JPH105771A - Dephosphorizing agent and production thereof and dephosphorizing method of discharge water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dephosphorizing agent capable of producing it at a low cost and easy in handling by preparing the dephosphorizing agent consisting of a gelled product of MgCl2 as an effective utilizing composition. SOLUTION: The dephosphorizing agent used to purify waste water, discharge water, contaminated water, and sewerage water, etc., containing a phosphorus compound, is prepared by using the gelled product of MgCl2 . A suspension liquid of calcined magnesia is added hydrochloric acid, then is stirred at a state as it is or at a heated state and is left as it is, thus the solution gradually loses fluidity to become a gelled state, and this product is used as the gelled product. In a dephosphorizing treatment of the phosphorus-containing discharge water, the gelled product of MgCl2 is added to the discharge water to treat so as to allow the liquid to react in an alkaline region. Thus, the phosphorus present in water to be treated is adsorbed or a phosphorus quantity in the liquid is reduced by reacting with the phosphorus.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for purifying wastewater, wastewater, sewage, sewage, sewage and the like containing phosphorus compounds (hereinafter abbreviated as phosphorus) generated in various industries and daily life. The present invention relates to a dephosphorizing agent to be obtained and a method for producing the same, and a dephosphorizing method for removing and purifying phosphorus in the water to be treated using the above-mentioned dephosphorizing agent.

[0002]

2. Description of the Related Art In recent years, eutrophication in rivers, lakes and marshes or enclosed sea areas has become a problem, and nitrogen and phosphorus drainage regulations have been implemented in order to preserve these water environments. Waste liquids and wastewater containing compounds are required to be properly treated and then discharged as wastewater with a concentration lower than the concentration specified by law. In order to prevent the above-mentioned inflow of phosphorus into the water area, various measures have been studied, and some of them have already been put into practical use.

[0003] The following methods have been known to reduce phosphorus in wastewater. A chemical coagulation sedimentation method in which a coagulant consisting of a metal salt of aluminum, iron, calcium, magnesium or the like is added to the water to be treated and coagulated and precipitated together with phosphorus. A biological treatment method that combines aerobic and anaerobic conditions and removes phosphorus with activated sludge. A selective ion exchange method in which phosphorus is adsorbed and removed by contact with activated alumina. A catalytic dephosphorization method in which phosphorus is crystallized as calcium hydroxyapatite by applying the principle of phosphate rock formation. Although these methods may be used alone, they are often implemented in combination.

[0004] Among the above-mentioned known dephosphorization methods, the chemical coagulation-sedimentation method is one of the methods that have been practically used for a long time. However, the following problems have been pointed out in the chemical coagulation precipitation method regardless of the coagulant used. Generally requires a large amount of coagulant and high processing cost. A large amount of sludge is generated in proportion to the chemical used, and the sedimentation and concentration of the sludge are extremely poor. The sludge generated has low dewatering properties. For this reason, the construction of the treatment facility has many problems, such as requiring a large amount of land and high construction costs, as well as costs for treatment.

[0005]

An object of the present invention is to provide a novel dephosphorizing agent and a method for producing the same, and a dephosphorizing method using the above-mentioned dephosphorizing agent. The aforementioned dephosphorizing agent was intended to be relatively inexpensive to manufacture and easy to handle.

[0006] The precipitate formed by the present invention is:
It has good cohesiveness and sedimentation, and can be easily separated by a separation device such as a filter.

Furthermore, the dephosphorization method of the present invention can be used essentially in the same manner as the conventional chemical coagulation-sedimentation method, existing equipment can be used, and no special equipment is required. One of the purposes is to make it applicable.

[0008]

In order to solve the above-mentioned problems, the present invention has been studied in various ways, and uses a gelled product of magnesium chloride as a dephosphorizing agent.

The above-mentioned gelled product is obtained by adding hydrochloric acid to a suspension of lightly burned magnesium, stirring the solution as it is or after heating, and then leaving the solution to gradually lose its fluidity and cause gelation. Use this as it will be A gel is formed by mixing lightly-baked magnesium and hydrochloric acid in this way and leaving the mixture. The components of lightly-baked magnesium, magnesium oxide (MgO) and hydrogen chloride (HCl), are formed.
And the reaction is considered to be mostly magnesium chloride, which is considered to be polymerized and gelled, but the details of the mechanism of gelation are unknown.

[0010]

The present invention relates to a dephosphorizing agent containing a gelled product of magnesium chloride as an active ingredient, and a dephosphorizing agent obtained by dispersing the gelled product in water.

[0011] Further, a method for producing a dephosphorizing agent characterized by gelling a solution consisting of lightly burned magnesium and hydrochloric acid, and, after gelling a solution consisting of lightly burned magnesium and hydrochloric acid as described above, A method for producing a dephosphorizing agent, comprising dispersing the gelled substance in water.

Further, a method of dephosphorizing wastewater in which a gelled product of magnesium chloride is added to the phosphorus-containing wastewater to make the liquid property react in an alkaline region, and in the above-described dephosphorization method, the gelled product of magnesium chloride is prepared in advance. This is a method in which the water is adjusted to be dispersed in water and added.

As the dephosphorizing agent of the present invention, a gelled product of magnesium chloride is used, which can reduce the amount of phosphorus in the liquid by adsorbing or reacting with phosphorus present in the water to be treated. In both cases where the solution is partially gelled and the whole is in a gelled state, it works effectively as a dephosphorizing agent, and when the gelled one is directly dispersed and used, the amount of drainage is Can be selected as appropriate according to the advantages and disadvantages and the use situation. However, since the dephosphorization effect is better when the whole is gelled than when a part is gelled, it is desirable to use a gelled one as much as possible.

The raw materials necessary for producing the gelled magnesium chloride used in the present invention are lightly burned magnesium and hydrochloric acid. Light fired magnesium used as a raw material
A basic component that is often produced in China is obtained by calcining MgCO ₃ magnesite with a kiln or the like, and is commercially available as a powder.
Although it contains magnesium oxide (MgO) mostly, although containing some impurities, lightly burned magnesium is less expensive than magnesium oxide such as ordinary industrial materials and reagents. Light calcined magnesium can be used as it is, and it is preferable to use as fine a powder as possible in order to accelerate the reaction, and it is desirable to use those having an average particle size of about 50 μm or less.

It is needless to say that the hydrochloric acid preferably has as few impurities as possible, but is not particularly limited, and a normal industrial-grade hydrochloric acid can be used.

Next, a method for producing a gelled product of magnesium chloride will be described. Since the solubility of MgO that constitutes lightly burned magnesium is low, when lightly burned magnesium powder is put into water, it becomes a suspended state.Hydrochloric acid is added to this lightly burned magnesium suspension to remove magnesium chloride. To be generated.

At this time, the ratio between the two is preferably 1: 1 to 1: 2, more preferably 1: 1.5 to 1 in a molar ratio of Mg: Cl.
When the ratio is in the range of 1: 1.7, gelation easily occurs. Further, when the concentration of the generated magnesium chloride is low, the gelation does not proceed, so that the magnesium chloride concentration is desirably 10 to 30% by weight.

Since the molar ratio of Mg: Cl in the production of the gelled product is lower than 1: 2 in the case of MgCl ₂ , there is a possibility that unreacted light-burned magnesium remains, but it is actually removed. When the phosphorus reaction is performed, an alkaline compound is added and the reaction is performed in a region where the liquidity is in an alkaline range. Therefore, there is no problem even if the unreacted light-burned magnesium remains.

Lightly-baked magnesium and hydrochloric acid are mixed and gelled by being left at about room temperature for about 10 hours. At this time, if the proportion of the lightly burned magnesium is small, the gelation remains in a part, or it takes time until the whole is gelled. Therefore, it is desirable to set the mixing ratio of the two as described above. In addition, by heating the mixture at the time of mixing the lightly burned magnesium and hydrochloric acid and keeping the solution warm, the gelation reaction is promoted and the gelation takes place in a short time of about 2 hours. At this time, a temperature of about 80 ° C. or less is sufficient.

The gelled product of magnesium chloride obtained as described above, if the amount of lightly burned magnesium used is large and the concentration is high, the gelation proceeds and becomes agar-like, so that the dephosphorization is required. May be transferred as it is, finely divided on the spot, and then dispersed and added to the phosphorus-containing wastewater. It may be used in a state where it is once transferred into a liquid, stirred vigorously therein, and dispersed in water. In any form, it effectively acts as a dephosphorizing agent, and the dephosphorization reaction proceeds.

In the dephosphorization method of the present invention, a gelled product of magnesium chloride is added to a phosphorus-containing wastewater, and an alkaline compound is added and reacted in an alkaline region.
The resulting sediment has good sedimentation properties, and the sediment is settled to the bottom of the container only by standing still. The alkaline region is desirably in a pH range of 8 to 10. As a result, the separability of the precipitate is good, and the sediment can be easily separated by a separation device such as a filter, and the water content can be reduced. In addition, depending on the alkaline compound to be added, the pH immediately after the addition may be lower than the above range due to solubility and the like, but if the pH is in the above pH range at the end of the reaction, the dephosphorization effect will not be obtained. Is recognized.

Examples of the alkaline compound used to make the liquid property in the alkaline region in the dephosphorization reaction include sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium carbonate, potassium carbonate, lightly burned magnesium and the like. Basically, a known alkaline compound can be used since it is basically required that the liquidity be in the alkaline region. Among these, it is desirable to use lightly burned magnesium or a magnesium compound from the viewpoint of the raw material.

The amount of phosphorus contained in the wastewater is not limited in principle, but may range from a high concentration of several thousand ppm to a relatively low concentration of several tens ppm as phosphorus. Is also applicable. The phosphorus removing agent may be added so that the molar ratio of Mg / P becomes 1.5 or more with respect to the amount of phosphorus in the water to be treated, and the reaction may be performed for 1 hour or more, preferably 2 hours or more. At this time, the reaction time can be shortened by heating the solution or increasing the amount of the dephosphorizing agent added.

[0024]

【Example】

Example 1 The following A and B were prepared using lightly burned magnesium powder (MgO 91 wt%, average particle size 40 μm) and 36 wt% hydrochloric acid.
A gel of magnesium chloride was produced under the following conditions. A: Water, lightly burned magnesium and hydrochloric acid in a container, Mg: Cl
Was added at a molar ratio of 1: 2 so that the concentration of generated magnesium chloride became 20 wt%, and the mixture was stirred at 50 ° C. for 2 hours, and a part of the liquid was gelled. B: Water, lightly burned magnesium and hydrochloric acid in a container, Mg: Cl
At a molar ratio of 1: 1.6 so that the concentration of magnesium chloride formed becomes 17 wt%.
After being stirred for 16 minutes and left standing for 16 hours, the whole liquid in the container gelled.

The waste liquid containing the phosphorus-containing organic compound is spray-roasted by the submerged combustion method, and the P concentration of the wastewater passing through the exhaust gas generated at that time is 990 mg / liter, and the temperature of the liquid is 80 to 90 ° C. there were. A test for dephosphorization was performed on the wastewater under the conditions described in the table, and the results are also shown in the table. In the dephosphorization test, a part of the test was performed at a liquid temperature of 80 ° C. and a room temperature of 20 ° C. In addition, the addition amount of the phosphorus removing agent was represented by the molar ratio of Mg and Ca of the phosphorus removing agent to P in the wastewater.

[0026]

【table】

The sediment after the test had good sedimentation properties and settled at the bottom of the container only by standing for a while, and was easily filtered with ordinary filter paper, and the precipitate was easily peeled off from the filter paper.
The analysis of phosphorus was performed by molybdenum blue (ascorbic acid reduction) absorption spectrophotometry.

Example 2 A gel of magnesium chloride was produced from the same lightly burned magnesium powder and hydrochloric acid used in Example 1 under the following condition C: C: Water, lightly burned magnesium and hydrochloric acid in a container, Mg: Cl
Was added at a molar ratio of 1: 1.6 so that the concentration of generated magnesium chloride was 17 wt%, and the mixture was stirred at 60 ° C. for 2 hours, and the whole liquid gelled. Phosphate ions _(PO ^{4 3-)} to adjust the phosphorus-containing waste water which contains such a 20mg / l as P concentration. A phosphorus removal test was performed on the phosphorus-containing wastewater under the conditions described in the table, and the results are shown in the table.

Comparative Examples 1 and 2 For the same wastewater having a P concentration of 990 mg / liter as used in Example 1, lightly burned magnesium powder and calcium chloride (CaCl ₂ ) were separately added as dephosphorizing agents to remove water. A phosphorus test was performed. Conditions and results are shown in the table.

The floc remaining in the liquid afterwards was poor in sedimentation with only lightly burned magnesium and could not be easily separated only by standing still. Further, the filterability of the precipitate was poor, and suction filtration was required. In the case of calcium chloride, the precipitate was fine and filtration was difficult.

[0031]

The dephosphorizing agent of the present invention is manufactured using relatively inexpensive raw materials, so that it has excellent economical efficiency and
Since it is non-toxic and agar-like or liquid, it is easy to handle. The precipitate formed by the dephosphorization method of the present invention has a high cohesive property and a good sedimentation property, so that it can be easily separated by a separating device such as a filter, and when a conventional aluminum-iron coagulant is used. The moisture content can be lower than that.

Further, since the dephosphorization method of the present invention can be used in the same manner as the conventional chemical coagulation precipitation method, it can be easily applied without using any special apparatus.

Claims (6)

[Claims] 1. A dephosphorizing agent comprising a gelled product of magnesium chloride as an active ingredient. 2. A dephosphorizing agent obtained by dispersing a gelled product of magnesium chloride in water. 3. A method for producing a dephosphorizing agent, wherein a solution comprising lightly burned magnesium and hydrochloric acid is gelled. 4. A method for producing a dephosphorizing agent, comprising: gelling a solution comprising lightly burned magnesium and hydrochloric acid; and dispersing the gelled product in water. 5. A method for removing phosphorus from waste water, comprising adding a gelled product of magnesium chloride to the phosphorus-containing waste water and reacting the solution in an alkaline region. 6. A method for removing phosphorus from wastewater, comprising adding a liquid in which a gelled product of magnesium chloride is dispersed in water to the phosphorus-containing wastewater, and reacting the solution in an alkaline region.