Method for repairing arsenic-containing water body by utilizing manganese ion to promote algal bacterial biofilm

Abstract

The application discloses a method for repairing arsenic-containing water bodies by using manganese ions to promote algal bacterial biofilm, and relates to the field of water treatment. The method comprises the following steps: (1) collecting water organism skin as a microbial source, culturing in a culture medium, and obtaining algal bacterial biofilm after centrifugal treatment; (2) adding the algal bacterial biofilm and divalent manganese ions into the water body to be repaired for culture. The algal bacterial biofilm is prepared from the biological components of the skin which widely exists in the water environment, and the algal bacterial biofilm has high arsenic (As) resistance and can grow rapidly in the As-containing water body. The divalent manganese ions are oxidized by the microorganisms to generate manganese oxides on the surface of the algal bacterial biofilm, so that the As in the water can be adsorbed or co-precipitated, thereby improving the As fixation capacity of the algal bacterial biofilm. The algal bacterial biofilm and the manganese oxides can also rapidly oxidize As(III) into As(V) and stably fix the As(V).

Description

Technical Field

[0001] This invention relates to the field of water treatment, and in particular to a method for remediating arsenic-containing water bodies by using manganese ions to promote algal biofilm formation. Background Technology

[0002] Arsenic (As) is the 20th most abundant element in the Earth's crust and is a prevalent carcinogen in the environment. Natural and human activities, including geological processes, rock weathering, mining, metal smelting, and the use of As-containing agricultural chemicals, have led to severe As pollution of groundwater and surface water globally. As has a high mobility in water bodies and easily enters the food chain. Human exposure to As can cause various diseases such as digestive discomfort, anemia, and neuropathic pain, and can induce various cancers such as skin cancer, lung cancer, and liver cancer, posing a significant threat to life. Therefore, the remediation of As-polluted water bodies is urgent. As exists in water bodies mainly in the form of pentavalent arsenate [As(V)] and trivalent arsenite [As(III)], with As(III) exhibiting higher toxicity and mobility than As(V). As-containing wastewater generated by geological processes and mining activities is one of the main sources of As in the environment, containing large amounts of As(III) that urgently need remediation.

[0003] Traditional asphalt (As) remediation technologies include physical, chemical, and biological methods. While these methods have been proven effective in removing As from water bodies, they all have limitations in practical applications. For example, physical remediation utilizes functional materials such as biochar, zeolite, and clay minerals to rapidly adsorb As, but the limited adsorption capacity of these materials leads to poor sustainability and requires subsequent maintenance. Chemical remediation uses chemical precipitants to precipitate As, but the resulting As-containing sludge causes secondary pollution. Biological remediation utilizes plants such as centipede grass and vetiver grass to absorb As, but their slow growth and high nutrient requirements limit their effectiveness. Therefore, seeking an efficient As treatment strategy that can be widely applied in aquatic environments is of great significance. Summary of the Invention

[0004] This invention provides a method for remediating arsenic-containing water bodies by using manganese ions to promote algal biofilm. The method utilizes microbial components in the crust to cultivate and form an algal biofilm. The microorganisms can mediate the conversion of divalent manganese ions into manganese oxides on the algal biofilm, thereby enhancing the arsenic (As) fixation capacity of the algal biofilm and ensuring the stability of As fixation.

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation, comprising the following steps:

[0006] (1) Collect aquatic organism crusts as a source of microorganisms, culture them in a culture medium, and obtain algal biofilms after centrifugation.

[0007] (2) Add algae and bacteria biofilm and divalent manganese ions to the water body to be restored for cultivation.

[0008] As a preferred embodiment, in step (2), the amount of algae biofilm added is 1-5 g / L.

[0009] As a preferred option, in step (1), the culture conditions are a temperature of 20-30℃, 12 hours of light and 12 hours of darkness per day, and a culture period of 7-14 days.

[0010] As a preferred option, in step (2), the culture conditions are a temperature of 20-30℃, 12 hours of light and 12 hours of darkness per day, adding pH buffer to balance the pH to neutral water, and a culture time of more than 2 days.

[0011] As a preferred option, in step (2), the pH buffer is 0.1 mmol / L HEPES.

[0012] As a preferred embodiment, in step (2), the amount of divalent manganese ions added is 1-60 mg / L.

[0013] As a preferred option, in step (2), the divalent manganese ions are sourced from MnCl2.

[0014] As a preferred embodiment, in step (1), the culture medium comprises 1.5 g / L NaNO3, 0.04 g / L K2HPO4·3H2O, 0.075 g / L MgSO4·7H2O, 0.036 g / L CaCl2·2H2O, 0.006 g / L citric acid, 0.006 g / L ferric ammonium citrate, 0.001 g / L EDTA, 0.02 g / L Na2CO3, 2.86 mg / L H3BO3, 1.81 mg / L MnCl2·4H2O, 0.222 mg / L ZnSO4·7H2O, 0.390 mg / L Na2MoO4·2H2O, 0.079 mg / L CuSO4·5H2O, and 0.049 mg / L Co(NO3)2·6H2O.

[0015] As a preferred option, in step (1), the aquatic organism crust originates from an As-contaminated tailings wetland area.

[0016] As a preferred method, the centrifugation conditions are 2500-3500 rpm for 10-20 min.

[0017] Compared with the prior art, the embodiments of the present invention have the following beneficial effects:

[0018] 1. This application cultivates biological components in crusts that are widely present in aquatic environments to prepare algal biofilms. The algal biofilms used have high (As) tolerance and grow rapidly in water containing As. The oxidation of divalent manganese salt ions by microorganisms produces manganese oxides on the surface of the algal biofilm, which can adsorb or co-precipitate As in the water, thereby improving the As fixation capacity of the algal biofilm. In addition, the formed manganese oxides can also simultaneously oxidize As(III), oxidizing As(III) into As(V) which is easily fixed and fixing it, thus ensuring the stability of the fixed As.

[0019] 2. This application provides a low-cost and efficient As removal strategy. As one of the nature-based solutions, it uses green remediation materials, has no secondary pollution, and is inexpensive. It can be applied to the remediation of widely existing As-contaminated water bodies. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the principle of using manganese ions to promote the remediation of arsenic-containing water bodies using algal biofilm.

[0021] Figure 2 This refers to the changes in As speciation in water samples after 22 days of microbial remediation using divalent manganese salt combined with algae and bacteria in Example 1 of this invention (Note: DMA stands for pentavalent dimethyl As; UNKNOWN1 represents unidentified organic As speciation).

[0022] Figure 3 The elemental distribution of algae and bacteria biofilm collected 22 days after water sample treatment in step (2) of Embodiment 1 of the present invention, based on SEM-EDS analysis.

[0023] Figure 4 This refers to the changes in the extracellular As speciation of algal biofilms in the As detection step after water sample treatment in Embodiment 1 of the present invention (Note: DMA is pentavalent dimethyl As; MMA is pentavalent monomethyl As; UNKNOWN1 is an unidentified organic As speciation).

[0024] Figure 5 This refers to the changes in intracellular As morphology in algal biofilms during the As detection step after water sample treatment in Embodiment 1 of the present invention (Note: DMA is pentavalent dimethyl As; MMA is pentavalent monomethyl As; UNKNOWN2 is an unidentified organic As morphology). Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] Crusts are widely present in aquatic environments such as rivers, lakes, wetlands, and paddy fields. They are aggregates of inorganic minerals formed by algae and bacteria and their extracellular polymers. They can grow rapidly in harsh environments and accumulate arsenic (As), making them good As removal agents. However, their biosorption capacity is limited, and they cannot efficiently absorb As. Manganese (Mn) oxides have As adsorption and oxidation capabilities, capable of oxidizing As(III) to As(V) and fixing it, making them effective As removal agents. However, the natural oxidation to form Mn oxides is extremely slow, while biological oxidation processes can effectively promote the formation of Mn oxides. Crusts have been found to accumulate Mn in the form of Mn oxides, indicating their potential for Mn oxidation, thereby promoting As removal. Therefore, this application uses a typical crust—aquatic biological crust—as a microbial source, cultivates its biological components (algae and bacteria biofilm) for the remediation of As-contaminated water, and utilizes Mn to enhance its As fixation capacity. Since the aquatic organism crusts collected in this study have typical crust characteristics, and the algal and bacterial biofilms obtained by culturing them have similar functions in remediating As polluted water bodies, the laws revealed by using them as research materials have universality.

[0027] Example 1

[0028] A method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation includes the following steps:

[0029] (1) Preparation of algal biofilm: Aquatic biological crusts were collected from an As-contaminated wetland of a lead-zinc tailings mine in Guangdong Province, stored in sterile centrifuge tubes, and transported back to the laboratory in a 4℃ vehicle refrigerator for the cultivation of algal biofilm. The aquatic biological crusts collected in the previous stage were rinsed three times with deionized water, and 5g of aquatic biological crusts were weighed and suspended in 50mL of ultrapure water. The mixture was shaken for 10min to fully disperse the aquatic biological crusts. 10mL of the aquatic biological crust suspension was added to 90mL of sterile BG11 medium and placed in an Erlenmeyer flask for cultivation. The cultivation conditions were 25℃ and light / dark conditions of 12h / 12h. After 7 days of cultivation, the mixture was centrifuged at 3000rpm for 10min, and the supernatant was removed to obtain the algal biofilm.

[0030] (2) Remediation of As-contaminated water: BG11 medium supplemented with 5 mg / L As(III) was used as a simulated As-contaminated water sample. The algal biofilm cultured in step (1) was then inoculated at a concentration of 1 g / L, and Mn (MnCl2) at concentrations of 0, 1, 5, 10, 20, 40, and 60 mg / L was added. The experimental groups were named Mn0-Mn60, and a blank group without algal biofilm was set up with a Mn concentration of 60 mg / L, named CK60. Under the same culture conditions, the initial pH was controlled at 7.0, and 0.1 mmol / L HEPES was added to buffer pH changes to simulate a neutral water environment. Water samples were collected on days 0, 2, 5, 9, 15, and 22. The concentrations of Mn and As in the solution were detected by ICP-OES, and the As speciation was detected by HPLC-ICP-MS. On day 22, the algal biofilm was collected by centrifugation at 4500 rpm for 10 min. The removal rates of total As and Mn in the water sample after 22 days of remediation are shown in Table 1 below. The changes in the speciation of As in the water sample on day 22 are shown in Table 1 below. Figure 2 As shown.

[0031] The formula for BG11 medium is as follows: 1.5 g / L NaNO3, 0.04 g / L K2HPO4·3H2O, 0.075 g / L MgSO4·7H2O, 0.036 g / L CaCl2·2H2O, 0.006 g / L citric acid, 0.006 g / L ferric ammonium citrate, 0.001 g / L EDTA, 0.02 g / L Na2CO3, 2.86 mg / L H3BO3, 1.81 mg / L MnCl2·4H2O, 0.222 mg / L ZnSO4·7H2O, 0.390 mg / L Na2MoO4·2H2O, 0.079 mg / L CuSO4·5H2O, and 0.049 mg / L Co(NO3)2·6H2O.

[0032] Table 1 - Removal rates of total As and Mn in water samples on day 22

[0033] sample Mn0 Mn1 Mn5 Mn10 Mn20 Mn40 Mn60 CK60 Total As removal rate (%) 63.3 58.9 68.8 67.0 78.2 71.5 79.6 35.0 Mn removal rate (%) - 100.0 99.1 99.0 99.6 73.0 68.3 50.9

[0034] As shown in Table 1 above and Figure 2 As shown, algal biofilms combined with Mn can effectively oxidize As(III), ultimately removing both As and Mn. When the Mn concentration is above 1 mg / L, the removal rate of As by algal biofilms combined with Mn is higher than that of algal biofilms alone. Furthermore, the removal rate of As gradually increases with increasing Mn concentration. When the Mn concentration is 20-60 mg / L, the removal rate of As by algal biofilms can reach over 70%, demonstrating high removal efficiency. Simultaneously, combined with… Figure 1As shown, As(III) is gradually oxidized to form As(V), and further transformed into organic As forms such as pentavalent dimethyl As, thereby reducing toxicity, indicating that this method has a remediation effect on As(III).

[0035] As distribution in algal and bacterial biofilm fixation: The algal and bacterial biofilm collected 22 days after step (2) was fixed with 2.5% glutaraldehyde, dehydrated using an ethanol gradient, and then subjected to biological sample preparation for observation by scanning electron microscopy (SEM). Results are shown below. Figure 3 It was found that the algal biofilm contained a large number of filamentous algae and formed layered Mn oxides, and both the algae and the Mn oxides adsorbed As.

[0036] As morphology of immobilized asphalt in algal biofilms: Extracellular and intracellular asphalt were extracted from algal biofilms collected 22 days after step (2) using 0.1 mol / L KH2PO4 / K2HPO4 buffer solution (pH 5.95) and methanol / H2O (1:1, v / v) solution, respectively, and their morphology was analyzed. The results of extracellular and intracellular asphalt morphology are as follows: Figure 4-5 As shown, the extracellular / intracellular As(V) ratio increases with increasing Mn concentration. Considering the low toxicity and low migration of As(V), this indicates that Mn treatment of algal biofilms is beneficial for enhancing As fixation.

[0037] After extracting extracellular / intracellular As, the remaining solid phase was washed with ultrapure water, pre-frozen at -80°C, then freeze-dried and microwave-digested to detect the total As fixed in the algal biofilm. The results are shown in Table 2 below.

[0038] Mn treatment can effectively improve the As fixation capacity of algal biofilms. Compared with the Mn0 group, the As fixation capacity of algal biofilms after Mn treatment increased by up to 6.3 times (Mn40).

[0039] Table 2 - Total As fixation capacity of algal and bacterial biofilms

[0040]

[0041] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. In particular, it should be noted that any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention for those skilled in the art.

Claims

1. A method for remediating arsenic-containing water bodies by utilizing manganese ions to promote algal biofilm formation, characterized in that, Includes the following steps: (1) Collect aquatic organism crusts as a source of microorganisms, culture them in a culture medium, and obtain algal biofilms after centrifugation; (2) Add algal biofilm and divalent manganese ions to the water body to be remediated for cultivation; In step (1), the aquatic biological crust is derived from arsenic-polluted tailings wetland areas; in step (2), the divalent manganese ions are derived from MnCl2, and the amount of algae and bacteria biofilm added is 1-5 g / L.

2. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 1, characterized in that, In step (1), the culture conditions are a temperature of 20-30℃, 12 hours of light exposure and 12 hours of darkness exposure per day, and a culture period of 7-14 days.

3. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 1, characterized in that, In step (2), the culture conditions are a temperature of 20-30℃, 12 hours of light exposure and 12 hours of darkness exposure per day, pH buffer solution is added to balance the pH to neutral water, and the culture time is more than 2 days.

4. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 3, characterized in that, In step (2), the pH buffer is 0.1 mmol / L HEPES.

5. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 1, characterized in that, In step (2), the content of divalent manganese ions is 1-60 mg / L.

6. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 1, characterized in that, In step (1), the culture medium includes 1.5 g / L NaNO3, 0.04 g / L K2HPO4·3H2O, 0.075 g / L MgSO4·7H2O, 0.036 g / L CaCl2·2H2O, 0.006 g / L citric acid, 0.006 g / L ferric ammonium citrate, 0.001 g / L EDTA, 0.02 g / L Na2CO3, 2.86 mg / L H3BO3, 1.81 mg / L MnCl2·4H2O, 0.222 mg / L ZnSO4·7H2O, 0.390 mg / L Na2MoO4·2H2O, 0.079 mg / L CuSO4·5H2O, and 0.049 mg / L Co(NO3)2·6H2O.

7. The method for remediating arsenic-containing water bodies using manganese ions to promote algal biofilm formation as described in claim 1, characterized in that, In step (1), the centrifugation conditions are 2500-3500 rpm for 10-20 min.

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