Heavy metal detection-adsorption integrated composite material, preparation method and application thereof

Abstract

The application belongs to the technical field of heavy metal detection and adsorption materials, and discloses a heavy metal detection-adsorption integrated composite material and a preparation method and application thereof.Under stirring conditions, a thiol-modified alginate is dissolved in water, an amino-modified carbon quantum dot solution is added to dope and crosslink to obtain a mixed solution, a calcium salt is added, and after uniform stirring, the mixed solution is placed and shaped, and then freeze-dried to obtain the heavy metal detection-adsorption integrated composite material.The amino-modified carbon quantum dots (CDs) are synthesized in one step by using an organic acid as a carbon source and polyethyleneimine as a nitrogen source, and the thiol-modified alginate is obtained by grafting alginate with a thiol donor reagent.The composite material is a fluorescence detection-adsorption integrated composite material (CDs / TA-gel) with an interpenetrating polymer network structure, has rich amine groups, carboxylic acid groups, hydroxyl groups and thiol groups, provides binding sites for heavy metal ions, and can quickly and sensitively detect and efficiently adsorb heavy metals copper and lead.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of heavy metal ion detection and adsorption materials, and particularly relates to a heavy metal detection-adsorption integrated composite material and a preparation method and application thereof. BACKGROUND

[0002] Metal ions are essentially non-degradable and can interact with organisms through the food chain, for example, they can easily bind to proteins, nucleic acids and small metabolites, blocking their biological functions, leading to serious health problems. Copper and lead ions are two common heavy metal ions in industrial wastewater, and even trace amounts can cause damage to the gastrointestinal system, kidneys, liver and central nervous system. Therefore, it is urgent to develop a material to detect the pollution of heavy metals in the water environment and remove it by adsorption to prevent the health hazards caused by heavy metal enrichment.

[0003] In recent years, various adsorbents have been developed for the treatment of heavy metal ion pollution in water, including activated carbon, biochar, ion exchange resins, biosorbents, hydrogels, etc. For example, patent CN117065724A uses Zr 4+ and carboxylic acid to form UiO-MOFs to adsorb heavy metal ions Pb 2+ However, the synthesis of the composite material requires strict control of the reaction conditions and has high preparation cost, and the carrier construction is difficult. In addition, an invention patent CN114307957A uses sulfuric acid to modify biomass straw, and then synthesizes biomass carbon for heavy metal ion adsorption in wastewater, but the adsorption capacity of the material is low, and it cannot be monitored in real time to control the amount of material to be put in according to the pollution situation, and the material is not easy to recover and degrade.

[0004] At the same time, the current widely used water quality heavy metal detection methods mainly include atomic absorption spectrometry, inductively coupled plasma method, ultraviolet-visible spectrophotometry, high performance liquid chromatography, electrochemical analysis method and biological detection method, etc. These methods have the defects of large instrument, high price, high running cost, inability to apply to continuous monitoring and on-site monitoring, etc. However, most of the currently developed materials can only perform detection or adsorption tasks alone, which seriously limits the actual application, and therefore, it is urgent to provide a composite material with high adsorption capacity, which integrates the detection and adsorption functions into one functional material to realize the simultaneous detection and adsorption of toxic heavy metal ions. SUMMARY

[0005] To solve the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a preparation method of a heavy metal detection-adsorption integrated composite material.

[0006] Another purpose of the present application is to provide a heavy metal detection-adsorption integrated composite material prepared by the above method.

[0007] Another purpose of the present application is to provide the application of the heavy metal detection-adsorption integrated composite material in heavy metal detection and adsorption.

[0008] The purpose of the present application is achieved by the following technical solutions:

[0009] A preparation method of a heavy metal detection-adsorption integrated composite material, comprising the following steps: dissolving a thiol-modified alginate in water under stirring, adding an amino-modified carbon quantum dot solution to dope and cross-link to obtain a mixed solution, adding a calcium salt to chelate, adding grape acid lactone after uniform stirring, standing and forming, and freeze-drying to obtain the heavy metal detection-adsorption integrated composite material.

[0010] The amino-modified carbon quantum dots form a Schiff base bond with the thiol-modified alginate, and the calcium salt chelates with the modified alginate. 2+ The final obtained composite material is an aerogel electrostatic network structure.

[0011] Preferably, the mass-volume ratio g / mL of the thiol-modified alginate and the amino-modified carbon quantum dot solution is 2-5:10-30, and more preferably 2:10.

[0012] The volume concentration of the amino-modified carbon quantum dot solution in the mixed solution is 5-15%, and more preferably 10%.

[0013] The mass-volume ratio g / mL of the thiol-modified alginate and water is 0.5-4:20-150.

[0014] Preferably, the amino-modified carbon quantum dot solution is prepared by hydrothermal reaction of a carbon source, a nitrogen source and water, and the mass-volume ratio g / g / mL of the carbon source, the nitrogen source and water is 0.1-0.5:0.6-3:20-100.

[0015] The thiol-modified alginate is obtained by grafting alginate with a thiol donor reagent.

[0016] Preferably, in the hydrothermal reaction, the nitrogen source and the carbon source are added to water and stirred until completely dissolved, the stirring speed is 200-1000 rpm, and the stirring time is 0.3-1 h.

[0017] Preferably, the hydrothermal reaction is heating at 150-200℃ for 12-24 h, and the product after the hydrothermal reaction is purified by dialysis, the dialysis molecular weight cut-off is 500-3000 D, and the dialysis time is 2-3 d to obtain the amino-modified carbon quantum dot solution.

[0018] Preferably, the carbon source is at least one of organic acids, specifically citric acid, malic acid, tartaric acid and oxalic acid.

[0019] The nitrogen source is at least one of polyethyleneimine, urea, and melamine, and is more preferably polyethyleneimine, with an average molecular weight of 600-10,000;

[0020] Preferably, the grafting steps include adding a catalyst to an aqueous alginate solution, adding a thiol donor reagent, adjusting the pH of the mixed solution, purifying the product by dialysis after sufficient reaction, freeze-drying, and obtaining the thiol-modified alginate.

[0021] Preferably, in the presence of the catalyst, the amino group of the thiol donor reagent condenses with the carboxyl group of the alginate, thereby grafting the thiol group onto the alginate molecule, and the surface of the prepared hydrogel has thiol functional groups, which can efficiently coordinate and complex with heavy metal ions, thereby improving the heavy metal adsorption performance of the microspheres.

[0022] Preferably, the thiol donor reagent is at least one of L-cysteine hydrochloride monohydrate and N-acetyl-L-cysteine; the alginate is at least one of sodium alginate, potassium alginate, and ammonium alginate, and the average molecular weight of the alginate is about 2×10 5 ~1×10 6 ; and the catalyst is a carbodiimide activator.

[0023] Preferably, the aqueous alginate solution is prepared by mixing alginate and water in a mass / volume ratio of 0.5-4:10-100 g / mL;

[0024] The mass / volume ratio of the thiol donor reagent to the aqueous alginate solution is 0.5-5:4-120 g / mL.

[0025] The dialysis molecular weight cut-off is 500-8,000 D, and the dialysis time is 1-2 days.

[0026] Preferably, the carbodiimide activator is at least one of dicyclohexyl carbodiimide (DCC), diisopropyl carbodiimide (DIC), and 1-ethyl- carbonyldiimidazole hydrochloride (EDC), and N-hydroxysuccinimide (NHS) or N-hydroxysulfosuccinimide (Sulfo-NHS) is added.

[0027] Preferably, the pH is adjusted to a range of 4.0-6.0, and the acid is at least one of analytical reagent (AR) hydrochloric acid, guaranteed reagent (GR) hydrochloric acid, and guaranteed reagent (GR) nitric acid, and the base is analytical reagent (AR) sodium hydroxide, and the acid and base are both diluted to a volume concentration of 1-3%.

[0028] Preferably, the stirring speed in the grafting reaction is 500-1,000 rpm, and the stirring time is 5-8 hours.

[0029] Preferably, the static molding is static molding poured into a mold, wherein the mold is a 0.5-1.2 cm diameter spherical silica gel mold.

[0030] Preferably, the temperature of the freeze-drying is -80 to -100 DEG C, and the time is 24-48 h.

[0031] Preferably, the calcium salt is calcium carbonate or calcium chloride.

[0032] A heavy metal detection-adsorption integrated composite material is prepared by the method.

[0033] The heavy metal detection-adsorption integrated composite material is applied in the field of heavy metal detection and / or adsorption.

[0034] Preferably, the heavy metal in the application is copper (II) or lead (II).

[0035] The present application uses green and safe natural polymer alginate as raw material, modifies the thiol group by adding thiol donor reagent, and uses small molecule organic acid and polyethylene imine to synthesize fluorescent carbon quantum dots, amino-modified fluorescent carbon dots can be crosslinked with alginate without chemical additives, the rich amino groups on the surface of carbon dots and their uniform distribution on aerogel provide more adsorption sites for metal ions, increase the aggregation and chelation of metal ions. The composite aerogel prepared by using alginate as the matrix and carbon dots as the fluorescent source realizes the dual functions of heavy metal ion adsorption and detection of the bio-based adsorbent.

[0036] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0037] (1) The raw material used in the present application is alginate, a natural polymer compound, which has the advantages of green environmental protection, safety, non-toxicity, biodegradability, etc., and is more healthy and environmentally friendly compared with existing adsorbents, showing its unique superiority.

[0038] (2) The present application uses detection-adsorption integrated technology to provide a new idea for the detection and adsorption of copper and lead pollution in water environment. By simply putting the composite material into wastewater, the fluorescence change of the small ball, the fluorescence of Cu 2+ is turned off, and the fluorescence of Pb 2+ is turned on, qualitative and quantitative analysis is carried out respectively, and by monitoring the fluorescence change in the adsorption process in real time, the amount of the composite material can be accurately controlled, and the cost is greatly saved.

[0039] (3) The composite material has low density and can float, and is easy to recover. After detection and adsorption are completed, the composite material can be salvaged and recovered, which is conducive to subsequent collection and treatment, realizes the complete removal of heavy metals, and has no risk of secondary release.

[0040] (4) The composite material has high water absorption, rich amine groups, carboxylic acid, hydroxyl and mercapto functional groups, good adsorption and detection effect on metal ions, high adsorption capacity, low detection limit and stability, and the adsorption capacity of copper and lead is 187.60 mg / g and 193.52 mg / g respectively, and the detection limit is 1.725 μmol / L and 1.495 μmol / L respectively.

[0041] (5) The preparation method is simple and low in cost, and is suitable for remediation and safe use of heavy metal copper and lead pollution in water environment. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 It is the infrared spectrum of SA and dried TA in Example 1.

[0043] Figure 2 It is the water absorption rate column chart of the composite materials obtained in Examples 1-4 and Comparative Examples 1-2, 5-8.

[0044] Figure 3 It is the adsorption capacity column chart of the heavy metal adsorption experiment of the composite materials obtained in Examples 1, 3, 4 and Comparative Examples 3-9.

[0045] Figure 4 It is the selectivity of the composite material CDs / TA-gel to metal ions at 355 nm.

[0046] Figure 5 It is the fluorescence change contrast real object diagram of the CDs solution in Example 1, the composite material CDs / TA-gel and the composite material CDs / CMCS-gel in Comparative Example 8 after adsorbing Cu 2+ , Pb 2+ solutions with different concentrations under 365 nm ultraviolet light.

[0047] Figure 6 It is the detection performance test result of the composite material CDs / TA-gel in Example 1 at 355 nm to Cu 2+ , Pb 2+ , a indicates the influence of Cu 2+ with different concentrations on the fluorescence intensity of CDs / TA-gel, b indicates the linear response curve of the detection of Cu 2+ , c indicates the influence of Pb 2+ with different concentrations on the fluorescence intensity of CDs / TA-gel, d indicates the linear response curve of the detection of Pb 2+ , wherein F0 is the fluorescence intensity of the composite material without adding Cu 2+ or Pb 2+ solution, and F is the fluorescence intensity of the composite material after adding Cu 2+ or Pb 2+Fluorescence intensity of the composite after solution.

[0048] Figure 7 Adsorption of Cu by CDs / TA-gel of Example 1 2+ and Pb 2+ Front and back photographs. DETAILED DESCRIPTION

[0049] The present application will be further described in conjunction with the examples and drawings, but the embodiments of the present application are not limited thereto.

[0050] The specific conditions not mentioned in the examples of the present application are carried out according to the conventional conditions or the conditions recommended by the manufacturers. The raw materials, reagents, etc. used without mentioning the manufacturers are all conventional products that can be purchased on the market.

[0051] Example 1

[0052] (1) At room temperature, 2.9 g of polyethyleneimine (PEI) with a relative molecular mass of 10,000 and a purity of 99% and 0.5 g of citric acid (CA) were weighed and dissolved in 100 mL of ionized water, stirred for 10 min until completely dissolved, and then subjected to a hydrothermal reaction with a heating temperature of 180°C and a reaction time of about 24 h to obtain a carbon quantum dot crude product. The product was placed in a dialysis bag with a molecular weight cut-off of 500 Da and continuously dialyzed for about 3 days to sufficiently remove unreacted molecular precursors, thereby obtaining a purified amino-modified carbon quantum dot solution (CDs).

[0053] (2) At room temperature, 1.0 g of sodium alginate (SA) was weighed into 50 mL of deionized water and mechanically stirred at 800 rpm until completely dissolved; 1.0 g of 1-ethyl-carbonyldiimidazole hydrochloride (EDC-HCl) and 1.2 g of N-hydroxysuccinimide (NHS) were added to the SA solution, and the carboxyl groups of SA were activated under stirring.

[0054] (3) After 1 h, 2.0 g of L-cysteine hydrochloride monohydrate (L-cys) was added to the solution of (2) above, and mechanically stirred at 500 rpm until completely dissolved. Then, the pH was adjusted to 5.0 with 1 mol / L NaOH solution, and stirred for 2 h. The product was then placed in a dialysis bag with a molecular weight cut-off of 500 Da and continuously dialyzed for about 2 days to sufficiently remove unreacted molecular precursors, thereby obtaining a thiol-modified sodium alginate solution (TA). Then, the product was freeze-dried at -80°C for 48 h.

[0055] (4) Under the condition of 400 rpm stirring, 2.0 g of TA freeze-dried in (3) was dissolved in 90 mL of deionized water, and 10 mL of CDs solution in (1) was added after 3 h.

[0056] (5) Take 2.0 g of CaCO3 and add it to the mixed solution of (4), stir until uniform, then add 0.5 g of gluconolactone, stir rapidly up and down at 800 rpm until uniform, pour into a silica gel mold with a diameter of 1.13 cm, stand to shape, then transfer to -80°C for freeze-drying for 24 h to obtain an aerogel ball composite material.

[0057] Example 2

[0058] Different from step (5) of Example 1, the mixed solution of step (4) is dropped into a 2% CaCl2 solution using a syringe under stirring at 150 rpm to form a hydrogel ball. The small ball is placed in the CaCl2 solution for 24 h, then filtered and washed with deionized water, then transferred to -80°C for freeze-drying for 24 h to obtain an aerogel ball composite material.

[0059] Example 3

[0060] Different from Example 1, in step (1), 2.9 g of polyethyleneimine (PEI) with a relative molecular mass of 10000 and a purity of 99% and 0.5 g of oxalic acid (OA) are weighed at room temperature, dissolved in 100 mL of ionized water, and stirred for 10 min until completely dissolved.

[0061] Example 4

[0062] Different from Example 1, in step (3), 2.0 g of N-acetyl-L-cysteine (NAC) is added to the solution of (2) after 1 h, mechanically stirred at 500 rpm until completely dissolved, then the pH is adjusted to 5.0 with 1 mol / L NaOH solution, and the mixed solution is stirred at room temperature for 2 h.

[0063] Comparative Example 1

[0064] (1) At room temperature, 2.9 g of polyethyleneimine (PEI) with a relative molecular mass of 10000 and a purity of 99% and 0.5 g of citric acid (CA) are weighed, dissolved in 100 mL of ionized water, and stirred for 10 min until completely dissolved, then a hydrothermal reaction is performed, the heating temperature is 180°C, and the reaction time is about 24 h to obtain a crude carbon quantum dot product, which is placed in a dialysis bag with a molecular weight cut-off of 500 Da for about 3 days to sufficiently remove unreacted molecular precursors to obtain a purified carbon quantum dot solution (CDs).

[0065] (2) At room temperature, 1.0 g of sodium alginate (SA) is weighed into 50 mL of deionized water, mechanically stirred at 800 rpm until completely dissolved, then 10 mL of the CDs solution of (1) is added and stirred until uniform; 1.0 g of activated agent 1-ethyl-carbonyldiimidazole hydrochloride (EDC-HCl) and 1.2 g of N-hydroxysuccinimide (NHS) are added to the SA solution to activate the carboxyl groups of SA under stirring.

[0066] (3) After 1 h, 2.0 g of L-cysteine hydrochloride monohydrate (L-cys) was added to the solution in (2) above, and mechanical stirring was performed at 500 rpm until complete dissolution. Then, 1 mol / L NaOH solution was used to adjust the pH to 5.0, and stirring was performed for 2 h. Then, the product was placed in a dialysis bag with a molecular weight cut-off of 500 Da, and dialysis was performed for about 2 days to sufficiently remove unreacted molecular precursors, thereby obtaining a thiol-modified sodium alginate solution (TA). Then, the TA was freeze-dried at -80°C for 48 h.

[0067] (4) Under stirring at 600 rpm, 2.0 g of the TA freeze-dried in (3) was dissolved in 100 mL of deionized water, and 2.0 g of CaCO3 and 0.5 g of gluconolactone were added to the mixed solution. After rapid stirring to obtain uniformity, the solution was poured into a silica gel mold with a diameter of 1.13 cm, and then the mold was placed in a -80°C freezer for 24 h to obtain an aerogel ball composite material.

[0068] Comparative Example 2

[0069] (1) At room temperature, 2.9 g of polyethyleneimine (PEI) with a relative molecular mass of 10,000 and a purity of 99% and 0.5 g of citric acid (CA) were weighed and dissolved in 100 mL of ionized water. After stirring for 10 min until complete dissolution, a hydrothermal reaction was performed at a heating temperature of 180°C for about 24 h to obtain a crude carbon quantum dot product. The product was placed in a dialysis bag with a molecular weight cut-off of 500 Da, and dialysis was performed for about 3 days to sufficiently remove unreacted molecular precursors, thereby obtaining a purified carbon quantum dot solution (CDs).

[0070] (2) At room temperature, 1.0 g of sodium alginate (SA) was weighed into 50 mL of deionized water, and mechanical stirring was performed at 800 rpm until complete dissolution. Then, 1.0 g of activated agent 1-ethyl-carbonyldiimidazole hydrochloride (EDC-HCl) and 1.2 g of N-hydroxysuccinimide (NHS) were added to the SA solution to activate the carboxyl groups of SA under stirring.

[0071] (3) After 1 h, 2.0 g of L-cysteine hydrochloride monohydrate (L-cys) was added to the solution in (2) above, and mechanical stirring was performed at 500 rpm until complete dissolution. Then, 1 mol / L NaOH solution was used to adjust the pH to 5.0, and stirring was performed for 2 h. Then, the product was placed in a dialysis bag with a molecular weight cut-off of 500 Da, and dialysis was performed for about 2 days to sufficiently remove unreacted molecular precursors, thereby obtaining a thiol-modified sodium alginate solution (TA). Then, the TA was freeze-dried at -80°C for 48 h.

[0072] (4) Under the condition of stirring at 600 rpm, 2.0 g of TA that had been freeze-dried in (6) was dissolved in 100 mL of deionized water, 2.0 g of CaCO3 and 0.5 g of gluconolactone were added after 3 h, and poured into a silica gel mold with a diameter of 1.13 cm to form a gel.

[0073] (5) The hydrogel ball in (4) was soaked in the 10% amino-modified carbon quantum dot solution in (1) (a solution formed by adding 10 mL of amino-modified carbon quantum dots to 90 mL of water) for 24 h, washed with deionized water after filtration, and then transferred to -80°C for freeze-drying for 24 h to obtain an aerogel ball composite material.

[0074] Comparative Example 3

[0075] Unlike Example 1, in step (4), 2.0 g of TA that had been freeze-dried in (3) was dissolved in 95 mL of deionized water under the condition of stirring at 400 rpm, and 5 mL of the CDs solution in (1) was added after 3 h.

[0076] Comparative Example 4

[0077] Unlike Example 1, in step (4), 2.0 g of TA that had been freeze-dried in (3) was dissolved in 80 mL of deionized water under the condition of stirring at 400 rpm, and 20 mL of the CDs solution in (1) was added after 3 h.

[0078] Comparative Example 5

[0079] Unlike Example 1, in step (4), 0.5 g of TA that had been freeze-dried in (3) was dissolved in 90 mL of deionized water under the condition of stirring at 400 rpm, and 10 mL of the CDs solution in (1) was added after 3 h.

[0080] Comparative Example 6

[0081] Unlike Example 1, in step (4), 3.0 g of TA that had been freeze-dried in (3) was dissolved in 90 mL of deionized water under the condition of stirring at 400 rpm, and 10 mL of the CDs solution in (1) was added after 3 h.

[0082] Comparative Example 7

[0083] (1) At room temperature, 2.9 g of polyethyleneimine (PEI) with a relative molecular mass of 10,000 and a purity of 99% and 0.5 g of citric acid (CA) were weighed and dissolved in 100 mL of ionized water, stirred for 10 min until they were completely dissolved, and then subjected to a hydrothermal reaction with a heating temperature of 180°C and a reaction time of about 24 h to obtain a carbon quantum dot crude product. The product was placed in a dialysis bag with a molecular weight cut-off of 500 Da and continuously dialyzed for about 3 days to sufficiently remove unreacted molecular precursors, thereby obtaining a purified carbon quantum dot solution (CDs).

[0084] (2) At room temperature, 2.0 g of sodium alginate (SA) was weighed into 90 mL of deionized water, and mechanically stirred at 800 rpm until completely dissolved, and then 10 mL of the CDs solution of (1) was added.

[0085] (3) 2.0 g of CaCO3 was weighed and added to the mixed solution of (2), stirred uniformly, and then 0.5 g of gluconolactone was added. After being stirred uniformly at 800 rpm, it was poured into a silica gel mold with a diameter of 1.13 cm, and then placed to form, and then transferred to -80°C for freeze-drying for 24 h to obtain a CDs / SA-gel composite material.

[0086] Comparative Example 8

[0087] Different from Comparative Example 7, in step (2), 2.0 g of carboxymethyl chitosan (CMCS) was weighed into 90 mL of deionized water, and mechanically stirred at 800 rpm until completely dissolved, and then 10 mL of the CDs solution of (1) was added. Finally, a CDs / CMCS-gel composite material was obtained.

[0088] Comparative Example 9

[0089] (1) At room temperature, 1.0 g of sodium alginate (SA) was weighed into 50 mL of deionized water, and mechanically stirred at 800 rpm until completely dissolved; 1.0 g of activated agent 1-ethyl-carbonyldiimidazole hydrochloride (EDC-HCl) and 1.2 g of N-hydroxysuccinimide (NHS) were added to the SA solution, and the carboxyl group of SA was activated under stirring.

[0090] (2) After 1 h, 2.0 g of L-cysteine hydrochloride monohydrate (L-cys) was added to the solution of (2) above, and mechanically stirred at 500 rpm until completely dissolved. Then, the pH was adjusted to 5.0 with 1 mol / L NaOH solution, and stirred for 2 h. Then, the product was placed in a dialysis bag with a molecular weight cut-off of 500 Da, and continuously dialyzed for about 2 days to sufficiently remove unreacted molecular precursors, to obtain a thiol-modified sodium alginate solution (TA). Then, the TA was freeze-dried at -80°C for 48 h.

[0091] (3) Under the condition of stirring at 600 rpm, 2.0 g of TA freeze-dried in (2) was dissolved in 100 mL of deionized water, and after 3 h, 2.0 g of CaCO3 and 0.5 g of gluconolactone were added. Then, it was poured into a silica gel mold with a diameter of 1.13 cm, and then placed to form, and then transferred to -80°C for freeze-drying for 24 h to obtain a TA-gel composite material.

[0092] Test Example 1

[0093] A small amount of raw material SA and modified TA in Example 1 were ground into powder respectively, and potassium bromide was pressed into tablets for infrared detection, and the infrared spectra of SA and TA were obtained Figure 1 :

[0094] In the SA spectrum, a wide absorption peak of -OH stretching vibration appeared near 3419 cm -1 , the peaks at 1614 cm -1 and 1417 cm -1 corresponded to the asymmetric and symmetric stretching vibrations of -COO-, and the peaks at 1031 cm -1 and 1085 cm -1 corresponded to the symmetric stretching vibrations of C-O(C-O-C).

[0095] In the TA spectrum, a new weak characteristic peak appeared at 2543 cm -1 , which was the stretching vibration peak of -SH (mercapto) thiol, indicating that -SH was derived from L-cys. In addition, due to the grafting of L-cys to SA, the peaks of -COO- shifted to 1647 cm -1 and 1398 cm -1 . At the same time, three new peaks at 1244 cm -1 , 1510 cm -1 , and 1573 cm -1 were observed, which were due to the bending and stretching vibrations of the CH2 group, the bending vibration of the amide group N-H bond of L-cys, and the stretching vibration of L-cys, respectively. The above analysis showed that L-cysteine hydrochloride monohydrate was successfully grafted onto SA.

[0096] Test Example 2

[0097] The water absorption rate of the composite material was determined by natural filtration method. 0.5 g of the composite material of Examples 1-4 and Comparative Examples 1, 2, 3, 4, 5, 6, 7, 8, and 9 was taken and placed in a beaker containing 400 mL of deionized water. The beaker was placed at room temperature until the adsorption equilibrium was reached. Then, the beads in the beaker were taken out and weighed to obtain the mass of the saturated water-absorbing beads. The water absorption rate was calculated, and the results are shown in Table 1. Figure 2

[0098] The water absorption rate of the composite material of Example 1 was significantly higher than that of Example 2, indicating that the use of calcium carbonate with gluconic acid lactone for slow release of Ca 2+ was more effective, and the use of calcium chloride would result in a too dense surface structure of the composite material, uneven chelation of calcium ions, and poor water absorption.

[0099] There was no significant difference in the water absorption rate between the composite materials of Example 1 and Examples 3 and 4, indicating that the use of different organic acids or mercapto donor reagents had no significant effect on the water absorption of the composite material. ​

[0100] The water absorption rate of Example 1 has no obvious difference with Comparative Examples 3 and 4, and the addition amount of CDs does not affect the water absorption rate of the material.

[0101] Comparing the water absorption rates of the composite materials of Example 1 and Comparative Examples 1 and 2 respectively, it is shown that different addition sequences of carbon quantum dots will cause changes in the structure of the composite material, thereby leading to a decrease in water absorption effect.

[0102] Comparing the water absorption rates of the composite materials of Example 1 and Comparative Examples 5, 6, 7 and 8 respectively, the water absorption rate of the composite material of Example 1 is 1487%, and the water absorption rates of the composite materials of Comparative Examples 5, 6, 7 and 8 are 682%, 848%, 1183% and 1210% respectively, which shows that the water absorption of the alginate composite material and the carboxymethyl chitosan composite material is lower than that of the modified alginate composite material; the addition of a proper amount of modified alginate can affect the structure of the composite material, increase the porosity and improve the water absorption rate.

[0103] Test Example 3

[0104] The maximum adsorption capacity is a key indicator for evaluating the adsorption performance of a material. 0.2 g of dried composite gel was added to a Cu 2+ , Pb 2+ ion solution with pH 5.5, concentration 50 mg / L and volume 100 mL, and the solution was shaken at 25°C and 150 rpm for 24 h to ensure adsorption equilibrium. The residual metal ion concentration in the solution was determined by atomic absorption spectrometry (AAS), and all experiments were performed in triplicate. The adsorption capacity of each gram of adsorbent was calculated using the following formula:

[0105]

[0106] In the formula, Q e is the equilibrium metal ion adsorption capacity of the aerogel (mg / g), C0 and C e are the initial and final concentrations of the metal solution (mg / L) respectively, V (L) represents the solution volume, and m (g) is the mass of the added adsorbent. The results are shown in Table 1: Figure 3

[0107] Comparing the adsorption effects of the composite materials of Example 1 and Examples 3 and 4 respectively, which use different organic acids to synthesize carbon dots or use different thiol donor reagents, although this operation has no significant effect on the water absorption rate of the composite material, the use of citric acid and L-cysteine hydrochloride monohydrate is more conducive to the adsorption of Cu 2+ , Pb 2+ by the composite material.

[0108] ​Example 1 and Comparative Examples 3, 4, 5, 6, 9 are compared with respect to the adsorption effect of different amounts of CDs and dry TA, which shows that the amount of CDs and TA needs to be controlled within a reasonable range to ensure the adsorption effect of the material, and the addition of CDs can promote the adsorption of TA-gel composite material to heavy metals.

[0109] Example 1 and Comparative Examples 7, 8 are compared with respect to the adsorption effect of composite materials CDs / TA-gel, CDs / SA-gel and CDs / CMCS-gel, respectively. The adsorption amount of Example 1 composite material CDs / TA-gel to copper and lead is 187.60 mg / g and 193.52 mg / g, respectively, the adsorption amount of CDs / SA-gel to copper and lead is 60.12 mg / g and 61.45 mg / g, respectively, and the adsorption amount of CDs / CMCS-gel to copper and lead is 44.45 mg / g and 46.35 mg / g, respectively, which shows that loading CDs on modified alginate can achieve more excellent adsorption effect.

[0110] Test Example 4

[0111] In order to study the selectivity of the composite material to different metal ions, the fluorescence intensity of the composite material CDs / TA-gel in different metal ion solutions was determined, and the results are shown in Figure 4

[0112] The CDs / TA-gel beads showed strong fluorescence intensity in the blank solution CK.

[0113] The CDs / TA-gel beads were put into 25 μmol / L Cu 2+ solution, and the fluorescence intensity of the beads at 355 nm was measured after 5 min of equilibrium. The results show that the fluorescence intensity decreased significantly, with a quenching degree of 38.3%, and the fluorescence was in the "off" state.

[0114] The CDs / TA-gel beads were put into 25 μmol / L Pb 2+ solution, and the fluorescence intensity at 355 nm increased, and the fluorescence was in the "on" state.

[0115] The CDs / TA-gel beads were put into 50 μmol / L Na + , Li + , Zn 2+ , Mn 2+ , Mg 2+ , K + , Fe 3+ , Ca 2+ solution, respectively, and the fluorescence intensity did not change significantly; and the addition of Ni 2+ , Cr 3+ and Cd​2+ The fluorescence intensity of the solution decreased slightly, but the quenching degree was less than 5.7%.

[0116] As shown above, the CDs / TA-gel beads have good selectivity for Cu 2+ , Pb 2+ in the fluorescence selective detection.

[0117] Test Example 5

[0118] In order to study the fluorescence response of CDs solution and CDs-loaded composite materials to Cu 2+ , Pb 2+ , the CDs solution, the composite material CDs / TA-gel, and the composite material CDs / CMCS-gel in Example 1 were respectively used to adsorb Cu 2 + , Pb 2+ solutions with different concentrations, and then the fluorescence changes were compared under a 365 nm ultraviolet lamp, and the results are shown in Figure 5

[0119] Compared with the composite material CDs / TA-gel, the amount of CDs solution used is more under the same conditions, and the fluorescence intensity change of CDs direct detection is smaller and the response to heavy metal ions is lower as the concentration of Cu 2+ or Pb 2+ increases.

[0120] When the concentration of heavy metals is 0 μM, the fluorescence of the composite material CDs / CMCS-gel is significantly smaller than that of the CDs solution and the composite material CDs / TA-gel, indicating that loading CDs on CMCS will weaken the fluorescence intensity of CDs.

[0121] After the composite material CDs / TA-gel adsorbed Cu 2+ and Pb 2+ with different concentrations, it respectively showed the phenomenon of gradually weakened fluorescence and gradually enhanced fluorescence, which was more obvious than the fluorescence response observed using CDs and the composite material CDs / CMCS-gel.

[0122] As shown above, the composite material CDs / TA-gel formed by loading CDs on the modified alginate is more conducive to the rapid aggregation of Cu 2 + , Pb 2+ , and has good fluorescence response to Cu 2+ , Pb 2+ .

[0123] Test Example 6

[0124] ​To further investigate the effect of the composite material CDs / TA-gel on Cu 2+ Pb 2+ The detection capability was assessed using the composite material CDs / TA-gel from Example 1 at different concentrations of Cu. 2+ Pb 2+ The fluorescence experiment was conducted, and the results are as follows: Figure 6 As shown:

[0125] The fluorescence intensity of CDs / TA-gel at 355 nm increased with Cu 2+ The concentration (0–50 μmol / L) gradually decreases with increasing concentration. Figure 6 a) Fluorescence intensity and Cu 2+ linear correlation coefficient of concentration (R) 2 ) is 0.9980 ( Figure 6 b) Cu can be obtained through calculation. 2+ The detection limit is 1.725 μmol / L.

[0126] The fluorescence intensity of CDs / TA-gel at 355 nm increased with Pb 2+ The effect gradually increases with increasing concentration (0–50 μmol / L). Figure 6 c) Fluorescence intensity and Pb 2+ linear correlation coefficient of concentration (R) 2 The value is 0.9975. Figure 6 d) Pb can be obtained through calculation. 2+ The detection limit is 1.495 μmol / L.

[0127] In summary, the fluorescence detection based on the CDs / TA-gel composite material exhibits good sensitivity. Therefore, the material proposed in this invention can be effectively used for Cu... 2+ Pb 2+ Quantitative analysis and selective detection.

[0128] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a heavy metal detection-adsorption integrated composite material, characterized in that, Comprising the following steps: Under stirring, the thiol-modified alginate is dissolved in water, the amino-modified carbon quantum dot solution is added to dope and cross-link to obtain a mixed solution, calcium carbonate is added, and after stirring uniformly, it is placed to form, and then freeze-dried to obtain a heavy metal detection-adsorption integrated composite material; The mass-volume ratio of the thiol-modified alginate to the amino-modified carbon quantum dot solution is 2g:10mL; the volume concentration of the amino-modified carbon quantum dot solution in the mixed solution is 5-15%; The amino-modified carbon quantum dot solution is prepared by hydrothermal reaction of a carbon source, a nitrogen source and water, and the mass-volume ratio is (0.1-0.5)g:(0.6-3)g:(20-100)mL; the carbon source is at least one of citric acid, malic acid, tartaric acid and oxalic acid; and the nitrogen source is at least one of polyethyleneimine, urea and melamine; The thiol-modified alginate is obtained by grafting alginate with a thiol donor reagent; The grafting step is: under stirring, a catalyst is added to an alginate aqueous solution, then a thiol donor reagent is added, the pH of the mixed solution is adjusted, and after sufficient reaction, the product is purified by dialysis, and then freeze-dried to obtain the thiol-modified alginate; The thiol donor reagent is at least one of L-cysteine hydrochloride monohydrate and N-acetyl-L-cysteine; and the catalyst is a carbodiimide activator.

2. The preparation method of the integrated heavy metal detection-adsorption composite material according to claim 1, characterized in that, The hydrothermal reaction is heating at 150-200℃ for 12-24h, and after the hydrothermal reaction, the product is purified by dialysis, the dialysis molecular weight cut-off is 500-3000Da, and the dialysis time is 2-3d to obtain the amino-modified carbon quantum dot solution.

3. The method according to claim 1, wherein the method is characterized by, The alginate is at least one of sodium alginate, potassium alginate and ammonium alginate.

4. The method of claim 1, wherein the method further comprises the step of: 4-1) adding a heavy metal adsorbent to the mixture of step 3-1) to prepare a heavy metal detection-adsorption integrated composite material. The alginate aqueous solution is prepared by mixing alginate and water in a mass-volume ratio of (0.5-4)g:(10-100)mL; The mass-volume ratio of the thiol donor reagent to the alginate aqueous solution is (0.5-5)g:(4-120)mL; The dialysis molecular weight cut-off is 500-8000Da, and the dialysis time is 1-2d.

5. The method of claim 1, wherein the method further comprises the step of: 5-1) mixing the heavy metal detection material and the heavy metal adsorption material to prepare the heavy metal detection-adsorption integrated composite material. The carbodiimide activator is at least one of dicyclohexyl carbodiimide, diisopropyl carbodiimide and 1-ethyl-carbonyldiimidazole hydrochloride, and N-hydroxysuccinimide or N-hydroxylthiosuccinimide is added.

6. A heavy metal detecting-adsorbing integrated composite material, characterized in that, Prepared by the preparation method of any one of claims 1-5.

7. The heavy metal detection-adsorption integrated composite material of claim 6 for use in the field of heavy metal detection and / or adsorption.

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