waste water and waste generated by nuclear energy development, ore treatment and the like usually contain low-concentration radioactive needles, and are far from harmful to human beings. Untreated tailings not only occupy the land, but also radioactive elements enter the surrounding soil and surface water under the action of rain wash and dust raising, and if unreasonable control is performed, on one hand, harm is caused to human health through food chain transmission, and on the other hand, the radioactive elements can enter rivers or underground water under the action of runoff to threaten the safety of drinking water. Therefore, effective treatment and utilization of thorium in the environment are very important.

In the prior art, the transfer and adsorption of thorium are still rarely reported, and some technical schemes in the prior art generally have the technical problem of low radioactive element transfer rate. In the high-cold high-altitude area, the transfer rate is low due to the interference of factors such as air temperature, atmospheric pressure and the like. Therefore, it is necessary to research the leaching rule of radioactive elements in tailings and the adsorption method of the leached radioactive elements.

Disclosure of Invention

The invention provides a method for transferring and adsorbing radioactive elements in tailings of alpine and high-altitude areas, aiming at overcoming the technical problem that the transfer rate of radioactive elements thorium is low in the prior art.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) heating and drying the tailings containing the radioactive element thorium, grinding the tailings, and adding water to prepare tailing slurry;

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system to leach radioactive elements in the tailings;

(S.3) after the tailings are filtered out, adding adsorption microspheres into the leaching solution to adsorb the radioactive elements;

(S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements;

wherein, the adsorption microspheres in the step (S.3) are nano iron oxide/graphene oxide/chitosan composite microspheres.

Preferably, in the step (S.1), the drying temperature is 100-105 ℃, and the drying treatment time is 12-24 h.

Preferably, the particle size of the tailings after grinding in the step (S.1) is less than 0.45mm, and the concentration of the tailings slurry obtained by configuration is 60-70 wt%.

Preferably, the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system in step (s.2) is 1: (1-10), wherein the ratio of the mass of the tailing slurry to the volume of hydrofluoric acid is 1 g: (4-15) ml.

Preferably, the pH value during leaching in the step (S.2) is controlled to be 3-5, the leaching time is 2-4 h, and the leaching temperature is 70-90 ℃. In the step (S.2), the addition amount of the adsorption microspheres is 0.1-0.25 g/L, the pH value of the leachate is controlled to be 4-6 during adsorption, and the adsorption reaction time is 4-6 h.

Preferably, the preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural flake graphite and potassium permanganate;

(b) adding nano iron oxide into the suspension, performing ultrasonic dispersion, and stirring for reaction for a certain time to obtain a graphene oxide suspension loaded with the nano iron oxide;

(c) dissolving a certain amount of chitosan into glacial acetic acid to obtain a chitosan solution;

(d) and mixing the modified graphene oxide turbid liquid and the chitosan solution according to a certain proportion, continuously stirring for reaction, pouring the mixed solution into a mold, standing for aging, and then placing in vacuum freeze drying to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Preferably, the addition amount of the nano iron oxide in the step (b) is 0.2-0.5% of the mass of the graphene suspension, the ultrasonic dispersion time is 5-30 min, the reaction temperature is 40-45 ℃, and the stirring time is 18-24 h.

Preferably, in the step (c), the concentration of the glacial acetic acid is 5-7%, and the mass fraction of the chitosan solution is 2-3%.

Preferably, the volume ratio of the modified graphene oxide suspension to the chitosan solution in the step (d) is (2-4): (3-5), stirring for 6-8 h, standing for 12-18 h, and freeze-drying for 24-48 h in vacuum.

Preferably, the tailings of the radioactive element thorium are lead-zinc tailings.

The invention has the following beneficial effects:

the technical scheme of the invention generally adopts a double-acid system leaching plus nano iron oxide/graphene oxide/chitosan microsphere adsorption mode with large specific surface area and high mechanical strength to transfer and adsorb radioactive thorium in tailings.

Firstly, the tailings containing radioactive element thorium are immersed into a hydrofluoric acid-sulfuric acid system, so that the leaching of the thorium element in the tailings is accelerated to the greatest extent. The principle is as follows: the sulfuric acid in the hydrofluoric acid-sulfuric acid system is capable of providing hydrogen ions as wellThe increase of the concentration of the sulfuric acid increases the amount of hydrogen ions, so that the mineral structure can be effectively destroyed, and thorium elements in tailings are exposed. Meanwhile, the acidic fluoride ion solution has extremely strong corrosivity, can slowly dissolve and corrode the surface and the gap interface of the dissolved tailing particles, increases the specific surface area of the ore particles, and also improves the leaching efficiency of the thorium element. At the same time, due to fluorine ion and Th⁴⁺The strong coordination capacity of the method activates the state of the particle interface, thereby further promoting the leaching of thorium in tailings. The double-acid system adopted by the technical scheme also has the advantages of convenient operation, simple process, good treatment effect and low cost.

In the adsorption step, although the prior art has a certain precedent for adsorbing the metal elements in the aqueous solution, the prior art also has the defects. For example, activated carbon, resin materials, and the like are mainly used as common adsorbents, but these adsorbents have a drawback of low adsorption capacity and low adsorption efficiency. Graphene is a novel carbon material, has properties such as large specific surface area and high porosity, and can purify elemental pollutants quickly and efficiently, so that radioactive pollution is minimized in a very short time, and diffusion of nuclear pollution and damage to graphene as an adsorbent to treat wastewater are avoided. Although graphene has many advantages, there are disadvantages such as agglomeration, poor biocompatibility, and difficulty in separating solid and liquid phases. When the graphene oxide and the chitosan are directly used for adsorbing wastewater, the defects of difficult separation, low adsorption quantity, easy loss and the like exist generally. The existing literature applies different technical methods to prepare graphene oxide and chitosan composite adsorption materials with different forms, but the defects of high process cost, high requirement conditions for the preparation process, complexity and the like exist. Researches show that the graphene oxide adsorption material can well adsorb and remove heavy metal ions in a solution, and researches on adsorption of thorium which is a radioactive element are only reported at present.

The difference between the adsorbing material adopted by the invention and the adsorbing material is that a plurality of different materials are compounded, so that the respective defects of the materials can be overcome after the advantages of the materials are integrated.

The invention adopts a technical scheme that a novel nano iron oxide/graphene oxide/chitosan adsorption material is used for adsorbing thorium which is a radioactive element in the tailing leachate. The chitosan is taken as a typical natural organic adsorbent, amino of the chitosan and hydroxyl on the surface of graphene oxide can react, and the chitosan is compounded with the graphene oxide, so that the layer-by-layer stacking of the graphene can be reduced, and the actual adsorption capacity of the adsorbent is increased. The prepared graphene oxide and chitosan composite material contains rich amino and hydroxyl, and has Th (Th-beta-carotene)⁴⁺Has double chelation effect, and can increase Th in leachate⁴⁺The active groups other than amino and hydroxyl groups can also be Th⁴⁺Provide lone pair of electrons to form coordination bond and Th⁴⁺And the effect of adsorption separation from the water body is achieved.

In addition, the nano material has a large specific surface area and a large number of unsaturated atoms on the surface, and by adding nano iron oxide and mixing with graphene oxide, the mechanical strength of the composite material is greatly improved, and the adsorption performance is improved.

In addition, the nano iron oxide/graphene oxide/chitosan adsorption material disclosed by the invention adopts a freeze-drying method which is simple and easy to operate, the component concentration is easy to control, the structure of the material can be kept, the preparation process is environment-friendly, the graphene and the chitosan are directly blended, the unique physical structure of the graphene cannot be changed, and the defects of high cost, secondary pollution and the like in the preparation process of other methods can be effectively avoided.

Drawings

FIG. 1 is a flow chart of the present invention.

Detailed Description

The invention is further described with reference to the drawings and the specific embodiments. Those skilled in the art will be able to implement the invention based on these teachings. Moreover, the embodiments of the present invention described in the following description are generally only some embodiments of the present invention, and not all embodiments. Therefore, all other embodiments obtained by a person of ordinary skill in the art based on the embodiments of the present invention without any creative effort shall fall within the protection scope of the present invention.

Example 1

A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) selecting certain lead-zinc tailings from Tibet, wherein the tailings containing radioactive element thorium are required to be placed in an oven at 100 ℃ for heating and drying for 12 hours due to the influence of high cold and high altitude of Tibet, then the tailings are ground into tailings with the particle size of less than 0.45mm, and then water is added to prepare tailing slurry with the concentration of 60 wt%.

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system is 1:1, and the mass ratio of the tailing slurry to the volume ratio of hydrofluoric acid is 1 g: 4ml, and controlling the pH value to be 3, the leaching time to be 2 hours and the leaching temperature to be 70 ℃ so as to leach the radioactive elements in the tailings.

(S.3) after tailings are filtered out, 0.1g/L of nano iron oxide/graphene oxide/chitosan composite microspheres are added into the leachate, the pH value of the leachate is controlled to be 4, the adsorption reaction time is 4 hours, and the adsorption of the correlation elements is completed.

And (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements.

The preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural flake graphite and potassium permanganate by using a Hummers method, adding 0.2% of nano iron oxide into the suspension, performing ultrasonic dispersion for 5min, keeping the reaction temperature at 40 ℃, and stirring for 18h to obtain the nano iron oxide-loaded graphene oxide suspension for later use. And then dissolving a certain amount of chitosan into 5% glacial acetic acid, and continuously stirring until the chitosan is completely dissolved to obtain a chitosan solution with the mass fraction of 2%. Taking the modified graphene oxide turbid liquid obtained by preparation and a chitosan solution according to the volume ratio of 2: 3, mixing and diluting, continuously stirring for 6h, pouring the mixed solution into a mould, standing and aging for 12h, and placing the mould into a vacuum freeze dryer for freeze drying for 24h to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Example 2

A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) selecting certain lead-zinc tailings from Tibet, wherein the tailings containing radioactive element thorium are required to be placed in an oven at 105 ℃ for heating and drying for 24 hours due to the influence of high cold and high altitude of Tibet, then the tailings are ground into tailings with the particle size of less than 0.45mm, and then water is added to prepare tailing slurry with the concentration of 70 wt%.

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system is 1:10, and the mass ratio of the tailing slurry to the volume ratio of hydrofluoric acid is 1 g: 15ml, and controlling the pH value to be 5, the leaching time to be 4 hours and the leaching temperature to be 90 ℃, so as to leach the radioactive elements in the tailings.

(S.3) after tailings are filtered out, 0.25g/L of nano iron oxide/graphene oxide/chitosan composite microspheres are added into the leachate, the pH value of the leachate is controlled to be 6, the adsorption reaction time is 6 hours, and the adsorption of the correlation elements is completed.

And (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements.

The preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural flake graphite and potassium permanganate by using a Hummers method, adding 0.5% of nano iron oxide into the suspension, performing ultrasonic dispersion for 30min, keeping the reaction temperature at 45 ℃, and stirring for 24h to obtain the nano iron oxide-loaded graphene oxide suspension for later use. And then dissolving a certain amount of chitosan into 7% glacial acetic acid, and continuously stirring until the chitosan is completely dissolved to obtain a chitosan solution with the mass fraction of 3%. Taking the modified graphene oxide turbid liquid obtained by preparation and a chitosan solution according to the volume ratio of 4: and 5, mixing and diluting, continuously stirring for 8h, pouring the mixed solution into a mold, standing and aging for 18h, and placing the mold in a vacuum freeze dryer for freeze drying for 48h to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Example 3

A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) selecting certain lead-zinc tailings from Tibet, wherein the tailings containing radioactive element thorium are heated and dried for 15 hours in an oven at 102 ℃ due to the influence of high cold and high altitude of Tibet, then the tailings are ground into tailings with the particle size of less than 0.45mm, and then water is added to prepare tailing slurry with the concentration of 65 wt%.

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system is 1:5, and the mass ratio of the tailing slurry to the volume ratio of hydrofluoric acid is 1 g: 10ml, and controlling the pH value to be 4, the leaching time to be 3 hours and the leaching temperature to be 80 ℃, so as to leach the radioactive elements in the tailings.

(S.3) after tailings are filtered out, 0.15g/L of nano iron oxide/graphene oxide/chitosan composite microspheres are added into the leachate, the pH value of the leachate is controlled to be 5, the adsorption reaction time is 5 hours, and the adsorption of the correlation elements is completed.

And (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements.

The preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural flake graphite and potassium permanganate by using a Hummers method, adding 0.25% of nano iron oxide into the suspension, performing ultrasonic dispersion for 10min, keeping the reaction temperature at 42 ℃, and stirring for 20h to obtain the nano iron oxide-loaded graphene oxide suspension for later use. And then dissolving a certain amount of chitosan into 6% glacial acetic acid, and continuously stirring until the chitosan is completely dissolved to obtain a chitosan solution with the mass fraction of 2.5%. Taking the modified graphene oxide turbid liquid obtained by preparation and a chitosan solution according to the volume ratio of 3: 4, mixing and diluting, continuously stirring for 7h, pouring the mixed solution into a mold, standing and aging for 16h, and placing the mold in a vacuum freeze dryer for freeze drying for 36h to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Example 4

A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) selecting certain lead-zinc tailings from Tibet, wherein the tailings containing radioactive element thorium are heated and dried in an oven at 105 ℃ for 16 hours due to the influence of high cold and high altitude of Tibet, then the tailings are ground into tailings with the particle size of less than 0.45mm, and then water is added to prepare tailing slurry with the concentration of 64 wt%.

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system is 1:4, and the mass ratio of the tailing slurry to the volume ratio of hydrofluoric acid is 1 g: 10ml, and controlling the pH value to be 3.5, the leaching time to be 2.5h and the leaching temperature to be 75 ℃ so as to leach the radioactive elements in the tailings.

(S.3) after tailings are filtered out, 0.18g/L of nano iron oxide/graphene oxide/chitosan composite microspheres are added into the leachate, the pH value of the leachate is controlled to be 5.5, and the adsorption reaction time is 5 hours, so that the adsorption of the radioactivity elements is completed.

And (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements.

The preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural crystalline flake graphite and potassium permanganate by using a Hummers method, adding 0.3wt% of nano iron oxide into the suspension, performing ultrasonic dispersion for 20min, keeping the reaction temperature at 42 ℃, and stirring for 20h to obtain the nano iron oxide-loaded graphene oxide suspension for later use. And then dissolving a certain amount of chitosan into 6% glacial acetic acid, and continuously stirring until the chitosan is completely dissolved to obtain a chitosan solution with the mass fraction of 2%. Taking the modified graphene oxide turbid liquid obtained by preparation and a chitosan solution according to the volume ratio of 3: 5, mixing and diluting, continuously stirring for 6h, pouring the mixed solution into a mold, standing and aging for 14h, and placing the mold in a vacuum freeze dryer for freeze drying for 30h to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Example 5

A method for transferring and adsorbing radioactive elements in tailings in alpine and high-altitude areas comprises the following steps:

(S.1) selecting certain lead-zinc tailings from Tibet, wherein the tailings containing radioactive element thorium are heated and dried in an oven at 105 ℃ for 21 hours due to the influence of high cold and high altitude of Tibet, then the tailings are ground into tailings with the particle size of less than 0.45mm, and then water is added to prepare tailing slurry with the concentration of 68 wt%.

(S.2) immersing the tailing slurry into a hydrofluoric acid-sulfuric acid system, wherein the volume ratio of hydrofluoric acid to sulfuric acid in the hydrofluoric acid-sulfuric acid system is 1:8, and the mass ratio of the tailing slurry to the volume ratio of hydrofluoric acid is 1 g: 12ml, and controlling the pH value to be 4.5, the leaching time to be 3 hours and the leaching temperature to be 85 ℃, so as to leach the radioactive elements in the tailings.

(S.3) after tailings are filtered out, 0.2g/L of nano iron oxide/graphene oxide/chitosan composite microspheres are added into the leachate, the pH value of the leachate is controlled to be 5, the adsorption reaction time is 5 hours, and the adsorption of the correlation elements is completed.

And (S.4) filtering out the adsorption microspheres to finish the transfer of the correlation elements.

The preparation method of the nano iron oxide/graphene oxide/chitosan composite microsphere comprises the following steps:

(a) preparing a graphene oxide suspension by using sodium nitrate, natural crystalline flake graphite and potassium permanganate by using a Hummers method, adding 0.45wt% of nano iron oxide into the suspension, performing ultrasonic dispersion for 25min, keeping the reaction temperature at 42 ℃, and stirring for 20h to obtain the nano iron oxide-loaded graphene oxide suspension for later use. And then dissolving a certain amount of chitosan into 5% glacial acetic acid, and continuously stirring until the chitosan is completely dissolved to obtain a chitosan solution with the mass fraction of 3%. Taking the modified graphene oxide turbid liquid obtained by preparation and a chitosan solution according to the volume ratio of 4: 3, mixing and diluting, continuously stirring for 6h, pouring the mixed solution into a mould, standing and aging for 18h, and placing the mould into a vacuum freeze dryer for freeze drying for 42h to obtain the nano iron oxide/graphene oxide/chitosan microsphere adsorbing material.

Comparative example 1

The experimental conditions of the comparative example 1 are basically the same as those of the example 1, except that in the comparative example 1, a hydrofluoric acid-sulfuric acid double-acid system is changed into a mono-sulfuric acid system, and the nano iron oxide/graphene oxide/chitosan composite microspheres are replaced by graphene oxide.

Comparative example 2

The experimental conditions of the comparative example 2 are basically the same as those of the example 1, except that in the comparative example 1, a hydrofluoric acid-sulfuric acid double-acid system is changed into a monohydrofluoric acid system, and the nano iron oxide/graphene oxide/chitosan composite microspheres are replaced by graphene oxide and chitosan composite microspheres.

The leaching rates of the radioactive element thorium in the lead-zinc tailings and the adsorption rates of the radioactive element thorium in the leaching solutions of the examples 1 to 5 and the comparative examples 1 to 2 are tested, and the results are shown in the following table 1.

TABLE 1

From the data in the above table, the leaching rate of the hydrofluoric acid-sulfuric acid double acid system in examples 1 to 5 of the present invention is 65.2 at the lowest, while the leaching rate of comparative examples 1 to 2 is 48.9 at the highest in the conventional single acid system. Therefore, the leaching rate of the double-acid system is at least 15% higher than that of the single-acid system, so that the leaching efficiency of the radioactive element thorium in the lead-zinc tailings can be effectively improved, and the efficient transfer of the radioactive element thorium is realized.

The column of observing the adsorption rate of thorium in the leachate shows that the adsorption rate in the embodiments 1-5 of the invention is as low as 85.3%, and the adsorption rate in the comparative examples 1-2 is as high as 78.5, so that the adsorption rate of thorium in the leachate can be greatly improved by adopting the nano iron oxide/graphene oxide/chitosan microsphere adsorption material synthesized by the invention, and the efficient adsorption of thorium as a radioactive element is realized.