KR20140115019A - Manufacturing method of biochar using sewage sludge and its effect on Pb immobilization in soil - Google Patents

Abstract

The present invention relates to a method for manufacturing a biochar using sewage sludge and a novel purpose for a heavy metal adsorption of the biochar manufactured by the same. More specifically, the present invention relates to Pb-immobilization effect in soil contaminated by heavy metal, derived from a biochar manufactured in a specific process using sewage sludge. The biochar manufactured from sewage sludge has a function of adsorbing heavy metal in soil which is contaminated by heavy metal, and is especially effective in adsorbing lead (Pb). Therefore, the biochar can be useful as a material for improving and stabilizing soil which is contaminated by lead (Pb). Moreover, since sewage sludge which requires a delicate treatment is used as a component, the present invention is capable of providing solutions to both recycling of waste resource and prevention of environmental pollution.

Description

[0001] The present invention relates to a method for producing bio-tea using sewage sludge, and a method for immobilizing lead (Pb)

The present invention relates to a method for producing a bio-tea using sewage sludge and a novel use of the bio-tea for the heavy metal adsorption. More specifically, the present invention relates to a method for producing a bio-tea using sewage sludge, (Immobilizing) the adsorbent effectively.

As the living standard increases due to urbanization and industrialization due to population growth, the amount of sludge generated is proportionally increased. Sludge refers to the wastewater discharged from factories and households by treating wastewater from water and wastewater and separating suspended matter from the liquid from the liquid. It is a semi-solid, which affects odor generation and natural ecosystem. The sludge formed in the wastewater treatment process has many pollutants such as heavy metals, high perishability and high water content. Such sludge is becoming a serious problem with solid wastes in various industrial fields and cities with limited land area, and the water content of the sludge, perishability, pathogenicity, environmental hazard potential and technical problem of treatment are important (Yoon, 1995). In addition, the marine dumping of sewage sludge will be banned in 2012 due to the London Convention, and countermeasures against marine dumping should be sought, which accounts for about 50% of the treatment methods.

On the other hand, some sludges considered as waste are valuable as natural resources, including important nutrients and organic matter. In developed countries, efforts are being made to conserve resources and conserve resources. J. of KOWREC, 8 (3), "Sewage Sludge Recycling Status and Prospect", Jae-Keun Bae, "Composting of Sludge as a Resource" , 9-30 [2000]).

However, there is a possibility that the accumulation of various heavy metals in sewage sludge, the inhibition of the growth of crops due to the toxic substances generated in the compaction of large amounts of salinity and inhaled organic matter, the possibility of lethal toxicity due to the bioconcentration of heavy metals, (Jung, K., Y., "Organic Wastes Recycling", Korean J. Soil Sci. Fert., 31 (SI), 30-33 [1995]) is also concerned with the negative effects of soil and groundwater contamination due to leaching.

Therefore, it is possible to cope with the problem of composting sludge which is difficult to treat, but it is necessary to effectively treat sewage sludge according to the result that it can cause heavy metals and toxicity.

On the other hand, biochar refers to a substance produced by pyrolyzing an organic material under an oxygen-free closed space under a temperature condition of 700 ° C or less. The material of the bio-tea may be a plant, Can also be the material of bio-tea. Patent patents relating to biocha are disclosed in Korean Patent No. 10-1190282, in which a bio-tea is produced by using by-product of wood (sycamore, willow tree, hardwood, maple leaf, And the like.

However, the stabilizing effect (use) of lead (Pb) -contaminated soil of bio-tea produced using sewage sludge has not been elucidated.

Therefore, the present inventors have tried to solve the waste disposal problem and the recycling of waste resources simultaneously by producing bio-lane in addition to composting as a treatment method of sewage sludge. As a result, the bio-car produced under a specific condition using sewage sludge (Pb) in a form usable in organisms contained in the soil (immobilization) to convert it into a form that the organism can not absorb, thereby effectively stabilizing the contaminated soil.

Korean Patent No. 10-1190282

Accordingly, an object of the present invention is to provide a method for producing bio-tea using sewage sludge.

Another object of the present invention is to provide a biochip for adsorbing heavy metals in soil produced by the above method.

It is still another object of the present invention to provide a soil improving composition comprising the above-mentioned heavy metal adsorbing biochain as an effective ingredient.

In order to achieve the above-mentioned object of the present invention,

(A) preparing a sewage sludge; (b) drying the prepared sewage sludge at a high temperature; (c) pulverizing the dried sewage sludge; And (d) thermally decomposing the pulverized material. The present invention also provides a method for producing biochar using sewage sludge.

In one embodiment of the present invention, the step (b) may be a step of drying the sewage sludge at a temperature ranging from 100 ° C to 110 ° C to a moisture content of 1% to 10%.

In one embodiment of the present invention, the step (c) may be a step of pulverizing the dried sewage sludge to a particle size of 1 mm to 3 mm.

In one embodiment of the present invention, the step (d) may include heating the pulverized product at a rate of 7 ° C / minute (min) and pyrolyzing the product at 300 ° C to 700 ° C for 2 hours to 4 hours have.

The present invention also provides a biochip for adsorbing heavy metals in soil produced by the above method.

In one embodiment of the present invention, the heavy metal may be lead (Pb).

In one embodiment of the present invention, the bio-car can stabilize the contaminated soil by immobilizing the lead (Pb) in a form that is usable for the organisms contained in the soil, .

The present invention also provides a composition for soil improvement comprising the above-mentioned bioacci for adsorbing heavy metals as an effective ingredient.

The bio-tea produced from the sewage sludge according to the present invention has a function of adsorbing heavy metals in the soil contaminated with heavy metals, particularly excellent in the adsorption function of lead (Pb), so that the material of the soil conditioner stabilizing the soil contaminated with lead (Pb) . ≪ / RTI > Further, in the case of the present invention, by using sewage sludge in a state difficult to be treated, there is an advantage that the environmental pollution problem can be prevented along with utilization of waste resources.

1 is a photograph showing a surface image according to the pyrolysis temperature (300 ° C., 700 ° C.) of the sewage sludge bio-tea of the present invention ((a): SS (Sewage sludge powder before pyrolysis), (b): SBC300 ): SBC700).
2 is a graph showing the result of functional group analysis according to the pyrolysis temperatures (300 ° C, 400 ° C, 500 ° C, 600 ° C and 700 ° C) of the sewage sludge bioassay of the present invention.
3 is a graph showing the results of particle size analysis according to the thermal decomposition temperatures (300 ° C, 400 ° C, 500 ° C, 600 ° C and 700 ° C) of the sewage sludge bioassay of the present invention.
4 is a graph showing an evaluation of lead (Pb) adsorption effect of heavy metal contaminated soil according to the pyrolysis temperature (300 ° C, 400 ° C, 500 ° C, 600 ° C and 700 ° C) of the sewage sludge bio- (A) 0.1N HCl extracted Pb, (b): 1M CaCl ₂ extracted Pb, and (b) the concentration of lead (Pb) ion in the soil after applying each sewage sludge bio- _{(c) 0.43M CH 3 COOH extracted} Pb).

(A) preparing a sewage sludge; (b) drying the prepared sewage sludge at a high temperature; (c) pulverizing the dried sewage sludge; And (d) thermally decomposing the pulverized material. The method of the present invention is characterized by using the sewage sludge.

Step (a) of the present invention is a step of preparing sewage sludge.

The term "sewage sludge" of the present invention means a sludge remaining after collecting and dehydrating foreign matter introduced into a sewage treatment plant by gravity sedimentation or chemical treatment.

In the present invention, sewage sludge used as a raw material of bio-tea is sludge produced in a general sewage end-treatment plant and sewage sludge having a moisture content of 50% or less produced through a process of a concentration tank, a coagulation tank and a dehydrator can be used.

The step (b) of the present invention is a step of drying the sewage sludge prepared in the step (a) at a high temperature, in detail, a step of drying at a high temperature of 100 ° C or more to reduce the moisture content of the sludge produced in the sewage end treatment plant.

In one embodiment of the present invention, the step (b) is a step of heating the sewage sludge at 100 ° C to 110 ° C It can be dried so that the moisture content is within 10%.

The step (c) of the present invention is a step of pulverizing the dried sewage sludge. In detail, the sewage sludge dried to have a moisture content of 1% to 10% through the step (b) And pulverizing the resulting mixture into particles having a particle size.

In one embodiment of the present invention, the step (c) may be a step of pulverizing the dried sewage sludge to a particle size of 1 mm to 3 mm to obtain a pulverized product.

The step (d) of the present invention is a step of pyrolyzing the pulverized product. Specifically, the pulverized product obtained through the step (c) is heated at a constant rate and thermally decomposed in a temperature range of 700 ° C or lower. Thereby obtaining a bio-tea.

In one embodiment of the present invention, the step (d) may include heating the pulverized product at a rate of 7 ° C / minute (min) and pyrolysis at 300 ° C to 700 ° C for 2 to 4 hours.

In another embodiment of the present invention, the step (d) comprises heating the pulverized product at a rate of 7 ° C / minute (min), heating the product at 300 ° C, 400 ° C, 500 ° C, 600 ° C, Pyrolysis can proceed.

The present inventors have found that the bio-tea produced through the steps (a) to (d) has a function of adsorbing heavy metals in the soil contaminated with heavy metals, and particularly excellent in the adsorption function of lead (Pb) And that it can be useful as a soil remediation agent for stabilizing contaminated soil.

As a result of examining the heavy metal adsorption effect according to the application to the heavy metal contaminated soil of the bio-tea produced according to the above-mentioned production method, the bio-tea of the present invention was found to contain lead (Pb) As the pyrolysis temperature for producing bio-tea increased, it showed a higher efficiency in stabilizing lead (Pb) (see FIG. 4) in a constant temperature incubation experiment.

As a result, the inventors of the present invention found that the sewage sludge bio-car produced by the above-described method can be converted into a form that can not be absorbed by living organisms by immobilizing lead (Pb) Lt; RTI ID = 0.0 > soil. ≪ / RTI >

Therefore, the bio-tea of the present invention can be effectively used as a material for heavy metal adsorption in soil, and can effectively adsorb lead (Pb) in heavy metals.

Accordingly, the present invention further provides a biochip for heavy metal adsorption produced by the above production method and a composition for improving soil comprising the same as an active ingredient.

Hereinafter, the present invention will be described in more detail with reference to Examples. These examples are for further illustrating the present invention, and the scope of the present invention is not limited to these examples.

< Example  1>

The Bio tea  Produce

<1-1> Sewage sludge  collection

Sewage sludge collection area was selected as a sewage treatment facility in Chuncheon city, Gangwon province. Sewage sludge was collected from a dehydrator which was processed through concentration tank, conditioning tank and dehydrator process and discharged with the lowest water content. And dried in a 105 ° C oven for 48 hours to reduce the moisture content of the sewage sludge. The dried sewage sludge was crushed using a rubber hammer and passed through a 2 mm standard body for analysis and production of bio-tea. In the following, it was named 'SS'.

<1-2> Bio tea  Produce

In this experiment, SS produced through the above Example <1-1> was pyrolyzed to produce bio-tea using sewage sludge.

In detail, the temperature was raised at a rate of 7 ° C per minute using Programmed Box-type Muffle Furance (Mod.No: N11 / H) [Nabertherm GmbH, Germany] to produce 300, 400, 500, The pyrolysis was carried out for the same time for 3 hours. The cooling of the bio-tea was allowed to cool to room temperature (about 12 hours) in the painting furnace. The thus-produced bio-tea of the present invention was named as SBC300, SBC400, SBC500, SBC600, and SBC700, respectively, according to the pyrolysis temperature, and used as a sample in the following experiment.

< Example  2>

[0050] Bio-car  Character analysis

<2-1> Bio tea  Chemical evaluation

For the chemical analysis of the bio-tea of the present invention manufactured through Example 1, the pH and EC (electrical conductivity) of the bio-tea were measured according to the soil pollution process test method.

3 g each of analytical samples (SS, SBC300, SBC400, SBC500, SBC600, and SBC700) were placed in 50 ml PDEF tubes, 15 ml distilled water was added (1 Soil: 5 Water method) 7110 BNC, WTW, Germany). The pH of the suspension was filtered with Whatman No. 42 and the EC was measured using an electrode (orion 3 star, Thermo, USA).

As a result, as shown in the following Table 1, it was confirmed that the pH tended to increase from 5.88 to 8.12 as the pyrolysis temperature increased from 0 ° C to 700 ° C in the production of bio-tea, It was judged that the acidic group was increased due to volatilization at high temperature. On the other hand, EC showed a tendency to increase with increasing pyrolysis temperature and showed the highest value in SBC400 because the content of inorganic matter in the bio-tea reached a maximum value at 400 ° C . In addition, EC tends to decrease gradually in the order of SBC500, SBC600, and SBC700. This is because the SS, which is the raw material, is not a single substance such as a plant but a mixture of various substances, Seems to be.

<2-2> Bio tea  Industrial analysis evaluation

The industrial analysis of the bio-tea of the present invention prepared in Example 1 was evaluated.

In detail, the water content contained in the analytical samples (SS, SBC300, SBC400, SBC500, SBC600, SBC700) was measured according to the waste process test method. The evaporation dish was preliminarily dried at 105 ° C for 1 hour, and then taken out and weighed. After putting the sample, the sample was dried for 24 hours and then cooled in a desiccator and the weight of the evaporation dish and the sample was precisely measured. After that, the residual samples were pyrolyzed in a painting furnace at 450 ° C and 750 ° C for 30 minutes to measure volatile matter and ash. Each value was calculated as a weight percentage and substituted into the following equation (1) to calculate the amount of fixed carbon as a percentage.

As a result, as shown in the following Table 1, it can be confirmed that the moisture content in the case of Moisture is smaller as the biocham produced at high temperature is. Also, the volatiles tend to decrease because of the volatilization of organics at high temperature and the formation of fixed carbon. The ash tends to increase differently from the moisture and mobile matter because it was considered to be the organic matter remaining in the sewage sludge.

[Equation 1]

Water (%) + volatiles (%) + ash (%) + fixed carbon (%) = 100%

<2-3> Bio tea  Elemental analysis

The element of the bio-tea of the present invention prepared through Example 1 was analyzed. H, O, N, and S were quantified using an element analyzer (FlashEA1112, Thermo, USA). For reference, the elemental analysis results can be used to indirectly predict the amount of gas generation, composition, and reactant balance among the substances generated during pyrolysis of biochar through CEA code.

As a result, as shown in Table 1, SBC300 showed a slight increase in carbon, and other elements showed a tendency to decrease. In the case of O / C, it can be confirmed that as the production temperature increases, it decreases. It is considered that the oxygen bonded to the amide compound in O / C is decreased by separating from carbon at high temperature. Also, the ratio of H / C with increasing pyrolysis temperature is decreased from 1.98 to 0.31%, which means that carbon is changed to fixed carbon (45.14 ~ 69.20%). The decrease of H / C is considered to be the phenomenon that hydrogen of aliphatic compound and aromatic compound is separated from carbon. As a result, it was found that the degree of carbonization was increased due to the increase of the ratio of the fixed carbon to the volatile content as a result of the industrial analysis. As a result, it was confirmed that the value of sewage sludge as fuel increased as the pyrolysis temperature increased.

<2-4> Bio tea  Surface analysis

(Brunauer, Emmet, Teller) analysis was performed to examine the specific surface area and pore size of the bio-tea of the present invention prepared in Example 1. The analytical samples (SS, SBC300, SBC400, SBC500, SBC600, SBC700) were measured using Particle and Pore Size Analysis System.

Scanning electron microscope (SEM) analysis is an analytical method to investigate the surface characteristics from various kinds of signals generated by the interaction of electron beam and surface. Using SEM (S-4300, HITACHI, Japan) , 600, and 700 were observed. Sample particle size and particle size distribution were analyzed with a particle size analyzer (Matersizer 2000, Malvern, UK).

As shown in Table 1, the specific surface area was increased from 4.01 to 54.76 m 2 / g as the pyrolysis temperature was increased, and the pore volume was also increased to 0.01 to 0.05 cm 3 / g. The overall results of the characterization analysis show that the increase of the specific surface area and the increase of the porosity will contribute to the formation of the soil as a soil remediation agent and the formation of stable form of fixed carbon. On the other hand, in case of pore size, pore size decreases with increasing temperature, but the result of this study does not show a tendency to decrease because it is a mixed material with mixed wastewater It is presumed that the general tendency does not appear.

On the other hand, the image of the surface is shown in FIG. 1, and it can be seen that the size of the pore decreases in the case of the bio-tea produced under the high temperature condition. As a result, porosity was increased and it was judged that it would improve water and nutrient retention ability as a porous material like the results of other biochains.

pH EC Yield Moisture Mobile Matter Resident Matter Ash C H N S O H / C O / C BET
Surface
Area (dS / m)  (%) (m ² / g) 5.882 5.05 - 4.50 48.09 11.53 35.90 27.60 4.56 4.11 0.86 24.02 1.98 0.65 4.01 6.759 0.129 70.13 1.09 19.79 22.48 56.63 30.72 3.11 4.11 0.68 11.16 1.22 0.27 4.46 6.550 0.859 57.40 0.54 8.79 23.54 67.12 26.62 1.93 4.07 0.44 10.67 0.87 0.30 14.08 7.266 0.552 53.82 0.66 7.49 19.97 71.87 20.19 1.08 2.84 0.44 9.81 0.64 0.36 26.16 8.328 0.439 51.21 0.51 5.80 19.06 74.63 24.76 0.83 2.78 0.41 8.41 0.40 0.26 35.81 8.125 0.391 50.27 0.61 4.11 16.63 76.55 22.04 0.57 1.73 0.42 7.09 0.31 0.24 54.76

< Example  3>

Invention Bio-car  Evaluation of action mechanism

In order to examine the chemical bonding state of each sample before and after the heat treatment of the bio-tea of the present invention prepared in Example 1, functional groups were analyzed using FT-3000 (Bio-Rad, USA).

As a result, as shown in FIG. 2, it can be seen that peaks do not gradually appear as the temperature for producing the bio-tea increases. This is because most of the oxygen and hydrogen elements are volatilized due to the high temperature and the stable carbon structure remains in the SBC700. The result that the stabilized carbon structure remained was confirmed in FIG. 2 that the peak of Aromatic CH was generated as the pyrolysis temperature was increased.

< Example  4>

Invention Bio-car Particle size analysis  evaluation

The particle size and particle size distribution of the bio-tea of the present invention prepared in Example 1 were analyzed by a particle size analyzer (Matersizer 2000, Malvern, UK).

As a result, as shown in FIG. 3, a bar graph corresponding to the particle size of SBC300-700 is shown, and although the SBC600 and SBC700 graphs are similar, the range of the particle size is smaller than BC700 . This result shows that the size of the particle size is reduced as the temperature rises. These results suggest that floc and cell wall destruction of sewage sludge proceeds even during the rising temperature of the reaction (Han, SK, S, HW, Choi, CS, Kim, H., Lee, Sewage Sludge according to Thermal Hydrolysis Reaction Temperature, &quot; Journal of Material Cycles and Waste Managemnet, 29 (4), 414-420 (2012)).

< Example  5>

Invention Bio-car  lead( Pb ) Stabilization effect by contaminated soil application

<5-1> Lead ( Pb ) Contaminated soil collection

Lead - contaminated soils were cultivated soil located in the vicinity of Sunglim - Seokdam mine site in Wonju, Gangwon - do. Soil frames around abandoned mines were contaminated with harmful heavy metals such as lead (Pb), arsenic (As), and copper The contaminated soil was removed from the soil after drying and sieved using a 2 mm standard. Soil and plant analysis method (Agricultural Science and Technology Institute, 2000) and analysis results were applied to Korean soil information system provided by National Academy of Agricultural Sciences, ).

<5-2> Lead ( Pb Evaluation of chemical properties of contaminated soil

The contents of pH, EC, OM, Ca, K, Mg, P2O5, NH4, NO3, T-N and T-C were analyzed in order to evaluate the chemical properties of the lead contaminated soil prepared in Example <5-1>.

The pH and EC of the soil were determined by 1Soil: 5Water method, the organic content was determined by Tyurin method, the effective phosphate was determined by Lancaster method, ammonia and nitrate nitrogen were extracted by Kjeldahl distillation method, and the substitutional cations were extracted by 1M-NH4OAc (pH 7.0) (ICP-OES, GBC Integra XL, Australia) (NIAST, 2000). The total carbon (T-C) and total nitrogen (T-N) were analyzed with an elemental analyzer (vario MAX CN, Elementar, Germany).

The results are shown in Table 2 below.

Chemical analysis of lead (Pb) contaminated soil Sample pH EC OM Ca K Mg Na P ₂ O ₅ NH4 NO3 T-N T-C dS / m g / kg mg / kg % CK 7.0 0.54 30.25 8.40 0.27 1.35 0.36 289 9.62 29.23 0.12 1.15

<5-3> Lead ( Pb ) Indoor incubation experiment of contaminated soil

In order to examine chemical properties of the soils contaminated with lead (Pb) contaminated soil of the present invention prepared in Example 1, the soil pH of the soil after treatment with the present invention was measured, EC, OM, Ca, K, Mg, P2O5, NH4, NO3, TN and TC contents were analyzed.

In detail, analytical samples (SS, SBC300, SBC400, SBC500, SBC600, SBC700) were applied in 1%, 3% and 5% (w / w) proportional to the soil weight and 3 replicates per treatment Three CKs and three SSs (1, 3, and 5%) and three SBC300, 400, 500, 600, and 700 (1, 3, and 5%) were incubated for 35 days.

The results are shown in Table 3 below.

Sample pH
1: 5 EC OM Ca K Mg Na P ₂ O ₅ NH ₄ NO ₃ T-N T-C dS / m g / kg mg / kg % SS  (One%) 6.64 1.15 32.50 8.32 0.33 1.45 0.37 272 8.58 176.93 0.20 1.88 SS  (3%) 6.36 3.01 32.28 7.73 0.30 1.26 0.22 341 24.50 309.64 0.27 2.17 SS  (5%) 6.24 3.54 42.66 8.15 0.40 1.59 0.30 380 59.39 339.50 0.36 2.53 300 (1%) 6.98 0.67 31.79 7.64 0.47 1.24 0.24 313 8.75 54.66 0.17 1.83 300 (3%) 7.00 0.76 35.54 8.32 0.35 1.53 0.35 327 6.59 56.70 0.22 2.15 300 (5%) 6.99 0.86 36.68 7.90 0.36 1.49 0.26 332 4.90 56.18 0.28 2.30 400 (1%) 7.00 0.68 32.48 7.38 0.30 1.21 0.24 353 5.60 53.32 0.17 1.81 400 (3%) 7.03 0.87 37.65 7.39 0.34 1.25 0.35 418 5.19 53.79 0.23 2.11 400 (5%) 7.00 0.92 36.96 7.55 0.37 1.25 0.33 435 4.90 58.40 0.26 2.25 500 (1%) 7.03 0.59 30.15 7.69 0.30 1.28 0.34 307 6.77 53.96 0.20 2.08 500 (3%) 7.02 0.67 36.78 7.41 0.32 1.28 0.21 317 7.59 49.19 0.23 2.35 500 (5%) 6.96 0.64 37.46 6.91 0.32 1.26 0.06 415 5.37 48.24 0.32 2.73 600 (1%) 6.97 0.53 29.69 7.69 0.30 1.31 0.18 303 6.42 43.87 0.20 2.09 600 (3%) 6.89 0.52 35.40 7.37 0.31 1.28 0.26 323 5.54 48.54 0.22 2.26 600 (5%) 6.98 0.66 36.95 7.04 0.30 1.23 0.05 356 5.48 43.11 0.26 2.50 700 (1%) 6.96 0.53 28.44 7.29 0.30 1.31 0.03 309 3.56 44.08 0.18 2.05 700 (3%) 6.98 0.55 32.97 7.46 0.30 1.29 0.04 282 4.96 41.42 0.20 2.23 700 (5%) 7.00 0.60 37.65 7.35 0.31 1.33 0.09 336 5.25 41.77 0.21 2.45

After the incubation, the soil was collected and used as a sample for the extraction of heavy metals.

&Lt; 5-4 > Bio-car  Heavy metal adsorption effect

In order to evaluate the stabilization of the soil according to the application to the lead (Pb) contaminated soil of the bio-tea of the present invention manufactured through Example 1, the soil sample after the indoor temperature incubation experiment in Example <5-4> After sealing, it was transported to the laboratory and analyzed by air drying and sieving with a standard body of 2 mm or less.

Domestic soils contaminated process test method of extraction 0.1N HCl, 1M CaCl ₂ and extracted 0.43M CH ₃ COOH extraction each sample for analysis in this study, a method for use in assessing the soil contaminated environmental conservation law based on (SS, SBC300, SBC400 , SBC500, SBC600, and SBC700) were weighed 5% (w / w) in proportion to the weight.

First, 0.1 N HCl extraction was carried out by taking 10 g of soil into a container, adding 50 ml of 0.1 N HCl, stirring at 30 ° C for 1 hour, filtering with Whatman No. 42, and then concentration of residual heavy metal ions in the filtrate was measured by ICP-OES Elmer Optima 2000DV). Further, 1M CaCl ₂ extraction is received, the supernatant was stirred at 30 rpm for 24 hours at room temperature, it was added 200ml of 1M CaCl ₂ taken 5g of soil in containers and centrifuge for 10 minutes, the concentration of the heavy metal ions remaining in the filtrate is then ICP- OES (Perkins Elmer Optima 2000DV). In addition, 0.43M CH ₃ COOH extraction was carried out by taking 5 g of soil in a container, adding 200 ml of 0.43 M CH ₃ COOH, stirring at room temperature for 16 hours, stirring at 30 rpm, centrifugation for 10 minutes to obtain a supernatant, Were analyzed using ICP-OES (Perkins Elmer Optima 2000DV).

As a result, as shown in FIG. 4, the biocide of the present invention effectively reduced lead (Pb) in heavy metals. When the pyrolysis temperature for producing bio-tea was increased, ), Which is more efficient for stabilization. Especially, it was confirmed that Pb extracted by the heavy metal extraction method such as 0.1N HCl was less than the lead (Pb) concentration by 5%. In addition, Cu and Zn contents in sewage sludge also showed a tendency to decrease. As a result of the above characteristics analysis and indoor temperature incubation experiment, it was possible to stabilize lead (Pb) in soil and possible recycling possibility as soil improvement agent.

As a result, it was found that the bio-tea of the present invention changed into a porous material as the temperature at which it was produced increased. In the case of pH, the tendency to increase and decrease was observed as in the case of general biochemical studies. In the case of EC, the tendency of increase and decrease could be confirmed by the existence of temperature which is the peak of inorganic matter, It seems to have appeared. In addition, since the bio-tea of the present invention has a wide surface area and is a porous material like other bio-tea, it can be utilized as a soil improving agent in Korea where acidic soil is dominant due to basicity of water and nutrient retention ability and pH.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (8)

(a) preparing sewage sludge;
(b) drying the prepared sewage sludge at a high temperature;
(c) pulverizing the dried sewage sludge; And
(d) thermally decomposing the pulverized material. The method for producing biochar using sewage sludge according to claim 1, The method according to claim 1,
Wherein the step (b) comprises drying the sewage sludge at a temperature ranging from 100 ° C to 110 ° C to a moisture content of 1% to 10%. The method according to claim 1,
Wherein the step (c) comprises pulverizing the dried sewage sludge to a particle size of 1 mm to 3 mm. The method according to claim 1,
Wherein the step (d) comprises heating the pulverized product at a rate of 7 ° C / min and pyrolyzing the product at a temperature of 300 ° C to 700 ° C for 2 hours to 4 hours. The method for producing a biochar using the sewage sludge . A biochar for adsorbing heavy metals in soil produced by the method of any one of claims 1 to 4. 6. The method of claim 5,
Wherein the heavy metal is lead (Pb). The method according to claim 6,
Characterized in that the bio-car is immobilized with a lead (Pb) in a form usable in the soil to transform it into a form that can not be absorbed by the organism, thereby stabilizing the contaminated soil (Biochar ). A composition for soil improvement comprising a biochar for adsorbing heavy metals (Biochar) as an active ingredient.

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