An arsenic wastewater treatment agent, preparation method, application and arsenic wastewater treatment method

Abstract

The present invention belongs to the technical field of wastewater treatment, and specifically relates to an arsenic wastewater treatment agent, a preparation method, an application, and an arsenic wastewater treatment method. The arsenic wastewater treatment agent includes a carrier and a bacterial suspension adsorbed and fixed on the carrier; the carrier is iron-modified biochar; the strain in the bacterial suspension is Bacillus subtilis ( Bacillus subtilis ) W7. The bacteria-carbon composite material prepared by freeze-drying in the present invention can not only be compatible with multifunctional additives (such as iron oxides), but also quickly activate the metabolic activity of the strain through rehydration, and is suitable for groundwater remediation with large temperature differences and high storage requirements or the production of industrial prefabricated remediation agents.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to an arsenic wastewater treatment agent, a preparation method, an application and an arsenic wastewater treatment method. Background Art

[0002] Arsenic is an element widely distributed in the natural environment. When the arsenic content in water accumulates to a certain extent, it will harm aquatic organisms in the water and endanger human health through food chains and other channels. For the treatment of arsenic-polluted wastewater, treatment agents such as modified biochar and microbial agents are often applied, and the combination of the two is also used for treatment. The current treatment technologies for arsenic-polluted wastewater have significant limitations: 1) The single treatment efficiency is insufficient. For example, although the application of iron-based biochar alone can adsorb part of arsenic, traditional modification methods such as low iron loading or non-optimized pyrolysis processes are prone to cause saturation of adsorption sites or desorption risks; while the application of microbial agents alone can transform the arsenic form, but they have poor tolerance to high-concentration arsenic and cannot block the absorption by aquatic plants or animals; 2) The existing combined treatment technologies lack a synergistic mechanism and do not optimize the compatibility of bacteria and biochar, resulting in blockage of biochar pores, thereby inhibiting the bacterial activity and the repair efficiency is lower than that of single components; 3) The treatment schemes have weak universality, high costs and are prone to secondary pollution.

[0003] In the prior art, physical adsorption, co-culture, chemical cross-linking and embedding methods are often used to load strains on biochar. However, the loading amount of physical adsorption is low and it is easy to fall off, the co-culture period is long and the efficiency is low; the chemical reagents in chemical cross-linking are easy to damage the bacterial activity; the mass transfer in the embedding method is limited. At the same time, in the long-term repair scenario, the bacteria adsorbed by physical adsorption are easily washed off by the environment, chemical cross-linking may introduce secondary pollution, and it is difficult to control the loading density in co-culture. Therefore, there is an urgent need for some bacteria-biochar composite materials and their preparation methods that can maintain a high survival rate of strains, ensure uniform loading and extend the material stability, which is of great significance for efficient arsenic pollution treatment. Summary of the Invention

[0004] The purpose of the present invention is to provide an arsenic wastewater treatment agent, a preparation method, an application and an arsenic wastewater treatment method, so as to overcome the deficiencies of the prior art and synergistically reduce the arsenic pollution content in water by strain W7 and iron-modified biochar.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] In the first aspect, the present invention provides an arsenic wastewater treatment agent, which includes a carrier and a bacterial suspension adsorbed and fixed on the carrier;

[0007] The carrier is iron-modified biochar;

[0008] The strain in the bacterial suspension is Bacillus subtilis (Bacillus subtilis) W7.

[0009] In some other embodiments, the mass ratio of carbon to iron in the iron-modified biochar is 1:(0.025 - 1.5);

[0010] The pH of the iron-modified biochar is 8 - 9, the conductivity is 1800 - 1900 μs / cm, the ash content is 25 - 30 wt%, the specific surface area is 10 - 12 m 2 / g, the total pore volume is 0.05 - 0.07 cm 3 / g, the average pore diameter is 20 - 22 nm, the adsorption pore diameter is 22 - 24 nm, and the desorption pore diameter is 17 - 19 nm.

[0011] In some other embodiments, the OD600 in the bacterial suspension is 0.9 - 1.1; the ratio of the carrier to the bacterial suspension is 1 g:(5 - 30) mL.

[0012] Second, the present invention provides a preparation method of the arsenic wastewater treatment agent described in the first aspect, including the following steps: under aseptic conditions, mixing the iron-modified biochar with the bacterial suspension, and then obtaining the product after freeze-drying.

[0013] In some other embodiments, the preparation method of the iron-modified biochar includes the following steps:

[0014] (1) Heating the straw powder to 350 - 450 °C under anoxic conditions, holding for 1 - 3 h, cooling to room temperature, and then sieving to obtain biochar;

[0015] (2) Adding a mixture of biochar and an iron source to water for reaction, drying, heating to 350 - 450 °C under anoxic conditions, holding for 0.5 - 1 h, cooling to room temperature, and then storing in a sealed manner to obtain the iron-modified biochar.

[0016] In some other embodiments, in step (1), the particle size of the straw powder < 1 mm, and the particle size of the biochar is 0.053 mm - 1 mm;

[0017] In step (2), the iron source is one of ferric nitrate nonahydrate, ferrous chloride, ferric chloride, and ferric sulfate;

[0018] The mixing mass ratio of iron in the biochar and the iron source is 1:(0.025 - 1.5);

[0019] The solid-liquid ratio of the mixture to water is 1 g:(25 - 35) mL;

[0020] The reaction is to oscillate and react at a constant temperature of 25 - 30 °C at 150 - 200 r / min for 10 - 15 h;

[0021] The drying temperature is 50-60°C.

[0022] In some other embodiments, the method for preparing the bacterial suspension comprises the following steps:

[0023] Inoculate Bacillus subtilis ( Bacillus subtilis ) W7 into the sterilized LB liquid medium, and perform light-shielding culture to obtain a seed solution. After mixing the seed solution with the sterilized medium, continue light-shielding culture to obtain the bacterial suspension;

[0024] The sterilization temperature is 121°C and the time is 0.5-1 h; the light-shielding culture is carried out at a constant temperature of 25-30°C and shaken at 150-200 r / min for 20-25 h;

[0025] The continued light-shielding culture is carried out at a constant temperature of 25-30°C and shaken at 150-200 r / min for 1-2 days;

[0026] The volume ratio of the seed solution to the sterilized medium is 1:(20-30);

[0027] The OD600 of the seed solution is 0.6-1;

[0028] The OD600 of the bacterial suspension is 0.9-1.1.

[0029] In some other embodiments, the ratio of the iron-modified biochar to the bacterial suspension is 1 g:(5-30) mL;

[0030] The mixing is carried out at a constant temperature of 30-40°C and shaken at 150-200 r / min for 1-12 h;

[0031] The freeze-drying is first carried out at -75~ -85°C for 0.5-2 h, and then at -45~ -55°C under vacuum for 20-30 h.

[0032] In a third aspect, the present invention provides the application of the arsenic wastewater treatment agent described in the first aspect in an arsenic-contaminated water body.

[0033] In a fourth aspect, the present invention provides a method for treating arsenic wastewater, which comprises applying the arsenic wastewater treatment agent described in the first aspect to an arsenic-contaminated water body;

[0034] The arsenic content in the water body is 0-100 mg / L, and the temperature of the water body is 10-30°C;

[0035] The application amount of the arsenic wastewater treatment agent is 1-5 g / L, and the application time is 20-30 h.

[0036] The beneficial effects of the present invention:

[0037] (1) The iron-modified biochar prepared in the present invention serves as the main active component for arsenic adsorption. Through coordination and chemical complexation, it significantly enhances the adsorption capacity. At the same time, the iron-modified biochar has an appropriate pH environment, high conductivity, inorganic phase distribution, and pore structures such as an enlarged specific surface area and pore volume, enabling efficient removal of arsenic pollutants and providing a solution with stable performance and controllable cost for industrial applications.

[0038] (2) The strain W7 in the present invention completes the full cycle from adaptation to efficient reproduction within 12 hours, demonstrating the potential for short-term high-density cultivation and high tolerance to high concentrations of arsenic, and is suitable for fields such as industrial fermentation and bioremediation.

[0039] (3) The synergistic effect between the bacterial cells and the iron-modified biochar in the present invention is enhanced. Its mechanism integrates physicochemical adsorption (FB-3 rapidly immobilizes arsenate), bioaugmentation (W7 secretes extracellular polymers to drive arsenic reduction and mineralization), and structural protection (biochar maintains the long-term activity of the bacterial cells); it combines high efficiency and sustainability, providing an innovative solution for the treatment of arsenic pollution in farmland and having the potential for industrial promotion.

[0040] (4) The freeze-dried bacteria-biochar composite material in the present invention can not only be compatible with multifunctional additives (such as iron oxides), but also rapidly activate the metabolic activity of the strain through rehydration, and is suitable for groundwater remediation with large temperature differences and high storage requirements or the production of industrial prefabricated remediation agents. Its technical advantages of high activity retention and stability make it the preferred loading method for efficient arsenic pollution treatment.

[0041] (5) The treatment agent in the present invention has the advantages of simple process, convenient operation, low treatment cost, high treatment efficiency, good removal effect, etc. It has high use value and good application prospects, providing a green and environmentally friendly biological approach for the treatment of arsenic in water bodies. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention.

[0043] Figure 1 It is the adsorption rate of As by the original biochar and the iron-modified biochars prepared with different iron modification ratios in the embodiments of the present invention, where BC is the original biochar, FB-1 is the iron-modified biochar with a carbon-iron mass ratio of 1:0.025, FB-2 is the iron-modified biochar with a carbon-iron mass ratio of 1:0.05, FB-3 is the iron-modified biochar with a carbon-iron mass ratio of 1:0.1, FB-4 is the iron-modified biochar with a carbon-iron mass ratio of 1:1.25, and FB-5 is the iron-modified biochar with a carbon-iron mass ratio of 1:1.5;

[0044] Figure 2Scanning electron microscope images of the original biochar and iron-modified biochar FB-3 in the embodiments of the present invention, where A, B, and C are the scanning electron microscope images of the original biochar at scales of 10 μm, 5 μm, and 2 μm; D, E, and F are the scanning electron microscope images of the iron-modified biochar FB-3 at scales of 10 μm, 5 μm, and 2 μm;

[0045] Figure 3 EDS quantitative result diagram of the original biochar and iron-modified biochar FB-3 in the embodiments of the present invention;

[0046] Figure 4 In the embodiments of the present invention, the growth curve, adsorption effect, and tolerance curve of strain W7 were tested at different times, where A is the growth curve, B is the adsorption effect, and C is the tolerance curve;

[0047] Figure 5 In the embodiments of the present invention, the effects of the inoculation ratio and fixation time of W7FB on arsenic adsorption performance, where A is the inoculation ratio and B is the fixation time;

[0048] Figure 6 Scanning electron microscope test diagram of W7FB in the embodiments of the present invention, where A, B, and C are the scanning electron microscope images of W7FB at scales of 10 μm, 5 μm, and 2 μm;

[0049] Figure 7 In the embodiments of the present invention, the arsenic adsorption effect of W7FB at different times;

[0050] Figure 8 In the embodiments of the present invention, the fitting results of the pseudo-first-order and pseudo-second-order kinetic models for the arsenic adsorption process of W7FB, where A is the pseudo-first-order kinetic model and B is the pseudo-second-order kinetic model;

[0051] Figure 9 Fitting results of the isothermal adsorption model in the embodiments of the present invention;

[0052] Figure 10 In the embodiments of the present invention, the water body repair effects at different dosages and different temperatures. Detailed implementation manners

[0053] Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Specific conditions are not indicated in the embodiments and are carried out according to conventional conditions or conditions recommended by the manufacturer. Components not indicated by the producer are all conventional products that can be obtained commercially.

[0054] Example 1

[0055] (1) Preparation of iron-modified biochar

[0056] Preparation of biochar (labeled as BC): The corn straw powder passed through a 1-mm sieve was placed into a 200-ml covered porcelain crucible, sealed with tin foil, and then placed in a muffle furnace. Under anoxic conditions, it was heated from room temperature to 400 °C at a heating rate of 5 - 10 °C / min and maintained for two hours. After cooling to room temperature, it was passed through 1-mm and 0.053-mm sieves, and the middle part was the original biochar (labeled as BC).

[0057] Preparation of Fe-modified biochar (labeled as FB): The original biochar was mixed with ferric nitrate nonahydrate in the ratios of carbon to iron mass ratio of 1:0.025, 1:0.05, 1:0.1, 1:1.25, and 1:1.5, placed in a conical flask containing deionized water (solid-liquid ratio of 1:30), and reacted in a constant-temperature shaker at 30 °C and 180 r / min for 12 hours. After shaking, the conical flask was repeatedly washed with deionized water, and the mixture was placed on a glass tray and dried in an oven at 50 °C. After drying, the mixture was sealed with tin foil and placed in a muffle furnace. Under anoxic conditions, it was heated from room temperature to 400 °C at a heating rate of 5 - 10 °C / min and maintained for 30 minutes. After taking it out, it was sealed and stored, and labeled as Fe-modified biochar FB-1 (carbon-iron mass ratio of 1:0.025), FB-2 (carbon-iron mass ratio of 1:0.05), FB-3 (carbon-iron mass ratio of 1:0.1), FB-4 (carbon-iron mass ratio of 1:1.25), and FB-5 (carbon-iron mass ratio of 1:1.5) respectively.

[0058] The prepared original biochar (BC) and Fe-modified biochars (FB) with different ratios were tested, and the results are as follows:

[0059] Figure 1 The removal rates of As by the original biochar and Fe-modified biochars prepared with different Fe modification ratios, where BC is the original biochar, FB-1 is the Fe-modified biochar with a carbon-iron mass ratio of 1:0.025, FB-2 is the Fe-modified biochar with a carbon-iron mass ratio of 1:0.05, FB-3 is the Fe-modified biochar with a carbon-iron mass ratio of 1:0.1, FB-4 is the Fe-modified biochar with a carbon-iron mass ratio of 1:1.25, and FB-5 is the Fe-modified biochar with a carbon-iron mass ratio of 1:1.5; the letters (such as a, b, c) marked on the bar chart represent the results of multiple comparison tests, which are used to visually show the significant differences between different groups. If two groups are marked with the same letter, it means that their means are not significantly different statistically (p ≥ 0.05). If two groups are marked with different letters (such as a and b), it means that their means are significantly different (p < 0.05). If two letters are marked simultaneously, such as bc, it indicates that the data of this group belong to two groups with non-significant differences statistically.

[0060] From Figure 1It can be seen that the original biochar BC has a low arsenic removal rate of only 35.3% due to the lack of iron active sites. After iron modification, the adsorption performance first increases and then decreases with the increase of the iron ratio. Among the low-ratio iron-loaded (FB-1 to FB-3), FB-3 (carbon-to-iron ratio of 1:0.1) reaches the peak, and the arsenic removal rate reaches 57.2%, indicating that appropriate iron loading can effectively increase the active sites and optimize the pore structure of the material. However, excessive iron (FB-4, FB-5) leads to a significant decrease in the arsenic removal rate due to iron agglomeration and pore blockage. Therefore, FB-3 (carbon-to-iron ratio of 1:0.1) is used as the optimal iron-modified biochar in this invention, and FB-3 is used as the iron-modified biochar for further research in subsequent studies.

[0061] Table 1 shows the physical and chemical properties of the original biochar BC and the iron-modified biochar FB-3; Table 2 shows the pore structure parameters of the original biochar BC and the iron-modified biochar FB-3.

[0062] Table 1 shows the physical and chemical properties of the original biochar BC and the iron-modified biochar FB-3

[0063]

[0064] As can be seen from Table 1, the pH of the original biochar BC is 9.45 ± 0.15, and the pH of the iron-modified biochar FB-3 drops to 8.76 ± 0.11, which is closer to the neutral condition and is conducive to the electrostatic adsorption of arsenate ions. The conductivity increases from 1257 ± 2.14 μs / cm to 1823 ± 1.59 μs / cm, indicating an increase in the surface active sites and ion exchange ability of FB-3. The ash content increases from 20.7% to 28.4%, confirming the successful loading of iron oxides (the iron in the iron-modified biochar mainly exists in the form of iron oxides, such as Fe3O4, FeO(OH), γ-Fe2O3, α-Fe2O3, etc.).

[0065] Compared with the biochar modified by zero-valent iron, the iron-modified biochar FB-3 of this invention has the following advantages: enhanced adsorption performance, as iron oxides can provide more adsorption sites; improved stability, as iron oxides have good stability in the environment and can maintain the adsorption performance for a long time; the preparation method of the iron-modified biochar is relatively mature, with low cost and easy for large-scale production. As the main active component for arsenic adsorption, it significantly improves the adsorption capacity through coordination and chemical complexation. The iron-modified biochar of this invention has an appropriate pH environment, high conductivity, and optimized inorganic phase distribution, and can efficiently remove arsenic pollutants in water, providing a solution with stable performance and controllable cost for industrial applications.

[0066] Table 2 shows the pore structure parameters of the original biochar BC and the iron-modified biochar FB-3

[0067]

[0068] As can be seen from Table 2, the BET specific surface area of the original biochar BC is only 7.17 m² / g, the total pore volume is 0.011 cm³ / g, and the average pore diameter is 6.177 nm, indicating that it is mainly composed of micropores and the pore development is limited; while the BET specific surface area of the modified biochar FB-3 is increased to 11.965 m² / g (an increase of about 67%), the total pore volume is increased to 0.062 cm³ / g (nearly 5 times increase), and the average pore diameter is expanded to 21.041 nm, proving that iron loading effectively broadens the pores and forms a mesopore-macropore hierarchical structure. At the same time, the BJH adsorption pore diameter is reduced from 30.914 nm to 23.35 nm, and the desorption pore diameter is increased from 15.92 nm to 18.91 nm, indicating that iron oxide modification optimizes the pore connectivity and reduces the dispersion degree of pore size distribution. This structural characteristic synergistically improves the arsenic adsorption performance of the material: the enlarged specific surface area and pore volume increase the exposed area of active sites, the hierarchical pores promote the diffusion and interception of arsenate ions, and the pore size homogenization enhances the adsorption stability. The above pore regulation mechanism provides key structural support for the efficient arsenic adsorption of iron-modified biochar.

[0069] Figure 2 Fig. is the scanning electron microscope images of the original biochar BC and the iron-modified biochar FB-3, where A, B, and C are the scanning electron microscope images of the original biochar at the scales of 10μm, 5μm, and 2μm; D, E, and F are the scanning electron microscope images of the iron-modified biochar FB-3 at the scales of 10μm, 5μm, and 2μm. From Figure 2 it can be seen that the surface of the iron-modified biochar FB-3 is rougher than that of the original biochar BC and has more adsorption sites.

[0070] The EDS quantitative results of the original biochar BC and the iron-modified biochar FB-3 are shown in Table 3.

[0071] Table 3 shows the EDS quantitative results of the original biochar BC and the iron-modified biochar FB-3

[0072]

[0073] As can be seen from Table 3, through the EDS elemental analysis of biochar (BC) and its iron-modified material (FB-3), the significant impact of the iron modification process on the surface composition of the material can be clearly identified: Outstanding iron loading effect: The mass percentage of Fe increased significantly from 0.68% to 39.5% (atomic percentage increased from 0.18% to 14.95%), indicating that iron oxides (such as FeOOH, Fe3O4) were successfully loaded on the surface and pores of biochar, providing abundant active sites for arsenic adsorption. Carbon skeleton oxidation and oxygen enrichment: The mass percentage of C decreased sharply from 57.5% to 22.7% (atomic percentage decreased from 70.23% to 40.12%), indicating that part of the carbon skeleton was oxidized or formed a composite structure with iron during the modification process; at the same time, the mass percentage of O increased from 19.72% to 28.7% (atomic percentage increased from 18.06% to 38.04%), indicating a significant increase in iron oxides and surface oxygen-containing functional groups (-OH, -COOH), further enhancing the coordination adsorption ability of arsenic. Decrease in silicon content: The mass percentage of Si decreased from 22.1% to 9.1% (atomic percentage decreased from 11.53% to 6.89%), which may be due to the dissolution of part of the silicate caused by iron coverage or high-temperature modification, but has little impact on the adsorption performance. The iron-modified biochar FB-3 significantly optimized its functional characteristics as an arsenic adsorbent through the efficient loading of iron oxides and surface oxidation modification. In particular, the synergistic effect of iron and oxygen laid a chemical foundation for the subsequent combined remediation of strain W7 and is suitable for the efficient treatment of high-arsenic polluted water bodies.

[0074] Figure 3 It is the EDS quantitative result spectrum of the original biochar BC and the iron-modified biochar FB-3. The spectrum of the original biochar (BC) is dominated by carbon (C-Kα peak, 0.28 keV), followed by oxygen (O-Kα peak, 0.53 keV), and the iron signal (Fe-Kα peak, 6.4 keV) is weak. In the spectrum of the iron-modified biochar (FB-3), the intensity of the Fe-Kα peak is significantly enhanced, confirming that iron oxides are uniformly loaded on the surface of the carbon matrix in the form of nanoparticles, which is consistent with the roughened morphology observed by SEM. The significant weakening of the C-Kα peak indicates that iron covers part of the carbon structure, while the increase in the intensity of the O-Kα peak is due to the contribution of hydroxyl groups (-OH) on the surface of iron oxides and calcium-based minerals. This change in chemical composition and spectral characteristics together indicate that iron oxides synergistically enhance the chemical adsorption and physical interception ability of arsenic by providing abundant hydroxyl sites and optimizing the pore structure.

[0075] (2) Adsorption effect and growth status of arsenic by strain W7 in shake flask experiments

[0076] The strain used in the shake flask experiment of the present invention is Bacillus W7 (taxonomically named Bacillus subtilis) disclosed in the application number 202010531482.9 Bacillus subtilis ).

[0077] Preparation of bacterial suspension: Measure LB liquid culture medium into a conical flask, place it in an autoclave and sterilize at 121 °C for 20 min. Under the laminar flow hood, use a sterile inoculation loop to pick the preserved strain and inoculate it into the sterilized medium. Incubate it in a constant temperature shaker at 30 °C and 150 r / min in the dark for 24 h. At this time, the bacteria enter the logarithmic growth phase (OD600 is between 0.6 and 1), and this is used as the seed liquid.

[0078] Using LB liquid culture medium as the base liquid, inoculate the target seed liquid according to the volume ratio of 1:25 (seed liquid: base liquid), and repeat the above culture process until the OD600 of the bacterial suspension reaches about 1 (generally, the requirement can be achieved in 1-2 days). The growth curve of the strain was determined by ultraviolet-visible spectrophotometry (wavelength 600 nm) to determine the optimal ratio between the strain and carbon in the later stage.

[0079] Arsenic tolerance experiment: Incubate at 37 °C and 180 rpm in a constant temperature shaker for 18 h until the logarithmic growth phase. Take the bacterial liquid and transfer it to LB medium containing arsenic As 5+ at an inoculation amount of 1% (v / v). Add sterile arsenic solution to the final concentrations of 0, 20, 40, 60, 80, and 100 mg / L respectively. Set 3 parallels for each group and continuously shake and culture at 37 °C for 12 h. Sample every 2 h, use a microplate reader (wavelength 625 nm) to measure the absorbance of the bacterial liquid, and record the change of OD value at each time point. Observe the growth curve of strain W7 in the culture medium with different arsenic concentrations to determine its tolerance to As 5+ degree.

[0080] Arsenic adsorption experiment: The arsenic adsorption experiment is a shake flask experiment. Place the cultured seed liquid of strain W7 in a medium with an arsenic content of 50 mg / L and culture for 24 hours. Use icp-MS to detect the arsenic concentration after adsorption and calculate the removal rate.

[0081] The growth curve, adsorption effect and tolerance curve of strain W7 were tested at different times, and the results are as Figure 4 shown, where A is the growth curve, B is the adsorption effect, and C is the tolerance curve. The present invention relates to the growth characteristics of strain W7 and its application in microbial engineering. The experiment reveals its significant growth kinetic characteristics by monitoring the change of OD600 value (optical density value) of strain W7 within 0 to 12 hours, such as Figure 4As shown in A in [reference], in the initial stage (0 - 2 hours), the strain was in the lag phase, and the OD value increased slowly (from 0.2 to 0.4), indicating that the cells gradually adapted to the culture environment and initiated metabolic activities; subsequently, it entered the logarithmic growth phase (2 - 8 hours), and the OD value increased exponentially (from 0.4 to 1.0), indicating rapid cell proliferation and peak metabolic activity; until the stationary phase (8 - 12 hours), the growth rate of the OD value slowed down (from 1.0 to 1.2), indicating that nutrient limitation or metabolite accumulation led to a decrease in the growth rate. The strain W7 completed the whole cycle from adaptation to efficient reproduction within 12 hours, demonstrating the potential for short - time high - density culture and being suitable for fields such as industrial fermentation and bioremediation.

[0082] The present invention relates to the application of strain W7 in the field of arsenic adsorption and its time - dependent adsorption characteristics. Through experiments on monitoring the arsenic adsorption dynamics of strain W7 within 0 to 12 hours, it was found that its adsorption efficiency was highly correlated with the growth stage as Figure 4 shown in B in [reference]: In the initial stage (0 - 2 hours), the strain was in the growth lag phase, and the arsenic removal rate slowly increased to 23%, mainly relying on physical adsorption by surface functional groups (such as hydroxyl and carboxyl groups); in the logarithmic growth phase (2 - 8 hours), the metabolic activity of the cells increased, and the adsorption rate rapidly rose to 33%. The secretion of extracellular polymeric substances (EPS) and the chemical complexation mediated by siderophores significantly enhanced the fixation of arsenic; in the stationary phase (8 - 12 hours), the adsorption rate reached a peak of 33% and tended to balance, indicating that the cells further optimized the adsorption capacity through biomineralization or intracellular enrichment mechanisms.

[0083] The growth curves (OD600 values) of strain W7 at different arsenic concentrations indicated its significant arsenic tolerance: it could grow within the arsenic concentration range of 0 - 100 mg / L, but its proliferation ability decreased with the increase in arsenic concentration. The specific results are as Figure 4 shown in C in [reference]: Under arsenic - free conditions (0 mg / L): The OD600 continuously increased from 0.32 to 1.12 (12 hours), showing a typical logarithmic growth phase, and the activity of the strain was not inhibited; at low arsenic concentrations (20 - 40 mg / L): The OD600 reached 0.79 and 0.75 respectively at 12 hours, a decrease of 29.5% and 33.0% compared with the blank group, indicating mild inhibition but still maintaining relatively high metabolic activity; at high arsenic concentrations (60 - 100 mg / L): The peak OD600 decreased to 0.70 (60 mg / L) and 0.62 (100 mg / L), and the inhibition rates were 37.5% and 44.6% respectively, and the logarithmic growth phase was shortened (the growth rate slowed down after 8 hours), suggesting that arsenic stress led to the cells entering the stationary phase in advance; the half - inhibitory concentration (IC50): Based on the data at 12 hours, the IC50 was approximately 80 - 100 mg / L (the concentration range corresponding to a 50% decrease in OD600).

[0084] Conclusion: Strain W7 has strong tolerance to high concentrations of arsenic (≤100 mg / L) and is suitable for bioremediation of medium- and high-arsenic contaminated environments (such as industrial wastewater and high-arsenic groundwater). However, its optimal activity window is an arsenic concentration of ≤60 mg / L (inhibition rate < 40%), within which efficient metabolism and arsenic adsorption performance can be ensured.

[0085] (3) Optimization of the bacteria-loaded biochar composite

[0086] Preparation of the composite material: Using iron-modified biochar FB-3 as the carrier, the strain was immobilized by the immersion adsorption method to prepare the composite material. The specific preparation method is as follows: Weigh iron-modified biochar FB-3 into a conical flask, sterilize it at 121°C under high-pressure steam for 20 min, and cool it to room temperature. Under sterile conditions, inoculate the above-mentioned bacterial suspension according to the ratio of iron-modified biochar FB-3: bacterial suspension (W:V) of 1:20, shake it at 30°C and 150 r / min for 4 h to complete adsorption and immobilization. After centrifugation, wash the precipitate part with 1% sterile saline three times repeatedly. The obtained precipitate is the loaded material, and the material with strain W7 loaded on iron-modified biochar FB-3 is denoted as W7FB.

[0087] Optimization of the strain inoculation amount: Weigh modified biochar FB-3 into a conical flask, sterilize it at 121°C for 20 min, and inoculate the bacterial suspension according to the ratios of modified biochar FB-3: bacterial suspension (W:V) of 1:5, 1:10, 1:20, and 1:30. Shake and culture it at 30°C and 150 r / min for 24 h, and obtain the loaded materials under different strain inoculation amounts after centrifugation and washing. Weigh 0.5 g of each of the above materials and place them in a 100 mL conical flask. Under sterile conditions, add 50 mL of 50 mg·L -1 of sterilized As solution, shake and culture it at 30°C and 150 r / min on a constant-temperature shaker for 12 h, centrifuge it at 5000 r / min for 5 min, take the supernatant, filter it through a 0.45 μm filter membrane, measure its As concentration, and calculate the adsorption amount to determine the optimal strain inoculation amount of the loaded material.

[0088] Optimization of the immobilization time: Weigh iron-modified biochar FB-3 into a conical flask, sterilize it at 121°C for 20 min, inoculate the bacterial suspension according to the ratio of iron-modified biochar FB-3: bacterial suspension (W:V) of 1:10, shake and culture it at 30°C and 150 r / min, and end the culture at 0, 1, 2, 3, 4, 8, and 12 h respectively. Obtain the loaded materials under different immobilization times after centrifugation and washing. Repeat the adsorption experiment above, measure the As concentration, and determine the optimal immobilization time of the composite material.

[0089] The prepared W7-loaded iron-modified biochar FB-3 composite material was freeze-dried for later use. The specific process is as follows: The resuspended solution of the cultured strain W7 was mixed with iron-modified biochar FB-3 in proportion and shaken in a constant-temperature shaking incubator at 37 °C and 150 r / min. According to the optimal immobilization time, after immobilization, it was placed in an -80 °C refrigerator for 1 h to freeze into solid ice, and then placed in a vacuum freeze-dryer and freeze-dried at -50 °C for 24 h. The obtained powder is the W7-loaded iron-modified biochar FB-3 material.

[0090] During the research process, the inventors found that among various methods of strain loading on biochar, the freeze-drying method has become the preferred option due to its unique comprehensive advantages. Compared with physical adsorption (low loading capacity and easy detachment), co-culture (long cycle), chemical cross-linking (damaging the activity of bacteria), and embedding method (mass transfer limitation), freeze-drying fixes the bacteria through low-temperature dehydration, and is outstanding in maintaining a high survival rate of the strain (80%-90%), ensuring the uniformity of loading (uniform distribution of bacteria in pores), and extending the stability of the material (stored at room temperature for 6-12 months). Its limitations in long-term repair scenarios are significant: for example, the bacteria adsorbed physically are easily washed off by the environment, chemical cross-linking may introduce secondary pollution, and it is difficult to control the loading density in co-culture. The freeze-dried bacteria-biochar composite material can not only be compatible with multifunctional additives (such as iron oxides), but also rapidly activate the metabolic activity of the strain through rehydration, and is suitable for groundwater remediation with large temperature differences and high storage requirements or the production of industrial prefabricated remediation agents. Therefore, its technical advantages of high activity retention and stability make it the preferred loading method for efficient arsenic pollution treatment.

[0091] The effects of the inoculation ratio and immobilization time of W7FB on arsenic adsorption performance were tested, and the results are as Figure 5 shown, where A is the inoculation ratio and B is the immobilization time.

[0092] The present invention relates to a method for optimizing the adsorption performance and regulating the inoculation ratio of the strain W7 and the biochar composite material (W7FB). By comparing the arsenic adsorption performance results of different inoculation ratios of biochar and bacterial suspension (1:5 to 1:30, W:V) as shown in Figure 5 A therein, it was found that the adsorption efficiency showed a significant threshold effect. Specifically: at a low inoculation ratio (1:5), the lack of bacterial suspension led to incomplete coverage of the active sites on the biochar surface, and the arsenic removal rate only reached 63%; as the ratio increased to 1:10, the synergistic effect between the bacteria and the biochar was enhanced, and the removal rate increased to the peak value of 75%. At this time, the iron oxide and the extracellular polymeric substances (EPS) secreted by the bacteria formed a composite adsorption interface, strengthening the chemical complexation and biological reduction of arsenic; however, at high inoculation ratios (1:20, 1:30), the excessive bacterial suspension did not increase the arsenic removal rate.

[0093] The present invention relates to an optimization method for the dynamic adsorption process of the strain W7 and biochar composite material. The influence of regulating the immobilization time of the bacterial suspension and biochar (1 - 18 hours, inoculation ratio 1:10 W:V) on the arsenic removal rate is as Figure 5 shown in B of

[0094] . The research found that the arsenic removal rate exhibits a two-stage characteristic of "rapid response - stable maintenance": in the initial immobilization stage (1 - 4 hours), the bacteria rapidly attach to the biochar surface and activate their metabolic activity, and the arsenic removal rate increases from 60.8% to 66.1% (peak value), indicating that iron oxides and extracellular polymeric substances (EPS) secreted by the bacteria synergistically form an efficient adsorption interface; in the stable maintenance period (4 - 12 hours), the removal rate is maintained at 64.6% - 65.7%, and the fluctuation range is less than 2%, proving that the composite material still maintains stable adsorption performance during long-term action. The mechanism may be attributed to the protective effect of the hierarchical pore structure of biochar (BET specific surface area 11.96 m² / g, average pore diameter 21.04 nm) on the active sites of the bacteria; the experiment shows that 4 hours is the optimal adsorption equilibrium time, at which the arsenic removal rate reaches 66.1%, and the material has both high efficiency and stability (efficiency > 64% within 12 hours). Figure 6 shown, where A, B, and C are the scanning electron micrographs of W7FB at scales of 10 μm, 5 μm, and 2 μm. From Figure 6 it can be seen that the strain W7 is successfully loaded on the iron-modified biochar FB-3.

[0095] (4) Adsorption kinetics study and adsorption isotherm study of the iron-modified biochar material W7FB loaded with bacteria W7

[0096] Weigh 0.1 g of the iron-modified biochar material W7FB loaded with bacteria W7 into a 100 mL conical flask, add 50 mL of 100 mg / L As 5+ solution, and shake and culture it in a constant temperature shaking water bath at 25°C and 150 r / min. Samples are taken at 0, 10, 30, 60, 120, 180, 240, 300, 360, 480, 600, and 720 min respectively. After standing, the upper layer solution is filtered through a 0.45 μm filter membrane, and then the adsorption amount is measured and calculated using ICP-MS. Three parallel samples are set for each sample.

[0097] The experimental results are fitted with the pseudo-first-order kinetic model and the pseudo-second-order kinetic model. Among them, the pseudo-first-order kinetic model is shown in Equation (1):

[0098]

[0099] In the formula: q e is the adsorption amount at equilibrium (mg / g), qt is the adsorption capacity at time t (mg / g), and k1 is the adsorption rate constant of the pseudo-first-order kinetic model.

[0100] The pseudo-second-order kinetic model is shown in Equation (2):

[0101]

[0102] where: q e is the adsorption capacity at equilibrium (mg / g), q t is the adsorption capacity at time t (mg / g), and k2 is the adsorption rate constant of the pseudo-second-order kinetic model.

[0103] Isothermal adsorption model: Weigh 0.1 g of the iron-modified biochar material W7FB loaded with bacteria W7 into a 100 mL conical flask, add 50 mL of As 5+ solution, and set the initial concentrations of As 5+ to be 0, 5, 10, 20, 40, 60, 80, 100 mg / L respectively. Shake and culture in a constant-temperature shaking water bath at 25 °C and 150 r / min. After reaching adsorption equilibrium (set to 720 min in this study), let it stand, filter the upper-layer solution through a 0.45 μm filter membrane, and then use ICP-MS to measure and calculate its adsorption capacity. Set 3 parallel samples for each sample.

[0104] The experimental results were fitted with the Langmuir and Freundlich models. The Langmuir adsorption isotherm model is shown in Equation (3):

[0105]

[0106] where: q e is the adsorption capacity at equilibrium (mg / g); q m is the adsorption capacity at saturation (mg / g); C e is the equilibrium concentration (mg / L); K L is the Langmuir adsorption constant (L / mg).

[0107] The Freundlich adsorption isotherm model is shown in Equation (4):

[0108]

[0109] where: q e is the equilibrium adsorption capacity (mg / g); K F is the Freundlich adsorption constant (L / mg); C e is the equilibrium concentration (mg / L); n is the Freundlich adsorption characteristic coefficient.

[0110] The arsenic adsorption effect of W7FB at different times is as follows Figure 7 As shown, the arsenic removal rate of W7FB shows two-stage characteristics of "rapid adsorption - dynamic equilibrium" with time: the rapid adsorption period and the equilibrium and stable period. Rapid adsorption period (0 - 2 hours): The arsenic removal rate rapidly increases from 33.6% to 63.8% (an increase of 90%), indicating that the abundant active sites of iron oxides and pore structures on the material surface dominate the physical adsorption and chemical complexation of arsenic in the initial stage; the removal rate reaches 51.7% within 0.5 hours, highlighting its high-efficiency adsorption kinetic characteristics. Equilibrium and stable period (2 - 12 hours): The removal rate fluctuates between 63.8% - 66.4%, reaching a peak of 66.2% at 4 hours, and then fluctuating slightly (e.g., dropping to 65.8% at 8 hours and recovering to 66% at 12 hours), reflecting the adsorption - desorption dynamic equilibrium; the metabolic activities of strain W7 (such as arsenic speciation transformation) may supplement adsorption sites at this stage to maintain the stability of the removal rate. W7FB can achieve an arsenic removal rate of over 60% within 2 hours and is close to adsorption saturation (66.2%) at 4 hours. Its rapid response and continuous stability characteristics stem from the dual mechanism of "adsorption - biotransformation" of bacteria - carbon synergy, which is suitable for emergency repair scenarios that require rapid reduction of arsenic pollution.

[0111] The fitting results of the arsenic adsorption process of W7FB by the pseudo-first-order and pseudo-second-order kinetic models are as follows Figure 8 and Table 4 show. Among them, Figure 8 A in [Figure] is the pseudo-first-order kinetic model, Figure 8 B in [Figure] is the pseudo-second-order kinetic model, Figure 8 The ordinate of A in [Figure] is the common logarithm of the difference in adsorption capacity, and the corresponding mathematical formula is lg(qe - qt), which represents the common logarithm of the difference between the adsorption capacity at adsorption equilibrium (qe) and the adsorption capacity at adsorption time t (qt). It reflects that during the adsorption process, as time goes by, the gap between the adsorption capacity of the adsorbent for the adsorbate and the equilibrium adsorption capacity. Figure 8 The ordinate of B in [Figure] is the ratio of time to adsorption capacity, and the corresponding mathematical formula is t / qt, which represents the ratio of time t to the adsorption capacity qt at time t when the adsorption proceeds to time t. It reflects that during the adsorption process, the time required per unit adsorption capacity.

[0112] Table 4 Fitting results of the arsenic adsorption process of W7FB by the pseudo-first-order and pseudo-second-order kinetic models

[0113]

[0114] k1 in Table 4 is the pseudo-first-order kinetic rate constant, k2 is the pseudo-second-order kinetic rate constant, and R 2 is the coefficient of determination.

[0115] Through Figure 8Fitting the arsenic adsorption process of W7FB with the pseudo-first-order and pseudo-second-order kinetic models in Table 4 revealed that the adsorption behavior was more in line with the pseudo-second-order kinetic model (R² = 0.999), indicating that the adsorption process was dominated by chemisorption mechanisms (such as surface complexation, ion exchange, or chemical bond formation), rather than simple physical diffusion. Specifically: the low fitting degree of the pseudo-first-order kinetics (R² = 0.605) indicated that the adsorption rate was not solely driven by the concentration gradient of arsenic in the solution; the high correlation of the pseudo-second-order kinetics (R² ≈ 1) suggested that the adsorption was limited by the chemical reactions at the active sites, and the rate constant k2 = 0.013 g / (mg·h) further verified the typical characteristics of chemisorption; Inferred adsorption mechanism: The iron oxides on the surface of iron-modified biochar bind to arsenate through coordination bonds, and the metabolites of strain W7 may synergistically enhance the stability of chemisorption sites. The arsenic adsorption process of W7FB was mainly chemisorption, and its high efficiency stemmed from the strengthening of active sites under the synergistic action of bacteria and biochar, which had significant advantages in the remediation of high-arsenic polluted water bodies.

[0116] The fitting results of the isothermal adsorption model are as Figure 9 shown in Table 5.

[0117] Table 5 Fitting results of the isothermal adsorption model

[0118]

[0119] Q in Table 5 max is the maximum adsorption capacity, that is, the maximum adsorption amount when the surface of the adsorbent is completely covered with a monolayer (in mg / g), which reflects the theoretical limit adsorption capacity of the adsorbent and is related to the number of active sites of the adsorbent. The Q of W7FB max = 118.584 mg / g represents the maximum capacity of this adsorbent under ideal monolayer adsorption. K L is the Langmuir adsorption constant, which reflects the binding strength between the adsorbent and the adsorbate (in L / mg); the larger this value, the stronger the binding between the adsorbate and the adsorbent, that is, the easier the adsorption occurs, and the smaller this value, the weaker the binding between the adsorbate and the adsorbent. 1 / n is the heterogeneity factor, which represents the heterogeneity of the adsorbent surface and the distribution of adsorption affinity (dimensionless). Among them, 1 / n < 1 indicates that the adsorption surface is uneven and the adsorption process is easy to proceed (preferential adsorption of high-affinity sites); 1 / n > 1 indicates that the adsorption surface is uniform and the adsorption difficulty increases with the increase in coverage; 1 / n = 1 indicates a degradation to linear adsorption (similar to Henry's law). K F represents the Freundlich adsorption constant, which reflects the relative adsorption capacity of the adsorbent (in (mg / g)·(L / mg)), and the larger its value, the stronger the adsorption capacity of the adsorbent for the adsorbate. R² is the coefficient of determination, which represents the goodness of fit of the model to the experimental data. The closer it is to 1, the more reliable the model.

[0120] As can be seen from Figure 9 the fitting results such as max Table 5, the arsenic adsorption of W7FB is mainly monolayer chemisorption (Langmuir model). At the same time, due to surface heterogeneity (Freundlich model), it shows a wide concentration adaptation range. Its ultra-high adsorption capacity (Q L is about 118.6 mg / g) and the synergistic characteristics of controllable binding strength (K

[0121] (5) Remediation effects of different dosages on water bodies at different temperatures

[0122] To study the arsenic adsorption ability of the W7-loaded iron-modified biochar material on the aquatic environment at different temperatures and different dosages, an arsenic-polluted aquatic environment was simulated, and a solution with an arsenic concentration of 50 mg / L was prepared. 1 g / L, 2 g / L, 3 g / L, and 5 g / L of W7 bacterial powder, iron-modified biochar, and W7-loaded iron-modified biochar materials were added respectively, and they were oscillated and cultured at 150 r / min on a constant temperature oscillator at 10 °C, 20 °C, and 30 °C for 24 h, centrifuged at 5000 r / min for 5 min, and the supernatant was filtered through a 0.45 μm filter membrane. The As concentration was measured and the adsorption capacity was calculated. The results are as Figure 10 shown, where W7 is strain W7, FB-3 is iron-modified biochar, and W7FB is the composite material of W7-loaded biochar FB-3; the letters marked on the graph (such as a, b, c) represent the results of multiple comparison tests, which are used to visually display the significant differences between different groups.

[0123] As Figure 10 can be seen, at 10 °C, 20 °C, and 30 °C, the arsenic removal rates of strain W7 (W7), iron-modified biochar (FB), and their composite material (W7FB) show significant temperature dependence, synergistic enhancement, and dosage optimization characteristics: the increase in temperature enhances the removal efficiency: W7FB still performs excellently at low temperature (60.8% removal rate at 10 °C and 3 g / L dosage), but as the temperature rises to 20 °C and 30 °C, the efficiency further increases to 65.8% and 66.8%, indicating that the strain activity and adsorption kinetics are positively regulated by temperature; single-component response differences: W7 bacterial powder: when the temperature ranges from 10 °C to 30 °C, the removal rate increases from 21.4% to 30.8% at a dosage of 3 g / L, with an increase of 44.0%, reflecting the significant promotion of temperature on bacterial metabolism; FB: when the temperature ranges from 10 °C to 30 °C, the removal rate increases from 54.2% to 60.2% at a dosage of 3 g / L, with an increase of 11.1%, mainly relying on physical adsorption and being less affected by temperature.

[0124] Synergistic effect stability: The synergistic advantage of W7FB is maintained within a wide temperature range: at 10 °C, with a dosage of 3 g / L, W7FB is 12.2% and 184.1% higher than FB / W7 respectively; at 30 °C, the improvement is 10.9% (vs FB) and 117.0% (vs W7), indicating that the bacteria-biochar synergy is still the dominant mechanism at high temperatures. Synergistic mechanism: Biochar provides a heat-preserving microenvironment for the strain at low temperatures, and enhances the exposure of active sites of the bacteria through pore structure at high temperatures, forming a dynamic adaptation.

[0125] Dosage optimization and saturation effect: Optimal dosage: 3 g / L is the efficiency inflection point at each temperature (e.g., at 30 °C, the removal rate of 3 g / L W7FB is 66.8%, and it only slightly decreases to 66.7% at 5 g / L), and it is recommended to use 3 g / L as the economic dosage threshold; Dosage-temperature interaction: Higher dosage is required at low temperature (10 °C) to compensate for the loss of activity (reaching 60.8% at 3 g / L); At high temperature (30 °C), a low dosage (2 g / L) can achieve a removal rate of 57.1%, which is suitable for scenarios with limited resources. Conclusion: W7FB shows high arsenic removal ability in the range of 10 - 30 °C, its synergistic effect is not limited by temperature, and 3 g / L is the universal optimal dosage. This material has both low-temperature adaptability and high-temperature activity enhancement characteristics, and is suitable for the treatment of arsenic pollution in scenarios with significant seasonal temperature differences or industrial wastewater temperature fluctuations.

[0126] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An arsenic wastewater treatment agent, characterized in that: It comprises a carrier and a bacterial suspension adsorbed and fixed on the carrier; The carrier is iron-modified biochar; the iron in the iron-modified biochar exists in the form of iron oxides, and the iron oxides are Fe3O4, FeO(OH), γ-Fe2O3 and α-Fe2O3; The strain in the bacterial suspension is Bacillus subtilis (Bacillus subtilis) W7; The mass ratio of carbon to iron in the iron-modified biochar is 1: (0.025-1.5); The iron-modified biochar has a pH of 8-9, a conductivity of 1800-1900 μs / cm, an ash content of 25-30 wt%, and a specific surface area of ​​10-12 m 2 / g, with a total pore volume of 0.05-0.07cm 3 / g, the average pore size is 20-22nm, the adsorption pore diameter is 22-24 nm, and the desorption pore diameter is 17-19 nm; The OD600 of the bacterial suspension is 0.9-1.1; the ratio of the carrier to the bacterial suspension is 1 g: (5-30) mL; The preparation method of the arsenic wastewater treatment agent comprises the following steps: Under sterile conditions, the iron-modified biochar is mixed with the bacterial suspension and then freeze-dried to obtain the biochar.

2. A method for preparing the arsenic wastewater treatment agent according to claim 1, characterized in that: The following steps are involved: Under sterile conditions, the iron-modified biochar is mixed with the bacterial suspension and then freeze-dried to obtain the biochar.

3. The method for preparing an arsenic wastewater treatment agent according to claim 1, characterized in that: The method for preparing the iron-modified biochar comprises the following steps: (1) The straw powder is heated to 350-450°C under anaerobic conditions, kept warm for 1-3 hours, cooled to room temperature, and sieved to obtain biochar; (2) Add water to the mixture of biochar and iron source for reaction, dry it, heat it to 350-450°C under anaerobic conditions, keep it warm for 0.5-1h, cool it to room temperature, and seal it to obtain iron-modified biochar.

4. The method for preparing an arsenic wastewater treatment agent according to claim 3, characterized in that: In step (1), the particle size of the straw powder is less than 1 mm, and the particle size of the biochar is 0.053-1 mm; In step (2), the iron source is one of ferric nitrate nonahydrate, ferrous chloride, ferric chloride and ferric sulfate; The mixing mass ratio of the biochar to the iron in the iron source is 1: (0.025-1.5); The solid-to-liquid ratio of the mixture to water is 1 g: (25-35) mL; The reaction is carried out at a constant temperature of 25-30°C and a shaking reaction at 150-200 r / min for 10-15 hours; The drying temperature is 50-60°C.

5. The method for preparing an arsenic wastewater treatment agent according to claim 2, characterized in that: The preparation method of bacterial suspension comprises the following steps: Bacillus subtilis ( Bacillus subtilis ) W7 is inoculated into a sterilized LB liquid medium and cultured in the dark to obtain a seed solution, the seed solution is mixed with the sterilized medium, and the culture is continued in the dark to obtain a bacterial suspension; The sterilization temperature is 121°C for 0.5-1h; the light-proof culture is a constant temperature culture of 25-30°C with shaking at 150-200r / min for 20-25h; The continued dark-proof culture is carried out at a constant temperature of 25-30° C. and a shaking culture at 150-200 r / min for 1-2 days; The volume ratio of the seed solution to the sterilized culture medium is 1:(20-30); The OD600 in the seed solution is 0.6-1; The OD600 of the bacterial suspension is 0.9-1.

1.

6. The method for preparing an arsenic wastewater treatment agent according to claim 2, characterized in that: The ratio of the iron-modified biochar to the bacterial suspension is 1 g: (5-30) mL; The mixing is carried out at a constant temperature of 30-40°C and at a shaking speed of 150-200 r / min for 1-12 hours; The freeze-drying temperature is first freezing at -75~ -85°C for 0.5-2h, and then freezing at -45~ -55°C under vacuum for 20-30h.

7. Use of the arsenic wastewater treatment agent according to claim 1 in arsenic-contaminated water.

8. A method for treating arsenic wastewater, characterized in that: Applying the arsenic wastewater treatment agent according to claim 1 to an arsenic-contaminated water body; The arsenic content in the water body is 60-100 mg / L, and the temperature of the water body is 10-30°C; The application amount of the arsenic wastewater treatment agent is 1-5 g / L, and the application time is 20-30 hours.

Images