CN115015399A - Method for evaluating real capacity of biochar in soil for adsorbing organic pollutants - Google Patents

Abstract

The invention discloses an evaluation method of true capability of biochar to adsorb organic pollutants in soil, belonging to the field of soil pollution control, wherein the adsorption capability of biochar to organic pollutants is S1, the adsorption capability of soil to organic pollutants is S2, the theoretical adsorption capability of mixed components of biochar and soil to organic pollutants is S3, the mass fractions of biochar and soil in the mixed components are X, Y respectively, then S3 is X S1+ Y S2, the actual adsorption capacity of the mixed component to the organic pollutants is S4, S4 is K S3, K is 0.4-0.9, the method can accurately evaluate the real adsorption capacity of the biochar in the soil to the organic pollutants, and has certain reference significance for the field of soil organic matter pollution control.

Description

A method for evaluating the true ability of biochar to adsorb organic pollutants in soil

technical field

The invention relates to a method for evaluating the true ability of biochar to adsorb organic pollutants in soil, and belongs to the field of soil organic pollutant treatment.

Background technique

Rhodamine B is a typical organic dye, easily soluble in water and ethanol, with red to violet color and strong fluorescence. It is often used in the dyeing industry of paper, fireworks, textiles and leather. Processes such as migration and transformation, absorption and metabolism of organisms, etc., have certain destructive effects on the water body and soil environment, and have a certain degree of damage to the health of organisms. Biochar is a carbonaceous material produced by biomass after high-temperature pyrolysis under anoxic or anaerobic conditions. The adsorption capacity can be used to adsorb organic pollutants in the environment.

At present, the situation of organic pollution in soil is relatively serious. Biochar of different raw materials has good adsorption effect on organic pollutants. Adding biochar into soil to adsorb organic pollutants is a practical method. The real adsorption effect of biochar in soil is affected by various factors. The adsorption effect of biochar itself on organic pollutants cannot be equal to its adsorption effect in soil. The real adsorption capacity of biochar in soil to organic pollutants To be assessed.

SUMMARY OF THE INVENTION

Aiming at the problems existing in the prior art, the present invention provides a method for evaluating the real adsorption capacity of biochar in soil for adsorbing organic pollutants, which can better evaluate the real adsorption capacity of biochar in soil for organic pollutants.

The technical scheme of the present invention is as follows:

A method for evaluating the true ability of biochar to adsorb organic pollutants in soil, the specific steps are as follows:

(1) Collect and select natural soil, air-dry it, grind it through a 100-mesh sieve, and dry it in an oven at 60°C for more than 12 hours;

(2) Using a milligram scale, accurately weigh 200mg of organic pollutant solids and 200mg of sodium azide (sodium azide is used to eliminate the influence of microorganisms), mix them into a 1L brown volumetric flask and make up to volume with ultrapure water to obtain a concentration of 200mg/L organic pollutant solution, measure 500mL and 250mL organic pollutant solution with a concentration of 200mg/L respectively, and dilute to a 1L brown volumetric flask to obtain organic pollutants with a concentration of 100mg/L and 50mg/L solution, all volumetric flasks are wrapped in tinfoil to protect from light;

(3) Using a gram scale (accuracy is 4 decimal places), accurately weigh 3 parts of X+Yg biochar and add them to a 250mL conical flask; accurately weigh 3 parts of Xg biochar and Yg soil and add them to a 250mL conical flask Mix and shake well; accurately weigh 3 parts of X+Yg soil and add it to the conical flask; wrap all conical flasks with tin foil to protect from light;

(4) Weigh 200g of organic pollutant solutions with concentrations of 50mg/L, 100mg/L and 200mg/L respectively and add them to the conical flask of step (3), put the conical flask into the shaker, and the shaker is set to The rotation speed was 140 rpm and the temperature was 24 °C, and the adsorption experiment was carried out;

(5) Sampling at different time points 1, 2, 4, 8, 12, 24, 36, 48, 60, 72h; the samples were measured by high performance liquid chromatography (HPLC), the results were obtained, and the amount of organic pollutants was calculated. Adsorption capacity;

(6) The adsorption capacity of biochar to organic pollutants is S1, the adsorption capacity of soil to organic pollutants is S2, and the theoretical adsorption capacity of the mixed components of biochar and soil to organic pollutants is S3, then S3=X* S1+Y*S2, X+Y=1, 0<X≤0.2, 0.2<Y<1, the actual adsorption capacity of the mixed components for organic pollutants is S4, and S3 is compared with S4, it can be concluded that S4= K*S3, K=0.4～0.9, when the pyrolysis temperature of biochar is 350～700℃, with the increase of pyrolysis temperature, the value of K also increases, S4 is the adsorption of biochar in soil The true capacity of organic pollutants.

The organic pollutants include Rhodamine B and the like.

The evaluation method of the invention can more accurately evaluate the real adsorption capacity of biochar in soil to organic pollutants, and the actual adsorption capacity of biochar and soil mixed components is lower than the theoretical adsorption capacity, indicating that the adsorption capacity of soil biochar is affected by the soil environment. After the biochar was added to the soil, the adsorption capacity of organic pollutants decreased significantly, but the mixed components of MBC-700 and soil were compared with the mixed components of MBC-350 and soil. The mixed components have higher adsorption capacity for organic pollutants and better adsorption effect.

The advantages and features of the present invention are:

Biochar itself has a good adsorption effect on organic pollutants. It is an ideal method to apply it to the soil environment to adsorb and fix organic pollutants. However, the adsorption capacity of biochar in soil is affected by various factors in the environment. , after adding biochar to soil, its adsorption capacity cannot be equal to that of biochar itself, and needs to be evaluated. In the experiment, it was observed that the actual adsorption capacity of the mixed components of biochar and soil was lower than its theoretical adsorption capacity, and with the increase of time, the adsorption capacity of the mixed components of biochar and soil to organic pollutants gradually decreased, indicating that the biochar The adsorption capacity of organic pollutants in soil is affected by soil environmental factors. The method provided by the invention can better evaluate the adsorption capacity of biochar in soil for organic pollutants, and further guide the application of biochar in soil pollution control, which has certain reference significance for the field of soil organic pollution control.

Description of drawings

Fig. 1 is the infrared spectrum of corn stalk biochar;

Figure 2 shows the actual and theoretical adsorption capacity of 50 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 350°C;

Figure 3 is a graph showing the actual and theoretical adsorption capacity of 50 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 700°C;

Figure 4 is a graph showing the actual and theoretical adsorption capacity of 100 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 350°C;

Figure 5 is a graph showing the actual and theoretical adsorption capacity of 100 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 700°C;

Figure 6 is a graph showing the actual and theoretical adsorption capacity of 200 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 350°C;

Figure 7 is a graph showing the actual and theoretical adsorption capacity of 200 mg/L Rhodamine B by corn stover biochar, soil and mixed components at 700°C.

Detailed ways

The present invention will be further described in detail below with reference to the specific embodiments, but the protection scope of the present invention is not limited to the content.

Example 1

The preparation method of MBC-350 biochar, the specific steps are as follows:

(1) Wash the corn stalks, put them into an oven and dry them at 60°C for 24 hours, and then use a pulverizer to pulverize them through a 100-mesh sieve;

(2) weigh 50g of the corn stalk powder of step (1) and put it into the crucible, cover the lid and put it into the muffle furnace, close the valve and continue to feed 150mL/min nitrogen for 30min, and discharge the air in the muffle furnace, During the pyrolysis process, nitrogen gas at 150 mL/min was continuously introduced, the temperature was raised to the target pyrolysis temperature of 350 °C, carbonized for 4 hours, the muffle furnace was closed, and it was naturally cooled to room temperature and taken out;

(3) Passing the corn stover biochar prepared in step (2) through a 100-mesh sieve, sealing and storing in a glass bottle, the obtained sample is named MBC-350.

Example 2

The preparation method of MBC-700 biochar, the specific steps are as follows:

(1) Wash the corn stalks, put them into an oven and dry them at 60°C for 24 hours, and then use a pulverizer to pulverize them through a 100-mesh sieve;

(2) weigh 50g of the corn stalk powder of step (1) and put it into the crucible, cover the lid and put it into the muffle furnace, close the valve and continue to feed 150mL/min nitrogen for 30min, and discharge the air in the muffle furnace, During the pyrolysis process, nitrogen gas at 150 mL/min was continuously introduced, the temperature was raised to the target pyrolysis temperature of 700 °C, carbonized for 4 hours, the muffle furnace was closed, and the furnace was naturally cooled to room temperature and taken out;

(3) Passing the corn stalk biochar prepared in step (2) through a 100-mesh sieve, sealing and storing in a glass bottle, the obtained sample is named MBC-700.

Table 1 below is an elemental analysis chart of MBC-350 and MBC-700.

Table 1

C% O% H% N% H/C O/C O+N/C MBC-350 4.2054 1.2443 3.9035 0.0723 0.9282 0.2959 0.3131 MBC-700 4.3841 0.6283 1.0668 0.0550 0.2433 0.1433 0.1559

Figure 1 shows the infrared spectra of MBC-350 and MBC-700. It can be seen from the figure that the surface of biochar has abundant functional groups, which are -OH at the wave number 3430cm ^-1 and alkane and aliphatic hydrocarbon groups at the wave number 2920cm ^-1 The group-CH ₂ stretching vibration is generated, the C=O bond stretching vibration of the carboxyl group at the wave number 1620 cm ^-1 is generated, and the CO stretching vibration of the ester group at the wave number 1100 cm ^-1 is generated.

Example 3

A method for evaluating the ability of biochar to adsorb organic pollutants in soil, the specific steps are as follows:

(1) Collect the local preferred red soil in Yunnan, air-dry it naturally, grind it through a 100-mesh sieve, and bake it in an oven at 60°C for more than 12 hours;

(2) Accurately weigh 200mg of organic pollutant solid rhodamine B and 200mg of sodium azide (sodium azide is used to eliminate the influence of microorganisms) using a milligram scale, mix them into a 1L brown volumetric flask and make up to volume with ultrapure water, To obtain Rhodamine B solution with a concentration of 200mg/L, measure 500mL and 250mL of Rhodamine B solution with a concentration of 200mg/L, and dilute to a 1L brown volumetric flask to obtain Rhodamine with a concentration of 100mg/L and 50mg/L. For solution B, all volumetric flasks are wrapped in tinfoil to protect from light;

(3) Using a gram scale (accuracy is 4 decimal places), accurately weigh 3 parts of 1g corn stalk biochar (both MBC-350 biochar and MBC-700 biochar are required) and add them to a 250mL conical flask; Weigh 3 parts of 0.1g biochar and 0.9g red soil into a 250mL conical flask, mix and shake well; accurately weigh 3 parts of 1g red soil and add them to the conical flask; wrap all the conical flasks with tin foil to protect from light ;

(4) Weigh 200g of Rhodamine B solution with concentrations of 50mg/L, 100mg/L and 200mg/L respectively and add it to the Erlenmeyer flask of step (3), put the Erlenmeyer flask into the shaker, set the rotating speed 140rpm, and the temperature 24°C for adsorption experiments;

(5) sampling at 1, 2, 4, 8, 12, 24, 36, 48, 60, 72h; on the sample, high performance liquid chromatography (HPLC) was measured to obtain the result, and the adsorption amount of Rhodamine B was calculated;

(6) The adsorption capacity of corn stalk biochar to Rhodamine B is S1, the adsorption capacity of red soil to Rhodamine B is S2, and the theoretical adsorption capacity of the mixed components of red soil and biochar to organic pollutants is S3, then S3=0.1 *S1+0.9*S2, the actual adsorption capacity of the mixed components of red soil and corn stover biochar to organic pollutants is S4, Figures 2, 3, 4, 5, 6, and 7 are the biochar, red soil and the mixture to Rhodamine B It can be seen from the figure that the actual adsorption capacity of rhodamine B by the mixture of biochar and red soil is lower than the theoretical adsorption capacity, indicating that the adsorption capacity of biochar on rhodamine B is affected by the soil environment. After the char is added to the soil, the adsorption capacity of organic pollutants has a relatively obvious decrease, but compared with the mixed components of MBC-700 and soil and the mixed components of MBC-350 and soil, the mixed components of MBC-700 and soil The adsorption capacity of organic pollutants is higher, and the adsorption effect is better.

According to the data in the examples and the attached drawings, S3 is compared with S4, S4=K*S3, S3=0.1*S1+0.9*S2, further, X represents the biochar in the mixed components of biochar and soil Y represents the mass fraction of soil in the mixed components of biochar and soil, X+Y=1, then theoretical adsorption capacity S3=X*S1+Y*S2, actual adsorption capacity S4=K*S3, and From Figure 2-7, it can be concluded that when the pyrolysis temperature of biochar is 350-700℃, K=0.4-0.9. As the pyrolysis temperature increases, the value of K also increases. When the pyrolysis temperature is 350 °C, the appropriate value of K is 0.4 to 0.5, and when the pyrolysis temperature of biochar is 700 °C, the appropriate value of K is 0.8 to 0.9; according to the doping ratio of biochar in soil, biochar In general, the incorporation amount of α does not exceed 20% of the total amount, then 0<X≤0.2, 0.2<Y<1.

Claims (2)

1. The method is characterized in that the adsorption capacity of the biochar on the organic pollutants is S1, the adsorption capacity of the soil on the organic pollutants is S2, the theoretical adsorption capacity of a mixed component of the biochar and the soil on the organic pollutants is S3, then S3 is X S1+ Y S2, X represents the mass fraction of the biochar in the mixed component of the biochar and the soil, Y represents the mass fraction of the soil in the mixed component of the biochar and the soil, X + Y is 1, the actual adsorption capacity of the mixed component on the organic pollutants is S4, S4K is S3, and K is 0.4-0.9.

2. The method for evaluating the real capability of the biochar in the soil for adsorbing the organic pollutants as claimed in claim 1, wherein the values of X and Y are as follows: x is more than 0 and less than or equal to 0.2, and Y is more than 0.2 and less than 1.

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