Preparation method of salt-resistant adsorbent for treating high-salt printing and dyeing wastewater

Abstract

The invention aims to provide a preparation method of a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater, and belongs to the technical field of water pollution repair / treatment. The preparation method comprises the following steps: by taking hydroxide as a precipitator, dropwise adding chitosan (CS) dissolved in acetic acid into a hydroxide solution, and aging for 24 hours to obtain CS gel balls; the obtained gel ball does not need to be washed with water, and the residual hydroxide is used as a pore-forming agent of the chitosan ball. And drying at 35 DEG C for 12 hours, putting into a tubular furnace, calcining in an N2 atmosphere, cooling to room temperature after calcining, washing to be neutral with deionized water, and drying for later use. The carbon material prepared by the method can be used for adsorbing and removing dyes in high-salt printing and dyeing wastewater, and has a wide application prospect in the field of treatment of industrial wastewater such as printing and dyeing, spinning and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of water pollution remediation / treatment, and particularly relates to a method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater. Background Art

[0002] Dyes have the characteristics of long-lasting color and non-biodegradability. Among the many water treatment technologies, adsorption is a common and effective method for removing organic pollutants from wastewater due to its low energy consumption, high efficiency, ease of operation, and lack of secondary pollution. Commonly used adsorbents include activated carbon, minerals, high-molecular-weight organic compounds, zeolites, and biomass. However, the printing and dyeing process requires the addition of large amounts of salt additives to enhance the effect, resulting in high salinity in dyeing wastewater, with TDS (Total Dissolved Solid) values ​​reaching 4,000 to 10,000 mg / L. Existing adsorbent materials generally experience reduced adsorption capacity in high-salt systems, significantly limiting their practical application. Therefore, the development of salt-tolerant adsorbents for the treatment of high-salt dyeing wastewater is urgent. Summary of the Invention

[0003] Aiming at the problem that the adsorption capacity of existing adsorption materials is reduced in a high-salt system, the present invention provides a method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater.

[0004] In order to solve the above problems, the present invention adopts the following technical solutions: A method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater comprises the following steps: S1, dissolving chitosan powder in acetic acid aqueous solution, stirring and standing to remove bubbles to obtain a mixed solution; S2, using a syringe to add the mixed solution obtained in S1 dropwise to the aqueous solution of hydroxide, and let it stand for 24 hours to obtain chitosan gel spheres; S3, directly placing the gel balls obtained in S2 into an oven for drying; S4. After drying, the mixture is placed in a tube furnace and heated and carbonized from room temperature under a N2 atmosphere. After carbonization, the mixture is cooled to room temperature. The obtained material is washed with deionized water until neutral and dried to obtain the salt-resistant adsorbent.

[0005] Furthermore, the usage ratio of the chitosan powder, acetic acid aqueous solution, and hydroxide aqueous solution is 1-3 g: 50-150 mL: 50-150 mL; the volume fraction of the acetic acid aqueous solution is 1-5%; and the concentration of the hydroxide aqueous solution is 0.5-1 mol / L.

[0006] Furthermore, the hydroxide includes any one of potassium hydroxide and sodium hydroxide or a mixture of the two.

[0007] Furthermore, the oven drying temperature in S3 is 35-85° C., and the drying time is 6-12 hours.

[0008] Furthermore, the heating rate of the tubular furnace is 10° C. / min, the carbonization temperature is 600-800° C., and the carbonization time is 1-3 hours.

[0009] A salt-resistant adsorbent is used for the adsorption and removal of dyes in high-salt printing and dyeing wastewater.

[0010] The principle of the present invention is as follows: the biochar prepared according to the above method has a multi-level pore structure, and is mainly composed of meso-macroporous pores. Usually under high salt conditions, dye molecules will undergo salting out and aggregate into ultra-large molecules. The meso-macroporous structure in the biochar prepared by the present invention can accommodate ultra-large molecular dyes, and the phenomenon of decreased adsorption due to steric hindrance will not occur. On the contrary, due to the salting-out effect, a large number of dye molecules are aggregated and adsorbed in the meso-macroporous structure in the biochar, which has a better adsorption effect than a single dye molecule. Therefore, under high salt conditions, the adsorption amount of dye is higher than that under salt-free conditions.

[0011] The beneficial effects of the present invention are as follows: 1. This invention uses biomass chitosan as raw material and hydroxide as a pore-forming agent. By regulating the time and temperature during carbonization, a carbon material with a rich pore structure and large specific surface area is synthesized. 2. The material obtained by this invention is used to adsorb dyes in high-salt wastewater, showing high adsorption capacity and rapid adsorption. In particular, the amount of dye adsorbed under high-salt conditions is higher than under salt-free conditions. 3. The adsorption material prepared by the present invention can adsorb a variety of different types of dyes including cationic and anionic dyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the curve of MB adsorption amount versus adsorption time; Figure 2 This is the effect of adsorbent dosage on the adsorption of MB; Figure 3 is the effect of the initial concentration of the solution on the adsorption of MB; Figure 4 Graph showing the effect of solution pH on the adsorption of MB. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, specific embodiments of the present invention are described in detail, but are not limited thereto. Unless otherwise specified, the raw materials used in the examples are all common commercial products; unless otherwise specified, the methods used are all commonly used methods in the art.

[0014] A method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater comprises the following steps: S1, dissolving chitosan powder in acetic acid aqueous solution, stirring and standing to remove bubbles to obtain a mixed solution; S2, using a syringe to add the mixed solution obtained in S1 dropwise to the aqueous solution of hydroxide, and let it stand for 24 hours to obtain chitosan gel spheres; S3, directly placing the gel balls obtained in S2 into an oven for drying; S4. After drying, the mixture is placed in a tube furnace and heated and carbonized from room temperature under a N2 atmosphere. After carbonization, the mixture is cooled to room temperature. The obtained material is washed with deionized water until neutral and dried to obtain the salt-resistant adsorbent.

[0015] Add 0.005–0.03 g of the salt-resistant adsorbent obtained above to 100 mL of a 40–200 mg / L dye solution containing 0–5 g / L of salt. Adjust the pH to 2–10 and shake on a shaker for 0–180 minutes, taking samples at regular intervals. Determine the dye concentration in the solution using a UV spectrometer. Calculate the adsorption capacity based on the adsorbent mass and the dye concentration before and after adsorption.

[0016] The dyes include any one of the cationic dyes methylene blue, rhodamine B, methyl violet, basic fuchsin, cationic blue X-GRRL, basic bright yellow O, cationic violet 5BN, neutral red, and the anionic dyes methyl orange, Congo red, acid red, acid orange 7, sunset yellow, acid blue 9, or a mixture of any two or more dyes.

[0017] The salt includes any one of sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium nitrate, sodium sulfate, and sodium carbonate, or a mixture of several of them.

[0018] 1. Effect of carbonization conditions on the adsorption properties of materials Example 1 1) Dissolve 1 g of chitosan powder in 50 mL of 1% acetic acid aqueous solution, stir and allow to cool to remove bubbles. Then, use a syringe to dropwise add the suspension to 100 mL of a 1.0 mol / L hydroxide solution in water. After immersing in the hydroxide solution for 24 hours, CS gel spheres are obtained. The resulting gel spheres are dried in an oven at 35°C for 12 hours without washing. They are then heated in a tube furnace under a nitrogen atmosphere at a heating rate of 10°C / min from room temperature to 800°C for 2 hours to obtain the salt-resistant adsorbent.

[0019] 2) Add 0.01 g of the salt-resistant adsorbent obtained above to 100 mL of a 100 mg / L methylene blue (MB) solution and shake on a shaker for 180 minutes. After adsorption equilibrium, the solution was filtered through a 0.45 µm filter and then measured by UV spectrometry. Repeat the above experimental procedure. The MB concentration measured without the adsorbent is referred to as the blank run. The actual MB equilibrium adsorption capacity is the difference between the measured concentration and the blank run concentration. The calculated MB adsorption capacity is 789.9 mg / g.

[0020] Example 2 Example 1 was repeated, except that the amount of chitosan powder in step 1) was changed from 1 g to 2 g, the carbonization temperature was changed from 800° C. to 700° C., and the dye was changed to rhodamine B. The adsorption capacity of rhodamine B at equilibrium was 494.7 mg / g.

[0021] Example 3 Example 1 was repeated, except that the amount of chitosan powder in step 1) was changed from 1 g to 3 g, the volume fraction of acetic acid was changed from 1% to 5%, the carbonization temperature was changed from 800°C to 600°C, and the dye was changed to methyl violet. The adsorption capacity of methyl violet at equilibrium was 256.0 mg / g.

[0022] Example 4 Example 1 was repeated, except that the hydroxide concentration in step 1) was changed from 1.0 mol / L to 0.5 mol / L, the carbonization time was changed from 2 h to 3 h, and the dye was changed to basic fuchsin. The adsorption capacity of basic fuchsin at equilibrium was 362.7 mg / g.

[0023] Example 5 Example 1 was repeated, except that the volume of the hydroxide aqueous solution in step 1) was changed to 150 mL, the carbonization time was changed from 2 h to 1 h, and the dye was changed to cationic blue X-GRRL. The adsorption capacity of cationic blue X-GRRL at equilibrium was 461.3 mg / g.

[0024] Example 6 Example 1 was repeated, except that the volume of the acetic acid aqueous solution in step 1) was changed to 150 mL, and the MB solution in step 2) was replaced with a methyl orange (MO) solution. The adsorption capacity of MO at equilibrium was 308.3 mg / g.

[0025] Example 7 Example 1 was repeated, except that the volume of the hydroxide aqueous solution in step 1) was changed to 50 mL, and the MB solution in step 2) was replaced with a neutral red (NR) solution. The adsorption capacity of NR at equilibrium was 440.0 mg / g.

[0026] Example 8 Example 1 was repeated, except that the drying temperature in step 1) was changed from 35°C to 85°C, and the MB solution in step 2) was replaced with a Congo red solution. The adsorption capacity of Congo red at equilibrium was 330.0 mg / g.

[0027] Example 9 Example 1 was repeated, except that the drying time in step 1) was changed from 12 h to 6 h, and the MB solution in step 2) was replaced with a solution of Acid Blue 9. The adsorption capacity of Acid Blue 9 at equilibrium was 315.0 mg / g.

[0028] Example 10 Example 1 was repeated, but in step 2) the MB solution was replaced with a mixed solution of 100 mg / L of Basic Yellow O and 100 mg / L of Cationic Violet 5BN. The equilibrium adsorption capacity of Basic Yellow O was 669.8 mg / g, and that of Cationic Violet 5BN was 423.0 mg / g.

[0029] Example 11 Example 1 was repeated, except that the MB solution in step 2) was replaced with a mixed solution of 100 mg / L Acid Red, 100 mg / L Acid Orange 7, and 100 mg / L Sunset Yellow. The equilibrium adsorption capacities for Acid Red, Acid Orange 7, and Sunset Yellow were measured to be 368.7 mg / g, 400.5 mg / g, and 277.4 mg / g, respectively.

[0030] 2. Effect of high salt conditions on the adsorption performance of materials Example 12 Example 1 was repeated, but sodium chloride, potassium chloride, magnesium chloride, calcium chloride, sodium nitrate, and sodium sulfate were added to the salt-free MB solution in step 2), with the salt concentrations all being 2 g / L. At adsorption equilibrium, the MB adsorption capacities were 862.9 mg / g, 909.1 mg / g, 788.7 mg / g, 859.7 mg / g, 888.5 mg / g, and 756.9 mg / g, respectively. Compared to the salt-free solution, the MB adsorption capacity increased under high-salt conditions.

[0031] Example 13 Example 1 was repeated, except that sodium chloride was added to the salt-free MB solution in step 2) at concentrations of 1 g / L, 2 g / L, 3 g / L, and 4 g / L, respectively. At adsorption equilibrium, the adsorption amounts of MB were 807.7 mg / g, 862.9 mg / g, 898.1 mg / g, and 940.0 mg / g, respectively.

[0032] Example 14 Example 1 was repeated, except that the MB solution in step 2) was replaced with a MO solution. Sodium chloride and sodium sulfate were added to the salt-free MO solution in step 2) to a mixed salt concentration of 2 g / L. The adsorption capacity of MO at equilibrium was measured to be 458.5 mg / g.

[0033] Example 15 Example 1 was repeated, except that the MB solution in step 2) was replaced with a NR solution. Sodium sulfate, magnesium chloride, potassium chloride, and sodium nitrate were added to the salt-free NR solution in step 2) to a mixed salt concentration of 5 g / L. The equilibrium adsorption capacity of NR was 732 mg / g.

[0034] 3. Influence of adsorption conditions on adsorption performance Example 16 Repeat Example 1, but oscillate for 180 min in step 2) and take samples at regular intervals. The kinetic curve of the adsorption reaction is shown in Figure 2. Figure 1 As shown. Figure 1 It can be seen that the adsorption reaction has a fast rate, and 80% of the adsorption capacity can be completed within 5 minutes.

[0035] Example 17 Example 1 was repeated, but the amount of adsorbent added in step 2) was changed to 0.005-0.02 g. The relationship between the amount of adsorbent added and the adsorption amount and adsorption rate is as follows: Figure 2 As shown. Figure 2 It can be seen that the optimal dosage of adsorption material in this system is 0.1g / L.

[0036] Example 18 Example 1 was repeated, but the concentration of MB solution in step 2) was changed to 40-200 mg / L. The relationship between the initial concentration of MB solution and the adsorption amount is shown in FIG. Figure 3 As shown. Figure 3 It can be seen that when the concentration of MB solution is 100 mg / L, the adsorption material reaches adsorption saturation, and further increasing the solution concentration cannot increase the adsorption capacity of the material.

[0037] Example 19 Example 1 was repeated, but in step 2), the pH value of the solution was adjusted to 2, 3, 4, 5, 6, 7, 8, 9, and 10. The relationship between the pH value of the solution and the adsorption amount is as follows: Figure 4 As shown. Figure 4 It can be seen that within the pH range studied, the adsorption capacity of the adsorption material is not affected by the pH value of the solution.

[0038] Comparative Example 1 Example 1 was repeated, except that in step 1), the precipitated CS gel spheres were washed with deionized water to neutrality before carbonization. After adsorption equilibrium, the measured MB adsorption capacity in water was only 100.6 mg / g.

[0039] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application. The description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all fall within the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater, characterized in that: The steps include: S1, dissolving chitosan powder in acetic acid aqueous solution, stirring and standing to remove bubbles to obtain a mixed solution; S2, using a syringe to add the mixed solution obtained in S1 dropwise to the aqueous solution of hydroxide, and let it stand for 24 hours to obtain chitosan gel spheres; S3, directly placing the gel balls obtained in S2 into an oven for drying; S4. After drying, the mixture is placed in a tube furnace and heated and carbonized from room temperature under a N2 atmosphere. After carbonization, the mixture is cooled to room temperature. The obtained material is washed with deionized water until neutral and dried to obtain the salt-resistant adsorbent.

2. The method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater according to claim 1, characterized in that: The usage ratio of the chitosan powder, acetic acid aqueous solution and hydroxide aqueous solution is 1-3g:50-150mL:50-150mL; the volume fraction of the acetic acid aqueous solution is 1-5%; and the concentration of the hydroxide aqueous solution is 0.5-1mol / L.

3. The method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater according to claim 1, characterized in that: The hydroxide includes any one of potassium hydroxide and sodium hydroxide or a mixture of the two.

4. The method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater according to claim 1, characterized in that: The oven drying temperature in S3 is 35-85° C., and the drying time is 6-12 hours.

5. The method for preparing a salt-resistant adsorbent for treating high-salt printing and dyeing wastewater according to claim 1, characterized in that: The heating rate of the tube furnace is 10° C. / min, the carbonization temperature is 600-800° C., and the carbonization time is 1-3 hours.

6. A salt-resistant adsorbent prepared by the preparation method according to claim 1, which is used for adsorption and removal of dyes in high-salt printing and dyeing wastewater.

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