Method for removing heavy metals in water body

Abstract

The invention provides a method for removing heavy metals in a water body, and relates to the technical field of water treatment. The method for removing the heavy metals in the water body comprises the following steps: preliminarily removing suspended matters and part of the heavy metals; preparing a magnetic composite adsorbent; preparing a functionalized magnetic composite adsorbent; adding the functionalized magnetic composite adsorbent into a water body containing heavy metal ions, and carrying out adsorption reaction on a constant-temperature oscillator; after the adsorption reaction is finished, an adsorption system is separated by utilizing an external magnetic field, so that the functional magnetic composite adsorbent loaded with the heavy metal ions is quickly separated from the water body; and adding the separated adsorbent into a desorption solution, and stirring at a certain temperature to carry out desorption reaction, so that the heavy metal ions are desorbed and recovered from the surface of the adsorbent. The functionalized magnetic composite adsorbent prepared by the method has relatively high adsorption capacity and adsorption selectivity on various heavy metal ions, and can effectively remove heavy metal pollutants in a water body, and the removal rate can reach 95% or above.

Description

Technical Field

[0001] The invention relates to the technical field of water treatment, in particular to a method for removing heavy metals from water. Background Art

[0002] With the development of industrialization, heavy metal pollution in water bodies has become increasingly serious. Heavy metals such as lead (Pb), cadmium (Cd), mercury (Hg), and chromium (Cr) are extremely harmful to the ecological environment and human health.

[0003] At present, common methods for removing heavy metals from water bodies include chemical precipitation, ion exchange, adsorption, etc. Although the chemical precipitation method is simple to operate, it will produce a large amount of chemical sludge and the subsequent treatment cost is high; the ion exchange method has a good removal effect, but the exchange resin is expensive and the regeneration process is complicated; there are many types of adsorbents in the adsorption method, but some adsorbents have problems such as low adsorption capacity, poor adsorption selectivity, and difficulty in recycling and reuse. Therefore, it is of great practical significance to develop an efficient, economical, environmentally friendly and recyclable method for removing heavy metals from water bodies. Summary of the invention

[0004] 1. Technical issues to be resolved In view of the deficiencies of the prior art, the present invention provides a method for removing heavy metals in water bodies, which solves the problems raised by the above-mentioned background technology.

[0005] (II) Technical solution To achieve the above objectives, the present invention is implemented through the following technical solutions: A method for removing heavy metals from water bodies, comprising the following steps: Step 1: Preliminary removal of heavy metals: The wastewater is pumped into the regulating tank and the pH value is adjusted to 2-4. Composite flocculants are added to form large particle flocs to preliminarily remove suspended solids and some heavy metals. Step 2: Preparation of magnetic composite adsorbent: The Fe3O4 nanoparticles were compounded with chitosan to prepare a magnetic composite adsorbent; Step 3: Preparation of functionalized magnetic composite adsorbent: The prepared magnetic composite adsorbent is dispersed in an ethanol solution containing thioglycolic acid, and stirred for reaction to obtain a functionalized magnetic composite adsorbent; Step 4: Heavy metal adsorption: The functionalized magnetic composite adsorbent is added into water containing heavy metal ions, and the adsorption reaction is carried out on a constant temperature oscillator; Step 5: Heavy metal separation: After the adsorption reaction is completed, the adsorption system is separated by using an external magnetic field, so that the functionalized magnetic composite adsorbent loaded with heavy metal ions is quickly separated from the water body; Step 6: Desorption and recovery: The separated adsorbent is added to the desorption liquid and stirred at a certain temperature to carry out a desorption reaction, so that the heavy metal ions are desorbed and recovered from the surface of the adsorbent.

[0006] Preferably, in step 1, the pH value is adjusted to 2-4 by a pH regulator, and the pH regulator is citric acid or sulfuric acid; the composite flocculant is a composite of polyacrylamide and nano-silicon dioxide.

[0007] Preferably, in step 2, first, Fe3O4 nanoparticles are prepared by coprecipitation method, FeSO4 and FeCl3 are dissolved in deionized water at a molar ratio of 1:2, and under nitrogen protection, ammonia water is quickly added and stirred to react to obtain a black Fe3O4 nanoparticle suspension; then, a certain amount of chitosan is dissolved in a dilute acetic acid solution, the above-mentioned Fe3O4 nanoparticle suspension is added, stirred evenly, glutaraldehyde is added dropwise for cross-linking reaction, and after washing and drying, a magnetic composite adsorbent is obtained.

[0008] Preferably, in step three, the stirring reaction conditions are: stirring the reaction in a water bath at 50-60°C for 6-8 hours. After the reaction is completed, washing with deionized water and anhydrous ethanol, and drying in a vacuum drying oven at 60-70°C for 12 hours, so that the thioglycolic acid is loaded onto the surface of the magnetic composite adsorbent by chemical bonding to obtain a functionalized magnetic composite adsorbent.

[0009] Preferably, in step 4, the conditions for the adsorption reaction are: the pH value of the water body is 6-8, the adsorbent dosage is 0.5-1.5 g / L, the reaction time is 60-120 min, and the temperature is 25-35°C.

[0010] Preferably, in step six, the conditions of the desorption reaction are: the desorption liquid is selected from dilute hydrochloric acid or ethylenediaminetetraacetic acid solution, and the reaction is stirred in a water bath at 50-60°C for 2-3 hours. After the desorption is completed, the adsorbent is separated by a magnet; the desorption liquid is taken and the heavy metal ions therein are recovered by chemical precipitation.

[0011] (III) Beneficial effects The present invention provides a method for removing heavy metals from water bodies, which has the following beneficial effects: 1. Efficient removal: The functionalized magnetic composite adsorbent prepared by the present invention has a high adsorption capacity and adsorption selectivity for a variety of heavy metal ions, and can effectively remove heavy metal pollutants in water bodies, with a removal rate of more than 95%.

[0012] 2. Easy operation: The magnetic separation technology can quickly separate the adsorbent from the water body without complicated filtering or centrifugal operation, which reduces the operating cost and energy consumption. The adsorbent can be reused after desorption, and the heavy metal ions in the desorption liquid can also be recovered, which reduces resource waste and secondary pollution and meets the requirements of green chemistry. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the specific method flow of the present invention. DETAILED DESCRIPTION

[0014] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Embodiment 1:

[0015] like Figure 1 As shown, an embodiment of the present invention provides a method for removing heavy metals from water, comprising the following steps: Step 1: Preliminary removal of heavy metals: The wastewater is pumped into the regulating tank, and the pH value is adjusted to 2 by a pH adjuster, wherein citric acid is selected as the pH adjuster; and a composite flocculant is added, which is a composite of polyacrylamide and nano-silicon dioxide to form large-particle flocs, and preliminarily remove suspended matter and some heavy metals; Step 2: Preparation of magnetic composite adsorbent: The Fe3O4 nanoparticles were compounded with chitosan to prepare a magnetic composite adsorbent; specifically, 1.08g of FeSO4 and 2.7g of FeCl3 were dissolved in 100mL of deionized water, stirred until completely dissolved, the solution was transferred to a three-necked flask, nitrogen was introduced, the air was exhausted, and the mixture was vigorously stirred in a 70°C water bath, 25mL of ammonia water was quickly added, and the stirring reaction was continued for 1h. After the reaction was completed, the black Fe3O4 nanoparticles were separated by a magnet, washed repeatedly with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 60°C for 12h; Dissolve 2g of chitosan in 100mL of a 2% by mass dilute acetic acid solution, stir until completely dissolved, add 1g of the Fe3O4 nanoparticles prepared above, stir evenly, slowly drop 5mL of a 2.5% by mass glutaraldehyde solution, and perform cross-linking reaction at room temperature for 4h. After the reaction is completed, wash the product with deionized water and anhydrous ethanol, and dry it in a vacuum drying oven at 60°C for 12h to obtain a magnetic composite adsorbent; Step 3: Preparation of functionalized magnetic composite adsorbent: The prepared magnetic composite adsorbent is dispersed in an ethanol solution containing thioglycolic acid, and stirred to react to obtain a functionalized magnetic composite adsorbent; specifically, 1 g of the magnetic composite adsorbent is dispersed in 100 mL of an ethanol solution containing 0.1 mol / L thioglycolic acid, and stirred to react in a water bath at 50° C. for 6 hours. After the reaction is completed, the mixture is washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60° C. for 12 hours, so that the thioglycolic acid is loaded on the surface of the magnetic composite adsorbent by chemical bonding to obtain a functionalized magnetic composite adsorbent; Step 4: Heavy metal adsorption: The functionalized magnetic composite adsorbent was added to the water containing heavy metal ions, and the adsorption reaction was carried out on a constant temperature oscillator; specifically, 100 mL of wastewater was taken into a 250 mL conical flask, the pH value was adjusted to 6, 0.5 g / L of the functionalized magnetic composite adsorbent was added, and the reaction was carried out on a constant temperature oscillator at 25°C and a speed of 150 r / min for 60 minutes; Step 5: Heavy metal separation: After the adsorption reaction is completed, the adsorption system is separated by using an external magnetic field, so that the functionalized magnetic composite adsorbent loaded with heavy metal ions is quickly separated from the water body; specifically, the conical flask is placed on a magnet, so that the functionalized magnetic composite adsorbent is quickly separated from the water body, and the supernatant is taken, and the concentration of heavy metal ions therein is determined by an atomic absorption spectrometer to calculate the removal rate; Step 6: Desorption and recovery: The separated adsorbent is added to the desorption liquid, and the desorption reaction is carried out by stirring at a certain temperature to desorb and recover the heavy metal ions from the surface of the adsorbent; specifically, the separated adsorbent is added to 100mL of 0.1mol / L dilute hydrochloric acid solution, and the reaction is stirred in a water bath at 50°C for 2h. After the desorption is completed, the adsorbent is separated by a magnet; the desorption liquid is taken, and the heavy metal ions therein are recovered by a chemical precipitation method; the desorbed adsorbent is washed and dried, and the adsorption experiment is repeated to examine its reusability. Embodiment 2:

[0016] like Figure 1 As shown, an embodiment of the present invention provides a method for removing heavy metals from water, comprising the following steps: Step 1: Preliminary removal of heavy metals: The wastewater is pumped into the regulating tank, and the pH value is adjusted to 3 by a pH adjuster, wherein citric acid is selected as the pH adjuster; and a composite flocculant is added, which is a composite of polyacrylamide and nano-silicon dioxide to form large particle flocs, and preliminarily remove suspended matter and some heavy metals; Step 2: Preparation of magnetic composite adsorbent: The Fe3O4 nanoparticles were compounded with chitosan to prepare a magnetic composite adsorbent; specifically, 2.16g of FeSO4 and 5.4g of FeCl3 were dissolved in 100mL of deionized water, stirred until completely dissolved, the solution was transferred to a three-necked flask, nitrogen was introduced, the air was exhausted, and the mixture was vigorously stirred in a water bath at 80°C, 30mL of ammonia water was quickly added, and the stirring reaction was continued for 1.5h. After the reaction was completed, the black Fe3O4 nanoparticles were separated by a magnet, washed repeatedly with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 70°C for 15h; 3 g of chitosan was dissolved in 100 mL of a 2% dilute acetic acid solution, stirred until completely dissolved, 2 g of the Fe3O4 nanoparticles prepared above were added, stirred evenly, 5 mL of a 2.5% glutaraldehyde solution was slowly added dropwise, and the cross-linking reaction was carried out at room temperature for 4 h. After the reaction was completed, the product was washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 h to obtain a magnetic composite adsorbent; Step 3: Preparation of functionalized magnetic composite adsorbent: The prepared magnetic composite adsorbent is dispersed in an ethanol solution containing thioglycolic acid, and stirred to react to obtain a functionalized magnetic composite adsorbent; specifically, 1 g of the magnetic composite adsorbent is dispersed in 100 mL of an ethanol solution containing 0.1 mol / L thioglycolic acid, and stirred to react in a water bath at 55° C. for 7 hours. After the reaction is completed, the mixture is washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 65° C. for 12 hours, so that the thioglycolic acid is loaded on the surface of the magnetic composite adsorbent by chemical bonding to obtain a functionalized magnetic composite adsorbent; Step 4: Heavy metal adsorption: The functionalized magnetic composite adsorbent was added to the water containing heavy metal ions, and the adsorption reaction was carried out on a constant temperature oscillator; specifically, 100 mL of wastewater was taken into a 250 mL conical flask, the pH value was adjusted to 7, 1 g / L of the functionalized magnetic composite adsorbent was added, and the reaction was carried out on a constant temperature oscillator at 30°C and a speed of 150 r / min for 90 minutes; Step 5: Heavy metal separation: After the adsorption reaction is completed, the adsorption system is separated by using an external magnetic field, so that the functionalized magnetic composite adsorbent loaded with heavy metal ions is quickly separated from the water body; specifically, the conical flask is placed on a magnet, so that the functionalized magnetic composite adsorbent is quickly separated from the water body, and the supernatant is taken, and the concentration of heavy metal ions therein is determined by an atomic absorption spectrometer to calculate the removal rate; Step 6: Desorption and recovery: The separated adsorbent is added to the desorption liquid, and the desorption reaction is carried out by stirring at a certain temperature to desorb and recover the heavy metal ions from the surface of the adsorbent; specifically, the separated adsorbent is added to 100mL of 0.1mol / L dilute hydrochloric acid solution, and the reaction is stirred in a water bath at 55°C for 2.5h. After the desorption is completed, the adsorbent is separated by a magnet; the desorption liquid is taken, and the heavy metal ions therein are recovered by a chemical precipitation method; the desorbed adsorbent is washed and dried, and the adsorption experiment is repeated to examine its reusability. Embodiment three:

[0017] like Figure 1 As shown, an embodiment of the present invention provides a method for removing heavy metals from water, comprising the following steps: Step 1: Preliminary removal of heavy metals: The wastewater is pumped into the regulating tank, and the pH value is adjusted to 4 by a pH adjuster, wherein sulfuric acid is selected as the pH adjuster; and a composite flocculant is added, which is a composite of polyacrylamide and nano-silicon dioxide to form large particle flocs, and preliminarily remove suspended matter and some heavy metals; Step 2: Preparation of magnetic composite adsorbent: The Fe3O4 nanoparticles were compounded with chitosan to prepare a magnetic composite adsorbent; specifically, 3.24g of FeSO4 and 8.1g of FeCl3 were dissolved in 100mL of deionized water, stirred until completely dissolved, the solution was transferred to a three-necked flask, nitrogen was introduced, the air was exhausted, and the mixture was vigorously stirred in a water bath at 85°C, 35mL of ammonia water was quickly added, and the stirring reaction was continued for 2h. After the reaction was completed, the black Fe3O4 nanoparticles were separated by a magnet, washed repeatedly with deionized water and anhydrous ethanol, and then dried in a vacuum drying oven at 75°C for 18h; Dissolve 4 g of chitosan in 100 mL of a 2% by mass dilute acetic acid solution, stir until completely dissolved, add 3 g of the Fe3O4 nanoparticles prepared above, stir evenly, slowly drop 5 mL of a 2.5% by mass glutaraldehyde solution, and perform cross-linking reaction at room temperature for 4 h. After the reaction is completed, wash the product with deionized water and anhydrous ethanol, and dry it in a vacuum drying oven at 60°C for 12 h to obtain a magnetic composite adsorbent; Step 3: Preparation of functionalized magnetic composite adsorbent: The prepared magnetic composite adsorbent is dispersed in an ethanol solution containing thioglycolic acid, and stirred to react to obtain a functionalized magnetic composite adsorbent; specifically, 1 g of the magnetic composite adsorbent is dispersed in 100 mL of an ethanol solution containing 0.1 mol / L thioglycolic acid, and stirred to react in a water bath at 60° C. for 8 h. After the reaction is completed, the mixture is washed with deionized water and anhydrous ethanol, and dried in a vacuum drying oven at 70° C. for 12 h, so that the thioglycolic acid is loaded on the surface of the magnetic composite adsorbent by chemical bonding to obtain a functionalized magnetic composite adsorbent; Step 4: Heavy metal adsorption: The functionalized magnetic composite adsorbent was added to the water containing heavy metal ions, and the adsorption reaction was carried out on a constant temperature oscillator; specifically, 100 mL of wastewater was taken into a 250 mL conical flask, the pH value was adjusted to 8, 1.5 g / L of the functionalized magnetic composite adsorbent was added, and the reaction was carried out on a constant temperature oscillator at 35°C and a speed of 150 r / min for 120 min; Step 5: Heavy metal separation: After the adsorption reaction is completed, the adsorption system is separated by using an external magnetic field, so that the functionalized magnetic composite adsorbent loaded with heavy metal ions is quickly separated from the water body; specifically, the conical flask is placed on a magnet, so that the functionalized magnetic composite adsorbent is quickly separated from the water body, and the supernatant is taken, and the concentration of heavy metal ions therein is determined by an atomic absorption spectrometer to calculate the removal rate; Step 6: Desorption and recovery: The separated adsorbent is added to the desorption liquid, and the desorption reaction is carried out by stirring at a certain temperature to desorb and recover the heavy metal ions from the surface of the adsorbent; specifically, the separated adsorbent is added to 100mL of 0.1mol / L ethylenediaminetetraacetic acid solution, and the reaction is stirred in a water bath at 60°C for 3h. After the desorption is completed, the adsorbent is separated by a magnet; the desorption liquid is taken, and the heavy metal ions therein are recovered by a chemical precipitation method; the desorbed adsorbent is washed and dried, and the adsorption experiment is repeated to examine its reusability.

[0018] Comparative Example: Heavy metals are removed from water by chemical precipitation methods known in the art.

[0019] Experimental example: The performance test of the heavy metal removal results of the water bodies in Example 1, Example 2, Example 3 and the comparative example is shown in the following table: .

[0020] In summary, the method for removing heavy metals from water bodies of the present invention not only achieves efficient heavy metal removal, but also significantly improves the convenience and environmental friendliness of the treatment process. Compared with the traditional chemical precipitation method, the comprehensive removal rate of the present invention is significantly improved, reaching more than 95%. At the same time, the adsorbent has good reusability. After multiple uses, the removal rate can still be maintained at more than 90%, which greatly reduces the treatment cost and improves the efficiency of resource utilization.

[0021] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for removing heavy metals from water, characterized in that: The following steps are involved: Step 1: Preliminary removal of heavy metals: The wastewater is pumped into the regulating tank and the pH value is adjusted to 2-4. Composite flocculants are added to form large particle flocs to preliminarily remove suspended solids and some heavy metals. Step 2: Preparation of magnetic composite adsorbent: The Fe3O4 nanoparticles were compounded with chitosan to prepare a magnetic composite adsorbent; Step 3: Preparation of functionalized magnetic composite adsorbent: The prepared magnetic composite adsorbent is dispersed in an ethanol solution containing thioglycolic acid, and stirred for reaction to obtain a functionalized magnetic composite adsorbent; Step 4: Heavy metal adsorption: The functionalized magnetic composite adsorbent is added into water containing heavy metal ions, and the adsorption reaction is carried out on a constant temperature oscillator; Step 5: Heavy metal separation: After the adsorption reaction is completed, the adsorption system is separated by using an external magnetic field, so that the functionalized magnetic composite adsorbent loaded with heavy metal ions is quickly separated from the water body; Step 6: Desorption and recovery: The separated adsorbent is added to the desorption liquid and stirred at a certain temperature to carry out a desorption reaction, so that the heavy metal ions are desorbed and recovered from the surface of the adsorbent.

2. The method for removing heavy metals from water bodies according to claim 1, characterized in that: In step 1, the pH value is adjusted to 2-4 by a pH regulator, wherein the pH regulator is citric acid or sulfuric acid; and the composite flocculant is composed of polyacrylamide and nano-silicon dioxide.

3. The method for removing heavy metals from water according to claim 1, characterized in that: In step 2, first, Fe3O4 nanoparticles are prepared by coprecipitation method, FeSO4 and FeCl3 are dissolved in deionized water at a molar ratio of 1:2, and under nitrogen protection, ammonia water is quickly added and stirred to react to obtain a black Fe3O4 nanoparticle suspension; then, a certain amount of chitosan is dissolved in a dilute acetic acid solution, the above Fe3O4 nanoparticle suspension is added, stirred evenly, glutaraldehyde is added dropwise for cross-linking reaction, and after washing and drying, a magnetic composite adsorbent is obtained.

4. The method for removing heavy metals from water according to claim 1, characterized in that: In step three, the stirring reaction conditions are: stirring the reaction in a water bath at 50-60°C for 6-8 hours. After the reaction is completed, washing with deionized water and anhydrous ethanol, and drying in a vacuum drying oven at 60-70°C for 12 hours, so that the thioglycolic acid is loaded onto the surface of the magnetic composite adsorbent by chemical bonding to obtain a functionalized magnetic composite adsorbent.

5. The method for removing heavy metals from water bodies according to claim 1, characterized in that: In step 4, the conditions of the adsorption reaction are: the pH value of the water body is 6-8, the adsorbent dosage is 0.5-1.5 g / L, the reaction time is 60-120 min, and the temperature is 25-35°C.

6. The method for removing heavy metals from water body according to claim 1, characterized in that: In step six, the conditions of the desorption reaction are: the desorption liquid is selected from dilute hydrochloric acid or ethylenediaminetetraacetic acid solution, and the reaction is stirred in a water bath at 50-60°C for 2-3 hours. After the desorption is completed, the adsorbent is separated by a magnet; the desorption liquid is taken and the heavy metal ions therein are recovered by chemical precipitation.

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