JP2013087274A - Heavy metal-fixing agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a polysulfide aqueous solution made from quicklime or slaked lime and sulfur and used as a heavy metal-fixing agent in the fields of wastewater treatment and soil treatment, the reactivity of the solution with heavy metal ions is low, the fixing of heavy metals is insufficient, and the odor of the hydrogen sulfide is generated.SOLUTION: A mixture having calcium hydroxide and sulfur as principal ingredients is obtained by blowing ozone gas into a polysulfide aqueous solution or adding an alkali agent thereto to change the structure of polysulfide. The use of this mixed aqueous solution as the fixing agent increases the reactivity with heavy metal ions and suppresses the generation of odor.

Description

The present invention relates to a heavy metal fixing agent that is used in wastewater treatment, soil treatment, incineration ash treatment, and the like, and in the case where harmful heavy metals are contained in wastewater, soil, or incineration ash, the heavy metal is fixed and detoxified.

There are a plurality of treatment agents mainly composed of polysulfides as treatment agents for immobilizing heavy metals in waste water, soil, and incineration ash. It is known that such a treatment material containing polysulfide as a main component sulfidizes harmful heavy metals such as lead, cadmium, mercury, chromium and arsenic, and converts it into a stable and harmless sulfide.

JP-A-59-59281 Japanese Laid-Open Patent Publication No. 2005-213375

Usually, when polysulfide is produced, alkaline material such as quick lime, slaked lime or incinerated ash and sulfur are mixed with water, and heated and pressurized. At this time, the alkali material and sulfur are combined to form a polysulfide. However, in this production method, a stable aqueous solution is obtained by containing the alkali material and sulfur until they are saturated, and when this is used as a treating agent, the reaction with heavy metal ions does not cause sufficient reaction, or Even if it reacts, hydrogen sulfide is generated, and it becomes a work in a very poor environment.

For example, a compound produced from quicklime or slaked lime and sulfur is a polysulfide named Bazhenovite, and its crystal structure is said to be CaS5 · CaS2O3 · 6Ca (OH) 2 · 20 (H2O). It has been found that it is effective to change the form of this compound to form a mixture mainly composed of calcium hydroxide and sulfur.
As a method of preparing a mixture mainly composed of calcium hydroxide and sulfur, a method of blowing ozone into a polysulfide aqueous solution and a method of adding an alkali agent to the polysulfide aqueous solution have been devised.

From the crystal structure of CaS5 ・ CaS2O3 ・ 6Ca (OH) 2 ・ 20 (H2O), by making a mixture mainly composed of calcium hydroxide and sulfur, the reactivity with heavy metals is improved and the generation of hydrogen sulfide is suppressed. I got the knowledge that I can do it.

An example in which ozone gas is blown into the polysulfide aqueous solution is shown. X-ray diffraction data of a polysulfide aqueous solution and a mixture of calcium hydroxide and sulfur as main components of the present invention. Upper: Heavy metal fixative of the present invention by addition of sodium hydroxide Discontinuation: Heavy metal fixative of the present invention by ozone treatment Lower: Commercial polysulfide aqueous solution Results of heavy metal immobilization tests of the present invention and comparative examples

About polysulfide aqueous solution made by mixing quick lime or slaked lime and sulfur in water, heating and pressurizing, mixing ozone hydroxide and sulfur as main components by blowing ozone gas into this aqueous solution and changing the crystal structure Generate a body. As another method, even when an alkaline agent such as sodium hydroxide is added to this aqueous solution, a mixture mainly composed of calcium hydroxide and sulfur can be produced. It has been found that when these are used as fixing agents for heavy metals, the formation of hydrogen sulfide can be promoted and the generation of hydrogen sulfide can be suppressed compared to polysulfide aqueous solutions.

Hereinafter, the present invention will be described in more detail with reference to specific examples.
First, a method using ozone gas will be described.
In order to produce a heavy metal fixing agent, ozone gas was blown into a commercially available aqueous polysulfide solution (lime sulfur mixture manufactured by Miyauchi Sulfur Mixture Co., Ltd.).
FIG. 1 shows an outline of blowing ozone.
One liter of polysulfide aqueous solution was put into a container, stirred, and ozone gas was blown into the container at a rate of 2 liters per minute through the pipe and held for 8 hours.
By blowing in ozone, the structure of the commercially available polysulfide aqueous solution was broken to obtain a mixture mainly composed of calcium hydroxide and sulfur.
Next, the addition of an alkaline agent will be described.
Similarly, 5% by weight of industrial flaky sodium hydroxide was added to 1 liter of a commercially available aqueous solution of polysulfide (lime sulfur mixture manufactured by Miyauchi Sulfur Mixture Co., Ltd.). When the mixture was stirred while sodium hydroxide was added, a solid was precipitated, which was separated by filtration to obtain an aqueous solution. The obtained aqueous solution is a mixture mainly composed of calcium hydroxide and sulfur.
It has been confirmed that this phenomenon is not only caused by sodium hydroxide but also by other alkaline agents such as calcium hydroxide, potassium hydroxide, and sodium carbonate.
Of course, even when a polysulfide aqueous solution is obtained by mixing and heating quick lime or slaked lime with sulfur and water in a pressure cooker instead of a commercially available polysulfide aqueous solution, ozone gas is blown in the same manner, or By adding an alkali agent, a mixture mainly composed of calcium hydroxide and sulfur can be obtained.

A commercially available polysulfide aqueous solution and the mixture of the present invention were dried at room temperature until the liquid disappeared, and X-ray diffraction was performed using the powder obtained by this drying. The result is shown in FIG.
According to FIG. 2, the crystal structure of the commercially available polysulfide aqueous solution is CaS5 · CaS2O3 · 6Ca (OH) 2 · 20 (H2O), but the mixture treated with ozone was also added with sodium hydroxide. The mixture also changes to calcium hydroxide and sulfur peaks.
Regarding these X-ray diffraction data, there is a possibility that the database will be accumulated in the future and the structure of the substance showing the peak may be changed. In the present invention, from the current database, a mixture containing calcium hydroxide and sulfur as main components is used. However, it is added that if the crystal structure is changed, the substance name must be changed.

FIG. 3 is a result of investigating the reactivity with heavy metals and the generation state of hydrogen sulfide with respect to the mixture of calcium hydroxide and sulfur by the ozone treatment according to the present invention and the commercially available polysulfide aqueous solution. .
Four types of nickel ion solution, arsenic ion solution, iron ion solution, and zinc ion solution were prepared for each concentration. In addition, pH of the aqueous solution at this time was 5-6. One liter of this solution was collected in a beaker, and one drop of each aqueous solution was added thereto. Each ion concentration before and after the addition of the aqueous solution was measured. In addition, the presence or absence of hydrogen sulfide odor, which is a hot spring odor, was evaluated during the addition.
As shown in FIG. 3, it can be seen that the heavy metal fixing agent of the present invention is effective for four types of heavy metal ions. Moreover, it turns out that the heavy metal fixing agent of this invention is advantageous also regarding an odor.

1 Ozone gas blowing pipe 2 Stirrer 3 Container 4 Polysulfide aqueous solution

Claims (3)

A heavy metal fixing agent mainly composed of calcium hydroxide and sulfur having diffraction angles (2θ) of diffraction peaks of maximum intensity in X-ray diffraction of 34.5 ° ± 2 ° and 23.5 ° ± 2 °. The method for producing a heavy metal fixing agent mainly comprising calcium hydroxide and sulfur according to claim 1 by blowing ozone gas into the polysulfide aqueous solution. The method of manufacturing the heavy metal fixing agent which has calcium hydroxide and sulfur as a main component of Claim 1 by adding an alkaline agent to polysulfide aqueous solution.

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