CN113856621A

CN113856621A - Preparation and application of iron-sulfur co-doped biochar material for simultaneously removing lead-arsenic composite pollution

Info

Publication number: CN113856621A
Application number: CN202110933025.7A
Authority: CN
Inventors: 林亲铁; 陈怡君; 温小情; 李家琦; 吴礼滨; 杨丹琳; 何金
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2021-08-13
Filing date: 2021-08-13
Publication date: 2021-12-31
Anticipated expiration: 2041-08-13
Also published as: CN113856621B

Abstract

The invention relates to preparation and application of an iron-sulfur co-doped biochar material for simultaneously removing arsenic-lead composite pollution. The iron-sulfur co-doped biochar material is prepared by the steps of carrying out magnetic stirring on straw powder and turbid liquid containing ferrous sulfate and sodium thiosulfate for 10-36 hours according to the solid-to-liquid ratio of (7-12) g:100mL, fully mixing, and carrying out pyrolysis for 1-3 hours at 250-450 ℃ after freeze drying. The mol ratio of ferrous sulfate to sodium thiosulfate in the suspension is (0.7-2): 1. the iron-sulfur co-doped biochar can simultaneously and efficiently adsorb arsenic and lead in the composite polluted water body, the optimal removal rate of As (III) in 24 hours reaches more than 96%, and the removal rate of Pb (II) reaches more than 93%; and the removal rate of As (III) and Pb (II) can be kept above 90% under the condition that the pH value is 3-6. The iron-sulfur co-doped biochar is obtained by primary calcination after raw material impregnation, is simple to operate, has a remarkable arsenic-lead removal effect, and has practical significance for treating industrial wastewater with arsenic-lead combined pollution.

Description

Preparation and application of iron-sulfur co-doped biochar material for simultaneously removing lead-arsenic composite pollution

Technical Field

The invention belongs to the technical field of heavy metal treatment, and relates to preparation and application of a modified biochar material for simultaneously removing lead-arsenic composite pollution.

Background

Lead and arsenic are widely present in the natural world, and as the second five toxic element (cadmium, mercury, arsenic, lead, chromium), the influence on the environment and human health safety is widely concerned. The arsenic-lead composite pollution in water is mainly generated in the industrial processes of smelting, mining, electroplating and the like. Trivalent arsenic As (III) in water has higher toxicity, mobility and solubility. Lead is usually present in the wastewater in the form of Pb (ii). The arsenic-lead composite pollution is not easy to be chemically or biologically degraded, can be enriched in a human body by being taken, and has great harm to organs of the human body, such as stomach, intestinal tract, liver, kidney and the like. In order to mitigate the effects of arsenic-lead co-pollution on human health, the World Health Organization (WHO) established that the international maximum pollution level of arsenic in drinking water is 10 ppb and lead is 10 ppb. Therefore, remediation of arsenic and lead contamination in aqueous solutions is critical.

At present, a variety of purification techniques such As chemical precipitation, electrochemical treatment, membrane separation, ion exchange and adsorption have been used to treat As (III) and Pb (II) in wastewater. Compared with the chemical precipitation method, the method has the limitations of large amount of sludge generation, high cost of electrochemical and membrane separation and the like, and the adsorption is considered to be one of the technologies with the most application prospect due to the special advantages of simple operation, high cost benefit, no need of sludge treatment and the like.

Biochar prepared from agricultural wastes such as straws has the advantages of developed pore structure, stable fat chain structure, wide source and the like, and is widely used as an economic adsorbent. Compared with unmodified biochar, the iron-based and sulfur-based modified biochar has better adsorption capacity to As (III) and Pb (II). Research has been carried out to confirm the feasibility of carrying iron and sulfur together with charcoal: (1) chinese patent application (publication No. CN 111229160A) proposes a preparation method of biochar simultaneously carrying ferrous sulfide and zero-valent iron, which is obtained by subjecting fired corn straw biochar to hydrophilic treatment and then continuously stirring with ferrous sulfate and sodium sulfide in an anaerobic condition, so that the material has good adsorption performance on lead in wastewater. However, the method only considers the removal of lead by materials singly, and the application range is quite limited because the combined pollution of various heavy metals usually exists in the actual wastewater. (2) Chinese patent application (publication No. CN 111925806A) proposes a preparation method of a sulfur-doped nano ferroferric oxide/biochar composite material, ferroferric oxide load and sulfur modification are combined, so that the material has high-efficiency adsorption performance on arsenic and lead, but the preparation process needs multiple times of high-temperature calcination, the sulfur modification process needs continuous stirring in an anaerobic environment, the procedure is complicated, the cost is high, the requirement on preparation conditions is strict, and the large-scale production in practical application is not facilitated.

Disclosure of Invention

Just like most of the existing iron and sulfur co-doped materials, the zero-valent iron sulfide, the nano iron sulfide and the like have the problems of easy oxidation, agglomeration and the like, nitrogen is introduced and calcination is carried out for many times in the preparation process, the generated material is very easy to oxidize and needs anaerobic storage, the preparation conditions are harsh, the cost is high, and only the removal of single heavy metal is usually considered. In order to overcome the problems, the invention provides a preparation method and an application method of iron-sulfur co-doped biochar which can simultaneously load iron-based and sulfur-based functional groups on biochar through one-time calcination and can simultaneously and efficiently remove arsenic and lead pollution. Through repeated experimental research, the invention creatively utilizes the reaction of ferrous sulfate and sodium thiosulfate in the process of soaking the biomass, so that iron oxide and iron sulfide can be loaded on the biochar through calcination, and the final product is stable and easy to store and has the capability of efficiently removing arsenic and lead.

The invention provides a preparation method of a modified biochar material for simultaneously removing lead-arsenic composite pollution, which comprises the following steps: the modified biochar material is iron and sulfur co-doped biochar formed by pyrolyzing ferrous sulfate, sodium thiosulfate and biomass. And (3) fully mixing the straw powder with the suspension of ferrous sulfate and sodium thiosulfate through magnetic stirring, freeze-drying, calcining at 250-450 ℃ in a protective atmosphere, and keeping the temperature for 1-3 hours to obtain a pyrolysis product, namely the iron-sulfur co-doped biochar.

In one embodiment, the straw selected is rice straw.

In a specific embodiment, the solid-to-liquid ratio of the rice straw powder to the suspension is 5-15 g:100mL, preferably 7-12 g:100 mL.

In one embodiment, the molar ratio of ferrous sulfate to sodium thiosulfate in the suspension is controlled to be 0.5-2.5: 1, preferably 0.7-2: 1.

preferably, the suspension is freeze-dried after being magnetically stirred for 10 to 36 hours.

Preferably, the temperature rise rate is controlled to be 5-10 ℃/min during pyrolysis.

Preferably, the pyrolysis is carried out at 250-450 ℃ and the temperature is kept for 1-3 hours.

Preferably, the pyrolysis product is dried after washing impurities with deionized water.

The invention also provides application of the iron-sulfur co-doped biochar material in arsenic-lead composite polluted water. Further, adding the modified biochar into the As (III) and Pb (II) composite polluted wastewater according to 1-3 g/L for oscillation reaction, performing adsorption treatment, and measuring the concentrations of As (III) and Pb (II) by using the solution before and after the reaction.

Preferably, the application of the material in the As (III) and Pb (II) composite solution adjusts the initial pH value of the material to be 2-7, preferably 3-6.

Compared with the prior art, the invention has the following advantages: according to the invention, the straw powder, the suspension mixed by ferrous sulfate and sodium thiosulfate are fully soaked and mixed, and then the iron-sulfur co-doped biochar can be obtained through one-time calcination, so that the operation is simple, the cost is low, and the large-scale production and practical application are facilitated. The iron-sulfur co-doped biochar prepared by the invention can simultaneously and efficiently remove As (III) and Pb (II) in water and has better anti-interference capability on pH. Experiments prove that: the optimal removal rate of the material to As (III) in 24 hours reaches more than 96 percent, and the removal rate to Pb (II) reaches more than 93 percent; and in the pH range of 3-6, the removal rate of the As (III) Pb (II) by the iron-sulfur co-doped biochar is kept above 90%.

Drawings

FIG. 1 is an XPS picture of the material of example 1

FIG. 2 is a graph showing the influence of different initial pH values on the adsorption effects of As (III) and Pb (II) in example 2.

Detailed Description

The following examples are presented to further illustrate the present invention and are not to be construed as limiting the invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Reagents, methods and apparatus used in the present invention are conventional in the art unless otherwise indicated.

Example 1

Preparing iron and sulfur co-doped biochar: taking 10g of rice straw powder, adding the rice straw powder into 100mL of the rice straw powder containing the components in a molar ratio of 1: 1, magnetically stirring for 10 hours, and then freeze-drying. And putting the dried solid in a nitrogen atmosphere, pyrolyzing the solid for 2h at 300 ℃ at the heating rate of 5 ℃/min, cooling the solid, and washing the solid with deionized water for three times to obtain the iron-sulfur co-doped biochar (Fe/S-BC). Comparison was performed with unmodified biochar.

Preparation of unmodified biochar: putting the rice straw powder in a nitrogen atmosphere, pyrolyzing the powder for 2h at 300 ℃ at the heating rate of 5 ℃/min, cooling the pyrolysis product, and washing the cooled pyrolysis product with deionized water for three times to obtain the unmodified Biochar (BC).

The BET test results are shown in table 1, and the XPS results are shown in fig. 1.

TABLE 1 BET test results of iron and sulfur co-doped biochar and unmodified biochar

Absorbent	Specific surface area (m)²/g)	Pore volume (cm)²/g)	Pore size (nm)
				BC	20.18	0.013	21.31
Fe/S-BC	121.90	0.058	17.85

As can be seen from table 1 and fig. 1, the iron-sulfur co-doped biochar has a large specific surface area and pore volume by supporting iron and sulfur, and the removal of As and Pb can be further promoted by the iron-sulfur compound supported on the biochar.

Arsenic and lead removal experiment:

1. comparison of removal rates of different iron and sulfur co-doped biochar dosages

The prepared iron-sulfur co-doped biochar is applied to a composite solution of As (III) and Pb (II) with the initial concentration of 50mg/L, the initial pH value of the solution is adjusted to be 5, the iron-sulfur co-doped biochar is added according to the concentration of 1g/L, 2g/L and 3g/L, the solution is horizontally oscillated for 24 hours in a constant temperature water bath oscillator at the temperature of 25 ℃, the concentration of arsenic and lead in the treated solution is measured according to the method in the documents GB 7475-87, HJ 694-2014 and the like, the result is recorded, and the removal rate is calculated. The results are shown in Table 2 below,

TABLE 2 influence of different concentrations on As (III) and Pb (II) removal rate of composite solution

Adding amount of charcoal (g/L)	As (III) content (ppm) after treatment	As (III) removal Rate (%)	Pb (II) content (ppm) after treatment	Pb (II) removal Rate (%)
					1	2.145	95.71	3.265	93.47
2	1.610	96.78	0.730	98.54
					3	0.810	98.38	0.655	98.69

The results show that: the removal rate of the prepared biochar material on As (III) and Pb (II) is kept above 90%, and the removal rate is increased along with the increase of the adding amount. However, the added iron and sulfur co-doped biochar with 1g/L has reached higher arsenic and lead removal rates which respectively reach 95.71% and 93.47.

2. Comparison of removal rates at different initial pH conditions

Meanwhile, the same operation is carried out As above, but the initial pH of the composite solution of As (III) and Pb (II) is adjusted to 3, 4, 5 and 6 respectively, and then the adsorption experiment is carried out by adding the iron-sulfur co-doped biochar according to 1 g/L. After the experiment, the results were measured. The results are shown in FIG. 1.

It can be seen that the removal rates of As and Pb of the prepared iron-sulfur co-doped biochar for As (III) and Pb (II) reach over 90% under different pH values, which indicates that the iron-sulfur co-doped biochar has better anti-interference capability and adaptive range for the pH value.

Example 2

Preparing iron and sulfur co-doped biochar:

reference is made to example 1 with the following differences: the solid-liquid ratio of the rice straw powder to the suspension is 7g:100mL, the protective atmosphere is argon, and the heating speed is 10 ℃/min.

Arsenic and lead removal experiment: the procedure of example 1 was followed, wherein the iron-sulfur-codoped biochar was 1g/L, and the pH of the composite solution of As (III) and Pb (II) was 5. After the experiment, the percentage of arsenic and lead removal was determined. The results show that: the removal rate of As (III) at the reaction equilibrium was 93.66%, the removal rate of Pb (II) was 91.93%,

example 3

Preparing iron and sulfur co-doped biochar: reference is made to example 1 with the following differences: the molar ratio of ferrous sulfate to sodium thiosulfate in the suspension is 2: 1, the pyrolysis time was 3h, as in example 1.

Arsenic and lead removal experiment: the procedure of example 1 was followed, wherein the iron-sulfur-codoped biochar was 1g/L, and the pH of the composite solution of As (III) and Pb (II) was 5. After the experiment, the percentage of arsenic and lead removal was determined. The results show that: the As (III) removal rate at the reaction equilibrium was 94.21%, and the Pb (II) removal rate was 95.68%.

Example 4

Preparing iron and sulfur co-doped biochar: reference is made to example 1 with the following differences: the pyrolysis temperature was 350 ℃ and the pyrolysis time was 3h, as in example 1.

Arsenic and lead removal experiment: the procedure of example 1 was followed, wherein the iron-sulfur-codoped biochar was 1g/L, and the pH of the composite solution of As (III) and Pb (II) was 5. After the experiment, the percentage of arsenic and lead removal was determined. The results show that: the As (III) removal rate at the reaction equilibrium was 96.95%, and the Pb (II) removal rate was 91.27%.

Based on the above embodiment, the iron-sulfur co-doped biochar can simultaneously and efficiently remove arsenic and lead in a water body, wherein the iron-sulfur co-doped biochar material is added into an arsenic-lead composite solution according to 1g/L to achieve a high removal rate. The initial pH value of the arsenic-lead composite solution is 3-6, the pH value of the solution is adjusted, and the removal rate of the prepared iron-sulfur co-doped biochar on As (III) and Pb (II) is kept above 90%. The solid-liquid ratio of the straw powder to the suspension is 5-15 g:100mL, and the removal rate of As (III) and Pb (II) of the iron-sulfur co-doped biochar prepared by adjusting the using amount of the rice straw powder and the suspension is kept above 90%. The molar ratio of ferrous sulfate to sodium thiosulfate in the suspension is 0.5-2.5: 1, the removal rate of As (III) and Pb (II) of the prepared iron-sulfur co-doped biochar on the As (III) and Pb (II) is kept above 90 percent by adjusting the using amounts of ferrous sulfate and sodium thiosulfate.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations and simplifications are intended to be included in the scope of the present invention.

Claims

1. The preparation method of the iron-sulfur co-doped biochar material for simultaneously removing the lead-arsenic composite pollution is characterized by comprising the following steps of:

(1) adding straw powder into a suspension containing ferrous sulfate and sodium thiosulfate, wherein the solid-to-liquid ratio of the straw powder to the suspension is 5-15 g:100mL, preferably 7-12 g:100 mL; the molar ratio of ferrous sulfate to sodium thiosulfate in the suspension is 0.5-2.5: 1, preferably 0.7-2: 1;

(2) magnetically stirring the solution obtained in the step (1) for 10-36 hours, fully mixing, and freeze-drying;

(3) and placing the dried mixture in a protective atmosphere, calcining at 250-450 ℃ to obtain a carbonized product, and cleaning and drying to obtain the iron-sulfur co-doped biochar material.

2. The preparation method of the iron-sulfur co-doped biochar material for removing lead-arsenic composite pollution according to claim 1, which is characterized by comprising the following steps of: the straw powder is obtained by washing and drying rice straws, crushing and sieving.

3. The preparation method of the iron-sulfur co-doped biochar material for removing lead-arsenic composite pollution according to claim 1, which is characterized by comprising the following steps of: the protective atmosphere is nitrogen or argon.

4. The preparation method of the iron-sulfur co-doped biochar material for removing lead-arsenic composite pollution according to claim 1, which is characterized by comprising the following steps of: the calcination time at 250-450 ℃ is 1-3 hours.

5. The preparation method of the iron-sulfur co-doped biochar material for removing lead-arsenic composite pollution according to claim 1, which is characterized by comprising the following steps of: the temperature rise rate of the calcination is 5-10 ℃/min.

6. The application of the iron-sulfur co-doped biochar material obtained by the preparation method of any one of claims 1-5 in arsenic-lead composite polluted water.

7. The application of the iron and sulfur co-doped biochar material in the arsenic and lead composite polluted water body according to claim 6 is characterized in that the iron and sulfur co-doped biochar material obtained by the preparation method according to any one of claims 1 to 5 is added into an arsenic and lead composite solution for oscillation reaction.

8. The application of the iron and sulfur co-doped biochar material in the arsenic and lead composite polluted water body according to claim 7 is characterized in that the iron and sulfur co-doped biochar material is added into the arsenic and lead composite polluted water body according to 1-3 g/L.

9. The application of the iron and sulfur co-doped biochar material in the arsenic-lead composite water body according to claim 6 is characterized in that: and adjusting the initial pH value of the arsenic-lead composite polluted water body to be 2-7, preferably 3-6.