Preparation method of high-salt environment lead adsorption activated carbon

Abstract

The application belongs to the technical field of modified activated carbon preparation, and discloses a preparation method of activated carbon for lead adsorption in high-salt environment. 2+ Still have a certain adsorption performance of activated carbon material. In the modified reagent selected in the experiment, tannic acid is a food-grade acid modifier, which presents very good safety at normal temperature, and triethanolamine is also a stabilizer commonly used in chemical experiments, which is very safe. Therefore, the raw materials used in the entire modification experiment design are safe reagents, which are safer than the commonly used modification reagents of activated carbon. The activated carbon is modified at 80 DEG C water bath environment, and the composite modification effect is best after 2wt%+2vt% composite modification. The adsorption capacity K value after modification reaches 14.724 mg / g, which has practical application value.

Description

Technical Field

[0001] This invention relates to the field of modified activated carbon preparation technology, specifically to a method for preparing lead-adsorbing activated carbon for high-salt environments. Background Technology

[0002] With societal development, particularly the research and development of galvanizing, zinc alloy die-casting, and zinc batteries in the automotive and new energy storage sectors, the mining and extraction of zinc ore has increased year by year. As a major associated mineral in zinc mining, galena (lead ore) generates wastewater containing high levels of the heavy metal lead. Direct discharge of this wastewater without proper treatment will directly threaten aquatic and soil ecosystems. Furthermore, heavy metals are highly difficult to degrade, easily accumulating in organisms and ultimately impacting human health through the food chain. Therefore, research on lead adsorption in zinc mine wastewater can provide strong support for the development of the national automotive and new energy storage sectors.

[0003] Currently, the main technologies for treating heavy metal wastewater include electrochemical treatment, irradiation treatment, membrane separation technology, and adsorption. Among these, adsorption is simple to operate, has low treatment costs, and can handle large volumes, making it uniquely advantageous for treating high-concentration wastewater such as mining wastewater. Activated carbon (AC) adsorbents have high biocompatibility and low cost, making them a primary research focus for wastewater adsorbents. Under typical wastewater conditions, AC-Pb... 2+ The adsorption performance is also quite ideal. However, some zinc mines contain rock salt, mine fluids, and seepage fluids, which can result in high salt concentrations in the wastewater. Na + Even reaching C Pb 2+ Hundreds of times greater. Ordinary activated carbon adsorbs metals primarily through physical adsorption of metal ions via its abundant and complex internal pores, and chemical adsorption through coordination reactions between the CO and CN bonds on the negative zeta potential of the carbon layer on the activated carbon surface and metal cations. In high-salt environments, Na… + Due to the high concentration, it will crowd out the internal pores of activated carbon, causing Pb to... 2+ Difficulty in entering the pores leads to AC-Pb 2+ The adsorption performance decreased sharply due to strong interference. Experimental data show that in a saline environment, AC-Pb... 2+ The adsorption capacity K value was 13.979 mg / g, while under high-salt conditions (C... Na + =0.1mol / L), the K value dropped to 1.987mg / g, and the adsorption performance was almost lost. Current literature research mainly focuses on modifying activated carbon with strong acids, strong bases, and strong oxidants. After modification, the internal pores of activated carbon can be widened and optimized, allowing Na+ to be adsorbed more readily. + It is easier for Pb to pass through the channel, avoiding channel blockage.2+ While it allows for better adsorption through pores, it may also cause problems such as operational safety and secondary pollution in practical applications. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the aforementioned background technology and provide a method for preparing activated carbon for lead adsorption in high-salt environments. This method involves a one-step composite modification treatment of activated carbon particles using tannic acid and triethanolamine in a water bath to prepare activated carbon that can adsorb lead (Pb) even under high-salt environmental interference. 2+ Activated carbon materials that still retain some adsorption capacity.

[0005] To achieve the objectives of this invention, the method for preparing lead-adsorbing activated carbon in a high-salt environment includes mixing tannic acid and triethanolamine to obtain a mixed solution, which is then used as a modifying agent to modify the activated carbon in a water bath environment.

[0006] Furthermore, in some embodiments of the present invention, the volume-to-mass ratio of the mixed solution to activated carbon is 35-45:1.

[0007] Furthermore, in some embodiments of the present invention, the volume-to-mass ratio of the mixed solution to activated carbon is 38-42:1.

[0008] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.5-8.5%.

[0009] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.7-6.5%.

[0010] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.7-4.5%.

[0011] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.8-2.2%, and the volume concentration of triethanolamine is 1.8-2.2%.

[0012] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.9-2.1%, and the volume concentration of triethanolamine is 1.9-2.1%.

[0013] Furthermore, in some embodiments of the present invention, the mass concentration of tannic acid in the mixed solution is 1.95-2.05%, and the volume concentration of triethanolamine is 1.95-2.05%.

[0014] Furthermore, in some embodiments of the present invention, the water bath temperature is 75-85°C.

[0015] Furthermore, in some embodiments of the present invention, the water bath temperature is 78-82°C.

[0016] Furthermore, in some embodiments of the present invention, the modification treatment of activated carbon in the water bath environment is carried out for 2.5-3.5 hours.

[0017] Furthermore, in some embodiments of the present invention, after the modification treatment is completed, the reaction solution is removed, ultrasonically cleaned until the solution pH is neutral, and then dried.

[0018] Furthermore, in some embodiments of the present invention, the drying process is a drying treatment at 58-62°C for 5-7 hours.

[0019] Among the modifying reagents selected in this experiment, tannic acid is a food-grade acidic modifier that exhibits excellent safety at room temperature, and triethanolamine is also a commonly used stabilizer in chemical experiments, with very safe properties. Therefore, all raw materials used in the entire modification experiment are safe reagents, offering higher safety compared to commonly used modifying reagents for activated carbon. This invention achieves the best modification effect for activated carbon in an 80℃ water bath environment using a 2wt% + 2vt% composite modification, resulting in an adsorption capacity K value of 14.724 mg / g after modification, demonstrating practical application value. Attached Figure Description

[0020] Figure 1 This invention relates to tannic acid-modified AC-Pb. 2+ Adsorption capacity diagram; Figure 2 The triethanolamine-modified activated carbon AC-Pb in this invention 2+ Adsorption capacity diagram; Figure 3 The present invention is a composite modification of AC-Pb by tannic acid and triethanolamine. 2+ Adsorption capacity diagram; Figure 4 These are SEM 1000x images of activated carbon surfaces under different modification conditions in this invention. (a) Unmodified activated carbon; (b) Activated carbon modified with 2 wt% tannic acid; (c) Activated carbon modified with 8 wt% triethanolamine; (d) Activated carbon modified with a composite of 2 wt% tannic acid and 2 wt% triethanolamine. Figure 5These are SEM 4000x images of activated carbon surfaces under different modification conditions in this invention. (a) Unmodified activated carbon; (b) Activated carbon modified with 2 wt% tannic acid; (c) Activated carbon modified with 8 wt% triethanolamine; (d) Activated carbon modified with a composite of 2 wt% tannic acid and 2 wt% triethanolamine. Figure 6 This is an EDS elemental distribution diagram of the activated carbon surface under different modification conditions in this invention. (a) Unmodified activated carbon; (b) Activated carbon modified with 2 wt% tannic acid; (c) Activated carbon modified with 8 wt% triethanolamine; (d) Activated carbon modified with a composite of 2 wt% tannic acid and 2 wt% triethanolamine. Figure 7 These are EDS elemental line scans of activated carbon surfaces under different modification conditions in this invention. (a) Unmodified activated carbon; (b) Activated carbon modified with 2 wt% tannic acid; (c) Activated carbon modified with 8 wt% triethanolamine; (d) Activated carbon modified with a composite of 2 wt% tannic acid and 2 wt% triethanolamine. Figure 8 These are FT-IR images of activated carbon under different modification conditions in this invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and not intended to limit the invention.

[0022] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0023] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0024] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1 to 5” is disclosed, the described range should be interpreted as including the ranges “1 to 4”, “1 to 3”, “1 to 2”, “1 to 2 and 4 to 5”, “1 to 3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0025] The singular form includes the plural objects of discussion unless the context clearly indicates otherwise. "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event occurs and the possibility that the event does not occur.

[0026] Approximate terms used in the specification and claims to modify quantities indicate that the invention is not limited to that specific quantity, but also includes acceptable modifications close to that quantity that do not alter the relevant essential function. Correspondingly, the use of "about," "approximately," etc., to modify a numerical value means that the invention is not limited to that precise value. In some instances, approximate terms may correspond to the precision of the instrument used to measure the value. In this application's specification and claims, scope definitions can be combined and / or interchanged, unless otherwise stated, these scopes include all subscopes contained therein.

[0027] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0028] Furthermore, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., described below refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example. Moreover, the technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0029] The high saline system AC-Pb in this invention 2+ The adsorption capacity test method is as follows: The xylenol orange spectrophotometric method was used for testing. 0.1 g of modified activated carbon was weighed into an iodine flask, and 50 ml of 100 mg / L lead standard solution and 50 ml of 0.2 mol / L acetic acid-sodium acetate solution (27.2 g sodium acetate trihydrate + 0.6 ml glacial acetic acid were added to make up to 1 L) were added to simulate a high saline environment of 0.1 mol / L Na+. The mixture was shaken in a water bath at 30 °C and 200 r / min for 2 h.

[0030] Transfer 5 ml of the adsorbed lead solution to a 25 ml colorimetric tube using a pipette. Then add 2 ml of 16.8 ml / L acetic acid solution and 3 ml of 0.1 g xylenol orange solution. After 10 min, shake well. Set the spectrophotometer to 575 nm, zero the blank tube, and test the adsorption capacity. Compare the results with the standard curve to obtain the lead ion concentration and adsorption capacity data K. The formula is as follows: K = (C0) _ C)•V / m K: Adsorption capacity (mg / g) C0: Initial lead ion concentration (0.05 mg / ml) C: Concentration of lead ions in the solution after adsorption (mg / ml) V: Measurement of solution volume (100ml) m: Adsorbent mass (g) The table below shows the AC-Pb content of the unmodified activated carbon of this invention under different environments. 2+ Adsorption capacity: Table 1. AC-Pb of unmodified activated carbon under different environments. 2+ Adsorption capacity Example 1 Tannic acid modified activated carbon Add approximately 2g of activated carbon granules to each of six 100ml Erlenmeyer flasks, then pour in 80ml of 1wt%, 2wt%, 4wt%, 6wt%, 8wt%, and 10wt% tannic acid solutions, respectively. Place the six Erlenmeyer flasks sequentially into a food vacuum sealer, seal the lids, and use an electric vacuum pump to evacuate for 5 minutes to remove air bubbles (under negative pressure, the air in the micropores of the activated carbon will expand and dissolve, allowing the modifying reagent to fully penetrate). Remove the Erlenmeyer flasks and place them in a water bath, securing them with metal clamps. The mouth of the conical flask was sealed tightly with a single-hole rubber stopper. A 1-meter-long glass tube was inserted as a pressure relief tube (the bottom of the glass tube should not touch the solution, because volatile gases will be generated during the reaction due to temperature rise and chemical reaction, and the pressure relief tube is needed to release the gases; the 1-meter-long pressure relief tube also allows water vapor to cool and flow back into the conical flask as it rises, reducing water loss). After reacting at 80℃ for 3 hours, the conical flask was removed, the reaction solution was poured out, and the solution was ultrasonically cleaned with deionized water (changing the water every 10 minutes, ultrasonic for 30 minutes) until the pH of the solution was neutral. The solution was then placed in a vacuum drying oven at 60℃ for 6 hours to dry under vacuum for AC-Pb reaction. 2+ Adsorption capacity test.

[0031] Table 2 shows the AC-Pb modified with different concentrations of tannic acid. 2+ Adsorption capacity (high saline system). Water bath modification with 1 wt% tannic acid provides some improvement, while 2 wt% modification yields the best results for AC-Pb. 2+ The adsorption capacity (K value) reached 9.203 mg / g. Under high-temperature water bath conditions, tannic acid exhibited strong acidity and oxidizing properties, effectively etching activated carbon, optimizing and widening micropores, and preventing Na+ adsorption. + Ions block pores; simultaneously, oxidized activated carbon enhances the oxygen-containing functional groups with negative zeta potential within the micropores of the material, thereby improving the material's resistance to Pb. 2+ The material exhibits both physical and chemical adsorption properties. However, as the concentration of tannic acid continues to increase, the K value begins to decrease, indicating that excessive oxidation and etching can significantly damage the material's structure, leading to a collapse in its performance.

[0032] Table 2. AC-Pb modified with different concentrations of tannic acid 2+ Adsorption capacity Figure 1 AC-Pb modified with tannins 2+ Adsorption capacity graph. As can be seen from the graph, with increasing tannic acid concentration, AC-Pb... 2+ The adsorption capacity exhibits an inverted U-shaped curve, reaching its maximum at 2 wt%. Subsequently, as the tannic acid concentration further increases, the etching and oxidation effects become too intense, leading to a decline in the material's performance, which continues to decrease.

[0033] The results showed that the adsorption performance of activated carbon was improved after water bath modification with tannic acid. After modification with 1 wt% tannic acid, the adsorption performance of ACF-Pb was improved. 2+ The adsorption capacity K value immediately increased to 7.230 mg / g, reaching its maximum of 9.203 mg / g with 2 wt% tannic acid modification. However, with further increases in tannic acid concentration, the material properties began to decline. Overall, tannic acid modification showed a significant effect on AC-Pb adsorption under high-salt conditions. 2+ There has been a significant improvement, but overall it has not reached the adsorption performance of activated carbon under normal conditions.

[0034] Tannic acid is a food-grade acidity modifier that is relatively mild at room temperature. However, its ionization level increases significantly under high-temperature water bath conditions, greatly increasing the acidity of the solution. Furthermore, tannic acid has strong adhesive properties and exhibits very strong etching and oxidative modification effects on activated carbon. When the tannic acid concentration is too high, the material will be over-etched, causing the microporous structure to collapse and the surface to be excessively etched. This can be clearly observed in the SEM characterization analysis results.

[0035] Example 2 Triethanolamine-modified activated carbon Add approximately 2g of activated carbon granules to each of five 100ml Erlenmeyer flasks, then pour in 80ml of 2vt%, 4vt%, 6vt%, 8vt%, and 10vt% triethanolamine solutions, respectively. Place the five Erlenmeyer flasks in a food vacuum sealer, seal the lids, and use an electric vacuum pump to evacuate for 5 minutes to remove air bubbles. Remove the Erlenmeyer flasks and place them in a water bath, securing them with iron clamps. Seal the mouths of the Erlenmeyer flasks with single-hole rubber stoppers, insert a 1m long glass tube as a pressure relief tube, and set the reaction temperature to 80℃ for 3 hours. After that, remove the Erlenmeyer flasks, pour out the reaction solution, and ultrasonically clean them with deionized water (changing the water every 10 minutes, ultrasonic for 30 minutes) until the solution pH is neutral. Place them in a vacuum drying oven at 60℃ for 6 hours to dry, and then proceed with AC-Pb analysis. 2+ Adsorption capacity test.

[0036] Table 3 shows the AC-Pb modified with different concentrations of triethanolamine. 2+ The adsorption capacity (high saline system) showed a slight increase in the K value after triethanolamine modification, but the improvement was not significant. The 8 wt% triethanolamine modification showed the best effect, with a K value reaching 4.889 mg / g. Due to steric hindrance, some triethanolamine remained within the activated carbon pores after the water bath reaction, increasing the O and N content of the material. The negative Zata potential of N effectively enhanced the material's adsorption capacity for Pb. 2+ The adsorption performance is good. However, the modification effect of triethanolamine is not very obvious.

[0037] Table 3. AC-Pb modified with triethanolamine at different concentrations 2+ Adsorption capacity Figure 2 AC-Pb, a triethanolamine-modified activated carbon 2+ The adsorption capacity graph shows that the adsorption performance of the material increases with increasing triethanolamine concentration, with the best modification effect at 8 vt%. Subsequently, as the triethanolamine concentration is further increased to 10 vt, the adsorption performance remains essentially constant, indicating that the modification effect has reached saturation.

[0038] The results show that triethanolamine, being a chemically safe buffer, exhibits good stability at normal temperatures. After the water bath reaction, due to port hydrogen bonds and its relatively large steric hindrance of vacancy migration, some of it remains inside the activated carbon channels, increasing the O and N content of the material. The negative Zata potential of N can effectively enhance the material's resistance to Pb. 2+ The adsorption performance was assessed. Water bath modification with 8 wt% triethanolamine showed the best effect, with an adsorption capacity K value of 4.889 mg / g. Although this is a significant improvement over the 1.987 mg / g of unmodified activated carbon, the overall performance is still not ideal.

[0039] Example 3 Tannic acid (A) + triethanolamine (B) composite water bath modified activated carbon Add approximately 2g of activated carbon granules to each of five 100ml Erlenmeyer flasks, then pour in 80ml of mixed solutions of 2wt%A+2vt%B, 2wt%A+4vt%B, 2wt%A+6vt%B, 2wt%A+8vt%B, and 2wt%A+10vt%B, respectively. Place the five Erlenmeyer flasks in a food vacuum sealer, seal the lids, and use an electric vacuum pump to evacuate for 5 minutes to remove air bubbles. Remove the Erlenmeyer flasks and place them in a water bath, securing them with iron clamps. Seal the mouths of the Erlenmeyer flasks with single-hole rubber stoppers, insert a 1m long glass tube as a pressure relief tube, and react at 80℃ for 3 hours. After that, remove the Erlenmeyer flasks, pour out the reaction solution, and ultrasonically clean them with deionized water (changing the water every 10 minutes, ultrasonic for 30 minutes) until the solution pH is neutral. Place them in a vacuum drying oven at 60℃ for 6 hours to dry, and then proceed with AC-Pb analysis. 2+ Adsorption capacity test.

[0040] Because 2wt% tannic acid showed the best modification effect, but the etching effect on the material was too obvious, tannic acid and triethanolamine were mixed in different proportions to prepare buffer solutions. The addition of triethanolamine can effectively control the strong acidity of tannic acid in a high-temperature water bath environment, and at the same time, it is easier to hydrolyze amine groups in an acidic environment to react with activated carbon for nitrogen modification. Table 4 shows the composite modification of AC-Pb by tannic acid (A) + triethanolamine (B). 2+Adsorption capacity (high saline system). As shown in Table 4, the modification effect of 2%A+2%B is the best, with the K value rising directly to 14.724 mg / g. The adsorption capacity is slightly higher than that of activated carbon in a salt-free environment, and the effect is very ideal. However, as the amount of triethanolamine in the buffer solution system increases, the effect of composite modification continuously decreases. This is because although increasing the proportion of triethanolamine can increase the nitrogen-containing functional groups of the material, the overall pH of the buffer solution increases, and the oxidation and etching effects decrease. The antagonistic effect of these two factors leads to an imbalance in the modification effect, and ultimately the modification effect weakens continuously.

[0041] Table 4. AC-Pb modified by tannic acid (A) + triethanolamine (B) 2+ Adsorption capacity Figure 3 For composite modification treatment of AC-Pb 2+ Adsorption data graph. It is clear from the graph that the composite modification effect of 2% tannic acid + 2% triethanolamine is the best. As the proportion of triethanolamine increases, the adsorption performance of the material continuously decreases. Excessively high proportions of triethanolamine inhibit the etching and oxidation effects of the reagent on the activated carbon. The results showed that the combined water bath modification with tannic acid and triethanolamine was more effective than modification with a single reagent. The 2wt%A + 2vt%B mixture showed the best modification effect, achieving an adsorption capacity (K value) of 14.724 mg / g under high-salt conditions, comparable to AC-Pb under pure water conditions. 2+ The adsorption capacity was equivalent to 13.979 mg / g, indicating a very significant modification effect. Triethanolamine, acting as a buffer, effectively controlled the oxidation and etching effects of tannic acid on activated carbon under high-temperature water bath conditions, and the buffer solution system also ensured the stability of the environment during the modification process. However, as the proportion of triethanolamine was further increased, the modification effect gradually decreased. This is because increasing the proportion of triethanolamine in the tannic acid-triethanolamine buffer solution system reduces the acidity of the solution environment, thus reducing the oxidation and etching effects of the reagent on the activated carbon. Furthermore, excessive loading of viscous triethanolamine may clog the internal pores of the activated carbon, thereby inhibiting its modification.

[0042] Example 3 This invention uses scanning electron microscopy to observe the changes in the microstructure of activated carbon materials before and after modification.

[0043] Figure 4 These are SEM 1000x images of activated carbon surfaces under different modification conditions. As can be seen in 4(a), the activated carbon surface has a certain distribution of micropores, the overall pore size of the micropores is relatively small, the activated carbon surface is relatively rough, and there are many amorphous carbon layer powder fragments; Figure 4(b) It is clearly visible that 2 wt% tannic acid exhibits significant etching properties under high-temperature water bath conditions. After tannic acid modification, the material surface is densely covered with large-diameter micropores, and the overall structure even presents an irregular perforated honeycomb-like pore structure. The expansion and increase of pores can effectively increase the specific surface area of ​​carbon materials and Na+. + The smooth flow of ions allows Pb 2+ Ions can easily enter the internal pores for adsorption. However, if the concentration of tannic acid is further increased, the etching intensity will continue to intensify, directly damaging the material's structure and causing the entire structure to collapse. Figure 4 (c) It can be seen that in an 8vt% triethanolamine water bath environment, multiple -OH groups of triethanolamine can undergo adsorption reaction with CO on the surface of activated carbon, causing the carbon layer to peel off and exposing the internal pores of activated carbon. However, this will reduce the oxygen content on the surface of activated carbon and decrease the chemical adsorption performance of the material surface. Figure 4 As shown in (d), the addition of triethanolamine can effectively control the acidity and etching intensity of tannic acid, making the etching degree of the activated carbon obvious and controllable. After composite modification, the micropores on the surface of the activated carbon are significantly enlarged, and a certain physical structure is maintained without the appearance of a fragile perforated honeycomb structure.

[0044] Figure 5 These are SEM 4000x images of activated carbon surfaces under different modification conditions. Figure 5 (a) It is evident that the surface of the unmodified activated carbon contains interconnected micropores. The abundant internal channels increase the overall specific surface area of ​​the activated carbon, resulting in good adsorption performance. However, the micropores have relatively small pore sizes, which can lead to poor adsorption of high concentrations of Na+. + Ions easily clog the pores, making Pb 2+ Ions have difficulty entering, resulting in a decrease in adsorption capacity. Figure 5 (b) It can be seen more clearly that after modification with tannic acid, obvious etching marks appear on the surface and inside of the activated carbon. Excessive etching will damage the internal structure of the material, which is not conducive to the adsorption modification of the material. Figure 5 (c) It can be seen that under the high temperature water bath environment, multiple -OH groups of triethanolamine can undergo an adsorption reaction with CO on the surface of activated carbon, causing the carbon layer to peel off and widening the internal pores of the activated carbon. Figure 5 (d) It can be seen that after composite modification, the excessive etching phenomenon of the material is controlled to a certain extent, and the obvious pore widening helps to increase the specific surface area of ​​the material and improve the physical adsorption performance of the material.

[0045] Figure 6 This is an EDS elemental distribution map on the surface of activated carbon under different modification conditions. Figure 6 (a) It can be seen that the raw material of unmodified activated carbon is bamboo charcoal, so it has certain oxygen-containing functional groups and a small amount of nitrogen-containing functional groups. Figure 6(b) It can be seen that after modification with 2 wt% tannic acid, there are more pores on the surface of the material and oxygen is evenly distributed on the surface of the material. Figure 6 (c) It can be seen that after modification with 8 vt% triethanolamine, the oxygen content distribution of the material becomes sparse due to the peeling of the carbon layer, and the modification effect is not obvious. Figure 6 (d) After composite modification, the distribution of oxygen becomes denser locally, and the distribution of nitrogen also increases. The dense distribution of oxygen-containing and nitrogen-containing functional groups can effectively improve the material's resistance to Pb. 2+ Chemisorption properties of ions.

[0046] Figure 7 EDS line scans of activated carbon surfaces under different modification conditions. Figure 7 (b) It can be seen that after modification with 2 wt% tannic acid, although tannic acid has a certain oxidizing effect, the activated carbon structure began to collapse due to the excessive etching, and the overall oxygen-containing functional groups of the material decreased slightly. Figure 7 (c) It can be seen that the nitrogen-containing functional groups of activated carbon increased to a certain extent after modification with 8 vt% triethanolamine, but the oxygen-containing functional groups decreased significantly due to the exfoliation of the carbon layer. From the perspective of chemical adsorption, the water bath modification effect of monotriethanolamine was not ideal. Figure 7 (d) As can be seen, after composite modification with 2 wt% tannic acid + 8 wt% triethanolamine, the oxygen-containing functional groups of activated carbon remain almost unchanged. The exfoliation of the carbon layer and the oxidation of the graphite carbon surface play a counterbalancing role, but the nitrogen-containing functional groups increase significantly, thus improving the chemisorption performance of the material. Composite modification can control the etching intensity, maintain the physical structure of the material while widening the internal channels, and increasing the physical adsorption performance of the material; at the same time, the overall increase in oxygen-containing and nitrogen-containing functional groups is beneficial to improving the chemisorption performance of the material. The synergistic effect of the two makes the material more effective in high-salt environments for AC-Pb. 2+ The adsorption capacity reaches 14.724 mg / g, which has practical application value.

[0047] To better understand the specific types of functional groups that increase oxygen and nitrogen content after activated carbon modification, this invention performed FT-IR characterization on the material. Among them, 1398 cm⁻¹ -1 The strong peak is the symmetric stretching vibration peak of -COOH, at 1556 cm⁻¹. -1 Several strong peaks nearby are coupling peaks of the bending vibration of -NH and the stretching vibration of CN. (1650 cm⁻¹) -1 The peaks are mainly C=O stretching vibration peaks. From Figure 8As can be seen, the composite modification of this invention effectively combines the modification effects of tannic acid and triethanolamine. The -COOH and -NH functional groups are increased to a certain extent compared with the unmodified activated carbon. The oxygen and nitrogen content of the material generally increases after the modification treatment, which improves the chemical adsorption performance of the material. The characterization results correspond to the EDS characterization results.

[0048] Those skilled in the art will readily understand that the above description is merely a partial example of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing activated carbon for lead adsorption in high-salt environments, characterized in that, The method includes mixing tannic acid and triethanolamine to obtain a mixed solution, which is then used as a modifying agent to modify activated carbon in a water bath environment.

2. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The volume-to-mass ratio of the mixed solution to activated carbon is 35-45:1; preferably, the volume-to-mass ratio of the mixed solution to activated carbon is 38-42:

1.

3. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.5-8.5%.

4. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.7-6.5%.

5. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The mass concentration of tannic acid in the mixed solution is 1.7-2.3%, and the volume concentration of triethanolamine is 1.7-4.5%.

6. The method for preparing lead-adsorbing activated carbon in a high-salt environment according to claim 1, characterized in that, The mass concentration of tannic acid in the mixed solution is 1.8-2.2%, and the volume concentration of triethanolamine is 1.8-2.2%; preferably, the mass concentration of tannic acid in the mixed solution is 1.9-2.1%, and the volume concentration of triethanolamine is 1.9-2.1%; more preferably, the mass concentration of tannic acid in the mixed solution is 1.95-2.05%, and the volume concentration of triethanolamine is 1.95-2.05%.

7. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The water bath temperature is 75-85℃; preferably, the water bath temperature is 78-82℃.

8. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, The modification time of activated carbon in the water bath environment is 2.5-3.5 hours.

9. The method for preparing lead-adsorbing activated carbon in high-salt environments according to claim 1, characterized in that, After the modification treatment is completed, the reaction solution is removed, and the solution is ultrasonically cleaned until the pH of the solution is neutral, and then dried.

10. The method for preparing lead-adsorbing activated carbon in a high-salt environment according to claim 1, characterized in that, The drying process involves drying at 58-62℃ for 5-7 hours.

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