JPS6082188A - Dephosphorizing method - Google Patents

Abstract

PURPOSE:To perform effective dephosphorizing treatment by bringing a dephosphorizing material on which a calcium phosphate crystal is precipitated into contact with an acidic soln. then lprecipitating again the calcium phosphate crystal on the surface of a carrier. CONSTITUTION:A carrier such as zeolite is first brought into contact with a soln. contg. phosphoric acid or the salt thereof to deposit phosphorus thereon and thereafter the carrier is brought into contact with a soln. contg. lime such as an aq. slaked lime soln. or the like to obtain a dephosphorizing material on which a calcium phosphate crystal is precipitated. Water contg. phosphoric acid is passed through the packed bed in which the above-described dephosphorizing material is packed, in the presence of calcium ion, to precipitate the phosphate ion on the dephosphorizing agent in the form of hydroxy apatite. The dephosphorizing agent of which the performance is deteriorated after the agent is subjected continuously to a dephosphorizing operation is brought into contact with the acidic soln. to dissolve away the calcium phosphate crystal precipitated on the carrier surface as best as possible.

Description

Detailed Description of the Invention This invention relates to a dephosphorization method for treating water containing phosphates.In recent years, the progress of eutrophication has become a serious problem in closed water bodies such as lakes and inner bays. has been done. Phosphate present in water has been highlighted as a cause of eutrophication, and its removal is being taken as an urgent issue.

Phosphates that cause eutrophication are inorganic phosphates such as orthophosphates and motion table phosphates, which are found in tap water, sewage, industrial water, factory sail water, boiler water, etc. It exists in the form of salts and amorphous phosphates.

As a method for removing such phosphates, a method has been proposed in which water containing phosphates is brought into contact with silica sand containing calcium phosphates such as phosphate rock (1). =serLation Abs
Lracts International, Vol.
, 88°A, 12. Part I, 587B-8
pages, etc.). This method involves converting phosphate ions contained in water into the form of calcium phosphate such as hydroxyanotite and crystallizing it into a crystal ridge to remove the Lv, and the operating method is different from the conventional flocculation method. Not only can this method be simplified, but also the processing efficiency can be greatly improved, so it has been particularly noted in recent years.

By the way, natural phosphate rock is mainly used for the Ail crystal building, but the supply of phosphate rock is limited and stable supply is difficult, and the chemical composition and physical properties vary depending on the 'E7'C production area. There are differences in the dephosphorization effect, which makes it difficult to ensure stable treatment.

In order to eliminate these conventional problems, the present inventors have developed an easy-to-manufacture and efficient dephosphorization method by supporting calcium phosphate crystals on zeolite or lime. We previously proposed a dephosphorizing agent capable of dephosphorization and a dephosphorization method using the same (patent application filed in 1973).
No. 7-28178) This dephosphorizing agent can be manufactured artificially under exactly the same conditions, so it has a stable supply of +1.1 and can maintain the same level of dephosphorizing performance. Meri of Sai)'t-! It is something to do.

However, as the research continued, a major problem arose with this drug.

ν1j In the previously proposed dephosphorization method using dephosphorization hlJ, if it is continued to be used for a long period of time, for example over a year, while performing the conventional method of red activation treatment, it will gradually become reactivated. The oil level decreased, and it was finally discovered that even after reactivation treatment, sufficient performance was not achieved.

This phenomenon can be seen when raw water contains 1-1 d+ reaction inhibiting substances such as crystals such as ions and organic substances.

The present invention was completed as a result of the rapid delivery method being developed in order to overcome the problems that arose from the conventional method. In the presence of dephosphorized water containing phosphate and tl calcium ions, and p
In the dephosphorization method in which contact is made under the strip 1'F of H6 or higher, the dephosphorization material and the acid @'6! The method is characterized in that after the crystals precipitated on the surface of the carrier are melted and awned by contacting with i, the phosphor jfI calcium thread crystals are pulled out again on the surface of the carrier to dry out the dephosphorizing material. This is a dephosphorization method.

The carriers used in the present invention are limited to those having mildew resistance. Examples of such porous-resistant carriers include natural and artificial zeolites. Especially 817A l
A zeolite with a chemical composition of 3'kW or more is suitable,
Theo with this composition.

As light, mordenite, crinovnarosite, Y
It is surrounded by type zeolite etc. In particular, mordenite and kleinofcoulolite thread zeolite have a pH of about 2+ffi'! It's good because I have 1 number 1 for 1 history.

An example of a method for depositing the phosphoric acid calcium/1', #i product on the surface of this enemy-resistant carrier is the method 4) 9, which is the same as in the previous application.

That is, the above-mentioned carrier is brought into contact with a bath solution containing phosphoric acid or its salt to carry phosphorus thereon. Zeolite has the property of absorbing phosphorus from molten phosphoric acid (salt), and can easily absorb phosphorus by bringing it into contact with the phosphorus by an impregnation method or the like. As the phosphate, yuzu orthophosphates such as sodium phosphate and linbotulium can be used.

The harshness of the phosphorus bath liquid that can be felt in contact with the carrier is 100 mv.
It can be freely selected from 1/l to several tens of weight %1. The contacting operation may be either a batch operation or a continuous water method. Although it is not limited to the pH of the phosphoric acid (water bath number) of the contact point, in order to achieve good phosphorus retention, the hostile conditions must be MJ"E, 'tt, and the condition of pH 6 without dropping. Desirable.This is I) HK, l: 7 of phosphate.
'1 (F detachment 1 core is different, suction to carrier surface + IJi
This is thought to be due to the fact that the pH becomes higher at low pH.3 At pH 6 or higher, stable treated water quality is not obtained, but the water becomes more stable and distorted. Contact time is carrier, phosphate μm, concentration, p l
-1, etc., but it may take about 8 to 50 hours.

After the phosphorus loading treatment has been completed, the carrier is subjected to IL treatment with vinegar to sweeten the phosphorus.The N1 operation can be carried out using ordinary skill, and if necessary, it can be conditioned with water. The separated solution can be used in the next compatibilization operation. 2. At this time, if necessary, by adding all the phosphate, a stable supporting treatment effect can be maintained. If the next operation is carried out without dividing the solution, the phosphorus ions in the solution will react with the slaked lime and a large amount of calcium precipitate will be generated, complicating the treatment process. Moreover, at this time, since slaked lime is consumed, the required amount of slaked lime increases and processing cost increases. Furthermore, the imitation A411 flyl phosphocalcium 9 crystals, which have a weak binding force to the surface of the carrier, are attached to the surface of the carrier and are detached during use, which is undesirable because the quality of the treated young fruit deteriorates.

The completely separated carrier is brought into contact with a solution containing lime, and the phosphorus supported on the carrier surface is reacted with calcium in a numerical ratio of 7 to 7 to form crystals of dephosphorizing commercial phosphorus enemy calcium.
let As the lime-containing bath liquid, a slaked lime water bath liquid can be used, but other substances may be mixed therein. For the actual production of calcium phosphate, an amount of calcium hydroxide greater than a certain amount is required for the amount of supported phosphorus, and if this is insufficient, (all
The performance is not bad. In order to obtain a dephosphorization agent with a high removal rate under standard fL dephosphorization conditions, 4
It would be best to contact and bribe a company that produces more than twice the amount of calcium hydroxide in a car. The concentration of calcium in water in the bath solution is α1~
5-fold Monchi, contact time may be about 1 to 7 days.

Artificially dephosphorized h11 can be produced using the above method, and a method with improved dephosphorization performance has also been developed.

That is, in the above method for producing a dephosphorizing agent, prior to contacting the llj acidic carrier with a bath containing phosphoric acid or a salt thereof, contacting with calcium ra (+ = yam) is carried out to increase the calcium affinity ratio of the carrier. This is a method in which the amount of phosphoric acid is preferably 20% or more, preferably 40% or more, and then brought into contact with the above-mentioned fK solution, which refers to phosphoric acid or a salt thereof, and then brought into contact with a filtrate-containing solution.

Calcium/ill is not particularly limited as long as it is a compound that generates calcium ions, and includes, for example, calcium chloride, *saponified calcium, and the like.

It is preferable to bring the carrier into contact with a solution containing a calcium agent in advance so that the calcium release rate is at least 100%, as this dramatically improves the ability to remove calcium.

Through the above operations, the artificial dephosphorization agent used in the present invention is obtained, but the uninvention is to add phosphorus brewing salt in the presence of calcium ions to a packed bed based on the dephosphorization obtained above. This is a method of dephosphorization by tracing the water contained therein and crystallizing phosphorus ions on a dephosphorizing agent using hydroxyapatite 113.The method of using the dephosphorizing agent 11 for this method will be explained below.

The waste water to be treated in the invention is water that refers to phosphoric acid, and secondary treated water such as sewage, wastewater, and factory wastewater is used. In such a raw material 7'
The reaction that occurs at this time varies depending on the reaction conditions, but is usually expressed by the 11th equation.

5Ca"+701-1- +8) 4PO,"'-+Ca
, (OH)(P(J4) + 6 k-1, U -(1
) In order to efficiently remove phosphates from water containing phosphates, it is necessary to allow the reaction in equation (1') to proceed to the right, and for this purpose, a calcium agent or a 7K potash agent must be used. In addition, calcium agents and/or water ions must be present.

These ions are in trouble! ! If the amount increases, fine precipitates may be formed in places other than air conditioners, or precipitates of 7um carbonate may be formed, so these should be kept within a range where they will not be destroyed. be.

'T, that is, calcium ions, hydroxide ions;
11- is the hydroxyapatite produced by formula (1) whose dust absorption is lower than that of the hydroxyapatite eye skin and lower than that of the overbath 1' + skin, that is, the hydroxyapatite in the semi-animal region. is the condition that generates. Here, the concentration of crystals is the concentration at which crystals begin to precipitate when no crystal phase exists in the reaction yarn.

Increase the amount of calcium ions and hydroxide ions
Calcium supplements may be used as necessary to reduce the
'l It's cool to cool the alkaline agent into the phosphate-containing water. Calcium <1 [and preference for alkaline agents j1
The addition of %I can be predetermined in the experiment, but if the phosphate in the raw water is less than 50"f/t, the calcium ion concentration is 10-200"f/t%p.
H is about 6 to 12 drums.

Calcium agents used in the VC of this invention include calcium hydroxide and calcium chloride, and alkaline agents include sodium hydroxide, potassium XrR, and calcium hydroxide.

The contact between water, which refers to phosphate, and the dephosphorizing agent is based on the packed bed water flow system, but the dephosphorizing agent has a particle size of 9 to 85 mesh in the case of a solid bed, and 86 to 800 mesh in the case of η+, nJ bed. , and ω is launched in a countercurrent or downward flow at a speed of 8V1 to 2Qhr-' to precipitate hydroxyapatite crystals. The suspended solids are captured in the upper layer, and the crystals +J'r'! i
-Can be done.

Similarly, when water is passed in a downward flow, suspended matter may adhere to the surface of the dephosphorizing agent, so use the P chestnut, which has a smaller specific gravity and larger particle size than the dephosphorizing agent, as a dephosphorizing coating layer. Layered on top of this F
It is desirable to remove ru 1tIl substances by using materials. If the dephosphorization surface becomes contaminated or clogged during water flow, periodically remove it by backflowing it with an upward flow. It is desirable to remove. The overwatering conditions during backwashing are as follows: flow rate is about 29-g On1/br, backwashing time is 5-60g
When crystallization is carried out in the above manner, hydroxyapatite with a low solubility of 1fi is mainly produced according to equation (1).
This is released/crystallized on the surface of the agent, and the amount of water in the treated water becomes low.

Due to the dephosphorization process, the water cannot be recovered by backwashing, so a red activation treatment is performed next. (In the seed activation treatment, first, the dephosphorizing agent with reduced performance is brought into contact with the antiseptic bath solution, and the calcium phosphate thread crystals precipitated on the carrier coat+fm are selectively dissolved and removed.

As the hostile bath solution, one having a p) of 16 or less can be used, and an inorganic acid or an aqueous solution of 7 + j fermentation can be used. Examples of inorganic acids are salt sauce, value rW% nitric acid, carbonic acid, and fluoric acid. ! , sulfamic acid, etc., I:I (11 of blown acid)
1, acetic acid, oxalic acid, citric acid, etc. are required, but especially hydrochloric acid, sulfuric acid, nitric acid, alfamic acid, vinegar C.
Citric acid is preferred. The amount of mother-in-law 11Le differs depending on the degree of Nenjika and the degree of 1jri, but the degree of 11Le is 1 woman.

The acidic swamp treatment can be carried out not only by contacting with the crystalline bathtub, but also by any other method such as light horizontal bed water passage or immersion, but it is preferable to use a method that corresponds to the stock-cutting method. For example, if crystallization is carried out using the Kuka bed water flow method, it is easy to perform crystallization using the light bed water flow method as well. The processing time varies from a few minutes to a few hours, depending on the skill level. Semi-processing v,
Since 1 & has a small amount of t, only one special process may be performed, but it is also possible to never process the target Xm.

In the method of using phosphate rock as dephosphorization Mtl, the method of using a dense solution for the reactivation treatment is known.

However, in this method, since the chemical composition of the crystal fm (IJ stone) and the calcium phosphate precipitated on the surface of the crystal ridge are the same, depending on the processing conditions for overnight bathing, the crystalline pongee (phosphate rock) There was a danger that even Fukyu 1 would melt.

When treated under these conditions, the grain size of the granular crystals will be smaller than 9, and the weight of the box crystals will be reduced.

- In the case of the invention, since an enemy-resistant compound is used as a carrier, the problems of the above-mentioned known methods do not occur.

After the calcium phosphorus crystals on the carrier have been orally removed in this way, the dephosphorizing agent can be prepared again based on the method for preparing a dephosphorizing agent by cutting.

In the raw water, by removing the calcium layer in the bath, it is restored to its initial state. Even crystallization reaction 11
Even if one harmful substance is present, regardless of the raw water quality,
An active dephosphorizing agent is always obtained, and the carrier itself can be used at any time.

In addition, in the above treatment, the raw water may be pretreated prior to the dephosphorization operation, or the treated water may be subjected to a pretreatment process. l! '(+?), or it is also possible to use all other treatments in addition to the dephosphorization treatment, or to cool mulberry leaves, etc.

As described above, according to the present invention, it is possible to efficiently and stably produce a dephosphorizing agent with ambiguous dephosphorizing performance through simple operations, and it is also efficient even when used repeatedly. Next non-inventive examples and comparisons that could be done with dephosphorization? 1" will be explained.

Example 1 Clinobunalolite yarn with particle size of 16-32 meshes (1-α5%φ) Natural zeolite 200mg (195r)il
The mixture was placed in a t Erlenmeyer flask and washed 5 times by decantation using 500 ml of tap water each time.

Next, a sodium phosphate (NaHJ (J4) aqueous solution (pH 4a) 5
After the carrier was transferred to 00d and impregnated for one day, the reaction residual liquid and the zeolite carrier were separated.

When calculating the amount of phosphorus supported on the zeolite carrier by the above-mentioned impregnating and supporting treatment operation from the amount of decrease in phosphorus concentration in the foot fluid, 44 - P7 was obtained with one carrier. Subsequently, 12
In wt% slaked lime milk 71 (500 mt), the above carrier was added to 8
Contact treatment was carried out for 1 day. The amount of slaked lime used and the weight of supported phosphorus are approximately 15%.

3 days class y+'J! Before the treatment, the reaction residue was separated and thoroughly washed with tap water.

The arm rinsing agent prepared in this way was filled into the acrylic (acrylic) J ram between 150 and 30 mm in total inner diameter, and
Column population in synthetic water with a total alkalinity of about 100111F//-, calcium chloride water;
, t 7 (lAIBEc approx. 451'9/L, pl-1
'i & 5 to a8 were subjected to continuous coupled treatment for 25 days in an upward flow at a flow rate of 8 V 21+ r-'. However, 11E per day! If# water backwashed the metal material.

>10 Half average of phosphorus μ degree of treated water for 25 days after starting water treatment 1
id- was 1122W9/l.

Phosphorus in JJi water (180 kg/L on 25th)
Therefore, 444 live pouring treatment was performed. Total amount of natural zeolite carrier packed in the column +ii ((150
ml)' was taken out and immersed in an αIN hydrochloric acid aqueous solution (800 ml) for 80 minutes. After 80 minutes, the hydrochloric acid/acetic acid solution was separated and removed by a decantation method, and the sample was immersed again in an IIN hydrochloric acid water bath solution for 30 minutes.

Such operations were repeated once every 8 days (18 meetings). Next, 500 d of phosphate-sodium
Transfer the above CpIC carrier and ft! for 1 day! After this, the reaction IAg and the carrier were separated. Then, the carrier T was subjected to contact treatment for 8 days in 500 g of 32w1% slaked lime milk. After contact treatment for 3 days, the reaction residual liquid was separated from gold, and further washed thoroughly with tap water.

Dephosphorization agent readjusted in this way 150d Gold inner diameter 80
A dephosphorization experiment was carried out under the same conditions as above.

As a result, the average phosphorus concentration for 25 days was (112 μ/l), which was an improvement compared to the first cycle.

The above operations were carried out for one year. One year later, the average 25-day roughness was α11 k/l, which was not much different from the initial performance.

Comparison Example In Example 1, the operation was the same as in Example 1 except that the reactivation method was changed to ゛ as follows. I did it.

1. After 26 days, remove the total amount of natural zeolite carrier (150 ml) that was at the bottom of column V,
After washing with water, among the red activation treatments in Example 1 and 2, the process of contacting with yeast, that is, the process of first contacting with phosphorus bath solution and then with lime bath (It). No way! 1lf4 has been activated.

After 3 days of re-treatment, #' to the reaction was carried out in minutes h1. I washed thoroughly with Chirasuko tap water.

The dephosphorization agent obtained in this way was packed into a full-length column.1. j
The average treated water quality for 25 days was 27 g/l.

I did this cycle for one year. The average phosphorus concentration for 25 hours in the first year was 88η/L.

From Example 1 and comparative examples, it can be seen that even when the method of the present invention is used during the thorny period, the dephosphorization performance is as good as '/6. f
On the other hand, it can be seen that although relatively soft IJ recovers sufficiently at the initial stage, the dephosphorization property deteriorates to a considerable extent when used repeatedly over a long period of time.

In Example 1, the same operation as in Example 1 was carried out except that the reactivation method was changed as follows.

That is, after 25 days, the entire amount (150 mJ) of the natural zeolite carrier that had been packed in the column was taken out and placed in an LT Erlenmeyer flask. After separating and removing the B aqueous solution by the decantation method, 800 g of 11N hydrochloric acid aqueous solution was added again and immersed for 10 minutes. Such operation was repeated If! 21 times (H2S times).

Subsequently, the sample was washed 8 times by decantation using 50 h! of tap water per time.Next, it was transferred to 500 mt of an aqueous solution of 782w1% calcium chloride and subjected to a contact treatment for 5 hours.

After 5 hours, the zeolite and calcium chloride aqueous solution were separated. Subsequently, it was transferred to 500 d of phosphate-sodium aqueous M solution (pH = 48) adjusted to a phosphorus content of a000 cape/l, and after being impregnated for 1 day, the reaction residual liquid and the carrier (zeolite) were mixed.
It was separated. Next, the carrier was subjected to a contact treatment for a total of 8 days in 500ml of 12wt slaked lime emulsion. After 3 days of contact treatment, the reaction residual liquid was separated and further washed with tap water.The thus readjusted dephosphorizing agent 150- was packed into the column again and the water flow operation was started. . The average phosphorus during the subsequent 258 years was 111. The degree was u08117/l.

From this experimental example, it can be seen that when manufacturing a dephosphorization agent, the sword that exchanges lucium for the first time becomes very useful.

Therefore, it is preferable to add calcium at each reactivation treatment because the quality of the treated water will always improve.

Claims (1)

[Scope of Claims] (1) A dephosphorizing material in which calcium phosphate crystals are precipitated on the surface of an acid-resistant carrier and water containing phosphorous salts are mixed in the presence of calcium ions and at a pH of 6 or more. In the 7 method of dephosphorization in which the dephosphorization material is brought into contact with an acidic bath solution and the crystals precipitated on the surface of the carrier are removed from the bath, the calcium thread containing phosphorus is removed from the surface of the carrier. A dephosphorization method characterized by reactivating a dephosphorization material by precipitating crystals. (2) By bringing the carrier into contact with an aqueous solution containing phosphoric acid or its salt, and then with a solution containing lime,
The dephosphorization method according to claim 1, wherein calcium phosphate thread crystals are completely precipitated on the surface of the carrier. (8) After contacting the carrier with a water bath containing a calcium agent to absorb calcium, the carrier is brought into contact with an aqueous solution containing phosphorus or other salts, and then with a solution containing lime to form a surface of the carrier. The removal/method according to claim 1, which is a method for precipitating calcium phosphorus thread crystals. (4) The acid-resistant carrier is zeolite! Samurai Claims 1 J to 8 (5) The dephosphorization method according to claim 4, wherein the zeolite has an 8i/Al ratio of 8 or more.