CN112387256A - Preparation method and application of pyridylamine-based composite hydrogel adsorbent - Google Patents
Preparation method and application of pyridylamine-based composite hydrogel adsorbent Download PDFInfo
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Abstract
The invention belongs to the field of environmental functional materials, and provides a preparation method and application of a pyridylamine-based composite hydrogel adsorbent aiming at the problem of efficiently and quickly removing heavy metal cations in strong-acid wastewater; the preparation method comprises the following steps: dissolving an acid-binding agent, an aminopyridinization modification reagent and polyethyleneimine in a water-organic mixed solution, and performing substitution reaction to prepare a modified solution; dialyzing or ultrafiltering or nanofiltering the modified solution to obtain a refined PEIPD solution; uniformly mixing the PEIPD solution and the polymer solution, and performing crosslinking and gelation reaction to obtain a pyridylamine-based composite hydrogel adsorbent; the hydrogel adsorbent has the advantages of low cost of raw materials, simple preparation technology and suitability for large-scale production; the hydrogel adsorbent can be used for directly treating strong-acid wastewater containing heavy metals without regulating pH, so that the high-efficiency and rapid removal of a plurality of heavy metal cations such as Pb (II), Cd (II), Ni (II), Cu (II), Zn (II), Co (II) and the like can be realized.
Description
Technical Field
The invention belongs to the field of environmental functional materials, and particularly relates to preparation of a pyridylamine-based composite hydrogel adsorbent and efficient removal of heavy metal cations in strong-acid wastewater.
Background
Strongly acidic wastewater (pH <3.0) containing heavy metals is widely derived from various heavy-duty industrial activities, including mining, metal smelting, acid leaching and detoxification of heavy-solid-containing wastewater, acid pickling of non-ferrous metals, and the like. The wastewater is large in amount and complex in components, not only contains various heavy metal ions such as lead, cadmium, nickel, copper and the like, but also can contain high-concentration inorganic salts such as sodium sulfate, calcium chloride and the like. Because the pH value of the wastewater is low, most of the prior engineering adopts a neutralization precipitation method to treat the wastewater, but the practical problems of large alkali adding amount, large generation amount of dangerous waste sludge and the like can be caused. The current concept of recycling economy and green development encourages low energy and low consumption treatment of wastewater, from which useful resources are recovered as much as possible. The disadvantages of the neutralization precipitation method and the lack of effective utilization of inorganic acid resources in the wastewater make the method no longer the optimal choice for treating the wastewater. It is of great significance to develop efficient and economical methods and techniques to directly separate and recover heavy metal resources from strongly acidic wastewater and to achieve attenuated treatment of such wastewater. The current widely applied methods such as membrane separation method, crystallization method, solvent extraction method, electrolysis method and the like are not suitable for wastewater with low heavy metal concentration (<50mg/L) because of relatively high energy consumption and material consumption cost. In comparison, the adsorption method has high separation efficiency and low energy consumption cost, and can adapt to wide variation of the concentration of heavy metal ions, so that the adsorption method is favored.
However, the separation and recovery of heavy metal cations from strongly acidic wastewater by adsorption still have some challenges, mainly because the high concentration of hydrogen ions compete for adsorption sites, resulting in a low adsorption capacity of most adsorbents for heavy metal cations. For example, some amino-functional based adsorbents have a greatly reduced adsorption of heavy metal cations due to protonation of the amino group at pH <3.0 and essentially 0 at pH < 1.5. In addition, the presence of inorganic salts in large amounts may also cause a reduction in the performance of some ion exchange adsorbents. For example, although the iminodiacetic acid sodium type and aminophosphonic acid type adsorbents have a certain adsorption effect on heavy metals at a pH of 2.0, their adsorption performance is significantly reduced when the concentration of the coexisting inorganic salt is increased to 0.1 mol/L. The research of the subject group finds that the chelating adsorbent has the advantage of resisting the interference of high-concentration inorganic salt compared with an ion exchange adsorbent, and the existence of the inorganic salt plays a role in promoting the chelating adsorbent to capture most heavy metal cations. Therefore, in view of the fact that some international commercial pyridyl resins such as Dowex M4195, Lewatit MonoPlus TP220, etc. have a high adsorption capacity (about 1.0mmol/g) to heavy metal cu (ii) under a strong acidic environment with pH of 1.0, the subject group developed a series of pyridylamine-based chelating resins (patent application No. 201911375554.9) that achieve a better adsorption effect to various heavy metal cations under a strong acidic environment. However, the pyridine amine chelating resins have a slow adsorption rate as commercial pyridine resins, and usually require 18-36 h to reach adsorption balance, which limits the practical engineering processing capacity of the pyridine amine chelating resins.
The hydrogel adsorbent is a very hydrophilic gel with a three-dimensional network structure, and the abundant pore structure of the hydrogel adsorbent creates favorable conditions for the diffusion of heavy metal ions and the contact of the heavy metal ions and adsorption sites, so that most of hydrogel adsorbents have the characteristic of high adsorption rate. Sodium alginate is a very good encapsulation biopolymer, and can form a solution with high viscosity and is very easy to form at a low mass concentration. Therefore, this group proposed mixing the refined pyridylamine-PEI polymer with sodium alginate to make a hydrogel adsorbent.
The pyridylamine-based structure is not uncommon in adsorbents, but is mainly present in resin-based adsorbents. In addition to commercial pyridyl resins and pyridylamine chelate resins developed by this group, other pyridyl-containing adsorption resins were not used for the separation and recovery of heavy metal cations from wastewater under strongly acidic conditions. For example, patents relating to pyridyl resins have been issued, the resin in the document of application No. 87103759 is used for separating noble metal Au, and the resin in the document of application No. 200610039862.0 is used for adsorption and separation of organic substances in the fields of drug separation, food decolorization, and the like. The patent only discloses that a pyridylamine-based structure is compounded with a hydrogel carrier, and the patent (application number: 201910696803.8) mixes and crosslinks pyridylated modified PEI and chitosan to prepare chitosan hydrogel, and is used for synchronously removing heavy metals and antibiotics in livestock and poultry breeding wastewater. At present, no report is found about the situation that the pyridylamine-PEI polymer is refined by a dialysis mode (or ultrafiltration and nanofiltration) and is mixed with sodium alginate to prepare hydrogel, and the hydrogel is used for separating and recovering heavy metal cations in strong-acid wastewater.
Disclosure of Invention
Aiming at the problems of extremely low adsorption capacity or low adsorption rate and the like of the existing adsorbent in strong acid wastewater, the invention provides a preparation method and an application method of a pyridylamine-based composite hydrogel adsorbent capable of quickly removing heavy metal cations in strong acid wastewater.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a pyridine amino composite hydrogel adsorbent comprises the following steps:
(a) chemical modification: dissolving an acid-binding agent and an aminopyridinization modification reagent in water in sequence, adding a certain amount of hydrophilic organic solvent, adding a certain amount of Polyethyleneimine (PEI) solution, and stirring uniformly at normal temperature to obtain a mixed solution. And carrying out substitution reaction on the mixed solution at the temperature of 60-100 ℃ for 1-24h to prepare the modified solution.
(b) Refining: transferring the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in water. And (3) evaporating and concentrating the dialyzed modified solution to obtain a refined PEIPD solution. Or treating the modified solution obtained in the step (a) by using an ultrafiltration and nanofiltration method, and also obtaining a refined PEIPD solution.
(c) Preparing a gel: weighing a certain amount of polymer capable of being prepared into hydrogel, and dissolving the polymer in water to prepare sol serving as a PEIPD carrier. Uniformly mixing the PEIPD solution finally prepared in the step (b) with the sol according to a certain proportion, and carrying out cross-linking and gelation reaction to obtain the pyridylamino composite hydrogel adsorbent.
Preferably, the acid-binding agent in step (a) is one or any combination of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, pyridine, triethylamine and the like; the aminopyridinization modification reagent is one or any combination of 2-chloromethylpyridine, 2-bromomethylpyridine, 2-chloromethylpyridine hydrochloride and 2-bromomethylpyridine hydrobromide; the hydrophilic organic solvent is one or any combination of methanol, ethanol, propanol, butanol, isopropanol, 1, 4-dioxane, acetone, tetrahydrofuran, etc.; the molecular weight of PEI is 3000-100000 dalton, and the concentration of PEI in the mixed solution is controlled to be 0.5-5.0 wt%.
Preferably, the mass concentration of the acid-binding agent in the mixed solution in the step (a) is 5-200 g/L; the mass concentration of the aminopyridinization modification reagent is 5-200 g/L; the volume concentration of the organic solvent is 5-90%; the mass concentration of the polyethyleneimine is 3-100 g/L.
Preferably, the dialysis bag used in step (b) has a size of m.w.500 to 3000 dalton.
Preferably, the mass concentration of PEIPD in the mixed solution in the step (c) is 5-150g/L, and the mass concentration of the polymer of the hydrogel is 5-100 g/L.
Preferably, the polymer capable of being made into hydrogel in step (c) comprises any one or more of sodium alginate, cellulose, hemicellulose, starch, gelatin, guar gum, polyvinyl alcohol and polyacrylic acid.
The invention preferably selects a method for preparing the pyridine amino composite hydrogel adsorbent with sodium alginate as a carrier, which comprises the following steps:
(d) weighing a certain amount of sodium alginate, heating and dissolving in deionized water to prepare a sodium alginate solution. Adjusting the pH value of the PEIPD solution finally prepared in the step (b) to 9.0-10.0, uniformly mixing the PEIPD solution with a sodium alginate solution according to a certain proportion to obtain a mixed solution, and adding a certain amount of concentrated NaOH solution to ensure that the mixed solution has no precipitate. Dropwise adding the mixed solution into a coagulating bath, carrying out cross-linking and gelation reaction at normal temperature for 1-24h, and packaging PEIPD in sodium alginate to obtain the bead-form pyridylamine-based composite hydrogel adsorbent.
Preferably, in the step (d), the mass concentration of PEIPD in the mixed solution is 5-150g/L, and the mass concentration of sodium alginate is 5-100 g/L.
Preferably, the coagulation bath in step (d) is formulated by dissolving inorganic salts and organic cross-linking agents in water. Wherein the inorganic salt is one or more of calcium chloride, calcium nitrate, barium chloride, barium nitrate and ferric chloride, the organic cross-linking agent is one or more of glutaraldehyde, succinaldehyde, epichlorohydrin and the like, the mass concentration of the inorganic salt in the coagulating bath is 5-200g/L, and the mass concentration of the organic cross-linking agent is 5-100 g/L.
Preferably, the hydrogel adsorbent in step (d) is preferably made into beads with a diameter of 0.5-5.0mm, but the form of preparation and application thereof is not limited to the beads.
The composite hydrogel adsorbent prepared by any one of the methods is applied to removal of heavy metal cations in strongly acidic wastewater and recovery of heavy metals.
The steps for removing heavy metal cations in the strongly acidic wastewater are as follows: directly adding the composite hydrogel adsorbent into the strongly acidic heavy metal wastewater, mixing and reacting for a plurality of times, and separating out the hydrogel adsorbent; or the composite hydrogel adsorbent is filled in a reaction vessel, so that the strongly acidic heavy metal wastewater flows through the reaction vessel.
Preferably, the pH of the strongly acidic heavy metal wastewater is less than 3.0, and the heavy metal cation is one or a combination of Pb (II), Cd (II), Ni (II), Cu (II), Zn (II) and Co (II).
The steps for recovering the heavy metal resources are as follows: and soaking the composite hydrogel adsorbent adsorbing the heavy metals in a proper amount of desorption agent to recover the heavy metal ions and regenerate the composite hydrogel adsorbent.
Preferably, the desorption agent is any one of concentrated hydrochloric acid and EDTA solution.
The main functional groups of the pyridine-amino composite hydrogel adsorbent are pyridyl and amino, and the pyridyl and amino groups can perform a synergistic coordination effect through free translation and rotation, so that heavy metal cations can be chelated and trapped, and the effect of separating and removing heavy metal cations from strongly acidic wastewater is achieved. And because the nitrogen atom belongs to the middle hard alkali, the nitrogen atom is difficult to be combined with the conventional alkali (earth) metal ion (Na) according to the soft and hard acid-base theory+、K+、Mg2+、Ca2+Etc.), so the pyridine amino composite hydrogel adsorbent provided by the invention has the advantage of resisting conventional inorganic salt.
In the invention, PEI is an abbreviation of polyethyleneimine, PEIPD is an abbreviation of PEI modified pyridylamine polymer, and SA is an abbreviation of sodium alginate.
Compared with most of the existing adsorbents, the composite hydrogel adsorbent provided by the invention has the following advantages:
(1) the composite hydrogel adsorbent provided by the invention can efficiently remove various heavy metal cations in strong acid wastewater (pH is less than 3.0), and has broad spectrum.
(2) The composite hydrogel adsorbent provided by the invention can still keep the adsorption capacity on heavy metal cations in a high-salt environment, and the coexisting inorganic salt has a promoting effect on the adsorption of most heavy metal cations.
(3) The composite hydrogel adsorbent provided by the invention has faster adsorption kinetics, can obtain higher adsorption capacity within 5 hours, and is obviously superior to pyridine amino chelating resin.
(4) The composite hydrogel adsorbent provided by the invention has the advantages of wide raw material source, simple synthesis steps, no need of complex treatment and industrial large-scale production.
(5) The composite hydrogel adsorbent provided by the invention forms a double-network structure by utilizing the cationic crosslinking of sodium alginate and the covalent bonding crosslinking of residual amino groups of PEI, has a stable structure, can deform under an external force instead of being directly crushed, and has strong engineering applicability.
Drawings
Fig. 1 is a flow chart of the preparation of the pyridine amine-based composite hydrogel adsorbent provided by the invention.
Fig. 2 shows the change of the adsorption amount (mmol/g) of the prepared optimum hydrogel adsorbent J on the dry weight of the heavy metal cu (ii) at pH 1.0 with the adsorption time.
Detailed Description
For a better understanding of the present invention, reference will now be made in detail to the following description taken in conjunction with the accompanying drawings and detailed description.
Example 1:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) sequentially dissolving 2.00g of anhydrous sodium carbonate and 3.000g of 2-chloromethylpyridine hydrochloride in 50mL of deionized water, adding 10mL of anhydrous ethanol, adding 2.0g of 50 wt% Polyethyleneimine (PEI) solution (MW 70000), stirring at normal temperature to mix uniformly, and reacting the mixed solution at 90 ℃ for 2-8 hours to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, and adding 4mL of deionized water. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (3) washing the beads for multiple times by using deionized water to prepare the pyridine amino composite hydrogel adsorbent. Marking the final hydrogel adsorbents prepared in the step (a) with the reaction time of 2h, 4h, 6h and 8h at 90 ℃ as A, B, C and D respectively.
(d) 0.120g of the above four wet hydrogel beads a, B, C and D were weighed, placed in a 60mL glass bottle, 50mL of a cu (ii) solution with an initial concentration of 1.0mmol/L, pH ═ 1.0 was added, the solution was shaken at 160r/min for 24 hours in a 298K constant temperature shaker to allow the adsorption to reach equilibrium, the cu (ii) concentration in the solution at the initial and equilibrium times was measured and the corresponding dry weight adsorption (mmol/g) was calculated.
Example 2:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 2.25g of anhydrous sodium carbonate and 3.375g of 2-chloromethylpyridine hydrochloride were dissolved in 50mL of deionized water in this order, 10mL of anhydrous ethanol was added, and 2.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, followed by stirring at room temperature to mix them uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, adding 4mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (4) washing the beads for multiple times by using deionized water to prepare the pyridine amino composite hydrogel adsorbent, which is marked as E.
(d) 0.120g of the above wet hydrogel beads E are weighed out separately and placed in a 60mL glass bottle, 50mL of a Cu (II) solution with an initial concentration of 1.0mmol/L, pH-1.0 is added, the adsorption is equilibrated by shaking at 160r/min in a 298K constant temperature shaker for 24h, the concentration of Cu (II) in the solution at the initial and at the equilibrium is determined and the corresponding dry weight adsorption (mmol/g) is calculated.
Example 3:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 2.50g of anhydrous sodium carbonate and 3.750g of 2-chloromethylpyridine hydrochloride were dissolved in 50mL of deionized water in this order, 10mL of anhydrous ethanol was added, and 2.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, followed by stirring at room temperature to mix them uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, adding 4mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (4) washing the beads for multiple times by using deionized water to prepare the pyridine amino composite hydrogel adsorbent, which is marked as F.
(d) 0.120g of the above wet hydrogel beads F was weighed out, placed in a 60mL glass bottle, 50mL of a cu (ii) solution with an initial concentration of 1.0mmol/L, pH ═ 1.0 was added, the adsorption was equilibrated by shaking at 160r/min in a 298K constant temperature shaker for 24 hours, the cu (ii) concentration in the solution at the initial and equilibrium was measured and the corresponding dry weight adsorption (mmol/g) was calculated.
Example 4:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 2.75g of anhydrous sodium carbonate and 4.125g of 2-chloromethylpyridine hydrochloride were dissolved in 50mL of deionized water in this order, 10mL of anhydrous ethanol was added, and 2.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, followed by stirring at room temperature to mix them uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, adding 4mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (4) washing the beads for multiple times by using deionized water to prepare the pyridine amino composite hydrogel adsorbent, which is marked as G.
(d) 0.120G of the above wet hydrogel beads G was weighed out, placed in a 60mL glass bottle, 50mL of a cu (ii) solution with an initial concentration of 1.0mmol/L, pH ═ 1.0 was added, the adsorption was equilibrated by shaking at 160r/min in a 298K constant temperature shaker for 24 hours, the cu (ii) concentration in the solution at the initial and equilibrium was measured and the corresponding dry weight adsorption (mmol/G) was calculated.
Example 5:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 3.00g of anhydrous sodium carbonate and 4.500g of 2-chloromethylpyridine hydrochloride were dissolved in 50mL of deionized water in this order, 10mL of anhydrous ethanol was added, and 2.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, followed by stirring at room temperature to mix them uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, adding 4mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (4) washing the beads for multiple times by using deionized water to prepare the pyridylamine-based composite hydrogel adsorbent, which is marked as H.
(d) 0.120g of the above wet hydrogel beads H are weighed out separately and placed in a 60mL glass bottle, 50mL of a Cu (II) solution with an initial concentration of 1.0mmol/L, pH-1.0 is added, the adsorption is equilibrated by shaking at 160r/min in a 298K constant temperature shaker for 24H, the concentration of Cu (II) in the solution at the initial and at the equilibrium is determined and the corresponding dry weight adsorption (mmol/g) is calculated.
Example 6:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 6.75g of anhydrous sodium carbonate and 10.125g of 2-chloromethylpyridine hydrochloride were dissolved in 150mL of deionized water in this order, 30mL of anhydrous ethanol was added, 6.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, and the mixture was stirred at room temperature to be mixed uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) putting 22.5-36.0 mL of the modified solution obtained in the step (a) into a dialysis bag, and dialyzing in deionized water. The volume ratio of the deionized water to the modification solution was controlled to 40. The water is changed every 1.5h for 4 times. Pouring the dialyzed polymer solution into a beaker, and heating and concentrating to obtain about 15mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH of the 15mL of PEIPD concentrated solution obtained in the step (b) to 9.4, and then mixing with 9g of 4.5% sodium alginate solutionRapidly mixing the mixture evenly under vigorous stirring, adding 3mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. And (3) washing the beads for multiple times by using deionized water to prepare the pyridine amino composite hydrogel adsorbent. In the labeling step (b), 22.5mL, 27.0mL, 31.5mL and 36.0mL of the modified solution are used, and the finally prepared hydrogel adsorbents are I, J, K and L respectively.
(d) 0.120g of each of the four wet hydrogel beads I, J, K, L described above was weighed into a 60mL glass bottle, 50mL of a cu (ii) solution with an initial concentration of 1.0mmol/L, pH ═ 1.0 was added, the solution was shaken at 160r/min for 24 hours in a 298K constant temperature shaker to allow the adsorption to reach equilibrium, the cu (ii) concentration in the solution at the initial and equilibrium times was measured and the corresponding dry weight adsorption (mmol/g) was calculated.
Example 7:
preparation and application of a pyridylamine-based composite hydrogel adsorbent, which comprises the following steps:
(a) 2.25g of anhydrous sodium carbonate and 3.375g of 2-chloromethylpyridine hydrochloride were dissolved in 50mL of deionized water in this order, 10mL of anhydrous ethanol was added, and 2.0g of a 50 wt% Polyethyleneimine (PEI) solution (MW 70000) was added, followed by stirring at room temperature to mix them uniformly. Reacting the mixed solution at 90 ℃ for 2h to obtain a modified solution;
(b) taking 24mL of the modified solution obtained in the step (a) to an ultrafiltration device for ultrafiltration treatment, and supplementing deionized water to obtain about 20mL of PEIPD concentrated solution;
(c) 4.5g of Sodium Alginate (SA) was weighed out and dissolved in 100mL of deionized water to make a 4.5% sodium alginate solution. Adjusting the pH value of the 20mL of PEIPD concentrated solution obtained in the step (b) to 9.4, rapidly and uniformly mixing the solution with 12g of 4.5% sodium alginate solution under vigorous stirring to ensure that the mass ratio of SA to PEIPD is 1:2, adding 4mL of deionized water, and adding 0.1mL of 2.0mol/L NaOH solution to ensure that the mixed solution has no precipitate. The mixture was added dropwise to 200mL of a coagulation bath (2 wt% CaCl)2+5 wt% glutaraldehyde), and reacting for 2h at normal temperature. The beads are washed by deionized water for a plurality of times to prepare the pyridylamino composite hydrogelGel adsorbent, noted M.
(d) 0.120g of the above-mentioned wet hydrogel beads M were weighed out, placed in a 60mL glass bottle, 50mL of a cu (ii) solution with an initial concentration of 1.0mmol/L, pH ═ 1.0 was added, the adsorption was equilibrated by shaking at 160r/min in a 298K constant temperature shaker for 24 hours, the cu (ii) concentration in the solution at the initial and equilibrium was measured and the corresponding dry weight adsorption (mmol/g) was calculated.
Example 8:
the dry weight adsorption amounts of the 13 pyridylamine-based composite hydrogel adsorbents prepared in examples 1 to 7 to the heavy metal cu (ii) at pH 1.0 are shown in table 1 below, and the results show that the performance of the hydrogel adsorbent J is relatively optimal.
TABLE 1 comparison of the adsorption Performance of the hydrogel adsorbents obtained in examples 1 to 7 for Cu (II)
Example 9:
the pyridylamine-based composite hydrogel adsorbent J with the best performance prepared in examples 1 to 7 was selected and studied for its adsorption performance on Pb (II), Cd (II), Ni (II), Cu (II), Zn (II) and Co (II) under strong acid and high salt conditions.
(1) Heavy metal adsorption experiment: weighing 0.120g of pyridylamine-based composite hydrogel adsorbent J, placing the pyridylamine-based composite hydrogel adsorbent J into a 60mL glass bottle, adding 50mL of heavy metal solution with the initial concentration of 1.0mmol/L and the adjusted pH (1 and 2), oscillating the solution in a 298K constant-temperature oscillator at 160r/min for 24h to balance the adsorption, measuring the concentrations of heavy metal ions in the solution at the initial and equilibrium stages, and calculating the corresponding dry weight adsorption amount (mmol/g).
The results of the experiment are shown in table 2. The result shows that the hydrogel has an adsorption removal effect on various heavy metal ions under a strong acid condition, and has a good broad-spectrum removal capability.
TABLE 2 comparison of adsorption Performance (mmol/g) of hydrogel adsorbents for various heavy metal ions under strongly acidic conditions
(2) Inorganic salts affect the experiment at pH 2.0: 0.120g of pyridylamine-based composite hydrogel adsorbent J was weighed into a 60mL glass bottle, and 50mL of 100mM CaCl-containing adsorbent having an initial concentration of 1.0mmol/L, pH of 2.0 was added2Oscillating the heavy metal solution in a 298K constant temperature oscillator at 160r/min for 24h to enable the adsorption to reach the equilibrium, measuring the concentration of heavy metal ions in the solution at the initial stage and the equilibrium stage and calculating the corresponding dry weight adsorption amount (mmol/g).
The results of the experiment are shown in table 3. The result shows that the hydrogel still has an adsorption removal effect on each heavy metal ion under the strong acid high salt condition, and the existence of the inorganic salt promotes the adsorption of most heavy metal ions (except Pb) by the hydrogel. Therefore, the hydrogel can be applied to treatment of high-salinity heavy metal wastewater.
TABLE 3 comparison of adsorption performance (mmol/g) of hydrogel adsorbent to various heavy metal ions under strong acid and high salt conditions
Example 10:
the pyridylamine-based composite hydrogel adsorbent J prepared in examples 1 to 7, which had the best performance, was selected and its adsorption kinetics under strongly acidic conditions (pH 1.0) were studied for cu (ii).
0.240g of pyridylamine-based composite hydrogel adsorbent J is weighed, placed in a 250mL conical flask, added with 100mL of a heavy metal Cu (II) solution with an initial concentration of 1.0mmol/L, pH-1.0, shaken at 160r/min in a 298K constant temperature shaker, and 0.1mL is sampled at 0, 30, 60, 90, 120, 180, 240, 300, 360, 540, 720, 1440min to determine the concentration of residual heavy metal Cu (II) and calculate the dry weight adsorption amount (mmol/g) of the hydrogel.
The results of the experiment are shown in FIG. 2. The result shows that the prepared pyridylamine-based composite hydrogel adsorbent has a fast adsorption dynamic performance on heavy metals under a strong acid condition, can obtain a high adsorption capacity within 5 hours, and is obviously superior to pyridylamine-based chelating resin which can reach the same adsorption level only within 12-24 hours.
Example 11:
the pyridylamine-based composite hydrogel adsorbent J with the optimal performance prepared in the examples 1 to 7 is selected, and the desorption effect of different desorbents on Cu (II) adsorbed by the desorbents is studied.
0.240g of pyridylamine-based composite hydrogel adsorbent J is weighed, placed in a 250mL conical bottle, added with 100mL of a heavy metal Cu (II) solution with the initial concentration of 1.0mmol/L, pH-1.0, shaken at 160r/min for 24h in a 298K constant temperature shaker, the concentration of the residual heavy metal Cu (II) is measured, and the dry weight adsorption capacity (mmol/g) of the hydrogel is calculated. The adsorbent J having cu (ii) adsorbed thereon was filtered, and placed in 20mL of 10% concentrated hydrochloric acid, 20% concentrated hydrochloric acid, 0.5mol/L EDTA solution (pH 6.0), and 1.0mol/L EDTA solution (pH 6.0), respectively, and shaken at 160r/min for 12 hours to measure the concentration of the desorbed heavy metal cu (ii) and calculate the recovery efficiency.
The results of the experiment are shown in table 4. The results show that the recovery efficiency of Cu (II) can reach more than 90 percent by using 20 percent concentrated hydrochloric acid or 1.0mol/L EDTA solution. And the binding stability of other heavy metal cations and the hydrogel adsorbent is not as good as that of Cu (II), so that the desorption effect is better.
TABLE 4 Desorption Effect of different Desorption Agents on Cu (II) on hydrogel adsorbents
The invention and its embodiments have been described above schematically. The description is not intended to be limiting and the data presented is merely the result of an embodiment of the invention and the data in actual use is not so limited. The present invention is not limited to the details given herein, but is within the ordinary knowledge of those skilled in the art. Therefore, if the person skilled in the art receives the teaching of the present invention, the embodiment and the embodiment similar to the technical solution should be covered by the protection scope of the present invention without creatively designing the same without departing from the spirit of the invention.
Claims (10)
1. The preparation method of the pyridine amino composite hydrogel adsorbent is characterized by comprising the following steps of:
dissolving an acid-binding agent and an aminopyridinization modification reagent in a mixed solution of water and an organic solvent, and adding a polyethyleneimine solution to react to obtain a modified solution;
step two, refining the modified solution obtained in the step one to obtain a refined PEIPD solution;
and step three, mixing the refined PEIPD solution with a polymer solution of the hydrogel to prepare the pyridylamino composite hydrogel adsorbent.
2. The method for preparing the pyridylamine-based composite hydrogel adsorbent according to claim 1, wherein the refining step in the second step is: dialyzing the modified solution, and evaporating and concentrating the dialyzed modified solution to obtain a refined PEIPD solution.
3. The method for preparing the pyridylamine-based composite hydrogel adsorbent according to claim 1, wherein the refining step in the second step is: and (3) carrying out ultrafiltration or nanofiltration on the modified solution to obtain a refined PEIPD solution.
4. The preparation method of the pyridine amine-based composite hydrogel adsorbent according to claim 1, wherein the preparation method comprises the following steps: in the first step, the acid-binding agent is any one or more of sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, sodium hydroxide, potassium hydroxide, pyridine and triethylamine; the aminopyridinization modification reagent is any one or more of 2-chloromethylpyridine, 2-bromomethylpyridine, 2-chloromethylpyridine hydrochloride and 2-bromomethylpyridine hydrobromide; the organic solvent is any one or more of methanol, ethanol, propanol, butanol, isopropanol, 1, 4-dioxane, acetone and tetrahydrofuran; the polymer of the hydrogel in the third step is any one or more of sodium alginate, cellulose, hemicellulose, starch, gelatin, guar gum, polyvinyl alcohol and polyacrylic acid.
5. The preparation method of the pyridine amino composite hydrogel adsorbent according to claim 4, wherein when the polymer of the hydrogel is sodium alginate, the preparation process of the third step is as follows:
(1) dissolving sodium alginate in water to obtain a sodium alginate solution;
(2) adjusting the pH value of the refined PEIPD solution to 9-12, and mixing the refined PEIPD solution with the sodium alginate solution obtained in the step (1) to obtain a mixed solution;
(3) and (3) dripping the mixed liquid obtained in the step (2) into a coagulating bath for reaction to obtain the pyridylamine-based composite hydrogel adsorbent.
6. The preparation method of the pyridine amine-based composite hydrogel adsorbent according to claim 5, wherein the preparation method comprises the following steps: in the step (2), the mass concentration of PEIPD in the mixed solution is 5-150g/L, and the mass concentration of sodium alginate is 5-100 g/L.
7. The preparation method of the pyridine amine-based composite hydrogel adsorbent according to claim 5, wherein the preparation method comprises the following steps: the reaction time in the step (3) is 1-24 h; the coagulating bath is formed by mixing inorganic salt, a cross-linking agent and water; wherein the inorganic salt is one or more of calcium chloride, calcium nitrate, barium chloride, barium nitrate and ferric chloride, and the cross-linking agent is one or more of glutaraldehyde, succinaldehyde and epichlorohydrin; the mass concentration of the inorganic salt in the coagulating bath is 5-200g/L, and the mass concentration of the cross-linking agent is 5-100 g/L.
8. The preparation method of the pyridine amine-based composite hydrogel adsorbent according to claim 1, wherein the preparation method comprises the following steps: in the first step, the reaction temperature is 60-100 ℃, and the reaction time is 1-24 h; the mass concentration of an acid-binding agent in the mixed solution obtained in the step one is 5-200g/L, the mass concentration of an aminopyridinization modification reagent is 5-200g/L, the volume concentration of an organic solvent is 5-90%, and the mass concentration of polyethyleneimine is 3-100 g/L; the mass concentration of PEIPD in the mixed solution in the third step is 5-150g/L, and the mass concentration of the polymer of the hydrogel is 5-100 g/L.
9. Use of the composite hydrogel adsorbent prepared by the method according to any one of claims 1 to 8 in removal of heavy metal cations in strongly acidic wastewater and recovery of heavy metals.
10. Use according to claim 9, characterized in that:
the steps for removing heavy metal cations in the strongly acidic wastewater are as follows: adding a composite hydrogel adsorbent into the strongly acidic heavy metal wastewater for reaction to remove heavy metal cations in the strongly acidic wastewater;
wherein, the pH of the strongly acidic heavy metal wastewater is less than 3.0, and the heavy metal cation is any one or more of Pb (II), Cd (II), Ni (II), Cu (II), Zn (II) and Co (II);
the steps for recovering heavy metals are as follows: soaking the composite hydrogel adsorbent adsorbed with the heavy metals in a desorption agent for elution, and recovering the heavy metals;
wherein the desorption agent is any one of concentrated hydrochloric acid and EDTA solution.
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