JPS601069B2 - Method for removing phosphates from wastewater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for removing phosphates from wastewater using calcined coral fossils as a treatment agent for phosphate-containing wastewater.

There are coral reef producing areas near the Ryukyu Islands, and the mineable reserves are estimated to be 5 tons, and it is expected that they will be put to effective use as a rich resource.

Coral fossils are mainly composed of calcite and contain some mist, and are composed of corals, foraminiferal calcareous algae, and mollusk remains from the Quaternary geological period, and are extremely porous. It is a fossil. An example of chemical analysis of coral fossils is shown in Table 1 below. Table 1: Menkoshi P205 Hada Gunma 2.

3Fe203Ca.

MgOS. 8 Na20K20 total 47.7 0.6
7 2.2 1.2 0.4 53
．． 2 1.2 0.3 0.17 0.07
100 The applicant is currently researching and developing the use of calcined coral fossils as a remover for heavy metals in wastewater, and is researching whether it can also be used as a remover for phosphates in wastewater. They found that it can be used and completed the present invention.

Conventionally, in the treatment of wastewater containing phosphates, it has been common to use lime to precipitate and remove calcium phosphate salts.

Since calcium salts of phosphoric acid have lower solubility in water than alkaline salts, they can be removed by sedimentation, but at least an amount corresponding to the solubility of the calcium salts remains in the wastewater. It also has the disadvantage of forming a precipitate that is difficult to settle and floating. In order to substantially completely remove phosphates from wastewater, adsorbents such as activated carbon can be used to remove them by adsorption, but activated carbon is expensive.

There is a need in the industry for an inexpensive removal agent that removes the small amounts of phosphates that remain after neutralization with lime.

It is an object of the present invention to provide an inexpensive method for removing phosphates in response to this demand. The present invention provides a method for removing phosphates from wastewater, which comprises burning coral fossils that do not substantially contain salt at a temperature of 300 to 500 oo and using the resultant as a treatment agent for wastewater containing phosphates. do.

For firing coral fossils, the coral fossils are washed with water, preferably hot water to remove salt, then fired at 300 to 500°C, cooled, and then crushed into a size suitable for usage conditions.

It is preferable to change the particle size depending on whether it is used packed in a tower or mixed in a kettle with a pestle.The particle size can be determined according to the purpose of use.30
Coral fossils fired below 0.000 have weak adsorption capacity.

Coral fossils fired at a temperature of 50,000 or more have a reduced adsorption capacity. Example 1 10, 25, and 50 g of calcined coral fossil particles having a particle size of 250 to 840 French m were used for 500 test liquids.

The test solution was trisodium phosphate (Na3P04.1
2nd day 20) as P04 and the pH is 2 with a target of 30 ppm.
．． Adjusted as 5. Takaazusa time of treatment tank is 1, 2, 5,
7.4 conditions were set. Concentration of stock solution used P0430.7pp
mNa24.5ppmS0417 pmThe following method was followed as an analysis method.

P04... Spectrophotometry Ca... Atomic absorption method Na... Atomic absorption method S04... Gravimetric method Amount of burned coral fossil (removal agent) used, liquid after treatment pH of
, Changes, P0 remaining in the filtrate after removal treatment
Table 2 shows the interrelationships among 4, Ca, Na, and S04.

Table 2 Removal rate by calcined coral fossil remover (batch type) Example 2 Calcined coral fossils with the same particle size as in Example 1 were packed into a column, and the liquid flow time was 1,2 at a flow rate of 760 to 800 [/h]. , 3, 4, 5, 6, 7 hours, stock solution concentration P04・
・・30.5ppmNa・・21.2ppmS04・
...3rd removal rate when using 163.4 ppm solution
Shown in the table.

Table 3: Removal rate by calcined coral fossil remover (column type) As a result of X-ray diffraction of used calcined coral fossils, it was confirmed that P04 forms a compound with Ca in addition to adsorption.

In order to check the P04 adsorption ability of the calcined coral fossil of the present invention,
As P04, 5g of calcined coral fossil was added to 500 skins with a concentration of 10,000ppm, and the result was 170 after 5 hours of worshiping.
It was confirmed that it had an adsorption removal ability of skin g/5g, that is, 340/g. Comparative Example A test was conducted to see if uncalcined coral fossils could be used to remove phosphates from wastewater in accordance with the example, but no removal was possible.

Claims (1)

[Claims] 1 300 to 5 coral fossils containing virtually no salt
A method for removing phosphates from wastewater, which comprises firing at 00°C and using the process as a treatment agent for wastewater containing phosphates.