A balloon-borne device and method for adsorbing polystyrene microplastics in water using argillaceous limestone

Abstract

The present invention belongs to the field of water treatment, and more specifically relates to a spherical device and method for adsorbing polystyrene microplastics in water using argillaceous limestone. In order to solve the problems of complex types of microplastics in the water environment and the difficulty in reuse and degradation, the present invention develops a technology for removing microplastics with low cost and high efficiency. By using argillaceous limestone with strong adsorption performance and fixing it in the spherical device, the polystyrene plastics in water can be efficiently and rapidly removed by the adsorption method, realizing water purification. The spherical device of the present invention has the advantages of simple structure, convenient use, low cost, good adsorption performance, recyclability, etc. Compared with the prior art, the device of the present invention has extremely high adsorption performance for polystyrene microplastics and can be conveniently recycled.

Description

Technical Field

[0001] The present invention relates to the field of water treatment, and more particularly to a spherical device and method for adsorbing polystyrene microplastics in water using argillaceous limestone. Background Art

[0002] As a new pollutant widely concerned internationally and defined by the Ministry of Ecology and Environment of the country, microplastics are small in particle size and difficult to degrade, posing a serious threat to aquatic organisms and human health. Water body microplastic pollution has become a global environmental problem. The removal technologies of microplastics in water environment mainly include: traditional physical separation (sedimentation, filtration, adsorption and flotation), chemical removal (advanced oxidation and coagulation), biological removal (biofilm separation and biodegradation) and emerging electrocoagulation removal technology. Adsorption method in physical removal, as a removal method with low cost, easy operation and high removal rate, is recognized as an important method for wastewater treatment.

[0003] Due to its relatively rich charge, strong bond energy and large specific surface area, argillaceous limestone has a large adsorption performance for positively charged pollutants in water environment purification. And argillaceous limestone, as an associated ore of limestone, is usually stacked as waste in the mining area during its mining process, and the waste stacking has become an environmental problem after mining. However, the adsorption technology based on argillaceous limestone for adsorbing microplastics has not been reported so far.

[0004] Moreover, most of the currently authorized microplastic adsorption technologies focus on adding adsorption materials into wastewater and pay attention to the research on improving adsorption performance, rarely involving recycling. For example, CN202111305954.X discloses a method for synchronously removing microplastics and quinolone antibiotics in water, and CN201910860438.X discloses a method for adsorbing polystyrene microplastics in water using three-dimensional graphene, neither of which mentions recycling the adsorption materials. And for the few technologies involving recycling, such as: CN202310400007.1 discloses a magnetic sponge carbon for adsorbing microplastics, its preparation method and application. Although it mentions that the magnetic sponge carbon can be quickly separated from liquid samples, the separation technology is not elaborated in detail.

[0005] Based on this, in order to solve the above problems, the present invention provides a microplastic adsorption material based on argillaceous limestone with simple conditions, low cost, good adsorption performance, recyclability, and turning waste into treasure. This adsorption material has ultra-high adsorption performance for polystyrene microplastics, stable chemical properties and broad application prospects. Summary of the Invention

[0006] To solve the problem that the types of microplastics in the water environment are complex and difficult to recycle and degrade, the present invention develops a low-cost and efficient technology for removing microplastics. By using argillaceous limestone with strong adsorption performance, the polystyrene plastics in water are efficiently and rapidly removed through the adsorption method to achieve water purification.

[0007] The technical solution of the present invention is as follows:

[0008] A spherical device for adsorbing polystyrene microplastics in water using argillaceous limestone, the outer shell of which is a hollow hard sphere, is formed by connecting two hemispheres through a number of movable slots. A number of support rods are fixed inside the sphere, and the argillaceous limestone wrapped by a soft net is placed inside the sphere. The argillaceous limestone wrapped by the soft net is fixed by the support rods.

[0009] Preferably, the materials of the hollow hard sphere, the support rods, and the soft net are all aluminum alloy. Aluminum alloy does not contain microplastic particles and will not cause secondary pollution; it has a low density but relatively high strength; it has good plasticity and can be processed into various profiles; it has excellent corrosion resistance.

[0010] Preferably, the argillaceous limestone is selected from the Mantou Formation in Dabeiwangdi, Jiangsu, China, where there is a mixed sedimentation phenomenon of carbonate and terrigenous clastics, and its surface is rich in negative charges.

[0011] The spherical device is prepared through the following steps:

[0012] Step (1): Using a hard aluminum alloy hollow sphere as the carrier, the sphere is evenly divided into two halves. A number of movable slots are evenly installed at the fracture of the sphere as the switch for opening and closing the sphere, and aluminum alloy support rods are fixed inside the sphere.

[0013] Step (2): Select a soft aluminum alloy net to wrap the argillaceous limestone. After wrapping, use filamentous aluminum alloy to seal the mouth of the soft aluminum alloy net.

[0014] Step (3): Put the soft aluminum alloy net ball sealed in step 2 into the hard aluminum alloy sphere in step 1 and fix it through the aluminum alloy support rods to obtain the adsorption spherical device.

[0015] Preferably, the diameter of the hard aluminum alloy hollow sphere in step (1) is 5 - 10 cm. More preferably, the diameter of the hard aluminum alloy hollow sphere is 7 cm.

[0016] Preferably, the surface of the hard aluminum alloy hollow sphere in step (1) is porous, and the pore diameter is 0.10 - 0.020 mm. More preferably, the pore diameter on the surface of the hard aluminum alloy hollow sphere is 0.015 mm.

[0017] Preferably, the number of movable slots of the hard aluminum alloy hollow sphere in step (1) is 4 - 7. More preferably, the number of movable slots is 5.

[0018] Preferably, the support rod in step (1) has a length of 0.8 - 1.2 cm and a diameter of 0.7 - 0.9 cm. More preferably, the support rod has a length of 1 cm and a diameter of 0.8 cm.

[0019] Preferably, the aperture of the soft aluminum alloy mesh in step (2) is 0.030 - 0.045 mm. More preferably, the aperture of the soft aluminum alloy mesh is 0.038 mm.

[0020] Dolomite with a particle size of 0.15 - 0.25 mm shows excellent effects in improving soil pH and releasing nutrients. Therefore, the preferred aperture of the soft aluminum alloy mesh should be less than 0.15 mm. Since more than 95% of the particles of argillaceous limestone passing through a 0.15 mm sieve after grinding have a particle size greater than 0.038 mm. To reduce material loss, the present invention selects 0.038 mm as the preferred aperture of the soft aluminum alloy mesh.

[0021] A method for adsorbing polystyrene microplastics in water using argillaceous limestone (which is essentially a method for wastewater treatment), directly placing the adsorption sphere carrier device in wastewater containing polystyrene microplastics. Preferably, perform oscillating treatment with an oscillation speed of 150 - 250 rpm and a treatment time of 12 - 36 hours; Optionally, further include the step of recovering the sphere carrier device, further treating the sphere carrier device with an NaCl solution, specifically oscillating in a thermostatic oscillator at 150 - 250 rpm and 25 ± 3 °C in the dark for 12 - 36 h until complete desorption equilibrium is reached for reuse, and reused 1 - 5 times.

[0022] Preferably, the pH value of the adsorbed wastewater is 5 - 7. The reason is that the pH of acidic wastewater widely existing in the environment is less than 6.0, and argillaceous limestone has strong adsorption performance for positively charged cations under the condition of pH 6.0.

[0023] The mass of the argillaceous limestone wrapped in each adsorption sphere carrier device is relatively determined, and the mass of the sphere - carried argillaceous limestone is changed by changing the number of adsorption sphere carrier devices.

[0024] Preferably, after the hard aluminum alloy hollow small balls filled with argillaceous limestone reach saturation in adsorbing polystyrene microplastics in wastewater, they are recovered by the filtration recovery method, and then desorbed with a specific desorbent (such as 5% NaCl solution), and the adsorption small balls can be regenerated and recycled.

[0025] The technical solution of the present invention has the following beneficial effects compared with the prior art: The present invention discovers for the first time that argillaceous limestone can efficiently remove microplastics, and mainly adsorbs polystyrene microplastics in wastewater through electrostatic adsorption and complexation. The spherical device of the present invention has the advantages of simple structure, convenient use, low cost, good adsorption performance, recyclability, etc. Compared with the prior art, the device of the present invention has extremely high adsorption performance for polystyrene microplastics and can be conveniently recycled. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 . Schematic diagram of the adsorption of polystyrene microplastics in water by spherical argillaceous limestone and the cross-section of the device;

[0027] Figure 2 . Influence of environmental factors on the adsorption of amino polystyrene microplastics (NPS) on argillaceous limestone (AL) ((a) ionic strength, (b) DBP, and (c) HA);

[0028] Figure 3 . XPS spectra of AL before and after adsorbing NPS.

[0029] Figure 4 . Results of the adsorption performance comparison test. DETAILED DESCRIPTION OF THE INVENTION

[0030] The following further elaborates on the technical solution of the present invention and the technical effects it produces in combination with the specific embodiments. The following description is only for explaining the present invention and does not limit the present invention in any way. Any transformation or substitution based on the teachings of the present invention belongs to the protection scope of the present invention. Unless otherwise specified, the methods described in the present invention are conventional methods in the art. Unless otherwise specified, the reagents used can be obtained from commercial sources.

[0031] Example 1. Preparation of the spherical device

[0032] Step (1): Use a hard-state aluminum alloy hollow sphere as the carrier. The diameter of the sphere is 7 cm, and the surface pore diameter of the sphere is 0.15 mm. Divide the sphere into two equal parts on average, and evenly install 5 movable card slots at the fracture of the sphere as the switch for opening and closing the sphere; Fix an aluminum alloy support rod inside the sphere. The length of the support rod is 1 cm, and the diameter is 0.8 cm;

[0033] Step (2): Select a soft-state aluminum alloy mesh with a pore diameter of 0.038 mm to wrap the argillaceous limestone. After wrapping, use a filamentous aluminum alloy to seal the mouth of the soft-state aluminum alloy mesh;

[0034] Step (3): Put the sealed soft-state aluminum alloy mesh ball into the hard-state aluminum alloy sphere, and fix it through the aluminum alloy support rod (see Figure 1 ).

[0035] Example 2. Adsorption Test of Polystyrene Microplastics on Ball-Borne Device

[0036] (1) Thermodynamic Adsorption

[0037] All adsorption experiments were carried out in 50 mL blue-capped glass bottles: Different concentrations of polystyrene microplastic solutions were pre-prepared with deionized water, and the initial pH value of the background solution was adjusted to 6.0 ± 0.1 with 0.1 mol / L NaOH and HNO3 in advance. The ball-borne devices prepared in Example 1 (i.e., containing ball-borne argillaceous limestone) with different solid-liquid ratios (0, 20, 40, 60, 80, 100 mg / L) were placed in 50 mL blue-capped glass bottles, 15 mL of polystyrene microplastic solution was added, and they were shaken in the dark at 180 rpm and 25 ± 3 °C in a constant temperature oscillator for 24 h. Then the ball-borne argillaceous limestone was taken out, and the concentration of polystyrene microplastics in the supernatant was analyzed.

[0038] Note: The mass of the ball-borne devices prepared in Example 1 in the adsorption test refers to the mass of pure argillaceous limestone.

[0039] (2) Kinetic Adsorption

[0040] The kinetic adsorption test of the ball-borne devices prepared in Example 1 on polystyrene microplastics was carried out under the conditions of pH = 6.0 and 25 ± 3 °C. 0.50 mg of ball-borne argillaceous limestone was taken in a 50 mL blue-capped glass bottle, 15 mL of 20 mg / L polystyrene microplastic solution was added, and after shaking for several time gradients (0, 1, 3, 5, 8, 10, 15, 20, 25, 30, 40, 50, 60, 75, 90, 120, 150, 180, 240, 360, 720, 1440 and 2880 min) in a constant temperature oscillator, the ball-borne argillaceous limestone was taken out, and the concentration of polystyrene microplastics in the supernatant was analyzed.

[0041] (3) Analysis of Adsorption Mechanism

[0042] The argillaceous limestone before and after adsorbing polystyrene microplastics was characterized by XPS to clarify the adsorption mechanism of argillaceous limestone on polystyrene plastics.

[0043] (4) Analysis of Experimental Results

[0044] Figure 2 Effects of environmental factors on the adsorption of NPS on AL (ionic strength (a), dibutyl phthalate (DBP) (b), and humic acid (HA) (c)). The data are mean ± standard deviation (n = 3 in figures a and b), and the letters (A, B, C, etc.) above each column are statistically significant at P < 0.05.

[0045] Figure 2The results show that the influence of coexisting ions on the adsorption of NPS on AL is as Figure 2 shown in a of the figure. When there are different concentrations of Na + in the background solution, within the concentration range of 0.003 - 0.2 mol / L, the adsorption amount of NPS on AL decreases significantly with the increase of Na + concentration, from 368.95 mg / g to 296.83 mg / g; within the concentration range of 0.2 - 0.6 mol / L, the adsorption amount of NPS on AL increases significantly with the increase of Na + concentration, from 296.83 mg / g to 349.71 mg / g. When there are different concentrations of Ca 2+ in the background solution, within the concentration range of 0.003 - 0.6 mol / L, the adsorption amount of NPS on AL shows no significant change, but when the Ca 2+ concentration is 0.01 mol / L, NPS has the minimum adsorption amount on AL, 323.62 mg / g; when the Ca 2+ concentration is 0.2 mol / L, NPS has the maximum adsorption amount on AL, 351.07 mg / g. When there are different concentrations of Fe 3+ in the background solution, when the Fe 3+ concentrations are 0.003 and 0.4 mol / L respectively, they significantly promote and inhibit the adsorption of NPS on AL, and their maximum and minimum adsorption amounts are 407.50 and 362.01 mg / g respectively. When the ion concentration is 0.003 mol / L, compared with Na + and Ca 2+ , Fe 3+ shows an obvious promoting effect on the adsorption of NPS on AL; when the ion concentrations are 0.1 and 0.2 mol / L, compared with Ca 2+ and Fe 3+ , Na + shows an obvious inhibitory effect on the adsorption of NPS on AL, while in other concentration treatments, Na + has a promoting effect. Generally speaking, the adsorption of NPS on AL is affected by the ionic strength of different valences, among which the promoting or inhibitory effect of monovalent Na + is the most significant; trivalent Fe 3+ has a certain promoting effect at low concentrations, but the effect is not significant; divalent Ca 2+ has almost no effect.

[0046] The influence of DBP on the adsorption of NPS on AL is as Figure 2As shown in b. When there are different concentrations of DBP in the background solution, as the DBP concentration increases from 0.005 mol / L to 0.8 mol / L, the adsorption amount of NPS on AL increases from 143.65 mg / g to 349.95 mg / g. The influence of HA on the adsorption of NPS on AL is as shown in Figure 2 c. When there are different concentrations of HA in the background solution, at low concentrations (0.5 - 0.2 mol / L), the adsorption amount of NPS on AL decreases significantly with the increase of HA concentration, from 354.16 mg / g to 336.24 mg / g; at high concentrations (5 - 20 mol / L), the adsorption amount of NPS on AL increases significantly with the increase of HA concentration, from 379.68 mg / g to 618.90 mg / g. Generally speaking, the adsorption of NPS on AL is significantly affected by environmental factors DBP and HA, among which DBP has a significant promoting effect; HA has a certain inhibitory effect at low concentrations and a significant promoting effect at high concentrations.

[0047] Figure 3 is the full XPS spectrum of AL before and after adsorbing NPS. The results show that: a new characteristic peak N1S (399 eV) appears after AL adsorbs NPS. The peak at 399 eV is the N atom bonded to the sp2 hybridized C atom (C≡N group); the signal intensity of the characteristic peak C1S (285 eV) is enhanced after AL adsorbs NPS. C 1S (285 eV) belongs to the carbon bonded to one nitrogen. The changes of both fully indicate that the C≡N group may be involved in the adsorption process of AL to NPS, and this group has a strong polarity.

[0048] Table 1. Fitting parameters of Langmuir and Freundlich adsorption isotherms of AL in NPS solution

[0049]

[0050] Table 1 shows the Langmuir and Freundlich adsorption isotherm parameters of AL in NPS solution. The results show that: from the fitting parameters (Table 1), it can be seen that the correlation coefficient (R 2 = 0.962) of the Freundlich model is higher than that of the Langmuir model (R 2 = 0.584). Therefore, the adsorption of NPS conforms more to the Freundlich model. The maximum adsorption amount of NPS fitted by the Freundlich model is 408 mg / g. In addition, the separation factor R L value has been widely used to determine the characteristics of the adsorption process. When R L = 0, the isothermal adsorption is irreversible adsorption. When 0 < R L < 1, it is favorable adsorption. When R LWhen R = 1, it is linear adsorption. When R L > 1, it is not conducive to isothermal adsorption. In the experiment, R L is in the range of 0.00485 - 0.718, which proves that the AL adsorbent has a good adsorption effect on NPS.

[0051] Table 2. Fitting parameters of the adsorption kinetic model of AL in NPS solution

[0052]

[0053] Table 2 shows the adsorption kinetic parameters of AL in NPS solution. The results in Table 2 indicate that in order to better understand the adsorption behavior of AL on NPS, the experimental data of AL adsorbing NPS were fitted with two kinetic models (pseudo-first-order kinetic model and pseudo-second-order kinetic model). Table 2 shows the parameters obtained by fitting the two kinetic adsorption models. The correlation coefficient (R 2 = 0.366) of the pseudo-first-order kinetic model is less than the correlation coefficient (R 2 = 0.999) of the pseudo-second-order kinetic model, indicating that the adsorption behavior of AL on NPS conforms to the pseudo-second-order kinetic model. The K value (K1 = -3.67×10-4) of the pseudo-first-order kinetic model is less than the K value (K2 = 0.00134) of the pseudo-second-order kinetic model, indicating that the adsorption of NPS on AL is completed in a short time.

[0054] Example 3. Adsorption performance comparison test

[0055] A comparative test on the adsorption performance of commercially available common materials was carried out.

[0056] The solution composition of polystyrene microplastics: pure water and polystyrene

[0057] According to the chemical properties and surface charge differences of environmental minerals, montmorillonite (Mon), hematite (HM), kaolinite (Kao), and argillaceous limestone (AL, the spherical device prepared in Example 1) were selected as adsorption materials. The point adsorption test of 4 environmental minerals on NPS was carried out under the conditions of pH = 6.0 and 25 ± 3°C. Weigh different solid-liquid ratios of 4 environmental minerals into 50 mL blue-capped glass bottles, add 15 mL NPS (1, 10, and 50 mg / L) solutions corresponding to the concentration ratios of the minerals, and oscillate in the dark at 180 rpm and 25 ± 3°C in a constant temperature oscillator (HJ / T 637 - 2012) for 24 h to reach complete equilibrium. Subsequently, the supernatant was filtered through a 0.22 μm organic phase filter head to remove larger particles, and the filtrate was diluted and the NPS concentration was measured with a fluorescence spectrophotometer (Fluorolog-3, USA). To eliminate the influence of the background solution, the experiment was set up with three replicates and blank correction was carried out. The removal rate was calculated by the following formula:

[0058]

[0059] where C0 and C e are the initial NPS concentration (mg / L) and the final NPS concentration (mg / L), respectively.

[0060] The test results show that ( Figure 4 ):

[0061] The NPS removal rate of Mon is 70%;

[0062] The NPS removal rate of HM is 76%;

[0063] The NPS removal rate of Kao is 81%;

[0064] The results show that: under the same conditions, the NPS removal rate of the main adsorbent material argillaceous limestone (AL) in the spherical carrier device is 84%. It can be seen that the spherical carrier device prepared by the present invention has a better NPS removal rate than commercially available conventional products. The reason may be that: compared with conventional products such as Kao and Mon, AL has relatively rich negative charges and functional groups.

[0065] Example 4. Comparative test on recycling

[0066] The spherical carrier device prepared in Example 1 that has been saturated with adsorbed NPS microplastics is treated with 5% NaCl solution and shaken in the dark at 180 rpm and 25 ± 3 °C in a constant temperature oscillator (HJ / T 637-2012) for 24 h to reach complete desorption equilibrium. After the desorption process is completed, the supernatant is transferred to a quartz cuvette, and the NPS concentration is measured with a fluorescence spectrophotometer (Fluorolog-3, USA). The desorption rate is determined according to the difference in the absorbance of NPS particles in the supernatant before and after desorption. According to the above adsorption-desorption test conditions, after 4 cycles, the recyclability of the spherical carrier device prepared in Example 1 loaded with argillaceous limestone is clarified to reduce costs.

[0067] The results show that: after 4 cycles, the desorption rate of NPS on the surface of the small balls of the spherical carrier device prepared in Example 1 can reach 90%, indicating good recyclability.

Claims

1. A balloon-borne device using argillaceous limestone to adsorb polystyrene microplastics in water, characterized in that, Its outer shell is a hollow hard sphere, which is formed by connecting two hemispheres through movable clamping grooves. A support rod is fixed inside the sphere, and argillaceous limestone wrapped by a soft net is placed inside the sphere. The argillaceous limestone wrapped by the soft net is fixed by the support rod; the materials of the hollow hard sphere, the support rod, and the soft net are all aluminum alloy; the diameter of the hard aluminum alloy hollow sphere is 5-10 cm; the surface of the hard aluminum alloy hollow sphere is porous, and its pore diameter is 0.15 mm; the pore diameter of the soft aluminum alloy net is 0.030-0.045 mm; the number of movable clamping grooves of the hard aluminum alloy hollow sphere is 4-7; the length of the support rod is 0.8-1.2 cm, and the diameter is 0.7-0.9 cm.

2. The airborne device according to claim 1, characterized in that, The spherical carrier device is prepared through the following steps: Step (1): Use a hard aluminum alloy hollow sphere as the carrier, divide the sphere into two equal parts on average, evenly install movable clamping grooves at the fracture of the sphere as the switch for opening and closing the sphere, and fix an aluminum alloy support rod inside the sphere; Step (2): Select a soft aluminum alloy net to wrap the argillaceous limestone. After wrapping, seal the mouth of the soft aluminum alloy net with filamentous aluminum alloy; Step (3): Put the soft aluminum alloy net ball with the sealed mouth in step (2) into the hard aluminum alloy sphere in step (1), and fix the soft aluminum alloy net ball through the aluminum alloy support rod to obtain the adsorption spherical carrier device.

3. The airborne device according to claim 1, characterized in that The diameter of the hard aluminum alloy hollow sphere is 7 cm.

4. The airborne device according to claim 1, characterized in that, The number of movable clamping grooves is 5.

5. The airborne device according to claim 1, characterized in that, The length of the support rod is 1 cm, and the diameter is 0.8 cm.

6. The airborne device according to claim 1, characterized in that, The pore diameter of the soft aluminum alloy net is 0.038 mm.

7. A treatment method for adsorbing polystyrene microplastics in water using argillaceous limestone, characterized in that, Place the spherical carrier device according to any one of claims 1-6 directly into the wastewater containing polystyrene microplastics, and perform oscillation treatment. The oscillation speed is 150-250 rpm, and the treatment time is 12-36 hours.

8. The method according to claim 7, wherein It also includes the step of recycling the spherical carrier device. Treat the spherical carrier device with NaCl solution, and oscillate it in a constant temperature oscillator at 150-250 rpm and 25±3°C in the dark for 12-36 h until complete desorption equilibrium is reached, so that it can be reused, and the reuse times are 1-5 times.

9. The method according to claim 7, characterized in that The pH value of the adsorbed wastewater is 5-7.

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