JP2007054818A - Method for treating water polluted with selenium and agent therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating water polluted with selenium and an agent therefor capable of easily decreasing the selenium concentration below the value prescribed by the environmental quality standard. <P>SOLUTION: The method for removing heavy metals by reducing and depositing them contained in the polluted water by making the polluted water contact iron particles employs the iron particles containing aluminum not less than 0.1 wt.%, calcium not less than 0.05 wt.%, and titanium not less than 0.05 wt.% and by making the water polluted with the selenium contact the iron particles to remove the selenium by reducing and depositing thereof. The method is preferably carried out with weakly acidic environment in a non-oxidizing atmosphere in a closed reactor. The agent for treating the water comprises the above iron particles. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention is excellent in the reduction and precipitation effect of selenium in a treatment method in which selenium contained in various polluted water such as factory effluent, sewage and river water is brought into contact with iron powder to reduce and precipitate and is removed. The present invention relates to a method for treating selenium-containing contaminated water that can easily reduce the selenium concentration of the selenium to an environmental standard value or less.

Selenium is an environmental pollutant, and a method for removing selenium in wastewater has been conventionally known. For example, in Japanese Patent Application Laid-Open No. 07-2502 (Patent Document 1), selenium is deposited on the surface of iron or iron-based metal by contacting a drainage liquid containing selenium and / or a selenium compound with iron or iron-based metal. A method for treating selenium and / or selenium compound-containing effluents that reduces the selenium concentration in the effluents is described.

Japanese Patent Application No. 09-47790 (Patent Document 2) discloses that exhaust gas desulfurized water is brought into contact with at least one metal selected from iron, manganese, nickel, and copper to thereby oxidize wastewater. A processing method is described which precipitates and removes the active substance and selenium.
Japanese Unexamined Patent Publication No. 07-2502 Japanese Patent Application No. 09-47790

In the treatment method of Patent Document 1, it is shown that an iron-chromium alloy having a chromium content of 12.5% or less is used as an iron-based metal, not just pure iron, but other alloy components are described. Absent. Further, in the treatment method of Patent Document 2, it is described that manganese, nickel, and copper are used in addition to iron, but other metals are not mentioned, and in any treatment method, The relationship between the type and content of other metal components contained in iron and the effect of removing selenium is not known. Furthermore, in the treatment method of Patent Document 2, manganese, nickel, and copper are solubilized when the acidity of the wastewater is strong, so that there is a problem of causing contamination by these metals.

The present invention focuses on components such as iron powder to be used in a treatment method for reducing and precipitating selenium contained in various wastewaters such as factory wastewater, sewage, river water, etc. Based on this finding, it has been found that the effect of removing selenium such as iron powder containing a small amount of iron is excellent, and the effect of treating selenium-containing water has been enhanced. Secondary metal contamination by manganese, nickel, copper, etc. A processing method that is excellent in the effect of removing selenium is provided.

The present invention relates to a method for treating selenium-containing contaminated water having the following configuration.
(1) In a treatment method in which contaminated water is brought into contact with iron fine particles to reduce and precipitate heavy metals contained in the contaminated water, 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and titanium A method for treating selenium-containing contaminated water, comprising using iron powder fine particles containing 0.05% by weight or more, bringing the iron powder fine particles into contact with contaminated water containing selenium, and reducing and precipitating selenium. .
(2) Iron powder fine particles containing 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05% by weight or more of titanium, in a non-oxidizing atmosphere and weakly acidic in a closed reaction tank, The method for treating selenium-containing contaminated water as described in (1) above, wherein contaminated water containing selenium is brought into contact.
(3) For selenium-containing contaminated water having a selenium concentration of 0.05 to 0.5 mg / L before treatment, the selenium concentration after treatment is reduced to the environmental standard value (0.01 mg / L) or less (1) or above The method for treating selenium-containing contaminated water as described in (2).
(4) A water treatment agent comprising iron powder fine particles containing 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05% by weight or more of titanium.
(5) 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05% by weight or more of titanium, 50% cumulative particle size of 30 to 80 μm, and mode particle size of 30 to 150 μm The water treatment agent according to (4), comprising iron powder fine particles.

According to the treatment method of the present invention, the effect of removing selenium contained in various polluted waters such as factory waste water, sewage, and river water can be enhanced. Specifically, for example, for selenium-containing contaminated water having a selenium concentration of 0.05 to 0.5 mg / L before treatment, the selenium concentration after treatment may be reduced to an environmental standard value (0.01 mg / L) or less. it can.

Since the treatment method of the present invention is a method of reducing selenium by bringing contaminated water containing selenium into contact with iron powder fine particles containing specific amounts of aluminum, calcium, and titanium, no special equipment is required. Moreover, since it can process at normal temperature, it can implement easily.

The treatment method of the present invention is a treatment method in which contaminated water is brought into contact with iron powder fine particles to reduce and precipitate heavy metals contained in the contaminated water, and is 0.1% by weight or more of aluminum and 0.05% by weight of calcium. The selenium-containing contamination is characterized by using iron powder fine particles containing 0.05% by weight or more of titanium and bringing the iron powder fine particles into contact with contaminated water containing selenium and reducing and precipitating selenium. Water treatment method.

In the treatment method of the present invention, contaminated water broadly means water containing heavy metals, and includes various types of wastewater and wastewater generated naturally and artificially. For example, industrial wastewater, sewage, seawater, river water This refers to water that contains heavy metals, such as water from swamps and lakes, surface water from the surface, water from dams such as rivers, underground running water and water, and culvert water. In some cases, the contaminated water is called drainage.

In the present invention, heavy metals refer to heavy metal elements such as selenium, cadmium, hexavalent chromium, lead, zinc, copper, nickel, arsenic, and antimony, and metal elements. Selenium-containing contaminated water refers to contaminated water containing selenium as a heavy metal.

Usually, selenium contained in waste water or the like is present in the form of selenite ion [SeO ₃ ^2- ] (tetravalent selenium) or selenate ion [SeO ₄ ^2- ] (hexavalent selenium). In addition to selenium, the contaminated water to be treated according to the present invention may contain other heavy metal ions as long as the reduction of selenium is not greatly hindered.

The iron powder fine particles used in the treatment method of the present invention are iron powder, iron fine particles, iron pieces, iron containing 0.1 wt% or more of aluminum, 0.05 wt% or more of calcium, and 0.05 wt% or more of titanium. Such as cutting waste. In addition, iron powder, iron fine particles, iron pieces, iron cutting waste, etc. are referred to as iron powder fine particles. Reducible ferrous ions are eluted from the iron powder fine particles in contact with the contaminated water, and this reduces and precipitates selenium ions and other heavy metal ions. Aluminum, calcium and titanium contained in the iron powder are considered to have an action of promoting reduction of selenium.

As shown in the examples and comparative examples described later, when iron powder fine particles containing the metal component are used, a selenium reduction rate of 97% or more can be obtained. On the other hand, the selenium reduction rate in the case of using iron powder fine particles in which any one of aluminum, calcium, and titanium is less than the above content is at most about 57%, and the treatment effect is remarkably different. Note that even if the contents of aluminum, calcium and titanium are all greater than 1.0% by weight, the reduction rate of selenium is not so different, so the aluminum content is 0.1 to 1.0% by weight and calcium is contained. The amount and the titanium content may be 0.05 to 1.0% by weight, respectively.

Moreover, the iron powder fine particles may be any material as long as it contains aluminum, calcium, and titanium with the above contents, and are not limited to carbon steel, and various iron and iron pieces and pieces of iron containing metal components such as chromium and manganese, or Cutting waste or the like can be used. These iron powders and the like are preferably as fine as possible because they have a larger contact area with drainage and the like. Specifically, iron powder fine particles having a 50% cumulative particle size of 30 to 80 μm and a mode particle size of 30 to 150 μm are preferable.

The amount of iron powder fine particles used may be about 1 to 3 g / L with respect to 1 L of drainage or the like having a selenium concentration of 0.05 to 0.5 mg / L. In addition, it is preferable to use selenium such as waste water and iron powder fine particles in contact with each other under stirring in a non-oxidizing atmosphere and under weak acidity (for example, pH = 3 to 5) using a sealed reaction tank. The temperature of the drainage or the like may be room temperature (15 ° C. to 25 ° C.).

Selenium ions contained in the contaminated water are reduced upon contact with the iron powder fine particles, and are deposited on the iron powder surface. On the other hand, the surface of the iron powder particles dissolves little by little under weak acidity, so the selenium deposited on the iron powder surface is separated into the liquid under stirring and the iron powder surface becomes fresh, and the reduction of selenium ions proceeds repeatedly. .

The selenium deposited by reduction is starched or suspended in the liquid, and this is solid-liquid separated to remove the selenium from the waste water or the like. Centrifugation or thickener can be used as the solid-liquid separation means. Further, the drainage containing precipitated selenium and iron powder may be guided to a wet cyclone and separated.

According to the above treatment method, for example, the selenium concentration in the wastewater after treatment is reduced to the environmental standard value by reducing and removing selenium ions in the wastewater etc. in the selenium concentration of 0.05 to 0.5 mg / L before treatment. 0.01 mg / L) or less. Moreover, if the iron powder fine particle of this invention is used, the heavy metals reduced besides selenium can be deposited and removed. Therefore, the iron powder fine particles of the present invention can be used not only for the treatment of selenium but also for the treatment of other heavy metals.

Contaminated water (selenium concentration and chromium concentration 0.40 mg / L) containing selenium and chromium is placed in a treatment tank (capacity 5 L), and the trace metal components shown in Table 1 are contained in the contaminated water containing selenium and chromium. Iron powder 1.0-2.5g / L is added, and it is made to react for 90 minutes, rotating the inside of a tank at the rotation temperature of liquid temperature 15-25 degreeC, pH = 3.5-4.5, 300-500 rpm. Then, selenium was reduced and precipitated, and the precipitated selenium was separated into solid and liquid. The chromium adsorbed on the iron powder was separated into solid and liquid together with the iron powder. The processing results for each iron powder used are shown in Table 1. The iron powder used has a 50% cumulative particle size of 30 to 80 μm and a most frequent particle size of 30 to 150 μm.

As shown in Table 1, all of the contaminated water (samples No. 5 and No. 6) treated with the iron powder of the present invention had a selenium reduction rate of 97.5% or more, and the selenium concentration after the treatment Is reduced below the environmental standard value, and an excellent selenium reduction rate (selenium removal rate) can be obtained. Moreover, also about the chromium processed using the iron powder of this invention, the removal rate is 97.5% or more, and the removal rate is high.

On the other hand, the contaminated water (samples No. 1 to No. 4) treated with iron powder whose aluminum content, calcium content and titanium content are less than the range of the present invention has a residual selenium concentration of 0. 17mg / L or more (selenium removal rate of 57.5% or less), residual chromium concentration after treatment is 0.02mg / L or more, and both selenium and chromium residual concentrations are environmental standards (0.01mg / L) The result is higher.

Claims (5)

In a treatment method in which contaminated water is brought into contact with iron powder fine particles to reduce and precipitate heavy metals contained in the contaminated water, 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05 of titanium A method for treating selenium-containing contaminated water, comprising using iron powder fine particles containing at least wt%, bringing the iron powder fine particles into contact with contaminated water containing selenium, and reducing and precipitating selenium.
Iron powder fine particles containing 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05% by weight or more of titanium contain selenium in a non-oxidizing atmosphere of a closed reaction tank and under weak acidity. The method for treating selenium-containing contaminated water according to claim 1, wherein the contaminated water is contacted.
The selenium according to claim 1 or 2, wherein the selenium-containing contaminated water having a selenium concentration of 0.05 to 0.5 mg / L before treatment is reduced to an environmental standard value (0.01 mg / L) or less after treatment. Treatment method of contained contaminated water.
A water treatment agent comprising fine iron powder containing 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium, and 0.05% by weight or more of titanium.
Iron containing 0.1% by weight or more of aluminum, 0.05% by weight or more of calcium and 0.05% by weight or more of titanium, 50% cumulative particle size of 30 to 80 μm, and mode particle size of 30 to 150 μm The water treatment agent according to claim 4, comprising fine powder particles.