JP3170517B2 - Modification of oil-contaminated soil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reforming method for purifying and recovering oil-contaminated soil into healthy soil.

[0002]

2. Description of the Related Art In recent years, environmental pollution of soil and rivers caused by dumping edible or industrial waste oil has become a serious problem, and its purification is urgently required. Among these, as a method for treating oil-contaminated soil, a combustion method for directly heat-treating contaminated soil to burn and remove oil has been known for a long time. However, the combustion method requires large-scale combustion equipment and has a disadvantage that secondary air pollution is caused by combustion gas discharged out of the system.

As a treatment for detoxifying oil-contaminated soil using a chemical reaction by chemicals, a method of spraying and mixing lime onto soil is known, and requires special equipment as compared with the above-mentioned combustion method. This has the advantage of being economical and of simplifying the processing. However, according to this method, the dispersed lime instantaneously reacts with the moisture in the soil to form a local soil mass, resulting in uneven processing, and the returned untreated soil has an oil content of untreated soil. There is a problem that the outflow diffusion phenomenon easily occurs.

[0004] In order to solve such a problem, calcium oxide treated with a surfactant which delays the reaction with water is added to waste material, and calcium oxide carried on the waste material is substantially stoichiometric with water. A method of detoxifying an oily substance that is reacted until it becomes calcium hydroxide has been proposed.
58-2000). However, this method is costly due to the use of expensive chemicals such as fatty acids in order to treat quicklime, and causes secondary chemical damage when left as it is because the treated soil exhibits strong alkalinity. There are difficulties.

[0005]

SUMMARY OF THE INVENTION The present invention has been developed in order to solve the problems of the prior art relating to the purification of oil-contaminated soil as described above. An object of the present invention is to provide a method for reforming oil-contaminated soil that can effectively prevent diffusion and promote the rate of oil decomposition by microorganisms in soil to purify and recover healthy soil.

[0006]

According to the present invention, there is provided a method for modifying oil-contaminated soil, which comprises mixing high-temperature calcined quicklime powder with oil-contaminated soil, and then incorporating a microbial nutrient. This is a feature of the configuration.

[0007] In the treatment method of the present invention, high-temperature calcined lime powder is first mixed with oil-contaminated soil. This quicklime powder,
For example, it is formed by firing limestone in a temperature range of 1200 to 1500 ° C. and then pulverizing, and the hydration reactivity is effectively delayed by the high-temperature firing treatment. The mixing amount of the quicklime powder with respect to the oil-contaminated soil is appropriately set in consideration of the amount of oil and water contained in the soil, but is generally used in the range of 30 to 70% by weight. Quicklime powder reacts with the moisture in the mixed soil to generate heat, but quicklime fires at a high temperature and the hydration reaction is delayed, so the reaction progresses slowly, resulting in uneven reaction and formation of soil clumps. Phenomenon is suppressed.

[0008] When the reaction with the quicklime powder is completed, the microbial nutrient is subsequently sprayed and mixed with the soil. The microbial nutrient is a component that functions to promote the decomposition of oil components by microorganisms in soil, and at least one selected from yeast, yeast extract, and rice bran is applied. A particularly effective microbial nutrient is rice bran, which further promotes the emulsification and dispersal of the oil and accelerates the decomposition rate due to its surfactant activity. Besides,
Since the soil after the treatment is converted to hydrophobic, it effectively functions to prevent the outflow and diffusion of oil. The mixing ratio of the microbial nutrient to the soil is suitably in the range of 2 to 5% by weight.

The above-mentioned microbial nutrient can be mixed with healthy soil in advance and sprayed or mixed, or an appropriate amount of healthy soil can be mixed and sprayed and mixed. Because the quality effect proceeds smoothly,
It is a preferred embodiment means. In this case, the mixing amount of the healthy soil is suitably about 30 to 50% by weight.

[0010]

The hydration reaction which occurs when quicklime powder is mixed with soil is an exothermic reaction in which quicklime is converted into slaked lime as shown in the following equation. CaO + H ₂ O → Ca (OH) ₂ +15.59 Kc
al / mol

The detoxification of the oily substance by quick lime causes the volume of quick lime to increase about two times and the surface area to more than 20 times during the above-mentioned reaction, and accompanying this, the soil which has become small lumps is contained. This is based on a treatment mechanism that absorbs and fixes oil to prevent fluid dispersion. However, if this reaction occurs instantaneously, the reaction in the soil will be uneven, and the size of the soil mass particles will vary, making the above-mentioned treatment mechanism incomplete.

According to the present invention, by mixing quicklime powder whose hydration reaction has been delayed by high-temperature calcination into oil-contaminated soil, it is possible to prevent the soil from becoming large agglomerates, to make the reaction with water uniform, and to improve the oil content. Ensure absorption and fixation. Spraying and mixing the microbial nutrient with the oil outflow and diffusion suppressed in this manner effectively promotes the decomposition of oil by microorganisms in the soil. Through such a two-stage action of oil absorption and decomposition, the oil-contaminated soil is effectively reformed and purified and restored to healthy soil within a short period of time.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

Example 1 Limestone was calcined at a temperature of 1400 ° C. and then pulverized to produce quicklime powder. This quicklime powder was mixed with 1 kg of soil contaminated with mineral oil at a ratio of 50% by weight. The mixed oil-contaminated soil exothermed to 100 ° C. after about 4 minutes, and the oily soil was converted into a smooth, hydrophobic powder. Then, after mixing this soil with healthy soil, rice bran was sprayed at a ratio of 5% by weight and mixed. The treated soil was allowed to stand for 30 minutes, and the oil content was determined by the hexane extraction method. As a result, the oil was decomposed at a rate of 2 to 3 cups compared to the untreated oil-contaminated soil.
It was recognized that it had been modified.

Example 2 The same quicklime powder as in Example 1 was mixed in a contaminated soil containing a metal polishing oil at a ratio of 30% by weight. The mixed oil-contaminated soil exothermed to 80 ° C. after about 7 minutes and was converted to a hydrophobic powder. Then, 3% by weight of yeast was sprayed on the soil,
Mixed. After the treated soil was left for 30 days, the oil content was measured. As a result, it was confirmed that the oil content was almost completely decomposed, and the soil was purified and recovered.

Example 3 Example 1 was applied to 2 m ² of a sludge-like oil-contaminated soil left outdoors.
The same quicklime powder was sprayed and mixed with a power shovel. After about 5 minutes, the mixed soil exothermed to 100 ° C. and was converted to a dry powder. Next, rice bran previously mixed with healthy soil was sprayed and mixed so that the mixing ratio became 5% by weight.
After the treated soil was allowed to stand for 20 days, the oil content was measured. As a result, it was confirmed that the oil content was almost completely decomposed, and the soil was reformed into healthy soil.

[0017]

As described above, according to the present invention, any oil-contaminated soil can be efficiently removed via an oil absorption and fixing mechanism by mixing quicklime powder with a delayed hydration reaction and an oil decomposition mechanism by mixing microbial nutrients. It can be purified and restored to healthy soil. In addition, since the processing operation is simple and does not require expensive equipment and chemicals, it is useful as a simple and low-cost pollution prevention means.

Claims (2)

(57) [Claims] 1. A method for modifying oil-contaminated soil, which comprises mixing high-temperature calcined quicklime powder with oil-contaminated soil, and then mixing a microbial nutrient. 2. The method according to claim 1, wherein the microbial nutrient is at least one selected from yeast, yeast extract and rice bran.