JPS627491A - Removal of phosphorus in waste liquid - Google Patents

Abstract

PURPOSE:To efficiently remove phosphorus, by containing sodium hypochlorite and an alkali metal ion in a waste liquid containing oxyacid of phosphorus to perform heat treatment and subsequently adding calcium hydroxide to the waste liquid. CONSTITUTION:Sodium hypochlorite is added to a waste liquid containing oxyacid of phosphorus and an alkali metal ion such as Na or K is further contained in the waste liquid and heat treatment is applied to the waste liquid at 70 deg.C or more. Next, calcium hydroxide is added to sediment oxyacid of phosphorus as calcium phosphate while the precipitate is removed by a usual method. By this method, the removal efficiency of phosphorus can be markedly enhanced.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a waste liquid containing oxyacids such as phosphoric acid, pyrophosphoric acid, phosphorous acid and 9-hypophosphorous acid. Regarding how to remove.

<Prior Art> Phosphorus in various industrial waste liquids needs to be removed for environmental conservation of rivers and lakes, or for reuse of the waste liquids. By the way, phosphoric acid and pyrophosphoric acid react with slaked lime, and the phosphoric acid power is 1. By producing an insoluble calcium salt such as calcium pyrophosphate, flocculation and sedimentation separation is possible, and there is no technical difficulty in its removal.

On the other hand, in recent chemical plating processes, the electroless plating solution sometimes contains large amounts of phosphite ions and hypophosphite ions as reducing agents, and as the solution ages, It is replaced at regular intervals. In this foaming waste liquid, the total amount of phosphorus is 10,000 to 70,000.
00 P p m is included.

By the way, phosphite ions and hypophosphite ions in this liquid cannot be removed by the above-mentioned means.

This conventional removal method includes the following methods.

(Hydrogen peroxide method) First, add the same amount of hydrogen peroxide to the waste liquid, then add sodium hydroxide until the pH becomes 7.5 to 8.0, and stir for 1 hour to cause an exothermic reaction. Add calcium oxide to p) 19.5. Furthermore, 10 pps+ of polymer flocculant is added.

■ Sodium hypochlorite method First, add the same amount of sodium hypochlorite to the waste liquid, add sodium hydroxide until the pH becomes 11.0, and stir for 1 hour to cause the primary reaction.0 Next, add sulfuric acid to pH 8. , 8, and then add calcium hydroxide to pH 9.5.
Add until. Furthermore, 10 ppm of a polymer flocculant is added.

In each of the above examples, a portion of the required amount of calcium hydroxide may be replaced with calcium chloride.

<Problems to be Solved by the Invention> Incidentally, each of the above-mentioned methods does not actually have a high removal rate and cannot necessarily be said to be an effective method.

Incidentally, using a solution containing a total of 20,000 ppm of phosphorus, the phosphorus was removed using each of the above methods, and the supernatant water was filtered through a filter paper. Then, e, tooppm is added to the supernatant water.
of phosphorus was contained, and the phosphorus removal rate was 59.5%. Furthermore, in the sodium hypochlorite method, the supernatant water contained 11,000 ppm of phosphorus, and the phosphorus removal rate was 45%.

As described above, it was confirmed that the phosphorus removal rate of each of the above methods was around 50%, and that it was not possible to achieve a favorable J& result.

In particular, the present invention aims to provide a method for removing phosphoric acid that can effectively remove phosphite ions and hypophosphite ions.

Means for Solving the Problems> The present invention involves adding sodium hypochlorite to a waste liquid containing phosphorous oxygen acid, further adding alkali metal ions to the waste liquid, and then subjecting the waste liquid to a heat treatment at 70°C or higher. It is obtained by first adding calcium hydroxide and precipitating it as calcium phosphate, and is characterized by being subjected to heat treatment during the necessary steps of the reaction process as described above.

Effect〉 According to the above method, the reaction proceeds based on the following chemical formula.

■) Reaction of phosphite ion PCt+ (-order reaction) M3 Poor + NaC10-” M3PO4+
Mail (secondary reaction) 2 M3PO4+ 3 Ca(OH) 2 →Ca3(
PO4) 2 + 6 MOI42) Hypophosphite ion P
o2 reaction (-order reaction) M3po2 + 2 NaC10→M, lPO4+ 2
Mail (secondary reaction) 2 M3PO4+ 3 Ca(OH)z = Ca3(P
O4)2 + 6 Mol Here, X represents an alkali metal ion such as Ha, etc.

Thus, in the above method, calcium phosphate (Ca3(PO4)2) is finally generated, and this inorganic substance is insoluble in water and therefore precipitates in the liquid.
Recovery can be easily done.

By the way, when the above-mentioned secondary reaction was carried out at high temperature, the reaction efficiency was increased and the phosphorus removal rate was dramatically improved.

Note that phosphoric acid and birophosphoric acid in the liquid become calcium salts and easily precipitate by adding calcium hydroxide.

Test example> 1 ■ Phosphate ion, hypophosphite ion, the sum of i
The present invention was carried out according to the following procedure using a chemical nickel plating waste solution containing ooppm as a sample.

b) Sodium hypochlorite (Na
Add 55 cc of Cl0 ) and NaOH. Said Na
Add OH until the pH of the solution reaches 11.

The liquid is heated at various temperatures as described below.

mouth) Next, calcium hydroxide (Ca(OH):+ ),
Add 15,000 ppm of calcium chloride. The above amount of hydroxidizing power sium (Ca(OH)+) (1) is added until the pH of the liquid becomes 10.5.

Here, the reason for adding 15,000 ppm of calcium chloride will be described. That is, if too much calcium hydroxide is applied, calcium hydroxide that is not involved in the reaction remains as sludge, which requires recovery, which is rather troublesome. On the other hand, in the waste liquid treatment number ζ, it is impossible to add the optimum amount of calcium hydroxide. Therefore, it was decided to reduce the amount of calcium hydroxide and compensate for the lack of Ca with calcium chloride. In addition, according to the calcium chloride alone, it is weakly acidic, so it is difficult to obtain a rapid chemical reaction, and it cannot be used as a Y agent.

c) Add 10 ppm of polymer flocculant.

The polymer flocculant flocculates precipitated calcium phosphate to facilitate its collection.

2) Pour the supernatant liquid onto filter paper! pass

By analyzing the amount of phosphorus in this filtrate, it is possible to detect the amount of phosphorus remaining in the liquid without precipitating.

Next, each of the above chemical reaction formulas is shown in F below.

(-Next reaction) Na3PO3+ Mail0 →Na3PO4+ Na
CINaBPO2+ 2 NaCl0 ”NaBPO4
+ 2 Mail (secondary reaction) 2 Na3PO4+ 3 (:a(OH) 2 +ca
3cpo4) 2 + 6 NaOH2Na3PO4+
30aC12→Ca,, (PO4)z + 68aC
1. Test results〉 The ratio of the total content of sulfite ions and hypophosphite ions in the waste liquid before treatment to the phosphorus content of the L clear liquid collected using the filter paper described above was determined as the phosphorus removal rate. As a result, the relationship with the liquid temperature during the next reaction was determined as shown in the 5th table.

Incidentally, the heating waiting period was 30 minutes in each case. However, in the wired state (100°C), the time was set to 1 to 2 minutes.

The J4 body stroke values are shown below.

As is clear from the table, when heated at 80 DEG C. or higher, the next reaction was carried out very quickly, and the removal rate was approximately 100%, indicating that most of the reaction was possible. It has also been found that temperatures above 70°C are better than conventional methods.

<Effects of the Invention> The present invention is capable of significantly increasing the removal rate of 1-non by adding a simple step of heat treatment during the reaction step, as described above. It has excellent effects that make it ideal for waste liquid treatment.

Claims (1)

[Claims] After adding sodium hypochlorite to the waste liquid containing phosphorus oxygen acid and further containing alkali metal ions,
A method for removing phosphorus from a waste liquid that is heat treated at a temperature of ℃ or above, then adds calcium hydroxide to precipitate it as calcium phosphate.