Method for removing fluorine in water through microorganism induced mineralization

Abstract

The invention discloses a method for removing fluorine in water through microorganism induced mineralization, and relates to the technical field of environmental science and biologication.The method is technically characterized in that achromobacter xylosoxidans serves as a microorganism source, calcium chloride is added into a urea culture solution of the achromobacter xylosoxidans, and a microorganism mineralization system is formed; and carrying out microbial mineralization defluorination under the conditions of different calcium ion concentrations, pH values, urea concentrations and culture time. According to the invention, when the addition amount of calcium chloride is 500mg / L to 1.5 g / L, the fluorine ion removal rate is increased along with the increase of the addition amount of calcium chloride; when the pH value is between 6 and 8, the removal rate can be maintained at 90%; when the concentration of urea is 20-30 g / L, the removal rate is reduced along with the increase of the concentration of urea, and according to the technical scheme, the fluorine removal efficiency is improved, the cost is reduced, the risk of secondary pollution is reduced, and excellent environmental friendliness and economical efficiency are shown.

Description

Technical Field

[0001] The invention relates to the fields of environmental science and biotechnology, and in particular to a method for removing fluorine from water by microbial induced mineralization. Background Art

[0002] In recent years, microbial induced mineralization (MICP) technology has attracted attention due to its environmental friendliness and cost-effectiveness. This technology uses microbial activity to promote the precipitation of minerals, thereby fixing or removing fluoride ions in water.

[0003] At present, fluoride removal technologies include physical, chemical and biological methods. Physical methods include adsorption and filtration, chemical methods include chemical precipitation and ion exchange, while biological methods involve the action of microorganisms. Among these methods, microbial induced mineralization technology stands out due to its unique advantages. This technology produces inorganic minerals through microbial metabolic activities, which are able to adsorb or co-precipitate fluoride ions, thereby reducing the fluoride content in water. For example, certain bacteria can produce minerals such as calcium carbonate during metabolism, which can effectively fix fluoride ions. In addition, modified phosphogypsum as a material is also used for fluoride removal, and its impurities are reduced through high-temperature treatment to make modified phosphogypsum to improve its adsorption performance.

[0004] Although microbial induced mineralization technology has shown good potential for fluoride removal, there are still some challenges and limitations. First, the treatment efficiency of MICP technology is affected by environmental conditions such as pH, temperature and nutrient supply, which need to be precisely controlled to optimize the fluoride removal effect. Second, the growth and metabolic activities of microorganisms may be interfered by other ions in the water, such as calcium ion concentration, urea concentration, etc. These coexisting ions may affect the removal efficiency of fluoride ions. Summary of the invention

[0005] The purpose of the present invention is to solve the above problems and provide a method for removing fluoride from water by microbial induced mineralization, so as to solve the problems of the prior art in terms of fluoride removal efficiency, environmental adaptability, ion interference, cost and environmental impact, and provide a new and effective solution for the removal of fluoride ions in water.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: a method for removing fluorine from water by microbial induced mineralization, the method comprising the following steps:

[0007] a. Using Achromobacter xylosoxidans as a microbial source;

[0008] b. adding calcium chloride to the urea culture solution of Achromobacter xylose oxidans to form a microbial mineralization system;

[0009] c. Use the above-mentioned microbial mineralization system to carry out microbial mineralization and fluoride removal.

[0010] Furthermore, in the method, the amount of calcium chloride added is 500 mg / L to 1.5 g / L, and under this condition, the removal rate of F- increases with the increase in the amount of calcium chloride added.

[0011] Furthermore, in the method, when the pH condition is between 6 and 8, the removal rate of F- in the solution is maintained at 90%.

[0012] Furthermore, in the method, the urea concentration is 20 g / L to 30 g / L, under which condition the removal rate of F- decreases with the increase of urea concentration.

[0013] Furthermore, the adsorption of F- by microbial mineralization in the method is mainly concentrated within the first 3 days and tends to be stable after the 3rd day.

[0014] Another object of the present invention is to provide a method for fixing and removing fluorine from water by combining modified phosphogypsum with Achromobacter xylosoxidans, the method comprising the following steps:

[0015] a. The obtained phosphogypsum sample was passed through a 200-mesh standard sieve and dried in an oven at 45°C to constant weight;

[0016] b. Place the dried sample into a muffle furnace, set the temperature to 800°C and last for 15 minutes to prepare modified phosphogypsum;

[0017] c. The above modified phosphogypsum combined with Achromobacter xylose oxidizing to fix and remove F - .

[0018] Furthermore, the optimal dosage of the modified phosphogypsum is 4 g / L.

[0019] Furthermore, the modified phosphogypsum is combined with Achromobacter xylosoxidans to fix and remove F - The optimal pH is 7.

[0020] Compared with the prior art, the beneficial effects of this scheme are as follows: By using a combination of Achromobacter xylosoxidans and calcium chloride, the present method can effectively remove fluoride ions within a wider range of calcium ion concentrations, especially when the amount of calcium chloride added is increased from 500 mg / L to 1.5 g / L, the removal rate of fluoride ions is significantly improved, which shows the adaptability and high efficiency of this method in treating fluoride-containing water bodies with different concentrations. In addition, the present method can stably maintain a fluoride ion removal rate of 90% under the condition of pH 6 to 8, which enables the technology to maintain a high fluoride removal efficiency under different environmental conditions. At the same time, the adjustment of urea concentration provides additional control parameters for optimizing the defluorination process, and the adsorption of fluoride ions by microbial mineralization is mainly concentrated in the first 3 days, and then tends to be stable.

[0021] The method for fixing and removing fluoride from water by combining modified phosphogypsum with Achromobacter xylosoxidans provided by the present invention is to prepare modified phosphogypsum by high-temperature treatment of phosphogypsum, which not only improves the adsorption performance of the material, but also reduces its impurity content, making the modified phosphogypsum more effective in the defluorination process. The optimal dosage is 4g / L and the optimal pH value is 7, which makes the method highly practical and operable. Compared with the prior art, the present method not only improves the defluorination efficiency, but also reduces the cost, while reducing the risk of secondary pollution, showing better environmental friendliness and economy. The implementation of these technical solutions provides a new solution for the removal of fluoride ions in water, helps to improve water quality, protect human health, and is of great significance for environmental protection and sustainable utilization of resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a flow chart of a method for removing fluoride from water by microbial induced mineralization according to an embodiment of the present invention;

[0023] Figure 2 This is a flow chart of a method for fixing and removing fluoride from water by using modified phosphogypsum in combination with Achromobacter xylosoxidans in an embodiment of the present invention;

[0024] Figure 3 This is an appearance diagram of phosphogypsum in an embodiment of the present invention;

[0025] Figure 4 Schematic diagram of fluoride removal by using modified phosphogypsum in different dosages in combination with Achromobacter xylosoxidans in an embodiment of the present invention;

[0026] Figure 5 Schematic diagram of fluoride removal by modified phosphogypsum combined with Achromobacter xylosoxidans under different pH conditions in an embodiment of the present invention;

[0027] Figure 6 The modified phosphogypsum and the combined system fixed F in the embodiment of the present invention - SEM;

[0028] Among them, Figure A and Figure B are modified phosphogypsum; Figure C and Figure D are combined systems;

[0029] Figure 7 It is the XRD diagram of modified phosphogypsum and combined system in the embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0032] The reagents and drugs used in the present invention are shown in Table 1 below:

[0033] Table 1 Experimental reagents

[0034]

[0035] The instruments used in the present invention are shown in Table 2 below:

[0036] Table 2 Experimental instruments

[0037]

[0038] Example 1: Figure 1 As shown, a method for removing fluoride from water by microbial induced mineralization comprises the following steps:

[0039] a. Using Achromobacter xylosoxidans as a microbial source;

[0040] Preparation of strains: The freeze-dried strains of Pseudomonas putida were obtained from the laboratory strain collection center. The strains were revived in a medium containing nutrient broth and cultured in a 37°C constant temperature incubator for 24 hours until the bacterial solution became turbid, indicating that the strains were successfully activated.

[0041] Bacterial liquid expansion culture: transfer the activated bacterial liquid to a larger culture medium for expansion culture to obtain sufficient microbial mass for subsequent experiments. Continue to culture in a 37°C constant temperature incubator until the OD of the bacterial liquid reaches 600 (optical density) reached 0.8-1.0, indicating that the bacteria had grown to the logarithmic phase.

[0042] b. adding calcium chloride to the urea culture solution of Achromobacter xylose oxidans to form a microbial mineralization system;

[0043] Preparation of culture medium: According to the experimental design, urea culture medium of different concentrations was prepared as the growth medium of Achromobacter xylosoxidans. Analytical pure calcium chloride was added to the urea culture medium to prepare culture medium with different calcium ion concentrations ranging from 500 mg / L to 1.5 g / L.

[0044] Construction of microbial mineralization system: Inoculate the bacterial solution of Achromobacter xylosoxidans in the logarithmic growth phase into the urea culture solution containing calcium chloride at an inoculation amount of 2% (v / v). Gently shake the culture solution to ensure that the bacterial solution and the culture solution are fully mixed to form a uniform microbial mineralization system.

[0045] c. Use the above-mentioned microbial mineralization system to carry out microbial mineralization and fluoride removal.

[0046] Experimental condition setting: Calcium ion concentration: three treatment groups were set up, and 500 mg / L, 1 g / L and 1.5 g / L of calcium chloride were added respectively. pH condition: pH value of culture medium was adjusted to 6, 7 and 8 using pH meter to evaluate the fluoride removal effect under different pH conditions. Urea concentration: two treatment groups were set up, and urea concentration was 20 g / L and 30 g / L respectively. Culture time: different culture time points were set, including 1 day, 2 days, 3 days and 4 days, to observe the dynamic changes of fluoride ion removal.

[0047] Preparation of fluoride-containing water samples: Dissolve sodium fluoride in deionized water to prepare a 5 mg / L simulated fluoride-containing water sample to simulate the high-fluoride water environment in nature.

[0048] Microbial mineralization and fluoride removal experiment: The simulated fluoride-containing water sample was mixed with the microbial mineralization system, and each treatment group was repeated three times to ensure the accuracy and repeatability of the experimental results. The mixed system was placed in a constant temperature shaking incubator, the temperature was controlled at 37°C, and the shaking speed was 120 times / minute for cultivation.

[0049] Sample collection and analysis: Culture samples were collected at set time points, and the supernatant and precipitate were separated by centrifugation. The fluoride ion concentration in the supernatant was determined using the fluoride ion selective electrode method to evaluate the defluoridation effect. The precipitate was analyzed by XRD and SEM to determine the composition and morphology of the mineralized product.

[0050] Example 2: A method for removing fluoride from water by using modified phosphogypsum in combination with Achromobacter xylosoxidans, comprising the following steps:

[0051] a. The obtained phosphogypsum sample was passed through a 200-mesh standard sieve and dried in an oven at 45°C to constant weight;

[0052] Preparation of phosphogypsum samples: The phosphogypsum samples were obtained from Yuanheng Water Purification Material Factory, Gongyi City, Zhengzhou City, Henan Province. Figure 3The phosphogypsum sample was sieved using a 200-mesh standard sieve to ensure that the particle size of the sample was uniform.

[0053] Sample drying: Spread the sieved phosphogypsum sample evenly on a tray and place it in an oven at 45°C. Dry until the sample weight no longer changes, that is, reaches a constant weight, to ensure that the moisture in the sample is completely removed.

[0054] b. Place the dried sample into a muffle furnace, set the temperature to 800°C and last for 15 minutes to prepare modified phosphogypsum;

[0055] High temperature treatment: The dried phosphogypsum sample is transferred to a muffle furnace and the furnace temperature is set to 800°C. The sample is heated for 15 minutes to allow the phosphogypsum to undergo high temperature calcination and transform into modified phosphogypsum.

[0056] Cooling and collection: After the high temperature treatment is completed, turn off the muffle furnace and wait for the temperature in the furnace to naturally drop to room temperature. Take out the modified phosphogypsum sample and put it in a dryer to cool it to room temperature to avoid moisture absorption.

[0057] c. The above modified phosphogypsum combined with Achromobacter xylose oxidizing to fix and remove F - .

[0058] Cultivation of Achromobacter xylosoxidans: According to the method in step a, activate and culture Achromobacter xylosoxidans to the logarithmic growth phase.

[0059] Mixing the modified phosphogypsum with the bacterial solution: Add the prepared modified phosphogypsum in a certain proportion, 4 g / L in this embodiment, to the culture solution containing Achromobacter xylosoxidans, and stir thoroughly to ensure that the modified phosphogypsum and the bacterial solution are evenly mixed.

[0060] Preparation of fluoride-containing water samples: Dissolve sodium fluoride in deionized water to prepare simulated fluoride-containing water samples of different concentrations.

[0061] Fixed removal of F-experiment: Add simulated fluoride-containing water sample to the mixed system of modified phosphogypsum and Achromobacter xylosoxidans. Adjust the pH value of the mixed system to the optimal condition, pH=7 in this embodiment, put it in a constant temperature shaking incubator, control the temperature to 37°C, and shake at a speed of 120 times / minute for cultivation.

[0062] Sample collection and analysis: Culture broth samples were collected at set time points and the supernatant and precipitate were separated by centrifugation. The fluoride ion concentration in the supernatant was determined using the fluoride ion selective electrode method to evaluate the defluoridation effect. The precipitate was subjected to XRD and SEM analysis to determine the characteristics of the modified phosphogypsum and mineralized products.

[0063] Data analysis: According to the fluoride ion concentration measurement results of Example 1, the fluoride ion removal rate of each treatment group was calculated. The effects of different calcium ion concentrations, pH conditions, urea concentrations and culture time on the defluoridation effect were analyzed. The schematic diagram of defluoridation by combining modified phosphogypsum with Achromobacter xylosoxidans with different dosages is shown in the attached figure. Figure 4 The schematic diagram of fluoride removal by modified phosphogypsum combined with Achromobacter xylosoxidans under different pH conditions is shown in the attached figure. Figure 5 Through XRD and SEM results, the SEM images of modified phosphogypsum and the combined system fixing F- are shown in the attached Figure 6 As shown in the attached XRD diagram of modified phosphogypsum and combined system Figure 7 As shown, the characteristics of the mineralized products were evaluated.

[0064] Implementation effect:

[0065] The present invention provides a method for the microbial mineralization of calcium chloride to F - The removal effect of F was studied and the products were analyzed by characterization. The removal of F by modified phosphogypsum combined with Achromobacter xylose oxidizing - The results and product analysis are as follows:

[0066] (1) Removal of F from microbial mineralization - The study was conducted from four different influencing factors. 2 When the concentration of F increases from 500 mg / L to 1.5 g / L, - The removal rate first increased and then stabilized, from 77% to 90% until it stabilized at around 90%. When 6≤pH≤8, solution F - The removal rate of F was basically maintained at about 90%. As the urea concentration increased from 20g / L to 30g / L, - The removal rate of F was decreasing from 89% to 70%. - The adsorption was mainly concentrated in the first 3 days and became stable after the 3rd day. The mineralization products formed inorganic carbonate amorphous crystals mainly composed of calcium carbonate.

[0067] (2) Fluoride removal by Achromobacter xylosoxidans alone was studied under two conditions. - The results showed that as the F- concentration increased from 1.5 mg / L to 10 mg / L, the removal rate also increased. When the initial F- concentration was 5 mg / L, the removal rate of Achromobacter xylosoxidans to F - The adsorption rate can reach about 20% to 30%. When pH 6≤pH≤8, the most suitable pH value for the removal of fluoride by Achromobacter xylosoxidans is 7, and the highest adsorption rate can reach 32.92%.

[0068] (3) Modified phosphogypsum combined with Achromobacter xylose oxidizing to remove F- The adsorption efficiency of F- was studied from three aspects: dosage, comparison with phosphogypsum combined with Achromobacter xylosoxidans, and pH conditions. The following results were obtained: the optimal dosage of modified phosphogypsum combined with Achromobacter xylosoxidans for the fixed removal of F- was 4g / L, and the removal rate could reach 75% to 77%. Compared with phosphogypsum combined with Achromobacter xylosoxidans, the removal rate of F- by 4g / L modified phosphogypsum was higher after cultivation, while the removal rate of F- by phosphogypsum combined with Achromobacter xylosoxidans reached 14% to 16%. When 6≤pH≤8, the optimal pH for the combined fluoride removal rate was 7.

[0069] The present invention determines the optimal dosage and pH conditions of modified phosphogypsum to achieve the highest fluoride ion removal rate through the analysis of the experimental data of Example 2. The physical and chemical properties of the modified phosphogypsum and the characteristics of the mineralized products under the synergistic effect of the modified phosphogypsum and Achromobacter xylosoxidans are verified by XRD and SEM analysis, further confirming the effectiveness of the modified phosphogypsum combined with microbial induced mineralization technology.

[0070] The above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for removing fluoride from water by microbial induced mineralization, characterized in that: The method comprises the following steps: a. Using Achromobacter xylosoxidans as a microbial source; b. adding calcium chloride to the urea culture solution of Achromobacter xylose oxidans to form a microbial mineralization system; c. Use the above-mentioned microbial mineralization system to carry out microbial mineralization and fluoride removal.

2. The method according to claim 1, characterized in that: The amount of calcium chloride added in the method is 500 mg / L to 1.5 g / L. Under this condition, F - The removal rate increases with the increase of calcium chloride addition.

3. The method according to claim 1, characterized in that: In the method, when the pH condition is between 6 and 8, F in the solution - The removal rate was maintained at 90%.

4. The method according to claim 1, characterized in that: The urea concentration in the method is 20 g / L to 30 g / L. Under this condition, F - The removal rate decreases with the increase of urea concentration.

5. The method according to claim 1, characterized in that: In the method, microbial mineralization is carried out on F - The adsorption was mainly concentrated in the first 3 days and tended to be stable after the 3rd day.

6. A method for removing fluoride from water by using modified phosphogypsum in combination with Achromobacter xylosoxidans, characterized in that: The method comprises the following steps: a. Pass the obtained phosphogypsum sample through a 200-mesh standard sieve and dry it in an oven at 45°C to constant weight; b. Place the dried sample into a muffle furnace, set the temperature to 800°C and last for 15 minutes to prepare modified phosphogypsum; c. The above modified phosphogypsum combined with Achromobacter xylose oxidizing to fix and remove F - .

7. The method according to claim 6, characterized in that: The optimal dosage of the modified phosphogypsum is 4 g / L.

8. The method according to claim 1, characterized in that: The modified phosphogypsum combined with Achromobacter xylosoxidans to fix and remove F - The optimal pH is 7.

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