Adsorbent capable of removing arsenic in wastewater and preparation method thereof

Abstract

The invention provides an adsorbent for removing arsenic in wastewater and a preparation method thereof, and belongs to the technical field of wastewater treatment. The preparation method of the adsorbent for removing arsenic in wastewater comprises the following steps: pretreating straws to obtain an activated carbon raw material; roasting the activated carbon raw material to obtain activated carbon; the activated carbon is soaked in phosphoric acid for modification, and modified activated carbon is obtained; dissolving metal salt in water to obtain a metal salt solution; soaking the modified activated carbon in the metal salt solution, and finally performing ultrasonic treatment to obtain the adsorbent capable of removing arsenic in wastewater. The adsorbent capable of removing the arsenic in the wastewater is obtained by adopting a mode of compounding the activated carbon and the metal oxide, the adsorption capacity and the adsorption efficiency of the adsorbent are improved by utilizing dual adsorption of the activated carbon and the metal oxide on the arsenic, and meanwhile, the activated carbon is modified to improve active sites and a gap structure of the activated carbon; the adsorption efficiency is further improved.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, and in particular to an adsorbent capable of removing arsenic from wastewater and a preparation method thereof. Background Art

[0002] Arsenic is a toxic element that is widely present in nature. In water bodies, arsenic mainly exists in the form of inorganic arsenic (trivalent arsenic and pentavalent arsenic) and organic arsenic. After arsenic enters the human body, it will interfere with the body's metabolic process. Long-term exposure to arsenic-containing sewage environment, drinking or contact with arsenic-containing sewage, will cause serious harm to human health. For example, it can cause skin lesions such as pigmentation, hyperkeratosis, and may even cause skin cancer. At the same time, arsenic can also have adverse effects on the human nervous system, cardiovascular system, and urinary system, leading to diseases such as peripheral neuropathy, arrhythmia, and renal damage.

[0003] From an ecological and environmental perspective, arsenic-containing wastewater discharged into natural water bodies will cause toxicity to aquatic organisms. It will affect the photosynthesis and growth of aquatic plants, and threaten the reproduction, growth and survival of aquatic animals such as fish. For example, high concentrations of arsenic can damage the gill tissue of fish, affect their respiratory function, and then lead to fish death, destroying the balance of the aquatic ecosystem.

[0004] At present, the traditional methods for removing arsenic include chemical precipitation, oxidation-reduction, evaporation concentration, electrolysis, ion exchange resin, etc. However, there are many problems in the practical application of the above methods, such as large investment, high operating cost, troublesome operation and management, secondary pollution, and failure to solve the problem of water resource reuse, etc. Moreover, when treating low-concentration arsenic-containing wastewater, a large amount of reagents need to be added, the operating cost is high, and the removal rate is low. The biological adsorption method is currently widely used because of its advantages of high efficiency and low price, wide adaptability to pH and temperature, good selectivity, and good treatment effect on low-concentration arsenic-containing wastewater. Commonly used adsorbents include activated alumina, activated carbon, etc., but these adsorbents generally have low adsorption capacity, low arsenic removal efficiency, poor mechanical strength, high cost, etc., which restricts the promotion and application of the biological adsorption method.

[0005] Based on this, it is of great practical significance to provide a new adsorbent with large adsorption capacity and high arsenic removal efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide an adsorbent capable of removing arsenic from wastewater and a preparation method thereof, aiming to solve the technical problems of low adsorption capacity and low removal efficiency of commonly used adsorbents in the prior art.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing an adsorbent capable of removing arsenic from wastewater, comprising the following steps:

[0009] Pre-treating the straw to obtain activated carbon raw material;

[0010] calcining the activated carbon raw material to obtain activated carbon;

[0011] The activated carbon is immersed in phosphoric acid for modification to obtain modified activated carbon;

[0012] Dissolving a metal salt in water to obtain a metal salt solution;

[0013] The modified activated carbon is immersed in the metal salt solution, and finally subjected to ultrasonic treatment to obtain the adsorbent capable of removing arsenic from wastewater.

[0014] Furthermore, the pretreatment is to wash the straw and then crush and sieve it.

[0015] Furthermore, the particle size of the activated carbon is 100 to 300 μm.

[0016] Furthermore, the calcination temperature is 450-600° C. and the calcination time is 35-45 minutes.

[0017] Furthermore, the mass concentration of the phosphoric acid is 50-60%.

[0018] Furthermore, the mass ratio of phosphoric acid to activated carbon in the modification is 1-2:1-6, and the modification time is 2-4 hours.

[0019] Furthermore, the metal salt is one or more of iron oxide, aluminum oxide and aluminum oxide, and the concentration of the metal salt solution is 1 to 1.5 mol / L.

[0020] Furthermore, the ratio of modified activated carbon to metal salt solution in the soaking is 1:2-4.

[0021] Furthermore, the conditions of the ultrasonic treatment are: power of 300-400w, time of 20-30 minutes, temperature of 40-50°C

[0022] The present invention also provides an adsorbent obtained by the preparation method of the adsorbent capable of removing arsenic from wastewater described in the above technical solution, and the adsorbent can be used to remove arsenic from wastewater with an arsenic content of 0 to 100 mg / L.

[0023] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0024] (1) The present invention adopts a composite method of activated carbon and metal oxide to prepare an adsorbent for removing arsenic, and the metal oxide is loaded on the activated carbon. At the same time, the large specific surface area of ​​the activated carbon is used to physically adsorb the arsenic in the wastewater, and the chemical activity of the metal oxide is used to chemically adsorb the arsenic. The double adsorption makes the adsorbent have a higher adsorption amount and adsorption efficiency; further, the present invention adopts ultrasonic treatment to make the combination of activated carbon and metal oxide more compact, so that the activated carbon and metal oxide will not fall off during the adsorption process of arsenic to affect the adsorption efficiency and adsorption amount;

[0025] (2) The present invention modifies the activated carbon by using an acid solution to introduce acidic functional groups, thereby enhancing the activated carbon's adsorption capacity for arsenic in wastewater; at the same time, the active sites therein are adjusted, the pore structure of the activated carbon is adjusted, and the adsorption performance is improved;

[0026] (3) The present invention uses straw as the raw material of activated carbon, realizes the utilization of straw, and performs secondary utilization of straw, which is more green and environmentally friendly. The raw material is easily available and cheap, which is convenient for further production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The present invention is a flow chart of the preparation method of the adsorbent capable of removing arsenic from wastewater. DETAILED DESCRIPTION

[0028] From an ecological and environmental perspective, arsenic-containing wastewater discharged into natural water bodies will cause toxicity to aquatic organisms. It will affect the photosynthesis and growth of aquatic plants, and threaten the reproduction, growth and survival of aquatic animals such as fish. For example, high concentrations of arsenic can damage the gill tissue of fish, affect their respiratory function, and then lead to fish death, destroying the balance of the aquatic ecosystem.

[0029] At present, traditional arsenic removal methods include chemical precipitation, oxidation-reduction, evaporation concentration, electrolysis, ion exchange resin, etc. However, there are many problems in the practical application of the above methods, such as: large investment, high operating cost, troublesome operation and management, secondary pollution, and failure to solve the problem of water resource reuse, etc. Moreover, when treating low-concentration arsenic-containing wastewater, a large amount of reagents need to be added, the operating cost is high, and the removal rate is low. The biological adsorption method is currently widely used because of its advantages such as high efficiency and low price, wide adaptability to pH and temperature, good selectivity, and good treatment effect on low-concentration arsenic-containing wastewater. Commonly used adsorbents include activated alumina, activated carbon, etc., but these adsorbents generally have low adsorption capacity, low arsenic removal efficiency, poor mechanical strength, high cost, etc., which restrict the promotion and application of the biological adsorption method. Based on the above:

[0030] The present invention provides a method for preparing an adsorbent capable of removing arsenic from wastewater, comprising the following steps:

[0031] Pre-treating the straw to obtain activated carbon raw material;

[0032] calcining the activated carbon raw material to obtain activated carbon;

[0033] The activated carbon is immersed in phosphoric acid for modification to obtain modified activated carbon;

[0034] Dissolving a metal salt in water to obtain a metal salt solution;

[0035] The modified activated carbon is immersed in the metal salt solution, and finally subjected to ultrasonic treatment to obtain the adsorbent capable of removing arsenic from wastewater.

[0036] Pre-treating the straw to obtain activated carbon raw material;

[0037] The present invention uses agricultural waste straw as a raw material for preparing activated carbon, which can realize the resource utilization of straw and reduce the environmental pollution caused by straw burning and stacking. At the same time, the straw is low in cost and is convenient for producing adsorbents. The present invention does not specifically limit the type of straw, and any type of straw known to those skilled in the art can be used. In the embodiment of the present invention, wheat straw or corn straw is preferably used.

[0038] The invention firstly cleans the straw to remove impurities therein, and then crushes the straw to facilitate subsequent roasting.

[0039] In the present invention, the pretreatment is preferably to wash the straw and then crush and sieve it. In the present invention, the straw is preferably crushed into straw particles with a particle size of 0.3 to 0.5 mm.

[0040] The activated carbon raw material is calcined to obtain activated carbon.

[0041] In the present invention, the particle size of the activated carbon is preferably 100 to 300 μm, more preferably 100 to 200 μm.

[0042] In the present invention, the calcination temperature is preferably 450 to 600° C., more preferably 450 to 500° C., and the calcination time is preferably 35 to 45 minutes, more preferably 35 to 40 minutes.

[0043] The activated carbon is immersed in phosphoric acid for modification to obtain modified activated carbon;

[0044] The present invention preferably uses phosphoric acid to modify the activated carbon, introduces acidic functional groups, adjusts the void structure that is easily generated in the activated carbon, and enhances the activated carbon's adsorption capacity for arsenic in wastewater; at the same time, adjusts the active sites therein, adjusts the void structure of the activated carbon, and improves the adsorption performance.

[0045] In the present invention, the mass concentration of the phosphoric acid is preferably 50 to 60%, and more preferably 50 to 55%.

[0046] In the present invention, the mass ratio of phosphoric acid to activated carbon in the modification is preferably 1-2:1-6, more preferably 1-2:1-4, and the modification time is preferably 2-4 hours, more preferably 2-3 hours.

[0047] Dissolving a metal salt in water to obtain a metal salt solution;

[0048] In the present invention, the metal salt is preferably one or more of iron oxide, aluminum oxide and aluminum oxide, and the concentration of the metal salt solution is preferably 1 to 1.5 mol / L, and more preferably 1 to 1.2 mol / L. When a plurality of metal salts are used to prepare the metal salt solution, the present invention does not impose any particular limitation on the usage ratio of the different metal salts, and any ratio or ratio well known to those skilled in the art can be used.

[0049] The modified activated carbon is immersed in the metal salt solution, and finally subjected to ultrasonic treatment to obtain the adsorbent capable of removing arsenic from wastewater.

[0050] The present invention adopts ultrasonic treatment to mix activated carbon and metal salt, and loads the metal salt on the activated carbon. The present invention simultaneously utilizes the larger specific surface area of ​​the activated carbon to physically adsorb arsenic in the wastewater, and utilizes the chemical activity of the metal oxide to chemically adsorb. The double adsorption enables the adsorbent to have higher adsorption capacity and adsorption efficiency. Furthermore, the present invention adopts ultrasonic treatment and further limits the parameters of the ultrasonic treatment to make the combination of the activated carbon and the metal oxide more compact, and the activated carbon will not fall off during the process of adsorbing arsenic to affect the adsorption efficiency and adsorption capacity.

[0051] In the present invention, the ratio of the modified activated carbon to the metal salt solution in the soaking is preferably 1:2-4, and more preferably 1:2-3.

[0052] In the present invention, the conditions for the ultrasonic treatment are preferably: power of 300-400w, time of 20-30 minutes, temperature of 40-50°C; more preferably, power of 300-350w, time of 20-25 minutes, temperature of 40-45°C.

[0053] The present invention also provides an adsorbent obtained by the preparation method of the adsorbent capable of removing arsenic from wastewater described in the above technical solution.

[0054] In the present invention, unless otherwise specified, the required raw materials for preparation are all commercially available products well known to those skilled in the art.

[0055] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0056] Example 1

[0057] (1) Selecting discarded corn stalks, washing and crushing them to obtain 0.3-0.5 mm corn stalk particles, which are activated carbon raw materials;

[0058] (2) roasting the corn stalk pellets at 450° C. for 35 minutes, and then sieving them to ensure that the particle size of the activated carbon obtained is 100 μm;

[0059] (3) immersing the activated carbon in phosphoric acid with a mass concentration of 50% in a mass ratio of 1:3 and mixing the mixture evenly for modification. The modification time is 2 hours, and then the activated carbon is taken out and washed with water to obtain modified activated carbon;

[0060] (4) placing iron oxide in water to prepare an iron oxide solution with a concentration of 1 mol / L;

[0061] (5) The modified activated carbon is immersed in the iron oxide solution at a mass ratio of 1:2 for ultrasonic treatment. The power of the ultrasonic treatment is 300 W, the time is 20 minutes, and the temperature is 40°C. After the treatment, it is filtered and cleaned to obtain the adsorbent that can remove arsenic from wastewater.

[0062] Example 2

[0063] (1) Selecting discarded wheat straw, washing and crushing it to obtain 0.3-0.5 mm corn straw particles as activated carbon raw materials;

[0064] (2) roasting the corn stalk particles at 500° C. for 40 minutes, and then sieving them to ensure that the particle size of the activated carbon obtained is 200 μm;

[0065] (3) immersing the activated carbon in phosphoric acid with a mass concentration of 55% in a mass ratio of 1:2 and mixing the mixture evenly for modification. The modification time is 3 hours, and then the activated carbon is taken out and washed with water to obtain modified activated carbon;

[0066] (4) placing iron oxide in water to prepare an iron oxide solution with a concentration of 1.2 mol / L;

[0067] (5) The modified activated carbon is immersed in the iron oxide solution at a mass ratio of 1:4 for ultrasonic treatment. The power of the ultrasonic treatment is 400 W, the time is 30 minutes, and the temperature is 50° C. After the treatment, it is filtered and cleaned to obtain the adsorbent that can remove arsenic from wastewater.

[0068] Example 3

[0069] (1) Selecting discarded corn stalks, washing and crushing them to obtain 0.3-0.5 mm corn stalk particles, which are activated carbon raw materials;

[0070] (2) roasting the corn stalk particles at 600° C. for 45 minutes, and then sieving them to ensure that the particle size of the activated carbon obtained is 300 μm;

[0071] (3) immersing the activated carbon in phosphoric acid with a mass concentration of 60% in a mass ratio of 1:1 and mixing the mixture evenly for modification. The modification time is 4 hours, and then the activated carbon is taken out and washed with water to obtain modified activated carbon;

[0072] (4) placing iron oxide in water to prepare an iron oxide solution with a concentration of 1.5 mol / L;

[0073] (5) The modified activated carbon is immersed in the iron oxide solution at a mass ratio of 1:3 for ultrasonic treatment. The power of the ultrasonic treatment is 350W, the time is 30 minutes, and the temperature is 50°C. After the treatment, it is filtered and cleaned to obtain the adsorbent that can remove arsenic from wastewater.

[0074] Application Example 1

[0075] The adsorbent for removing arsenic from wastewater obtained in Example 1 was used for 1000 mL and 9.28 mg / L of As 3+ The adsorption conditions of the solution were pH = 7.0, T = 40°C, and the adsorption equilibrium was reached within 1 hour, with the maximum adsorption rate being 93.5%.

[0076] In summary, the adsorbent capable of removing arsenic from wastewater obtained by the preparation method of the present invention has a high adsorption capacity for arsenic-containing wastewater.

[0077] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an adsorbent capable of removing arsenic from wastewater, characterized in that: The following steps are involved: Pre-treating the straw to obtain activated carbon raw material; calcining the activated carbon raw material to obtain activated carbon; The activated carbon is immersed in phosphoric acid for modification to obtain modified activated carbon; Dissolving a metal salt in water to obtain a metal salt solution; The modified activated carbon is immersed in the metal salt solution, and finally subjected to ultrasonic treatment to obtain the adsorbent capable of removing arsenic from wastewater.

2. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The pretreatment is to wash the straw and then crush and sieve it.

3. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 2, characterized in that: The particle size of the activated carbon is 100 to 300 μm.

4. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The calcination temperature is 450-600° C. and the calcination time is 35-45 minutes.

5. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The mass concentration of the phosphoric acid is 50-60%.

6. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The mass ratio of phosphoric acid to activated carbon in the modification is 1-2:1-6, and the modification time is 2-4 hours.

7. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The metal salt is one or more of iron oxide, aluminum oxide and aluminum oxide, and the concentration of the metal salt solution is 1-1.5 mol / L.

8. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The ratio of modified activated carbon to metal salt solution used in the soaking is 1:2-4.

9. The method for preparing an adsorbent capable of removing arsenic from wastewater according to claim 1, characterized in that: The conditions of the ultrasonic treatment are: power of 300-400W, time of 20-30 minutes, temperature of 40-50°C.

10. An adsorbent obtained by the preparation method of an adsorbent capable of removing arsenic from wastewater according to any one of claims 1 to 9, characterized in that: The adsorbent can be used to remove arsenic in wastewater with an arsenic content of 0 to 100 mg / L.

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