JP6662168B2 - Acidic water neutralizing agent and acidic water neutralizing treatment method - Google Patents

Description

  The present invention relates to an acidic water neutralizing agent and an acidic water neutralizing treatment method using the same.

  Mine wastewater often shows sulfuric acidity due to oxidation of sulfide ore and dissolution in groundwater. BACKGROUND ART Conventionally, mine wastewater has been discharged to rivers and the like by neutralizing limestone or slaked lime using a calcium-based alkali dissolved in water as a neutralizing agent. A large amount of iron is often dissolved in mine wastewater, and when the pH rises due to the neutralization reaction, precipitation of iron hydroxide occurs due to the effect of the solubility product. In addition, when a neutralization treatment is performed using limestone or slaked lime, sulfate ions and calcium components contained in a large amount in the mine wastewater react with each other to generate gypsum as a neutralized precipitate. Therefore, in the neutralization treatment of mine wastewater using calcium compounds such as limestone and slaked lime, a large amount of neutralized precipitates such as iron hydroxide and gypsum are generated, and enormous costs are required for the neutralized precipitate treatment (For example, see Patent Document 1).

  In order to solve this problem, a method has been proposed in which a magnesium compound such as magnesium hydroxide or magnesium oxide is used as a neutralizing agent to suppress the formation of a neutralized precipitate (for example, see Patent Document 2). When a magnesium compound is used as a neutralizing agent, the solubility of magnesium sulfate produced by reacting with sulfate ions is extremely high compared to gypsum and does not remain as a solid in treated water. Can be reduced.

JP-B-61-156 JP-A-2003-190969

  However, since magnesium hydroxide and magnesium oxide have low solubility in water, the rate of neutralization is slow, and there is room for improvement in that the amount used for neutralization increases.

  An object of the present invention is to provide an acidic water neutralizing agent containing a magnesium compound, which has an excellent neutralization rate and can neutralize acidic water with a sufficiently small amount of use.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, by adding an appropriate amount of an ammonium salt to a magnesium-based alkali such as magnesium hydroxide or magnesium oxide, the neutralization speed is increased, and the neutralization rate is increased. The inventors have found that the amount used can be suppressed, and have accomplished the present invention.

  That is, the acidic water neutralizing agent according to the present invention contains a magnesium compound and an ammonium salt. Magnesium compounds include magnesium hydroxide, magnesium oxide and mixtures thereof. Examples of the ammonium salt include diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, ammonium dihydrogen phosphate, ammonium hydrogen carbonate, and a mixture of two or more thereof.

  ADVANTAGE OF THE INVENTION According to the acidic water neutralizing agent which concerns on this invention, since the magnesium compound and the ammonium salt were used together, the excellent neutralization rate can be achieved and the acidic water can be neutralized with a sufficiently small amount of use. On the other hand, when a magnesium compound (for example, magnesium hydroxide) is used alone as an acidic water neutralizing agent, the water to be treated is neutralized to a predetermined pH (for example, pH 7) or more within a predetermined time (for example, 20 minutes). Therefore, it is necessary to add a large amount of neutralizing agent (magnesium compound) to the acidic water as compared with the present invention. In addition, even if it does not add a large amount of a magnesium compound, although pH of acidic water will reach predetermined pH if it takes time, neutralization processing cannot be completed within predetermined time.

  The reason why the neutralization rate is improved by using a magnesium compound and an ammonium salt in combination is not clear, but the present inventors speculate as follows. That is, it is presumed that ammonium ions act as Lewis acids in water, and that the solubility of the magnesium compound is improved.

When magnesium hydroxide is used as the magnesium compound, the magnesium hydroxide contained in the acidic water neutralizing agent has an average particle diameter of 1 to 10 μm from the viewpoint of achieving a higher neutralization rate, and a Blaine specific surface area of 1000 to 1000. Preferably, it is 30,000 cm ² / g. When using magnesium oxide as the magnesium compound, the magnesium oxide contained in the acidic water neutralizing agent has an average particle diameter of 1 to 10 μm and a Blaine specific surface area of 1,000 to 30,000 cm ² from the viewpoint of achieving a higher neutralization rate. / G.

  In the acidic water neutralizing agent according to the present invention, the ratio B / A of the mole number B of ammonium contained in the ammonium salt to the mole number A of magnesium contained in the magnesium compound is preferably more than 0 and 0.5 or less. . The neutralizing agent for acidic water according to the present invention can be obtained by mixing a magnesium compound and an ammonium salt such that the value of the molar ratio B / A falls within this range.

  The present invention provides a method for neutralizing acidic water, which comprises a step of adding the neutralizing agent for acidic water to acidic water to be neutralized. By using the neutralizing agent for acidic water according to the present invention, the acidic water can be neutralized with a sufficiently small amount of use. The acidic water to be neutralized is water having a pH of 5 or less, and includes mine wastewater, river water, groundwater, and a mixed water of two or more of these.

  According to the present invention, a neutralizing agent containing a magnesium compound, which has an excellent neutralization rate, can neutralize acidic water with a sufficiently small amount of use, and a method for neutralizing acidic water using the same Is provided.

  Hereinafter, embodiments of the present invention will be described in detail.

<Acid water neutralizer>
The acidic water neutralizing agent according to the present embodiment is for neutralizing acidic water, and includes a magnesium compound and an ammonium salt. According to this acidic water neutralizer, an excellent neutralization rate can be achieved by using a magnesium compound and an ammonium salt in combination, and the acidic water can be neutralized with a sufficiently small amount of use. The acidic water to be treated is, for example, water having a pH of 5 or less, and includes mine wastewater, river water, groundwater, and a mixed water of two or more of these. From the viewpoint that the effect of the acidic water neutralizing agent is remarkably exhibited, the pH of the acidic water to be treated may be 4 or less, or may be in the range of 4 to 6.

  Various magnesium compounds such as magnesium hydroxide, magnesium oxide, basic magnesium carbonate, magnesium chloride, and hydrocake are exemplified as the magnesium compound used in the preparation of the acidic water neutralizing agent. Of these, one type may be used alone, or two or more types may be used in combination. From the viewpoint of obtaining an acidic water neutralizer having an excellent neutralization rate, it is preferable to use magnesium hydroxide, magnesium oxide or a mixture thereof as the magnesium compound.

When magnesium hydroxide is used as the magnesium compound, the average particle diameter of the magnesium hydroxide contained in the acidic water neutralizing agent (after preparation) or the magnesium hydroxide used for preparing the acidic water neutralizing agent (before adjustment) is preferably Is 1 to 10 μm (more preferably 1 to 5 μm), and the Blaine specific surface area is preferably 1000 to 30000 cm ² / g (more preferably 3000 to 20000 cm ² / g). When magnesium oxide is used as the magnesium compound, the average particle diameter of the magnesium oxide contained in the acidic water neutralizing agent (after preparation) or the magnesium oxide used for preparing the acidic water neutralizing agent (before adjustment) is preferably 1 to 1. 10 μm (more preferably 1 to 5 μm), and the Blaine specific surface area is preferably 1000 to 30000 cm ² / g (more preferably 3000 to 20000 cm ² / g).

  Various ammonium salts such as diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, ammonium dihydrogen phosphate, ammonium hydrogen carbonate, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium fluoride, etc. Is mentioned. Of these, one type may be used alone, or two or more types may be used in combination. From the viewpoint of obtaining an acidic water neutralizing agent having an excellent neutralization rate, it is preferable to use ammonium chloride, diammonium hydrogen phosphate, ammonium carbonate, ammonium dihydrogen phosphate, ammonium hydrogen carbonate or a mixture of two or more thereof. . The ammonium salt is not capable of neutralizing the acidic water itself.For example, diammonium hydrogen phosphate is a substance whose aqueous solution is neutral, and ammonium chloride and ammonium dihydrogen phosphate are acidic Respectively.

  In the acidic water neutralizing agent according to the present embodiment, the ratio B / A of the mole number B of ammonium contained in the ammonium salt to the mole number A of magnesium contained in the magnesium compound may be more than 0 and 0.5 or less. preferable. It is preferable to obtain a neutralizing agent for acidic water by mixing a magnesium compound and an ammonium salt such that the molar ratio B / A falls within this range. When the ratio B / A is 0.5 or less, generation of ammonia gas in the neutralization treatment of acidic water can be sufficiently suppressed. The value of the ratio B / A is more preferably 0.01 to 0.3, and still more preferably 0.03 to 0.2, from the viewpoint of obtaining an acidic water neutralizer having an excellent neutralization rate.

  The acidic water neutralizing agent according to the present embodiment may be composed of a magnesium compound and an ammonium salt, and may further include another component (additive). The total amount of the magnesium compound and the ammonium salt in the acidic water neutralizing agent may be appropriately set depending on the application and use conditions, and is, for example, 50 parts by mass or more, and 75 parts by mass or more based on 100 parts by mass of the acidic water neutralizing agent. You may. Slaked lime etc. are mentioned as an additive mix | blended with an acidic water neutralizing agent.

  The method for preparing the acidic water neutralizing agent is not particularly limited, and the weighed components (magnesium compound, ammonium salt, and additives to be blended if necessary) may be put into a mixer and mixed for a predetermined time. . The acidic water neutralizer may be in the form of powder, granules, or slurry. In order to obtain a slurry-like acidic water neutralizing agent, a powdery or granular acidic water neutralizing agent may be added to a dispersion medium (eg, water), and the resulting liquid may be stirred. Note that a dispersant may be added so that the solid content does not precipitate in the slurry-like acidic water neutralizing agent.

<Acid water neutralization method>
The method for neutralizing acidic water according to the present embodiment includes a step of adding the neutralizing agent for acidic water to acidic water to be neutralized. By using the neutralizing agent for acidic water according to the present embodiment, the acidic water can be neutralized with a sufficiently small amount of use. For example, when a neutralizing agent for acidic water is added to the acidic water contained in the tank, the neutralization reaction can be advanced by stirring the liquid in the tank. When a neutralizing agent for acidic water is added to the acidic water flowing in the pipe, the liquid flows in the pipe, and the two are mixed, so that the neutralization reaction proceeds.

Although it depends on the type of the acidic water and the level of the neutralization treatment, the mass of the neutralizing agent added to 1 L of the acidic water is preferably 0.01 to 0.05 mol / L, more preferably 0.02 to 0.05 mol / L. 0.035 mol / L. When the amount of the neutralizing agent added is 0.01 mol / L or more, the neutralization treatment can be completed in a sufficiently short time. The quantity of goods can be reduced sufficiently. From the same viewpoint, the amount of magnesium added to 1 L of acidic water is preferably 10 × 10 ⁻³ to 50 × 10 ⁻³ mol / L, and more preferably 20 × 10 ^{−3 to} 35 × 10 ⁻³ mol. / L, and the addition amount of the ammonium salt added to 1 L of acidic water is preferably 0.1 × 10 ^{−3 to} 25 × 10 ⁻³ mol / Lg, and more preferably 0.2 × 10 ^−3. 〜１０10 × 10 ⁻³ mol / L.

  Hereinafter, the present invention will be described in detail with reference to examples.

<Material used>
Magnesium hydroxide (natural brucite made in China) and magnesium oxide (light fired magnesium oxide made by Ube Materials Co., Ltd.) were used as magnesium compounds. Table 1 shows the physical properties and the chemical components.

The Blaine specific surface area was measured using a Blaine air permeable fineness meter (manufactured by Tsutsui Physical and Chemical Instruments). The porosity was set to 0.44, and the measurement was performed by weighing the sample so as to fill the sample to the same extent as the calibration sample. The Blaine specific surface area was calculated from the measurement results using the following equation (1).
S = 1392.51 / ρ × (e ^3/2 / (1-e)) × t ^1/2 (1)
S: Blaine specific surface area (cm ² / g)
ρ: density (g / cm ³ )
e: Sample porosity
t: time (s)

  The average particle diameter was measured using a laser diffraction type particle size distribution analyzer (manufactured by Shimadzu Corporation, SALD-2200). Ethanol was used as a solvent for dispersing the sample. Before the measurement, the sample was irradiated with an ultrasonic wave for 1 minute to disperse the sample in a solvent and measured.

  The reagents shown in Table 2 (manufactured by Wako Pure Chemical Industries, Ltd.) were used as ammonium salts.

<Preparation of simulated wastewater>
Simulated wastewater having a pH of 2.5 was prepared by adding a 1N aqueous sodium hydroxide solution to a solution obtained by dissolving the following reagents in 1 L of water.
・ 1.58 g of ferrous sulfate (special grade manufactured by Wako Pure Chemical Industries, Ltd.)
1.75 g of aluminum sulfate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.)
・ Manganese sulfate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) 0.012 g
・ Zinc sulfate (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) 0.0057g
・ 95% sulfuric acid (Wako Pure Chemical Industries Ltd. special grade) 0.68g

<Preparation of neutralizing agent>
(Comparative Example 1)
After adding 140 g of magnesium hydroxide to 1 L of water, the mixture was stirred for 24 hours to prepare a slurry-like neutralizing agent.

(Comparative Example 2)
After 140 g of magnesium oxide was added to 1 L of water, the mixture was stirred for 24 hours to prepare a neutralizing agent in the form of a slurry.

(Example 1)
After 140 g of magnesium hydroxide and 1.58 g of diammonium hydrogen phosphate were added to 1 L of water, the mixture was stirred for 24 hours to prepare a neutralizing agent in the form of a slurry.

(Example 2)
A slurry-like neutralizing agent was prepared in the same manner as in Example 1 except that the addition amount of diammonium hydrogen phosphate was changed to 7.9 g instead of 1.58 g.

(Example 3)
A slurry-like neutralizing agent was prepared in the same manner as in Example 1 except that the addition amount of diammonium hydrogen phosphate was changed to 15.8 g instead of 1.58 g.

(Example 4)
A slurry-like neutralizing agent was prepared in the same manner as in Example 1 except that the addition amount of diammonium hydrogen phosphate was changed to 31.6 g instead of 1.58 g.

(Example 5)
A slurry-like neutralizing agent was prepared in the same manner as in Example 1 except that the amount of diammonium hydrogen phosphate added was changed to 47.4 g instead of 1.58 g.

(Example 6)
After adding 140 g of magnesium hydroxide and 1.32 g of ammonium chloride to 1 L of water, the mixture was stirred for 24 hours to prepare a slurry-like neutralizing agent.

(Example 7)
A slurry neutralizing agent was prepared in the same manner as in Example 6 except that the amount of ammonium chloride added was changed to 6.6 g instead of 1.32 g.

(Example 8)
A slurry-like neutralizing agent was prepared in the same manner as in Example 6, except that the amount of ammonium chloride added was changed to 13.2 g instead of 1.32 g.

(Example 9)
A slurry-like neutralizing agent was prepared in the same manner as in Example 6, except that the amount of ammonium chloride added was changed to 26.4 g instead of 1.32 g.

(Example 10)
After 140 g of magnesium hydroxide and 1.14 g of ammonium carbonate were added to 1 L of water, the mixture was stirred for 24 hours to prepare a slurry-like neutralizing agent.

(Example 11)
A slurry-like neutralizing agent was prepared in the same manner as in Example 10 except that the amount of ammonium carbonate added was changed to 11.4 g instead of 1.14 g.

(Example 12)
After adding 140 g of magnesium hydroxide and 2.81 g of ammonium dihydrogen phosphate to 1 L of water, the mixture was stirred for 24 hours to prepare a slurry-like neutralizing agent.

(Example 13)
A slurry-like neutralizing agent was prepared in the same manner as in Example 12 except that the amount of ammonium dihydrogen phosphate added was changed to 28.2 g instead of 2.81 g.

(Example 14)
After adding 140 g of magnesium hydroxide and 1.94 g of ammonium bicarbonate to 1 L of water, the mixture was stirred for 24 hours to prepare a neutralizing agent in the form of a slurry.

(Example 15)
After 140 g of magnesium oxide and 1.88 g of ammonium carbonate were added to 1 L of water, the mixture was stirred for 24 hours to prepare a slurry-like neutralizing agent.

(Evaluation of neutralizing agent by neutralization test)
Using the neutralizing agents of Comparative Examples 1 and 2 and Examples 1 to 15, neutralization tests of simulated mine wastewater (acidic water) were performed as follows. That is, 500 mL of the simulated mine wastewater was taken into a beaker, and 6.5 g of the slurry-like neutralizing agent was used in Comparative Example 1 and Examples 1 to 14 while being stirred with a magnetic stirrer. 4.5 g of the slurry-like neutralizing agent were added in each case. After the addition of the neutralizing agent, the pH of the simulated wastewater was measured every minute with a pH meter while stirring was continued. The measurement was continued until 1 hour after the addition. The time until the pH reached 7 was read, and the time was defined as the “neutralization time” and used as an index of the neutralization rate. The pH value one hour after the addition of the neutralizing agent was read, and this was taken as the “end of neutralization” and used as an index of neutralization performance.

(Measurement of precipitation amount)
One hour after the addition of the neutralizing agent, stirring was stopped, and a coagulant was added to coagulate the neutralized precipitate. The wastewater neutralized together with the precipitate was transferred to a measuring cylinder and allowed to stand overnight. After standing, the amount of sediment deposited was read, and this was converted to per liter of wastewater to obtain the sediment volume. Thereafter, the precipitate was collected by filtration and dried overnight in a dryer. The mass of the precipitate was measured, and this was converted to 1 L of wastewater to obtain the mass of the precipitate.

  As shown in Table 3, the neutralization time of the neutralizing agent composed of magnesium hydroxide and various ammonium salts (Examples 1 to 14) was shorter than that of magnesium hydroxide alone (Comparative Example 1). The neutralizing agent comprising magnesium oxide and ammonium carbonate (Example 15) also had a shorter neutralization time than magnesium oxide alone (Comparative Example 2).

Claims (7)

A magnesium compound and an ammonium salt seen including,
The neutralizing agent for acidic water , wherein the magnesium compound is one or more of magnesium hydroxide and magnesium oxide . ^{2. The} neutralizing agent for acidic water according to claim 1 , wherein the magnesium hydroxide has an average particle diameter of 1 to 10 μm and a Blaine specific surface area of 1,000 to 30,000 cm ² / g. Said magnesium oxide has an average particle size of 1 to 10 [mu] m, Blaine specific surface area of 1000~30000cm ² / g, the acid water neutralizing agent according to claim 1 or 2. The ammonium salt according to any one of claims 1 to 3 , wherein the ammonium salt is at least one selected from the group consisting of diammonium hydrogen phosphate, ammonium chloride, ammonium carbonate, ammonium dihydrogen phosphate and ammonium hydrogen carbonate. Neutralizer for acidic water. The ratio B / A of the number of moles B of ammonium contained in the ammonium salt to the number of moles A of magnesium contained in the magnesium compound is more than 0 and 0.5 or less, according to any one of claims 1 to 4. The neutralizing agent for acidic water according to 1. A method for neutralizing acidic water, comprising a step of adding the neutralizing agent for acidic water according to any one of claims 1 to 5 to acidic water to be neutralized. The acidic water neutralization method according to claim 6 , wherein the acidic water has a pH of 5 or less and is at least one selected from mine wastewater, river water, and groundwater.