JPH10128287A - Treatment of solid waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely fix a harmful material together with a heavy metal and to prevent a generation of a toxic gas by adding an inorg. ion exchanger to a solid waste and fixing the harmful material in the solid waste with the inorg. ion exchanger. SOLUTION: A 10% water dispersion of the inorg. ion exchanger is added and mixed to 100g soot and dust being the solid waste obtained from a trash incineration plant so that an amount as the inorg. ion exchanger may be 10g. In this state, the harmful material in the solid waste is fixed with the inorg. ion exchanger. In this way, not only heavy metal element such as mercury, cadmium, lead, zinc, copper and chromium but also the element of arsenic acid and selenic acid are fixed efficiently, moreover, a fear of a generation of the toxic gas is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the immobilization of harmful substances such as heavy metals present in solid wastes such as incinerated ash, dust, slag, sludge, soil and the like, and elution from these solid wastes. And a method for treating solid waste.

[0002]

2. Description of the Related Art Various elements are contained in solid waste such as incinerated ash and dust generated in garbage incineration plants, slag discharged from mines, sludge generated in wastewater treatment, and contaminated soil. It also contains a lot of heavy metal elements harmful to the human body, such as mercury, cadmium, lead, zinc, copper, and chromium. When metals contained in these solid wastes flow out, there is a possibility that groundwater, rivers, seawater, etc. will be contaminated.

For this reason, conventionally, a method has been adopted in which solid waste is solidified with cement, and then landfilled or dumped into the ocean. However, there is a risk that metal may flow out through the cement wall. It was not a safe treatment. In order to solve such problems, the applicant has
Various methods have been proposed for immobilizing metals in solid waste with a metal collecting agent (see, for example, JP-A-64-90).
083, JP-A-1-99679, JP-A-4-267
982).

[0004]

The above-mentioned method is a method by which harmful metal elements such as mercury, cadmium, lead, zinc, copper and chromium in solid waste can be fixed efficiently and reliably. However, harmful substances such as arsenic acid and selenic acid are also contained in the solid waste, and it is difficult to immobilize these substances by a conventional treatment method using only a metal collecting agent. . For this reason, ferric chloride,
Using additives such as aluminum sulfate and polyiron sulfate together,
Methods for immobilizing arsenic acid and selenic acid were studied. However, in order to reliably fix arsenic acid, selenic acid, and the like in solid waste, it is necessary to add an additive as much as 30% by weight of the weight of solid waste. Was also a problem. In addition, since many metal collectors used for solid waste treatment have a substituent containing sulfur such as dithioic acid group, acidic substances are contained in solid waste. In this case, there is a problem that toxic hydrogen sulfide gas is generated.

The present inventors have conducted intensive studies to solve the above problems, and as a result, by using an inorganic ion exchanger instead of a conventional metal collector, mercury, cadmium, lead, zinc, copper, chromium, etc. It has been found that not only heavy metal elements but also elements such as arsenic acid and selenic acid can be efficiently immobilized and that there is no risk of generating toxic gas, and the present invention has been completed.

[0006]

That is, in the method for treating solid waste according to the present invention, an inorganic ion exchanger is added to solid waste, and harmful substances in the solid waste are fixed by the inorganic ion exchanger. It is characterized in that Dust is particularly suitable as the solid waste targeted by the present invention.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The inorganic ion exchanger used in the present invention includes, for example, metal oxides and hydrated oxides, polyvalent metal acid salts, insoluble heteropolyacid salts, insoluble ferrocyanides, aluminosilicates and clay minerals. Is mentioned.

The metal oxides and hydrated oxides include oxides and hydrated oxides of titanium, zirconium, aluminum, antimony, rare earth elements and the like. Polyvalent metal acid salts include titanium, zirconium, aluminum,
Rare earth elements, phosphates such as chromium (III), etc., as insoluble heteropolyacid salts, phosphorus antimonic acid, molybdophosphoric acid, molybdic acid, antimonic acid, titanic acid, niobic acid, vanadic acid, aluminate, etc. Sodium, potassium, calcium, magnesium, zirconium, titanium, aluminum, tin salts and the like.

[0009] Insoluble ferrocyanides include:
Cobalt ferrocyanide and the like, aluminosilicates and clay minerals, zeolite, mordenite,
Bentonite, vermiculite, smectite (including montmorillonite) and the like. Further, in addition to these, hydroxyapatite, tobermorite, zonotolite, magadylite, and the like, calcium carbonate, calcium silicate, sodium silicate, magnesium silicate, zirconium silicate, and the like can also be used as the inorganic ion exchanger. These inorganic ion exchangers can be used alone or in combination of two or more. These inorganic ion exchangers, depending on their chemical structure, crystal structure, interlayer distance, etc.
Since the selectivity to cations or anions and the ion exchange properties are different, it is necessary to select an inorganic ion exchanger based on the type and amount of ions eluted from the solid waste to be treated.

[0010] The solid wastes targeted by the method of the present invention include:
Although it is incinerated ash, dust, slag, sludge, soil, etc., it is particularly suitable for treating dust in the form of fine powder. To treat these solid wastes, it is only necessary to add and mix the inorganic ion exchanger with the solid waste. However, the inorganic ion exchanger is not suitable for the reaction of immobilizing metals and the like in the solid waste. , Because water is required, when processing fly ash, dust, slag, etc.,
The inorganic ion exchanger is dispersed in water and added to and mixed with solid waste, or the inorganic ion exchanger and water are added to and mixed with solid waste. In addition, since sludge and soil generally contain moisture, it is effective to simply add and mix an inorganic ion exchanger, but if necessary, disperse the inorganic ion exchanger in water and add it. Preferably, water is separately added. For example, metal oxides and hydrated oxides have excellent ability to fix anions of elements such as arsenic and selenium, and polyvalent metal acid salts have excellent ability to fix cations. Is preferably used by mixing a metal oxide or a hydrated oxide with a polyvalent metal acid salt.

The amount of the inorganic ion exchanger to be added to the solid waste varies depending on the amount of the metal to be immobilized contained in the solid waste. The amount is about 0.1 to 50% by weight of the weight of the solid waste.

[0012] Some of the inorganic ion exchangers used in the present invention have a higher immobilizing ability than conventional metal collectors, especially for arsenic acid and selenic acid. However, depending on the type and content ratio of heavy metals contained in the solid waste, it is more effective to use a normal metal collecting agent together with the inorganic ion exchanger, and the amount of the inorganic ion exchanger used is reduced. Sometimes you can. However, when a metal collecting agent is used in combination, it is necessary not to impair the performance of the inorganic ion exchanger. However, when the inorganic ion exchanger and the metal collecting agent are added simultaneously, the inorganic ion exchanger becomes Since there is a possibility that the collecting agent may coat or impair the ion exchange ability, it is preferable to add them separately.

The solid waste treated by the method of the present invention can be finally disposed as it is, or by solidifying it with cement or the like and burying it.

[0014]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. Examples 1 to 4 For 100 g of dust obtained from a garbage incineration plant, a 10% aqueous dispersion of an inorganic ion exchanger shown in Table 1 was added so that the amount of the inorganic ion exchanger added was 10 g. 3
Kneaded for 0 minutes. Next, a dissolution test of metals and the like from the treated product was performed. 80 g of the treated product was shaken at room temperature for 60 minutes in 1000 ml of water at pH = 8, and the concentration of metals and the like eluted from the treated product into water was measured by atomic absorption spectrometry. The results are shown in Table 1.

[0015]

[Table 1]

Comparative Example 1 A test was conducted in the same manner as in Examples 1 to 4, except that a 40% aqueous solution of sodium dimethyldithiocarbamate was used as a metal collector instead of the inorganic ion exchanger. The results are shown in Table 1.

Examples 5 to 10 7 g of an inorganic ion exchanger shown in Table 2 was added per 100 g of sludge (water content 70%) and kneaded for 30 minutes. Next, the dissolution test of the treated product was performed in the same manner as in Examples 1 to 4. The results are shown in Table 2.

[0018]

[Table 2]

Comparative Example 2 A test was conducted in the same manner as in Examples 5 to 10 except that triazine thiol was used as a metal collector instead of the inorganic ion exchanger. The results are shown in Table 2.

[0020]

As described above, the method of the present invention employs a method in which an inorganic ion exchanger is added to solid waste to fix harmful substances in the solid waste. Even when harmful substances such as arsenic acid and selenic acid, which are difficult to immobilize by the method using a metal trapping agent, are contained in solid waste, these harmful substances can also be immobilized reliably with heavy metals. Has an effect.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C02F 11/14 B09B 3/00 304K C09K 3/00 107

Claims (2)

[Claims] 1. A method for treating solid waste, wherein an inorganic ion exchanger is added to the solid waste, and harmful substances in the solid waste are immobilized by the inorganic ion exchanger. 2. The method for treating solid waste according to claim 1, wherein the solid waste is dust.