Preparation method of a modified adsorbent and its application in metallurgical wastewater

Abstract

The present invention relates to the technical field of metallurgical wastewater treatment, and discloses a preparation method of a modified adsorbent and its application in metallurgical wastewater treatment. The present invention uses 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide as esterification catalysts, and a thiourea quaternary ammonium salt modifier and a carboxyl group of sodium alginate to carry out an esterification cross-linking reaction to obtain a sodium alginate-based modified adsorbent. A large number of thiourea groups and quaternary ammonium salt groups are introduced into the sodium alginate matrix, and the amino groups and sulfur atoms in the thiourea groups react with Cu 2+ , Pb 2+ 、Cd 2+ There is a strong complexation between them, which has strong chelating adsorption performance. The quaternary ammonium salt cation and Cr2O7 2‑ The positive and negative electrostatic interactions between anions give the modified adsorbent a high adsorption capacity for these metal ions, expanding the practical application of sodium alginate in the treatment of metallurgical and other wastewaters containing heavy metal ions.

Description

Technical Field

[0001] The invention relates to the technical field of metallurgical wastewater treatment, in particular to a preparation method of a modified adsorbent and application thereof in metallurgical wastewater. Background Art

[0002] In recent years, the metallurgical industry has developed rapidly, and more and more metallurgical wastewater has been generated. Metallurgical wastewater contains a large amount of heavy metal ions such as copper, lead, and chromium, which are highly toxic, difficult to degrade, and cause serious pollution. The current treatment method for these heavy metal ions is mainly adsorption, and the development of high-performance environmentally friendly adsorption materials is a research hotspot.

[0003] Sodium alginate is a natural polysaccharide polymer that is cheap and readily available. It contains a large number of carboxyl groups and has strong adsorption properties for metal ions. It has broad application prospects in wastewater treatment. Chinese patent CN116272890B discloses a method for preparing thiourea double-crosslinked sodium alginate / chitosan gel spheres and a method for removing Cr from aqueous solutions. 6+ The method uses sodium alginate, thiourea, chitosan, ferric chloride, glutaraldehyde and the like as raw materials to prepare gel balls that have a high removal rate for chromium ions in wastewater. However, the gel balls of this patent have a low adsorption capacity for chromium ions and do not show good adsorption performance for metal ions such as copper, lead and cadmium. Summary of the Invention

[0004] The invention solves the problem that sodium alginate has poor adsorption performance for pollutants such as metal ions.

[0005] The technical solution of the present invention: a method for preparing a modified adsorbent:

[0006] (1) Add p-phenylenediisocyanate and N,N-dimethylethylenediamine in a molar ratio of 1:(2-2.4) to ethanol. After the reaction, distill under reduced pressure. The product is washed with deionized water and petroleum ether, and then recrystallized from chloroform to obtain a thiourea precursor.

[0007] (2) Add thiourea precursor and bromohydrin at a molar ratio of 1:(2.6-3.4) to acetonitrile, distill under reduced pressure after the reaction, wash with petroleum ether, and recrystallize the product in ethanol to obtain a thiourea quaternary ammonium salt modifier. The preparation reaction formula is:

[0008] .

[0009] (3) Sodium alginate, thiourea quaternary ammonium salt modifier, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide are added to dimethyl sulfoxide in a mass ratio of 1: (0.3-1.5): (0.02-0.1): (0.12-0.6). After the reaction, the mixture is filtered, washed with deionized water and ethanol, and then soaked in deionized water, filtered, and dried to obtain a modified adsorbent. The preparation reaction formula is:

[0010] .

[0011] Preferably, the reaction in (1) is stirred at 20-25°C for 3-4 hours.

[0012] Preferably, the structural formula of the bromohydrin in (2) is Br(CH2) n OH, n is any integer from 2 to 6.

[0013] Preferably, the reaction in (2) is stirred at 80-85°C for 36-48 hours.

[0014] Preferably, the reaction in (3) is stirred at 20-30°C for 24-48 hours.

[0015] Preferably, the modified adsorbent is used in metallurgical wastewater treatment.

[0016] Beneficial technical effects: The present invention uses p-phenylenediisocyanate and N,N-dimethylethylenediamine to carry out addition reaction, and then carries out quaternization reaction with bromoalcohols such as 2-bromoethanol to obtain a thiourea quaternary ammonium salt modifier containing multiple quaternary ammonium salts and thiourea groups, and then uses 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide as esterification catalysts to carry out esterification cross-linking reaction with the carboxyl group of sodium alginate to obtain a sodium alginate-based modified adsorbent. A large number of thiourea groups and quaternary ammonium salt groups are introduced into the sodium alginate matrix, and the amino groups and sulfur atoms in the thiourea groups react with Cu 2+ , Pb 2+ 、Cd 2+ There is a strong complexation between them, which has strong chelating adsorption performance. The quaternary ammonium salt cation and Cr2O7 2- The positive and negative electrostatic interactions between anions give the modified adsorbent a high adsorption capacity for these metal ions, expanding the practical application of sodium alginate in the treatment of metallurgical and other wastewaters containing heavy metal ions. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention. Example 1

[0018] (1) Add 15 mmol of p-phenylenediisocyanate and 30 mmol of N,N-dimethylethylenediamine to 35 mL of ethanol, stir and react at 20 °C for 4 h, and distill under reduced pressure. The product is washed with deionized water and petroleum ether, and then recrystallized from chloroform to obtain a thiourea precursor.

[0019] (2) Add 10 mmol of thiourea precursor and 30 mmol of 2-bromoethanol to 30 mL of acetonitrile, heat to 85 °C, stir and reflux for 36 h, distill under reduced pressure, wash with petroleum ether, and recrystallize the product from ethanol to obtain a thiourea quaternary ammonium salt modifier.

[0020] (3) Add 30 g of sodium alginate, 9 g (about 14.56 mmol) of thiourea quaternary ammonium salt modifier, 0.6 g of 4-dimethylaminopyridine, and 3.6 g of N,N'-dicyclohexylcarbodiimide to 1.2 L of dimethyl sulfoxide, stir and react at 25 °C for 24 h, filter, wash with deionized water and ethanol, then add to 2 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0021] Comparative Example 1: The difference between this comparative example and Example 1 is that an equal molar amount of 1,8-octanediol is used instead of the thiourea quaternary ammonium salt modifier.

[0022] (1) Add 30 g of sodium alginate, 2.13 g (14.56 mmol) of 1,8-octanediol, 0.6 g of 4-dimethylaminopyridine, and 3.6 g of N,N'-dicyclohexylcarbodiimide to 1.2 L of dimethyl sulfoxide, stir and react at 25 °C for 24 h, filter, wash with deionized water and ethanol, then add to 2 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0023] Comparative Example 2: The difference between this comparative example and Example 1 is that an equimolar amount of N-methyldiethanolamine quaternary ammonium salt is used instead of the thiourea quaternary ammonium salt modifier.

[0024] (1) N-methyldiethanolamine quaternary ammonium salt was prepared according to the method of the master's thesis "Preparation and Characterization of New Photocurable Quaternary Ammonium / Quaternary Phosphonium Composite Antibacterial Coating" of Beijing University of Chemical Technology. 20mmol N-methyldiethanolamine was added to 40mL acetonitrile, and 22mmol 1-bromodecane was added dropwise at 50℃. The mixture was stirred for 24h. Ether was added to the solution to precipitate the precipitate. The precipitate was filtered, washed with ether, and dried to obtain N-methyldiethanolamine quaternary ammonium salt. The structural formula is .

[0025] (2) Add 30 g of sodium alginate, 4.95 g (14.56 mmol) of N-methyldiethanolamine quaternary ammonium salt, 0.6 g of 4-dimethylaminopyridine, and 3.6 g of N,N'-dicyclohexylcarbodiimide to 1.2 L of dimethyl sulfoxide, stir and react at 25 °C for 24 h, filter, wash with deionized water and ethanol, then add to 2 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0026] Comparative Example 3: This comparative example differs from Example 1 in that an equimolar amount of N-benzoyl-N',N'-dihydroxyethylthiourea is used instead of the thiourea quaternary ammonium salt modifier.

[0027] (1) N-benzoyl-N', N'-dihydroxyethylthiourea was prepared according to the method of the master's thesis "Synthesis and Crystal Structure Study of Acylthiourea and Its Complexes" of Northwest Normal University. 15mmol of ammonium thiocyanate (NH4SCN) was added to 10mL of dichloromethane, and 0.2mL of polyethylene glycol 400 was added. The mixture was stirred at 25℃ for 1h. The filtrate was collected after filtration. The filter cake was washed with 10mL of dichloromethane and the filtrate was collected. The filtrate was combined, and then 10mmol of diethanolamine was added to the filtrate. The mixture was stirred at 25℃ for 1h. The mixture was distilled under reduced pressure and the product was recrystallized in ethanol to obtain N-benzoyl-N', N'-dihydroxyethylthiourea. The structural formula is .

[0028] (2) Add 30 g of sodium alginate, 4.11 g (14.56 mmol) of N-benzoyl-N',N'-dihydroxyethylthiourea, 0.6 g of 4-dimethylaminopyridine, and 3.6 g of N,N'-dicyclohexylcarbodiimide to 1.2 L of dimethyl sulfoxide, stir and react at 25 °C for 24 h, filter, wash with deionized water and ethanol, then add to 2 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0029] Example 2

[0030] (1) Add 15 mmol of p-phenylenediisocyanate and 36 mmol of N,N-dimethylethylenediamine to 35 mL of ethanol, stir and react at 25 °C for 3 h, and distill under reduced pressure. The product is washed with deionized water and petroleum ether, and then recrystallized from chloroform to obtain a thiourea precursor.

[0031] (2) Add 10 mmol of thiourea precursor and 30 mmol of 6-bromo-1-hexanol to 30 mL of acetonitrile, heat to 80 °C, stir and reflux for 48 h, distill under reduced pressure, wash with petroleum ether, and recrystallize the product in ethanol to obtain a thiourea quaternary ammonium salt modifier.

[0032] (3) Add 30 g of sodium alginate, 18 g of thiourea quaternary ammonium salt modifier, 1.2 g of 4-dimethylaminopyridine, and 7.2 g of N,N'-dicyclohexylcarbodiimide to 1 L of dimethyl sulfoxide, stir and react at 20 °C for 36 h, filter, wash with deionized water and ethanol, then add to 2 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0033] Example 3

[0034] (1) 10 mmol of thiourea precursor (prepared in Example 1) and 26 mmol of 4-bromo-1-butanol were added to 25 mL of acetonitrile, heated to 85°C, stirred and refluxed for 36 h, distilled under reduced pressure, washed with petroleum ether, and recrystallized from ethanol to obtain a thiourea quaternary ammonium salt modifier.

[0035] (2) Add 30 g of sodium alginate, 27 g of thiourea quaternary ammonium salt modifier, 1.8 g of 4-dimethylaminopyridine, and 10.8 g of N,N'-dicyclohexylcarbodiimide to 1.2 L of dimethyl sulfoxide, stir and react at 30 °C for 36 h, filter, wash with deionized water and ethanol, then add to 3 L of deionized water and soak for 24 h, filter, and dry to obtain a modified adsorbent.

[0036] Example 4

[0037] (1) To 1.5 L of dimethyl sulfoxide, 30 g of sodium alginate, 36 g of thiourea quaternary ammonium salt modifier (prepared in Example 1), 2.4 g of 4-dimethylaminopyridine, and 14.4 g of N,N'-dicyclohexylcarbodiimide were added, stirred and reacted at 20 °C for 48 h, filtered, washed with deionized water and ethanol, and then added to 3 L of deionized water and soaked for 24 h. After filtering and drying, a modified adsorbent was obtained.

[0038] Example 5

[0039] (1) To 1.5 L of dimethyl sulfoxide, 30 g of sodium alginate, 45 g of thiourea quaternary ammonium salt modifier (prepared in Example 1), 3 g of 4-dimethylaminopyridine, and 18 g of N,N'-dicyclohexylcarbodiimide were added, stirred and reacted at 25 °C for 48 h, filtered, washed with deionized water and ethanol, and then added to 3 L of deionized water and soaked for 24 h, filtered, and dried to obtain a modified adsorbent.

[0040] Add copper nitrate to 500 mL of water to make Cu 2+ Add 20 mg of modified adsorbent to the 20 mg / L standard solution, stir and adsorb at 25 °C for 4 h, take the supernatant, and test Cu by atomic absorption spectrophotometry. 2+ The adsorption capacity was calculated based on the concentration of .

[0041] Add lead nitrate to 500mL of water to make Pb 2+ Add 20 mg of modified adsorbent to a 20 mg / L standard solution, stir and adsorb at 25 °C for 3 h, take the supernatant, and test Pb by atomic absorption spectrophotometry. 2+ The adsorption capacity was calculated based on the concentration of .

[0042] Add cadmium nitrate to 500mL of water to prepare Cd 2+Add 20 mg of modified adsorbent to the standard solution with a concentration of 20 mg / L, stir and adsorb at 25 °C for 4 h, take the supernatant, and test Cd by atomic absorption spectrophotometry. 2+ The adsorption capacity was calculated based on the concentration of .

[0043] Add potassium dichromate to 500mL of water to make Cr2O7 2- Add 20 mg of modified adsorbent to the standard solution with a concentration of 20 mg / L, stir and adsorb at 25 ° C for 4 hours, take the supernatant, and test Cr2O7 by diphenylcarbazide spectrophotometry 2- The adsorption capacity was calculated based on the concentration of .

[0044] Adsorption capacity = (C0-C) × V / m. C is the concentration of the metal solution after adsorption, C0 is the concentration of the metal solution before adsorption, V is the volume of the solution, and m is the amount of modified adsorbent used.

[0045] Table 1 Metal ion adsorption capacity test

[0046]

[0047] After testing, Examples 1-5 used the two hydroxyl groups of the thiourea quaternary ammonium salt modifier to carry out esterification cross-linking reaction with the carboxyl group of sodium alginate to obtain a sodium alginate-based modified adsorbent. A large number of thiourea groups and quaternary ammonium salt groups were introduced into the sodium alginate matrix. The amino groups and sulfur atoms in the thiourea groups reacted with Cu 2+ , Pb 2+ 、Cd 2+ There is a strong complexation between them, which has strong chelating adsorption performance. The quaternary ammonium salt cation and Cr2O7 2- There are positive and negative electrostatic interactions between anions, which makes the modified adsorbent have a high adsorption capacity for these metal ions.

[0048] Compared with Example 1, the modified adsorbent obtained by esterification reaction of 1,8-octanediol with sodium alginate does not contain thiourea groups and quaternary ammonium salt groups. 2+ , Pb 2+ 、Cd 2+ The complexation between them is low, and it is difficult to react with Cr2O7 2- The positive and negative electrostatic interactions are formed between them, resulting in a very low adsorption capacity of the adsorbent for these metal ions. Comparative Example 2: N-methyldiethanolamine quaternary ammonium salt is used to esterify sodium alginate to obtain a modified adsorbent that does not contain thiourea groups and has a strong affinity for Cu 2+ , Pb 2+ 、Cd 2+ The complexation between them is low, and the N-methyldiethanolamine quaternary ammonium salt contains only one quaternary ammonium salt group, resulting in the quaternary ammonium salt content in the adsorbent being less than that of the modified adsorbent in Example 1, and the adsorption of Cr2O72- The adsorption capacity is low. Comparative Example 3: N-benzoyl-N', N'-dihydroxyethylthiourea is used to esterify sodium alginate. The modified adsorbent obtained does not contain quaternary ammonium salt groups and is difficult to adsorb with Cr2O7 2- The positive and negative electrostatic interactions are formed between them, and N-benzoyl-N', N'-dihydroxyethyl thiourea contains only one thiourea structure, resulting in the thiourea structure content in the adsorbent being less than that of the modified adsorbent in Example 1. 2+ , Pb 2+ 、Cd 2+ The adsorption capacity is low.

[0049] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a modified adsorbent, characterized in that: The preparation method is: (1) Adding p-phenylenediisocyanate and N,N-dimethylethylenediamine to ethanol, distilling under reduced pressure after the reaction, washing, and recrystallizing the product to obtain a thiourea precursor; (2) Adding thiourea precursor and bromohydrin to acetonitrile, distilling under reduced pressure after the reaction, washing, and recrystallizing the product to obtain a thiourea quaternary ammonium salt modifier; (3) Sodium alginate, thiourea quaternary ammonium salt modifier, 4-dimethylaminopyridine, and N,N'-dicyclohexylcarbodiimide are added to dimethyl sulfoxide, and after the reaction, the mixture is filtered, washed, and then added to deionized water for soaking, filtered, and dried to obtain a modified adsorbent.

2. The method for preparing the modified adsorbent according to claim 1, wherein The molar ratio of p-phenylenediisocyanate to N,N-dimethylethylenediamine in (1) is 1:(2-2.4).

3. The method for preparing the modified adsorbent according to claim 1, wherein The reaction in (1) is stirred at 20-25°C for 3-4 hours.

4. The method for preparing the modified adsorbent according to claim 1, wherein The molar ratio of the thiourea precursor to the bromohydrin in (2) is 1:(2.6-3.4).

5. The method for preparing the modified adsorbent according to claim 4, wherein: The structural formula of the bromohydrin is Br(CH2) n OH, n is any integer from 2 to 6.

6. The method for preparing the modified adsorbent according to claim 1, wherein: The reaction in (2) is stirred at 80-85°C for 36-48 hours.

7. The method for preparing the modified adsorbent according to claim 1, wherein: The mass ratio of sodium alginate, thiourea quaternary ammonium salt modifier, 4-dimethylaminopyridine and N,N'-dicyclohexylcarbodiimide in (3) is 1:(0.3-1.5):(0.02-0.1):(0.12-0.6).

8. The method for preparing the modified adsorbent according to claim 1, wherein The reaction in (3) is stirred at 20-30°C for 24-48 hours.

9. Use of the modified adsorbent obtained by the preparation method according to any one of claims 1 to 8 in metallurgical wastewater.

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