JPS6130639B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a seed crystal material for crystallization treatment for crystallizing and separating a phosphorus compound dissolved in a liquid, and particularly for use in sewage water. The present invention relates to a method for producing a crystallization material suitable for efficiently crystallizing phosphorus compounds contained in industrial wastewater.

Various types of wastewater discharged to natural water systems contain phosphorus compounds in various forms such as inorganic orthophosphates, various condensed phosphates, and organic phosphates. The existence of rivers,
It is a major cause of eutrophication in closed water bodies such as lakes and inner bays.

A crystallization treatment method is one of the methods for removing phosphorus compounds dissolved in these liquids. In this method, water to be treated whose pH has been adjusted to 7 or higher in the presence of calcium ions is passed through a packed bed of phosphate rock whose main component is calcium phosphate salt, and the phosphate in the liquid is converted to calcium phosphate and applied to the surface of the phosphate rock. It is basically based on precipitation. At this time, phosphate rock acts as a seed crystal material, and an intermediate product of a calcium phosphate compound is initially formed on the surface of phosphate rock, but it is said to change into stable hydroxyapatite over time. This crystallization treatment method has the advantages of generating little sludge and simple treatment operations, and has recently been adopted as a tertiary treatment for sewage with relatively low phosphoric acid concentrations. .

By the way, this crystallization treatment method is difficult because the naturally produced phosphate rock that is the seed crystal material is relatively expensive, contains impurities, so the ability to treat phosphate in the liquid is not constant, and the treatment process is difficult during operation. This method had drawbacks such as a decrease in performance. In addition, the composition and properties of phosphate rock itself vary significantly depending on the production area, and there have been problems with unstable factors in terms of performance guarantee and suitability of physical properties as a filler.

An object of the present invention is to eliminate the drawbacks of the above-mentioned prior art and to provide a method for producing a seed crystal material for crystallizing phosphorus in a liquid that is stable and has stable processing performance in place of the above-mentioned phosphate rock. .

In order to achieve this objective, the method for producing a seed crystal material according to the present invention includes depositing at least one calcium compound selected from calcium chloride, calcium hydroxide, and calcium oxide on a carrier, and then
It is characterized by heating at 120 to 200°C to fix the calcium compound on the carrier.

Here, the term "carrier" refers to a granular material (spherical or crushed) that becomes the base of the seed crystal material, and in particular, a water-insoluble material is selected from among magnesium compounds, aluminum compounds, and zirconium compounds. be done. For example, seawater magnesia/clinker, fused magnesia/clinker, etc.
Clinker, activated alumina, Kanuma soil, zirconia,
Examples include magnesium hydroxide. In other words, these compounds have a strong affinity with phosphates, and when seed crystal materials containing these compounds as carriers are used for crystallizing phosphates in a liquid, it is necessary to Because of its good properties, calcium phosphate is efficiently crystallized on the surface of the carrier by synergistically with the fixed calcium compound described below and calcium ions coexisting in the liquid. Figure 1 shows adsorption isotherms for phosphoric acid on various carriers. From FIG. 1, it can be seen that the amount of phosphorus adsorbed by magnesium oxide, aluminum oxide, and zirconium hydroxide according to the present invention is large, and these carriers have a strong affinity for phosphate.

As a method for attaching the calcium compound to the carrier, a method of immersing the carrier in an aqueous solution of the calcium compound is preferably used. For example, 0.01 to 10
% calcium compound solution for 10-100 hours. In this treatment, by immersing the carrier in a calcium compound solution with a concentration as low as possible for as long as possible, adhesion of the calcium compound to the carrier becomes more sufficient. The amount of calcium compound deposited is preferably 2 to 50 mg per gram of carrier. In other words, if the amount attached is too small, the activity as a seed crystal material will decrease, and if it is too large, the attached calcium compound will cover the surface of the carrier, making it impossible to fully utilize the affinity of the carrier for phosphorus compounds. The activity as seed material is similarly reduced. If the above-mentioned treatment for adhering calcium compounds to the carrier is not enough, when this is used for the crystallization treatment of phosphorus in the liquid,
Calcium compounds easily dissolve and leave the liquid,
Not suitable as seed crystal material. For this reason, a calcium compound fixing treatment is next performed. That is, the carrier to which the calcium compound is attached by the immersion is dried and then heated. Drying may be carried out in the sun, but forced drying at a temperature of 80 to 110°C is preferable. Heating is performed at 120 to 200°C for about 2 hours. Heating temperature is 120
If the temperature is less than 0.degree. C., the fixation of calcium compounds will be insufficient. Even if heated above 200℃, the above 120~200℃
It shows only the same crystallization treatment performance as when heated at . Therefore, heat treatment at temperatures exceeding 200°C is disadvantageous in terms of energy conservation.

Another method for fixing the calcium compound may be to thoroughly mix a fine powder of the calcium compound with a carrier and heat the mixture.

The carrier on which the calcium compound is fixed as described above exhibits properties suitable as a seed crystal material for crystallizing phosphorus in a liquid.

In other words, the seed crystal material resulting from the present invention has a wide selection of carriers, has uniform natural or artificial properties, can be used at low cost, and can uniformly fix calcium compounds. It is chemically uniform and exhibits stable processing performance. Further, by arbitrarily selecting the particle size, particle size, specific gravity, mechanical strength, etc. of the body, it can be filled with seed crystal material and used as a fixed bed or a fluidized bed.

Example 1 Seawater magnesia clinker having a particle size of 0.3 to 0.6 mm was immersed in a 0.1% calcium chloride aqueous solution for 30 hours. Next, this immersed carrier was drained, dried, and heated in a constant temperature bath at 120° C. for 2 hours to obtain a seed crystal material. A column filled with this seed crystal material has a phosphorus concentration of approximately 3.0 mg/, a calcium concentration of 35 to 45 mg/
The phosphorus removal performance was investigated by passing simulated secondary treated sewage water adjusted to pH 8.0 to 8.5 at SV = 4 h ^-1 . As a result, the phosphorus concentration in the treated water was 0.3mg/
The phosphorus removal performance was stable even after long-term operation.

Example 2 A seed crystal material was produced under the same conditions as in Example 1, except that aluminum oxide hydrate was used as a carrier, and a water flow experiment was conducted under the same conditions. As a result, the phosphorus concentration in the treated water showed a value of around 0.4mg/continuously.

Example 3 A seed crystal material was produced under the same conditions as in Example 1, except that zirconium oxide hydrate was used as a carrier, and a water flow experiment was conducted under the same conditions. As a result, the phosphorus concentration in the treated water continuously showed a value of around 0.3mg/.

Example 4 Seawater magnesia clinker granules (particle size 0.3
~0.6mm) as a carrier, mix quicklime fine powder (particle size 30-80μm) at a ratio of 5% based on the dry weight of the carrier, and heat it at 180℃ for 2 hours to obtain seed crystal material. And so. As a result of a water flow experiment using this seed crystal material under the same conditions as in Example 1, the phosphorus concentration in the treated water showed a high value of around 1.2 mg/kg at the beginning of operation, but after 72 hours of operation, The phosphorus concentration is
The amount was around 0.5mg/, and stable phosphorus removal performance was shown thereafter.

Comparative Example Except for using river sand and activated carbon as carriers,
A seed crystal material was produced under the same conditions as in Example 1, and a water flow experiment was conducted under the same conditions. As a result, the phosphorus concentration in the treated water was around 1.6 mg/d, and this value did not change even after 1500 hours of operation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing phosphorus adsorption isotherms of various carriers.

Claims (1)

[Claims] 1. At least one calcium compound selected from calcium chloride, calcium hydroxide, and calcium oxide is attached to a granular carrier selected from water-insoluble magnesium compounds, aluminum compounds, and zirconium compounds. After, 120~200℃
1. A method for producing a seed crystal material for crystallizing phosphorus in a liquid, the method comprising heating the seed crystal material to fix the calcium compound to the carrier. 2 immersing the carrier in a calcium chloride solution,
2. The method for producing a seed crystal material according to claim 1, wherein calcium chloride is fixed to the carrier by heating.