JPH01231981A - Treatment of waste - Google Patents

Abstract

PURPOSE:To maintain the density of a caked body of waste contg. salt and heavy metals by previously removing the salt by dissolution in water when the waste is caked with cement, etc. CONSTITUTION:Collected dust is mixed with an aq. soln. of calcium polysulfide in a mixing vessel 1 and this mixture is stirred in a reaction vessel 2. Salt in the dust dissolves in water in the aq. soln. and heavy metals react with S to form a precipitate of insoluble metal sulfides. The metal sulfides are separated from the resulting aq. soln. in a precipitate separating vessel 3, kneaded with cement in a kneading vessel 4, caked and discarded. Thus, the outflow of the heavy metals can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waste treatment method in which waste containing salt and heavy metals is mixed with an additive for insolubilizing the heavy metals and solidified with cement.

[Conventional technology]

Conventional treatment methods involve mixing additives and cement into waste at the same time and solidifying it.

[Problem to be solved by the invention]

However, if the solidified material is immersed in water or exposed to water such as rainwater for a long period of time, the salt in the solidified material will leach out, making the solidified material porous and brittle, and the heavy metals that have become insolubilized within the solidified material may become porous and brittle. There was a risk that it would easily leak out and cause a re-reaction and become harmful.

An object of the present invention is to make it difficult for heavy metals insolubilized from a solidified product to come out.

[Means to solve the problem]

The characteristic means of the waste treatment method of the present invention is that salts in the waste are removed by dissolving them in water before solidifying the waste with cement, and its functions and effects are as follows.

[For production]

In other words, even if a solidified cement product is exposed to water by dissolving and removing the salt in the waste, the density of the solidified product is maintained because there are no water-soluble substances in it. , heavy metals insolubilized by additives are
It is firmly held in the solidified material and does not come out.

〔Effect of the invention〕

Therefore, it is possible to prevent the insolubilized heavy metals from reacting again, making it possible to maintain the waste in a harmless state for a long period of time, and making it possible to save waste by disposing of it in a landfill or mountain area as a safe solidified product. Became.

〔Example〕

Next, embodiments of the present invention will be described based on the drawings.

The following treatment method will be used to render the dust collected during incineration of sewage sludge and municipal garbage harmless so that it can be disposed of.

In other words, the collected dust contains sodium chloride (Na
water-soluble salts such as CR), cadmium (Cd), arsenic (A
s), zinc (Zn), lead (Pd), chromium (Cr), etc., the collected dust is mixed with an aqueous solution of calcium polysulfide (CaSx) in a mixing tank (1), and then While being stirred in the reaction tank (2), the salt in the collected dust is dissolved into the water in the aqueous solution, and heavy metals (Cd, A
s, Zn, Pb, Cr) react with sulfur (S) in the calcium polysulfide aqueous solution to form insoluble gold sulfide M (CdS+
This results in a precipitate of AsS+ ZnS, PbS+ Cry).

Then, from the reaction treated water, the sedimentation separation tank (3)
The aqueous solution containing dissolved salt and the metal sulfide are separated, and the metal sulfide is kneaded together with cement in a kneading tank (4), solidified, and disposed of.

On the other hand, the reaction state in the reaction tank (2) is such that the salt is ionized as it elutes and the conductivity increases.
) and the amount of calcium polysulfide aqueous solution added to the mixing tank (1).

[Another example]

Instead of the collected dust, other waste may be used.

Instead of the calcium polysulfide (CaSx), sodium sulfide (NazS) or sodium polysulfide (NazS
may be a water-soluble sulfide such as ammonium polysulfide (NH4SX) or another substance that insolubilizes heavy metals;
These are collectively called additives.

The salt contained in the waste includes calcium chloride (
Salts such as CaCβ2), potassium chloride (KCl'), and sodium sulfate (NazSO,) may also be used.

An ion meter may be used instead of the conductivity meter (5).

In addition, sodium chloride (NaCit) in collected dust
The hydrogen chloride (HC1) contained in the exhaust gas from the incineration of sewage sludge, municipal waste, etc. is converted into sodium hydroxide (NaOl).
l) Sodium chloride (NaCI!) by sparging with an aqueous solution.
) and collected in a dust collector.

Although additives may be added to the waste after water is mixed therein, it is more efficient to insolubilize heavy metals if the additives are mixed in at the same time as water.

Incidentally, although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure shown in the accompanying drawings.

[Brief explanation of the drawing]

The drawing is a schematic diagram showing the waste treatment method of the present invention.

Claims (1)

[Claims] 1. A waste treatment method in which waste containing salt and heavy metals is mixed with an additive for insolubilizing the heavy metals and solidified with cement, the method comprising: before solidifying the waste with cement; Second, there is a waste treatment method that removes the salt in the waste by dissolving it in water. 2. The waste treatment method according to claim 1, wherein the water-soluble sulfide as the additive is added at the same time as the salt removal by the water is carried out when the waste is mixed.