Biogenic amorphous calcium carbonate for dye wastewater treatment and its preparation method and application

Abstract

The present invention belongs to the technical field of environmental governance, and specifically relates to a biogenic amorphous calcium carbonate for dye wastewater treatment, and a preparation method and application thereof. Bacillus licheniformis LRL007 is inoculated into a liquid culture medium containing a soluble inorganic calcium salt for cultivation to obtain the biogenic amorphous calcium carbonate; the Bacillus licheniformis LRL007 has been deposited in the General Microbiology Center of the China Committee for the Collection of Microorganisms on January 10, 2022, with a deposit number of CGMCC No. 24275. The preparation method of the present invention is economical and environmentally friendly, simple to operate, and no toxic or harmful substances are added during the synthesis process, and no secondary pollution will be caused; the obtained amorphous calcium carbonate has good stability, a well-developed porous structure and good organic dye adsorption and anti-interference ability. At the same time, its pH applicability range is wide, and it can be recycled at least 8 times or more, and has good application prospects in the treatment of organic dye wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental governance, and particularly relates to a biogenic amorphous calcium carbonate for dye wastewater treatment, and a preparation method and application thereof. Background Art

[0002] The production and use of various dyes such as disperse dyes, acid dyes, anionic dyes and sulfur dyes generate a large amount of dye wastewater. The printing and dyeing industry is a major emitter of industrial wastewater. These dye wastewaters have complex and very stable components, with dark colors visible to the naked eye, strong acidity and alkalinity, and "three-hazard" effects. Congo Red (CR, C 32 H 22 N6Na2O6S2) is a typical anionic diazo dye, primarily used in the plastics, paper, textile, printing, and dyeing industries. CR, a water-soluble benzidine-based azo dye with a complex structure, is not only carcinogenic and mutagenic to organisms but also extremely harmful to the natural environment. Direct release into ecosystems poses serious environmental and health risks. Furthermore, due to the high biodegradability of CR compounds, they are difficult to effectively remove through water purification and are difficult to effectively degrade using conventional treatment methods.

[0003] Nowadays, adsorption is a simple and easy method for treating organic dye wastewater. It has the following advantages: simple equipment and instruments, convenient and fast operation, no side reactions, etc. In addition, the adsorption process is simple and easy to operate, and has good practicality. Therefore, it has been widely used in wastewater treatment. The key to this technology is the adsorption material. Although a variety of materials have been developed as dye adsorbents to date, such as polymers, zeolites, clays, carbon nanotubes and activated carbon, the selection is still very limited. At the same time, there are also common problems such as low adsorption capacity, high cost, difficulty in reuse, and significant influence of environmental factors such as pH, temperature, time, coexisting ions and humic acid. As a result, the removal effect of these existing dye adsorption materials in actual wastewater applications is very unsatisfactory, making it difficult to promote and apply them on a large scale. With the intensification of organic dye pollution and the increasingly stringent sewage discharge standards, the development of a new, low-cost adsorption material that can efficiently remove organic dyes from sewage has important positive significance for the restoration of water ecology and is also conducive to the recycling of water resources. Although there have been some applied studies on the adsorption of CR by calcium carbonate to date, there are few reports on the adsorption properties of biogenic amorphous calcium carbonate, which seriously restricts the theoretical research and potential applications of biogenic amorphous calcium carbonate.

[0004] Compared to naturally occurring calcium carbonates such as stalactites and limestone, as well as chemically synthesized calcium carbonate, amorphous calcium carbonate prepared by microbial induced mineralization offers unique advantages. Its porous surface and abundant reactive groups make it suitable as an adsorption material. While microorganisms utilize their synthesized amorphous calcium carbonate to adsorb and remove organic dyes from wastewater, they also promote the metabolism of polluting organic matter, increase the pH of the mineralization system, and facilitate the mineralization reaction. Currently, the preparation of chemically synthesized amorphous calcium carbonate is extremely complex, characterized by poor stability, and high cost. This is because amorphous calcium carbonate is the most unstable form of calcium carbonate minerals. Therefore, its chemical synthesis often requires the addition of large amounts of stabilizers, such as polyvinylpyrrolidone, polyacrylic acid, and highly carboxylated substances, which pose environmental risks. The microbial induced mineralization of amorphous calcium carbonate offers significant advantages, including its simple operation, low cost, and environmental friendliness. Therefore, exploring the biosynthesis of amorphous calcium carbonate and its adsorption properties for organic dyes will help promote the development and application of biogenic amorphous calcium carbonate in the field of organic dye remediation. Microorganisms are ubiquitous in the environment, and many of them can induce the formation of amorphous calcium carbonate. Based on this, we have selected and explored the removal effect of amorphous calcium carbonate induced by different common microbial strains on the organic dye Congo red through a large amount of screening work, and thus determined that the amorphous calcium carbonate induced by the dominant strain Bacillus licheniformis LRL007 has excellent application prospects in the field of dye wastewater treatment. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a biogenic amorphous calcium carbonate for dye wastewater treatment and a preparation method and application thereof, specifically adopting the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing biogenic amorphous calcium carbonate for dye wastewater treatment, comprising the following steps: inoculating Bacillus licheniformis LRL007 into a liquid culture medium containing a soluble inorganic calcium salt for culturing to obtain biogenic amorphous calcium carbonate; the Bacillus licheniformis LRL007 was deposited in the General Microbiology Center of the China Culture Collection Administration on January 10, 2022, with the deposit number CGMCC No. 24275.

[0007] The Bacillus licheniformis LRL007 used in the present invention is highly adaptable, environmentally friendly, and widely distributed in water and soil. It is also a typical functional microbial fertilizer strain commonly used in my country. The Bacillus licheniformis LRL007 used in the above method can produce a large amount of alkaline substances during cultivation, significantly increasing the pH of the solution, thereby promoting the synthesis of amorphous calcium carbonate. This method does not require the addition of an alkaline source or other stabilizers required in traditional methods, effectively reducing preparation costs and being environmentally friendly.

[0008] Preferably, the liquid culture medium is LB medium or beef extract peptone medium; the amount of the soluble inorganic calcium salt added is 1 g / L to 2 g / L. More preferably, the soluble inorganic calcium salt is industrial-grade calcium chloride. This method avoids the need to add additional alkaline sources and other stabilizers required in traditional preparation methods. Furthermore, the soluble inorganic calcium salt is industrial-grade calcium chloride, which is inexpensive and only requires an addition amount of 1 g / L to 2 g / L, significantly reducing costs.

[0009] Preferably, the inoculation process of the above-mentioned Bacillus licheniformis LRL007 is as follows: 2 mL to 5 mL of seed solution is added to every 100 mL to 300 mL of culture medium, and the concentration of Bacillus licheniformis LRL007 in the seed solution is (2.92 ± 0.51) × 10 8 cfu / mL.

[0010] Preferably, the temperature of the above-mentioned culture process is 25° C. to 35° C., and the time is 3 to 7 days. After the culture is completed, the precipitate is centrifuged, dried, ground and sieved to obtain the biogenic amorphous calcium carbonate.

[0011] A second aspect of the present invention provides a biogenic amorphous calcium carbonate prepared by the above-mentioned preparation method for dye wastewater treatment. The mineral element composition of the biogenic amorphous calcium carbonate is 41.7% C, 29.6% O, and 12.4% Ca. The biogenic amorphous calcium carbonate prepared by the present invention has a rough and porous surface, good dispersibility, and well-developed pores, which can remove organic dyes through pore encapsulation. Furthermore, the material is an organic-inorganic composite material with a rich variety of surface functional groups, which can enhance adsorption by forming hydrogen bonds or chemical bonds with dyes.

[0012] A third aspect of the present invention provides the use of the aforementioned biogenic amorphous calcium carbonate for removing organic dyes from wastewater or preparing an organic dye adsorbent. The organic dye is Congo red. The biogenic amorphous calcium carbonate is used in the treatment of organic dye-contaminated wastewater; its maximum adsorption capacity for CR (Congo red) can reach 454.55 mg / g, significantly higher than other common adsorption materials. Furthermore, the aforementioned biogenic amorphous calcium carbonate exhibits broad pH applicability, maintaining good stability and adsorption properties in environments with a pH greater than or equal to 6.0 (CR will change color due to protonation at a pH below 6). The optimal adsorption dose is 2.5 g / L, and equilibrium is reached after approximately 3 hours of adsorption. Furthermore, after eight cycles, it maintains stable and efficient adsorption performance and is virtually unaffected by the influence of various coexisting ions and humic acid, demonstrating its enormous application potential.

[0013] The fourth aspect of the present invention further provides an organic dye adsorbent, which comprises the above-mentioned biogenic amorphous calcium carbonate.

[0014] It should be noted that the Bacillus licheniformis LRL007 used in the present invention belongs to the prior art and has been applied for in patent application number 202210458409.2.

[0015] The beneficial effects of the present invention are:

[0016] (1) The biogenic amorphous calcium carbonate of the present invention is synthesized by induction of Bacillus licheniformis, and its adsorption capacity for organic dyes is significantly better than that of other common environmental microbial strains;

[0017] (2) The biogenic amorphous calcium carbonate of the present invention has excellent adsorption properties for organic dyes. Its maximum adsorption capacity for the organic dye CR can reach 454.55 mg / g, which is significantly higher than that of most commonly used adsorption materials.

[0018] (3) The biogenic amorphous calcium carbonate of the present invention has an adsorption efficiency of 100% for organic dyes, which is expected to achieve near-zero emissions of organic dyes and has good regeneration and recycling performance;

[0019] (4) The biogenic amorphous calcium carbonate of the present invention has a wide pH range of application and can maintain good organic dye adsorption properties in an environment with a pH greater than or equal to 6.0;

[0020] (5) The biogenic amorphous calcium carbonate of the present invention has an extremely fast adsorption rate for organic dyes, reaching adsorption equilibrium within 3 hours, and its adsorption kinetics conforms to the pseudo-second-order kinetic model;

[0021] (6) The adsorption process of the biogenic amorphous calcium carbonate of the present invention on organic dyes is an endothermic reaction process. The adsorption efficiency increases with increasing temperature, which can further improve its application effect in summer or in areas with mild climates (such as southern China).

[0022] (7) The preparation method of the biogenic amorphous calcium carbonate of the present invention is economical and environmentally friendly, simple and fast to operate, low in cost, and the obtained amorphous calcium carbonate has good stability and a porous surface, and is an organic-inorganic composite material; no toxic or harmful substances are added during the synthesis process, so the biogenic amorphous calcium carbonate product will not cause secondary pollution and has no potential risks to the environment, and has good application prospects for the repair of organic dyes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The structure and morphology characteristics of the biogenic amorphous calcium carbonate in Example 1 are shown; a is the XRD pattern, b is the TEM-SAED result, c is the FTIR spectrum, and d is the TG-DTG result;

[0024] Figure 2 Shown are scanning electron microscope images (a1, a2) of the biogenic amorphous calcium carbonate in Example 1; b, c are atomic force microscope observation results;

[0025] Figure 3 The figure shows the comparative results of the adsorption performance of CR by amorphous calcium carbonate prepared by different bacteria.

[0026] Figure 4 Shown are the effects of different adsorbent dosages (a), adsorption temperature (b), pH (c) and adsorption time (d) on the adsorption of biogenic amorphous calcium carbonate, as well as the pseudo-first-order (e) and pseudo-second-order (f) kinetic fitting results.

[0027] Figure 5 Shown are the results of the effects of different coexisting ions on the adsorption properties of biogenic amorphous calcium carbonate;

[0028] Figure 6 Shown are the results of the effects of different concentrations of humic acid on the adsorption properties of biogenic amorphous calcium carbonate;

[0029] Figure 7 The figures show the adsorption performance of biogenic amorphous calcium carbonate on different dyes, a is the removal efficiency of different dyes, and b is the color change of the dye waste liquid before and after treatment with biogenic amorphous calcium carbonate.

[0030] Figure 8 Shown are the results of the effects of different recycling times on the adsorption performance of biogenic amorphous calcium carbonate. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments and drawings to clearly and completely describe the concept, specific structure and technical effects of the present invention so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of this application can be combined with each other unless there is a conflict.

[0032] Example 1

[0033] A method for preparing biogenic amorphous calcium carbonate for dye wastewater treatment, which specifically comprises the following steps:

[0034] (1) Preparation of bacterial culture liquid: 1-2 rings of Bacillus licheniformis (CGMCC No. 24275) were inoculated into 200 mL of sterilized (115°C, 30 min) LB liquid medium [(tryptone 1% (m / V), yeast extract 0.5% (m / V), NaCl 1% (m / V), 6.5 ≤ pH ≤ 7.5)] and cultured in a shaker at 30°C and 180 rpm for about 10 h to prepare bacterial culture liquid [effective viable cell count was (2.92 ± 0.51) × 10 8 cfu / mL], Bacillus licheniformis LRL007 was a dominant strain isolated from the soil of a rare earth mineral storage yard in southern Jiangxi (24°59′N, 115°02′E);

[0035] (2) Expanded culture and induced synthesis of biogenic amorphous calcium carbonate: 300 mL of prepared LB liquid medium was added to a clean 500 mL conical flask. After sterilization at 115 °C for 30 min, 5 mL of bacterial culture liquid and 1.5 mL of CaCl2 (0.6 g) mother solution were inoculated. 32 replicates were set up and cultured at 30 °C and 180 rpm for 7 days to induce the formation of biogenic amorphous calcium carbonate.

[0036] (3) Collection of biogenic amorphous calcium carbonate: The fermentation broth was centrifuged at 4000 rpm for 25 min; the collected precipitate was dried in an oven at 65 °C for 3 days, then ground and passed through a 100-mesh sieve to obtain biogenic amorphous calcium carbonate.

[0037] The structure and morphology of the precipitate prepared above were analyzed using XRD (X-ray diffraction), EDS (X-ray energy dispersive spectrometry), FTIR (Fourier transform infrared spectroscopy), TG-DTG (thermogravimetric analysis), TEM-SAED (transmission electron microscopy-selected area electron diffraction) and SEM (scanning electron microscopy). The results are as follows. Figure 1 and Figure 2 As shown, combined with XRD and TEM-SAED ( Figure 1The results of a, b) show that the precipitate is mainly amorphous calcium carbonate. The mineral element composition of EDS analysis is mainly C 41.7%, O 29.6%, Ca 12.4% ( Figure 1 b); FTIR spectrum ( Figure 1 c) shows that there are a large number of organic functional groups (-OH, -CH3, -CH2, CO, CN, NH, etc.) on the surface of the mineral. It can be seen that these amorphous calcium carbonates are organic-inorganic complex structures, of which the organic matter content is 41.31% ( Figure 1 d). Scanning electron microscopy ( Figure 2 a1, Figure 2 The observation results of a2) show that the surface of the biogenic amorphous calcium carbonate is rough and porous. The AFM image (( Figure 2 b, c)) The results show that its roughness is as high as 0.59 nm; In summary, biogenic amorphous calcium carbonate is an organic-inorganic composite mineral material with a porous surface.

[0038] Example 2

[0039] Comparison of CR adsorption properties of amorphous calcium carbonate synthesized by different bacteria

[0040] In order to clarify the advantages of the strain (Bacillus licheniformis LRL007-strain D) used in the present invention compared to common bacteria in the environment, the present invention also investigated the adsorption and removal effect of amorphous calcium carbonate induced by other common environmental strains, strain A-Escherichia coli (CGMCC No. 1.12883), strain B-Bacillus subtilis (CGMCC No. 1.15792), strain C-Bacillus megaterium (CGMCC No. 1.7413), strain E-Bacillus amyloliquefaciens (CGMCC No. 1.857) and strain F-Bacillus cereus (CGMCC No. 7069) on CR, and the preparation method was the same as that in Example 1.

[0041] In this experiment, 0.05 g of biogenic amorphous calcium carbonate produced by different bacteria was weighed into a 50 mL centrifuge tube and 20 mL of an organic dye solution (CR: 1000 mg / L) was added. After thorough mixing, the mixture was placed in a shaker at 25°C and 100 rpm for adsorption for 24 hours. After adsorption, the supernatant of each group was collected by centrifugation and analyzed by UV-Vis spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to measure the CR concentration and calculate its adsorption amount Q e (mg / g) (Formula 1)

[0042] Adsorption capacity Q e (mg / g) = (Formula 1)

[0043] Where: C i is the initial organic dye concentration (mg / L), C e is the concentration of organic dye when adsorption reaches equilibrium (mg / L), W is the mass of the adsorbent (g), V is the volume of the concentrated organic dye solution in the adsorption system (L).

[0044] Figure 3 The results showed that compared with other strains, the strain D-Bacillus licheniformis (CGMCC No. 24275) selected in the present invention showed the largest adsorption capacity for CR, with obvious advantages. It can be seen that the amorphous calcium carbonate induced by it has better application prospects in the field of dye wastewater remediation.

[0045] Example 3

[0046] Effects of different adsorbent dosages on the adsorption properties of biogenic amorphous calcium carbonate

[0047] Different amounts (0.005-0.1 g) of the biogenic amorphous calcium carbonate obtained in Example 1 were weighed into a 50 mL centrifuge tube and 20 mL of an organic dye solution (CR: 500 mg / L) was added. After thorough mixing, the mixture was placed in a shaker at 25°C and 100 rpm for adsorption for 24 h. After adsorption, the supernatant of each group was collected by centrifugation and analyzed by UV-Vis spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to measure the CR concentration and calculate its adsorption amount Q e (mg / g) (Formula 1) and adsorption efficiency A e (%) (Formula 2). The results show that the adsorption efficiency increases with the increase in the amount of adsorbent. This may be due to the increase in the amount of adsorbent, which increases its specific surface area and provides more sites for CR adsorption. When 0.05 g / 20 mL (2.5 g / L) of biogenic amorphous calcium carbonate is added, the adsorption efficiency of CR is the highest ( Figure 4 a). After that, further addition had no significant effect on the adsorption efficiency, and the optimal dose was determined to be 2.5 g / L. Q e Continued decrease ( Figure 4a), which may be due to the increase in the number of adsorbable unsaturated sites. It may also be because the high concentration of adsorbent promotes the aggregation of adsorbent, thereby reducing the total surface area of ​​biogenic amorphous calcium carbonate and extending the diffusion path. Similar adsorption characteristics have also been found for other CR adsorbents.

[0048] Adsorption efficiency A e (%) = (Formula 2)

[0049] Where: C i is the initial organic dye concentration (mg / L), C e is the concentration of organic dye when adsorption reaches equilibrium (mg / L).

[0050] Example 4

[0051] Adsorption characteristics of organic dye Congo red (CR) on biogenic amorphous calcium carbonate and comparison with other materials

[0052] The biogenic amorphous calcium carbonate prepared in Example 1 was used for CR adsorption: according to the optimal adsorbent dosage of 2.5 g / L, the biogenic amorphous calcium carbonate prepared above was added to CR (composed of C 32 H 22 N6Na2O6S2) in simulated wastewater and adsorbed in a shaker at 25 ℃ and 100 rpm for 24 h. After adsorption, the mixture was centrifuged (9000 rpm, 10 min) and then analyzed by UV-Vis spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to calculate the amount of CR. The adsorption amount of organic dyes by biogenic amorphous calcium carbonate was calculated according to the expression Q e (mg / g) (Formula 1) and adsorption efficiency A e (%) (Formula 2). The adsorption data were further analyzed using the Langmuir (Formula 3) and Freundlich (Formula 4) isothermal adsorption models.

[0053] Langmuir: (Formula 3)

[0054] Freundlich: (Formula 4)

[0055] Where: C eis the concentration of organic dye when adsorption reaches equilibrium (mg / L), Q e is the adsorption amount of organic dye when adsorption reaches equilibrium (mg / g), Q max is the maximum adsorption capacity of the adsorbent for organic dyes (mg / g); K L is the adsorption coefficient of the Langmuir model (L / mg); K F and n are the parameters of the Freundlich model related to the adsorption amount and adsorption intensity, respectively.

[0056] By comparing R 2 The Langmuir isotherm adsorption model has a better fitting effect at different temperatures (Table 1), which can also be clearly seen in the figure ( Figure 4 b). It shows that the adsorption of the biogenic amorphous calcium carbonate prepared in Example 1 is mainly a monolayer adsorption type. The maximum adsorption amount of CR by the biogenic amorphous calcium carbonate prepared in Example 1 ( Q max ) is 454.55 mg / g, and its maximum adsorption capacity is significantly higher than that of other common mineral materials, modified materials and natural adsorption materials (the specific adsorption experimental process is the same as that of biogenic amorphous calcium carbonate) (Table 2). In addition, according to Table 1 and Figure 4 Results in Figure b also show that the maximum adsorption capacity of biogenic amorphous calcium carbonate increases with increasing temperature, indicating that the adsorption process is endothermic. The enhanced adsorption capacity of biogenic amorphous calcium carbonate with increasing temperature is likely due to the increased thermal motion of molecules, which increases the probability of collision between the adsorbent and dye molecules, thus facilitating the adsorbent's capture of organic dyes. This indicates that higher temperatures are more conducive to CR adsorption, suggesting that the present material has a greater advantage in applications involving organic dye wastewater in summer or in temperate southern regions of my country.

[0057] Table 1 Langmuir and Freundlich adsorption model parameters

[0058]

[0059] Table 2 Maximum adsorption capacity of CR by different adsorption materials ( Q max , mg / g)

[0060]

[0061] Example 5

[0062] Effects of different pH values ​​on the adsorption properties of biogenic amorphous calcium carbonate

[0063] 0.05 g of the biogenic amorphous calcium carbonate obtained in Example 1 was weighed into a 50 mL centrifuge tube, and 20 mL of organic dye solution (CR: 500 mg / L) with different pH values ​​(6-12) was added. After thorough mixing, the mixture was placed in a shaker at 25°C and 100 rpm for adsorption for 24 h. After adsorption, the supernatant of each group was collected by centrifugation and analyzed by UV-Vis spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to measure the concentration and calculate its adsorption efficiency A e (%) (Formula 2). The result is as follows Figure 4 c, the results show that when pH ≥ 6.0, biogenic amorphous calcium carbonate can still maintain a high adsorption capacity and is basically not affected by the increase in pH ( Figure 4 c), indicating that biogenic amorphous calcium carbonate has good pH adaptability. Zeta potential results ( Figure 4 c, inset) shows that the surface of biogenic amorphous calcium carbonate has a significant negative charge, indicating that electrostatic attraction is not the driving force for its adsorption.

[0064] Example 6

[0065] Effects of different time on the adsorption properties of biogenic amorphous calcium carbonate and its adsorption kinetics

[0066] 0.05 g of the biogenic amorphous calcium carbonate prepared in Example 1 was thoroughly mixed with an organic dye CR (500 mg / L) and a solution (20 mL, pH = 6.0). The mixture was then shaken at 100 r / min and 25 °C for different time periods t (1 to 1440 min), with three replicates per group. After adsorption, the supernatant was obtained by centrifugation (9000 r / min, 10 min) and analyzed by UV-Vis spectroscopy (UV-Vis, A max =498 nm, UV-2700i, Shimadzu) to determine the concentration of organic dye in the supernatant. The adsorption amount after different adsorption times t can be calculated using the formula ( Q t , mg / g) (Formula 1) and adsorption efficiency A t (Formula 2):

[0067] Adsorption kinetics can provide important information about the adsorption mechanism. Analyzing the kinetic adsorption data of the adsorbent using the pseudo-first-order (Equation 5) and pseudo-second-order (Equation 6) adsorption kinetic models can further understand its kinetic adsorption characteristics:

[0068] Ln ( Q e, exp –Q t ) = Ln ( Q e1, cal ) – K 1 t (Formula 5)

[0069] (Formula 6)

[0070] Where: K 1 represents the pseudo-first-order adsorption rate constant (min −1 ), Q e, exp Refers to the adsorption amount of organic dye when adsorption reaches equilibrium (mg / g); Q e1, cal It represents the adsorption amount of organic dye (mg / g) when the adsorption reaches equilibrium calculated by the pseudo-first-order adsorption kinetic equation. K 2 represents the pseudo-secondary adsorption rate constant (g / mg min), Q e2, cal It represents the adsorption amount of organic dye (mg / g) when the adsorption reaches equilibrium, calculated by the pseudo-second-order adsorption kinetic equation.

[0071] The results showed that the adsorption efficiency of biogenic amorphous calcium carbonate for CR increased rapidly in the first 3 h ( Figure 4 d); thereafter, the adsorption efficiency did not change significantly with the extension of time, and the adsorption efficiency of biogenic amorphous calcium carbonate for CR finally stabilized at about 92%. The pseudo-first-order and pseudo-second-order adsorption kinetic models were used to analyze the kinetic data, and the corresponding kinetic parameters were calculated ( Figure 4 e and 4f). The results show that the pseudo-second-order adsorption kinetic model has a higher correlation coefficient (R 2 = 0.9999), and the adsorption amount calculated by the pseudo-second-order adsorption kinetic model ( Q e2,cal ) is closer to the adsorption amount obtained in the experiment ( Q e ); It can be seen that the adsorption kinetics between biogenic amorphous calcium carbonate and organic dyes is more consistent with the pseudo-second-order adsorption kinetics model, indicating that the adsorption rate depends on the number of unoccupied adsorption sites on the adsorbent surface, and the adsorption process is mainly chemical adsorption.

[0072] Example 7

[0073] Adsorption anti-interference ability and resistance to the influence of humic acid

[0074] The different ions (K + , Na + , NH4 +, Ca 2+ , Mg 2+ , Al 3+ , NO3 - , NO2 - , SO4 2- , CO3 2- ,HPO4 2- ) and the influence of humic acid on the adsorption process. Weigh 0.05 g of the biogenic amorphous calcium carbonate obtained in Example 1 into a 50 mL centrifuge tube, add 20 mL of organic dye solution (CR: 10 mg / L, refer to the actual concentration of dye wastewater), set different concentrations of ion concentration (0-2%) and humic acid (0-100 mg / L) interference groups, mix thoroughly and place in a shaker at 25 ° C and 100 rpm for adsorption for 24 h, and do 3 replicates for each group. After the adsorption is completed, the supernatant of each group is collected by centrifugation and analyzed by ultraviolet-visible spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to measure the CR concentration in the supernatant and calculate its adsorption efficiency A e (%) (Formula 2). The results show that the adsorption of organic dye CR by biogenic amorphous calcium carbonate is basically not affected by coexisting ions and humic acid in water ( Figure 5 , Figure 6 ), has good adsorption and anti-interference properties, and has excellent application potential in complex dye wastewater.

[0075] Example 7

[0076] Selective adsorption experiments

[0077] In order to explore the applicability of the obtained biogenic amorphous calcium carbonate, the adsorption and removal results of different dyes, including methylene blue (MB), rhodamine B (RB), acid orange (AO), and methyl orange (MO), were also investigated. 0.05 g of the biogenic amorphous calcium carbonate obtained in Example 1 was weighed into a 50 mL centrifuge tube, and 20 mL of different organic dye solutions (100 mg / L) were added respectively. After thorough mixing, the mixture was placed in a shaker at 25°C and 100 rpm for adsorption for 24 h. After the adsorption was completed, the supernatant of each group was collected by centrifugation, and the concentration was determined by ultraviolet-visible spectroscopy (UV-Vis, UV-2700i, Shimadzu), and the adsorption efficiency was calculated respectively. A e (%) (Formula 2). The results are as follows Figure 7As shown in the figure, the adsorption efficiency of biogenic amorphous calcium carbonate for CR is 100%, which is significantly higher than that of the other four organic dyes. It can be seen that biogenic amorphous calcium carbonate shows a high selectivity for CR and can specifically and efficiently remove CR from water.

[0078] Example 8

[0079] Recycling experiment

[0080] The regeneration and recycling performance of adsorbents are important indicators for evaluating their industrial application capabilities. In adsorption experiments, regeneration and recycling is the cyclic process in which the adsorbent material adsorbs and desorbs pollutants and then reuses them. Bio-sourced amorphous calcium carbonate (0.05 g) was added to tap water (20 mL) containing 10 mg / L (the actual concentration of dye wastewater) CR and shaken for 24 hours. After the adsorption was completed, the supernatant of each group was collected by centrifugation and analyzed by ultraviolet-visible spectroscopy (UV-Vis, A max = 498 nm, UV-2700i, Shimadzu) to measure the CR concentration in the supernatant and calculate its adsorption efficiency A e (%) (Formula 2). The precipitate was then immersed in 50% ethanol (20 mL) and desorbed on a shaker for 24 hours in preparation for subsequent re-adsorption experiments. This adsorption / desorption experiment was performed eight times to evaluate its sustainable application potential and stability. The results showed that after eight cycles, ACC still maintained a nearly 100% adsorption efficiency for CR ( Figure 8 ), this excellent renewable recycling ability and adsorption stability indicate that the prepared biogenic amorphous calcium carbonate is a very excellent and economically efficient adsorption material.

[0081] Although the description of the present invention has been exhaustive and particularly describes several embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but rather should be considered to provide a broad possible interpretation of these claims in view of the prior art by reference to the appended claims, thereby effectively covering the intended scope of the invention. In addition, the above description of the invention is based on the embodiments foreseen by the inventors, which is intended to provide a useful description, and those non-substantial changes to the invention that have not yet been foreseen may still represent equivalent changes to the invention.

Claims

1. A use of biogenic amorphous calcium carbonate in removing organic dyes from wastewater or preparing an organic dye adsorbent, characterized in that: The organic dye is the typical anionic dye Congo red; The preparation method of the biogenic amorphous calcium carbonate comprises the following steps: inoculating Bacillus licheniformis LRL007 into a liquid culture medium containing a soluble inorganic calcium salt for culturing to obtain the biogenic amorphous calcium carbonate; the Bacillus licheniformis LRL007 has been deposited in the General Microbiology Center of the China National Center for Microbiological Culture Collection on January 10, 2022, with a deposit number of CGMCC No. 24275; The mineral elements in the biogenic amorphous calcium carbonate are C: 41.7%, O: 29.6%, and Ca: 12.4%. The added amount of the soluble inorganic calcium salt is 1 g / L to 2 g / L.

2. The use according to claim 1, characterized in that The liquid culture medium is LB culture medium or beef extract peptone culture medium.

3. The use according to claim 1, characterized in that The soluble inorganic calcium salt is calcium chloride.

4. The use according to claim 1, characterized in that The inoculation process of the Bacillus licheniformis LRL007 is as follows: 2 mL to 5 mL of seed solution is added to every 100 mL to 300 mL of culture medium, and the concentration of Bacillus licheniformis LRL007 in the seed solution is (2.92 ± 0.51) × 10 8 cfu / mL.

5. The use according to claim 1, characterized in that The temperature of the culture process is 25°C to 35°C, and the time is 3 to 7 days. After the culture is completed, the precipitate is centrifuged, dried, ground and sieved to obtain the biogenic amorphous calcium carbonate.

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