CN114713181B - Biosynthesis method of exogenous seed crystal-added mediated Schwerner mineral, product and application thereof - Google Patents

Abstract

The invention discloses a biosynthesis method of an exogenous seed crystal-added mediated Schwerk mineral, and a product and application thereof. Adding a beta-FeOOH nano seed crystal solution into a ferrous sulfate solution, and then adding an A.ferrooxidans resting cell suspension to obtain a mixed solution; culturing the mixed solution at 25-30 ℃ for 42-72h; and after the culture is finished, washing, freeze-drying and sieving the mineral precipitate to obtain the Schneider mineral which is mediated and synthesized by adding the exogenous seed crystal. The invention has higher yield of the Schneider prepared by adding the exogenous seed crystal and shorter synthesis period. The treatment effect on As (V) and Cr (VI) in the water body is better than that without the use of seed crystal. In addition, the invention has the advantages of simple preparation, rapidness, high efficiency, low cost and no secondary pollution to the environment, and can be applied to the treatment of acid mine wastewater.

Description

Biosynthesis method of exogenous seed crystal-added mediated Schwerner mineral, product and application thereof

Technical Field

The invention belongs to the technical field of water treatment adsorption materials, and particularly relates to a biosynthesis method of an exogenous seed crystal mediated Schwerer mineral, a product and application thereof.

Background

Heavy metal pollution widely exists in the industries of mining, machining, metal smelting, surface treatment and the like. Large amounts of waste water are produced in industrial processes and are discharged into surface and ground waters without appropriate treatment. Heavy metal pollution can produce long-term toxicity to the environment and human health through a variety of means. At present, the main technologies for treating the heavy metal polluted wastewater comprise coagulation-flocculation, membrane treatment, chemical precipitation, ion exchange, adsorption and the like. However, limitations such as inefficient processing, high cost, and lack of selectivity make these processes impractical. The adsorption has attracted more and more attention by the characteristics of simplicity, convenience, high removal efficiency and the like. Among the adsorbents widely used, metal oxides such as nano iron oxide, aluminum oxide and manganese oxide are considered as ideal adsorbents for removing heavy metals. Iron-based adsorption materials have become the most widely used adsorbents due to their huge reserves, simple synthesis and environmental friendliness, and low-cost iron-based materials have attracted increasing attention worldwide. Schlemm's mineral (Fe) ₈ O ₈ (OH) _8-2x (SO ₄ ) _x ·nH ₂ O is an ochre hydroxyl iron sulfate secondary mineral formed in acidic and sulfate-rich water, has the characteristics of high specific surface area, surface reactivity, tunnel structure, no biotoxicity, environmental friendliness and the like, and has an important influence on migration and passivation of heavy (class) metals in the environment. And thus are of great interest to geologists and geochemists.

The Schneider minerals are usually only present in extremely acidic Fe-rich and SO-rich minerals ₄ ^2- In the mine drainage environment, the environmental condition window of the ore formation is narrow and the yield is low. At present, the methods of artificial synthesis mainly include hydrogen peroxide oxidation (chemical fast method), dialysis (chemical slow method) and microbiological method. For example, chinese invention patent CN110713224B (CN 201910958408.2) discloses a method for preparing schwers mineral by dialysis, which comprises the steps of firstly, preserving heat of a synthetic system at 50-70 ℃, and then dialyzing at normal temperature for 7 days to obtain sea urchin-shaped schwers mineral with burr structure, which is formed in the natural environment; but H ₂ O ₂ The spherical Schleman mineral with the particle size of 400-500 nm can be obtained only by 1d of rapid oxidation (Loan et al, 2005); and the thiobacillus ferrooxidans oxidizes FeSO ₄ After about 3 days, the sea urchin-shaped schwann mineral with the particle size of about 2 mu m can be obtained. The existing synthetic method mainly has the following problems: the synthesis period of the dialysis method is too long,large amounts of deionized water are required, which is impractical for engineering applications; albeit H ₂ O ₂ The rapid oxidation method is high in speed, but the obtained mineral has no observed typical sea urchin-shaped burr structure, and the adsorption and removal capacity on pollutants is obviously weaker than that of the burr-shaped Schlemm mineral. The microbial oxidation method can obtain Schneider minerals with micro-morphology (sea urchin shape) close to that of the ore formation in the natural environment, but the microbial ore synthesis period is longer, the agglomeration of mineral particles is serious, the specific surface area is small, and the maximum removal of pollutants is limited. In addition, li Zhejiang et al (Prov. Environmenta science, 2011,31 (3): 460-467; prov. Environmenta science, 2011,31 (5): 912-918) also found that the microbially synthesized Schneider minerals had higher adsorption capacity for pollutants due to the microstructure of their burrs and that the biomineralization rate was higher than the chemical oxidation iron precipitation rate. Therefore, microbial mineralization has recently received increasing attention as an effective, sustainable, low-cost method for the synthesis of iron-based materials. However, schwann minerals synthesized by microbial methods are generally present in the form of micron-sized spherical aggregates, and due to a large spherical structure, an internal reaction zone is protected to reduce the specific surface area thereof, so that the adsorption capacity thereof cannot be maximized. Researchers have therefore been working on engineering biosynthetic schwann minerals to increase adsorption activity and adsorption capacity. The measures taken are mainly focused on controlling environmental factors such as pH, temperature, formation time and culture medium. However, these measures are not effective in regulating the structure of schneider minerals. Meanwhile, the adsorbent is greatly influenced by pH when treating (similar) metals in the wastewater, and the adsorption effect is poorer than that of a neutral environment under an acidic condition, and the same is true for Schneider minerals. The present invention thus seeks to improve the performance of biosynthesized schlerian minerals by a gentle and non-mortal process by seeding (providing more surface sites for schlerian mineral formation).

Generally, seeds need to provide sufficient surface (i.e., growth sites) for growth, and therefore smaller crystal particles are often used as seeds, while very small amounts of large crystals tend to be more difficult to achieve with significant results during crystallization. Depending on the conditions of the schlerian mineral synthesis, the desired seed crystals also need to be stable under acidic conditions, in a specific ratioLarge surface area, uniform and proper particle size, high cost performance, fixed internal structure, structure and composition similar to those of Schneider mineral, and high compatibility with Fe (III) and SO ₄ ^2- Has certain adsorption capacity. Therefore, we first consider iron oxides commonly found in the natural environment, mainly including iron oxides and iron oxyhydroxides (also known as iron oxyhydroxides, feOOH). The FeOOH has the advantages of large specific surface area, stable physicochemical properties, special structural characteristics and the like, and plays an important role in purifying pollutants in the environment. The FeOOH currently of interest is mainly goethite (α -FeOOH), tetralepidocrocite (β -FeOOH), lepidocrocite (γ -FeOOH). Among these, picrochorite (. Beta. -FeOOH) is a nanoparticle formed in a chloride ion-and iron-rich environment, the presence of which has also been found in chlorine-rich zones and acidic mine wastewaters. The beta-FeOOH has a tunnel structure junction similar to that of the Schneider mineral, and the structure comprises double-chain octahedrons sharing edges, and the common-edge octahedrons share an angle with adjacent chains to form a channel parallel to a c axis. The beta-FeOOH is a nano particle, and has the advantages of no toxicity, low cost, good stability under an acidic condition and the like. Therefore, under the induction of specific functional groups (a large number of hydroxyl groups) of beta-FeOOH, inorganic substances may migrate, enrich, transform and form secondary minerals. The nature of the formed schneider mineral will vary with the amount of beta-FeOOH additive. On the basis, the system of the invention researches the feasibility of the beta-FeOOH as the seed crystal for mediating the biosynthesis of the nano-scale schlerian mineral. Our aim is to modulate the morphology, structure and surface properties of schwertmannite, increase the number of functional groups and improve its reactivity towards heavy metals in biosynthetic systems. The invention makes a contribution to the high-performance adsorbent for biosynthesis and has important significance for deepening the understanding of the biosynthesis of the Schneider minerals.

Disclosure of Invention

Aiming at the problems of low yield and long period of biosynthesized schlerian minerals in the prior art, the invention aims to provide a synthetic method of high-yield schlerian minerals; and the period of biosynthesis of Schlemm's mineral can be shortened. The invention also aims to enhance the performance of removing pentavalent arsenic and hexavalent chromium in the acid wastewater by using the Schwerer minerals. The schlempe mineral prepared by the method has high yield, short synthesis period, low cost and good treatment effect on As (V) and Cr (VI) pollution in water, and can be applied to treatment of industrial wastewater such As mining and the like.

The purpose of the invention is realized by the following technical scheme:

a biosynthesis method for mediating Schneider minerals by adding exogenous seed crystals comprises the following steps:

(1) Adding a beta-FeOOH nano seed crystal solution into a ferrous sulfate solution, and then adding an A.ferrooxidans resting cell suspension to obtain a mixed solution;

(2) Culturing the mixed solution obtained in the step (1) at 25-30 ℃ for 42-72h, and after the culture is finished; and washing, freeze-drying and sieving the mineral precipitate to obtain the Schneider mineral which is mediated and synthesized by adding the exogenous seed crystal.

Preferably, the density of A.ferrooxidans in the suspension of resting cells of A.ferrooxidans in step (1) is 1X 10 ⁸ ～3×10 ⁸ cells/ml; more preferably, the density is 1X 10 ⁸ cells/ml。

Preferably, the concentration of the beta-FeOOH nano seed crystal solution in the step (1) is 0.001-0.1 g/mL. A more preferred concentration is 0.01g/mL.

Preferably, the concentration of the ferrous sulfate in the mixed solution in the step (1) is 20-160 mMol/L; more preferably at a concentration of 80mMol/L;

preferably, the volume ratio of the beta-FeOOH nano seed crystal solution to the mixed solution in the step (1) is 2-128: 1000 parts by weight; more preferred volume ratios are (2, 4, 8, 16, 32, 64, 128): 1000;

preferably, the volume ratio of the suspension of resting cells of ferrooxidans to the mixed solution in step (1) is 1. More preferably, the volume ratio is 1.

Preferably, the culture in the step (2) is carried out in a shaking table with the speed of 150-200 r/min;

preferably, the washing in the step (2) is deionized water washing; the temperature of the freeze drying is-30 to-45 ℃, and the time is 12 to 36 hours; the sieving is to sieve through 100-200 meshes.

Preferably, the preparation method of the beta-FeOOH nano seed crystal solution in the step (1) comprises the following steps: dissolving ferric chloride in absolute ethyl alcohol, adding deionized water, mixing and stirring uniformly to obtain a reaction solution, and reacting at the temperature of 80-100 ℃ for 36-54 h; after the reaction is finished, centrifuging, washing, freezing and drying to obtain beta-FeOOH nano seed crystal; adding water into the obtained beta-FeOOH nano seed crystal, and performing ultrasonic dispersion to obtain a beta-FeOOH nano seed crystal solution.

More preferably, the ferric chloride is FeCl ₃ ·6H ₂ O; the concentration of ferric chloride in the reaction liquid is 0.2-0.4 Mol/L; the volume ratio of the absolute ethyl alcohol to the deionized water is 1:1-1.5;

more preferably, the washing is absolute ethyl alcohol and deionized water washing to be neutral; the freeze drying time is 12-36 h;

more preferably, the time for the ultrasonic dispersion is 30 to 45 minutes.

Preferably, the method for preparing the suspension of a. Ferrooxidans resting cells comprises the following steps:

sterilizing a 9K culture medium at high temperature and high pressure, inoculating A.ferrooxidans bacteria, adding ferrous sulfate, adjusting the pH, and culturing for 2-3 days; filtering to remove iron precipitate, centrifuging the filtrate, collecting thalli, washing and suspending to obtain A.ferrooxidans resting cell suspension.

More preferably, the centrifugal temperature is 4-7 ℃, the centrifugal force is 10000-12000 g, and the time is 8-10 minutes;

more preferably, the volume after suspension is 1/50 to 1/100 of the culture medium.

More preferably, the pH is adjusted to H ₂ SO ₄ Adjusting pH to 2-3.

The Schwerner mineral which is obtained by the biosynthesis method and is mediated and synthesized by adding exogenous seed crystals.

The application of the Schwerner mineral which is added with the exogenous seed crystal and mediated for synthesis in removing As (V) and Cr (VI) pollution in water body.

Compared with the prior art, the invention has the following advantages:

(1) The 'seed crystal method' of the invention can directly provide crystal nuclei and provide crystal growth sites for the growth of the Schneider minerals, thereby greatly shortening the induction period and the nucleation period. Therefore, the invention can shorten the period of microbe mineralization (from 66h to 42 h). The hydrolysis and the ore formation of the ferric iron of the comparative example without the seed crystal are finished in 66 hours, while the precipitation of the seed crystal is finished in 42 hours, so that the microbial ore formation period is shortened.

(2) The synthesized Schneider mineral has high yield which is obviously higher than that of the synthesized Schneider mineral without adding crystal seeds. The total yield of the synthesized mineral is 8.0-96.7% higher than that of a comparative example without adding the seed crystal.

(3) The Schneider minerals prepared by the method have better removal effect on As (V) and Cr (VI) in the water body, and an effective way is provided for treating the polluted wastewater rich in As (V) and Cr (VI).

(4) The invention takes the ferric salt as the raw material, the raw material is simple and easy to obtain, and the microorganism mineralization is an effective, sustainable and low-cost synthesis method, the process flow is simple, the operation is convenient and fast, and the production cost is low.

Drawings

FIG. 1 is a characteristic X-ray diffraction pattern (XRD) of the Schneider mineral and the beta-FeOOH nanoparticles prepared in examples 1-7 of the present invention and comparative example.

FIG. 2 is a Scanning Electron Microscope (SEM) image of Schneider minerals and beta-FeOOH nanoparticles prepared in examples 1-7 of the present invention and comparative example.

FIG. 3 is an infrared spectrum (FTIR) of the Schneider mineral and β -FeOOH nanoparticles prepared in examples 1-7 of the present invention and comparative example.

FIG. 4 is a graph of the ferrous iron oxidation rates of the Schneider minerals prepared in examples 1-7 of the present invention and comparative examples.

FIG. 5 is a trivalent iron mineralization map of the Schneider minerals prepared in examples 1-7 of the present invention and comparative examples.

FIG. 6 is a bar graph of the total and net production of Schneider minerals prepared in examples 1-7 of the present invention and comparative examples.

FIG. 7 is a graph showing the removal of As (V) at different As (V) concentrations (a. Removal rate; b. Adsorption capacity) of the Schneider minerals and β -FeOOH nanoparticles prepared in examples 1 to 7 of the present invention and comparative example.

FIG. 8 is a graph of Cr (VI) removal curves (a. Removal rate; b. Adsorption capacity) for the Schneider minerals and β -FeOOH nanoparticles prepared in examples 1-7 of the present invention and comparative examples at different Cr (VI) concentrations.

FIG. 9 is a graph showing the removal of As (V) from the Schneider mineral and β -FeOOH nanoparticles prepared in examples 3 and 6 of the present invention and comparative example at different pH values (a. Removal rate; b. Adsorption capacity).

FIG. 10 is a graph of Cr (VI) removal curves (a. Removal rate; b. Adsorption capacity) for the Schneider mineral and beta-FeOOH nanoparticles prepared in inventive examples 3 and 6 and comparative example at different pH values.

Fig. 11 is a graph showing adsorption kinetics of schwerer minerals prepared in examples 3 and 6 of the present invention and comparative example { a.as (V); cr (VI).

Detailed Description

The following description of the embodiments of the present invention is provided in connection with the accompanying drawings and examples, but the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated by the manufacturer, and are regarded as conventional products commercially available.

A biosynthesis method of adding exogenous seed crystal to mediate Schwerer mineral comprises the following steps:

(1) Preparation of beta-FeOOH nano seed crystal solution:

weighing a certain amount of FeCl ₃ ·6H ₂ And O, adding absolute ethyl alcohol to dissolve, and slowly adding a certain amount of deionized water at a constant speed. After being mixed and stirred evenly, the mixture is moved into a reaction kettle, the reaction temperature is set at 90 ℃, and the reaction is carried out for 45 hours. After the reaction is finished, washing the reaction product by absolute ethyl alcohol and deionized water for several times, centrifuging the reaction product, cleaning the precipitate to be neutral, and freeze-drying the precipitate for 24 hours to obtain the beta-FeOOH nano-particles. The obtained nano seed crystal beta-FeOOH is prepared into 0.01g/mL aqueous solution, and after ultrasonic treatment is carried out for 30 minutes, the beta-FeOOH nano particles are uniformly dispersed in the solution and are used as seed crystals for synthesizing schlieren minerals.

FeCl in the step (1) ₃ ·6H ₂ The concentration of O is 0.2Mol/L, and the ratio of absolute ethyl alcohol to deionized water is 1; the obtained beta-FeOOH has good crystallinityThe particles are uniform and are spindle-shaped nanoparticles with the length of about 60nm and the width of 30 nm.

(2) Preparation of suspensions of ferrooxidans resting cells:

ferrooxidans bacterial strain is obtained by separating and purifying acid mine wastewater of a pyrite mine in Guangdong province of China (preserved by China center for type culture Collection, CCTCC for short, with the preservation number of CCTCC NO: M2013102). The strain was cultured using 9K medium. Sterilizing 9K culture medium at high temperature and high pressure, inoculating A.ferrooxidans into sterilized 9K culture medium, and adding FeSO ₄ ·7H ₂ O to a concentration of about 44.2g/L with 1mol/L H ₂ SO ₄ The pH was adjusted to 2.5. The inoculated culture solution is placed in a shaking table at 30 ℃ for shaking culture at 180r/min, and the culture is stopped after the logarithmic growth phase (about 2 to 3 days). The culture broth was then filtered through qualitative filter paper to remove iron precipitates, and the filtrate was centrifuged at 10000g for 10 minutes at 4 ℃ to collect the cells. H for bacteria ₂ SO ₄ The solution (pH 2.5) was washed 3 times with H ₂ SO ₄ The solution (pH 2.5) was suspended. About 20ml of the bacterial suspension was collected in 1L of the culture medium to obtain a concentrated bacterial suspension (50-fold). Wherein the density of A. Ferrooxidans is about 1X 10 ⁸ cells/ml。

(3) Preparation of schlerian mineral:

FeSO is added into a 1L triangular flask ₄ ·7H ₂ O preparing a Schneider mineral, adding a certain amount of beta-FeOOH nanoparticle solution obtained in the step (1), then adding 5mL of A.ferrooxidans resting cell suspension prepared in the step (2), and adding a proper amount of deionized water to make the total volume be 500mL (Fe) ²⁺ The concentration reaches 80 mMol/L); then the mixed solution is put into a shaking table at 30 ℃ and 180r/min for culturing for 3 days. After the culture is finished, washing with deionized water, freeze-drying at-45 ℃ for 24h, and sieving with a 100-mesh sieve to obtain the seed crystal mediated synthesized schneishi mineral.

The volume of the beta-FeOOH nanoparticle solution added into the system in the step (3) is 0, 1, 2, 4, 8, 16, 32 and 64mL. The synthesized schlerian minerals are respectively marked as comparative examples, example 1, example 2, example 3, example 4, example 5, example 6 and example 7, and the comparative examples serve as blank control groups.

Example 1

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of Schneider mineral, fe ²⁺ The concentration reaches 80mMol/L; and (2) adding 1mL of the beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of the A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and culturing the mixed solution in a shaking table at 30 ℃ and 180r/min for 3 days. After the completion of the culture, the collected mineral was washed with deionized water, centrifuged and dried to obtain 1.63g of mineral.

Example 2

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of schwertmannite, fe ²⁺ The concentration reaches 80mMol/L; and (2) adding 2mL of the beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of the A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and culturing the mixed solution in a shaking table at 30 ℃ and 180r/min for 3 days. After the completion of the culture, the collected mineral was washed with deionized water, centrifuged and dried to obtain 1.68g of mineral.

Example 3

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of schwertmannite, fe ²⁺ The concentration reaches 80mMol/L; and (2) adding 4mL of the beta-FeOOH nano concentrated solution obtained in the step (1), then adding 5mL of the A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and then placing the mixed solution in a shaking table at 30 ℃ and 180r/min for culturing for 3 days. After the completion of the culture, the collected mineral was washed with deionized water, centrifuged and dried to obtain 1.75g of mineral.

Example 4

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of Schneider mineral, fe ²⁺ The concentration reaches 80mMol/L; adding 8mL of beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of A.ferrooxidans resting cell suspension prepared in the step (2), and adding a proper amount of deionized water to ensure that the total system is500mL, and then the above mixture was cultured in a shaker at 30 ℃ and 180r/min for 3 days. After the completion of the culture, the collected mineral was washed with deionized water, centrifuged and dried to obtain 1.81g of mineral.

Example 5

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of schwertmannite, fe ²⁺ The concentration reaches 80mMol/L; and (2) adding 16mL of the beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of the A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and culturing the mixed solution in a shaking table at 30 ℃ and 180r/min for 3 days. After the completion of the culture, the collected minerals were washed with deionized water, centrifuged and dried to obtain 2.01g of minerals.

Example 6

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of schwertmannite, fe ²⁺ The concentration reaches 80mMol/L; and (2) adding 32mL of the beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of the A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and culturing the mixed solution in a shaking table at 30 ℃ and 180r/min for 3 days. After the culture was completed, the collected minerals were washed with deionized water, centrifuged and dried to obtain 2.39g of minerals.

Example 7

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of schwertmannite, fe ²⁺ The concentration reaches 80mMol/L; adding 64mL of beta-FeOOH nano concentrated solution obtained in the step (1), adding 5mL of A.ferrooxidans resting cell suspension prepared in the step (2), adding a proper amount of deionized water to make the total volume be 500mL, and culturing the mixed solution in a shaking table at 30 ℃ and 180r/min for 3 days. After the culture was completed, the collected minerals were washed with deionized water, centrifuged and dried to obtain 2.97g of minerals.

Comparative example

11.12g of FeSO were charged into a 1L Erlenmeyer flask ₄ ·7H ₂ O preparation of Schneider mineral, fe ²⁺ The concentration reaches 80mMol/L; then add into5mL of A. Ferrooxidans resting cell suspension prepared in step (2), adding an appropriate amount of deionized water to make the total volume to be 500mL, and then culturing the above mixture in a shaker at 30 ℃ and 180r/min for 3 days. After completion of the culture, the collected mineral was washed with deionized water, centrifuged, and dried to obtain 1.51g of mineral.

Phase identification

Compared with the prepared mineral XRD pattern (figure 1) and SEM scanning electron microscope pattern (figure 2), the synthesized seed crystal (beta-FeOOH) has obvious characteristic peak, good crystal form and high purity, and is a spindle-shaped particle with the length of 60nm and the width of 30 nm. From FIG. 1, it can be seen that the characteristic peaks of the Schneider minerals prepared by the present invention are the same as the characteristic peaks of the minerals reported, the Schneider minerals are determined, and the specific surface area (BET) ratio of the examples is larger than that of the comparative example. As can be seen from fig. 1 and 2: the Schneider mineral prepared by adding the seed crystal (beta-FeOOH) is more dispersed, has more burrs on the surface and has larger specific surface area than the particles of a comparative example (the Schneider mineral synthesized without using the seed crystal), and the invention shows that the adsorption sites of the Schneider mineral can be increased through the induction of the seed crystal, so that the adsorption quantity of the Schneider mineral on heavy metals can be increased.

The infrared spectrograms (FTIR) of the examples and comparative examples are shown in fig. 3. 1647cm can be seen from FIG. 3 ^-1 1078, 950 and 688cm of water molecules ^-1 Should be classified as Schneider mineral SO ₄ ^2- V3, v1, v4 diffraction peaks of (a). The infrared spectrum analysis result further proves that the mineral prepared by the invention is a Schneider mineral. The difference is a diffraction peak on an infrared spectrogram of-OH, and the diffraction peak position of-OH of a comparative example is 3159cm ^-1 Here, as the amount of the seed crystal added was increased, the position of the-OH stretching vibration absorption peak in examples 1 to 7 was from 3159cm ^-1 Is positioned 3300cm ^-1 The position shifts, and the intensity of the-OH diffraction peak gradually increases, which indicates that more-OH is possibly successfully introduced into the seed crystal induced Schlemn mineral, and is beneficial to adsorbing heavy metal. The surface of the iron hydroxyl mineral can have three surface hydroxyl functional groups with different contents, different surface hydroxyl functional groups are named as A, B and C type hydroxyl groups according to different coordination of oxygen and iron, and each type of hydroxyl group has obviously different acidity and reactivity to an adsorbent. The hydroxyl group of type A is considered to be the most active, the hydroxyl group of type BAnd the C-type hydroxyl group is considered to be inert and does not substantially participate in the reaction.

Ore-combining cycle and yield

As can be seen from fig. 4, the addition of seed crystals to induce schwann mineral synthesis accelerates the rate of ferrous oxidation by acidithiobacillus ferrooxidans, the ferrous oxidation of the control example was complete at 66 hours, while the example was almost complete at around 42 hours.

As can be seen from FIG. 5, the ferric iron in the comparative example is hydrolyzed into ore within 66h, while the ferric iron in the example is precipitated almost within 42h, so that the period for synthesizing Schneider minerals by microorganisms is greatly shortened, and the defect of long period for forming ore by microorganisms is overcome to a certain extent; in addition, the addition of seed crystals increases the rate of iron (about 3% to 5%) being hydrolyzed to ore.

As can be seen from fig. 6, the addition of the seed crystals can increase the yield of the schlerian mineral, and the total yield of the minerals of examples 1 to 7 is 8.0%, 11.3%, 15.9%, 19.9%, 33.1%, 58.3% and 96.7% higher than that of the comparative example. The net yields of minerals from example 1 to example 7 are 7.3%, 10%, 13.2%, 14.6%, 22.5%, 37.1%, 54.3% higher than the comparative examples, respectively. The net yield here refers to the yield of schwann mineral after deducting the weight of added seeds, since the seeds may not be fully used and are nanoparticles which have been washed away in the washed mineral, and are therefore the lowest net yield here. Therefore, the invention is a high-yield Schneider mineral synthesis method.

Application of Schwertmannite in removing pentavalent arsenic and hexavalent chromium pollution in water body

Adsorption batch experiments:

EXAMPLES 1 TO 7 synthetic Schneider minerals, COMPARATIVE EXAMPLE AND A batch experiment reaction system for adsorbing As (V) and Cr (VI) by beta-FeOOH was carried out by charging 30mL of 0.1M NaNO containing specified concentrations of As (V) and Cr (VI) into a 50mL centrifuge tube ₃ Adding 15mg of solid sample (solid concentration is 0.5 g/L) into the background solution, and then placing the solution in a shaking table with the rotating speed of 180r/min and the temperature of 25 ℃ for 24 hours. And the change in pH was by 0.1M HNO ₃ And 0.1M NaOH. All samples were set for 3 parallel treatments per group.

Adsorption isotherm experiments: the solution pH was maintained at 3 by setting the initial As (V) and Cr (VI) concentrations at 5, 15, 30, 60 and 100mg/L, respectively.

pH adsorption experiment: examples 3 and 6 and comparative examples and seed crystals were used for the adsorption experiments. The initial As (V) and Cr (VI) concentrations were all 30mg/L, setting the pH at 2, 3, 4, 5, 6, 7, 8, respectively.

Adsorption kinetics experiment: examples 3 and 6 and comparative examples and seed crystals were used for the adsorption experiments. Initial As (V) and Cr (VI) concentrations were both 30mg/L, pH 3, and sampling time points were set at 1, 2, 5, 10, 20, 30, 60, 120, 180, 360, 720, 1080, 1440 minutes.

After the three groups of experimental reactions are finished, taking supernate and filtering the supernate through a 0.22 mu m filter membrane, and respectively measuring the mass concentration of As and Cr in the filtrate. And calculating the removal rate of As (V) and Cr (VI) and the adsorption capacity corresponding to the initial concentration in different embodiments (different seed crystal adding amounts), and obtaining the removal effect and the adsorption amount of As (V) with different initial concentrations As shown in FIG. 7; the removal effect and the adsorption amount of the obtained Cr (VI) with different initial concentrations are shown in FIG. 8; the effect of pH on As (V) removal is shown in FIG. 9; the effect of pH on Cr (VI) removal is shown in FIG. 10; the adsorption kinetics results are shown in fig. 11.

As can be seen from fig. 7: under acidic conditions (pH 3), the removal rate of As (V) by examples 1 to 7 prepared by the present invention is significantly stronger than that of comparative example and beta-FeOOH, and particularly, the adsorption capacity of example 6 is increased by about 2 to 4 times at As (V) of 15, 30, 60 and 100 mg/L.

As can be seen from fig. 8: under acidic conditions (pH 3), the Cr (VI) removal rates of examples 1 to 7 prepared by the present invention are all better than that of comparative example, and the Cr (VI) removal rate of example 3 is the best.

As can be seen from fig. 9: the removal of As (V) by the prepared Schneider mineral under acidic and neutral conditions is greatly better than that of a comparative example and a seed crystal, the optimal adsorption pH of the comparative example to As (V) is 7, the removal rate of As (V) by example 3 at pH 6-8 is over 90%, and the removal rate of As (V) by example 6 at pH 2-8 is over 90%, which shows that the removal effect of As (V) by example 6 is extremely strong, and the adsorption saturation is not reached in a system with the initial concentration of As (V) of 30mg/L.

As can be seen from fig. 10: the removal effect of the Schneider minerals prepared by the invention on Cr (VI) is better than that of seed crystals under acidic and neutral conditions and is not weaker than that of comparative examples, the optimal adsorption pH values of the examples and the comparative examples on Cr (VI) are respectively 5-6, the adsorption capacity of the examples and the comparative examples on Cr (VI) is gradually enhanced at pH 2-6, and the adsorption capacity of the examples and the comparative examples on Cr (VI) is gradually reduced at pH 6-8. The seed crystal has poorer removal capability on As (V) and Cr (VI) than the comparative example which is inferior to the example, so the example never enhances the adsorption capability of As (V) and Cr (VI) because an adsorbent with stronger adsorption capability is introduced, and the seed crystal in the discovery plays a role in modifying the structure of the Schwerer mineral synthesized in the example, guiding the synthesis of the Schwerer mineral, forming more adsorption active sites or exposing more adsorption active sites, and improving the adsorption activity and the adsorption capacity of the Schwerer mineral.

As can be seen from fig. 11: the adsorption kinetics of the examples 3 and 6 and the comparative example show that the adsorption of As (V) and Cr (VI) reaches the equilibrium at 12h (720 min), the removal rate of As (V) and Cr (VI) of the example 6 is higher than that of the comparative example, and the adsorption capacities of As (V) and Cr (VI) at the adsorption equilibrium are higher than that of the comparative example.

The invention systematically researches the feasibility of beta-FeOOH As a seed crystal for mediating and biosynthesizing the nano-scale Schneider minerals, and the inventor finds that under the induction action of specific functional groups (a large number of hydroxyl groups) of the beta-FeOOH, the form, the structure and the surface property of the Schneider minerals are successfully regulated in a Schneider mineral microbial mineralization system, the number of the functional groups is increased, more adsorption active sites are formed, and the removal rate and the adsorption capacity of the Schneider minerals on As (V) and Cr (VI) are improved. In addition, the Schneider mineral prepared by the method has high yield, short synthesis period and low cost, overcomes the difficulty that the pollution treatment effect of the Schneider mineral on As (V) and Cr (VI) in an acidic water body is poor to a certain extent, and can be applied to the treatment of acidic mine wastewater. In any case. The invention makes a contribution to the high-performance adsorbent for biosynthesis and has important significance for deepening the understanding of the biosynthesis of the Schneider minerals.

The above examples are only preferred embodiments of the present invention, which are intended to illustrate the present invention, but not to limit the present invention, and those skilled in the art should be able to make changes, substitutions, modifications, etc. without departing from the spirit of the present invention.

Claims (9)

1. The biosynthesis method of the Schwerer mineral mediated by adding the exogenous seed crystal is characterized by comprising the following steps:

(1) Adding a beta-FeOOH nano seed crystal solution into a ferrous sulfate solution, and then adding an A. Ferrooxidans resting cell suspension to obtain a mixed solution; the concentration of the beta-FeOOH nano seed crystal solution is 0.001 to 0.1g/mL; the volume ratio of the beta-FeOOH nano seed crystal solution to the mixed solution is 2 to 128:1000, parts by weight;

the preparation method of the beta-FeOOH nano seed crystal solution comprises the following steps: dissolving ferric chloride in absolute ethyl alcohol, adding deionized water, mixing and stirring uniformly to obtain a reaction solution, and reacting at the temperature of 80-100 ℃ for 36-54 h; after the reaction is finished, centrifuging, washing, freezing and drying to obtain beta-FeOOH nano seed crystal; adding water into the obtained beta-FeOOH nano seed crystal and performing ultrasonic dispersion to obtain a beta-FeOOH nano seed crystal solution;

(2) Culturing the mixed solution in the step (1) at 25-30 ℃ for 42-72h, and after the culture is finished; and washing, freeze-drying and sieving the mineral precipitate to obtain the Schneider mineral which is mediated and synthesized by adding the exogenous seed crystal.

2. The method for biosynthesis of Schlemn's mineral with the addition of exogenous seeds as recited in claim 1, wherein said suspension of A. Ferrooxidans resting cells in step (1)A. ferrooxidansHas a density of 1X 10 ⁸ ~3×10 ⁸ cells/ml。

3. The biosynthesis method of an exogenic seed crystal mediated Schwerner mineral, according to claim 1, characterized in that the concentration of ferrous sulfate in the mixed solution in the step (1) is 20 to 160mMol/L;

the volume ratio of the suspension of the ferrooxidans resting cells to the mixed solution is 1 to 50-100.

4. The biosynthesis method of Schwerner mineral mediated by adding exogenous seed crystals as claimed in claim 1, wherein the culture in step (2) is carried out in a shaking table at 150 to 200 r/min;

the washing is deionized water washing; the temperature of the freeze drying is-30 to-45 ℃, and the time is 12 to 36 hours; and the screening is to pass through a sieve with 100 to 200 meshes.

5. The method as claimed in claim 1, wherein the ferric chloride is FeCl ₃ ·6H ₂ O; the concentration of ferric chloride in the reaction liquid is 0.2 to 0.4Mol/L; the volume ratio of the absolute ethyl alcohol to the deionized water is 1:1 to 1.5;

the washing is absolute ethyl alcohol and deionized water washing to be neutral; the freeze drying time is 12 to 36h;

the time of ultrasonic dispersion is 30 to 45 minutes.

6. The method for biosynthesis of Schlemn's mineral with the addition of exogenous seeds as claimed in claim 1, wherein the suspension of A. Ferrooxidans resting cells is prepared by the following steps:

sterilizing a 9K culture medium at high temperature and high pressure, inoculating A. Ferrooxidans bacteria, adding ferrous sulfate, adjusting the pH, and culturing for 2 to 3 days; filtering to remove iron precipitate, centrifuging the filtrate, collecting thalli, washing and suspending to obtain A. Ferrooxidans resting cell suspension.

7. The biosynthesis method of an exogenic seed crystal mediated Schlemm mineral, according to claim 6, characterized in that the centrifugation temperature is 4 to 7 ℃, the centrifugation force is 10000 to 12000g, and the time is 8 to 10 minutes;

the volume of the suspension is 1/50 to 1/100 of the culture medium;

the pH is adjusted to H ₂ SO ₄ Adjusting the pH to 2-3.

8. An exogenously seeded mediated synthesized schlerian mineral synthesized according to the biosynthetic method of any of claims 1 to 7.

9. Use of the exogenously seeded mediated synthesis of schneiderian minerals of claim 8 for the removal of As (V) and Cr (VI) contamination in a body of water.

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