CN115155508A - FeS/LDH nano adsorbent and synthetic method and application thereof - Google Patents

FeS/LDH nano adsorbent and synthetic method and application thereof Download PDF

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CN115155508A
CN115155508A CN202210796113.1A CN202210796113A CN115155508A CN 115155508 A CN115155508 A CN 115155508A CN 202210796113 A CN202210796113 A CN 202210796113A CN 115155508 A CN115155508 A CN 115155508A
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adsorbent
fes
ldh
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salt
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CN115155508B (en
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李良
闫瑞鑫
孔龙
刘敏
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Shanghai Jiaotong University
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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    • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
    • B01J20/08—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04 comprising aluminium oxide or hydroxide; comprising bauxite
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    • B01J20/28002—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their physical properties
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    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28059—Surface area, e.g. B.E.T specific surface area being less than 100 m2/g
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    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28061—Surface area, e.g. B.E.T specific surface area being in the range 100-500 m2/g
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/28—Treatment of water, waste water, or sewage by sorption
    • C02F1/288—Treatment of water, waste water, or sewage by sorption using composite sorbents, e.g. coated, impregnated, multi-layered
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/103—Arsenic compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
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    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/10—Inorganic compounds
    • C02F2101/20—Heavy metals or heavy metal compounds
    • C02F2101/22—Chromium or chromium compounds, e.g. chromates

Abstract

The invention relates to an adsorbent, in particular to a FeS/LDH nano adsorbent and a synthesis method and application thereof, wherein the nano adsorbent is based on LDH and is loaded with amorphous iron sulfide on the surface; the method comprises the following steps: s1: dissolving ferric salt in deoxidized ultrapure water, fully dissolving the deoxidized ultrapure water by ultrasonic stirring, injecting and adding a NaOH solution, continuously stirring and adjusting the pH value to 8, adding a sulfur precursor solution, and fully reacting under the protection of inert gas; s2: centrifuging the solution reacted in the step S1, washing and drying the precipitate to obtain precursor powder; s3: and (3) calcining the precursor powder obtained in the step (S2) in an inert gas atmosphere to obtain the FeS/LDH nano adsorbent. Compared with the prior art, the method realizes the high-efficiency removal of common heavy metal anions in the wastewater, reduces the concentration of heavy metals in the water body, and simultaneously has the effect of fixing the heavy metals on the surface of the adsorbent.

Description

FeS/LDH nano adsorbent and synthetic method and application thereof
Technical Field
The invention relates to an adsorbent, in particular to a FeS/LDH nano adsorbent and a synthesis method and application thereof.
Background
Heavy metals are important mineral raw materials manufactured in the non-ferrous industry of China, are mostly distributed in soil matrixes, and are important raw materials in the industrial fields of smelting, alloy printing, mining, coal burning, electroplating, leather tanning, semiconductor manufacturing and the like. Excessive heavy metal mining not only causes rapid consumption of non-renewable resources, but also causes serious environmental problems with industrial waste generated by industrial products, such as industrial chromium slag is buried without treatment, which easily causes diffusion and migration of chromium elements, toxic hexavalent chromium is usually easy to migrate and diffuse under natural conditions, and pollution may be caused to soil groundwater after vertical migration, thereby posing threats to drinking water safety and human health. In addition, the high-concentration heavy metal anion wastewater generated in the electroplating industry also faces the problems of high treatment difficulty, high treatment cost and the like.
The common treatment means of heavy metal anions in water at present comprises a chemical precipitation method and an ion exchange method. Because of the physicochemical properties of heavy metal anions, heavy metals of different valences usually exhibit differential solubility products, and therefore, the valences of heavy metal anions are often changed to obtain corresponding metal oxides or hydroxides to precipitate, which facilitates the separation of heavy metal anions from water, such as Cr (VI), and a method of adding a reducing salt is usually employed to convert hexavalent chromium having high toxicity into trivalent chromium having low toxicity, and then, the trivalent chromium is converted into Cr (OH) by using basic substances such as lime, caustic soda and the like 3 Precipitating to remove hexavalent chromium. However, this method requires a large amount of alkali and a flocculant to be used in combination, and causes problems of an excessively high pH value of the effluent and an operation cost. The ion exchange method is to exchange ions with heavy metal anions in water through exchange resin or zeolite, and has the advantages of deep purificationHigh degree, simple operation, and the like, and has the disadvantages of high cost and low efficiency. Compared with the two methods, the nano adsorbent has the characteristics of high reactivity, large specific surface area, high adsorption speed and the like, can effectively enhance the atom utilization rate in the adsorbent, realizes high-efficiency ion transfer and reaction on a solid-liquid interface, and has important significance for developing the nano adsorbent which is generally suitable for heavy metal anions, wherein chemical means for adsorbing and fixing high-valence metals Cr (VI), as (V) and Sb (V) with higher oxidation-reduction potentials are common ideas for treating the three heavy metals.
Disclosure of Invention
The invention aims to solve at least one of the problems, provides a FeS/LDH nano-adsorbent, a synthesis method and an application thereof, realizes the efficient removal of three common heavy metal anions Cr (VI), as (V) and Sb (V) in wastewater, reduces the concentration of heavy metals in a water body, simultaneously has the effect of fixing the heavy metals on the surface of the adsorbent, and can realize the recycling of the adsorbent through elution treatment, thereby providing an economic solution for high-concentration wastewater.
The purpose of the invention is realized by the following technical scheme:
the invention discloses a FeS/LDH nano-adsorbent, which is based on LDH and is loaded with amorphous iron sulfide on the surface.
Preferably, the nano adsorbent has a particle size of 20-200 nm and a specific surface area of 80-150 m 2 (iv) g; at pH of<When 8, the Zeta potential on the surface of the adsorbent presents electropositivity, and the adsorbent has good electrostatic adsorption effect on heavy metal anions. Meanwhile, the larger specific surface area provides a large number of chemical adsorption sites for the adsorption of the adsorbent, and ensures that the pH value is in the pH range>When 8, the adsorbent also has good adsorption effect, so that the adsorbent has wider pH application range.
The second aspect of the invention discloses a method for synthesizing the FeS/LDH nano-adsorbent, which comprises the following steps of firstly pre-synthesizing an iron-containing precursor with a hydrotalcite-like layered structure, vulcanizing and then calcining at low temperature to synthesize amorphous iron sulfide with high reaction activity, namely FeS/LDH, and specifically comprises the following steps:
s1: dissolving ferric salt in deoxidized ultrapure water, fully dissolving the ferric salt by ultrasonic stirring, slowly injecting, adding NaOH solution, adjusting the pH value to be about 8, gradually adding a sulfur precursor solution, and fully reacting under the protection of inert gas;
s2: centrifuging the solution reacted in the step S1, washing and drying the precipitate to obtain precursor powder;
s3: and (3) calcining the precursor powder obtained in the step (S2) at low temperature in an inert gas atmosphere to obtain the FeS/LDH nano adsorbent.
Preferably, the iron salts described in step S1 include Fe (II) salts and Fe (III) salts, in terms of Fe (II) = 3; the Fe (II) salt is FeCl 2 ·4H 2 O、(NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O and FeSO 4 ·7H 2 One or more of O; the Fe (III) salt is FeCl 3 ·6H 2 O、Fe(NO 3 ) 3 ·9H 2 O and Fe 2 (SO 4 ) 3 ·5H 2 One or more of O; the molar ratio of Fe (II) salt to Fe (III) salt is 3. The addition of the Fe (III) salt can be used to form a hydrotalcite-like structure, which can cause the charge of the layered structure to remain due to the presence of the trivalent metal, and further attract the interlayer anions to neutralize the charge.
Preferably, the deoxygenated ultrapure water in step S1 is ultrapure water from which dissolved oxygen is removed, and the removal of dissolved oxygen in the ultrapure water is achieved by continuously introducing nitrogen gas into the ultrapure water for at least 30min.
Preferably, the concentration of the NaOH solution is 1-4 mol/L, the injection adding speed is 1-2 mL/min, and the stirring duration is at least 30min.
Preferably, the sulfur precursor solution in step S1 is one or more of thioacetamide, thiourea and sodium thiosulfate; the sulfur precursor solution is added according to the molar ratio of Fe (II) to S being 1. Since S cannot completely participate in the reaction, an excessive amount of S contributes to a forward shift of the reaction equilibrium, and gasification of S occurs during calcination, so that it is necessary to increase the dosage of S to resist loss. The excessive S improves the adsorption effect, but is not obvious, so the S can be controlled in a certain range, and the addition amount of the S is controlled in a proper range.
Preferably, the reaction time in step S1 is 4h.
Preferably, the drying in step S2 is vacuum drying at a temperature of 40 to 60 ℃.
The precursor powder obtained in step S2 is prepared by dissolving Fe (II) salt and Fe (III) salt in water sufficiently, and ultrasonic-assisted dissolution may be used. When NaOH is used for pH adjustment, the stirring is continuously carried out for at least 30min, so that divalent and trivalent ions directly form a hydrotalcite-like flaky structure instead of flocculent precipitates, the concentration of the NaOH can be 1-4 mol/L, the injection speed is 1-2 mL/min, the hydrotalcite-like structure can be fully grown, and the formation of high specific surface area is facilitated. Because the proportion of the hydrotalcite-like structure in the FeS/LDH nano-adsorbent can influence the crystallinity of the generated iron sulfide (FeS), the more NaOH participating in the reaction, the longer the reaction time, and the more remarkable the lamellar structure, the more the hydrotalcite-like structure can exert the uniform dispersion effect on the FeS, and simultaneously the crystal growth of the FeS is inhibited, and the obtained small-size amorphous FeS is beneficial to increasing the selective chemical adsorption on heavy metal anions. Therefore, the addition amount and speed of NaOH need to be controlled, namely the mass ratio of FeS to LDH in the FeS/LDH nano-adsorbent is controlled to be 1:1 to 1:4.
preferably, the calcination temperature in step S3 is 150-300 ℃ and the time is 2-4 h.
Preferably, the inert gas in step S1 and step S3 is nitrogen, argon or other inert gas.
The synthesis method can realize material synthesis at a lower calcination temperature (150-300 ℃) by loading uniformly distributed iron sulfide on a hydrotalcite-like layer plate as a reaction site and utilizing the characteristic of high specific surface area of a layered structure.
The third aspect of the invention discloses an application of the FeS/LDH nano-adsorbent in removing heavy metal anions in water.
Preferably, the FeS/LDH nano-adsorbent is used for removing heavy metal anions such As Cr (VI), as (V) and Sb (V) in a water body with the pH value of 3-10.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention takes a hydrotalcite-like mineral as a carrier, reduces or even eliminates the additional introduction of toxic and harmful substances in the practical application process, and reduces the risk of secondary pollution to the water body. Furthermore, the synthetic process of the adsorbent is simple and nontoxic, is suitable for one-time mass production, has the adsorption capacity of more than 200mg/g for heavy metal anions, namely hexavalent chromium (Cr (VI)), pentavalent antimony (Sb (V)) and pentavalent arsenic (As (V)), can quickly remove low-concentration wastewater in a short time, realizes deep purification of a water body in half an hour, and is a high-efficiency and convenient adsorption material.
2. The invention utilizes the layered structure of hydrotalcite-like compound, firstly obtains Fe (II) sites uniformly distributed on the surface of the layered structure, and then synthesizes FeS in situ on the sites, thereby realizing uniform dispersion of adsorption sites; and the generated nano adsorbent has a large specific surface area, can provide a large number of chemical adsorption sites, and can improve the adsorption effect.
3. The FeS/LDH synthesized by the method can reach the adsorption reaction balance within 24h, and can realize deep purification (< 0.01 mg/L) of heavy metal anions within 30min, thereby greatly shortening the treatment time and saving the time cost; meanwhile, the adsorbent has larger adsorption capacity, so that the use cost of the adsorbent is reduced, and the subsequent post-treatment of the adsorbent can be facilitated.
4. The FeS/LDH synthesized by the invention removes heavy metal anions partly from the electrostatic attraction effect of the surface of the adsorbent on the anions, and partly from the larger specific surface area, so that enough chemical adsorption sites are provided, namely, feS chemically reacts on the three anions. Specifically, the method can realize chemical adsorption of heavy metals by loading iron sulfide with high reactivity on the surface of the adsorbent, and can achieve the effect of deep purification by removing residual high-valence anions at the same time by utilizing the electrostatic attraction effect on the surface of the adsorbent.
5. The FeS/LDH synthesized by the method has stronger selectivity on heavy metal anions, and the FeS/LDH contains NO through the test of an ion competitive adsorption experiment 3 - 、SO 4 2- 、Cl - And CO 3 2- The adsorbent can still keep high removal rate of Cr (VI), as (V) and Sb (V) in the solution.
6. After adsorbing heavy metal anions, the FeS/LDH synthesized by the method is washed by hydrochloric acid for a short time, can be recycled for at least more than 5 times, the removal rate can be kept above 90% under the optimal pH (pH = 3), and the removal efficiency can be kept at least 60% in alkaline water. In addition, the adsorbent can also adjust the pH of the water body, the adsorbent is added into the water body containing heavy metal anions with the initial pH of 3-10, and after full adsorption, the pH of the water body can be adjusted to 6-9, which is beneficial to the adjustment of ecological environment.
Drawings
FIG. 1 is a graph of the adsorption capacity of FeS/LDH for Cr (VI) at various starting concentrations in example 1;
FIG. 2 shows examples 2 to 5: a XRD patterns of FeS/LDH obtained at different calcination temperatures; b, the removal rate of Cr (VI) by FeS/LDH obtained at different calcination temperatures;
FIG. 3 shows the results of example 6: a XRD pattern at different ratios of FeS to LDH; b, adsorption kinetics of FeS and LDH in different proportions;
FIG. 4 is the adsorption capacity of FeS/LDH for Cr (VI) at different starting pH's in example 7;
FIG. 5 is the adsorption capacity after FeS/LDH acid wash cycle of example 9.
Detailed Description
The present invention is described in detail below with reference to specific examples, but the present invention is not limited thereto in any way.
The reagents and measurement methods used in the following examples may be commercially available products and conventional methods, which can be routinely obtained by those skilled in the art, unless otherwise specified.
The main steps in the following examples include:
(1) Introducing nitrogen into the ultrapure water for at least 30min to sufficiently remove dissolved oxygen contained in the water body, and then adding quantitative Fe (II) salt and Fe (III) salt reagents;
(2) Ultrasonically dispersing the solution obtained in the step (1) for 10min to fully dissolve Fe (II) salt and Fe (III) salt, then adding NaOH solution to adjust the pH value to about 8, and continuously stirring for more than 30 min;
(3) Continuously injecting a sulfur precursor solution under stirring in a nitrogen atmosphere for full reaction, then centrifuging the reaction product at the rotating speed of 6000rpm, washing and drying the precipitate in vacuum for 4 hours, wherein the obtained yellow powder is the precursor of the final product;
(4) Calcining the mixture for 2 to 4 hours in a tubular furnace at the temperature of between 150 and 300 ℃ in a nitrogen environment to obtain the final adsorbent FeS/LDH.
Example 1
Introducing nitrogen gas into 800mL of ultrapure water for 30min to remove dissolved oxygen, and weighing 1.9881g of FeCl 2 ·4H 2 O and 1.212g Fe (NO) 3 ) 3 ·9H 2 Dissolving O in ultrapure water, performing ultrasonic treatment for 10min to fully disperse O, and continuously stirring for 30min. Continuously injecting 1mol/L NaOH solution into the solution at a speed of 1ml/min under the condition of introducing nitrogen until the pH value is stabilized to 8, continuously stirring for reacting for 2h, injecting the solution dissolved with 1.5g thioacetamide into the reaction solution for reacting for 2h, centrifugally separating the precipitate from the reacted solution at 6000rpm, sequentially washing the separated precipitate with ultrapure water and acetone, and then drying the precipitate in vacuum at 60 ℃ for 4h. And transferring the dried powder and the dried powder into an alumina crucible, and calcining the powder for 3h in a tube furnace at 200 ℃ in a nitrogen atmosphere to obtain the final FeS/LDH black powder.
Adsorption test (taking Cr (VI) as an example):
40ml of 40 mg/L-300 mg/L Cr (VI) solution is put into a 50ml centrifuge tube respectively, 20mg of FeS/LDH is weighed and added into the Cr (VI) solution, the mixture is sealed in a shaker at 25 ℃ and shaken for 3h, the removal rate (adsorption capacity) is shown in figure 1, and the adsorption capacity of the mixture on Cr (VI) can reach more than 200 mg/g.
Example 2
A synthesis method of FeS/LDH nano-adsorbent is characterized in that Fe (II) and Fe (III) molysite are mixed with NaOH and thioacetamide according to stoichiometric ratio to prepare a precursor, and then the precursor is calcined at low temperature to obtain the FeS/LDH nano-adsorbent, and the method comprises the following specific operation steps:
(1) Weighing 12mmol FeCl 2 ·4H 2 Dissolving O in 800mL deoxidized ultrapure water, and weighing 4mmol FeCl 3 ·6H 2 Adding O into the solution, dispersing in the solution by ultrasonic treatment for 10min, continuously stirring for 30min, continuously introducing nitrogen into the mixed solution, injecting 1mol/L NaOH solution at a speed of 1ml/min to adjust the pH value to 8, and reacting for 1h under magnetic stirring. Then injecting a solution in which 32mmol of thiourea is dissolved into the reaction solution for reaction for 2 hours;
(2) Centrifuging the reacted solution at 6000rpm to separate precipitate, sequentially cleaning the separated precipitate with ultrapure water and acetone, and vacuum drying at 60 deg.C for 4h to obtain precursor powder;
(3) And transferring the dried precursor powder into an alumina crucible, and calcining for 2h in a tubular furnace at 200 ℃ in a nitrogen atmosphere to obtain the final FeS/LDH black powder.
Example 3
Essentially the same as in example 2, except that the ferrous salt solution used was (NH) 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O, and the sulfur precursor is sodium thiosulfate.
Example 4
Essentially the same as in example 2, except that the ferrous salt solution used was FeSO 4 ·7H 2 O, the calcining temperature adopted is 300 ℃.
Example 5
Essentially the same as in example 2, except that the sulfur precursor solution used was thiourea.
The final samples obtained in examples 2-5 were tested to have amorphous FeS (as shown in fig. 2 a), and when the calcination temperature reached 400 c, the FeS crystals grew, thereby inhibiting the removal efficiency of heavy metals (as shown in fig. 2 b). Because different ferrous salts have different anions, the finally formed FeS/LDH has different interlayer anions, and the ion exchange effect on different heavy metal anions is slightly different according to the selected ferrous salts.
Example 6
A synthesis method of a FeS/LDH nano adsorbent for controlling FeS crystallinity comprises the following specific steps:
(1) Weighing 12mmol FeCl 2 ·4H 2 O and 4mmol FeCl 3 ·6H 2 Dissolving O in 800ml of deoxidized ultrapure water, respectively injecting 20ml,40ml and 80ml of 1mol/L NaOH solution (so that the doses of hydrotalcite-like structures formed in the final samples are different, and are referred to as 1;
(2) Centrifuging the reacted solution at 6000rpm respectively to separate precipitates, sequentially cleaning the separated precipitates with ultrapure water and acetone, and performing vacuum drying at 60 ℃ for 4h to obtain precursor powder containing LDH in different proportions;
(3) And transferring the dried precursor powder into an alumina crucible, and calcining for 2h in a tubular furnace at 200 ℃ in a nitrogen atmosphere to obtain FeS/LDH black powder with different crystal forms.
In the final sample obtained, the iron sulfide in the sample of ratio 1 2 The iron sulfide in the samples 1.
The prepared sample is added into a solution containing heavy metal anion Cr (VI), the adsorption reaction is 30min, the deep purification capacity of the 1. The 1.
Example 7
The application of the FeS/LDH nano adsorbent in heavy metal anion-containing solutions with different pH values comprises the following specific steps:
(1) 10 groups of 50mg/L heavy metal anion (Cr (VI)) solutions were magnetically stirred, wherein 5 groups were adjusted to pH 2, 3, 4, 5, 6 with 0.5mol/L hydrochloric acid, respectively, and the other 5 groups were adjusted to pH 7, 8, 9, 10, 11 with 0.5mol/L NaOH solution, respectively. Performing the adsorption test according to the operation steps of the adsorption test in example 1, wherein it should be noted that the reaction time in this example is prolonged to 24 hours, so that the reaction is sufficient and the pH of the adsorbed water is stable;
(2) Standing and precipitating the solution reacted in the step (1) for a period of time, taking supernate, filtering the supernate by using a filter head with the diameter of 0.22 mu m, carrying out quantitative analysis on heavy metal elements in the supernate by using an ICP-OES instrument, and simultaneously detecting the pH value of the solution after the reaction is finished;
the results of the experiment, as shown in fig. 4, show that under the condition of initial pH =3, feS/LDH has the best effect of removing heavy metal anions, close to 100%.
Example 8
The application of the FeS/LDH nano adsorbent in heavy metal anion-containing solutions with different pH values comprises the following specific steps: treating the solution containing heavy metal anion arsenic, putting 40ml of pentavalent arsenic solution with the initial concentration of 50mg/L into a 50ml centrifuge tube, weighing 20mg of FeS/LDH, adding into the arsenic solution, and carrying out oscillation reaction at room temperature for 30min.
Example 9
The application of the FeS/LDH nano adsorbent in circularly treating the heavy metal-containing anion solution comprises the following specific steps:
(1) FeS/LDH black powder was prepared according to the synthesis method in example 1 and used for an adsorption experiment of 50mg/L heavy metal anion (Cr (VI)) containing solution, and the mixture was allowed to stand for precipitation after 3 hours of reaction;
(2) Separating the supernatant and the black precipitate in the step (1), adding 10ml of 0.05mol/L hydrochloric acid into the precipitate, shaking for about 30min to desorb the heavy metal complex adsorbed on the surface of the FeS/LDH into the hydrochloric acid solution, standing for precipitation, and filtering to obtain the recycled FeS/LDH adsorbent;
(3) After the adsorbent obtained in the step (2) is adopted to carry out repeated adsorption tests, desorbing by using 0.05mol/L hydrochloric acid again to achieve the effect of recycling the FeS/LDH adsorbent;
after 5 times of cycle tests, the adsorbent still can achieve a removal effect (shown in figure 5) of more than 90% on heavy metal-containing anion solution with the initial concentration of 20mg/L, and still has a good adsorption effect after multiple cycles, so that the use cost of the adsorbent can be greatly reduced.
The embodiments described above are intended to facilitate a person of ordinary skill in the art in understanding and using the invention. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims (10)

1. The FeS/LDH nano-adsorbent is characterized in that the nano-adsorbent is based on LDH, and amorphous iron sulfide is loaded on the surface of the nano-adsorbent.
2. The FeS/LDH nano-adsorbent as claimed in claim 1, wherein the nano-adsorbent has a particle size of 20-200 nm and a specific surface area of 80-150 m 2 (ii)/g; at pH<At 8, the surface Zeta potential of the adsorbent exhibits positive electrical properties.
3. A method for the synthesis of a FeS/LDH nanoadsorbent according to claim 1 or 2, comprising the steps of:
s1: dissolving ferric salt in deoxidized ultrapure water, fully dissolving the deoxidized ultrapure water by ultrasonic stirring, injecting and adding a NaOH solution, continuously stirring and adjusting the pH value to 8, adding a sulfur precursor solution, and fully reacting under the protection of inert gas;
s2: centrifuging the solution reacted in the step S1, washing and drying the precipitate to obtain precursor powder;
s3: and (3) calcining the precursor powder obtained in the step (S2) in an inert gas atmosphere to obtain the FeS/LDH nano-adsorbent.
4. The synthesis method of the FeS/LDH nano-adsorbent as claimed in claim 3, wherein the iron salt in step S1 comprises Fe (II) salt and Fe (III) salt; the Fe (II) salt is FeCl 2 ·4H 2 O、(NH 4 ) 2 Fe(SO 4 ) 2 ·6H 2 O and FeSO 4 ·7H 2 One or more of O; the Fe (III) salt is FeCl 3 ·6H 2 O、Fe(NO 3 ) 3 ·9H 2 O and Fe 2 (SO 4 ) 3 ·5H 2 One or more of O; the molar ratio of Fe (II) salt to Fe (III) salt is 3.
5. The synthesis method of a FeS/LDH nano-adsorbent as claimed in claim 3, wherein the concentration of the NaOH solution is 1-4 mol/L, the injection rate is 1-2 mL/min, and the stirring time is at least 30min.
6. The synthesis method of a FeS/LDH nano-adsorbent as claimed in claim 3, wherein the sulfur precursor solution in step S1 is one or more of thioacetamide, thiourea and sodium thiosulfate; the sulfur precursor solution is added according to the molar ratio of Fe (II) to S of 1.
7. The synthesis method of the FeS/LDH nano-adsorbent as claimed in claim 3, wherein the reaction time in step S1 is 2-4 h.
8. The synthesis method of the FeS/LDH nano-adsorbent as claimed in claim 3, wherein the drying in step S2 is vacuum drying at a temperature of 40-60 ℃.
9. The synthesis method of the FeS/LDH nano-adsorbent as claimed in claim 3, wherein the calcination temperature in step S3 is 150-300 ℃ and the calcination time is 2-4 h.
10. Use of the FeS/LDH nano-adsorbent of claim 1 or 2 for removing heavy metal anions from water.
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