Method for enhancing adsorption performance of wheat straw carbon by utilizing filamentous fungus fermentation technology and application
Technical Field
The invention relates to the technical field of environmental protection, in particular to a method for enhancing the adsorption performance of wheat straw carbon by utilizing a filamentous fungus fermentation technology and application thereof.
Background
The waste biomass comprises crop straws, livestock and poultry dry manure, forestry waste, perishable garbage and the like. The amount of waste biomass in China is large and wide, and the annual crop straw production amount in China is 8.65 hundred million tons according to the 'second national pollution source census bulletin'. Agricultural and forestry waste biomass including wheat straws is always considered as the best raw material for resource conversion due to the characteristics of wide sources, low raw material price, reproducibility, sustainability, diversity of utilization modes and the like. As a big country of agriculture, the conversion and the recycling of crop straws have very important significance for solving the urgent problems of resource, environment, rural development and the like.
Pyrolysis and carbonization are one of the effective utilization ways of the straws. At present, most researches on direct carbonization of straws cause loss of straw resources to a certain extent, and the obtained biomass charcoal material has limited adsorption capacity when used as an adsorbent. In order to enhance the adsorption capacity of the biomass charcoal to better remove pollutants, many researchers can modify biomass charcoal materials, the modification methods of the biomass charcoal are not uniform and have certain cost, and the modification effect is greatly different due to different properties and application environments of raw materials. Straw is mainly composed of cellulose, hemicellulose and lignin, and a plurality of microorganisms existing in the environment have the capacity of degrading lignocellulose. Through microbial fermentation, the straw can realize conversion and structural change to a certain degree. The straw residue after microbial fermentation is composed of waste biomass and waste microbial cells, and contains a large amount of proteins, lipids and other carbohydrates as well as trace elements such as phosphorus (P), calcium (Ca) and iron (Fe). The incineration or disposal of the fermentation residues can cause great resource waste and environmental pollution. The potential application of biomass charcoal derived from fermentation waste is yet to be explored.
Disclosure of Invention
The invention provides a method for enhancing the adsorption performance of wheat straw charcoal by utilizing a filamentous fungus fermentation technology and application thereof, aiming at the application problems of low adsorption performance and high modification cost of the biomass charcoal from wheat straw.
The invention utilizes dominant fungi with lignocellulose degradation capability to degrade straws, achieves the purpose of loosening the microstructure of natural straws, then carries out pyrolysis carbonization on the fermented straws, and uses the product for adsorbing and removing typical water pollutants such as dye, heavy metal and the like. The adsorption performance of the straw carbon is enhanced, and a new idea is provided for recycling the fermentation residues of the straws.
In order to achieve the purpose, the invention adopts the following technical means:
a method for strengthening the adsorption performance of wheat straw charcoal by utilizing a filamentous fungus fermentation technology is characterized by comprising the following steps:
1) taking mature spore suspension of filamentous fungus trichoderma asperellum T-1, inoculating the mature spore suspension into a sterilized wheat straw solid-state fermentation culture medium, uniformly stirring, and then culturing at constant temperature to finish wheat straw solid-state fermentation based on the trichoderma asperellum T-1, so as to obtain a wheat straw fermentation system;
2) adding a citric acid buffer solution into the wheat straw fermentation system in the step 1), oscillating at constant temperature by using a shaking table, leaching and cleaning, and filtering or centrifuging by using filter paper to obtain a wheat straw fermentation residue;
3) drying the wheat straw fermentation residues obtained in the step 2) in an oven, uniformly grinding, putting the straws into a porcelain boat, putting the porcelain boat in a tubular furnace for pyrolysis and carbonization, and keeping nitrogen atmosphere during the pyrolysis and carbonization, thereby finally obtaining the biomass charcoal with high adsorption performance.
In step 1), the trichoderma asperellum T-1 is a prior art, has been disclosed in chinese patent with application publication No. CN104450530A (application No. 201410578593.X), has been deposited in the common microorganism center of the china committee for culture collection of microorganisms at 9-24 months in 2014, and has a biological preservation number of: CGMCC No. 9722;
the inoculation concentration of the spore suspension of the trichoderma asperellum T-1 is 106~107Spores/g wheat straw;
in the step 1), the wheat straw solid-state fermentation culture medium is prepared from a Mandel culture solution and wheat straws, wherein the ratio of the use amount of the Mandel culture solution to the use amount of the wheat straws is 3-4 mL: 1g (volume: mass).
The Mandel culture solution is counted by 1L and prepared from the following raw materials by weight:
the pH of the Mandel culture solution is 5-6.
In the step 1), the conditions of constant temperature culture are as follows: culturing at constant temperature of 25-30 ℃ for 4-6 days.
In the step 2), the pH value of the citric acid buffer solution is 4-5. The dosage ratio of the citric acid buffer solution to the wheat straw fermentation system is 12-20 g: 1mL (volume: mass).
In the step 2), the constant temperature oscillation condition of the shaking table is as follows: the temperature is 25-30 ℃, and the rotating speed of the shaking table is 150-200 r/min.
In the step 3), the drying conditions are as follows: the temperature is 50-80 ℃, and the time is 48-96 hours.
In the step 3), the pyrolysis carbonization conditions are as follows: the pyrolysis temperature is 500-700 ℃, and the pyrolysis carbonization time is 100-180 min.
In the step 3), the nitrogen input flow rate of the nitrogen atmosphere is kept to be 0.2-0.6L/min.
The biomass charcoal prepared by the method is applied to adsorbing dyes and heavy metals in water or soil.
Specifically, a method for enhancing the adsorption performance of wheat straw charcoal by utilizing a filamentous fungus fermentation technology comprises the following steps:
(1) inoculating trichoderma asperellum T-1 on a potato glucose agar culture medium in a streaking manner, culturing at the constant temperature of 28 ℃ for 5-7 days, washing spores by using a sterilized 0.1% (v/v) Tween 80 solution, filtering the spores by using sterilized three-layer mirror wiping paper, collecting the spores in a sterilized 50mL centrifuge tube, centrifugally collecting spore precipitates, adding 10mL of 0.1% Tween 80 to resuspend and clean the spore precipitates once, centrifugally removing supernatant, and adding 5mL of sterile water to resuspend the spores to prepare spore suspension;
(2) preparing a solid fermentation culture medium of wheat straws: the volume of the Mandel culture solution and the wheat straw: mixing the components in a mass ratio of 3: 1-4: 1 (mass: volume), and sterilizing at 121 ℃ for 30min under high temperature and high pressure;
the Mandel culture solution is counted by 1L and prepared from the following raw materials by weight:
the pH of the Mandel broth was 5.5.
(3) The spore suspension in step 1 is diluted 106~107Inoculating the concentration of each spore/g of wheat straw into a wheat straw solid fermentation culture medium, and standing and fermenting for 4-6 days at a constant temperature of 25-30 ℃.
(4) Citric acid buffer at pH 4.8 was mixed at 12: 1-20: 1 (volume: mass), uniformly mixing, placing in a constant-temperature shaking table, vibrating, leaching and cleaning, controlling the temperature to be 25-30 ℃, and controlling the rotation speed of the shaking table to be 150-200 r/min.
(5) And (4) filtering or centrifuging the product obtained in the step (4) to obtain fermented wheat straws, and drying the fermented wheat straws in an oven at the temperature of 50-80 ℃ for 48-96 hours.
(6) And (3) putting the product obtained in the step (5) into a porcelain boat, putting the porcelain boat into a tubular furnace for pyrolysis carbonization, and inputting nitrogen at a flow rate of 0.2-0.6L/min to ensure an anaerobic environment, wherein the pyrolysis carbonization temperature is 300-600 ℃, and the pyrolysis carbonization time is 60-200 min. And cooling the obtained product to room temperature, and taking out the product to obtain the biomass charcoal with high adsorption performance, which is prepared by taking the wheat straws after microbial fermentation as raw materials.
In order to characterize the modification effect of the microbial fermentation process on the biomass charcoal, the specific surface area of the biomass charcoal is analyzed by a surface characteristic analyzer.
Furthermore, the invention provides an application of the biomass charcoal in removing dyes and heavy metals in a water body.
The biomass charcoal prepared by the method is particularly suitable for adsorbing pollutants such as dye, heavy metal and the like in water or soil.
Compared with the prior art, the invention has the following advantages:
the invention utilizes the microorganism with lignocellulose degradation capability to ferment the straws, and then the straws are used for preparing the biomass charcoal, and the biomass charcoal is used as a biomass charcoal modification means. The method has low cost and good environmental and economic benefits. Meanwhile, a new way of secondary utilization is provided for the treatment of straw fermentation residues after microbial fermentation.
Compared with biomass charcoal prepared by using unfermented wheat straws, the biomass charcoal prepared by using fermented wheat straws has an initial concentration of 50mg L in water-1And 100mg L-1The removal efficiency of the organic dye methylene blue is improved by more than 50 percent; for the initial concentration of 100-300 mg L in the water body-1Heavy metal Cd2+The adsorption efficiency is improved by 300-400%; the method is simple, energy-saving and environment-friendly, and provides technical support for modification of the biomass charcoal and application of the biomass charcoal in pollutant removal.
Drawings
FIG. 1 is a graph comparing the effect of methylene blue adsorption by biomass charcoal prepared from unfermented or fermented wheat straw (a: the initial concentration of methylene blue is 50mg L)-1(ii) a b: the initial concentration of methylene blue was 100mg L-1)。
FIG. 2 shows that heavy metal Cd is adsorbed by biomass charcoal prepared from unfermented or fermented wheat straws2+The effect of (3) is compared with the figure.
Detailed Description
In order to make the objects, technical solutions and technical features of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
In the examples, the percentages indicated are by weight unless otherwise indicated.
The straw fermentation strain used in the invention is trichoderma asperellum T-1, is the prior art, is disclosed in Chinese patent with application publication number CN104450530A (application number 201410578593.X), is stored in the common microorganism center of China Committee for culture Collection of microorganisms 24/9 in 2014, and has the biological preservation number of: CGMCC No. 9722.
Example 1: preparation of Natural wheat straw charcoal (as a comparative example)
Crushing wheat straws, sieving with a 20-mesh sieve, drying, putting the straws into a porcelain boat, putting the porcelain boat into a tubular furnace, and performing pyrolysis carbonization, wherein nitrogen is input at a flow rate of 0.3L/min to ensure an anaerobic environment, the pyrolysis carbonization temperatures are controlled to be 600 ℃ and 800 ℃, and the pyrolysis carbonization time is 120 min. And cooling the obtained product to room temperature of 25 ℃, and taking out the product to obtain the biomass charcoal prepared by taking the natural wheat straws as the raw materials at the pyrolysis temperatures of 600 ℃ and 800 ℃ respectively.
Example 2: preparation of biomass charcoal from wheat straw by microbial fermentation
Inoculating trichoderma asperellum T-1 on a potato glucose agar culture medium in a streak manner, culturing for 5 days at a constant temperature of 28 ℃, washing spores by using a sterilized 0.1% (v/v) Tween 80 solution, filtering the spores by using sterilized three-layer mirror wiping paper, collecting the spores in a sterilized 50mL centrifuge tube, centrifugally collecting spore precipitates, adding 10mL of 0.1% Tween 80 to resuspend and clean the spore precipitates once, centrifuging to remove supernatant, adding 5mL of sterile water to resuspend the spores, and preparing spore suspension;
preparing a solid fermentation culture medium of wheat straws: the volume of the Mandel culture solution and the wheat straw: mixing at a mass ratio of 3.5:1 (mass: volume), and sterilizing at 121 deg.C for 30 min;
the Mandel culture solution is counted by 1L and prepared from the following raw materials by weight:
the pH of the Mandel broth was 5.5.
At 106Inoculating the spore suspension into a solid fermentation culture medium of wheat straws at the concentration of each spore/g of wheat straws, and standing and fermenting for 4d at a constant temperature of 28 ℃; citric acid buffer at pH 4.8 was mixed at 15: 1 (volume mL: mass g) is added into a wheat straw fermentation system, the mixture is uniformly mixed and then placed into a constant temperature shaking table to be vibrated, extracted and cleaned, the temperature of the shaking table is controlled to be 28 ℃, and the rotating speed of the shaking table is 150 r/min; filtering or centrifuging the leaching product to obtain fermented wheat straw, and drying in a 60 ℃ oven for 72 h;
putting the dried product into a porcelain boat, putting the porcelain boat into a tubular furnace for pyrolysis carbonization, inputting nitrogen at a flow rate of 0.3L/min to ensure an anaerobic environment, controlling the pyrolysis carbonization temperature to be 600 ℃ respectively, and controlling the pyrolysis carbonization time to be 120 min. And cooling the obtained product to room temperature of 25 ℃, and taking out the product to obtain the biomass charcoal prepared by taking the wheat straws after microbial fermentation as the raw material.
Comparative example 3: specific surface area comparative analysis of wheat straw charcoal
To ascertain the effect of temperature and microbial fermentation on the performance of biochar, the present invention measured and compared the specific surface area of biochar prepared from natural unfermented wheat straw and fermented wheat as raw materials in examples 1 and 2 using a surface feature analyzer (ASAP 2020Plus HD 88). Before the on-machine measurement, the sample is pretreated in a flowing gas degassing device to remove adsorbed pollutants. The degassing condition is 180 ℃, and desorption is carried out for 12 hours under the condition of flowing nitrogen. As can be seen from Table 1, the specific surface area of the biomass charcoal prepared by using the fermented wheat straws as the raw material is 3.46 times that of the natural wheat straw charcoal at the pyrolysis temperature of 600 ℃; when the pyrolysis temperature is increased to 800 ℃, the specific surface area of the natural wheat straw charcoal is 31.2 times that of the biochar obtained under the pyrolysis condition of 600 ℃, and the influence of the results on the adsorption performance of the biochar is specifically researched in comparative examples 3 and 4.
TABLE 1 comparison of specific surface area of Biomass charcoal
Sample (I)
|
Specific surface area (m)2 g-1)
|
600 ℃ of natural straw carbon
|
2.62
|
The fermented straw carbon is 600 DEG C
|
9.06
|
Natural straw 800 deg.C
|
81.67 |
Comparative example 3: comparison of adsorption efficiency of methylene blue
The wheat straw charcoal in the embodiment 1-2 is used for removing methylene blue in the water body, and the specific operation is as follows: respectively taking the initial concentration of 50mg L-1And 100mg L-1Adding 25mL of methylene blue aqueous solution into a triangular flask, adding 50mg of biomass charcoal sample, placing the mixture in a constant-temperature shaking table with the rotation speed of 150rpm and the temperature of 25 ℃ for reacting for 6 hours to ensure that adsorption balance is achieved; during the period, samples are periodically sucked, the supernatant is taken after centrifugation, the absorbance value at OD 665nm is measured by a spectrophotometer, and the concentration of the residual methylene blue in the solution is calculated according to a standard curve.
The adsorption effect of different biomass charcoals on methylene blue is shown in figure 1. The natural wheat straw carbon has no obvious adsorption balance in the adsorption process, and the fermented wheat straw carbon has obvious adsorption rising period and balance period in the adsorption process. When the initial concentration of methylene blue is 50mg L-1When the natural wheat straw charcoal is used, the maximum adsorption efficiency of the natural wheat straw charcoal on methylene blue at the pyrolysis temperature of 600 ℃ and 800 ℃ is 45.9% and 24.5% respectively; the maximum adsorption efficiency of the fermented wheat straw charcoal is 99.4%, and the adsorption efficiency is improved by at least 53.5%. And when the initial concentration of methylene blue is 100mg L-1When the natural wheat straw charcoal is used, the maximum adsorption efficiency of the natural wheat straw charcoal on methylene blue at the pyrolysis temperature of 600 ℃ and 800 ℃ is respectively 37.5% and 38.5%; the maximum adsorption efficiency of the fermented wheat straw charcoal is 88.8%, and the adsorption efficiency is improved by at least 49.3%. Therefore, although the specific surface area of the wheat straw charcoal can be greatly improved by increasing the pyrolysis temperature from 600 ℃ to 800 ℃, the biomass charcoal prepared by taking the wheat straws fermented by the microorganisms as the raw material has better dye adsorption performance, and the improvement effect of the microbial fermentation on the dye adsorption performance of the biomass charcoal is far greater than the effect achieved by increasing the pyrolysis temperature.
Comparative example 4: heavy metal Cd2+Comparison of adsorption efficiency
The wheat straw carbon in the embodiment 1-2 is used for removing heavy metal ions Cd in water body2+The method comprises the following specific operations: with a concentration of 0.1mol L-1NaNO of (2)3Solution as background solution, Cd was performed2+Adsorption experiment of (1). With cadmium nitrate Cd (NO)3)2Configuration of Cd2+Solutions of 100mg L initial concentration-1、150mg L-1、200mg L-1And 300mg L-1. Taking Cd with different initial concentrations2+Adding 20mL of each solution into a triangular flask, adding 20mg of biomass charcoal sample, mixing, placing in a constant-temperature shaking table with the rotation speed of 150rpm and the temperature of 25 ℃ for reaction for 24h, periodically sucking the sample, centrifuging, taking the supernatant, measuring by using an atomic absorption instrument (ICE 3500z), and calculating the residual Cd in the solution according to a standard curve2+The concentration of (c).
Different biomass carbon pairs Cd2+The adsorption effect of (2) is shown in FIG. 1. The initial concentration of the natural wheat straw charcoal pair obtained at the pyrolysis temperature of 600 ℃ is 100mg L-1、150mg L-1、200mg L-1And 300mg L-1Cd (2)2+The maximum adsorption efficiencies of the adsorbent are 22.3%, 18.5%, 9.2% and 6.2%, respectively; the initial concentration of the natural wheat straw charcoal pair obtained at the pyrolysis temperature of 800 ℃ is 100mg L-1、150mg L-1、200mg L-1And 300mg L-1Cd (2)2+The maximum adsorption efficiencies of the adsorbent are 22.3%, 18.5%, 9.2% and 6.2%, respectively; the fermented wheat straw charcoal has different initial concentrations of Cd2+The adsorption efficiency is respectively up to 99.1%, 87.4%, 48.8% and 27.2%, and the adsorption efficiency of the traditional wheat straw charcoal is respectively improved by 344.4%, 372.4%, 430.4% and 338.7%. Therefore, although the specific surface area of the wheat straw charcoal can be greatly improved by increasing the pyrolysis temperature from 600 ℃ to 800 ℃, the biomass charcoal prepared by taking the wheat straws fermented by the microorganisms as the raw material has better heavy metal adsorption performance, and the improvement effect of the heavy metal adsorption capacity of the biomass charcoal through the microbial fermentation is far greater than the effect achieved by increasing the pyrolysis temperature.
It can be seen from comparative examples 2, 3 and 4 that the adsorption performance of the biomass charcoal prepared from the wheat straw fermented by the microorganism is greatly improved, and the improvement effect is much greater than the effect achieved by increasing the pyrolysis temperature.
The foregoing list is only illustrative of several embodiments of the present invention. The present invention is not limited to the above embodiments, and many variations are possible. All modifications which can be derived or suggested by a person skilled in the art from the disclosure of the present invention are to be considered within the scope of the invention.