JPS5814840B2 - Method for detoxifying industrial waste containing heavy metals - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for detoxifying industrial waste containing heavy metals.

In recent years, with the development of industry, pollution problems such as water pollution and air pollution have come into the spotlight, and related factories, which are the sources of pollution, are steadily producing results by installing pollution removal equipment.

However, on the other hand, the disposal of industrial waste containing hazardous heavy metals generated from these facilities, etc. is subject to amendments to the Waste Disposal and Cleaning Act (revised June 16, 1976, Law No. 68). This has become a very serious problem, as seen in the strengthening of the system.

Normally, industrial waste containing hazardous heavy metals is disposed of in a landfill, but at that time, industrial waste is The standards set forth in the Prime Minister's Office Ordinance Establishing Judgment Standards for Hazardous Industrial Waste (Prime Minister's Office Ordinance No. 3, revised March 14, 1978) must be met.

These heavy metal-containing industrial wastes contain almost all metals, and these metals are in the form of insoluble oxides and soluble compounds such as sulfates, nitrates, and chlorides.

In particular, in addition to various heavy metals, the ash collected by dust collectors, flue gas desulfurization by-products, and flue gas denitrification by-products discharged from heavy oil combustion factories, as well as the ash collected by dust collectors and alkaline smoke washing wastewater from garbage incineration plants, are ,
Since it contains large amounts of sulfates, nitrates, chlorides, etc. of Ca, Mjj, NH4, Na, heavy metals are likely to be eluted, so caution is required.

Conventional methods for treating industrial waste containing heavy metals include concrete solidification method, asphalt solidification method, plastic melt solidification method, calcination solidification method, and dispersion of incinerated fly ash in water or acidic aqueous solution to adjust the pH to 40 to 7.0. A treatment method for adjusting the soluble heavy metals within the range of
No. 165) etc.

However, a stable and reliable treatment method has not yet been established for any of these, and the treatment process and operations are complex, and equipment costs and operation and maintenance costs are high, so some are left untreated or some are left untreated. Due to the incompleteness, there is a problem in securing a landfill site due to concerns about secondary pollution.

In particular, the concrete solidification method, asphalt solidification method, plastic melt solidification method, etc. consume large amounts of cement, asphalt, plastic, etc., resulting in very high operation and maintenance costs. However, methods such as sintering have the disadvantage of being inefficient in transportation and use of landfill sites.Furthermore, methods such as sintering have the disadvantage of generating secondary pollution due to the sublimation and scattering of heavy metals due to heating to high temperatures. There is.

Furthermore, regarding the treatment method of JP-A-53-12165, the pH is 40 to 7. 0 is ineffective because soluble heavy metals cannot be sufficiently transferred to the liquid phase, and even after solid-liquid separation, residual fly ash contains adhering water containing dissolved heavy metals, so it must be washed. A large amount of water is consumed for washing, and even if the water is thoroughly washed, heavy metals will be re-eluted, and heavy metals must be removed from the separately separated heavy metal-containing water and a large amount of washing water using a coagulation method or the like.

As described above, not only is there no treatment effect, but the treatment process and operation are complicated because the separated water is treated as wastewater, and the equipment cost and operation and maintenance cost are very high.

On the other hand, in viscose rayon factories, from the sulfurization process to the scouring process, particularly from the spinning process, exhaust gases containing harmful substances such as hydrogen sulfide and sulfuric acid mist are generated in addition to carbon dioxide, and these gases are released directly into the atmosphere. and air pollution,
Unfavorable in terms of environmental conservation.

Therefore, it is well known that this exhaust gas is washed with a caustic soda solution in a scrubber to remove harmful substances from the exhaust gas, but the waste fluid generated at this time is soda sulfide, sodium hydrogen sulfide, etc. Because it contains toxic substances, it cannot be released as is, but currently it is burned and turned into gaseous substances such as sulfur oxides, which are then treated with flue gas desulfurization equipment, but this is also economically viable and environmentally friendly. Not good.

The present inventors have provided a highly efficient detoxification treatment method for heavy metal-containing industrial waste that can reliably and stably detoxify the waste by solving these shortcomings and reducing equipment costs and operation and maintenance costs. As a result of intensive research with the aim of
We found that all of the above objectives could be achieved and applied for a patent.However, as a result of further research, we found that using the wastewater produced by-product from the above-mentioned viscose rayon factory instead of the alkaline agent is equivalent to or better than the alkaline agent. The present invention has been completed by discovering that the above-mentioned effects can be obtained and that the waste liquid produced as a by-product from the above-mentioned viscose rayon factory can be treated at the same time.

That is, the present invention applies slurry-like industrial waste containing a soluble heavy metal compound and an insoluble heavy metal compound, in which some or all of the soluble heavy metal compound is dissolved in a liquid, to a wet spinning process in a viscose rayon factory. This is a method for detoxifying industrial waste containing heavy metals, which is characterized in that the soluble heavy metal compounds are insolubilized by adding a waste liquid obtained by washing the gas generated from the above with a caustic soda solution.

According to the present invention, a soluble heavy metal compound in slurry-like industrial waste can be made into a very stable insoluble substance by insolubilizing it in the presence of an insoluble heavy metal compound.

This extremely stable insoluble substance differs from the precipitate of conventional coagulation-precipitation methods in that no heavy metals are eluted.

Although the detailed reason is not clear, it is likely that unlike the conventional coagulation-precipitation method, in which heavy metal hydroxides or heavy metal sulfides are formed into simple compounds, the slurry-like industrial waste in the present invention is insoluble. The heavy metal compound, the soluble heavy metal compound, and the component contained in the viscose rayon factory effluent react with each other, and the component contained in the viscose rayon factory effluent acts as a crosslinking agent between the insoluble heavy metal compound and the soluble heavy metal compound, and as a whole, This is thought to be due to the formation of a very stable, insoluble, relatively high-molecular complex compound.

Heavy metal-containing industrial waste in the present invention includes, for example, incinerated ash from garbage incinerators, ash collected by dust collectors, alkali smoke waste water concentrate, sludge from plating factories, ash collected by dust collectors from heavy oil combustion plants, and wastewater Examples include smoke desulfurization byproducts, flue gas denitrification byproducts, sludge from water treatment plants, and sludge from sewage treatment plants.

This heavy metal-containing industrial waste contains insoluble heavy metal compounds, soluble heavy metal compounds, soluble alkali metal compounds, soluble alkali metal compounds, and the like.

Examples of the soluble heavy metal compound in the present invention include:
Examples of insoluble heavy metal compounds include chlorides, sulfates, nitrates, and sulfites of zinc, cadmium, nickel, manganese iron, chromium, mercury, copper, etc., and examples of insoluble heavy metal compounds include oxides, hydroxides, and carbonates of the above heavy metals. Examples include salts and sulfides.

Examples of soluble alkaline earth metal compounds include chlorides and sulfates of calcium and magnesium; examples of soluble alkali metal compounds include chlorides, sulfates, and sulfates of sodium and potassium. can be mentioned.

In the present invention, slurry-like industrial waste refers to heavy metal-containing industrial waste that has a concentration that is fluid enough to be stirred, and usually has a concentration of 2 to 33% by weight. refer to things

In this case, if the industrial waste is solid, water may be added to it to form a slurry.

In addition, alkali smoke washing waste water concentrate from garbage incinerators is also included in the slurry-like industrial waste referred to in the present invention.

The industrial waste targeted by the present invention is a slurry-like industrial waste containing a soluble heavy metal compound and an insoluble heavy metal compound, and the soluble heavy metal compound is dissolved in a liquid.

For example, if industrial waste is solid, water is added to it to make it into a slurry, and the slurry industrial waste is then adjusted to pH
The soluble heavy metal compound may be dissolved in the liquid by adjusting, heating, or stirring.

The selection of pH adjustment, heating, and stirring can be carried out individually or in combination, but it varies depending on the type of heavy metal-containing industrial waste, the heavy metal content concentration, and pH.

For example, sludge containing heavy metals at a pH of 1.3 in a plating factory can completely dissolve soluble heavy metal compounds with just 2 hours of stirring;
The soluble heavy metal compounds in the flue gas desulfurized heavy metal-containing by-product sodium sulfate can be completely dissolved by simply heating it at 100°C for 1.5 hours.

Furthermore, the pH of heavy oil combustion plants 6. The collected ash containing heavy metals in the multi-cyclone dust collector in step 1 was adjusted to pH 3 with hydrochloric acid. The soluble heavy metal compound can be completely dissolved by adjusting the temperature to 0, raising the temperature to 80°C, and stirring for 2.5 hours.

The pH here is adjusted to 1 with a normal acid or alkali.
The pH is adjusted to a range of 7 to 7, preferably a range of 2 to 6.

Regarding heating, it is heated to 60 to 120'C using heated steam, electric heat, heavy oil, or other factory waste heat, and preferably to 80 to 100''C.

Further, stirring is usually carried out by mechanical stirring, but other methods such as air stirring, kneading, shaking, etc. can also be carried out.

The method of the present invention is to insolubilize soluble heavy metal compounds in slurry-like industrial waste and make it harmless, by adding the viscose rayon factory wastewater described above in the presence of the insoluble heavy metal compounds. conduct.

The pH of this slurry-like industrial waste is generally in the range of 2 to 6, and it is preferable to add viscose rayon factory effluent in an amount such that the pH does not exceed 10.

In particular, it is preferable to add viscose rayon factory effluent in an amount such that the pH becomes 6 to 9.

If the pH exceeds 10, amphoteric metal compounds such as zinc, chromium, and lead may be redissolved, and a large amount of viscose rayon factory effluent is consumed, which is uneconomical.

The amount of viscose rayon factory effluent used varies depending on the type and pH of the slurry industrial waste, but for example, 10 to 800 kg of viscose rayon factory effluent is used per ton (dry weight) of slurry industrial waste. It is.

The viscose rayon factory effluent used in the present invention is:
As mentioned above, it is obtained by washing the gas generated from the wet spinning process etc. with a caustic soda solution, and its composition is, for example, 40 to 2009/l of soda carbonate,
Sodium sulfide 30~180g/l'e nitric acid 50~150
&/l, sulfite sodium 20-50 g/l, sodium hydrogen sulfide 20-60Vfj, sodium sulfate 10-40
g/l, etc., and the pH is approximately constant at about 13 to 14, but the present invention is not limited to these composition ratios.

In addition, whether the slurry-like detoxified material treated in this way completely satisfies the landfill disposal standards and wastewater standards for both solid and liquid, or if it is necessary to reduce the weight and volume of the slurry-like detoxified product. Precipitation, filtration, dehydration, depending on
It is best to perform solid-liquid separation by concentration, drying, etc.

As a result of the elution test in accordance with the Environment Agency Notification No. 13, the solids can be disposed of as they are, as they fully satisfy the standard values stipulated in the Prime Minister's Office Ordinance No. 3. In order to meet the wastewater standards stipulated by the revised Prime Minister's Office Ordinance No. 3), wastewater containing heavy metals is usually discharged directly into public water bodies or can be reused within factories, which is extremely effective from the standpoint of environmental conservation. This is a method for detoxifying industrial waste.

According to the present invention, by using the wastewater produced as a by-product from the above-mentioned viscose rayon factory, heavy metal-containing industrial waste can be stably and reliably converted into a detoxified product that does not elute heavy metal compounds at a lower cost than using alkaline chemicals. At the same time, the above-mentioned waste water from the hiscose rayon factory can be treated at the same time, and the separated water discharged despite the wet method can also be discharged without treatment, so there is no need to worry about secondary pollution.

In addition, because the process and operation are simple and chemical consumption is low, equipment costs and operation and maintenance costs are much lower than concrete solidification methods, etc., and since it is a wet method, there is no need for molding, which reduces the transportation unit. This makes it possible to use landfill space more effectively.

Next, the present invention will be specifically explained using examples.

Example 1, Comparative Example 1 Nickel 68m9/kg, Manganese 9 20Tn9/k
g, zinc 3 90 0 0tn9/kg, cadmium 2
70y/kg, total chromium 320mg/kg, lead 12
000mg/kg1 total mercury 93mg/kg, arsenic 16m
g/'mg, copper 3500tny/'Kg, iron 4 200
07V/kg, silicon 17000mg/kg, aluminum 48000mg/IJ, potassium 1.2 0 0 0
0mgkg, calcium 80000mtii/kg,
Na1.Rium 5 20 0 0779/kg, 7gnesium 14000mg/kg, sulfate ion 1450000
mg/Kg, chlorine ion 1120000mg/kg, cyanide 0.03mg/kg, organic phosphorus o. 0 4ill9/
kg, PCB0.002mLI/kg, moisture 0.8
Ash collected by a dry electrostatic precipitator at a garbage incineration plant containing 2 wt% of soluble heavy metal compounds and insoluble heavy metal compounds 1
500 ml of water was added to 0CBi' to form a slurry, and after stirring for 1 hour, the pH was measured and found to be 6.4.

While stirring, add 5 ml of 63% sulfuric acid.
H was adjusted to 5.0.

Next, soda carbonate 8o & yJ1 soda sulfide 3 3El
/13, Glauber's salt 64jJ/l! , Sodium sulfite 32&/'
l, sodium bisulfide 2 1 &/l, sodium thiosulfate 16
22 ml of the waste liquid obtained by washing the gas generated from the wet spinning process of a viscose rayon factory with a caustic soda solution was added to adjust the pH to 7.0.

Furthermore, this is centrifuged and dehydrated at 15,000 rpm, 5
Solid-liquid separation was performed by dehydration for a minute.

The solid material was subjected to a dissolution test according to Environment Agency Notification No. 13.
On the other hand, the dehydration filtration was analyzed according to JISK-0102.

For comparison, instead of waste water from a viscose rayon factory, 36 m of hexavalent sodium sulfide was added at a pH of 7.0.
The same procedure was followed except that 1 was added.

The results are shown in Table 1.

From Table 1, it is clear that Example 1 and Comparative Example 1 satisfy the landfill treatment standards for solids and the drainage standards for dewatered filtrate, and for both standards, Example 1 is better than Comparative Example. It is clear that this is superior to 1.

Example 2, Comparative Example 2 Cadmium 500m9/9 as soluble heavy metal compound
(Cd Cl22.5 H20 1 0 2 om9
/kg), mercury 500mg/kg (HgCl2
680mg/kg), cadmium 500cm/kg as insoluble heavy metal compounds (cao570cm/kg was used), mercury 500m? /kg (Hg0 540mg/
kg), calcium 500 m&/kg (CaCl26H,,0
2730mg/kg), calcium 5001V/kg (Ca
0 570m? /kg), sodium i 0 0 01ru? as a town-soluble alkali metal compound? /kli
Hydrochloric acid was added to 100 g of slurry-like model industrial waste prepared with reagents with pH = 6.1 containing i' (NaCd 2 5 4 omy/kg) to adjust the pH to 3.0.
Adjusted to.

Next, the viscose rayon factory effluent was adjusted to have a pH of 7.0 (composition is the same as in Example 1).

) was added, and solid-liquid separation was performed by filter paper filtration. The solid substance was subjected to a dissolution test according to Environment Agency Notification No. 13, and the filtrate was analyzed according to JISK-0102.

For comparison, the same process was carried out except that the insoluble heavy metal compound was not contained.

The results are shown in Table 2.

It is clear from Table 2 that Example 2 is a much more stable insoluble substance than Comparative Example 2.

Example 3 Vanadium 720mg/kg, Nickel 1800mg/
kg, iron 860cm/kg, copper 15mg/yu, zinc 70m
q/Kg, aluminum ■/yu, lead 1 57Q/Kl7
1 Cadmium 0.2mg/U, total chromium 16mg/kg
, Manganese tsm9/k&, Arsenic 1.9■/kg, Total mercury 0.14m9/U, Magnesium 3 20m9/kg
, Calcium 1000rn9/}1, Glauber's Salt 239/'k
g, ammonium sulfate 3009/kg, moisture 0.60 wt%, flue gas desulfurization by-product ammonium sulfate 100 g from a heavy oil combustion factory containing a mixture of soluble and insoluble heavy metal compounds, etc., and 400 ml water.
was added to make a slurry, heated to 100°C by steam heating, stirred for 2 hours, and measured for pH, which showed a pH of 3.
It was 2.

While stirring this liquid, 28 rrtl of viscose rayon factory waste liquid (composition is the same as in Example 1) was added to adjust the pH to 8.0, and solid-liquid separation was performed by filter paper filtration.

The solid substance was subjected to an elution test according to Environment Agency Notification No. 13, and the filtered water was analyzed according to JISK-0102.

The results are shown in Table 3.

Example 4 Copper 26■/l, iron 98■/l, lead 200■/l, total
Mu14m9/lj, zinc 12000m9/l, cadmium L7m9/l, total mercury 287V/71 arsenic 0.
27n9/l, Aluminum 3 20mti/C Nickel 40m9/13, Tin 16■/13,77ga 71Qm
y/4 Calcium 2900my/#,? Gnesium 50
0ynq/l, sodium 66000m9/l
, 12,800 m of suspended solids? /l of soluble heavy metal compounds and malfunction (pH 6.2 with soluble heavy metal compounds etc.)
2 500 ml of concentrated liquid of alkaline smoke washing wastewater from garbage incinerator
Stir for hours.

Next, 52 ml of viscose rayon factory waste liquid (composition is the same as in Example 1) was added so that the pH was 80, and the mixture was stirred for 1 hour.

This was allowed to stand for 3 hours to precipitate, and then separated into solid and liquid.

The solid matter was subjected to an elution test according to Environment Agency Notification No. 13, and the precipitated supernatant water was analyzed according to JISK-0102.

The results are shown in Table 4.

Example 5 Total chromium 59ml? /kg, hexavalent cum 0.0 8m4
7/Iv, cadmium 38 cycles/yu, lead 2200mg/k
g, copper 5200779/kg, zinc 5100mg
/kg, Iron 3300 -m9/Kg, Manga 7 1 0
00mQ/kg, tin 42omq/Ky, nickel 13
0mg/yu, arsenic 0.9mg/kg, total mercury 1.4m9
/kg, alkylmercury 0. O 0 27n9/kg1 aluminum 1 5 20 0 01n9/Ig, silicon 4
250001n9/kg, sodium 9 s o o
o1rU? Ag, potassium 34000mg/kg, calcium 48000/yu, magnesium 2700my
/yu, sulfate ion 42000mg/kg, chloride ion 3
A slurry is made by adding 300 ml of water to 100 g of incinerated ash from a garbage incineration factory, which contains a mixture of 9000 mg/kg of cyanide, 0.06 mg/kg of cyanide, 0.03 mg/kg of organic phosphorus, and 5.9 wt% moisture of soluble and insoluble heavy metal compounds. After stirring for 1 hour, the pH was measured and the pH was 10.2.
Met.

While stirring the mixture, 20 rnl of 10% nitric acid and 20 ml of 10% hydrochloric acid were added to adjust the pH to 6.1.

Next, the viscose rayon factory effluent was adjusted to have a pH of 8.5 (composition is the same as in Example 1).

) and then concentrated and dried in an evaporator using steam heating.

The solid material was subjected to a dissolution test according to Environment Agency Notification No. 13.

The results are shown in Table 5.

Claims (1)

[Claims] 1. Slurry-like industrial waste containing a soluble heavy metal compound and an insoluble heavy metal compound, and in which some or all of the soluble heavy metal compound is decomposed in a liquid, is treated with a wet process at a viscose rayon factory. 1. A method for detoxifying industrial waste containing heavy metals, which comprises adding a waste liquid obtained by washing gas generated from a spinning process etc. with a caustic soda solution to insolubilize the soluble heavy metal compounds. 2. Claim 1, wherein the slurry-like industrial waste is a slurry-like industrial waste obtained by adding water to solid industrial waste to dissolve some or all of the soluble heavy metal compounds.
Treatment method described in section. 3. The treatment method according to claim 1 or 2, in which the waste liquid is added in an amount such that the pH does not exceed io. 4. The treatment method according to claim 3, wherein the waste liquid is added in an amount such that the pH becomes 6 to 9.