TWI530471B - A method for solidified heavy metals and chloride ions of hazardous waste incineration fly ash - Google Patents

Description

Fixed heavy waste incineration fly ash in the form of heavy metals and chloride salts law

The invention relates to a method for treating incineration fly ash of hazardous waste, in particular to a treatment method for fixing heavy metal and chlorine salt in incineration fly ash of hazardous waste.

With the development of Taiwan's economy and the improvement of the living standards of Chinese people, the improvement of personal consumption power and mass consumption have become a common lifestyle. Under the influence of this lifestyle, the annual garbage production of the Chinese people has reached a record high. Because Taiwan is narrow and dense, the burial method cannot meet the demand of Taiwan's garbage disposal for a long time. Therefore, the urban waste treatment is mainly changed from burial to incineration, with the concept of reducing capacity and reducing hygiene. However, the incineration waste will still produce a certain proportion of commercial waste such as incineration fly ash and incinerated bottom slag, and the incineration fly ash will exceed the hazardous wastes by the concentration of heavy metals such as lead and cadmium. It is considered to be hazardous waste and cannot be disposed of by landfill.

At present, the method of treating the incinerated fly ash is mainly to use Portland cement to carry out the immobilization/stabilization of the incineration fly ash and then to bury it. However, after the cement solidified body is buried, the heavy metals such as lead and cadmium are still dissolved in the acidic environment, and the cement solidified body is easily disintegrated under the acidic environment for a long time. The heavy metals in it are more soluble. In order to effectively reduce the dissolution of heavy metals from the cement solidified material, a chelating agent or a high-temperature heat treatment method is generally used to reduce the dissolution of heavy metals. Although the use of a chelating agent can effectively reduce the dissolution of heavy metals, the strength of the obtained cured body cannot meet the requirements of the regulations; in addition, since the chelating agent is mostly a high unit price of the patented product, the processing cost is higher than the cost of curing only the cement. More than double, and some of the chelating agents have an odor, and may cause cracking or spoilage decomposition when in contact with air, which not only reduces the mechanical strength of the treated incineration fly ash solidified body, but also has long-term stability to heavy metals. influential. While the high-temperature heat treatment method can enclose the heavy metal in the sintered structure or the glass slag, the metal dissolution can be effectively avoided, but the sintering or melting process requires a large amount of energy cost, and the heavy metal is easy to volatilize during the high-temperature treatment. Therefore, there must be air pollution treatment equipment to avoid secondary pollution. In addition, since a large amount of chlorine salt is contained in the general incineration fly ash, since the general solidified body cannot effectively immobilize the chloride ion, it is easy to dissolve the chloride ion again, causing a problem that the chlorine ion content in the discharged water is too high. Therefore, how to develop a new curing agent that can effectively fix heavy metals in incineration fly ash and reduce the energy consumption of incineration fly ash processing is the direction that relevant industry players are actively studying.

Inorganic polymers are in recent years in order to improve the aforementioned disadvantages. Newly developed inorganic non-metallic material curing agent. It is obtained by stirring and immobilizing a reaction substrate rich in cerium and aluminum elements with an alkaline solution. However, the general inorganic polymer is a meta-kaolin (Metakaolin) obtained by firing kaolin at about 700 ° C (breaking the -OH bond) as a main active material, for example, the patent of the Republic of China Patent No. 97140773, One kind A method for treating heavy metals in an incineration fly ash by bottom slag wet sieving sludge, which is prepared by using incineration fly ash and bottom slag wet sieving sludge with a fixed proportion of metakaolin as a reaction substrate for inorganic polymeric materials. And adding an alkaline activation liquid to form a solidified body. However, the method requires not only the raw material to be subjected to wet sieve separation, sand washing separation, and sedimentation separation process, and the kaolin must be subjected to high temperature calcination, so the process time is long and high temperature curing is required. However, the hazardous waste in the treatment method accounts for only 33-46% by weight of the solidified body, and the proportion is also low. In addition, since the currently commercially available metakaolin is mostly obtained by calcination at 1000 ° C, its surface area and activity are not good, and the metakaolin which is calcined at 600 to 800 is not easily purchased, and therefore, in the era of energy shortage, utilization The technique of changing kaolin as an inorganic polymer reaction substrate will undoubtedly increase its cost and difficulty.

Accordingly, an object of the present invention is to provide a method for immobilizing heavy metals and chloride salts in hazardous waste incineration fly ash, comprising: adding a hazardous waste incineration fly ash containing chlorine salts, calcium ions and heavy metals The alkaline activation liquid obtains a mixed slurry, and the mixed slurry is stirred and then fixed at room temperature to obtain an incineration fly ash solidified product, wherein the alkaline activation liquid comprises an alkali metal aluminate, and at least one an alkali metal hydroxide, an alkali metal silicate, or a silicate glue, SiO the alkali activation solution is ₂ / M ₂ O is between 0.96 to 2.0, the content of the alkali metal aluminate for the hazardous waste incineration fly The ash weight is 5 to 10% by weight, and the incineration fly ash solidified material has a chloride ion solidification rate of more than 70%.

Preferably, the foregoing fixed hazardous waste incinerated fly ash A method for heavy metals and chloride salts, wherein the chloride ions in the mixed mud form a Freund's salt with calcium and aluminum ions, and the heavy metals of the incinerated fly ash are fixed to the layered double of the Freund's salt by ion exchange. In the metal structure.

Preferably, the foregoing fixed hazardous waste incinerated fly ash The method of heavy metal and chlorine salt, wherein the heavy metal in the incinerated fly ash of the hazardous waste comprises lead, cadmium, chromium, copper, etc., and the content of the chlorine salt is more than 20%.

Preferably, the foregoing fixed hazardous waste incinerated fly ash A method of heavy metals and chloride salts, wherein the weight ratio of the alkaline solution (liquid) to the hazardous waste incineration fly ash (solid) is between 0.6 and 1.4 (liquid/solid).

Preferably, the foregoing fixed hazardous waste incinerated fly ash The method of heavy metal and chlorine salt further comprises adding water quenched blast furnace stone powder in the mixed mud, and the content of the water quenched blast furnace stone powder is not more than 30% of the weight of the hazardous waste incineration fly ash.

The effect of the invention is to use externally added alkali metal containing aluminum Aluminate is used as an aluminum source. Instead of using metakaolin as a reactive component, it can effectively reduce the amount of heavy metal dissolved, and can effectively reduce the elution of chloride ions and greatly increase the compressive strength of incineration fly ash solidified materials.

The treatment method of the present invention is an incineration fly ash which treats general hazardous waste by an immobilization method, since the incineration fly ash has heavy metals and chlorine The incineration fly ash solidified body obtained by the immobilization treatment method of the present invention can effectively reduce the amount of heavy metal and chloride ion elution without affecting the mechanical strength of the solidified body, so that the salt content is high and cannot be directly buried. Direct landfill treatment does not require worrying about the dissolution of heavy metals or chloride ions after burial.

A preferred embodiment of the method for immobilizing hazardous materials in incinerated fly ash in a fly ash comprises: adding an alkaline activating solution to a hazardous waste incineration fly ash containing calcium ions, heavy metals and chloride salts After mixing the slurry, the mixed slurry is stirred and fixed at room temperature for at least 5 days to obtain an incineration fly ash solidified product. The cured product of the incineration fly ash obtained after the immobilization has a heavy metal dissolution rate after the M-TCLP test, and the compressive strength is greater than 160 kgf/cm ² , and the effective solidification rate of the chloride ion is greater than 70%.

Specifically, the aforementioned hazardous waste incineration fly ash is generally Residues after incineration of household or industrial waste, containing calcium ions, and heavy metals such as lead, cadmium, chromium, copper, etc., and the chloride salt content is greater than 20%. The alkaline activation liquid is obtained by mixing an alkali activator with water, and the alkali activator comprises an alkali metal aluminate, and at least one alkali metal hydroxide, alkali metal silicate, or citric acid gel, preferably The alkali metal aluminate is selected from the group consisting of sodium aluminate or potassium aluminate, and the alkali metal hydroxide and alkali metal silicate are selected from the group consisting of sodium citrate, potassium citrate, and sodium hydroxide and potassium hydroxide. And the alkali metal aluminate content is 5-10% by weight of the hazardous waste incineration fly ash.

At room temperature, only alkali has a direct destructive effect on the network structure of the citrate material; the stronger the base and the higher the temperature, the more likely the chain cleavage of the citrate network structure is caused. In general, the activity of the crystalline substance is low, and the amorphous substance is highly active due to the incomplete structure. Therefore, in order to effectively chemically activate the crystalline or amorphous citrate, it must be destroyed by a highly alkaline solution. The Si-O-Si and/or Si-O-Al network structure depolymerizes and disintegrates the network-like aggregates on the surface of the particles to form an active substance such as a helium tetrahedron or an aluminoxy tetrahedron monomer or oligomer. The chemical activity is increased, and the SiO ₄ and AlO ₄ tetrahedrons are again subjected to dehydration, condensation, hardening, etc., and re-polymerized to form a cementing material. Therefore, preferably, the alkaline activation liquid The molar ratio of cerium oxide to alkali metal oxide (SiO2/M2O, M is an alkali metal element) is between 0.96 and 2.0.

It should be noted that the fixed hazardous waste incineration fly of the present invention The method of adding heavy water and chlorinated salt in the ash can further add water-quenched blast furnace powder in the mixed slurry, and utilize the activity of the blast furnace powder and the large amount of strontium and calcium ions provided, thereby forming the polymeric cementing material and forming the Dissolved Freund's salt.

It is customary to add metakaolin as a reactive agent. The fixed incineration fly ash mainly utilizes the calcined kaolin because the -OH bond has been interrupted, so that interlayer voids are generated to increase the activity, so the kaolin and alkaline liquid will be changed. After blending with incineration fly ash, only incineration fly ash can be cemented and fixed in metakaolin, so it is not effective to reduce the re-dissolution of chloride ions and heavy metals. In the present invention, the alkali metal aluminate is added to the alkali activation solution, and the surface of the incineration fly ash is broken by a strong alkali solution to produce a lead colloid, and the alkali metal aluminate is provided with a sufficient aluminum source. Allows aluminum ions to react with chloride and calcium ions of incineration fly ash to form insoluble Freund's salt (Friedel's Salt, Ca ₂ Al(OH) ₆ Cl.2H ₂ O), so it can be effectively fixed The chlorine ions in the fly ash are incinerated, and when the Freund's salt is formed, the heavy metal ions in the incinerated fly ash are ion-exchanged with the cations in the Freund's salt structure, and the heavy metal can be further fixed to the formed Freund's salt structure. It can effectively prevent the re-dissolution of heavy metals and chloride ions after the incineration fly ash solidified material is buried.

In addition, the present invention is not required to be used after high temperature baking. The obtained high-environment territory is used as a raw material, so that the cost of the treatment can be reduced, and since the added aluminum source is a metal aluminate, unlike the general addition of metakaolin, since the amount of aluminum in the metakaolin is not easily controlled. The problem is that the present invention can also effectively control the content of aluminum ions.

Preferably, in order to allow the chloride ions in the incineration fly ash to be combined with aluminum The ion and the calcium ion form a Freund's salt, and the ratio of the molar number of the aluminum ion to the molar ratio of the chloride ion in the mixed mud is not less than 1, and the ratio of the molar number of the calcium ion to the molar ratio of the chloride ion is not less than 2, more preferably, The ratio of the molar number of calcium ions to the molar number of aluminum ions in the mixed solution is between 1 and 4; preferably, the ratio between the molar numbers of the calcium ions, aluminum ions and chloride ions is not less than The calcium aluminum chloride compound has a ratio of calcium, aluminum, and chloromol of 1.5 times.

However, when the amount of SiO ₄ or AlO ₄ monomer dissolved in the surface of the highly alkaline solution from the bismuth citrate (incinated fly ash) is too small, the cemented material may be insufficient in strength due to structural incompleteness, and therefore, the present invention is Controlling the alkalinity of the alkali-activated solution with an alkali metal hydroxide, an alkali metal silicate, and/or a phthalic acid gel, and further adjusting the aluminum content of the alkali-activated liquid by the alkali metal aluminate, and supplementing according to the actual situation The required AlO ₄ monomer can not only make up for the shortcomings of insufficient AlO ₄ monomer dissolved in the surface of the self-incineration fly ash of the high alkaline solution, so when the incineration fly ash does not contain aluminum, it can also be used normally.

The following two specific examples and two comparative examples are used to illustrate the method for fixing heavy metals and chloride salts in the incineration fly ash of hazardous waste according to the present invention.

The incineration fly ash (IFA) used in the following specific examples and comparative examples is from an incineration plant in northern Taiwan, and its source is fly ash from municipal waste incineration. After average sampling, the analysis was performed by X-ray fluorescence spectrometer (XRF). The analysis results are shown in the table below. The main components of fly ash are mainly CaO, SiO2, Al2O3 and Fe2O3, of which CaO accounts for 64.5%, SiO2 accounts for 8.1%, Al2O3 accounts for 4.2%, and Fe2O3 accounts for 4.6%.

Incineration fly ash XRF analysis

Specific example 1

First, 42 g of sodium hydroxide, 150 g of sodium citrate and 14 g of sodium aluminate were added to water (110 g), and the mixture was uniformly mixed to obtain a molar ratio of SiO ₂ /Na ₂ O of 0.96, SiO ₂ /Al ₂ O ₃ . The ear ratio was 20, and the sodium aluminate content was 5% by weight of the alkaline activated liquid of the weight of the incineration fly ash. Then, 285 g of the incineration fly ash was stirred and mixed with 316 g of the alkaline activation liquid to obtain a mixed slurry.

Finally, the mixed slurry is immobilized at room temperature of about 30 ° C to obtain an incineration fly ash solidified product.

Specific example 2

First, 27 g of sodium hydroxide, 150 g of sodium citrate and 14 g of sodium aluminate were added to water (110 g), stirred and mixed to obtain a molar ratio of SiO ₂ /Na ₂ O of 1.28, SiO ₂ /Al ₂ O ₃ . The ear ratio was 20, and the sodium aluminate content was 5% by weight of the alkaline activated liquid of the weight of the incineration fly ash, and 271 g of the incineration fly ash was stirred and mixed with 301 g of the alkaline activation liquid to obtain a mixed slurry.

Finally, the mixed slurry is immobilized at room temperature of about 30 ° C to obtain an incineration fly ash solidified product.

Comparative example 1

First, 42g of sodium hydroxide and 150g of water was added with silicon (110g) was stirred in a mixed uniformly to obtain ₂ / Na ₂ O mole ratios as a basic of SiO activation solution is 0.96, then the incineration ash and 302g 272g The alkaline activation solution is stirred and mixed to obtain a mixed slurry.

Finally, the mixed slurry is immobilized at room temperature of about 30 ° C to obtain an incineration fly ash solidified product.

Comparative example 2

First, 27 g of sodium hydroxide and 150 g of sodium citrate were added to water (110 g), and the mixture was uniformly stirred to obtain an alkaline activation solution of SiO ₂ /Na ₂ O with a molar ratio of 1.28, and then 259 g of incinerated fly ash and 287 g of The alkaline activation solution was stirred and mixed to obtain a mixed slurry.

Finally, the mixed slurry is immobilized at room temperature of about 30 ° C to obtain an incineration fly ash solidified product.

Comparative example 3

First, 12g of sodium hydroxide and 150g of sodium citrate were added to water (110g) and stirred and mixed to obtain an alkaline activation solution with a molar ratio of 1.91 of SiO ₂ /Na ₂ O, and 245g of incineration fly ash and 272g. The alkaline activation solution was stirred and mixed to obtain a mixed slurry.

Finally, the mixed slurry is immobilized at room temperature of about 30 ° C to obtain an incineration fly ash solidified product.

Next, the cured incineration fly ash obtained by the above is immobilized 7 The compressive strength, chloride ion elution concentration, and heavy metal dissolution measurement were measured after days, 14 days, and 28 days, respectively.

Chloride ion dissolution measurement, refer to CNS13407-fine particle Water-soluble chloride ion content test method. For the sake of precision, this study firstly weighed 1000g of dried samples of incineration fly ash solidified material after 28 days of immobilization in a beaker, then added 500g of deionized water and sealed it with a sealing film, then placed it in super The sonic oscillator was placed for 1 hr and allowed to stand for 48 hr. Then, the beaker was shaken up and down every 5 minutes for a total of 3 times to extract the salt contained. After standing, it was filtered, and 50 mL of the filtrate was taken up in a conical flask, and 1 mL of potassium chromate indicator was added. After the titration with a silver nitrate solution to the reddish brown end point, the titration result is calculated by the following formula, and the chloride ion content in the solution can be determined.

Water-soluble chloride ion content (%) = ( f × 0.0035 × ( A - B )) / W × 100

A = volume of silver nitrate consumed (mL); B = volume of blank test silver nitrate consumption (mL); W = sample weight (g)

Heavy metal dissolution measurement system refers to the standard of the environmental inspection institute (NIEA R201.14C , toxic characteristic dissolution test), which is the heavy metal toxic concentration of the effluent produced after the simulated waste is eroded by acid rain. The experimental method is to first weigh the solid in the container, add the extract, adjust the liquid-solid ratio (L/S) to 20, and place it in the rotating device, set the rotation speed of 30 rpm and the rotation time to 18 ± 2 hr. The liquid was filtered and its heavy metal concentration was determined by inductively coupled plasma atomic emission spectrometry (ICP-AES).

The above measurement results are separately compiled in Tables 1 to 3.

It can be seen from the results of the above Tables 1 to 3 that the solid of the present invention is utilized. The incineration fly ash solidified body obtained by the chemical conversion method can not only effectively fix the heavy metal but also reduce the elution of the chloride ions, and the compressive strength of the incineration fly ash solidified material obtained in the specific example 2 after 28 days of oxygen protection Up to 16 MPa, much higher than the compressive strength of the cured product containing no sodium aluminate in the alkaline active liquid component degree.

In summary, the present invention utilizes the mixing of incineration fly ash with an alkaline activation solution, and utilizes the aluminum content in the alkaline activation solution to control the mixed slurry to form a Freund's salt by forming a Freund's salt. The process of incinerating the chloride ions in the fly ash, and then fixing the heavy metals in the formed Freund's salt structure, thereby not only effectively fixing the heavy metals but also preventing the elution of the chlorine ions, and the obtained incineration fly ash solidified material The compressive strength can reach 160 kgf/cm ² or more, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the present invention is not limited thereto, that is, the simple equivalent changes and modifications made by the patent application scope and patent specification content of the present invention, All remain within the scope of the invention patent.

Claims (5)

A method for fixing heavy metals and chloride ions in a fly ash by hazardous waste, comprising adding an alkaline activation liquid to a hazardous waste incineration fly ash containing chlorine salt, calcium ion and heavy metal to obtain a mixed mud, and mixing the mixture After the slurry is stirred and fixed at room temperature, an incineration fly ash solidified product is obtained, wherein the alkaline activation liquid comprises an alkali metal aluminate, and at least one alkali metal hydroxide, alkali metal silicate, Or citrate gum, the alkali metal aluminate content is 5~10wt% of the weight of the hazardous waste incineration fly ash, and the alkaline activation liquid has a SiO ₂ /M ₂ O ratio of 0.96-2.0, in the mixed mud The chloride ion forms a fluorine salt with calcium ions and aluminum ions, and the heavy metal of the hazardous waste incineration fly ash is fixed in the fluorine salt structure by ion exchange, and the solidification rate of the incineration fly ash solidified material is greater than that of the chloride ion 70%. A method for incinerating heavy metals and chloride salts in fly ash from hazardous waste according to claim 1, wherein the incineration fly ash solidified material has a compressive strength of up to 160 kgf/cm ² . The method for injecting heavy metals and chloride salts in fly ash from hazardous wastes according to claim 1, wherein the heavy metals in the incineration fly ash of the hazardous wastes include lead, cadmium, chromium, copper and the like. The method for injecting heavy metals and chloride salts in fly ash from hazardous waste according to claim 1, wherein the weight ratio of the hazardous waste incineration fly ash to the alkaline solution is between 0.6 and 1.4. The method for incinerating heavy metals and chloride salts in fly ash from hazardous wastes according to claim 1, further comprising adding water quenched blast furnace stone powder to the mixed mud The content of the water quenched blast furnace stone powder is not more than 30% of the weight of the hazardous waste incineration fly ash.