A method for adsorbing heavy metal copper

Abstract

The scheme discloses a heavy metal copper adsorption method in the technical field of heavy metal adsorption, which comprises the following steps: using a modified adsorbent to adsorb heavy metal copper; and the preparation of the modified adsorbent comprises the following steps: alkalinization, oxidation, modification, crosslinking and exchange of distiller's grains to increase groups. The modified adsorbent prepared by the method has the advantages of high adsorption capacity, high adsorption efficiency and strong reusability.

Description

Technical Field

[0001] This invention relates to the field of heavy metal adsorption technology, and in particular to a method for adsorbing heavy metal copper. Background Technology

[0002] my country is a major producer and consumer of baijiu (Chinese liquor), and distiller's grains are a major byproduct of baijiu production. As a byproduct of baijiu production, distiller's grains are characterized by high acidity, high moisture content, strong viscosity, susceptibility to mold, and difficulty in storage. If not treated and utilized in a timely manner, they will not only cause serious pollution to soil, water, and air, but also damage the ecological environment of brewing microorganisms, directly affecting the sustainable development of the baijiu industry. In addition to high levels of starch, protein, cellulose, and fat, distiller's grains also contain abundant phosphorus, potassium, vitamins, and amino acids, among other conventional nutrients. Currently, the comprehensive utilization of distiller's grains has expanded to various fields, including the production of animal feed, organic fertilizer, edible fungi culture medium, hydroponics substrate for plants, pharmaceuticals and biomass energy, brewing soy sauce and vinegar, and extracting umami enhancers.

[0003] The rapid development of industry and agriculture has brought about a worsening problem of heavy metal pollution in water systems. The development of industry and agriculture has resulted in a huge amount of wastewater discharge, including copper ions. Direct discharge into the aquatic environment causes irreversible pollution on Earth and can also cause abnormal hematopoietic function in the human body, leading to diseases such as jaundice, liver necrosis, and gastric ulcers.

[0004] To address the environmental problem of heavy metal pollution, chemical precipitation, ion exchange, and adsorption methods are used to treat heavy metal ions in water. Adsorption, a common industrial application, utilizes specialized materials, such as porous materials, to bind certain pollutants together, thereby achieving purification. This method not only improves purification efficiency but also reduces adverse impacts on the environment and human health. Typically, adsorbents can be activated carbon, minerals, or bio-based elements.

[0005] To more accurately classify them, adsorption methods can also be divided into physical and chemical methods. Chemisorption involves linking atoms in a molecule in a certain way, enabling it to capture the molecule's energy. Physical adsorption, on the other hand, relies on the properties of the atoms in the molecule and the molecule itself to achieve this linking. However, when using these methods to treat heavy metal pollutants, their performance is often insufficient to completely resist pollution.

[0006] To more accurately assess the adsorption performance of heavy metal ions, it is necessary to explore their kinetic characteristics and thermodynamic behavior in depth. Therefore, this paper proposes a method that combines the adsorption of heavy metal copper with distillers' grains to better achieve the adsorption of heavy metal copper and reduce the pollution of heavy metal copper to the environment. Summary of the Invention

[0007] The present invention aims to provide a method for adsorbing heavy metal copper, specifically a method that combines distiller's grains to achieve heavy metal copper adsorption, thereby reducing the environmental pollution caused by heavy metal copper.

[0008] One method for adsorbing heavy metal copper in this scheme includes using a modified adsorbent to adsorb heavy metal copper; the preparation of the modified adsorbent includes: Step 1: Alkalization of distiller's grains: Take 200-300g of distiller's grains powder, prepare 1-1.5L of 0.1-0.2mol / L NaOH solution and add it to the distiller's grains powder, adjust the pH of the alkalization solution to 7, centrifuge, and then dry the centrifuged sediment in a constant temperature electric heating drying oven at 45-50℃, and grind the dried distiller's grains into powder using a mortar and pestle;

[0009] Step 2: Oxidation of distiller's grains: Take 8-10g of alkalized distiller's grains and 40-50ml of distilled water, and stir at 45-50℃ for 1-1.5h to obtain an alkalized distiller's grains solution. Take 5-10g of sodium periodate and add it to 400-60ml of distilled water to prepare a sodium periodate solution. Add the sodium periodate solution dropwise to the alkalized distiller's grains solution and stir for 15-25min. Then add hydrochloric acid to adjust the pH to 4 and react for 24-28h. Then add 5-10ml of ethylene glycol and wash the residue after filtration with 50-100ml of anhydrous ethanol to obtain oxidized distiller's grains.

[0010] Step 3: Modification of distiller's grains: Take 2-5g of oxidized distiller's grains and add 30-50ml of anhydrous ethanol and stir for 2-3h. Then add 2-3g of salicylhydrazine and add glacial acetic acid as a catalyst. Stir at 45-50℃ for 24-36h. Then filter and air dry to obtain modified distiller's grains.

[0011] Step 4: Crosslinking of distiller's grains: Add 0.5-0.8g of sodium alginate to 100-150ml of distilled water, then add 2-3g of modified distiller's grains and stir thoroughly. Then add 1-2mL of 1,4-butanediol diglycidyl ether (BDE) crosslinking agent and stir for 12-15 hours.

[0012] Step 5: Adding groups by exchanging lees: The cross-linked material is added to a 3-5% calcium chloride solution and stirred for 12-24 hours. After freezing and vacuum drying, the modified adsorbent of lees is obtained. Then, the cross-linked material of acylhydrazone-crosslinked sodium alginate is prepared by vacuum freeze drying.

[0013] The working principle and beneficial effects of this scheme are as follows: Modified adsorbents are used to adsorb Cu. 2+ The effect of modified distiller's grains adsorbent on Cu was studied using the controlled variable method, focusing on factors such as temperature and copper ion concentration. 2+ The optimal reaction conditions were determined, with pH = 7, and the optimal adsorption time for the solution was identified as 360 min. This was particularly relevant for Cu. 2+The removal rate was as high as 73.52%, and the prepared modified distiller's grains adsorbent showed good removal efficiency for Cu. 2+ It has a large adsorption capacity, even in trace amounts of heavy metal Cu. 2+ The removal rate of LODG is remarkable, exceeding 90%, thus enabling its application in the treatment of heavy metal Cu in aquatic environments. 2+ It's a great choice.

[0014] Furthermore, in step 2, the alkalized distiller's grains and anhydrous ethanol are stirred in a light-protected environment, and the sodium periodate solution is prepared in a light-protected environment.

[0015] Furthermore, the constant temperature stirring uses a constant temperature magnetic stirrer.

[0016] Furthermore, after adding hydrochloric acid to adjust the pH in S2, the pH should be maintained at 4.0 during the constant temperature stirring process.

[0017] Furthermore, in step S5, the freezing time is 12–24 hours, and the vacuum drying is performed using a vacuum dryer for 24–48 hours. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating the preparation process of a modified adsorbent based on distiller's grains in this invention.

[0019] Figure 2 For DG(a), ODG(b), LODG(c), LODG adsorption of Cu 2+ (d) Infrared spectrum;

[0020] Figure 3 For DG(a), ODG(b), LODG(c), LODG adsorption of Cu 2+ (d)Cu 2+ SEM images of the surface microporous structure before and after the reaction;

[0021] Figure 4 The EDAX spectrum of LODG;

[0022] Figure 5 LODG adsorption of Cu 2+ EDAX spectrum;

[0023] Figure 6 The effect of adsorption time on adsorption performance;

[0024] Figure 7 LODG adsorption of Cu 2+ Fitting curves for the pseudo-first-order dynamic equation and the pseudo-second-order dynamic equation;

[0025] Figure 8 (a) Isoelectric point testing, (b) analysis of the effect of different pH values ​​on adsorption;

[0026] Figure 9 To adsorb Cu from modified distiller's grains adsorbent 2+ Adsorption-desorption;

[0027] Figure 10 Cu at different temperatures 2+ Thermodynamics;

[0028] Figure 11 Thermogravimetric analysis (TGA) diagram of the functionalized adsorbent from distiller's grains. Detailed Implementation

[0029] The following detailed explanation illustrates the specific implementation methods:

[0030] Example: A method for adsorbing heavy metal copper, comprising using a modified adsorbent to adsorb heavy metal copper;

[0031] The preparation of the modified adsorbent includes: Step 1: Distillers' grains alkalization (DG): Take 200-300g of distillers' grains powder, prepare 1-1.5L of 0.1-0.2mol / L NaOH solution and add it to the distillers' grains powder. Adjust the pH of the alkalization solution to 7, centrifuge it, and then dry the centrifuged precipitate in a constant temperature electric heating drying oven at 45-50℃. Grind the dried distillers' grains into powder using a mortar and pestle.

[0032] Step 2: Oxidation of distiller's grains (ODG): Take 8-10g of alkalized distiller's grains and 40-50ml of distilled water, and stir at 45-50℃ for 1-1.5h to obtain an alkalized distiller's grains solution. Take 5-10g of sodium periodate and add it to 400-60ml of distilled water to prepare a sodium periodate solution. Add the sodium periodate solution dropwise to the alkalized distiller's grains solution and stir for 15-25min. Then add hydrochloric acid to adjust the pH to 4 and react for 24-28h. Then add 5-10ml of ethylene glycol and wash the residue after filtration with 50-100ml of anhydrous ethanol to obtain oxidized distiller's grains.

[0033] Step 3: Modification of distiller's grains: Take 2-5g of oxidized distiller's grains and add 30-50ml of anhydrous ethanol and stir for 2-3h. Then add 2-3g of salicylhydrazine and add glacial acetic acid as a catalyst. Stir at 45-50℃ for 24-36h. Then filter and air dry to obtain modified distiller's grains.

[0034] Step 4: Crosslinking of distiller's grains: Add 0.5-0.8g of sodium alginate to 100-150ml of distilled water, then add 2-3g of modified distiller's grains and stir thoroughly. Then add 1-2mL of 1,4-butanediol diglycidyl ether (BDE) crosslinking agent and stir for 12-15 hours.

[0035] Step 5: Adding Groups (LODG) by Exchange of Distillers' Grains: The cross-linked material is added to a 3-5% calcium chloride solution and stirred for 12-24 hours. After freezing and vacuum drying, the modified adsorbent of distillers' grains is obtained. Then, the cross-linked material of acylhydrazone-crosslinked sodium alginate is prepared by vacuum freeze drying.

[0036] Experiment: FT-IR can be used to understand the functional groups of substances. FT-IR of DG, ODG, LODG, and LODG adsorbing Cu. From the FT-IR of LODG, it can be inferred that 3269.26 cm⁻¹ is likely the characteristic peak of the intramolecular association of hydroxyl groups on the LODG chain; the double peak at 1731 cm⁻¹ is the characteristic peak of the dialdehyde group introduced by NaIO₄; 1722 cm⁻¹ may be the stretching vibration peak of the carbonyl group on the salicylhydrazine group; and 1598.69 cm⁻¹ is the stretching vibration peak of LODG after the successful synthesis of a new functional group, acylhydrazone, through aldehyde-amine condensation. Figure 2 Similarly, amino groups have been successfully introduced into the LODG system.

[0037] By detecting LODG adsorbed Cu 2+ Elemental composition of SEM images before and after. Cu 2+ SEM images of the surface microporous structure before and after the reaction are as follows: Figure 3 As shown, the surface of DG (distillers' grains) is smooth, with large and uneven pores on the sides. After oxidation with sodium periodate, the ODG is no longer a large particle but is broken down into small, fragmented substances. Further modification with salicylhydrazone of LODG results in a rougher surface, exhibiting a sponge-like porous structure and increased specific surface area. LODG is then used to adsorb Cu. 2+ Afterwards, its surface microporous structure presents a mesh-like structure with a rough surface, as well as some relatively large pores and clearly more than two layers of interlaced upper and lower structures, achieving a very good adsorption effect.

[0038] EDAX analysis of LODG adsorption of Cu 2+ The element contained therein. Cu 2+ EDAX element spectrum as Figure 4 and Figure 5 As shown, in the elemental analysis results of EDAX, LODG ( Figure 3 c) contains four elements: carbon (C) at a relative molecular mass percentage of 37.88%, nitrogen (N) at 9.99%, oxygen (O) at 46.24%, and calcium (Ca) at 5.9%. Cu adsorption from LODG... 2+ The following image shows ( Figure 3 In section d), the number of element types changed, with the addition of Cu. 2+It transformed into C, N, O, Ca, and Cu, with the relative molecular mass percentages of C being 59.21%, N being 6.4%, O being 0.04%, and Cu being 2.14% (Table 1 below). EDAX analysis showed that Cu adsorbed from LODG to LODG... 2+ Subsequently, Ca2+ in the raw material LODG is converted to Cu. 2+ It was replaced. LODG adsorbs Cu 2+ Copper ions exchange for calcium ions, resulting in a significant reduction in calcium ion levels. Copper ions are present in EDAX, while calcium ion levels are almost zero. This indicates that LODG affects Cu... 2+ The reason it works so well is that the interaction between copper ions and calcium ions is achieved through ion exchange.

[0039] Table 1 DG, ODG, LODG, LODG-Cu 2+ EDAX spectral parameters

[0040]

[0041] The results are as follows Figure 6 As shown, Cu 2+ The adsorption on LODG began to change significantly within 150 minutes, affecting Cu. 2+ The equilibrium adsorption capacity reached 58.59%. Then the adsorption rate slowed down, and finally equilibrium was reached in 240 minutes.

[0042] Subsequently, pseudo-first-order kinetic model, pseudo-second-order kinetic model, and intraparticle diffusion model were fitted to investigate the adsorption kinetics of the functionalized adsorbent from distiller's grains. The fitted curves are shown below. Figure 7 As shown.

[0043] The formula for the pseudo-first-order dynamic model is as follows:

[0044] ln(q e -q t )=lnq e -K1t (3-1)

[0045] The formula for the pseudo-second-order dynamic model is as follows:

[0046]

[0047] Intraparticle diffusion model formula:

[0048] q t =0.5kid t +c i (3-3)

[0049] In the formula, and represent time t and adsorption amount, respectively, in mg / g; k2 represents pseudo-second-order constant, in mg / (mg·min); Ci is the boundary layer thickness, in (mg / g); k1 represents pseudo-first-order constant, in min-1.

[0050] Table 2 Parameters of LODG Adsorption Kinetic Model

[0051]

[0052]

[0053] Cu in the quasi-second-order model 2+ The correlation coefficient R² is 0.999, which is much higher than the R1 (Cu) of the quasi-first-order model. 2+ The quasi-first-order model is a physical adsorption process dominated by sponge-like adsorption, while the quasi-second-order model is dominated by chemical adsorption. This indicates that the adsorption process is mainly chemical adsorption.

[0054] LODG was tested and analyzed under pH conditions, such as... Figure 8 As shown in (a), the isoelectric point of LODG in pH solution is 2.7. When pH > 2.7, its absolute value increases. This is fundamentally because, with different pH levels in the solution, the carboxyl and hydroxyl functional groups in LODG undergo self-crosslinking reactions, leading to an increase in anions on the LODG surface and a stronger attraction to cationic groups. In summary, LODG's attraction to Cu... 2+ It has strong adsorption properties.

[0055] To verify the reasoning results, such as Figure 8 As shown in (b), with the increase of hydrogen ions in the solution, Cu 2+ The removal rate is significant, but the increase is slow when pH > 2. At around pH 7, Cu... 2+ The removal rate reached its peak at 73.52%. This phenomenon is due to the protonation of phosphonic acid groups and hydroxyl functional groups in LODG under conditions of low hydrogen ion content, highlighting their positively charged properties. 2+ Potentially similar to LODGs, they repel each other. As the hydrogen ion concentration increases, the deprotonation of some functional groups becomes significant, particularly in Cu. 2+ The presence of polymerization and enhanced charge attraction between Cu and LODG is beneficial. 2+ Adsorption.

[0056] like Figure 9 The used LODG is processed and then adsorbed with Cu again. 2+ The data is shown in the figure above. After 6 adsorption cycles of Cu 2+Then, Cu was desorbed after washing with HCl. 2+ After repeated utilization experiments, LODG on Cu 2+ The elution efficiency decreased from 90% to 67%, indicating that some useful functional groups were tightly bound to other substances. The elution efficiency also decreased from 86% to 63%, meaning that even strong acids could not destroy the functional sites, resulting in fewer and fewer usable functional sites. However, the prepared LODG showed a decrease in its effectiveness against Cu. 2+ It has a good reuse effect and is worth promoting in the production of treatment for trace amounts of heavy metal copper ions with few adsorption cycles.

[0057] Need to understand LODG adsorption of Cu 2+ The process is either an endothermic or exothermic reaction, and precise calculations are performed on the relevant thermodynamic coefficients. Based on this, it is analyzed that LODG can maintain high adsorption conditions.

[0058] The analysis results showed that the Gibbs free energy was always negative, proving that LODG adsorbs Cu. 2+ The process spontaneously involves an endothermic reaction. The removal rate is also high at high temperatures (as shown in Figure 10), presumably because the functional sites in LODG experience increased intermolecular collisions due to rising temperature, leading to more frequent reactions with LODG and a greater probability of binding to the active sites in LODG. Furthermore, at high temperatures, the smaller the Gibbs free energy, the larger its absolute value, which favors the endothermic reaction proceeding in the forward direction. The fact that ΔH > 0 indicates that the adsorption of copper ions is also an endothermic reaction, and the adsorption of Cu ions by LODG is similar. 2+ The fundamental reason why ΔS > 0 is that calcium ion exchange occurred in the solution.

[22] This results in a positive LODG entropy value, indicating that the adsorption process is entropy-driven. These results demonstrate that LODG adsorbs Cu. 2+ The process is a spontaneous process in which entropy increases and an endothermic reaction occurs.

[0059] Table 3. Cu adsorption at 25℃, 35℃, and 45℃ 2+ The correlation coefficient between the equilibrium adsorption amount and the thermodynamic curve

[0060]

[0061] The effect of LODG on Cu adsorption was analyzed. 2+ Thermal stability during the process (e.g.) Figure 11The relative molecular mass loss of LODG is significant at different temperatures. In stage one, when the temperature of the DG sample is increased to 200K and the LODG sample to 150K, the mass percentage decreases by approximately 4.788% and 8.361%, respectively. This is attributed to the evaporation of free water and crystalline water in the solution. In stage two, when the temperature is further increased to 450K and 250K, the mass percentages of DG and LODG decrease by 38.251% and 26.662%, respectively. This decrease is attributed to the occupation of functional group sites and tighter binding with other substances. In stage three, when the temperature is further increased to 425K, the mass percentage of LODG decreases by 49.289%, due to the carbonization of carbon chains in the DG structure. Comparison with the results for DG indicates that LODG has relatively strong thermal stability before 250K, suggesting that LODG is more suitable for reactions at low temperatures.

[0062] Adsorption is essentially the process by which adsorbates are held on a solid surface by physical forces (intermolecular forces, electrostatic attraction) and chemical forces (hydrogen bonds, covalent bonds, ligand exchange). The binding of adsorbates and adsorbents through intermolecular forces is generally called physical adsorption; binding through electrostatic attraction is generally called ion exchange adsorption, also known as outer-sphere complexes; adsorption through covalent bonds or ligand exchange is called coordination adsorption, also known as inner-sphere complexes. Among these, outer-sphere and inner-sphere coordination are the main types of adsorption at the solid-liquid interface.

[0063] According to coordination theory, Lewis bases, as Lewis bases, can produce a special coordination compound in which the core atom generates a special charge, thus enabling this theory to be effectively used to explain adsorption reactions.

[0064] According to the Hard and Soft Acids and Bases Theory, hard acids are characterized by a small positive charge and low polarizability, while soft acids are characterized by a large positive charge and high polarizability. Furthermore, hard bases are characterized by strong electronegativity, low polarizability, and are readily affected by oxygen, while soft bases are characterized by strong resistance to acids. Recent research suggests that a relatively stable structure exists between hard acid-hard base and soft acid-soft base pairs.

[0065] In this experiment, after a series of pretreatments of the distiller's grains, distiller's grains powder was obtained. Then, sodium periodate and salicylhydrazine were added to the distiller's grains powder and chemically combined, physically adsorbed, and condensed to prepare a functionalized modified distiller's grains adsorbent (LODG).

[0066] Furthermore, by controlling variables, the optimal reaction conditions of LODG for Cu2+ were studied, including temperature and copper ion concentration. The optimal adsorption time for the solution was determined to be 360 ​​min at pH 7. 2+ The removal rate reached 73.52%. Kinetic model analysis revealed that LODG's removal was primarily influenced by chemical adsorption, with physical adsorption also present. Analysis using SEM, EDAX, FT-IR, and mechanistic studies indicated that the acylhydrazone structure of LODG is due to ion adsorption, polymerization, and condensation adsorption of Cu. 2+ Cu 2+ It appears at various locations within the LODG material. Further thermodynamic analysis reveals that LODG adsorbs Cu. 2+ The process is endothermic, indicating that the reaction can proceed spontaneously. Thermogravimetric analysis shows that LODG is suitable for reaction at low temperatures below 250K, and its structure is relatively stable. Adsorption and desorption experiments show that after multiple cycles, the adsorption rate of LODG still reaches 67%. The combined experimental results indicate that the prepared LODG is effective against Cu... 2+ It has a large adsorption capacity, even in trace amounts of heavy metal Cu. 2+ The removal rate of LODG is remarkable, exceeding 90%, thus enabling its application in the treatment of heavy metal Cu in aquatic environments. 2+ It's a great choice.

[0067] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method of adsorbing heavy metal copper, characterized by: A method for adsorbing heavy metal copper, comprising using a modified adsorbent to adsorb heavy metal copper; the preparation of the modified adsorbent comprises: step 1: alkali treatment of distiller's grains: take 200-300g of distiller's grain powder, prepare 0.1-0.2mol / L NaOH solution 1-1.5L, add to the distiller's grain powder, adjust the alkali treatment liquid to pH 7, centrifugal treatment, then dry the distiller's grain precipitate in a constant temperature electric heating drying oven at 45-50℃, and grind the dried distiller's grain into powder with a mortar; Step 2: distiller's grain oxidation: take 8-10g of alkali treated distiller's grains and 40-50ml of anhydrous ethanol, then constant temperature stirring at 45-50℃ for 1-1.5h to obtain an alkali treated distiller's grain solution, take 5-10g of sodium periodate, add distilled water to prepare a sodium periodate solution, drop the sodium periodate solution into the alkali treated distiller's grain solution and stir for 15-25min, then add hydrochloric acid to adjust the pH to 4, react for 24-28h; then add 5-10ml of ethylene glycol, and use 50-100ml of anhydrous ethanol to wash the residue after filtration, to obtain oxidized distiller's grains; Step 3: distiller's grain modification: take 2-5g of oxidized distiller's grains, add 30-50ml of anhydrous ethanol and stir for 2-3h, then add 2-3g of salicylic hydrazide, drop in ice acetic acid as catalyst, stir at 45-50℃ for 24-36h, then filter and air dry to obtain modified distiller's grains; Step 4: distiller's grain crosslinking: add 0.5-0.8g of sodium alginate to 100-150ml of distilled water, then add 2-3g of modified distiller's grains and stir well, then drop in 1-2ml of 1,4-butanediol diglycidyl ether crosslinking agent and stir for 12-15h to obtain a crosslinked product; Step 5: distiller's grain exchange to increase groups: add the crosslinked product to a 3-5% calcium chloride solution and stir for 12-24h, then freeze and vacuum dry to obtain a modified distiller's grain adsorbent, then vacuum freeze dry to prepare the crosslinked product of acylhydrazone crosslinked sodium alginate.

2. The method of claim 1, wherein: In step 2, the alkali treated distiller's grains and anhydrous ethanol are stirred in a light-proof environment, and the sodium periodate solution is prepared in a light-proof environment.

3. The method of claim 2, wherein the method is characterized by: In step 2, constant temperature stirring is performed using a constant temperature magnetic stirrer.

4. The method of claim 3, wherein the method is characterized by: In step 5, the freezing time is 12-24h, vacuum drying is performed using a vacuum dryer, and the vacuum drying time is 24-48h.

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