Preparation method and application of heavy metal adsorbent

Abstract

The invention relates to the field of petrifaction, and discloses a preparation method and application of a heavy metal adsorbent. The preparation method comprises the following steps: 1) mixing a thiolated alumina microsphere dispersion liquid with AlOOH sol; mixing the obtained compound with urea and water, and performing heating reaction to obtain an aluminum oxide microsphere compound; 2) mixing the alumina microsphere compound, charcoal, Span-80, lauryl sodium sulfate and sodium bicarbonate in a sodium alginate solution, dripping the obtained mixed solution into a calcium chloride solution containing copper ions and zinc ions, reacting, and cross-linking through glutaraldehyde to obtain a calcium alginate coated composite material; and 3) mixing water, alum and ethanol, adding the calcium alginate coated composite material, fly ash coal, charcoal, clay and zeolite, and granulating to obtain the heavy metal adsorbent. Through compounding of the charcoal, fly ash, clay, zeolite, the calcium alginate coated composite material and the like, the prepared heavy metal adsorbent can efficiently remove various heavy metals in naphtha.

Description

Technical Field

[0001] This invention relates to the petrochemical field, and more particularly to a method for preparing a heavy metal adsorbent and its application. Background Technology

[0002] Naphtha contains heavy metals such as Ni, V, Pb, and As. Although their content is only tens to hundreds of ppb, it is enough to cause an exponential increase in the coking rate of furnace tubes during downstream high-temperature cracking and reforming processes. Exceeding the heavy metal limit by 50 ppb will shorten the operating cycle of ethylene cracking furnaces, causing industrial losses.

[0003] Existing demetallization technologies, such as acid washing and alkali washing, generate a large amount of waste, with As entering the aqueous phase in the form of arsenate, resulting in high subsequent treatment costs. Traditional molecular sieves have poor selectivity and uniform pore size, which limits the diffusion of Ni and V-type macromolecules (e.g., CN110562997A).

[0004] In summary, there is an urgent need to develop an adsorbent that can efficiently remove heavy metals from naphtha. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for preparing a heavy metal adsorbent and its application. The heavy metal adsorbent of this invention comprises a composite material of biochar, fly ash, clay, zeolite, and calcium alginate, exhibiting excellent adsorption capacity for heavy metal ions such as Ni, V, Pb, and As in naphtha.

[0006] The specific technical solution of the present invention includes: In a first aspect, the present invention provides a method for preparing a heavy metal adsorbent, comprising the following steps, by weight: 1) Mix 0.2-0.3 g / 20 mL of a 2-3 wt% mercaptolated alumina microsphere dispersion with AlOOH sol; mix the resulting complex with urea and water, and heat to react, to obtain the alumina microsphere complex.

[0007] In step 1), the surface of the thiolized alumina microspheres has a large number of thiol groups, which not only allows for electrostatic adsorption with AlOOH sol, but also facilitates the adsorption of heavy metal elements such as Ni, V, Pb, and As from naphtha. Simultaneously, the adsorption of AlOOH sol on the surface of the alumina microspheres enriches the pores on the surface, giving them a greater heavy metal adsorption capacity.

[0008] 2) Mix 2 parts of alumina microsphere composite, 0.5-1.5 parts of biochar, emulsifier (preferably Span-80), dispersant (preferably sodium dodecyl sulfate) and pH adjuster (preferably sodium bicarbonate) in 10-100 parts of sodium alginate solution. Slowly add the resulting mixture dropwise into a calcium chloride solution containing copper and zinc ions, stir and react. Add the reaction product to a glutaraldehyde solution and stir and react. Filter and dry to obtain calcium alginate coated composite material.

[0009] In step 2), this invention uses sodium alginate as a binder to combine the alumina microsphere composite with biochar, which improves the dispersibility of the alumina microsphere composite in the matrix. Through calcium ion crosslinking, a calcium alginate-coated composite material with stable structure and excellent adsorption performance can be formed. Furthermore, copper and zinc ions can enter the gel network through ion exchange, providing secondary coordination for metal ions and improving the adsorption capacity of the adsorbent.

[0010] 3) Mix 12-15 parts water, 3-5 parts alum and 2-3 parts ethanol, add 12-16 parts calcium alginate coated composite material, 12-14 parts fly ash, 20-25 parts biochar, 5-7 parts clay and 7-9 parts zeolite, mix evenly, granulate to obtain heavy metal adsorbent.

[0011] In step 3), the present invention granulates a composite material containing biochar, fly ash, clay, zeolite, and calcium alginate, and the resulting heavy metal adsorbent can efficiently remove heavy metals from naphtha.

[0012] Preferably, in step 1), the preparation method of the alumina microsphere composite by weight includes: taking 0.2-0.3 g / 20 mL of thiolized alumina microsphere dispersion and AlOOH sol, mixing and stirring for 10-12 h, centrifuging, washing, and drying to obtain the composite; stirring 0.3 parts of the composite with 0.25-0.35 parts of urea and 60-80 parts of water evenly, reacting at 90-110℃ for 46-50 h, cooling, centrifuging, washing, and freeze-drying to obtain the alumina microsphere composite.

[0013] Preferably, in step 1), the preparation method of the thiolized alumina microsphere dispersion, by weight, includes: Take 2 parts of aluminum sulfate octahydrate, 0.05-0.15 parts of urea, 0.2-0.4 parts of hexadecyltrimethylammonium bromide, and 40-60 parts of water, stir evenly, treat at 180-185℃ for 22-26 hours, wash until neutral, filter, dry, calcine at 500-600℃ for 3-4 hours, grind, and obtain alumina microspheres.

[0014] Take 14-16 parts of 3-mercaptopropyltriethoxysilane and 80-120 parts of ethanol aqueous solution, stir evenly, add 2 parts of alumina microspheres, heat to 50-55℃, stir for 2-3 hours to obtain a mercaptolated alumina microsphere dispersion.

[0015] This invention uses aluminum sulfate octadecylhydrate, hexadecyltrimethylammonium bromide, and urea to prepare alumina microspheres with a large specific surface area. These microspheres are then modified with thiol to provide conditions for subsequent electrostatic adsorption of AlOOH sol, while also facilitating the adsorption of heavy metals from naphtha.

[0016] Preferably, in step 1), the preparation method of the AlOOH sol by weight includes: mixing 18 parts of aluminum isopropoxide with 80-120 parts of water, heating to 80-85℃, stirring for 40-50 min, adding nitric acid to adjust the pH to 3-4, stirring for 3-4 h, drying, and grinding; mixing the obtained powder with water, heating to 80-85℃, stirring for 40-50 min, adding nitric acid, and refluxing at a constant temperature for 6-7 h to obtain AlOOH sol.

[0017] Preferably, in step 2), the concentration of the sodium alginate solution is 3-3.5 wt%; the concentration of calcium chloride in the calcium chloride solution is 2.5-3 wt%, the concentration of copper salt is 0.5-1.5 wt%, and the concentration of zinc salt is 0.25-0.75 wt%.

[0018] Preferably, in step 2), the volume ratio of the mixture to the calcium chloride solution is 60-100:200.

[0019] Preferably, in step 2), the concentration of the glutaraldehyde solution is 0.3-0.7 wt% and the pH is 7.2-7.6.

[0020] Preferably, in step 2), the stirring reaction time for the first stirring reaction is 2-4 hours, and the stirring reaction time for the second stirring reaction is 1-2 hours.

[0021] Secondly, the present invention provides the application of the heavy metal adsorbent obtained by the above preparation method in the removal of heavy metals from naphtha.

[0022] Preferably, the heavy metal includes one or more of Ni, V, Pb and As.

[0023] The heavy metal adsorbent of the present invention has good adsorption capacity for heavy metals, especially Ni, V, Pb and As.

[0024] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention first prepares alumina microspheres with high specific surface area, and then modifies them with thiol, which can provide conditions for the electrostatic adsorption of AlOOH sol in the subsequent process, and at the same time facilitates the adsorption of heavy metals in naphtha. After AlOOH sol is adsorbed on the surface of alumina microspheres, it can enrich the pores of alumina microspheres, thereby having better adsorption capacity and adsorption capacity.

[0025] (2) In this invention, the alumina microsphere complex and biochar are combined by the cross-linking reaction of sodium alginate and calcium chloride, which can improve the dispersibility of alumina in the matrix. Through calcium ion cross-linking, it is prepared into an adsorbent with stable structure and excellent adsorption performance. When copper salt and zinc salt are added to the calcium chloride solution, copper ions and zinc ions enter the gel network through ion exchange and provide secondary coordination for metal ions, thereby improving the adsorption capacity of the adsorbent.

[0026] (3) The heavy metal adsorbent of the present invention is composed of biochar, fly ash, clay, zeolite and calcium alginate coated composite material, which has excellent adsorption capacity for heavy metal ions such as Ni, V, Pb and As in naphtha. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments.

[0028] General Implementation Examples In a first aspect, the present invention provides a method for preparing a heavy metal adsorbent, comprising the following steps, by weight: 1) Mix 0.2-0.3 g / 20 mL of a 2-3 wt% mercaptolated alumina microsphere dispersion with AlOOH sol; mix the resulting complex with urea and water, and heat to react, to obtain the alumina microsphere complex.

[0029] In some preferred embodiments, in step 1), the preparation method of the thiolized alumina microsphere dispersion, by weight, includes: Take 2 parts aluminum sulfate octadechydrate, 0.05-0.15 parts urea, 0.2-0.4 parts hexadecyltrimethylammonium bromide, and 40-60 parts water, stir evenly, treat at 180-185℃ for 22-26 hours, wash until neutral, filter, dry, calcine at 500-600℃ for 3-4 hours, grind, and obtain alumina microspheres; Take 14-16 parts of 3-mercaptopropyltriethoxysilane and 80-120 parts of ethanol aqueous solution, stir evenly, add 2 parts of alumina microspheres, heat to 50-55℃, stir for 2-3 hours to obtain a mercaptolated alumina microsphere dispersion.

[0030] In some preferred embodiments, in step 1), the preparation method of the AlOOH sol by weight includes: mixing 18 parts of aluminum isopropoxide with 80-120 parts of water, heating to 80-85°C, stirring for 40-50 min, adding nitric acid to adjust the pH to 3-4, stirring for 3-4 h, drying, and grinding; mixing the obtained powder with water, heating to 80-85°C, stirring for 40-50 min, adding nitric acid, and refluxing at a constant temperature for 6-7 h to obtain the AlOOH sol.

[0031] In some preferred embodiments, in step 1), the preparation method of the alumina microsphere composite by weight includes: taking 0.2-0.3 g / 20 mL of thiolized alumina microsphere dispersion and AlOOH sol, mixing and stirring for 10-12 h, centrifuging, washing, and drying to obtain the composite; stirring 0.3 parts of the composite with 0.25-0.35 parts of urea and 60-80 parts of water evenly, reacting at 90-110℃ for 46-50 h, cooling, centrifuging, washing, and freeze-drying to obtain the alumina microsphere composite.

[0032] 2) Mix 2 parts of alumina microsphere composite, 0.5-1.5 parts of biochar, emulsifier (preferably Span-80), dispersant (preferably sodium dodecyl sulfate), and pH adjuster (preferably sodium bicarbonate) in 10-100 parts of sodium alginate solution. Slowly add the resulting mixture dropwise to a calcium chloride solution containing copper and zinc ions, and stir to react. Add the reaction product to a glutaraldehyde solution and stir to react. Filter and dry to obtain a calcium alginate-coated composite material. In some preferred embodiments, in step 2), the concentration of the sodium alginate solution is 3-3.5 wt%; the concentration of calcium chloride in the calcium chloride solution is 2.5-3 wt%, the concentration of copper salt is 0.5-1.5 wt%, and the concentration of zinc salt is 0.25-0.75 wt%.

[0033] In some preferred embodiments, in step 2), the volume ratio of the mixture to the calcium chloride solution is 60-100:200.

[0034] In some preferred embodiments, in step 2), the concentration of the glutaraldehyde solution is 0.3-0.7 wt% and the pH is 7.2-7.6.

[0035] In some preferred embodiments, in step 2), the stirring reaction time for the first stirring reaction is 2-4 hours; and the stirring reaction time for the second stirring reaction is 1-2 hours.

[0036] 3) Mix 12-15 parts water, 3-5 parts alum and 2-3 parts ethanol, add 12-16 parts calcium alginate coated composite material, 12-14 parts fly ash, 20-25 parts biochar, 5-7 parts clay and 7-9 parts zeolite, mix evenly, granulate to obtain heavy metal adsorbent.

[0037] Secondly, the heavy metal adsorbent obtained by the above preparation method is used in the removal of heavy metals from naphtha.

[0038] In some preferred embodiments, the heavy metal includes one or more of Ni, V, Pb and As.

[0039] Specific embodiments and comparative examples The sources and types of substances involved in this application are not particularly limited, and exemplary ones include: fly ash: particle size: 10-30µm; biochar: particle size: 50-100µm; clay: particle size: 2-10µm; zeolite: particle size: 1-10µm.

[0040] Example 1 Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 181℃ for 24h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3.5h, grind, and obtain alumina microspheres. S2: Preparation of mercapto-modified alumina microsphere dispersion: Take 15g of 3-mercaptopropyltriethoxysilane and 100mL of anhydrous ethanol and water mixture with a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 52℃, stir for 2.5h to obtain a mercaptolated alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 82℃, stir for 45min, add nitric acid, adjust the pH to 3.5, stir for 3.5h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 82℃, stir for 45min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 6.5h to obtain AlOOH sol; S4: Take 0.25g of mercapto-modified alumina microsphere dispersion and 30mL of AlOOH sol, stir for 11h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 48h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex; Step 2: Preparation of calcium alginate-coated composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution containing 2g of copper nitrate and 1g of zinc nitrate, stir for 2.5h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 1.5h, filter and dry to obtain calcium alginate coated composite material; Step 3: Preparation of heavy metal adsorbent: By weight, take 13 parts deionized water, 4 parts alum, and 2.5 parts ethanol, mix them evenly, add 14 parts calcium alginate-coated composite material, 13 parts fly ash, 22 parts biochar, 6 parts clay, and 8 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0041] Example 2 Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octadecate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 180℃ for 22h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3h, grind, and obtain alumina microspheres. S2: Preparation of mercapto-modified alumina microsphere dispersion: Take 15g of 3-mercaptopropyltriethoxysilane, 100mL of anhydrous ethanol and water in a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 50℃, stir for 2h to obtain a mercaptolated alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 80℃, stir for 40min, add nitric acid, adjust the pH to 3, stir for 3h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 80℃, stir for 40min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 6h to obtain AlOOH sol; S4: Take 0.25g of mercapto-modified alumina microsphere dispersion and 30mL of AlOOH sol, stir for 10h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 46h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex; Step 2: Preparation of calcium alginate-coated composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution containing 2g of copper nitrate and 1g of zinc nitrate, stir for 2h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 1h, filter and dry to obtain calcium alginate coated composite material; Step 3: Preparation of heavy metal adsorbent: By weight, take 12 parts deionized water, 3 parts alum, and 2 parts ethanol, mix them evenly, add 12 parts calcium alginate-coated composite material, 12 parts fly ash, 20 parts biochar, 5 parts clay, and 7 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0042] Example 3 Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir evenly, treat at 182℃ for 26h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 4h, grind, and obtain alumina microspheres. S2: Preparation of mercapto-modified alumina microsphere dispersion: Take 15g of 3-mercaptopropyltriethoxysilane, 100mL of anhydrous ethanol and water in a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 55℃, stir for 3h to obtain a mercaptolated alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 85℃, stir for 50min, add nitric acid, adjust the pH to 4, stir for 4h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 85℃, stir for 50min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 7h to obtain AlOOH sol; S4: Take 0.25g of mercapto-modified alumina microsphere dispersion and 30mL of AlOOH sol, stir for 12h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 50h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex; Step 2: Preparation of calcium alginate-coated composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution containing 2g of copper nitrate and 1g of zinc nitrate, stir for 3h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 2h, filter and dry to obtain calcium alginate coated composite material; Step 3: Preparation of heavy metal adsorbent: Take 15 parts by weight of deionized water, 5 parts of alum, and 3 parts of ethanol, mix them evenly, add 16 parts of calcium alginate-coated composite material, 14 parts of fly ash, 25 parts of biochar, 7 parts of clay, and 9 parts of zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0043] Comparative Example 1: No mercaptolation treatment was performed on the alumina microspheres; all other aspects were the same as in Example 1. Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 181℃ for 24h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3.5h, grind, and obtain alumina microspheres. S2: Preparation of alumina microsphere dispersion: Take 100 mL of anhydrous ethanol and water mixture with a volume ratio of 95:5, add 2 g of alumina microspheres, heat to 52 °C, and stir for 2.5 h to obtain an alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 82℃, stir for 45min, add nitric acid, adjust the pH to 3.5, stir for 3.5h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 82℃, stir for 45min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 6.5h to obtain AlOOH sol; S4: Take 0.25g of alumina microsphere dispersion and 30mL of AlOOH sol, stir for 11h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 48h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex. Step 2: Preparation of calcium alginate-coated composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution containing 2g of copper nitrate and 1g of zinc nitrate, stir for 2.5h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 1.5h, filter and dry to obtain calcium alginate coated composite material; Step 3: Preparation of heavy metal adsorbent: By weight, take 13 parts deionized water, 4 parts alum, and 2.5 parts ethanol, mix them evenly, add 14 parts calcium alginate-coated composite material, 13 parts fly ash, 22 parts biochar, 6 parts clay, and 8 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0044] Comparative Example 2: No AlOOH sol was added; all other aspects were the same as in Example 1. Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 181℃ for 24h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3.5h, grind, and obtain alumina microspheres. S2: Preparation of thiolated alumina microspheres: Take 15g of 3-mercaptopropyltriethoxysilane and 100mL of anhydrous ethanol and water mixture with a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 52℃, stir for 2.5h, centrifuge, wash and dry to obtain mercapto-modified alumina microspheres. Step 2: Preparation of calcium alginate-coated composite material: Take 2g of mercapto-modified alumina microspheres and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution containing 2g of copper nitrate and 1g of zinc nitrate, stir for 2.5h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 1.5h, filter and dry to obtain calcium alginate-coated composite material; Step 3: Preparation of heavy metal adsorbent: By weight, take 13 parts deionized water, 4 parts alum, and 2.5 parts ethanol, mix them evenly, add 14 parts calcium alginate-coated composite material, 13 parts fly ash, 22 parts biochar, 6 parts clay, and 8 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0045] Comparative Example 3: No sodium alginate coating, otherwise the same as Example 1: Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 181℃ for 24h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3.5h, grind, and obtain alumina microspheres. S2: Preparation of mercapto-modified alumina microsphere dispersion: Take 15g of 3-mercaptopropyltriethoxysilane and 100mL of anhydrous ethanol and water mixture with a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 52℃, stir for 2.5h to obtain a mercaptolated alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 82℃, stir for 45min, add nitric acid, adjust the pH to 3.5, stir for 3.5h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 82℃, stir for 45min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 6.5h to obtain AlOOH sol; S4: Take 0.25g of mercapto-modified alumina microsphere dispersion and 30mL of AlOOH sol, stir for 11h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 48h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex; Step 2: Preparation of alumina-biochar composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL containing 2g of copper nitrate and 1g of zinc nitrate, stir for 1.5h, filter and dry to obtain alumina-biochar composite material.

[0046] Step 3: Preparation of heavy metal adsorbent: By weight, take 13 parts deionized water, 4 parts alum, and 2.5 parts ethanol, mix them evenly, add 14 parts alumina-biochar composite material, 13 parts fly ash, 22 parts biochar, 6 parts clay, and 8 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0047] Comparative Example 4: No modification with copper nitrate or zinc nitrate was added; all other aspects were the same as in Example 1. Step 1: Preparation of alumina microsphere composite: S1: Preparation of alumina microspheres: Take 2g of aluminum sulfate octahydrate, 1g of urea, 0.3g of hexadecyltrimethylammonium bromide, and 50mL of deionized water, stir well, treat at 181℃ for 24h, wash until the pH of the solution is neutral, filter, dry, calcine at 550℃ for 3.5h, grind, and obtain alumina microspheres. S2: Preparation of mercapto-modified alumina microsphere dispersion: Take 15g of 3-mercaptopropyltriethoxysilane and 100mL of anhydrous ethanol and water mixture with a volume ratio of 95:5, stir evenly, add 2g of alumina microspheres, heat to 52℃, stir for 2.5h to obtain a mercaptolated alumina microsphere dispersion. Preparation of S3: AlOOH sol: Take 18g of aluminum isopropoxide and 100mL of deionized water, heat to 82℃, stir for 45min, add nitric acid, adjust the pH to 3.5, stir for 3.5h, dry and grind to obtain powder; take 10g of powder and 20mL of deionized water, heat to 82℃, stir for 45min, add 10mL of 0.1mol / L nitric acid, reflux at constant temperature for 6.5h to obtain AlOOH sol; S4: Take 0.25g of mercapto-modified alumina microsphere dispersion and 30mL of AlOOH sol, stir for 11h, centrifuge, wash and dry to obtain complex A; take 0.3g of complex A, 0.2g of urea and 70mL of deionized water, stir evenly, react at 100℃ for 48h, cool, centrifuge, wash and freeze dry to obtain alumina microsphere complex; Step 2: Preparation of calcium alginate-coated composite material: Take 2g of alumina microsphere composite and 50mL of deionized water, stir well, add 30mL of 3wt% sodium alginate solution, stir well, add 1g of biochar, 0.05g of Span-80, 0.01g of sodium dodecyl sulfate and 0.4g of sodium bicarbonate, stir well to obtain a mixed solution, slowly add the mixed solution dropwise to 200mL of 3wt% calcium chloride solution, stir for 2.5h, add to 100mL of 0.5wt% glutaraldehyde solution with pH 7.4, stir for 1.5h, filter and dry to obtain calcium alginate coated composite material; Step 3: Preparation of heavy metal adsorbent: By weight, take 13 parts deionized water, 4 parts alum, and 2.5 parts ethanol, mix them evenly, add 14 parts alumina-biochar composite material, 13 parts fly ash, 22 parts biochar, 6 parts clay, and 8 parts zeolite, continue to mix evenly, granulate, and obtain heavy metal adsorbent.

[0048] Performance testing The removal performance of heavy metal adsorbents prepared in each example and comparative example on naphtha was tested. The adsorption temperature was 25℃, the adsorption time was 2h, and the agent-to-oil ratio was 1:200g / mL. The concentrations of Ni, V, Pb, and As in the naphtha before removal were 0.2μg / kg, 0.15μg / kg, 0.15μg / kg, and 0.1μg / kg, respectively. The adsorption rates of several representative heavy metals are shown in Table 1 below. Table 1 Ni V Pb As Example 1 99.9% 99.9% 99.3% 99.6% Example 2 99.9% 99.9% 99.2% 99.5% Example 3 99.9% 99.9% 99.4% 99.6% Comparative Example 1 99.7% 99.7% 98.7% 99.1% Comparative Example 2 99.6% 99.5% 98.4% 98.7% Comparative Example 3 99.7% 99.6% 98.9% 99.2% Comparative Example 4 99.6% 99.5% 98.5% 98.9% The data comparison in Table 1 shows that: (1) The heavy metal adsorbents prepared in Examples 1-3 have a very high removal capacity for heavy metals Ni, V, Pb and As in naphtha that enhance the adsorbent.

[0049] (2) In Comparative Example 1, the lack of thiolization treatment on the alumina microspheres resulted in a decrease in the adsorption capacity of the adsorbent for heavy metals (especially a greater decrease in the removal of Pb and As). In Comparative Example 2, the absence of AlOOH sol reduced the specific surface area of ​​the alumina microspheres, also leading to a decrease in the heavy metal adsorption capacity of the adsorbent, even worse than in Comparative Example 1. In Comparative Example 3, the lack of sodium alginate coating resulted in poor dispersibility of the alumina, which to some extent affected the adsorption capacity of the heavy metal adsorbent. In Comparative Example 4, the absence of copper nitrate and zinc nitrate modification also led to a decrease in the adsorption capacity of the heavy metal adsorbent for heavy metals.

[0050] Unless otherwise specified, the raw materials and equipment used in this invention are all commonly used in the field; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, alterations, and equivalent transformations made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a heavy metal adsorbent, characterized by: By weight, it includes: 1) Mix 2-3 wt% of mercaptolated alumina microsphere dispersion with AlOOH sol at a ratio of 0.2-0.3 g / 20 mL; then mix with urea and water to react and obtain alumina microsphere complex; 2) Mix 2 parts of alumina microsphere composite, 0.5-1.5 parts of biochar, emulsifier, dispersant and pH adjuster in 10-100 parts of sodium alginate solution, drop the resulting mixture into calcium chloride solution containing copper salt and zinc salt, and add the reaction product to glutaraldehyde solution to react, to obtain calcium alginate coated composite material. 3) Mix 12-15 parts water, 3-5 parts alum, 2-3 parts ethanol, 12-16 parts calcium alginate-coated composite material, 12-14 parts fly ash, 20-25 parts biochar, 5-7 parts clay and 7-9 parts zeolite, granulate to obtain heavy metal adsorbent.

2. The preparation method according to claim 1, characterized in that: In step 1), the preparation method of the alumina microsphere composite by weight includes: taking 0.2-0.3 g / 20 mL of thiolized alumina microsphere dispersion and AlOOH sol, mixing and stirring for 10-12 h, centrifuging, washing, and drying to obtain the composite; stirring 0.3 parts of the composite with 0.25-0.35 parts of urea and 60-80 parts of water evenly, reacting at 90-110℃ for 46-50 h, cooling, centrifuging, washing, and freeze-drying to obtain the alumina microsphere composite.

3. The production method according to claim 1 or 2, characterized by: In step 1), the preparation method of the thiolized alumina microsphere dispersion, by weight, includes: Take 2 parts of aluminum sulfate octadechydrate, 0.05-0.15 parts of urea, 0.2-0.4 parts of hexadecyltrimethylammonium bromide, and 40-60 parts of water, stir evenly, treat at 180-185℃, wash until neutral, filter, dry, calcine, and grind to obtain alumina microspheres. Take 14-16 parts of 3-mercaptopropyltriethoxysilane and 80-120 parts of ethanol aqueous solution, stir evenly, add 2 parts of alumina microspheres, heat and stir to react, and obtain a mercapto-modified alumina microsphere dispersion.

4. The production method according to claim 1 or 2, characterized by: In step 1), the preparation method of the AlOOH sol by weight includes: mixing 18 parts of aluminum isopropoxide with 80-120 parts of water, stirring at 80-85℃, adjusting the pH to 3-4, stirring, drying, and grinding; mixing the obtained powder with water, stirring at 80-85℃, adding nitric acid, and refluxing at a constant temperature to obtain AlOOH sol.

5. The method of claim 1, wherein: In step 2), The concentration of the sodium alginate solution is 3-3.5 wt%. The calcium chloride solution contains 2.5-3 wt% calcium chloride, 0.5-1.5 wt% copper salt, and 0.25-0.75 wt% zinc salt.

6. The method of claim 5, wherein: In step 2), the volume ratio of the mixture to the calcium chloride solution is 60-100:

200.

7. The method of claim 1 or 5 or 6, wherein: In step 2), the concentration of the glutaraldehyde solution is 0.3-0.7 wt% and the pH is 7.2-7.

6.

8. The method of claim 1, wherein: In step 2), The reaction time for the first time is 2-4 hours; The reaction time for the second reaction is 1-2 hours.

9. The application of the heavy metal adsorbent obtained by the preparation method according to any one of claims 1-8 in the removal of heavy metals from naphtha.

10. Use according to claim 9, characterized in that: The heavy metal includes one or more of Ni, V, Pb, and As. The heavy metal includes one or more of Ni, V, Pb, and As.