Biological source amorphous calcium carbonate for dye wastewater treatment as well as preparation method and application of biological source amorphous calcium carbonate

Abstract

The invention belongs to the technical field of environmental treatment, and particularly relates to biological source amorphous calcium carbonate for dye wastewater treatment as well as a preparation method and application of the biological source amorphous calcium carbonate. The method comprises the following steps: inoculating bacillus licheniformis LRL007 into a liquid culture medium containing soluble inorganic calcium salt, and culturing to obtain the biological source amorphous calcium carbonate, the bacillus licheniformis LRL007 is preserved in the China General Microbiological Culture Collection Center on January 10, 2022, and the preservation number is CGMCC (China General Microbiological Culture Collection Center) No. 24275. The preparation method is economical, environmentally friendly and easy to operate, no toxic or harmful substance is added in the synthesis process, and no secondary pollution is caused; the obtained amorphous calcium carbonate is good in stability, has a well-developed porous structure and relatively good organic dye adsorption anti-interference capability, is wide in pH application range, can be recycled for at least 8 times or more, and has a very good application prospect in treatment of organic dye wastewater.

Description

Technical Field

[0001] The 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. Background Art

[0002] A large amount of dye wastewater is generated in the production and use of various dyes such as disperse dyes, acid dyes, anionic dyes and sulfur dyes. The printing and dyeing industry is a major discharger of industrial wastewater. These dye wastewaters have complex components and are very stable. They have dark colors visible to the naked eye, strong acidity and alkalinity, and have "three-cause" effects. Congo Red (CR, C 32 H 22 N6Na2O6S2) is a typical anionic diazo dye, mainly used in plastics, paper, textiles, printing and dyeing industries. CR is a water-soluble benzidine-based azo dye with a complex structure. It is not only carcinogenic and mutagenic to organisms, but also extremely harmful to the natural environment. Direct discharge into the ecosystem will cause serious environmental problems and health risks. Moreover, due to the high biodegradation resistance of CR compounds, it is difficult to effectively remove them through the self-purification of water bodies, and it is difficult to effectively degrade them 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., and the adsorption process is simple and easy to operate, with good practicality, so 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 so far, such as polymers, zeolites, clays, carbon nanotubes and activated carbon, the choice is still very limited. At the same time, there are also common problems such as low adsorption capacity, high cost, difficulty in reuse, and being greatly affected by 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 and difficult to promote and apply 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, there are few reports on the adsorption performance of biogenic amorphous calcium carbonate, which seriously restricts the theoretical research and potential applications of biogenic amorphous calcium carbonate.

[0004] Compared with calcium carbonate such as stalactites and limestones in nature and chemically synthesized calcium carbonate, amorphous calcium carbonate prepared by microbial induced mineralization has unique advantages. Its surface is porous and contains a large number of active groups, making it suitable for adsorption materials. While microorganisms use their own synthesized amorphous calcium carbonate to adsorb and remove organic dyes in sewage, they can also promote the metabolism of polluting organic matter in sewage, increase the pH of the mineralization system, and promote the smooth progress of mineralization reactions. At present, the preparation method of amorphous calcium carbonate synthesized by chemical methods is extremely complicated, with poor stability and high cost. This is because amorphous calcium carbonate is the most unstable state among calcium carbonate mineral types. Therefore, a large amount of stabilizers such as polyvinyl pyrrolidone, polyacrylic acid, and highly carboxylated substances are often required in its chemical synthesis process. These stabilizers will bring environmental safety risks; and the microbial induced mineralization method of amorphous calcium carbonate has a simple operation process, low cost, and environmental friendliness, which has obvious advantages. Therefore, exploring the biosynthesis method of amorphous calcium carbonate and its adsorption characteristics for organic dyes will help promote the development and application of biogenic amorphous calcium carbonate in the field of organic dye treatment. Microorganisms are ubiquitous in the environment, and many of them can induce the formation of amorphous calcium carbonate. Based on this, we 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 scheme: 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 in a liquid culture medium containing soluble inorganic calcium salts for culturing to obtain biogenic amorphous calcium carbonate; the Bacillus licheniformis LRL007 has been deposited in the General Microbiology Center of the China National Microbiological Culture Collection Administration on January 10, 2022, with a deposit number of CGMCC No. 24275.

[0006] The Bacillus licheniformis LRL007 used in the present invention is highly adaptable, environmentally friendly, widely distributed in water bodies or soil, and 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 the cultivation process, so that the pH in the solution can be significantly improved, thereby promoting the synthesis of amorphous calcium carbonate. This method does not require the additional addition of alkali sources and other stabilizers required in traditional methods, effectively reduces the cost of preparation, and is environmentally friendly.

[0007] Preferably, the liquid culture medium is LB culture medium or beef extract peptone culture 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. The present invention avoids the need to add additional alkali sources and other stabilizers in the traditional preparation method. In addition, the soluble inorganic calcium salt uses industrial-grade calcium chloride, which is cheap and only needs to be added in an amount of 1 g / L to 2 g / L, which greatly reduces the cost.

[0008] 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.

[0009] 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.

[0010] The second aspect of the present invention also provides a biogenic amorphous calcium carbonate prepared by the above-mentioned preparation method for dye wastewater treatment, wherein the mineral elements in the biogenic amorphous calcium carbonate are C: 41.7%, O: 29.6%, and Ca: 12.4%. The biogenic amorphous calcium carbonate prepared by the present invention has a rough and porous surface, good dispersibility, and well-developed pores, and can remove organic dyes through pore wrapping. In addition, the material is also an organic-inorganic composite material, and there are a variety of functional groups on the surface, which can enhance the adsorption effect by forming hydrogen bonds or chemical bonds with the dye.

[0011] The third aspect of the present invention also provides the use of the above-mentioned biogenic amorphous calcium carbonate in the removal of organic dyes from wastewater or in the preparation of organic dye adsorbents. The organic dye is Congo red. The biogenic amorphous calcium carbonate is used in the treatment of wastewater contaminated with organic dyes; its maximum adsorption capacity for CR (Congo red) can reach 454.55 mg / g, which is significantly higher than other common adsorption materials. In addition, the above-mentioned biogenic amorphous calcium carbonate exhibits a wide range of pH applicability, and can maintain good stability and adsorption characteristics in an environment with a pH value greater than or equal to 6.0 (CR will change color due to protonation when the pH is lower than 6). The optimal adsorbent dose is 2.5 g / L, and equilibrium can be reached after about 3 hours of adsorption. Moreover, after being recycled 8 times, it still has stable and efficient adsorption performance, and is almost unaffected by the influence of different coexisting ions and humic acid, and has great application potential.

[0012] The fourth aspect of the present invention further provides an organic dye adsorbent, which comprises the above-mentioned biogenic amorphous calcium carbonate.

[0013] 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.

[0014] The beneficial effects of the present invention are: (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; (2) The biogenic amorphous calcium carbonate of the present invention has excellent adsorption performance for organic dyes, and its maximum adsorption capacity for organic dye CR can reach 454.55 mg / g, which is significantly higher than most commonly used adsorption materials; (3) The adsorption efficiency of the biogenic amorphous calcium carbonate of the present invention on organic dyes can reach 100%, which is expected to achieve near-zero emission of organic dyes and has good regeneration and recycling performance; (4) The biogenic amorphous calcium carbonate of the present invention has a wide pH application range and can maintain good organic dye adsorption properties in an environment with a pH greater than or equal to 6.0; (5) The biogenic amorphous calcium carbonate of the present invention has an extremely fast adsorption rate for organic dyes, and can reach adsorption equilibrium within 3 hours. Its adsorption kinetics process conforms to the pseudo-second-order kinetic model; (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 the increase of temperature. The application effect can be further improved in summer or in areas with mild climate (such as southern China).

[0015] (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

[0016] Figure 1 The structure and morphology characteristics of the biogenic amorphous calcium carbonate in Example 1 are shown; a is an XRD spectrum, b is a TEM-SAED result diagram, c is a FTIR spectrum, and d is a TG-DTG result diagram; 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; Figure 3 The figure shows the comparative results of the CR adsorption performance of amorphous calcium carbonate prepared by different bacteria.

[0017] Figure 4 The results of the effects of different adsorbent dosages (a), adsorption temperature (b), pH (c) and adsorption time (d) on the adsorption of biogenic amorphous calcium carbonate and the pseudo-first-order (e) and pseudo-second-order (f) kinetic fitting results are shown; Figure 5 The results show the effect of different coexisting ions on the adsorption performance of biogenic amorphous calcium carbonate; Figure 6 The results show the effect of different concentrations of humic acid on the adsorption performance of biogenic amorphous calcium carbonate; Figure 7 The figures show the adsorption performance of biogenic amorphous calcium carbonate for different dyes, a is the removal efficiency of different dyes, and b is the color change of the dye waste liquid before and after being treated with biogenic amorphous calcium carbonate.

[0018] Figure 8 Shown are the results of the effects of different recycling times on the adsorption performance of biogenic amorphous calcium carbonate. DETAILED DESCRIPTION

[0019] 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 without conflict.

[0020] Example 1 A method for preparing biogenic amorphous calcium carbonate for dye wastewater treatment, which specifically comprises the following steps: (1) Preparation of bacterial culture medium: 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 medium [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 dump in southern Jiangxi (24°59′N, 115°02′E); (2) Expanded culture and induced synthesis of biogenic amorphous calcium carbonate: Add 300 mL of prepared LB liquid medium to a clean 500 mL conical flask, sterilize at 115 °C for 30 min, inoculate 5 mL of bacterial culture liquid and 1.5 mL of CaCl2 (0.6 g) mother solution, set up 32 parallels, and culture at 30 °C and 180 rpm for 7 days to induce the formation of biogenic amorphous calcium carbonate; (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.

[0021] The structure and morphology of the precipitate prepared above were analyzed using XRD (X-ray diffraction), EDS (X-ray energy spectrum analysis), 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 1 The results of a, b) show that the precipitate is mainly amorphous calcium carbonate. EDS analysis shows that its mineral element composition 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, with an organic matter content of 41.31% ( Figure 1 d). Scanning electron microscopy ( Figure 2 a1, Figure 2 The observation results of a2 show that the surface of biogenic amorphous calcium carbonate is rough and porous. Figure 2 b, c)) The results show that its roughness is as high as 0.59nm; In summary, biogenic amorphous calcium carbonate is an organic-inorganic composite mineral material with a porous surface.

[0022] Example 2 Comparison of CR adsorption performance of amorphous calcium carbonate synthesized by different bacteria In order to clarify the advantages of the strain (Bacillus licheniformis LRL007-strain D) used in the present invention compared with 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.

[0023] In the 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 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 h. After the adsorption was completed, 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) Adsorption Q e (mg / g) = (Formula 1) 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).

[0024] Figure 3The results showed that compared with other strains, the strain D-Bacillus licheniformis (CGMCC No. 24275) selected in the present invention showed the largest adsorption amount 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.

[0025] Example 3 Effects of different adsorbent dosages on the adsorption properties of biogenic amorphous calcium carbonate Weigh different amounts (0.005-0.1 g) of the biogenic amorphous calcium carbonate obtained in Example 1 into a 50 mL centrifuge tube and add 20 mL of an organic dye solution (CR: 500 mg / L). After thorough mixing, place the mixture in a shaker at 25 °C and 100 rpm for adsorption for 24 h. After adsorption, collect the supernatant of each group by centrifugation and analyze the supernatant using 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 leads to an increase in its specific surface area, providing more sites for CR adsorption. When 0.05 g / 20 mL (2.5 g / L) of biogenic amorphous calcium carbonate is added, its adsorption efficiency for 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 4 a), 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 prolonging the diffusion path. Similar adsorption characteristics have also been found for other CR adsorbents.

[0026] Adsorption efficiency A e (%) = (Formula 2) 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).

[0027] Example 4 Adsorption characteristics of organic dye Congo red (CR) by biogenic amorphous calcium carbonate and comparison with other materials 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 °C and 100 rpm for 24 h. After adsorption, the samples were 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.

[0028] Langmuir: (Formula 3) Freundlich: (Formula 4) Where: C e is 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.

[0029] By comparing R 2 It can be seen from the values ​​that the Langmuir isotherm adsorption model has a better fitting effect at different temperatures (Table 1), which can also be clearly seen from the figure ( Figure 4b). 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, from Table 1 and Figure 4 The results of b also show that the maximum adsorption amount of biogenic amorphous calcium carbonate increases with the increase of temperature, indicating that the adsorption process is an endothermic reaction. The increase in temperature leads to an increase in the adsorption capacity of biogenic amorphous calcium carbonate, which may be due to the increase in temperature expanding the thermal motion of molecules, increasing the probability of collision between the adsorbent and the dye molecules, and facilitating the adsorbent to capture organic dyes. It can be seen that the higher the temperature, the more conducive it is to the adsorption of CR. The material of the present invention has greater advantages in the application of organic dye wastewater in summer or in mild areas in the south of my country.

[0030] Table 1 Langmuir and Freundlich adsorption model parameters Table 2 Maximum adsorption capacity of CR by different adsorbent materials ( Q max , mg / g) Example 5 Effect of different pH values ​​on the adsorption properties of biogenic amorphous calcium carbonate Weigh 0.05 g of the biogenic amorphous calcium carbonate obtained in Example 1 into a 50 mL centrifuge tube, and add 20 mL of organic dye solution (CR: 500 mg / L) with different pH values ​​(6-12) respectively. After thorough mixing, place in a shaker at 25 °C and 100 rpm for adsorption for 24 h. After the adsorption is completed, collect the supernatant of each group by centrifugation, and use 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 applicability. 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.

[0031] Example 6 Effects of different time on the adsorption performance of biogenic amorphous calcium carbonate and its adsorption kinetics 0.05 g of the biogenic amorphous calcium carbonate prepared in Example 1 was thoroughly mixed with the organic dye CR (500 mg / L) and solution (20 mL, pH = 6.0), and then placed in a shaker at 100 r / min and 25 °C for different time periods t (1 to 1440 min), with 3 parallels in each group. After the adsorption was completed, the supernatant was obtained by centrifugation (9000 r / min, 10 min), and UV-Vis, A max =498 nm, UV-2700i, Shimadzu) to determine the concentration of organic dyes 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): Adsorption kinetics can provide important information about the adsorption mechanism. By analyzing the kinetic adsorption data of the adsorbent using the pseudo-first-order (Formula 5) and pseudo-second-order (Formula 6) adsorption kinetic models, we can further understand its kinetic adsorption characteristics: Ln( Q e, exp – Q t ) = Ln ( Q e1, cal ) – K 1 t (Formula 5) (Formula 6) Where: K 1 represents the pseudo-first-order adsorption rate constant (min −1 ), Q e, exp Refers to the amount of organic dye adsorbed 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.

[0032] The results showed that the adsorption efficiency of biogenic amorphous calcium carbonate on 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 finally the adsorption efficiency of biogenic amorphous calcium carbonate for CR 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-secondary 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.

[0033] Example 7 Adsorption anti-interference ability, resistance to the influence of humic acid 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 repeat 3 times 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.

[0034] Example 7 Selective adsorption experiments In order to explore the applicability of the obtained biogenic amorphous calcium carbonate, the adsorption and removal results of different dyes such as methylene blue (MB), rhodamine B (RB), acid orange (AO), and methyl orange (MO) were also investigated. Weigh 0.05 g of the biogenic amorphous calcium carbonate obtained in Example 1 in a 50 mL centrifuge tube, and add 20 mL of different organic dye solutions (100 mg / L) respectively. After fully mixing, place it in a shaker at 25°C and 100 rpm for adsorption for 24 h. After the adsorption, 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 7 As shown, 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.

[0035] Example 8 Recycling experiment The regeneration and recycling performance of the adsorbent is an important indicator for evaluating its industrial application ability. In the adsorption experiment, regeneration and recycling is a cyclic process in which the adsorbent material adsorbs and desorbs pollutants and then reuses them. Biogenic amorphous calcium carbonate (0.05 g) was added to tap water (20 mL) containing 10 mg / L (i.e., the actual dye wastewater concentration) CR and shaken on a shaker 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 h in preparation for the subsequent re-adsorption experiment. The adsorption / desorption experiment was performed 8 times in total to evaluate its sustainable application potential and stability. The results showed that after 8 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.

[0036] Although the description of the present invention has been described as detailed as possible and specifically describes several described embodiments, it is not intended to be limited to any of these details or embodiments or any particular embodiment, but should be regarded as providing a broad possible interpretation of these claims by reference to the attached claims in view of the prior art, thereby effectively covering the intended scope of the present invention. In addition, the above description of the present invention is based on the embodiments foreseeable by the inventor, and its purpose is to provide a useful description, and those non-substantial changes to the present invention that have not yet been foreseen may still represent equivalent changes to the present invention.

Claims

1. A method for preparing biogenic amorphous calcium carbonate for dye wastewater treatment, characterized in that: The following steps are involved: Bacillus licheniformis LRL007 is inoculated into a liquid culture medium containing soluble inorganic calcium salts for cultivation to obtain the biogenic amorphous calcium carbonate; the Bacillus licheniformis LRL007 has been deposited in the General Microbiology Center of the China Microbiological Culture Collection Administration on January 10, 2022, with a deposit number of CGMCC No.24275.

2. The preparation method according to claim 1, characterized in that: The liquid culture medium is LB culture medium or beef extract peptone culture medium; the added amount of the soluble inorganic calcium salt is 1 g / L to 2 g / L.

3. The preparation method according to claim 2, characterized in that: The soluble inorganic calcium salt is calcium chloride.

4. The preparation method 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 preparation method 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.

6. A biogenic amorphous calcium carbonate for dye wastewater treatment, characterized in that: The invention is prepared by the preparation method according to any one of claims 1 to 5.

7. The biogenic amorphous calcium carbonate for dye wastewater treatment according to claim 6, characterized in that: The mineral element composition is C: 41.7%, O: 29.6%, Ca: 12.4%.

8. Use of the biogenic amorphous calcium carbonate according to any one of claims 6 to 7 in removing organic dyes from wastewater or preparing an organic dye adsorbent.

9. The use according to claim 8, characterized in that: The organic dye is the typical anionic dye Congo red.

10. An organic dye adsorbent, characterized in that: Including the biogenic amorphous calcium carbonate described in claim 6.

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