JPS58137497A - Treatment of heavy metal-containing waste matter - Google Patents

Abstract

PURPOSE:To convert harmful heavy metal salts into a stable state and to recover noble matter, by adding an iron salt and alkaline substance to the aqueous slurry of heavy metal-contg. pulverized waste matter, filtering said slurry, and then leaving the formed filtering leftovers spontaneously standing or heat- treating the filtered residues. CONSTITUTION:Waste matter A such as dust is charged in a water tank B and changed into aqueous suspension, so as to dissolve water-soluble alkali metal salts and heavy metal salts in water. By adding iron salt C and alkali D to it, the heavy metal salts are converted into water-insoluble hydroxides with the iron salt, while the alkali metal salts are held under the dissolved condition. Thereafter, the suspension is precipitated and then separated into solid matter and a liquid by filtration using a filtering device E. The filtrate 1 is concentrated by an evaporator H, and the alkali metal slats are recovered. On the other hand, the mixture 3 of heavy metal hydroxides, etc. at the side of filtered residues G is converted into residues 4 stable even to acidic water by heat-treating it in a heat-treating device I.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for non-pollutingly disposing of hazardous wastes containing heavy metals, such as urban and industrial wastes.

In general, the residue and dust discharged when municipal waste, sludge, etc. generated from wastewater treatment processes are incinerated contain various harmful heavy metals. However, there is no established treatment method for these wastes such as dust containing harmful heavy metals, so they are currently being dumped in landfills. There is a concern that heavy metals, which are harmful to waste, may be leached out by rainwater and pollute the environment around the landfill.

For example, when examining the chemical properties of waste such as dust generated when municipal waste is incinerated, it is found that: Dust contains a large amount of water-insoluble salts as well as cedar oxides that are insoluble in water. To be.

- The main forms of oxides contained in Ail dust etc. are 5i02, Al2O5, and CaO, and the salts are alkali gold salts of NaCl, KCI, Na2SO4, and 2SO4.

■ In addition, harmful heavy metals (e.g. Cd, Pb, Zn
.

Most of Cu, Hg) are also heavy metal salts in the form of chlorides or sulfates.

In order to immobilize heavy metals using conventional methods, dust containing a large amount of these salts Y is treated at high temperatures, sintered and solidified, and then melted and solidified. is only in the state of a molten salt, and can never become a solid state of heavy metals. Furthermore, since the heavy metal salt has a very high vapor pressure, there is a strong possibility that it will evaporate and diffuse into the atmosphere during the high-temperature treatment. Furthermore, even if an attempt is made to harden the salt by directly mixing it with cement, since salts are water-bathable, they will disintegrate and turn into powder during the curing period, making it impossible to achieve the desired goal.

Wastes such as tast, which contain large amounts of alkali metal salts and heavy metals in the form of salts, are extremely polluting (this poses problems in terms of disposal).

As a means of preventing the elution of heavy metals from these highly polluting wastes such as dust, the inventor has already applied for a patent application in 1986-14.
4620 proposes a method in which Dust Y is dissolved in an alkaline aqueous solution, separated into a P solution and a residue, and this residue is subjected to high-temperature sintering (melting) or solidifying with cement. However, in order to prevent the elution of heavy metals, this method requires the generated residue to be subjected to further high-temperature treatment (requiring a heating temperature of 1,000°C or higher), which is expensive, or requires the use of expensive cement. Hime 711] and solidify it. In addition, no heavy metals were eluted in the solidified product after treatment in water with a neutral pH, but when it came into contact with acidic water, a large amount of heavy metals were observed to be eluted.

The present invention further solves these problems, enables hazardous waste containing heavy metals to be dumped without any problem under any conditions, proposes a more stable method for preventing heavy metal bathing, and at the same time The purpose of this invention is to provide an effective and inexpensive method for recovering harmless valuables that do not contain heavy metals MY.

The invention is to pulverize the waste containing heavy metals, or immerse the pulverized waste containing heavy metals in water to dissolve the heavy metal salts and alkali metal salts contained in the waste, and then add The dissolved iron salts and dissolved heavy metal salts are made into hydroxides with an alkali, and then filtered to separate into a P solution and a residue, and this residue is heated at 50 to 500°C, preferably below 6 to 300°C. This is a method for disposing of waste containing heavy metals.

To explain one embodiment of the non-invention without using drawings, first, waste such as dust is put into AY Mizumon B, stirred in water to form a suspension, and water-soluble alkali metal salts and heavy metal salts are dissolved. Dissolve in water. Next, when iron salt C and alkali D are added to the immersion liquid, the heavy metal salt in the dust and the added iron salt become hydroxides and become insoluble. - Since the alkali metal salts in the dust do not produce hydroxides, they are dissolved as they are, and since the oxides are originally insoluble, they are suspended as they are, and mixed with the heavy metal hydroxides and iron hydroxides. It becomes a suspended liquid.

Next, after the suspension is allowed to settle, it is further filtered by a filtration device E to perform solid-liquid separation.
, KCI, Na2SO4, K2SO4, etc. are transferred, and heavy metal hydroxides, iron hydroxide, 5i02, Al2O3, CaO, and other oxides remain in a mixed state on the filtration residue G side.

On the other hand, NaCl and KCI migrated to the fluid F side.

-7- The solution 1 containing alkali metal salts such as Na2SO4 and K2S mountains is recovered by evaporation and concentration using an evaporator, for example, and then used as a harmless industrial or fertilizer solution in place of power IJg or rock salt. It can be used as raw material 2.

In this embodiment, iron hydroxide, which has good sedimentation properties, and heavy metal hydroxide, which has poor sedimentation properties, are precipitated in a mixed state, and then the filtrate is
However, since the iron hydroxide incorporates heavy metal hydroxides into its crystal structure or adsorbs them and precipitates, the sedimentation rate is faster than that of heavy metal hydroxides alone, and the filterability is also good. . Furthermore, the iron hydroxide also has an adsorption effect on heavy metal ions, and because the solubility of hydroxide also adsorbs and precipitates heavy metal ions, the transfer of heavy metal ions to several p atoms is completely prevented. It can be prevented.

Car metal hydroxide, iron hydroxide on the f″ excess residue G side.

When the oxide mixture 3 is subjected to heat treatment at a Nr constant of 1 in a heat treatment apparatus I, it becomes a residue 4 that is stable even in acidic water.

In this case, the reason why the heavy metals in the perishables become insoluble is because the heavy metal ions coexist with iron ions and alkali, and a mixed hydroxide of heavy metals and iron is produced, and at this point the heavy metal hydroxide becomes hydrated. It is incorporated into the crystal lattice of iron oxide, or heavy metal hydroxides are adsorbed onto iron hydroxide.

Furthermore, it is presumed that an extremely stable crystal structure of iron and heavy metals is created by artificial heat treatment or natural release in the atmosphere for a period of 1k.

The iron salt conveniently used in the present invention is ferrous sulfate (Fe
SO4) f:ti, ferric acid (Fe2(SO4
)s) Ferrous chloride (FeCl2) Ferric chloride (Fe
In addition to chemicals such as C13), it is also possible to use ferrous chloride and ferrous sulfate, which are by-products produced in large quantities during the pickling of iron plates and the production of titanium oxide. In addition, as the alkali, sodium hydroxide A (NaOH), potassium hydroxide (KOH)
, calcium hydroxide (Ca(OH)2), ammonium hydroxide (NH40H), etc. may be used alone or in combination.

In the non-invention, the iron salts and alkaline leaves are waste components, the types of heavy metals and '! It varies depending on the situation and should be determined by experiment, but it is preferable to use 0.01 to 3 parts and 0.02 to 2 parts, respectively, per 1 part (amount) of waste. Also Ai
The temperature during heat treatment depends on the heat treatment time, waste composition, and
Approximately 500C to 500 depending on the front of the ail product
℃ range, preferably 300°C or less.

In the invention, the filtration residue is artificially heated '1
Although the objective can be achieved by leaving the product naturally in air at room temperature without heat treatment, in this case the reaction time will be considerably longer than in the case of artificial heat treatment, or iron salts or There is an advantage that the damage caused by alkali MS) does not require much force or a thermal mechanical heat treatment equipment.On the other hand, the heat treatment time or natural standing time is longer than the treatment Y.
Although it differs depending on the M degree, the ingredients of the 1-year-old food, the song of the added food, etc., it is sufficient to select the minimum necessary time, preferably 10 minutes or more.

In addition, in these series of steps, it is desirable that the waste such as dust be a saturated solution of the alkali metal salt contained in the water. That is, since the recovery of these alkali metal salts requires, for example, an evaporation polarization process, the amount of water for immersion can be kept to a safe minimum. It is efficient to use a saturated aqueous solution with −f. In addition, in the case where the waste such as waste is discharged from the incineration equipment, the waste heat of the incineration equipment
For example, the P solution may be evaporated by using the waste from J, and the filtration residue may be heat-treated.

In addition, the P liquid does not contain any harmful heavy metals.
It is also possible to discharge the alkali metal salts as they are without recovering them, and in addition, when the waste is discharged from the incinerator, it is possible to discharge the waste from the incinerator itself. '1. It is also possible to dispose of the P liquid by absorbing water into the incineration ash, which contains no filtration water and may be scattered during handling.

In addition, the residue produced by the present invention after heat treatment/leaving is stable even in acidic water, and hardly any heavy metals are leached, but it is somewhat brittle in terms of mechanical strength, so it cannot be solidified easily when used with a ladle. (For example, p4 1st to aggregate etc.)
In order to achieve this, if the product is sintered and melted at a higher temperature (1000°C or higher), 5i02 and A will be contained in the residue.
12O3, CaO, Fe2O3, etc.-11- are formed as melts and become slender, resulting in assimilates with extremely high mechanical strength. Furthermore, since the residual crushed carcass does not contain Class 14 substances that may have an adverse effect on cement, it can be made into a solidified product with high mechanical strength by using the same Boltland Cementora. In other words, the residue after heat treatment or natural standing may be mixed with cement, or the filtration residue may be directly mixed with cement y to obtain a natural number t.

According to the method of the present invention, harmful and unstable heavy metal salts are converted into stable oxide forms and then processed in a form with low energy costs. KCI, Na2SO4゜K2S0
4) There is a useful benefit in that it can be used to accurately prevent the elution of heavy metals through adjacent processing that efficiently separates and recovers them.

Next, examples of the present invention will be shown.

Example 1 The dust discharged from the air dyeing machine of a municipal waste incineration plant contains 3.3% of 8102 as an oxide.

Al2O51.5%, CaO3.0% are alkali 11
NaC 123.3%, KCI 9.5%,
It contains 11.0% Na2804, 33.0% K2SO4, and its low heavy metal salts include ZnCl2 and ZnSO4, totaling 2.1%.

Total of 0.5% of pbct2 and pbso4, Cu
Total of Cl2 and CuSO4 0.2%, CdCl2 and c
A total of 0.05% of ctso4 was contained. This dust Y was immersed in water to form a saturated bath solution of the alkali metal salt, and then FeSO4 was added as an iron salt at 160 g per ky dust.
, Ca(OH)2Yl 10g was added and stirred to create a mixture of heavy metal hydroxide and iron hydroxide. The mixture was then sedimented and filtered. Hardly any heavy metals were observed to be eluted from the P solution at this time. Next, the filtration residue was heat-treated at 100° C. for one hour using a heating furnace. After pulverizing the treated sample, an elution test (method according to Environment Agency Notification No. 13) was conducted using water with a pH of 7. All heavy metal eluate concentrations were below 0.1 p-, meeting the standards stipulated by the Prime Minister's Office Ordinance. It was below the value. Furthermore, in order to examine the leaching properties of heavy metals in acidic conditions, the above sample was used at pH 4.
Seven elution tests were conducted in a liquid controlled to As a result, the heavy metal concentrations in the eluate -16- were ZnO, 3ppm, Pbo, 5ppm, and CuO.
, 11) Illll, Cd 2 O, 1pp, and there was almost no elution of heavy metals, which was below the standard value. - As a result of evaporation steel making of 10,000, rff, NaCl, KC
A very pure white mixture of I, Na2SO4, and 2SO4 was obtained.

Example 2 15% by weight was added to the filtration residue before 710 heat in Example 1.
Portland cement FY was added and kneaded for 5 minutes using a kneader, and then an extrusion molding machine was used to obtain a short rod-shaped product with a diameter of 10 rr/An. When this molded product was left in the air for 10 days to cure, it was found to be a strong molded product with -axial compression g1 degree of 45 kiJ. After pulverizing this molded product, an elution test (method according to Environment Agency Notification No. 13) was conducted using water with a pH of 7, and the concentrations of heavy metals in the eluate were all below 0.1, which was below the standard value specified by the Prime Minister's Office Ordinance. Met. Furthermore, in order to examine the elution properties of heavy metals in acidic conditions, we used the Ail sample.
An elution test was attempted in a solution controlled at H4. the result,
The heavy metals in the bathing solution were Zn 0.591m, P'b 0.
8flllll, Cu 0.2DPII, CdO,
159-, all of which were below standard values.

-14-

[Brief explanation of the drawing]

The drawing is a system explanatory diagram of the method of the present invention. A: Waste, B: Water tank, C: Old
・Iron salt, D...alkali, E...filtration device, F...P liquid, G...filtration residue,
H... Evaporation device, ■ Old... Heat treatment device, J...
...Waste heat, 1...Alkali metal salt-containing solution, ?・・・・・・
・Fertilizer raw materials, 3...mixture, numbers, old...residues. Patent applicant Go Hatayama, patent attorney representing Ebara Infilco Co., Ltd. - Patent attorney Sen 1)
Minor Procedural Amendment 1932, October 21, 1939 2. Name of the invention Method for treating heavy metal-containing waste 3. Relationship with the case of the person making the amendment Patent applicant address (residence) 4. Agent preferably 300℃ Claims characterized by ``heat treatment with the following: t Finely powdered waste containing heavy metals or finely powdered waste is immersed in water to form a slurry, and iron salt and an alkaline substance or an aqueous solution thereof are added to the slurry. A method for treating heavy metal-containing waste, which is characterized in that the mixture is then stirred and mixed, then treated in a furnace to separate it into a ν liquid and a residue, and the resulting residue is allowed to stand naturally. 2. The process of soaking the waste in water to make a slurry,
The waste treatment according to claim 1, wherein 0.01 to 3 parts of iron salt and 0.02 to 2 parts of alkali are added to 1 part (by weight) of waste. Method. 4. The waste treatment method according to claim 3, wherein in the dipping step, heavy metal hydroxide and iron hydroxide are mixed to form a suspension, which is then subjected to sedimentation separation treatment. A. The waste treatment method according to claim 1 or 2, wherein the residue is subjected to sintering and assimilation treatment as it is. 5. The waste treatment method according to claim X or j, wherein the residue is left to stand naturally after being solidified with cement. Difference: The waste according to claim 3, claim 3, claim 1, or claim 1, wherein the P solution is disposed of by collecting alkaline gold maple salt and absorbing water into incineration ash. Processing method. that's all

Claims (1)

[Scope of Claims] 1. After soaking imitation powdered slivers or finely powdered waste leaves containing heavy metals in water to form a slurry, and adding iron salt and an alkaline substance or a water bath solution thereof to the slurry, A method for treating car metal-containing waste slag, which comprises stirring and mixing, then Y-filtering the mixture to separate it into a P solution and a residue, and leaving the filtered residue to stand naturally or subjecting it to heat treatment. 2. The waste treatment method according to claim 1, wherein the heat treatment step is performed within a crystallinity range of 50°C to 500°C. 3. The process of soaking the waste in water to make a slurry involves adding 0.00% iron salt to 1 part (weight) of the waste. 1 to 3 parts of O 0.02 to 2 parts of alkali I
The waste treatment method described in item 1 or 2 of the scope of ¥j. 4. The disposal according to claim 3, wherein the dipping step is a step of mixing heavy metal hydroxide and iron hydroxide to form a suspension of milliliter, followed by sedimentation and separation treatment. Material processing method. 5.) The waste treatment method according to item 3 or 4, wherein the residue is sintered and solidified as it is or after heat treatment. 6. The waste treatment method according to claim 3 or 4, wherein the residue is left to stand naturally after being solidified with cement. 7. The waste according to claim 3, 4, 5, or 6, wherein the p-liquid collects the alkali metal salt and then absorbs water into incineration ash to be disposed of. Processing method.