Preparation method of ternary microorganism modified steel slag

Abstract

The invention provides a preparation method of ternary microorganism modified steel slag, and relates to the technical field of steel slag modification, and the preparation method comprises the following steps: preparing a liquid culture medium, inoculating bacillus pasteurii, saccharomyces cerevisiae and carbonic anhydrase bacteria into the liquid culture medium, with the inoculation total mass being 10% of the total mass of the liquid culture medium, so as to obtain a mixed bacteria solution; placing in a constant-temperature shaking incubator for culturing, so that the concentration of the mixed bacterial liquid reaches 5 * 10 < 8 > cells / ml to 8 * 10 < 9 > cells / ml; steel slag with the particle size being 5-10 mm is screened out, cleaned and dried; the screened steel slag is soaked in a mixed bacteria solution, urea is added, the mass ratio of the mixed bacteria solution to the steel slag is 0.4-1.25, the concentration of the urea is 1.5 mol / L-3 mol / L, the reaction temperature is controlled to be 33-37 DEG C, the soaking time is 24-72 h, and the modified steel slag is prepared. Free calcium oxide in the steel slag can be effectively reduced, the water absorption expansion rate is reduced, the compressive strength is improved, and the resource utilization rate of the steel slag is increased.

Description

Technical Field

[0001] The invention relates to the technical field of steel slag modification, and in particular to a method for preparing ternary microbial modified steel slag. Background Art

[0002] According to statistics from the World Steel Association, the global crude steel output in 2023 will be 1.888 billion tons, and China's crude steel output will be 1.019 billion tons, accounting for 56.59% of the global crude steel output. In recent years, my country has produced more than 100 million tons of steel slag each year, but the comprehensive utilization rate of steel slag is still less than 50%, which is far from the goal of increasing my country's steel slag utilization rate to 95% proposed in the "Industrial Green Development Plan (2016-2020)". The reason for the low utilization rate of steel slag is that on the one hand, the hydration activity of steel slag is low, the hydration rate of silicate minerals is low, and the utilization of mineral components is low; on the other hand, the free calcium oxide and free magnesium oxide crystals in the steel slag are closely arranged, and the volume expands and cracks when it encounters water (the volume expansion rate is 97.8%), causing poor volume stability and causing great harm. At present, most steel slag is still stored in the open air, which not only occupies land and pollutes the environment, but also the heavy metal ions in the steel slag are washed and leached by rainwater, which will pollute groundwater and soil, causing great harm to water bodies. The accumulated steel slag is also easily eroded and gradually powdered, forming dust, which brings great pressure to the air. How to improve the resource utilization rate of steel slag has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art or related technology, and provides a preparation method of ternary microbial modified steel slag, which can effectively reduce the free calcium oxide in the steel slag, reduce the water absorption expansion rate, improve the compressive strength, and improve the resource utilization rate of the steel slag.

[0004] The first aspect of the present invention discloses a method for preparing ternary microbial modified steel slag, comprising: preparing a liquid culture medium, inoculating Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria in the liquid culture medium, wherein the total mass of the inoculation is 10% of the total mass of the liquid culture medium, obtaining a mixed bacterial solution, placing the mixed bacterial solution in a constant temperature shaking incubator for cultivation, and making the concentration of the mixed bacterial solution reach 5×10 8 cells / ml~8×10 9 cells / ml; screen out steel slag with a particle size of 5mm-10mm, wash it and dry it; soak the screened steel slag in a mixed bacterial solution and add urea, the mass ratio of the mixed bacterial solution to the steel slag is 0.4-1.25, the urea concentration is 1.5mol / L-3mol / L, the reaction temperature is controlled between 33℃-37℃, the soaking time is 24h-72h, and the modified steel slag is obtained.

[0005] According to the method for preparing ternary microbial modified steel slag provided by the present invention, preferably, the volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2.

[0006] According to the method for preparing ternary microbial modified steel slag provided by the present invention, preferably, the mass ratio of the mixed bacterial liquid to the steel slag is 0.6.

[0007] According to the method for preparing ternary microbial modified steel slag provided by the present invention, preferably, the urea concentration is specifically 2.5 mol / L.

[0008] According to the method for preparing ternary microbial modified steel slag provided by the present invention, preferably, the step of preparing the liquid culture medium specifically comprises:

[0009] Add 9.6g urea, 15g peptone, 3g beef extract, 10g glucose, 5.6g yeast extract powder, 5g disodium hydrogen phosphate, 0.28g potassium chloride, 2g calcium carbonate, 20g sucrose, 1g ammonium sulfate, and 1g magnesium sulfate to every 1L of deionized water, adjust the pH to 11-13, place it at 120℃ and 0.1MPa for sterilization for 25min-35min, take it out and cool it to obtain a liquid culture medium.

[0010] According to the preparation method of ternary microbial modified steel slag provided by the present invention, preferably, the culture conditions of the mixed bacterial solution specifically include: at a temperature of 33°C to 38°C, setting the speed of the constant temperature oscillating incubator to 150 r / min to 170 r / min, and the culture time to 24h to 72h.

[0011] According to the method for preparing ternary microbial modified steel slag provided by the present invention, preferably, after the soaking time reaches 72 hours, the free calcium oxide content in the modified steel slag is 1.34%.

[0012] The beneficial effects achieved by the present invention include at least: the present invention provides a method for microbial pretreatment of steel slag with low economic cost, low resource consumption, environmental protection, simple process and short treatment cycle, which can reduce the content of free calcium oxide in steel slag, and the volume stability of the treated steel slag is stable, so it can be used as steel slag aggregate in actual engineering concrete, thereby improving the resource utilization rate of steel slag. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The figure shows the precipitation amount after mixing different proportions of multi-bacteria in an aerobic environment.

[0014] Figure 2 The free calcium oxide content in the steel slag after treating the steel slag at different temperatures is shown.

[0015] Figure 3The free calcium oxide content in the steel slag after treating the steel slag at different times is shown.

[0016] Figure 4 The free calcium oxide content in steel slag after treating the steel slag at different urea concentrations is shown. DETAILED DESCRIPTION

[0017] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] According to one embodiment of the present invention, a preparation method of ternary microbial modified steel slag is disclosed, comprising: preparing a liquid culture medium, inoculating Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria in the liquid culture medium, the total mass of the inoculation being 10% of the total mass of the liquid culture medium, obtaining a mixed bacterial solution, placing the mixed bacterial solution in a constant temperature shaking incubator for cultivation, and making the concentration of the mixed bacterial solution reach 5×10 8 cells / ml~8×10 9 cells / ml; screen out steel slag with a particle size of 5mm-10mm, wash it and dry it; soak the screened steel slag in a mixed bacterial solution and add urea, the mass ratio of the mixed bacterial solution to the steel slag is 0.4-1.25, the urea concentration is 1.5mol / L-3mol / L, the reaction temperature is controlled between 33℃-37℃, the soaking time is 24h-72h, and the modified steel slag is obtained.

[0019] According to the above embodiment, further, the volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2.

[0020] According to the above embodiment, further, the mass ratio of the mixed bacterial liquid to the steel slag is specifically 0.6.

[0021] According to the above embodiment, further, the urea concentration is specifically 2.5 mol / L.

[0022] According to the above embodiment, further, the step of preparing the liquid culture medium specifically includes:

[0023] Add 9.6g urea, 15g peptone, 3g beef extract, 10g glucose, 5.6g yeast extract powder, 5g disodium hydrogen phosphate, 0.28g potassium chloride, 2g calcium carbonate, 20g sucrose, 1g ammonium sulfate, and 1g magnesium sulfate to every 1L of deionized water, adjust the pH to 11-13, place it at 120℃ and 0.1MPa for sterilization for 25min-35min, take it out and cool it to obtain a liquid culture medium.

[0024] According to the above embodiment, further, the culture conditions of the mixed bacterial solution specifically include: at a temperature of 33°C to 38°C, setting the speed of the constant temperature shaking incubator to 150 r / min to 170 r / min, and the culture time to 24h to 72h.

[0025] According to the above embodiment, further, after the immersion time reaches 72 hours, the free calcium oxide content in the modified steel slag is 1.34%.

[0026] like Figure 1 As shown, according to another embodiment of the present invention, a process for determining the optimal ratio of ternary microorganisms is also disclosed:

[0027] According to the law of coordinated growth and reproduction of multiple microorganisms and their ability in mineralization, three bacteria, namely Bacillus pasteurianus, Saccharomyces cerevisiae and Carbonic anhydrase bacteria, were selected;

[0028] Prepare 2 mol / L urea solution, 2 mol / L calcium acetate solution, and 20 g / L glucose solution. Use a pipette to add 10 mL of urea solution and 10 mL of calcium acetate solution to a beaker, then add 10 mL of the mixed bacterial solution to the beaker. Place it in a 30°C oven for 2 days, filter it, dry it, and calculate the amount of precipitation. Figure 1 The amount of precipitation shown: the proportional relationship between each group on the horizontal axis in the figure is the volume ratio of Bacillus pasteurian, Saccharomyces cerevisiae and carbonic anhydrase bacteria. The group with a ratio of 10:0:0 means that the mixed bacterial liquid only contains Bacillus pasteurian, and Saccharomyces cerevisiae and carbonic anhydrase bacteria are not added, which serves as the control group. The group with a ratio of 6:4:0 means that Bacillus pasteurian and Saccharomyces cerevisiae are mixed in a ratio of 6:4, and carbonic anhydrase bacteria are not added, which serves as the control group.

[0029] From the analysis of the precipitation amount, the highest precipitation amount was 1.81 g and 1.79 g, and the corresponding mixed bacterial solution ratio was 5:2:3 and 5:3:2; the optimal ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria was finally determined to be 5:2:3 and 5:3:2. Under the optimal mixing ratio, the OD value (using the absorbance value of bacteria to measure the concentration of the bacterial solution), pH value and conductivity value of the mixed bacterial solution were further detected to be better than those of the control group: OD600 was 1.598 and 1.565 respectively, the pH value fluctuated around 8.5, and the conductivity was stable at 259 ms / min and 274 ms / min respectively.

[0030] like Figure 2 , Figure 3 and Figure 4 As shown, according to another embodiment of the present invention, the influence of different treatment conditions on the free calcium oxide (F-Cao) content during slag immersion is also disclosed:

[0031] Figure 2 The volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2, which are shown in the chart with different lines. The group with a ratio of 10:0:0 means that the mixed bacterial solution only contains Bacillus pasteurianus, without Saccharomyces cerevisiae and carbonic anhydrase bacteria, as the control group. The group with a ratio of 6:4:0 means that Bacillus pasteurianus and Saccharomyces cerevisiae are mixed in a ratio of 6:4, without carbonic anhydrase bacteria, as the control group. Different reaction temperatures lead to different contents of free calcium oxide (F-CAO) remaining in the treated steel slag. The ternary microbial bacterial solution with a ratio of 5:2:3 or 5:3:2 is better than the control group. The treatment effect is best when the reaction temperature is around 35 degrees Celsius.

[0032] Figure 3 The volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2, which are shown in the chart with different lines. The group with a ratio of 10:0:0 means that the mixed bacterial solution only contains Bacillus pasteurianus, without Saccharomyces cerevisiae and carbonic anhydrase bacteria, as the control group, and the group with a ratio of 6:4:0 means that Bacillus pasteurianus and Saccharomyces cerevisiae are mixed in a ratio of 6:4, without carbonic anhydrase bacteria, as the control group. With the increase of reaction time, the content of free calcium oxide (F-CAO) remaining in steel slag gradually decreases, and the treatment effect of the ternary microbial bacterial solution with a ratio of 5:2:3 or 5:3:2 is better than that of the control group at the same reaction time.

[0033] Figure 4 The volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2, which are shown in the chart with different lines. The group with a ratio of 10:0:0 means that the mixed bacterial solution only contains Bacillus pasteurianus, without Saccharomyces cerevisiae and carbonic anhydrase bacteria, which is used as the control group. The group with a ratio of 6:4:0 means that Bacillus pasteurianus and Saccharomyces cerevisiae are mixed in a ratio of 6:4, without carbonic anhydrase bacteria, which is used as the control group. The addition of different concentrations of urea leads to different contents of residual free calcium oxide (f-cao) in the treated steel slag. The ternary microbial bacterial solution with a ratio of 5:2:3 or 5:3:2 is better than the control group, and the treatment effect is best when the urea concentration is 2.5 mol / L.

[0034] According to another embodiment of the present invention, the physical properties and water expansion rate test of steel slag before and after modification are also disclosed: based on the preparation method of the ternary microbial modified steel slag disclosed in the above embodiment, the inoculation volume ratio of Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria is 5:2:3 or 5:3:2; the mass ratio of the mixed bacterial solution to the steel slag is 0.6; the urea concentration is specifically 2.5 mol / L; the soaking time is 72h. The modified steel slag is tested according to the test method of aggregate physical properties in GB / T14685-2011 "Pebbles and Crushed Stones for Construction" and the test method of steel slag volume stability in GB / T24175-2009 "Steel Slag Stability Test Method". The steel slag is selected after screening by a screening machine, and the particle size is 1.18~2.36mm and 4.75~9.5mm. The steel slag is rinsed clean and dried for standby use. The water absorption rate and crushing index of the steel slag aggregate before and after modification are tested. Among them, the water absorption rate of the test group with a particle size of 1.18~2.36mm dropped from the original 7.6% to 4.3%, a decrease of 43.42%, and the crushing index dropped from the original 4.65% to 4.31%, a decrease of 7.31%; among them, the water absorption rate of the test group with a particle size of 4.75~9.5mm dropped from the original 3.9% to 2.83%, a decrease of 27.44%, and the crushing index dropped from the original 5.52% to 5.29%, a decrease of 4.17%; compared with the untreated steel slag, its water absorption rate and crushing value were significantly reduced. The treated steel slag showed only a 0.95% change in the immersion expansion rate test. The untreated steel slag showed a 6.04% change in the immersion expansion rate test, which was 84.27% lower than the untreated steel slag, meeting the specification requirements.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. 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. A method for preparing ternary microbial modified steel slag, characterized in that: include: A liquid culture medium was prepared, and Bacillus pasteurianus, Saccharomyces cerevisiae and carbonic anhydrase bacteria were inoculated in the liquid culture medium, and the total inoculation mass was 10% of the total mass of the liquid culture medium to obtain a mixed bacterial solution, which was placed in a constant temperature shaking incubator for culture until the concentration of the mixed bacterial solution reached 5×10 8 cells / ml~8×10 9 cells / ml; Screen out steel slag with a particle size of 5mm-10mm, wash it and dry it; The screened steel slag is soaked in the mixed bacterial solution and urea is added, the mass ratio of the mixed bacterial solution to the steel slag is 0.4-1.25, the urea concentration is 1.5mol / L-3mol / L, the reaction temperature is controlled between 33°C-37°C, the soaking time is 24h-72h, and the modified steel slag is obtained.

2. The method for preparing ternary microbial modified steel slag according to claim 1, characterized in that: The volume ratio of the Bacillus pasteurianus, the Saccharomyces cerevisiae and the carbonic anhydrase bacteria is 5:2:3 or 5:3:

2.

3. The method for preparing ternary microbial modified steel slag according to claim 1, characterized in that: The mass ratio of the mixed bacterial liquid to the steel slag is specifically 0.

6.

4. The method for preparing ternary microbial modified steel slag according to claim 1, characterized in that: The urea concentration is specifically 2.5 mol / L.

5. The method for preparing ternary microbial modified steel slag according to claim 1, characterized in that: The steps of preparing the liquid culture medium specifically include: Add 9.6g urea, 15g peptone, 3g beef extract, 10g glucose, 5.6g yeast extract powder, 5g disodium hydrogen phosphate, 0.28g potassium chloride, 2g calcium carbonate, 20g sucrose, 1g ammonium sulfate, and 1g magnesium sulfate to every 1L of deionized water, adjust the pH to 11-13, place it at 120℃ and 0.1MPa for sterilization for 25min-35min, take it out and cool it to obtain a liquid culture medium.

6. The method for preparing ternary microbial modified steel slag according to claim 1, characterized in that: The culture conditions of the mixed bacterial solution specifically include: Under the temperature condition of 33℃~38℃, set the speed of the constant temperature shaking incubator to 150 r / min ~170r / min, and the incubation time to 24h~72h.

7. The method for preparing ternary microbial modified steel slag according to any one of claims 1 to 6, characterized in that: After the immersion time reaches 72 hours, the free calcium oxide content in the modified steel slag is 1.34%.

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