CN109224364B - Method for reducing alkalinity of Bayer process red mud by using penicillium oxalicum - Google Patents

Abstract

The invention discloses a method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum, which belongs to the technical field of microbial application and comprises the following steps: (1) naturally air-drying and sieving the red mud, dividing the obtained red mud into a first part and a second part, adding the pretreated bagasse and bran into the first part of the red mud, and uniformly mixing to obtain the red mud added with the biomass; (2) filling the soil column, filling quartz sand at the bottom of the soil column, using the second part of red mud as a middle layer, filling the red mud added with biomass at the top, and inoculating the penicillium oxalicum strain into the second part of red mud; (3) and filling water into the filled soil column from bottom to top, keeping the water content at 60-80%, and cultivating at room temperature to reduce the alkalinity of the red mud. The method of the invention combines the biomass and the penicillium oxalicum, can reduce the pH value of the red mud to 6.66, has wide sources of used raw materials, low cost, no secondary pollution in microbial remediation and obvious effect, and can be applied to red mud yards.

Description

Method for reducing alkalinity of Bayer process red mud by using penicillium oxalicum

Technical Field

The invention belongs to the technical field of microorganism application, and particularly relates to a method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum.

Background

The Bayer process red mud is high-alkaline solid waste discharged in the industrial production process of alumina, 1.5-2.0 t of red mud is generated when 1 t of alumina is produced, the comprehensive utilization difficulty is high, the discharged red mud is mainly piled, about 40 hundred million tons of red mud to be treated are accumulated globally in 2017, and the red mud is increased at the rate of 1.7 hundred million tons per year. The environmental safety problem of the red mud disposal site is increasingly serious, and the problem of how to effectively dispose and utilize the red mud is urgent. Ecological restoration of red mud yards has been tried at home and abroad, but due to strong alkalinity of red mud, high salt content, lack of nutrients and difficulty in plant growth. The research idea of red mud soil formation is provided by the national teaching of Schachlerian of environmental and ecological engineering team of the university of China and south China, and the red mud is converted into a matrix similar to soil by physical-chemical-biological methods and the like, so that the improved red mud has basic conditions for plant growth, and the harmless treatment of the red mud is realized.

The microorganism has high propagation speed and large quantity, can decompose organic matters, release nutrient elements, improve the soil structure and increase the soil fertility; some special functional strains can be metabolized to generate organic acid, the alkalinity of the red mud is reduced, a condition suitable for growth of plants is provided, and the soil formation progress of the red mud is promoted. In recent years, researches show that Acidobacteriaceae, Nitrosomonadaceae, Caulobacter asiaticus and the like can grow in an unrepaired red mud environment, and provide important indexes for ecological restoration of a red mud yard.

The traditional red mud matrix improvement method comprises a physical method and a chemical method, but the two methods have higher cost, large occupied area of a red mud yard, large consumption of spraying chemical reagents and the like, and thus the methods are difficult to apply in practice. The microorganism has the characteristics of high propagation speed, low application cost, no secondary pollution and the like, and has wide application prospect. However, research on the repair of red mud by using a biological method is relatively less. Therefore, the actual remediation of the red mud by using a low-cost biological method is urgently needed in the field, so that technical support is provided for the implementation of the red mud soil formation.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum, which is simple to operate, economic, effective and environment-friendly, so as to solve the environmental safety problem of stacking a large amount of Bayer process red mud.

In order to achieve the technical purpose, the invention provides the following technical scheme:

the invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing penicillium oxalicum, which comprises the following steps:

(1) naturally air-drying and sieving the red mud, dividing the obtained red mud into a first part and a second part, adding the pretreated bagasse and bran into the first part of the red mud, and uniformly mixing to obtain the red mud added with the biomass;

(2) filling the soil column, filling quartz sand at the bottom of the soil column, using the second part of red mud as a middle layer, filling the biomass-added red mud obtained in the step (1) at the top, and inoculating the penicillium oxalicum strain into the first part of red mud to obtain the filled soil column;

(3) and (3) filling water into the filled soil column in the step (2) from bottom to top, keeping the water content at 60-80%, and cultivating at room temperature to reduce the alkalinity of the red mud, increase the content of organic matters in the red mud and promote the formation of red mud aggregates.

Preferably, in the step (1), the bagasse, the bran and the first part of red mud are (6-18%) by mass: (5-15%): (67-89%).

Preferably, in the step (1), the pretreatment is one of hydrothermal treatment, sulfuric acid treatment, calcium oxide treatment and hydrogen peroxide treatment.

Further, the pretreatment adopts hydrothermal treatment, and comprises the following specific steps:

(a) drying bagasse and bran, then crushing the bagasse and bran by using a crusher, and sieving the crushed bagasse and bran by using a sieve of 60-80 meshes;

(b) adding the sieved bagasse, bran and water into a beaker, placing the beaker in a high-pressure steam sterilization pot, heating to 150-180 ℃, keeping the pressure at 4.0-6.0 MPa, treating for 5-10 min, and finally blasting the biomass by suddenly reducing the pressure to obtain the pretreated bagasse and bran.

Preferably, in the step (2), the concrete steps of filling the soil column are as follows:

1) establishing an indoor soil column device model, fixing a transparent column on an iron frame, wherein the inner diameter of the cross section of the soil column is 6.3cm, the outer diameter of the cross section of the soil column is 7.0cm, small holes with plugs are arranged on the column body every 10cm of depth, a leaching device is arranged above the soil column to simulate the rain weather of a red mud storage yard, the tip of the lowest end of the soil column is connected with a rubber tube, and the rubber tube is connected into a conical bottle to contain percolate;

2) filling the soil column, filling quartz sand with the thickness of 6cm at the bottom (the depth of less than 65 cm) of the soil column, filling a second part of red mud at the depth of 25-65 cm of the soil column, and filling the red mud added with the biomass obtained in the step (1) at the depth of 0-25 cm of the soil column;

3) two soil columns are respectively filled and named as an E column and an F column, the F column is periodically inoculated with penicillium oxalicum agent, and the E column is used as a control and is not inoculated with the agent.

Further, the preparation process of the penicillium oxalicum agent comprises the following steps:

a) preparing a glucose liquid culture medium, filling 100mL of the culture medium into a 250mL conical flask, and performing high-pressure steam sterilization;

b) inoculating penicillium oxalicum to a sterilized and cooled culture medium, and culturing at the temperature of 25-30 ℃ and at the speed of 160-180 r/min for 72-96 h;

c) inoculating the cultured penicillium oxalicum agent into an F column.

In earlier experiments, an inventor team screens a microbial strain penicillium oxalicum with good alkali resistance and high acid production performance from a red mud storage yard, and the microbial sequence number is as follows: MF802280, wherein the penicillium oxalicum has significant effects on the regulation of red mud alkalinity, and as an important cellulase-producing microorganism, the penicillium oxalicum can degrade cellulose and has important effects in carbon circulation.

The principle of the invention is as follows: bayer process red mud has strong alkalinity, nutrient deficiency and loose structure, and plants are difficult to grow on primary red mud yards. According to the invention, bagasse and bran subjected to hydrothermal treatment are added into Bayer process red mud to serve as a carbon source and a nitrogen source required by the survival of microorganisms, and then penicillium oxalicum agent is applied into the red mud, so that a large amount of organic acid is produced by metabolism, and the alkalinity of the red mud can be effectively reduced; the penicillium oxalicum can decompose biomass by using bagasse and bran as carbon-nitrogen sources, and meanwhile, the penicillium oxalicum can also secrete cellulase to increase the organic matter content in the red mud; and secondly, the hypha physical winding effect of the penicillium oxalicum can further promote the formation of red mud aggregates.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention provides a method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum, which can reduce the pH value of the red mud to 6.66 by using a method combining biomass and penicillium oxalicum, improve the content of organic matters in the red mud and promote the formation of aggregates in the red mud. The method has the advantages of wide sources of used raw materials, low cost, no secondary pollution in microbial remediation and remarkable effect, can be applied to the red mud disposal site, and can effectively solve the problem of environmental pollution caused by the red mud disposal site.

Drawings

FIG. 1 shows the effect of different pretreatment methods of biomass on the acid production of Penicillium oxalicum.

FIG. 2 is a diagram of a model of the soil column. (F: red mud column with Penicillium oxalicum; E: red mud column without Penicillium oxalicum)

Fig. 3 is a graph of red mud pH, EC (conductivity) and total alkali over time.

Fig. 4 is a graph of the change of organic matter content in red mud with time.

FIG. 5 is a graph showing the change of urease and cellulase contents in red mud with time.

FIG. 6 is a graph showing the change of the alkaline cation content (Na +, Ca2+, K +, Mg2 +) in red mud at 30 days after remediation.

Fig. 7 is an SEM image of red mud.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments, and all other embodiments obtained by those skilled in the art without any creative work based on the embodiments of the present invention belong to the protection scope of the present invention.

The invention will be further illustrated with reference to the following specific examples and the accompanying drawings:

example 1

The biomass pretreatment can adopt the following 4 methods, the optimal conditions of acid production by penicillium oxalicum are determined by comparing different biomass pretreatment methods, and the optimal pretreatment method is selected finally:

(1) hydrothermal treatment

Crushing bagasse and bran by using a crusher, sieving the crushed bagasse and bran by using a 60-mesh sieve (the aperture is 0.25 mm), and then mixing the bagasse, the bran and water according to a solid-liquid ratio of 1:10 placing in a beaker, placing in a high pressure steam sterilization pot, heating to 180 deg.C, maintaining the pressure at 4.0MPa for 5min, and finally suddenly reducing the pressure to explode the biomass.

(2) Sulfuric acid treatment

Crushing bagasse and bran, sieving with a 60-mesh sieve (aperture 0.25 mm), weighing appropriate amount of bagasse and bran, adding 1% (w/w) H2SO4 solution according to a solid-to-liquid ratio of 1:10, stirring well, and treating for 1H at 121 ℃ under high pressure steam.

(3) Calcium oxide treatment

Lime (calcium oxide as the main component) was slurried (to form calcium hydroxide) and then 0.075g calcium hydroxide and 5g water per gram of biomass was added and heated at 120 ℃ for 4 h.

(4) Hydrogen peroxide treatment

10.0g of bagasse and bran were weighed into a 250mL Erlenmeyer flask, in a solid-to-liquid ratio of 1:10, adding 5% (w/w) of H2O2 solution, uniformly stirring, and placing in a water bath constant temperature shaking box for processing for 24 hours at 30 ℃.

Preparing culture solution from the treated biomass and distilled water at a ratio of 1:5, inoculating penicillium oxalicum to the liquid culture medium, setting a blank control group, performing shake culture at 28 ℃ at 160r/min for 9 days, and measuring pH.

The results in fig. 1 show that the hydrothermal treatment and the H2SO4 treatment are both significantly higher than the CaO treatment and the H2O2 treatment (P < 0.05), and there is no significant difference between the hydrothermal treatment and the H2SO4 treatment, but compared with the two, the H2SO4 treatment requires the addition of chemical reagents, and if introduced into red mud remediation, exogenous ions are introduced, SO the hydrothermal treatment is adopted.

Example 2

The invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing penicillium oxalicum, which comprises the following steps:

(1) naturally air-drying and sieving the red mud, dividing the obtained red mud into a first part and a second part, and then adding the bagasse and the bran subjected to hydrothermal treatment into the first part of the red mud, wherein the mass percent of the bagasse, the bran and the first part of the red mud is 6%: 5%: 89 percent and uniformly mixing to obtain the red mud added with the biomass;

(2) filling a soil column, wherein a soil column model is shown in figure 2, a layer of 0-25 cm of E column and a layer of F column are red mud added with biomass, a layer of 25-65 cm of red mud is second part of red mud, quartz sand with the depth of 6cm is filled at the bottom of the column (below 65 cm), the red mud is prevented from losing along with the outflow of percolate, after the E column and the F column are filled, leaching is carried out on the red mud at irregular intervals, the rainfall weather of a red mud storage yard is simulated, and a penicillium oxalicum agent is inoculated in the F column every 3 days;

the preparation process of the penicillium oxalicum agent comprises the following steps:

a) preparing a glucose liquid culture medium, filling 100mL of the culture medium into a 250mL conical flask, and performing high-pressure steam sterilization (21 ℃, 20 min);

b) inoculating penicillium oxalicum to a sterilized and cooled culture medium, and culturing at 28 ℃ at 180r/min for 72 h;

c) inoculating the cultured penicillium oxalicum agent into an F column;

(3) filling water into the filled soil column from bottom to top, keeping the water content at 60-80%, cultivating at room temperature, reducing the alkalinity of the red mud, increasing the content of organic matters in the red mud, and promoting the formation of red mud aggregates.

Example 3

The invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing penicillium oxalicum, which comprises the following steps:

(1) naturally air-drying and sieving the red mud, dividing the obtained red mud into a first part and a second part, and then adding the bagasse and the bran subjected to hydrothermal treatment into the first part of the red mud, wherein the mass percent of the bagasse, the bran and the first part of the red mud is 18%: 15%: 67 percent, and uniformly mixing to obtain the red mud added with the biomass;

(2) filling a soil column, wherein a soil column model is shown in figure 2, a layer of 0-25 cm of E column and a layer of F column are red mud added with biomass, a layer of 25-65 cm of red mud is second part of red mud, quartz sand with the depth of 6cm is filled at the bottom of the column (below 65 cm), the red mud is prevented from losing along with the outflow of percolate, after the E column and the F column are filled, leaching is carried out on the red mud at irregular intervals, the rainfall weather of a red mud storage yard is simulated, and a penicillium oxalicum agent is inoculated in the F column every 3 days;

(3) filling water into the filled soil column from bottom to top, keeping the water content at 60-80%, cultivating at room temperature, reducing the alkalinity of the red mud, increasing the content of organic matters in the red mud, and promoting the formation of red mud aggregates.

Example 4

Analysis of the red mud obtained in example 2 for changes in pH, EC, Total alkali (Total alkali):

sampling red mud at the depth of 0cm, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column respectively on the 6 th, 12 th, 18 th, 24 th and 30 th days, air-drying the samples to constant weight, respectively weighing 5.0g of red mud in a centrifuge tube, then adding 25mL of deionized water (1: 5), shaking uniformly, standing for 30min, and determining the pH value and EC of the supernatant. 10mL of red mud leachate with the soil-water ratio of 1:5 is sucked and put into a 100mL conical flask, the content of CO32- (HCO 3-) in the sample is measured by a bromophenol blue indicator titration method, a bromophenol blue indicator is added into the supernatant, the supernatant is titrated to be colorless (pH 4.5) by using a H2SO4 standard solution, and the content of CO 32-and the content of HCO 3-are obtained through calculation. Total alkali in red mud is the sum of contents of CO32-, HCO3-, Al (OH) 4-and OH-, wherein the Al (OH) 4-content is determined and calculated from the Al content of the supernatant by inductively coupled plasma atomic emission spectrometry (ICP-AES, Optima 5300DV, Perkin Elmer, USA).

As a result, as shown in fig. 3, the pH of the red mud in the F column changed with time, and at day 18, the pH of the F column slightly increased, and it was considered that a large amount of free alkali was neutralized by acidic substances metabolized by penicillium oxalicum, and the bound alkali in the red mud was eluted. After day 24, the pH of the F column was maintained around 7, and there was a significant difference in pH at day 30 from that at day 6 (P < 0.05). In the E column, the pH value of the red mud is basically unchanged, the pH value is maintained at about 9, and no obvious difference exists within 30 days. At day 30, the pH of the F column is significantly lower than that of the E column (P is less than 0.05), which shows that the penicillium oxalicum can effectively reduce the pH of the red mud and has a good repairing effect. In the E column, EC decreases with time, probably because eluviation leads to migration of basic ions in the column. In the F column, the increase of EC with the increase of time is probably because the acidic substances generated by the penicillium oxalicum dissolve out the alkaline ions in the red mud. The day 24 EC was significantly higher in both columns than day 30, probably due primarily to eluviation. The total alkali of the F column is obviously lower than that of the E column (P < 0.05), which shows that acidic substances generated by the penicillium oxalicum have great influence on the alkalinity of the red mud.

In the F column, the pH value of red mud in a layer of 0-5 cm is obviously lower than that of the E column (P is less than 0.05), which shows that the activity of the penicillium oxalicum in the depth of the surface layer is higher and the action effect is more obvious. And the EC value of the red mud in the F column is obviously higher than that of the E column in a layer of 0-5 cm, which shows that the penicillium oxalicum can dissolve out a large amount of bound alkali in the red mud, so that the content of alkaline ions is increased. In the 35-45 cm layer, the pH value of the red mud of the F column is obviously lower than that of the E column (P is less than 0.05), which shows that acidic substances metabolized by penicillium oxalicum can migrate to the lower layer to react with alkaline substances in the red mud under the leaching action. In the F column, the total alkali content of the red mud is lower than that of the E column, and the total alkali content of the red mud in an unmodified 35-45 cm layer in the F column is lower than that of the E column, so that the alkaline property of the red mud can be obviously reduced by organic acid metabolized by penicillium oxalicum, and the red mud alkaline property can be well regulated and controlled.

Example 5

Analyzing changes of organic matters, urease and cellulase in the red mud obtained in example 2:

(1) determination of organic content

Sampling red mud at the depth of 0cm, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column respectively on days 6, 12, 18, 24 and 30, air-drying the samples to constant weight, grinding, accurately weighing 1.000g of red mud passing through a 100-mesh sieve, putting the red mud into a 50mL beaker, adding 3mL of water, fully shaking up, adding 10mL of 1mol/L (1/6K 2Cr2O 7) solution, then adding 10mL of concentrated sulfuric acid, continuously shaking up, standing for 20min, adding 10mL of water, shaking up, and standing overnight. And (3 mL) of the supernatant is sucked into a 10mL colorimetric tube, water is added until the scales are uniformly shaken, the measurement is carried out at the wavelength of 590nm, and the organic matter content is calculated according to a standard curve.

(2) Determination of Urease (Urease) content

Sampling red mud at the depth of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column on the 6 th, 12 th, 18 th, 24 th and 30 th days respectively, drying the samples to constant weight, weighing 5.0g of red mud sample into a 50mL conical flask, adding 1mL of toluene, uniformly shaking, adding 10mL of 10% urea solution and 20mL of citrate buffer solution with pH of 6.7 after 15min, uniformly shaking, and culturing for 24 hours in a 37 ℃ incubator. After the culture is finished, filtering, adding 1mL of filtrate into a 50mL volumetric flask, adding 4mL of sodium phenolate solution and 3mL of sodium hypochlorite solution, and shaking up while adding. Developing after 20min, and fixing volume. The color is measured in a spectrophotometer at 578nm wavelength within 1 h. (the blue color of indophenol remained stable for 1 h)

(3) Determination of cellulase (Cellulolytic enzyme) content

The red mud at the depth of 0cm, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column is sampled on the 6 th, 12 th, 18 th, 24 th and 30 th days respectively, the samples are dried to constant weight, 10.0g of red mud is weighed and placed in a 50mL conical flask, 1.5mL of toluene is added, the mixture is shaken uniformly and placed for 15min, 5mL of 1% carboxymethyl cellulose solution and 5mL of acetate buffer solution with pH value of 5.5 are added, and the triangular flask is placed in a 37 ℃ incubator for culturing for 72 h. After the culture is finished, filtering and taking 1mL of filtrate, and then carrying out colorimetric determination according to a color development method for drawing a standard curve. (in order to eliminate the error caused by original cane sugar and glucose in the soil, each soil sample needs to be controlled without matrix, the whole test needs to be controlled without soil, if the light absorption value of the sample exceeds the maximum value of the standard curve, the extraction multiple is increased or the cultivated soil sample is reduced.)

The experimental results are shown in fig. 4, where the organic content in both columns increased slightly with increasing time. On day 12, the organic content of the column was the highest and then decreased. The organic matter content of 0-25 cm layers in the two columns is obviously higher than that of 35-45 cm layers (P is less than 0.01). As can be seen from FIG. 5, the urease activity in the E, F two columns increased with time, while the urease activity in the E column was not significantly different from that in the F column, indicating that Penicillium oxalicum had little effect on urease activity. E. The urease activity of the 0-25 cm layer in the F two columns is obviously higher than that of the 35-45 cm layer (P is less than 0.01), which shows that the enzyme activity in the red mud can be obviously improved by adding the bagasse and the bran, and the nitrogen circulation is improved. The activity of the cellulase in the E column is lower than that of the cellulase in the F column, which shows that the activity of the cellulase in the red mud can be improved by adding the penicillium oxalicum, so that the carbon circulation is improved. The activity of cellulase in a layer of 0-5 cm in the F column is obviously higher than that of cellulase in a layer of 15-25 cm, which shows that the action of the penicillium oxalicum on the surface layer is larger. In the F column, the enzyme activity at day 30 is higher, which indicates that the survival state and the quantity of the penicillium oxalicum reach the highest at day 30.

Example 6

Analysis of the change in alkaline cations in the red mud obtained in example 2:

sampling red mud at the depth of 0cm, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column on the 30 th day, air-drying the samples to constant weight, weighing 5.0g, adding 25mL of deionized water, shaking up, taking the supernatant, and measuring alkaline cations Na +, K +, Ca2+ and Mg2+ in the red mud by using inductively coupled plasma atomic emission spectrometry (ICP-AES).

The water soluble alkaline cations at day 30 were further analyzed because the red mud column was the least alkaline at day 30. The cation content of the F column is obviously higher than that of the E column, and the Na + content of the F column is higher than that of the E column although the pH value of the F column is lower than that of the E column, so that the acidic substances metabolized by the penicillium oxalicum can promote the dissolution of Na +. The Na + content in the F and E columns accounted for 86% and 90% of the total alkali cations, respectively, indicating that Na + predominated in the basic cations in the red mud of the column. The Na + content of the surface layer of the F column is 5069.1mg/kg at most, the deeper the depth is, the lower the ion content is, and the Na + content of the 45cm layer is 998.25 mg/kg; the Na + content of the surface layer of the E column is 103.26mg/kg at most, and the ion content is lower towards the lower part of the column, and the Na + content is 65.26mg/kg at a 45cm layer. The content of Ca2+ in the F column is reduced from 263.66mg/kg of the surface layer to 72.28mg/kg of the 45cm layer of the soil column; the content of Ca2+ in the E column is low, the surface layer is 31.24mg/kg, and the Ca2+ can not be basically detected in a layer of 35-45 cm. In the F column, the content of K + at 0-25 cm is higher than that of a layer of 35-45 cm, particularly the content of a surface layer reaches 316.01mg/kg, and the content difference between the K + at 0-25 cm and the K + at 35-45 cm in the E column is not obvious; in the F column, the Mg2+ content is reduced from 35.87Mg/kg at the surface layer to 2.61Mg/kg at the 45cm layer of the column, while in the E column, the Mg2+ content is very low and cannot be basically detected at the 35 cm-45 cm layer. The addition of the penicillium oxalicum can obviously improve the nutrient elements in the red mud, and has obvious effect on improving the red mud matrix.

Example 7

Analysis of the change in the microscopic morphology of the red mud particles in the earth pillar in example 2:

sampling red mud at the depth of 0cm on the surface layers of the E column and the F column on the 30 th day, naturally drying the samples, slightly grinding the samples, sieving the samples with a 300-mesh sieve, and measuring the change condition of the red mud fine particles in the two columns by using electron microscope Scanning (SEM).

In the red mud of the E column without the penicillium oxalicum, more fine particles with the particle size of 0.1-0.5 mu m are distributed on the aggregate with the particle size of 2-5 mu m, the crystallinity is poor, and the particle distribution is relatively dispersed and disordered. Compared with the red mud in the E column, the red mud in the F column has the advantages of obviously reduced fine particles, improved crystallinity to a certain extent, obviously increased large particles and better agglomeration structure. Compared with the E column, the Na ion content of the F column is reduced to 0.24% from 1.47%, and the Ca ion content is increased to 24.21% from 6.65%, which further indicates that the penicillium oxalicum can promote the alkalinity reduction of the red mud and improve the red mud agglomeration structure.

Claims (6)

1. A method for reducing alkalinity of Bayer process red mud by using penicillium oxalicum is characterized by comprising the following steps:

(1) naturally air-drying and sieving the red mud, dividing the obtained red mud into a first part and a second part, adding the pretreated bagasse and bran into the first part of the red mud, and uniformly mixing to obtain the red mud added with the biomass;

(2) filling the soil column, filling quartz sand at the bottom of the soil column, using the second part of red mud as a middle layer, filling the biomass-added red mud obtained in the step (1) at the top, and inoculating the penicillium oxalicum strain into the first part of red mud to obtain the filled soil column;

(3) filling water into the filled soil column in the step (2) from bottom to top, keeping the water content at 60% -80%, cultivating at room temperature, reducing the alkalinity of the red mud, increasing the content of organic matters in the red mud, and promoting the formation of red mud aggregates;

the microbial serial number of the penicillium oxalicum is as follows: MF 802280.

2. The method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum according to claim 1, wherein in the step (1), the mass percentages of the bagasse, the bran and the first part of red mud are (6-18%): (5-15%): (67-89%).

3. The method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum according to claim 1, wherein in the step (1), the pretreatment is one of hydrothermal treatment, sulfuric acid treatment, calcium oxide treatment and hydrogen peroxide treatment.

4. The method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum according to claim 3, wherein the pretreatment adopts hydrothermal treatment, and comprises the following specific steps:

(a) drying bagasse and bran, then crushing the bagasse and bran by using a crusher, and sieving the crushed bagasse and bran by using a sieve of 60-80 meshes;

(b) adding the sieved bagasse, bran and water into a beaker, placing the beaker in a high-pressure steam sterilization pot, heating to 150-180 ℃, keeping the pressure at 4.0-6.0 MPa, treating for 5-10 min, and finally blasting the biomass by suddenly reducing the pressure to obtain the pretreated bagasse and bran.

5. The method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum according to claim 1, wherein in the step (2), the concrete steps of filling the soil column are as follows:

1) establishing an indoor soil column device model, fixing a transparent column on an iron frame, wherein the inner diameter of the cross section of the soil column is 6.3cm, the outer diameter of the cross section of the soil column is 7.0cm, small holes with plugs are arranged on the column body every 10cm of depth, a leaching device is arranged above the soil column to simulate the rain weather of a red mud storage yard, the tip of the lowest end of the soil column is connected with a rubber tube, and the rubber tube is connected into a conical bottle to contain percolate;

2) filling the soil column, filling quartz sand with the thickness of 6cm below the depth of 65cm at the bottom of the soil column, filling a second part of red mud in the depth of 25-65 cm of the soil column, and filling the red mud added with the biomass obtained in the step (1) in the depth of 0-25 cm of the soil column;

3) two soil columns are respectively filled and named as an E column and an F column, the F column is periodically inoculated with penicillium oxalicum agent, and the E column is used as a control and is not inoculated with the agent.

6. The method for reducing the alkalinity of Bayer process red mud by using penicillium oxalicum according to any one of claims 1 to 5, wherein the preparation process of the penicillium oxalicum agent is as follows:

a) preparing a glucose liquid culture medium, filling 100mL of the culture medium into a 250mL conical flask, and performing high-pressure steam sterilization;

b) inoculating penicillium oxalicum to a sterilized and cooled culture medium, and culturing at the temperature of 25-30 ℃ and at the speed of 160-180 r/min for 72-96 h;

c) inoculating the cultured penicillium oxalicum agent into an F column.

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