Ultrasonic-thermal activated attapulgite applied to organic wastewater and preparation method thereof

Abstract

The invention relates to the technical field of attapulgite, and provides ultrasonic-thermal activated attapulgite applied to organic wastewater and a preparation method thereof, the preparation method comprises the following steps: pretreating attapulgite raw ore, mixing the pretreated attapulgite raw ore with water, carrying out ultrasonic activation, filtering, calcining, carrying out thermal activation, and optionally carrying out acidizing treatment; according to the method, through the synergistic effect of ultrasonic cavitation and heat treatment, fiber bundles of attapulgite are effectively stripped, impurities are removed, and a developed hierarchical pore structure and surface acid sites are formed; the obtained activated attapulgite has excellent adsorption performance on organic pollutants, and is especially suitable for treating complex wastewater containing aromatic organic matters and cationic dyes at the same time; when the adsorbent is applied, the adsorbent is added into wastewater, synchronous and efficient removal of pollutants can be realized after stirring adsorption is performed under proper conditions, and the saturated adsorbent can be regenerated and reused through high-temperature calcination. The method is simple in process, low in cost, high in adsorption efficiency and environment-friendly.

Description

Technical Field

[0001] This invention relates to the field of attapulgite technology, specifically to ultrasonic-thermal activated attapulgite for use in organic wastewater and its preparation method. Background Technology

[0002] Attapulgite is a natural one-dimensional nanomaterial with potential applications in adsorption and catalysis due to its unique pore structure and surface properties. However, natural attapulgite typically suffers from problems such as easy pore clogging, few surface active sites, and limited adsorption capacity, requiring activation treatment to fully realize its performance.

[0003] Traditional activation methods mainly include acid treatment, thermal activation, and organic modification. Acid treatment can remove some impurities, increase specific surface area, and introduce acidic sites, but strong acids easily damage the crystal structure and have limited effect on pore expansion. Thermal activation can effectively remove bound water and organic matter, but single high-temperature treatment may lead to pore collapse or sintering, which in turn reduces porosity. In recent years, ultrasonic activation has attracted attention because its cavitation effect can effectively dissociate mineral aggregates and open micropores, but single ultrasonic treatment is insufficient for deep control of crystal structure and surface chemical properties.

[0004] Existing technologies have attempted to combine different activation methods, such as acid-then-heat or hot-acid combination. However, these combinations are often complex and fail to fully leverage the synergistic effects between steps. Therefore, there is still room for improvement in their effectiveness in preparing high-performance adsorbents with well-developed hierarchical pores and abundant surface acidic sites. In particular, for complex organic wastewater (such as wastewater containing both aromatic organic compounds and ionic dyes), existing adsorbents often face challenges such as poor selectivity, low efficiency in the simultaneous removal of mixed pollutants, and difficulty in regenerating and reusing adsorbents.

[0005] Based on the aforementioned problems, we propose an ultrasonic-thermal activated attapulgite for use in organic wastewater and its preparation method. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides ultrasonic-thermal activated attapulgite clay for use in organic wastewater and its preparation method, which overcomes the deficiencies of existing technologies, has a reasonable design, a compact structure, and solves existing problems.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing ultrasonically-thermally activated attapulgite soil includes the following steps:

[0009] The first step is raw material pretreatment: the attapulgite ore is crushed, screened to a particle size ≤2mm, and dried at 105℃.

[0010] The second step, ultrasonic treatment: The pretreated attapulgite soil is mixed with water at a solid-liquid ratio of 1:5–1:20 and treated under ultrasonic conditions at a frequency of 40–80 kHz and a power density of 50–150 W / L for 20–60 minutes, with the treatment temperature controlled at 20–60℃.

[0011] The third step is thermal activation: the slurry after ultrasonic activation is filtered, and the resulting solid is calcined at 200–450℃ for 1–3 hours with a heating rate of 5–10℃ / min.

[0012] The fourth step, optional acidification: The thermally activated attapulgite is mixed with a 0.1–0.5 mol / L nitric acid solution and stirred at 20–60°C for 1–2 h, followed by filtration, washing and drying.

[0013] Preferably, the frequency is 50–70 kHz, the power density is 80–120 W / L, and the solid-liquid ratio of the ultrasonic treatment is 1:8–1:15.

[0014] Preferably, the calcination temperature is 300–400°C.

[0015] Preferably, the concentration of the nitric acid solution is 0.15–0.3 mol / L, and the stirring temperature is 25–35°C.

[0016] An activated attapulgite for organic wastewater treatment is prepared by the ultrasonic-thermal activated attapulgite preparation method.

[0017] The application of the activated attapulgite in the simultaneous adsorption of aromatic organic matter and cationic dyes in wastewater includes the following steps:

[0018] Step 1: The activated attapulgite clay is added to the organic wastewater to be treated at a dosage of 0.5–5 g / L as an adsorbent.

[0019] Step 2: Stir and adsorb for 30–120 min at 20–40℃ and pH 3–10, utilizing the synergistic effect of the acidic sites and hierarchical pore structure on the surface of the activated attapulgite to simultaneously adsorb and remove aromatic organic matter and cationic dyes.

[0020] Step 3: After adsorption is complete, solid-liquid separation is performed.

[0021] Preferably, after solid-liquid separation in step three, the separated saturated adsorbent is calcined and regenerated at 300–500°C and reused in the adsorption process.

[0022] Preferably, the aromatic organic pollutant includes phenol or aniline, and the cationic dye pollutant includes methylene blue.

[0023] Preferably, the dosage of the adsorbent is 1–3 g / L, and the adsorption time is 45–90 min.

[0024] This invention provides ultrasonic-thermal activated attapulgite for use in organic wastewater and its preparation method. It has the following beneficial effects:

[0025] This invention employs a specific sequence of ultrasonic activation followed by thermal activation. The ultrasonic cavitation effect preferentially strips fiber bundles and opens primary pores, creating a more open and uniform initial structure for subsequent thermal activation. This allows for a deeper and more thorough process of removing impurities (such as structured water and organic matter) through thermal activation. The synergy of these two methods avoids the pore closure or structural sintering that may result from single thermal activation, thereby constructing a well-developed hierarchical porous structure dominated by mesopores.

[0026] By using an optional low-concentration nitric acid acidification step, amorphous impurities can be selectively dissolved without severely damaging the existing hierarchical framework structure, and surface acidic sites (such as -Si-OH2⁺, -Al-OH, etc.) can be effectively introduced; thus, the final product has both physical adsorption (relying on hierarchical pores) and chemical adsorption (relying on acidic sites) capabilities.

[0027] The activated attapulgite prepared by this method has acidic sites on its surface that have a specific affinity for aromatic organic compounds (such as phenol and aniline), while its hierarchical channels have a strong retention and containment capacity for cationic dyes (such as methylene blue). Therefore, the material of this invention is particularly suitable for the simultaneous adsorption and removal of aromatic organic compounds and cationic dyes coexisting in wastewater, solving the problem of low treatment efficiency of single-function adsorbents for complex pollutant systems.

[0028] This material maintains excellent adsorption performance over a wide pH range (3-10), and its adsorption capacity for typical pollutants such as phenol, aniline, and methylene blue can reach more than 100 mg / g, which is much higher than that of unactivated soil.

[0029] The entire preparation process does not require the use of strong corrosive acids or complex organic modifiers, and the process is green and mild. In addition, the material after adsorption saturation can be regenerated by simple high-temperature calcination. Its stable thermal structure ensures that the adsorption performance decay rate is low after regeneration, and it can be reused, which significantly reduces operating costs. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] A method for preparing ultrasonically-thermally activated attapulgite soil includes the following steps:

[0032] The first step is raw material pretreatment: crush and screen the attapulgite ore to a particle size ≤2mm, and dry it at 105℃ (e.g., dry for 4-12 hours to fully remove surface free water and some adsorbed water).

[0033] The second step is ultrasonic activation: the pretreated attapulgite soil is mixed with water at a solid-liquid ratio of 1:5–1:20 and treated under ultrasonic conditions of 40–80kHz frequency and 50–150W / L power density for 20–60 minutes, with the treatment temperature controlled at 20–60℃ (the ultrasonic treatment effectively removes the agglomerated rod crystal bundles in the attapulgite soil through cavitation effect and mechanical vibration, so that the fibers are dispersed and the internal channels are initially expanded).

[0034] The third step is thermal activation: the slurry after ultrasonic activation is filtered (or centrifuged), and the resulting solid is calcined at 200–450℃ for 1–3 hours at a heating rate of 5–10℃ / min (this heating rate helps the structure to dehydrate and transform gradually, and avoids the collapse of the pores due to rapid heating).

[0035] The fourth step, optional acidification: The thermally activated attapulgite is mixed with a 0.1–0.5 mol / L nitric acid solution (solid-liquid ratio of 1:10–1:30), stirred at 20–60°C for 1–2 h, then filtered, washed (until the filtrate is nearly neutral) and dried (the acidification treatment can dissolve some surface impurities and introduce or enhance surface acidic sites, while basically maintaining the pore structure established by the previous steps).

[0036] The frequency is 50–70kHz, the power density is 80–120W / L, and the solid-liquid ratio of the ultrasonic treatment is 1:8–1:15 (this combination of parameters can achieve a balance between energy efficiency and dispersion effect while ensuring effective cavitation intensity).

[0037] The calcination temperature is 300–400℃ (this temperature range can effectively remove interlayer water, some crystal water and organic impurities, and promote the formation of a stable porous structure).

[0038] The concentration of the nitric acid solution is 0.15–0.3 mol / L, and the stirring temperature is 25–35℃ (this mild condition can effectively modify the surface while protecting the material's skeletal structure to the greatest extent).

[0039] An activated attapulgite for organic wastewater treatment is prepared by the ultrasonic-thermal activated attapulgite preparation method described above.

[0040] The application of activated attapulgite in the simultaneous adsorption of aromatic organic matter and cationic dyes in wastewater, wherein the wastewater contains at least aromatic organic matter (such as phenol and aniline) and cationic dyes (such as methylene blue); the method of application includes the following steps:

[0041] Step 1: The activated attapulgite is used as an adsorbent and added to the organic wastewater to be treated at a dosage of 0.5–5 g / L (the dosage can be adjusted within this range according to the initial concentration of the wastewater).

[0042] Step 2: Stir and adsorb at 20–40℃ and pH 3–10 for 30–120 min (utilizing the affinity of the acidic sites on the surface of the activated attapulgite for aromatic organic compounds, and the retention and electrostatic adsorption of cationic pollutants by the hierarchical pore structure to achieve simultaneous removal of the two types of pollutants).

[0043] Step 3: After adsorption is complete, solid-liquid separation is performed by sedimentation, centrifugation, or filtration.

[0044] The aromatic organic compound includes phenol or aniline, and the cationic dye includes methylene blue.

[0045] The dosage of the adsorbent is 1–3 g / L, and the stirring adsorption time is 45–90 min.

[0046] After solid-liquid separation in step three, the separated saturated adsorbent is calcined at 300–500°C (in air or an inert atmosphere) to regenerate (e.g., calcination for 0.5–2 hours to remove adsorbed organic matter), and can be reused in subsequent adsorption processes (the regeneration benefits from the stable structure formed by the high-temperature thermal activation step of the material).

[0047] Example 1: Weigh 100g of attapulgite ore, crush it and sieve it, take particles with a particle size ≤2mm, and dry them in an oven at 105℃ for 4 hours;

[0048] The dried attapulgite was mixed with 1000 mL of deionized water (solid-liquid ratio 1:10) and placed in an ultrasonic reactor. The mixture was ultrasonically treated for 40 minutes at a frequency of 60 kHz, a power density of 100 W / L, and a temperature of 40 °C. After treatment, the mixture was filtered, and the filter cake was placed in a muffle furnace and heated to 350 °C at a programmed rate of 8 °C / min, and then calcined at this temperature for 2 hours. After cooling, the calcined soil was mixed with 0.2 mol / L nitric acid solution at a solid-liquid ratio of 1:20 and stirred at 30 °C for 1 hour. The mixture was then filtered, washed with deionized water until the filtrate was neutral, and finally dried at 105 °C for 6 hours to obtain activated attapulgite S1.

[0049] Prepare a phenol-simulated wastewater with an initial concentration of 100 mg / L, and adjust the pH to 7.0 with NaOH or HCl; add 100 mL of this wastewater to a 250 mL Erlenmeyer flask, and add 0.20 g of activated attapulgite S1 (dosage 2 g / L); place it in a constant temperature shaker and shake and adsorb at 30 °C and 150 rpm for 60 minutes; take a sample, filter, and determine the phenol concentration in the filtrate.

[0050] Example 2: Activated attapulgite S1 was prepared according to the method in Example 1; a mixed simulated wastewater containing phenol and methylene blue was prepared, with an initial concentration of phenol of 60 mg / L and an initial concentration of methylene blue of 40 mg / L, and the pH was adjusted to 6.0. 100 mL of this mixed wastewater was taken, and 0.15 g of activated attapulgite S1 (dosage 1.5 g / L) was added. The mixture was shaken and adsorbed at 30℃ and 150 rpm for 90 minutes; after adsorption, samples were taken and filtered, and the residual concentrations of phenol and methylene blue in the filtrate were determined.

[0051] Example 3: Activated attapulgite S1 was prepared according to the method in Example 1; 1.0 g of S1 was used to adsorb 200 mL of aniline wastewater with an initial concentration of 80 mg / L (pH=5.0), and the adsorption was saturated at 35 °C. The saturated adsorbent was recovered by filtration, placed in a muffle furnace, and calcined at 400 °C at a rate of 10 °C / min in air atmosphere for 1 hour. After cooling, regenerated adsorbent S1-R was obtained; using regenerated adsorbent S1-R, adsorption experiments were carried out again under the same conditions (1.0 g adsorbent, 200 mL of 80 mg / L aniline wastewater, 35 °C).

[0052] Comparative Example 1: Attapulgite ore that has only been crushed, sieved (≤2mm) and dried at 105℃ was used as adsorbent R1; adsorption experiments were conducted using adsorbent R1 under the exact same conditions as in Example 1 (100mg / L phenol, pH=7.0, dosage 2g / L, adsorption at 30℃ for 60min).

[0053] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing ultrasonically-thermally activated attapulgite, characterized in that, Includes the following steps: The first step is raw material pretreatment: crush and screen the attapulgite ore to a particle size ≤2mm, and dry it at 105℃; The second step, ultrasonic treatment: The pretreated attapulgite soil is mixed with water at a solid-liquid ratio of 1:5–1:20 and treated under ultrasonic conditions at a frequency of 40–80 kHz and a power density of 50–150 W / L for 20–60 minutes, with the treatment temperature controlled at 20–60℃. The third step is thermal activation: the slurry after ultrasonic activation is filtered, and the resulting solid is calcined at 200–450℃ for 1–3 hours with a heating rate of 5–10℃ / min. The fourth step, optional acidification: The thermally activated attapulgite is mixed with a 0.1–0.5 mol / L nitric acid solution and stirred at 20–60°C for 1–2 h, followed by filtration, washing and drying.

2. The method according to claim 1, characterized in that, The frequency is 50–70 kHz, the power density is 80–120 W / L, and the solid-liquid ratio of the ultrasonic treatment is 1:8–1:

15.

3. The method according to claim 1, characterized in that, The calcination temperature is 300–400℃.

4. The method according to claim 1, characterized in that, The concentration of the nitric acid solution is 0.15–0.3 mol / L, and the stirring temperature is 25–35℃.

5. An activated attapulgite clay for treating organic wastewater, characterized in that, Prepared by the method according to any one of claims 1 to 4.

6. The application of the activated attapulgite clay according to claim 5 in the simultaneous adsorption of aromatic organic matter and cationic dyes in wastewater, characterized in that, Includes the following steps: Step 1: The activated attapulgite clay is added to the organic wastewater to be treated at a dosage of 0.5–5 g / L as an adsorbent. Step 2: Stir and adsorb for 30–120 min at 20–40℃ and pH 3–10, utilizing the synergistic effect of the acidic sites and hierarchical pore structure on the surface of the activated attapulgite to simultaneously adsorb and remove aromatic organic matter and cationic dyes. Step 3: After adsorption is complete, solid-liquid separation is performed.

7. The application according to claim 6, characterized in that, After solid-liquid separation in step three, the separated saturated adsorbent is calcined and regenerated at 300–500°C and reused in the adsorption process.

8. The application according to claim 6, characterized in that, The aromatic organic pollutants include phenol or aniline, and the cationic dye pollutants include methylene blue.

9. The application according to claim 6, characterized in that, The adsorbent dosage is 1–3 g / L, and the adsorption time is 45–90 min.