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 oxalate, and belongs to the technical field of microorganism application. In the second part, the pretreated bagasse and bran are then added to the first part of the red mud, and mixed evenly to obtain the biomass-added red mud; (2) soil column filling is carried out, and the quartz sand is filled in the soil At the bottom of the column, the second part of the red mud is used as the middle layer, the red mud with biomass added is packed on the top, and the Penicillium oxalic acid species is inoculated into the second part of the red mud; (3) Into the packed soil column from the bottom Fill up with water, keep the water content at 60% to 80%, and cultivate at room temperature to reduce the alkalinity of red mud. The method of combining biomass and Penicillium oxalate can reduce the pH value of red mud to 6.66. The method uses a wide range of raw materials, has low cost, and has no secondary pollution in microbial restoration. The effect is remarkable and can be applied to red mud. mud yard.

Description

A kind of method that utilizes Penicillium oxalate to reduce the alkalinity of Bayer process red mud

technical field

The invention belongs to the technical field of microorganism application, and in particular relates to a method for reducing the alkalinity of Bayer process red mud by using Penicillium oxalate.

Background technique

Bayer process red mud is a highly alkaline solid waste discharged in the alumina industrial production process. Every 1 ton of alumina produced produces 1.5-2.0 tons of red mud, which is difficult to comprehensively utilize. The discharged red mud is mainly stored. In 2017, the world's accumulated red mud to be treated was about 4 billion tons, and it is increasing at an annual rate of 170 million tons. The environmental safety problem of the red mud yard is becoming more and more serious, and the problem of how to effectively dispose and utilize the red mud is imminent. At home and abroad, attempts have been made to carry out ecological restoration of red mud yard, but due to the strong alkalinity of red mud, high salt content, and lack of nutrients, it is difficult for plants to grow. Professor Xue Shengguo from the Environmental and Ecological Engineering Team of Central South University proposed the research idea of red mud soilization. It is planned to convert red mud into a soil-like matrix through physical-chemical-biological methods, so that the improved red mud has the basic conditions for plant growth. Realize the harmless disposal of red mud.

Microorganisms reproduce quickly and in large numbers, can decompose organic matter, release nutrients, improve soil structure, and increase soil fertility; some special functional strains can metabolize to produce organic acids, reduce the alkalinity of red mud, and provide suitable growth conditions for plants , to promote the progress of red mud soilization. In recent years, studies have found that Acidobacteriaceae, Nitrosomonadaceae and Caulobacteraceae can grow in unrestored red mud environment, providing important indicators for the ecological restoration of red mud yard.

The traditional red mud matrix improvement methods include physical method and chemical method, but these two methods are expensive, the red mud yard covers a large area, and the consumption of chemical reagent spraying is large, so these methods are difficult to apply in practice. . Microorganisms have the characteristics of fast reproduction, low application cost, and no secondary pollution, and have broad application prospects. However, there are relatively few studies on red mud remediation using biological methods. Therefore, there is an urgent need in the field to use a low-cost biological method to actually remediate red mud, so as to provide technical support for the implementation of red mud soilization.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the object of the present invention is to provide a simple, cost-effective and environmentally friendly method for reducing the alkalinity of Bayer process red mud by utilizing Penicillium oxalate, so as to solve the environmental safety of a large amount of Bayer process red mud storage. question.

In order to realize the above-mentioned technical purpose, the present invention provides the following technical solutions:

The invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing Penicillium oxalate, comprising the following steps:

(1) The red mud is naturally air-dried and sieved, and the obtained red mud is divided into a first part and a second part, and then the pretreated bagasse and bran are added to the first part of the red mud, and mixed evenly, obtain biomass-added red mud;

(2) carrying out soil column filling, filling quartz sand at the bottom of the soil column, the second part of the red mud as the middle layer, filling the red mud of the gained biomass in step (1) on the top, and inoculating the Penicillium oxalicum species into the In the first part of the red mud, a packed soil column is obtained;

(3) filling the soil column filled in the step (2) with water from bottom to top, keeping the moisture content at 60% to 80%, and cultivating at room temperature, reducing the alkalinity of red mud, and increasing the content of organic matter in the red mud, Promote the formation of red mud aggregates.

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

Preferably, in 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 the specific steps are:

(a) Dry the bagasse and bran, then pulverize them with a pulverizer and pass through a 60-80 mesh sieve;

(b) Add the sieved bagasse, bran and water into a beaker, place it in a high-pressure steam sterilizer, heat it to 150~180°C, keep the pressure at 4.0~6.0MPa, and treat it for 5~10min. The biomass is blasted by reducing the pressure to obtain pretreated bagasse and bran.

As preferably, in step (2), the concrete steps of soil column filling are:

1) Build an indoor soil column device model, fix the transparent column on the iron frame, the inner diameter of the cross section of the soil column is 6.3cm, and the outer diameter is 7.0cm. A leaching device is added above the column to simulate the rainy weather of the red mud yard. A rubber tube is connected to the tip of the bottom end of the soil column, and the rubber tube is connected to the conical flask to collect the leachate;

2) Filling the soil column, filling the bottom of the soil column (below 65cm depth) with 6cm thick quartz sand, filling the second part of the red mud at the depth of the soil column 25~65cm, and then adding the biomass-added red mud obtained in step (1). The mud is filled in the soil column at a depth of 0~25cm;

3) Fill two soil columns respectively, named as E column and F column, inoculate the F column with Penicillium oxalate regularly, and E column as a control without inoculating the bacterial agent.

Further, the preparation process of described Penicillium oxalate agent is:

a) Prepare glucose liquid medium, take 100mL and put it in a 250mL conical flask, and carry out high pressure steam sterilization;

b) Inoculate Penicillium oxalate into the sterilized and cooled medium, and cultivate at 25~30℃, 160~180r/min for 72~96h;

c) Inoculate the cultured Penicillium oxalate agent into the F column.

In the previous experiments, the inventor team screened out the microbial strain Penicillium oxalicum with good alkali resistance and high acid production performance from the red mud yard. It has a significant effect, and as an important cellulase-producing microorganism, it can degrade cellulose and play an important role in the carbon cycle.

The principle of the invention: the Bayer process red mud has strong alkalinity, lack of nutrients and loose structure, and it is difficult for plants to grow on the original red mud yard. In the present invention, sugarcane bagasse and bran treated with hydrothermal treatment are added to the Bayer process red mud as the carbon source and nitrogen source required for the survival of microorganisms, and then the Penicillium oxalate agent is applied to the red mud, and its metabolism produces a large amount of organic Acid, can effectively reduce the alkalinity of red mud; Penicillium oxalate can decompose biomass by using bagasse and bran as carbon and nitrogen sources, and Penicillium oxalate will also secrete cellulase to increase the content of organic matter in red mud; The physical entanglement of mold mycelium can further promote the formation of red mud aggregates.

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

The invention provides a method for reducing the alkalinity of Bayer process red mud by using Penicillium oxalate, and the method of combining biomass and Penicillium oxalate can reduce the pH value of the red mud to 6.66, and improve the organic matter in the red mud. content, promoting the formation of aggregates in red mud. The invention uses a wide range of raw materials, has low cost, and has no secondary pollution for microbial remediation, and has a remarkable effect, can be applied to a red mud yard, and can effectively solve the problem of environmental pollution caused by the red mud yard.

Description of drawings

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

Figure 2 shows the soil column model diagram. (F: Red mud column with Penicillium oxalate added; E: Red mud column without Penicillium oxalate)

Figure 3 is a graph showing the changes in pH, EC (conductivity) and total alkali of red mud over time.

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

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

Figure 6 is a graph of changes in the content of alkaline cations (Na+, Ca2+, K+, Mg2+) in red mud on the 30th day after repair.

Figure 7 is an SEM image of red mud.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, ordinary skills in the art All other embodiments obtained by personnel without creative work fall within the protection scope of the present invention.

The present invention will be further described below in conjunction with specific embodiments and accompanying drawings:

Example 1

Biomass pretreatment can adopt the following four methods. By comparing different biomass pretreatment methods, the optimal conditions for acid production by Penicillium oxalicum are determined, and finally the optimal pretreatment method is selected:

(1) Hydrothermal treatment

Use a pulverizer to pulverize the bagasse and bran, pass through a 60-mesh sieve (pore size 0.25mm), then put the bagasse, bran and water in a beaker at a solid-liquid ratio of 1:10, and place it in a high-pressure steam sterilizer. Heating to 180 ℃, maintaining the pressure of about 4.0MPa for 5min, and finally depressurizing the biomass to blast.

(2) Sulfuric acid treatment

Pulverize the bagasse and bran, pass through a 60-mesh sieve (pore size 0.25mm), weigh an appropriate amount of bagasse and bran, add 1% (w/w) H2SO4 solution at a solid-to-liquid ratio of 1:10, stir evenly, and steam under high pressure. Treat at 121°C for 1h.

(3) Calcium oxide treatment

The lime (the main component is calcium oxide) is slurried (to generate calcium hydroxide), and then each gram of biomass is mixed with 0.075g of calcium hydroxide and 5g of water, and heated at 120 ° C for 4 hours.

(4) Hydrogen peroxide treatment

Weigh 10.0g bagasse and bran into a 250mL conical flask, add 5% (w/w) H2O2 solution at a solid-to-liquid ratio of 1:10, stir evenly, and place it in a water bath constant temperature shaking box for 24h at 30°C.

The treated biomass and distilled water were prepared into a culture solution at a ratio of 1:5, and then inoculated with Penicillium oxalate in the liquid medium. At the same time, a blank control group was set up, placed at 28°C, and cultured on a 160r/min shaker for 9 days. pH.

The results in Figure 1 show that the effects of hydrothermal treatment and H2SO4 treatment are significantly higher than those of CaO treatment and H2O2 treatment (P<0.05), and there is no significant difference between hydrothermal treatment and H2SO4 treatment, but compared with the two, H2SO4 treatment requires Adding chemical reagents, if used in the restoration of red mud, will introduce exogenous ions, so the hydrothermal treatment method is adopted.

Example 2

The invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing Penicillium oxalate, comprising the following steps:

(1) The red mud is naturally air-dried and sieved, and the obtained red mud is divided into the first part and the second part, and then the bagasse and bran after the hydrothermal treatment are added to the first part of the red mud, bagasse, The mass percentage of the bran and the first part of the red mud is 6%: 5%: 89%, and mixed evenly to obtain the red mud added with biomass;

(2) Fill the soil column. The soil column model is shown in Figure 2. The 0-25cm layer of the E column and the F column is the red mud with biomass added, the 25-65cm depth is the second part of the red mud, and the bottom of the column ( 65cm or less) is filled with quartz sand with a depth of 6cm to prevent the loss of red mud with the outflow of leachate. After the E column and F column are filled, they are leached from time to time to simulate the rainy weather in the red mud yard. Inoculate Penicillium oxalate every 3 days;

The preparation process of penicillium oxalate agent is as follows:

a) Prepare a glucose liquid medium, take 100 mL of it and put it in a 250 mL conical flask, and sterilize it by autoclaving (21°C, 20min);

b) Inoculate Penicillium oxalate into the sterilized and cooled medium, and cultivate at 28°C and 180r/min for 72h;

c) Inoculate the cultured Penicillium oxalate agent into the F column;

(3) Fill the packed soil column with water from bottom to top, keep the moisture content at 60%~80%, cultivate at room temperature, reduce the alkalinity of red mud, increase the content of organic matter in red mud, and promote red mud agglomeration Formation.

Example 3

The invention provides a method for reducing the alkalinity of Bayer process red mud by utilizing Penicillium oxalate, comprising the following steps:

(1) The red mud is naturally air-dried and sieved, and the obtained red mud is divided into the first part and the second part, and then the bagasse and bran after the hydrothermal treatment are added to the first part of the red mud, bagasse, The mass percentage of the bran and the first part of the red mud is 18%: 15%: 67%, and mixed evenly to obtain the red mud added with biomass;

(2) Fill the soil column. The soil column model is shown in Figure 2. The 0-25cm layer of the E column and the F column is the red mud with biomass added, the 25-65cm depth is the second part of the red mud, and the bottom of the column ( 65cm or less) is filled with quartz sand with a depth of 6cm to prevent the loss of red mud with the outflow of leachate. After the E column and F column are filled, they are leached from time to time to simulate the rainy weather in the red mud yard. Inoculate Penicillium oxalate every 3 days;

(3) Fill the packed soil column with water from bottom to top, keep the moisture content at 60%~80%, cultivate at room temperature, reduce the alkalinity of red mud, increase the content of organic matter in red mud, and promote red mud agglomeration Formation.

Example 4

Analyze the variation of pH, EC, total alkali (Total alkalinity) in the red mud gained in Example 2:

On the 6th, 12th, 18th, 24th, and 30th days, the red mud at the depths of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column was sampled. After the samples were air-dried to constant weight, 5.0 g red mud was placed in a centrifuge tube, then 25 mL of deionized water (1:5) was added, shaken well, and after standing for 30 min, the pH and EC of the supernatant were measured. Draw 10mL of red mud leachate with a soil-water ratio of 1:5, put it into a 100mL conical flask, measure the CO32- (HCO3-) content in the sample by bromophenol blue indicator titration, and add bromophenol blue indicator to the supernatant , titrated with H2SO4 standard solution to colorless (pH 4.5), and obtained CO32- content and HCO3- content by calculation. The total alkalinity in red mud is the sum of CO32-, HCO3-, Al(OH)4- and OH- content, where Al(OH)4- content was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES, Optima 5300DV, American Perkin Elmer Company) determined the Al content in the supernatant and calculated it.

The results are shown in Figure 3. In the F column, the pH of the red mud changed with time. On the 18th day, the pH of the F column increased slightly, probably because the acidic substances metabolized by Penicillium oxalicum neutralized a large amount of Free base, leading to dissolution of bound base in red mud. After the 24th day, the pH of the F column was maintained at around 7, and the pH on the 30th day was significantly different from that on the 6th day (P<0.05). In the E column, the pH of the red mud was basically unchanged, and its pH value was maintained at around 9, and there was no significant difference within 30 days. On the 30th day, the pH of column F was significantly lower than that of column E (P<0.05), indicating that Penicillium oxalicum could effectively reduce the pH of red mud, and the repair effect was better. In the E column, the EC decreased with time, probably due to the migration of basic ions in the column due to leaching. In the F column, the EC increased with time, probably because the acidic substances produced by Penicillium oxalicum dissolved the alkaline ions in the red mud. The EC on day 24 was significantly higher than that on day 30 in both columns, probably mainly due to leaching. The total alkali of column F was significantly lower than that of column E (P<0.05), indicating that the acidic substances produced by Penicillium oxalicum had a great influence on the alkalinity of red mud.

In the F column, the pH of the red mud in the 0-5cm layer was significantly lower than that in the E column (P<0.05), indicating that Penicillium oxalicum had greater activity at the surface depth and had a more obvious effect. The EC value of red mud in the F column was significantly higher than that in the E column in the 0-5 cm layer, indicating that Penicillium oxalicum can dissolve a large amount of bound alkali in the red mud, which increases the content of alkaline ions. In the 35-45cm layer, the pH of the red mud in the F column was significantly lower than that in the E column (P<0.05), indicating that the acidic substances metabolized by Penicillium oxalicum could migrate to the lower layer and the alkaline substances in the red mud under the action of leaching. reaction. In the F column, the total alkali content of red mud is lower than that of the E column, and the total alkali content of the red mud in the unmodified 35-45 cm layer in the F column is lower than that in the E column, indicating that the organic acids metabolized by Penicillium oxalicum can be significantly reduced. The alkalinity of red mud has a good control effect on the alkalinity of red mud.

Example 5

Changes in organic matter, urease and cellulase in the red mud obtained in Example 2 were analyzed:

(1) Determination of organic matter content

On the 6th, 12th, 18th, 24th and 30th days, the red mud at the depths of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column was sampled, and the samples were air-dried to constant weight and then ground, and accurately weighed. Put 1.000g of red mud that has passed through a 100-mesh sieve into a 50mL beaker, add 3mL of water, shake well, add 10mL of 1mol/L (1/6 K2Cr2O7) solution, then add 10mL of concentrated sulfuric acid, shake continuously, leave for 20min, add 10mL of water , shake well and let stand overnight. Pipette 3mL of the supernatant into a 10mL colorimetric tube, add water to the mark, shake well, measure at a wavelength of 590nm, and calculate the organic matter content according to the standard curve.

(2) Determination of urease (Urease) content

On the 6th, 12th, 18th, 24th and 30th days, the red mud at the depths of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column was sampled. The samples were dried to constant weight and weighed 5.0g. The red mud sample was placed in a 50 mL conical flask, 1 mL of toluene was added, and the mixture was shaken evenly. After 15 minutes, 10 mL of 10% urea solution and 20 mL of pH 6.7 citrate buffer solution were added. After culturing, filter, add 1 mL of filtrate into a 50 mL volumetric flask, add 4 mL of sodium phenolate solution and 3 mL of sodium hypochlorite solution, and shake up while adding. After 20 minutes, the color develops and the volume is fixed. Within 1h, the spectrophotometer was colorimetric at 578nm wavelength. (The blue color of indophenol remains stable within 1h)

(3) Determination of Cellulolytic enzyme content

On the 6th, 12th, 18th, 24th and 30th days, the red mud at the depths of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column was sampled, and the samples were dried to constant weight and weighed 10.0g red mud. Put the mud into a 50mL conical flask, add 1.5ml toluene, shake well and leave for 15min, add 5ml 1% carboxymethyl cellulose solution and 5ml pH5.5 acetate buffer, and place the flask at 37°C at a constant temperature Incubate for 72h. After the incubation, filter and take 1 mL of filtrate, and then draw a standard curve colorimetric method for colorimetric determination. (In order to eliminate the errors caused by the original sucrose and glucose in the soil, each soil sample needs to be a matrix-free control, and the whole experiment needs to be a soil-free control; if the sample absorbance value exceeds the maximum value of the standard curve, the fractionation multiple should be increased. Or reduce the soil samples for cultivation.)

The experimental results are shown in Figure 4. With the increase of time, the content of organic matter in the two columns increased slightly. On the 12th day, the content of organic matter in the column was the highest and then decreased. The organic matter content of the 0-25cm layer in the two columns was significantly higher than that of the 35-45cm layer (P<0.01). It can be seen from Figure 5 that the urease activity in the E and F columns increased with time, while the urease activity in the E column was not significantly different from the F column, indicating that Penicillium oxalicum had little effect on the urease activity. The urease activity in the 0-25cm layer in the two columns E and F was significantly higher than that in the 35-45cm layer (P<0.01), indicating that the addition of bagasse and bran could significantly improve the enzyme activity in red mud and improve the nitrogen cycle. The activity of cellulase in column E was lower than that in column F, indicating that adding Penicillium oxalicum could improve the activity of cellulase in red mud, thereby increasing the carbon cycle. The cellulase activity in the 0-5 cm layer in the F column was significantly higher than that in the 15-25 cm layer, indicating that Penicillium oxalicum played a greater role in the surface layer. In the F column, the enzyme activity was higher on the 30th day, indicating that the survival state and number of Penicillium oxalicum reached the highest on the 30th day.

Example 6

Changes of basic cations in the red mud obtained in Example 2 were analyzed:

On the 30th day, the red mud at the depths of 0, 5cm, 15cm, 25cm, 35cm and 45cm of the E column and the F column was sampled. After the samples were air-dried to a constant weight, 5.0 g was weighed, 25 mL of deionized water was added, and the samples were shaken well. , the supernatant was taken, and the basic cations Na+, K+, Ca2+, Mg2+ in red mud were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

Since the red mud column had the lowest alkalinity on the 30th day, the water-soluble alkaline cations on the 30th day were further analyzed. It was found that the cation content of the F column was significantly higher than that of the E column. Although the pH of the F column was lower than that of the E column, its Na+ content was higher than that of the E column, indicating that the acidic substances metabolized by Penicillium oxalicum could promote the dissolution of Na+. The Na+ content in the F column and E column accounts for 86% and 90% of the total basic cations, respectively, indicating that Na+ dominates the basic cations in the red mud of the soil column. The Na+ content in the surface layer of the F-column is up to 5069.1 mg/kg, and the deeper the depth, the lower the ion content. The Na+ content in the 45cm layer is 998.25 mg/kg; the Na+ content in the E-column surface is up to 103.26 mg/kg, and the more In the lower part of the soil column, the lower the ion content, the Na+ content in the 45cm layer is 65.26mg/kg. The Ca2+ content in column F decreased from 263.66 mg/kg in the surface layer to 72.28 mg/kg in the 45 cm layer of the soil column; the content of Ca2+ in the E column was lower, 31.24 mg/kg in the surface layer, which was basically undetectable in the 35-45 cm layer. In column F, the content of K+ at 0-25 cm is higher than that at 35-45 cm, especially the surface layer content reaches 316.01 mg/kg, while the content of K+ in column E is not significantly different between 0-25 cm and 35-45 cm; In the F column, the Mg2+ content decreased from 35.87 mg/kg in the surface layer to 2.61 mg/kg in the 45 cm layer of the soil column, while the Mg2+ content in the E column was very low and could not be detected in the 35 cm-45 cm layer. It shows that the addition of Penicillium oxalate can significantly increase the nutrient elements in red mud, and has a significant effect on the improvement of red mud matrix.

Example 7

Analysis of the change diagram of the microscopic morphology of the red mud particles in the soil column in Example 2:

On the 30th day, the red mud at the surface (0cm) depth of the E column and the F column was sampled. The samples were air-dried and ground slightly, passed through a 300-mesh sieve, and the fine particles of red mud in the two columns were determined by scanning electron microscope (SEM). changes.

In the red mud of the E-column without Penicillium oxalate added, many fine particles of 0.1-0.5 μm are distributed on the aggregates of 2-5 μm, the crystallinity is poor, and the particle distribution is relatively scattered and disordered. Compared with the red mud in the E column, the fine particles of the red mud in the F column are significantly reduced, the crystallinity is improved to a certain extent, the large particles are increased significantly, and the agglomeration structure is better. Compared with the E column, the Na ion content of the F column decreased from 1.47% to 0.24%, and the Ca ion content increased from 6.65% to 24.21%, which further indicated that Penicillium oxalicum could promote the reduction of red mud alkalinity and improve red mud agglomeration. structure.

Claims (6)

1. a method utilizing Penicillium oxalate to reduce the alkalinity of Bayer process red mud, is characterized in that, comprises the following steps: (1) The red mud is naturally air-dried and sieved, and the obtained red mud is divided into a first part and a second part, and then the pretreated bagasse and bran are added to the first part of the red mud, and mixed evenly, obtain biomass-added red mud; (2) carrying out soil column filling, filling quartz sand at the bottom of the soil column, the second part of the red mud as the middle layer, filling the red mud of the gained biomass in step (1) on the top, and inoculating the Penicillium oxalicum species into the In the first part of the red mud, a packed soil column is obtained; (3) filling the soil column filled in the step (2) with water from bottom to top, keeping the moisture content at 60% to 80%, and cultivating at room temperature, reducing the alkalinity of red mud, and increasing the content of organic matter in the red mud, Promote the formation of red mud aggregates; The microorganism serial number of the described Penicillium oxalicum is: MF802280. 2. utilize Penicillium oxalate according to claim 1 to reduce the method for Bayer process red mud alkalinity, it is characterized in that, in step (1), the mass percent of described bagasse, bran and the first part of red mud is (6. ~18%): (5~15%): (67~89%). 3. the method utilizing Penicillium oxalate to reduce the alkalinity of Bayer process red mud according to claim 1, is characterized in that, in step (1), described pretreatment is hydrothermal treatment, sulfuric acid treatment, calcium oxide treatment and hydrogen peroxide treatment one of the. 4. the method utilizing Penicillium oxalate to reduce the alkalinity of Bayer process red mud according to claim 3, is characterized in that, described pretreatment adopts hydrothermal treatment, and concrete steps are: (a) Dry the bagasse and bran, then pulverize them with a pulverizer and pass through a 60-80 mesh sieve; (b) Add the sieved bagasse, bran and water into a beaker, place it in a high-pressure steam sterilizer, heat it to 150~180°C, keep the pressure at 4.0~6.0MPa, and treat it for 5~10min. The biomass is blasted by reducing the pressure to obtain pretreated bagasse and bran. 5. the method utilizing Penicillium oxalate to reduce the alkalinity of Bayer process red mud according to claim 1 is characterized in that, in step (2), the concrete steps of soil column packing are: 1) Build an indoor soil column device model, fix the transparent column on the iron frame, the inner diameter of the cross section of the soil column is 6.3cm, and the outer diameter is 7.0cm. A leaching device is added above the column to simulate the rainy weather of the red mud yard. A rubber tube is connected to the tip of the bottom end of the soil column, and the rubber tube is connected to the conical flask to collect the leachate; 2) Carry out soil column filling, below the depth of 65cm at the bottom of the soil column, fill with 6cm thick quartz sand, fill the second part of red mud at the depth of 25~65cm of the soil column, and then fill the red mud obtained in step (1) with the addition of biomass. In the soil column 0~25cm depth; 3) Fill two soil columns respectively, named as E column and F column, inoculate the F column with Penicillium oxalate regularly, and E column as a control without inoculating the bacterial agent. 6. according to the described method of utilizing Penicillium oxalate to reduce the alkalinity of Bayer process red mud according to any one of claims 1～5, it is characterized in that, the preparation process of described Penicillium oxalate agent is: a) Prepare glucose liquid medium, take 100mL and put it in a 250mL conical flask, and carry out high pressure steam sterilization; b) Inoculate Penicillium oxalate into the sterilized and cooled medium, and cultivate at 25~30℃, 160~180r/min for 72~96h; c) Inoculate the cultured Penicillium oxalate agent into the F column.

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