Preparation method of modified activated carbon adsorption carrier

Abstract

The application provides a preparation method of a modified activated carbon adsorption carrier and relates to the technical field of activated carbon processing. The modified activated carbon adsorption carrier is obtained by the following steps: activating raw activated carbon in a KOH aqueous solution, mixing graphene oxide and then performing ultrasonic centrifugation, immersing the mixture in a mixed aqueous solution of glucoside and starch and then performing centrifugation, performing two-stage heat treatment in a nitrogen atmosphere, and finally cooling under a certain oxygen concentration. The application overcomes the shortcomings of the prior art, and the prepared modified activated carbon adsorption carrier can quickly adsorb hexavalent chromium in wastewater in various environments, thereby ensuring the removal efficiency of hexavalent chromium.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of activated carbon processing, and particularly relates to a preparation method of a modified activated carbon adsorption carrier. BACKGROUND

[0002] Chromium is a common heavy metal pollutant, which widely exists in inferior cosmetic raw materials and industrial wastewater such as electroplating. The existing form in water is mainly hexavalent chromium and trivalent chromium. Among them, hexavalent chromium is a substance that pollutes water bodies.

[0003] Hexavalent chromium can change the taste, odor and color of water, making it more difficult to digest and absorb. Higher content of hexavalent chromium can also cause symptoms such as rhinitis and conjunctivitis, and even cause acute toxicity, such as severe vomiting and diarrhea. And hexavalent chromium is a hydrophilic heavy metal, if it exceeds the standard, it will enter the soil, causing soil ecosystem imbalance, affecting the soil's ability to breathe and retain water, and even posing a risk to plant growth and even killing crops.

[0004] Therefore, how to remove hexavalent chromium in water is crucial. The existing removal methods mainly include chemical reduction method, ion exchange method, electrolysis method, biological method and adsorption method. The chemical reduction method is to reduce hexavalent chromium to trivalent chromium by using chemical reducing agents (such as sodium sulfite, ferrous sulfate, etc.) under acidic conditions, and then remove it by adjusting the pH value to make trivalent chromium form chromium hydroxide precipitate. However, a large amount of chromium-containing sludge is generated during the reduction process, which is easy to cause secondary pollution, and the treatment cost is high. The ion exchange method is to exchange the exchangeable ions on the ion exchange resin with hexavalent chromium ions in water to remove hexavalent chromium from water. However, the cost of ion exchange equipment and resin is high, and the overall operation is complex, which is not suitable for popularization and use. The electrolysis method is to use iron plate as anode, and in the electrolysis process, iron is dissolved to generate ferrous ions. Under acidic conditions, ferrous ions reduce hexavalent chromium ions to trivalent chromium ions, and then remove them by adjusting the pH value to make trivalent chromium form chromium hydroxide precipitate. However, the overall iron plate consumption is high, and the generated sludge is difficult to utilize. The biological method is to use the metabolic activity of microorganisms to remove hexavalent chromium in wastewater. For example, some microorganisms can reduce hexavalent chromium to trivalent chromium to reduce its toxicity. However, the overall operation stability is low, and it is easy to cause secondary pollution. The adsorption method is to use adsorbents (such as activated carbon, zeolite, diatomite, etc.) to adsorb hexavalent chromium ions in wastewater. However, it can only be used for wastewater with low concentration of hexavalent chromium, and the overall adsorption effect is poor.

[0005] Considering the cost and subsequent secondary pollution, activated carbon adsorption of hexavalent chromium is an important research direction. However, general activated carbon can only have good removal effect on hexavalent chromium in wastewater under acidic conditions. How to overcome the problems such as low adsorption efficiency of activated carbon at present and poor adsorption effect at high pH is the focus of the present research. SUMMARY

[0006] In view of the deficiencies in the prior art, the present application provides a preparation method of a modified activated carbon adsorption carrier, which can quickly adsorb hexavalent chromium in wastewater under various environments and ensure the removal efficiency of hexavalent chromium.

[0007] To achieve the above object, the present application is implemented by the following technical solutions:

[0008] A preparation method of a modified activated carbon adsorption carrier, the preparation method comprising the following steps:

[0009] S1, after the raw material activated carbon is ultrasonically cleaned, it is activated and treated in KOH aqueous solution and then dried to obtain a preliminary activated activated carbon;

[0010] S2, the preliminary activated activated carbon is placed in clean water, and then graphene oxide is added, ultrasonic oscillation is performed, and then it is left standing for 2-4h, followed by centrifugal filtration to obtain activated carbon loaded with graphene oxide;

[0011] S3, the activated carbon loaded with graphene oxide is added to a mixed aqueous solution of glucoside and starch, and then it is fully stirred, centrifuged again, and filtered to obtain loaded activated carbon;

[0012] S4, the loaded activated carbon is microwave dried and then heat treated at 200-220℃ under a nitrogen atmosphere for 1-2h to obtain a first heat-treated activated carbon;

[0013] S5, the first heat-treated activated carbon is further heated to 350-400℃ and heat treated for 30-40min to obtain a second heat-treated activated carbon;

[0014] S6, the heat treatment atmosphere of the second heat-treated activated carbon is adjusted to an oxygen concentration of 30%-40%, and then it is cooled to room temperature to obtain a modified activated carbon adsorption carrier.

[0015] Preferably, in the step S1, the mass concentration of KOH in the KOH aqueous solution is 25%-30%, and the activation time is 1-2h.

[0016] Preferably, in the step S1, the drying temperature is 110-120℃, and the drying time is 4-6h.

[0017] Preferably, in the step S2, the mass ratio of graphene oxide to preliminary activated activated carbon is 1:5-8.

[0018] Preferably, in the step S2, the ultrasonic oscillation power is 200-300W, and the oscillation time is 40-60min.

[0019] Preferably, the mass concentration of the glucoside in the mixed aqueous solution of the glucoside and the starch in step S3 is 1%-1.5%, and the mass concentration of the starch is 15%-20%.

[0020] Preferably, the heating rate during the heat treatment in step S4 is 10-15℃ / min.

[0021] Preferably, the rate of the continuous heating in step S5 is 5-10℃ / min.

[0022] Preferably, the rate of the cooling in step S6 is 5-10℃ / min.

[0023] The present application provides a preparation method of a modified activated carbon adsorption carrier, which has the following advantages compared with the prior art:

[0024] The present application uses activated carbon as raw material, loads graphene oxide after KOH activation, and then wraps with glucoside and starch and high-temperature heat treatment, which effectively improves the specific surface area of the activated carbon, improves the physical adsorption efficiency of the activated carbon on hexavalent chromium, ensures good adsorption effect on hexavalent chromium in a wide pH range, and comprehensively improves the application range of the material. DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application are described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0026] The following activated carbon raw material selects coconut shell activated carbon AC (specific surface area about 1363.4m 2 / g, 200 mesh), and the specification of graphene oxide GO is 0.5-3μm, and the thickness is 0.55-1.2nm.

[0027] Embodiment 1:

[0028] Preparation of the modified activated carbon adsorption carrier:

[0029] (1) AC is cleaned with water under 400W ultrasonic for 20min, then taken out and activated in 25% KOH aqueous solution for 2h, then washed with distilled water to neutral, and dried at 110℃ for 6h to obtain a preliminary activated activated carbon;

[0030] (2) The primary activated activated carbon is placed in clean water, and the oxidized graphene is added to the clean water according to a mass ratio of the primary activated activated carbon to the oxidized graphene of 5:1, then 200W ultrasonic oscillation is performed for 60min, and after standing for 2h, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, and GO-AC is obtained;

[0031] (3) A water solution with a glucoside mass concentration of 1% and a starch concentration of 15% is prepared, the GO-AC is placed in the water solution, and after being fully stirred at a speed of 200r / min for 20min, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, and the activated carbon carrier is obtained;

[0032] (4) The activated carbon carrier is dried by 1000W microwave to a water content of ≤6%, and then is placed in a calcining furnace, the air in the furnace is replaced by nitrogen, and then the temperature is increased to 200℃ at a rate of 10℃ / min, and heat treatment is performed for 2h, then the temperature is increased to 350℃ at a rate of 5℃ / min, and heat treatment is continued for 40min, then the oxygen concentration in the furnace is adjusted to 30%, and the temperature is decreased to room temperature at a rate of 5℃ / min, and APG / ST-GO-AC-1 is obtained.

[0033] Example 2:

[0034] Preparation of the modified activated carbon adsorption carrier:

[0035] (1) The AC is cleaned with clean water under 400W ultrasonic for 20min, and then is placed in a KOH water solution with a mass concentration of 30% for activation treatment for 1h, and then is washed with distilled water until neutral, and is dried at a temperature of 120℃ for 4h, and the primary activated activated carbon is obtained;

[0036] (2) The primary activated activated carbon is placed in clean water, and the oxidized graphene is added to the clean water according to a mass ratio of the primary activated activated carbon to the oxidized graphene of 8:1, then 300W ultrasonic oscillation is performed for 40min, and after standing for 4h, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, and GO-AC is obtained;

[0037] (3) A water solution with a glucoside mass concentration of 1.5% and a starch concentration of 20% is prepared, the GO-AC is placed in the water solution, and after being fully stirred at a speed of 200r / min for 20min, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, and the activated carbon carrier is obtained;

[0038] (4) The above loaded activated carbon is dried by microwave of 1000W to water content≤6%, and then placed in a calcination furnace. The air in the furnace is replaced by nitrogen, and then heated to 220°C at a heating rate of 15°C / min for 1h. Then heated to 400°C at a heating rate of 10°C / min, and continue to heat for 30min. Then adjust the oxygen concentration in the furnace to 40%, and then cool to room temperature at a rate of 10°C / min, to obtain APG / ST-GO-AC-2.

[0039] Comparative Example 1:

[0040] Preparation of modified activated carbon adsorption carrier:

[0041] (1) The AC is cleaned with water under ultrasonic wave of 400W for 20min, and then placed in a 25% KOH aqueous solution for activation treatment for 2h. Then washed with distilled water until neutral, and dried at 110°C for 6h to obtain a preliminary activated activated carbon;

[0042] (2) The preliminary activated activated carbon is placed in water, and graphene oxide is added to the water according to a mass ratio of preliminary activated activated carbon to graphene oxide of 5:1. Then ultrasonic oscillation is performed at 200W for 60min, and then placed for 2h. Then centrifuged at a speed of 4200r / min for 10min, and the supernatant is removed to obtain GO-AC;

[0043] (3) A water solution with a glycoside mass concentration of 1% and a starch concentration of 15% is prepared, and the GO-AC is placed in the water solution and stirred at a speed of 200r / min for 20min. Then centrifuged at a speed of 4200r / min for 10min, and the supernatant is removed to obtain a loaded activated carbon;

[0044] (4) The above loaded activated carbon is dried by microwave of 1000W to water content≤6%, and then placed in a calcination furnace. The air in the furnace is replaced by nitrogen, and then heated to 220°C at a heating rate of 15°C / min for 1h. Then heated to 400°C at a heating rate of 10°C / min, and continue to heat for 30min. Then adjust the oxygen concentration in the furnace to 40%, and then cool to room temperature at a rate of 10°C / min, to obtain APG / ST-GO-AC-2.

[0045] Comparative Example 2:

[0046] Preparation of modified activated carbon adsorption carrier:

[0047] (1) The AC is cleaned with water under ultrasonic wave of 400W for 20min, and then placed in a 25% KOH aqueous solution for activation treatment for 2h. Then washed with distilled water until neutral, and dried at 110°C for 6h to obtain a preliminary activated activated carbon;

[0048] (2) The primary activated activated carbon is placed in clean water, and graphene oxide is added to the clean water according to a mass ratio of the primary activated activated carbon to the graphene oxide of 5:1, then 200W ultrasonic oscillation is performed for 60min, and after standing for 2h, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, to obtain GO-AC;

[0049] (3) A starch solution with a concentration of 15% is prepared, the GO-AC is placed in the starch solution, and after being fully stirred at a speed of 200r / min for 20min, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, to obtain the activated carbon carrier;

[0050] (4) The activated carbon carrier is dried by microwave with a power of 1000W until the water content is less than or equal to 6%, and then placed in a calcining furnace, the air in the furnace is replaced with nitrogen, heated to 200℃ at a heating rate of 10℃ / min for heat treatment for 2h, heated to 350℃ at a heating rate of 5℃ / min, and heat treatment is continued for 40min, the oxygen concentration in the furnace is adjusted to 30%, and the temperature is lowered to room temperature at a rate of 5℃ / min, to obtain ST-GO-AC.

[0051] Comparative Example 3:

[0052] Preparation of the modified activated carbon adsorption carrier:

[0053] (1) The AC is cleaned with clean water under ultrasonic cleaning with a power of 400W for 20min, and then taken out and placed in a KOH aqueous solution with a mass concentration of 25% for activation treatment for 2h, and then washed with distilled water until neutral, and dried at a temperature of 110℃ for 6h, to obtain the primary activated activated carbon;

[0054] (2) The primary activated activated carbon is placed in clean water, and graphene oxide is added to the clean water according to a mass ratio of the primary activated activated carbon to the graphene oxide of 5:1, then 200W ultrasonic oscillation is performed for 60min, and after standing for 2h, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, to obtain GO-AC;

[0055] (3) A glucoside solution with a mass concentration of 1% is prepared, the GO-AC is placed in the glucoside solution, and after being fully stirred at a speed of 200r / min for 20min, centrifugation is performed at a speed of 4200r / min for 10min, and the supernatant is removed, to obtain the activated carbon carrier;

[0056] (4) The activated carbon carrier is dried by microwave with a power of 1000W until the water content is less than or equal to 6%, and then placed in a calcining furnace, the air in the furnace is replaced with nitrogen, heated to 200℃ at a heating rate of 10℃ / min for heat treatment for 2h, heated to 350℃ at a heating rate of 5℃ / min, and heat treatment is continued for 40min, the oxygen concentration in the furnace is adjusted to 30%, and the temperature is lowered to room temperature at a rate of 5℃ / min, to obtain APG-GO-AC.

[0057] Comparative Example 4:

[0058] Preparation of modified activated carbon adsorption carrier:

[0059] (1) AC was cleaned with water under 400W ultrasonic for 20min, then was placed in 25% KOH aqueous solution for activation treatment for 2h, then was washed with distilled water until neutral, and was dried at 110℃ for 6h to obtain preliminary activated carbon;

[0060] (2) The preliminary activated carbon was placed in water, and graphene oxide was added to the water according to a mass ratio of the preliminary activated carbon to the graphene oxide of 5:1, then was ultrasonically oscillated for 60min, and was centrifuged at a speed of 4200r / min for 10min after standing for 2h, and the supernatant was removed to obtain GO-AC;

[0061] (3) The GO-AC was dried with 1000W microwave until the water content was less than or equal to 6%, then was placed in a calcination furnace, the air in the furnace was replaced with nitrogen, and was heated to 200℃ at a heating rate of 10℃ / min for heat treatment for 2h, then was heated to 350℃ at a heating rate of 5℃ / min, and was continuously heat treated for 40min, then the oxygen concentration in the furnace was adjusted to 30%, and was cooled to room temperature at a rate of 5℃ / min to obtain GO-AC-1.

[0062] Detection:

[0063] A chromium solution with a concentration of 250mg / L of hexavalent chromium was prepared for standby;

[0064] 1. Detection of the adsorption effect of the modified activated carbon adsorption carrier on hexavalent chromium at different times: 0.2g of the modified activated carbon adsorption carrier was placed in a 100mL conical flask, 50mL of the chromium solution was poured into the conical flask, the pH was adjusted to 4, and the solution was stood for 5min, 20min, 40min and 60min respectively, the concentration of hexavalent chromium in the solution was detected after filtration, and the removal rate was calculated, and the specific results are shown in Table 1:

[0065] Table 1

[0066]

[0067] From the above table, it can be seen that APG / ST-GO-AC-1 and APG / ST-GO-AC-2 can achieve good hexavalent chromium removal effect in a short time, although the removal rate of APG / ST-GO-AC-3 is also high at 20h, but the removal efficiency is slow in the early stage, and the removal efficiency and the final removal rate of ST-GO-AC, APG-GO-AC and GO-AC-1 are all poorer than those of APG / ST-GO-AC-1 and APG / ST-GO-AC-2.

[0068] 2. The adsorption effect of each group of modified activated carbon adsorption carriers on hexavalent chromium under different pH conditions was detected: 0.2 g of modified activated carbon adsorption carrier was placed in a 100 mL conical flask, 50 mL of chromium solution was poured into the conical flask, the pH was adjusted to 3, 4, 6, 8 respectively, and then the solution was left to stand for 40 min. The concentration of hexavalent chromium in the solution was detected after filtration, the removal rate was calculated, and the specific results are shown in Table 2:

[0069] Table 2

[0070]

[0071]

[0072] From the above table, it can be seen that APG / ST-GO-AC-1, APG / ST-GO-AC-2 and APG / ST-GO-AC-3 are less affected by pH, while the removal rate of ST-GO-AC, APG-GO-AC and GO-AC-1 on hexavalent chromium significantly decreases at a higher pH.

[0073] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for producing a modified activated carbon adsorbent carrier, characterized by, The preparation method comprises the following steps: S1, after the raw material activated carbon is ultrasonically cleaned, it is activated and treated in KOH aqueous solution and then dried to obtain a preliminary activated activated carbon; S2, the preliminary activated activated carbon is placed in clean water, and then graphene oxide is added, ultrasonic oscillation is performed, and then it is left to stand for 2-4 h, and then centrifugal filtration is performed to obtain activated carbon loaded with graphene oxide; S3, the activated carbon loaded with graphene oxide is added into a mixed aqueous solution of glucoside and starch, and then it is fully stirred, and then secondary centrifugal filtration is performed to obtain loaded activated carbon; the mass concentration of glucoside in the mixed aqueous solution of glucoside and starch is 1%-1.5%, and the mass concentration of starch is 15%-20%; S4, the loaded activated carbon is microwave dried, and then heat treatment is performed at 200-220 DEG C under a nitrogen atmosphere for 1-2 h to obtain a first heat-treated activated carbon; S5, the first heat-treated activated carbon is continuously heated to 350-400 DEG C, and then heat treatment is performed for 30-40 min to obtain a second heat-treated activated carbon; S6, the heat treatment atmosphere of the second heat-treated activated carbon is adjusted to an oxygen concentration of 30%-40%, and then it is cooled to room temperature to obtain a modified activated carbon adsorption carrier.

2. The method of claim 1, wherein: In the step S1, the mass concentration of KOH in the KOH aqueous solution is 25%-30%, and the activation time is 1-2 h.

3. The method of claim 1, wherein: In the step S1, the drying temperature is 110-120 DEG C, and the drying time is 4-6 h.

4. The method of claim 1, wherein: In the step S2, the mass ratio of graphene oxide to preliminary activated activated carbon is 1:5-8.

5. The method of claim 1, wherein: In the step S2, the ultrasonic oscillation power is 200-300 W, and the oscillation time is 40-60 min.

6. The method of claim 1, wherein: In the step S4, the heating rate during heat treatment is 10-15 DEG C / min.

7. The method of claim 1, wherein: In the step S5, the continuous heating rate is 5-10 DEG C / min.

8. The method of claim 1, wherein: In the step S6, the cooling rate is 5-10 DEG C / min.

Images