JPS6043193B2 - Method for detoxifying industrial waste containing hazardous substances - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detoxifying industrial waste or contaminated soil containing harmful substances.

In recent years, large amounts of industrial waste and contaminated soil, such as metal scraps, glass scraps, ceramic scraps, slag, sludge, soot, and rice husks, which contain hazardous substances such as heavy metals, have been generated from various business establishments, etc., and their disposal is a pollution-related issue. This is an extremely important issue in terms of countermeasures.

A large amount of industrial waste is finally disposed of by landfilling, ocean dumping, etc., but in either case, it is necessary to detoxify the waste so that the harmful substances contained in the waste do not leach out. Criteria for determining hazardous substances are established by the Prime Minister's Office Ordinance (February 17, 1971, Prime Minister's Office Ordinance No. 5, etc.) that establishes criteria for determining waste. It was quite difficult in terms of workability and economy to carry out elution prevention treatment and clear the above criteria.

Lead (Pb), cadmium (Cd), etc. are harmful substances.
Zinc (Zn), copper (Cu), hexavalent chromium (Cr'゛),
It is extremely difficult to completely detoxify waste containing heavy metals such as mercury (Hg), alkyl mercury, arsenic (As), cyanide (CN), or even fluorine (F). It was considered difficult. The present inventors have conducted various studies on methods for preventing the elution of large amounts of industrial waste containing hazardous substances and making them harmless. As a result, we have found that by treating waste with an aqueous solution of a specific compound, a large amount of the substances to be treated can be removed. The present invention has been completed based on the discovery that it is possible to efficiently render the molecule harmless.

That is, the detoxification method of the present invention is characterized by treating industrial waste or contaminated soil containing toxic metals and fluorine as hazardous substances with an aqueous solution containing iron chloride or iron sulfate, a sulfur-containing compound, and a calcium compound. .

Here, the harmful substances contained in industrial waste or contaminated soil include lead (Pb), cadmium (Cd), and zinc (Z).
n), copper (Cu), hexavalent chromium (Cr6*), mercury (H
g), alkyl mercury, metals such as arsenic (As), cyanide (CN), PCB, organic chlorine, etc. These harmful substances are treated to prevent elution with an aqueous solution containing iron chloride or iron sulfate, and ion-containing compounds. If fluorine (F) is further included as a harmful substance, it is rendered harmless by being treated to prevent elution with an aqueous solution containing iron chloride or iron sulfate, a sulfur-containing compound, and a calcium-containing compound.

The types of industrial waste may be in the form of metal scraps, glass scraps, ceramic scraps, slag, sludge, soot, dust, rice husks, contaminated soil, powder, crushed granules, slurry, etc.
If the shape is not such, the detoxification method of the present invention can be applied after pretreatment such as crushing or crushing. The treatment liquid of the present invention is an aqueous solution containing iron chloride or iron sulfate, a sulfur compound, and a calcium compound.

As the iron chloride, ferrous chloride is preferable, but a small amount of ferric chloride or the like may be mixed.

As such an aqueous solution containing iron chloride, aluminum etching waste liquid or the like can be used. As the iron sulfate, ferrous sulfate is preferably used. As the sulfur compound, sodium sulfide, NaHSOJl powdered sulfur, thiourea, etc. can be used, but it is particularly preferable to use sodium sulfide.

As the calcium compound, calcium chloride, calcium oxide, calcium hydroxide, cement, etc. can be used, but it is particularly preferable to use calcium chloride. The above-mentioned iron chloride solution or iron sulfate solution is 2 to 25% (wt%, same hereinafter), preferably 5 to 20%, based on the waste in terms of 20% aqueous solution, and the sulfur compound is 0.1 to 5%, preferably 0.
．． An aqueous solution can be prepared and used by blending the calcium compound in an amount of 2 to 2%, preferably 0.1 to 5%, and preferably 0.1 to 2%.

An appropriate method for processing waste can be selected depending on the form and amount of waste, processing equipment, processing time, etc. For example, a method in which dust is piled up in a pelletizer and granulated by spraying the aqueous solution of the present invention. can be taken. Ultimately, the treatment method may be any method that allows sufficient contact between the waste and the aqueous solution.

Although the detoxification treatment method of the present invention is sufficiently effective when carried out at normal temperature and normal pressure, conditions such as heating and pressurization may be added as desired.

The detoxification treatment method of the present invention is preferably carried out by controlling the pH of the waste after 4 days of treatment to 6.5 to 9.5, preferably 7.0 to 9.0, that is, around neutral and weak alkalinity. It is preferable to do so.

PH may be controlled using hydric soda, slaked lime, cement, etc. Waste is processed into pellets,
It can be converted into a form suitable for final disposal, such as concrete solidification or slurry. The method for detoxifying industrial waste of the present invention is a method with excellent workability and economy, which can prevent the elution of a large amount of waste containing hazardous substances and detoxify it in one step. Lead (Pb) as a substance
, cadmium (Cd), zinc (Zn), copper (Cu), 6
Valent chromium (6 Cr, mercury (Hg), alkylated mercury,
We treat waste that contains arsenic (, As), cyanide (CN), PCBl organic chlorine, etc., and fluorine (F), etc., and make all hazardous substances harmless below the criteria specified by government ordinance. can do.

Moreover, according to this method, a wide variety of wastes can be easily rendered harmless, and its application range is wide.

Next, examples of the present invention will be described.

Example 1 5 tons of dust generated from a roasting furnace as industrial waste
Due to time constraints, it was introduced onto the pelletizer.

On top of this, an aqueous solution of 20% ferrous chloride, 1% calcium chloride, and 4% sodium sulfide solution was sprayed from separate nozzles to prevent elution. The usage amount is 20% ferrous chloride liquid 750k9/hour, soda sulfide 40k9/hour,
Calcium chloride was 42.5k9/hour. The results of component analysis of the dust before treatment and analysis of the eluate after treatment are shown in Table 1 below.

The eluate was analyzed by the method shown below.

Preparation of sample liquid: The sample liquid is prepared by mixing the sample and solvent as follows.

1 Hydrogen ion concentration index of the solvent If the solvent is to be disposed of in the ocean or in a sea-surface landfill, the hydrogen ion concentration index should be 7.8 to 8.3, taking into account the pH of the seawater, and in the case of land landfill disposal, the hydrogen ion concentration index should be 5. .8~6
．． 3 by adding sodium hydroxide or hydrochloric acid to pure water.

2 Ratio of sample and solvent The ratio of sample to solvent is determined as shown in the table below.

As shown in this table, the weight/volume ratio of the sample to the solvent is sometimes 10%, and sometimes the solid content in the mixed liquid is 3%.
The solid content is determined by intentionally adding water during the judgment test when disposing of waste that easily contains water, such as dirty sewage, into the ocean or in a sea-surface landfill for which there are no disposal standards regarding water content. This is to prevent a loophole that would effectively reduce the amount of sample and thus reduce the concentration of harmful substances eluted.
Elution operation: Keep the sample flow at room temperature (approximately 2) and normal pressure (approximately 1)
Shake continuously for 6 hours using a shaker (shaking frequency: 200 reciprocations per minute, shaking width: 4-5c!n) at atmospheric pressure).

Preparation of test solution: Filter the sample solution obtained by elution using a glass fiber filter vapor with a pore size of 1 micron (if filtration is extremely difficult, filter the solution at a rate of 30 (4) per minute).
After centrifuging the two powders by rotation, use the supernatant/filtrate as the test solution.

Comparative Example 1 The same industrial waste was treated in the same manner as in Example 1, except that the calcium chloride solution was not used.

The analysis results of the eluate after treatment are shown in Table 1. Example 2
As industrial waste, 1 ton (t) of mercury-containing glass waste generated from the fluorescent lamp manufacturing process was put into a cement roll mixer.
), add 50 kg of 4% sodium sulfide solution while mixing, and then add 100 kg of 20% ferrous chloride solution.

Furthermore, 100k9 of cement was added and mixed thoroughly. The results of the component analysis of the glass waste and the analysis of the eluate after treatment are shown in Table 2 below.

Comparative Example 2 The same industrial waste was treated in the same manner as in Example 2, except that cement was not used.

The analysis results of the eluate after treatment are shown in Table 2. Example 3 A 24% ferrous sulfate solution, a 5% calcium hydroxide aqueous dispersion, and a 4% sodium sulfide solution were sprayed onto the same industrial waste as used in Example 1 using three separate nozzles for elution. Preventive treatment was carried out.

The amount used is 750 kg/hour of 24% ferrous sulfate solution, 40 kg/hour of sodium sulfide, and 15 kg/hour of calcium hydroxide aqueous dispersion.
It was 0 kg/hour. The analysis results of the eluate after the above treatment are shown in Table 1.

Claims (1)

[Claims] 1. A method for detoxifying industrial waste or contaminated soil, which comprises treating industrial waste or contaminated soil containing toxic metals and fluorine as hazardous substances with an aqueous solution containing iron chloride or iron sulfate, a sulfur compound, and calcium.