JPH03224678A - Treatment of used acidic solution - Google Patents

Abstract

PURPOSE:To efficiently remove Fe, Cr and Ni from a used acidic soln. containing Ce, Fe, Cr, and Ni by subjecting the soln. to reduction treatment, adsorbing a free inorg. acid in the soln. on an anion exchange resin, removing the acid and electrodepositing metal ions in the soln. on the cathode. CONSTITUTION:Ce, Fe and Cr in a used acidic soln. are reduced from metal ions in a high oxidized state to metal ions in a low oxidized state and a free inorg. acid in the soln. is adsorbed on an anion exchange resin and removed. The Fe, Ni and Cr in the soln. are then electrodeposited on the cathode at below the voltage at which Ce is electrodeposited and an inorg. acid is added to the remaining Ce soln. to adjust the pH of the soln. before reuse. The anion exchange resin with the adsorbed free inorg. acid can be regenerated by passing an aq. NaOH soln. through the resin and causing the exchange reaction of the acid with OH<->. The resulting Na salt passed through the resin is dried, caked and stored. The electrodeposited metals are separated and stored.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to a method in which many kinds of metals are dissolved and these metals form metal ions in a high oxidation state having multivalent oxidation states in a solution. This invention relates to a method for treating acidic waste liquid in which metal ions in a low oxidation state are dissolved.

(Prior art) In general, acidic waste liquid in which many types of metals are dissolved is chemically stabilized by adding a reducing agent, etc., if the metals have oxidizing power, and a neutralizing agent is added to make it easier to handle. In addition, it is turned into sludge and heated and dried.

This method is simple in that there is no need to reuse the metal in the waste liquid, and the dried material after treatment can be easily handled.

As an example of using this waste liquid treatment process,
A process for treating analytical waste liquid after analyzing '+ or Cr2O7''- with an analytical indicator in which Fe'' is dissolved is known.

Concentration analysis of Ce4+ or Cr2O,'''' in an acidic solution is performed by utilizing the oxidizing power of Ce'', Cr2O,''-, and using an analytical indicator in which Fe2+, which has a lower redox potential than these metal ions, is dissolved. I can do it. Ce'
+ or Cr, 0. When an analytical indicator in which ``Fe'' is dissolved is dropped into an acidic solution in which ``-'' is dissolved, Ce' 0 becomes Ce 3
Fe2+ is oxidized to Fe'+ by the oxidizing power when Cr2O7''- changes to Cr3+ and Cr2O7''- changes to Cr3+.
Since the redox potential in the acidic solution changes rapidly when the entire amount is reduced to "+", the concentration of Ce'+ or Cr2O72- in the analysis solution can be determined from the amount of the analysis indicator dropped at this point.

On the other hand, the acidic solution after analysis must be disposed of as acidic waste liquid. The conventional treatment method for acidic waste liquid is similar to the above treatment method, in which magnesium is added to the waste liquid.

iron materials, alkali metals such as calcium, or sulfites,
Sulfite was added to completely reduce the metal ions in the acidic waste liquid, and then a neutralizing agent such as sodium hydroxide was added to form a sludge, which was then heated and dried.

(III! JII to be solved by the invention) However, the conventional method for treating acidic waste liquid has the following problems.

■ Secondary waste increases because alkaline earth metals are added as reducing agents and a neutralizing agent is added to treat the waste liquid.

■ Since a neutralizing agent is added to stabilize the acidic waste liquid, Ce, which is a rare metal and can be used as an analytical reagent, cannot be reused.

The present invention has been made to solve this problem, and in particular, it separates Fe, Ni, and Cr from acidic waste liquid in which Ce, Fe, Ni, and Cr are dissolved, and recovers and recycles rare metal and expensive Ce ions. The object of the present invention is to provide a waste liquid treatment method that can be used and can reduce secondary waste compared to conventional waste liquid treatment methods.

[Structure of the invention]

(Means for solving problem a) In the present invention, in a waste liquid treatment method for removing Fe, Ni, and Cr from an acidic waste liquid in which Ce, Fe, Ni, and Cr are dissolved, A reduction treatment step in which Ce, FO, and Cr are electrolytically reduced to reduce metal ions in a high oxidation state to metal ions in a low oxidation state, and free inorganic acids in the reduction-treated waste liquid are separated and removed using an anion exchange resin. an adsorption treatment step, an electrodeposition treatment step in which metal ions in a low oxidation state in the waste liquid that has been treated to remove free acids are electrodeposited with Fe, Ni, and Cr on the cathode at a voltage lower than the Ce electrodeposition voltage; It is characterized by adding an inorganic acid to the Ce solution and comprising a pH adjustment step for reuse.

(Function) In acidic waste liquid, Ce, Fe, Ni, and Cr are metal ions in a highly oxidized state as Ce'÷, Fe3'', Cr2O,''-
As low oxidation state metal ions, Ce3+, Fa"",
Cr” ”, dissolves in Ni2+. When hydrogen peroxide or an organic acid is added to the acidic waste liquid in which these metal ions are dissolved in the reduction treatment process, or electrolytic reduction is performed, the metal ions in a highly oxidized state are reduced to metal ions in a low oxidized state. . The added hydrogen peroxide or organic acid does not become waste because it decomposes into water while generating oxygen or carbon dioxide gas. When the reduced waste liquid is passed through an anion exchange resin in the adsorption treatment process, the free inorganic acids in the acidic waste liquid undergo an exchange reaction with the exchange groups of the anion exchange resin, and the free inorganic acids are adsorbed by the anion exchange resin, causing exchange. The groups migrate into the waste liquid and pass through the resin along with the metal ions. When the waste liquid from which free inorganic acids have been adsorbed and removed is subjected to electrolytic reduction in the electrodeposition treatment process, the pH of the waste liquid is close to neutral, so Fe2''Cr, which has a low reduction potential, is
3+ and Ni2+ are easily precipitated on the cathode and can be separated and removed from the waste liquid.

The Ce ions remaining in the waste liquid can be reused as a Ce acidic solution by adding an inorganic acid equivalent to the inorganic acid adsorbed on the anion exchange resin in the adsorption/removal step.

The anion exchange resin that has adsorbed the t1 free acid can be regenerated by causing an exchange reaction between the free acid and 01 (-) when an aqueous sodium hydroxide solution is passed therethrough.

The Na salt that has passed through the resin is dried and assimilated and stored together with the metal separated and removed in the electrodeposition process.

(Example) Hereinafter, an example of the acidic waste liquid treatment method according to the present invention will be described with reference to the drawings. The decontamination waste liquid treatment method of the present invention reduces Ce, Fe, Ni, and Cr, which are metal ions in a highly oxidized state and metal ions in a low oxidized state, dissolved in an acidic waste liquid 1, with a reduction treatment cathode made of an inert metal. A reduction treatment step 2 in which a predetermined DC voltage is applied to the treatment anode and the metal ions in a highly oxidized state are reduced to metal ions in a low oxidation state at the reduction treatment cathode, and a free inorganic acid in the reduced waste liquid is reduced. Adsorption treatment step 3 in which Fe, Cr, and Ni in the adsorbed waste liquid is adsorbed onto an anion exchange resin, and a predetermined DC voltage is applied to an electrodeposition treatment cathode made of an inert metal and an electrodeposition treatment anode. and adding an inorganic acid to the electrodeposition treatment step 4 in which the electrodeposition is deposited on the cathode for electrodeposition treatment, and the treatment solution 5 subjected to the electrodeposition treatment,
It consists of PI (p for adjustment) and I adjustment step 6. In addition, the pH-adjusted Ce acidic aqueous solution can be reused as an analytical reagent, etc.7
can do. On the other hand, when the anion exchange resin that has adsorbed the free inorganic acid in the adsorption treatment step 3 is brought into contact with an aqueous sodium hydroxide solution in the adsorbed inorganic acid desorption treatment step 8, an exchange reaction occurs between the adsorbed inorganic acid and the hydroxyl group. The hydroxyl groups are adsorbed on the anion exchange resin and can be regenerated and reused.

The Na salt generated in the desorption treatment step 8 is removed in the drying-solidification step 9.
Fe, Cr, which was reduced in volume and recovered in electrodeposition process 4,
It is stored 11 together with an electrodeposited metal 10 such as Ni.

Next, a first embodiment of the decontamination waste liquid treatment method according to the present invention will be described. Nitric acid is selected as the acidic waste liquid 1, and Ce, Fe, Cr, and Ni are dissolved in the nitric acid waste liquid.

The Ce is Ce′+ and Ce3+, the Fe is Fe′+,
Cr is dissolved in Cr, O,'' -, Ni is dissolved in Ni2+, nitric acid concentration is 2 moffi/L, Co' concentration is 0.4 mo
ff/12. Ce3+ concentration 0.4mo12#1. “Fe”
Ten concentration 0.6IloQ, Cr2o7'-concentration 0.07
3moQ/41. Ni concentration 0.065mon/12
The treatment of waste liquid will be explained.

In the reduction treatment step 2, Ce4+ and Cr2O in the waste liquid 1,
” ” to reduce. Hydrogen peroxide (H2
0□) is selected and added to the waste liquid 1, the following redox reaction occurs.

Ce” + 1/2H□O□”-Ce” +1/2H2
0+ 1/40□ ↑Cr, 072- + 3820
□: 2Cr" +3H,0+ 3/20. First, in free inorganic acid adsorption treatment step 3, when the reduced waste liquid is brought into contact with an anion exchange resin (R-OH), free nitric acid and anion exchange resin An exchange reaction occurs with the exchange group (OH-) of
Free nitric acid is adsorbed on the anion exchange resin, and OH- is hydrated with H+ in the waste liquid and transferred to the waste liquid.

R-OH+)INO3+) R-No3+ 820 The waste liquid from which free nitric acid was removed and became a neutral solution was subjected to electrodeposition treatment step 4.
Electrode area ratio (cathode/anode): 1/1 A current density of 0.0. When a DC voltage of LA/cJ is applied, the following electrodeposition reaction occurs at the electrodeposition treatment cathode, and F is removed from the waste liquid.
Electrodeposited metals such as e, Cr, and Ni are removed.

“Fe” + 2e Fe
-0,440V→ Cr” + 3e Cr
+0.74V→Ni” +2e Ni
-0,23V→ 2H÷+28. ■20.00v The metal ion electrodeposition reaction occurs in competition with the hydrogen gas generation reaction, and if the p+ of the waste liquid is low, hydrogen gas is generated preferentially than the metal ion electrodeposition reaction, and the metal is not deposited on the cathode. Does not precipitate. However, in step 3 of the free inorganic acid adsorption treatment, the pH of the waste liquid
Since it is raised to neutrality, the electrodeposition reaction of metal ions occurs easily. Further, as shown below, Ce3+ has a higher redox potential than other metal ions, so that almost no electrodeposition reaction occurs.

Ce"+ 3e Ce
-2,33V → The treatment solution 5 treated in the electrodeposition treatment step 4 is added with nitric acid equivalent to the nitric acid adsorbed in the adsorption treatment step 3 in the pH adjustment step 6, and is reused as an analytical reagent etc. as a nitric acid Ce aqueous solution7. be able to.

On the other hand, Fe, Cr, Ni electrodeposited on the cathode for electrodeposition treatment
Since the electrodeposited metal 10 such as can be easily removed from the cathode,
The cathode for electrodeposition treatment is reused in electrodeposition treatment step 4, and Fe, C
r, Electrodeposited metals such as Ni 10 are stored as waste 11
do.

In addition, when the anion exchange resin that has adsorbed NO3- in adsorption treatment step 3 is brought into contact with sodium hydroxide (NaOH) aqueous solution as a regenerant in adsorbed inorganic acid desorption treatment step 8, the following exchange reaction occurs and anion exchange resin adsorbs NO3- in adsorption treatment step 3. Ion exchange resins can be regenerated.

R-No, + Na0)l → R-OH+
NaNo.

The Na salt generated in the desorption treatment step 8 is removed in the drying/solidification step 9.
After reducing the volume, store 11.

Next, a conventional example conducted to confirm the effect of the present invention,
An example of the method for treating acidic waste liquid according to the present invention will be described by comparing the amount of waste generated when nitric acid waste liquid is discarded.

The amount of waste generated when 1000 ffi of nitric acid waste liquid having the composition shown in the above example is processed is determined.

In the treatment method according to the present invention, the hydrogen peroxide solution added in the reduction treatment step 2 can be decomposed into water and evaporated, so that the waste is the electrodeposited metal 10 such as Fe, Cr, and Ni generated in the electrodeposition treatment step 4. and Na salt generated from adsorption treatment step 3 and desorption treatment step 8. Note that the amount of Na salt generated is determined for the case of evaporation and drying.

Fe=0.6mol/12X 1100OffiX56
/mol/1000=33.6kg Cr=0.073mol/QX 2 X 11000Q
X52/mol/1.000=7.59kg N1=0.065mol/QX 1100OQX59/
mol/1000=3.84kg NaNo3= 2mol/QX 100012 X 8
5g/mol/101000=170 Total=215kg Next, calculate the amount of waste generated when conventional nitric acid waste liquid is disposed of. An iron material is added as a reducing agent to chemically stabilize Ce4+, Cr, and 0□'- in the nitric acid waste solution.

Reduction amount of Fe material required amount Ce4+ = 0.4 mol #! X 1/3=
0.133mol/12 Cr2072- reduction amount = 0.073111ol/1
2 X 2 = 0.146 mol/12 When the reduced nitric acid waste solution is neutralized with Na0II, the following compounds are generated: Ce (No, ), + 3NaOH Fe (No3)a + 3NaOHCr (No,)
, + 3NaO)I Ni(NOI)2 + 2NaOH→ Ce(OH
)3 + → Fe(OH)3 + → Cr(OH)a + → N1(O)l)2 + NaNO3 3NaN0゜NaNO3 NaNO3 When the nitric acid waste solution after neutralization is evaporated and dried, hydroxide and Na salt are Generated as waste.

Ce(OH), =0.8mol/ff1X 1o00
12X 191g/mol/10001000=1 53 (0) = (0,6+0.133+0.1
42) mol/QX 100OQ X 107g/mo
l/1000=73゜6Kg Cr(OH), =0.146mol/QX 1000
12X 103g/m+ol/1000=15.0kg N1(OH), =0.065mol/QX 1100
012X93/mol/1000=s, osicg NaN03=((0,8+0.875+0.146)X
3+(0,065X2)) mol/Qx1000j2X
85 g/mol/101000 = 475 Total = 723 kg Table 1 shows a comparison of the results of examining the amount of waste generated in accordance with the waste liquid treatment methods of the embodiment according to the present invention and the conventional example when disposing of nitric acid waste liquid. .

Table 1 As is clear from Table 1, the amount of waste generated when 1000 ff of nitric acid waste liquid is disposed of is 215 kg in the case of the example of the present invention, and the amount of waste generated when 1000 ff of nitric acid waste liquid is disposed of is 215 kg. It was confirmed that the weight would be 713 kg if discarded.

As explained above, in the first embodiment, Ce, Fe,
Hydrogen peroxide solution, which decomposes into water, is added to the nitric acid waste solution in which Cr and Ni are dissolved to chemically stabilize Ce and Cr, and Fe, Cr, and Ni can be separated from the waste solution by ion exchange and electrodeposition. Compared to conventional waste liquid treatment methods, the amount of waste generated can be reduced, and the Ce nitric acid solution can be reused. The dried waste can be assimilated into plastic, solidified with asphalt, solidified with cement, or solidified with vitrification.

In the first example, the nitric acid concentration in the nitric acid solution is 2mol
/12 instead of 0.01 to 10 mol/Q, Ce(C
e"+Ce") concentration is 0.0 instead of 0.8 mo1 #2
1-2.0mol#l, Fe concentration is 0, 6mol#l
0.01-2. instead of Q. Omol/12. The Cr concentration is 0.003 to 2.0 mo instead of 0.146 mo1/12. O
mol/R, the Ni concentration is 0.0065 Ilol, and instead of 1, 0.001 to 2.0 mol #2 can also be used. As the reducing agent added in the reduction treatment step, an organic acid such as formic acid, formaldehyde, or oxalic acid can be used instead of hydrogen peroxide solution. The current density in the electrodeposition process is 0. I
Instead of A/-, 0.01 to 2 A/d, and the cathode/anode area ratio of 100/1 to 115 can be used instead of 1/1.

In addition, instead of adding hydrogen peroxide or organic acid in the reduction treatment step 2 according to the first embodiment, a predetermined DC voltage was applied to the reduction treatment cathode and the reduction treatment anode made of an inert metal. Highly oxidized metal ions were reduced to low oxidized metal ions at the reduction cathode.

That is, the above waste liquid is subjected to reduction treatment step 2 by applying a current density of 0 and IA# between a reduction treatment cathode and a reduction treatment anode made of an inert metal with an electrode area ratio (cathode/anode) of 100/1.
When an AC voltage of d is applied, the following electrolytic reduction reaction occurs at the reduction treatment cathode.

Ce” + e Ce”
+1,61V→ Fe”+ e Fe”+
◆0,771VCr207” −+ 148÷+
6e''2Cr'+7820 +1.33V Since the reduction potential of Fe3+ is lower than the redox potential of other metal ions, the reduction reaction of Fe'0 occurs preferentially. Therefore, Ce'0 and Cr, O,"- is completely reduced by an electrolytic reduction reaction and an oxidation-reduction reaction with Fe'' described below.

Ce" + Fe"+ → Ce""+ + F
e"Cr2O7"-+14H" + 6Fe"→ 2C
r” + 6Fe” + 7)! 20 After the reduction treatment in this reduction treatment step 2, adsorption treatment step 3. When the electrodeposition treatment step 4, the PH adjustment step 6, the desorption treatment step 8, and the drying/solidification step 9 were performed according to the above first example, the effect according to the above first example was obtained. Ta.

The current density in the reduction process is 0. 0 instead of IA/ant
．． 01 to 2 A/d, and a cathode/anode area ratio of 200/1 to 1/1 can be used instead of 100/1. Further, the reduction treatment step and the electrodeposition treatment step can be used in combination instead of being installed independently.

Next, a second embodiment of the waste liquid treatment method according to the present invention will be described. In the second embodiment, sulfuric acid is selected as the acidic waste liquid 1, and Ce, Fe, Cr, and Ni are dissolved in the sulfuric acid waste liquid 1. The Ce is Ce4+ and Ce3+, and the Fe is F
e'+, Cr dissolves in Cr2O, "-, Ni dissolves in Ni", sulfuric acid concentration is 1 mol/L, Ce' concentration is 0.2
mol#t, Ce3+ concentration 0.1 mol/Q, Fe concentration 0.6 mol/n, Cr2O7''- concentration 0.073
The treatment of waste liquid with a + ol/l and Ni concentration of 0.065111 ol/12 will be described.

In the reduction treatment step 2, Ce' and Cr2O7 in the waste liquid 1 are
2- is reduced. Hydrogen peroxide solution (H20□
) is selected and added to the waste liquid, the oxidation-reduction reaction explained in the reduction treatment process of the nitric acid waste liquid occurs, and Ce'+ becomes C
At e'10, Cr2O□"- is reduced to Cr3+.

Next, in the free inorganic acid adsorption treatment step 3, when the reduced waste liquid is brought into contact with the anion exchange resin (R-OH), the free sulfuric acid and the exchange group (Oll-) of the anion exchange resin undergo an exchange reaction. However, free sulfuric acid is adsorbed on the anion exchange resin, and 0
11-: ■+ in the waste liquid is hydrated and transferred to the waste liquid.

2R-OH+ H2SO42R-SO4+ 28.
0 Free sulfuric acid has been removed and the waste liquid, which has become a neutral solution, is subjected to electrodeposition treatment step 4 with an electrodeposition treatment cathode and an electrodeposition treatment anode made of an inert metal with an electrode area ratio (cathode/anode) of 1/1. The current density is 0. When a DC voltage of IA/aJ is applied, the electrodeposition reaction described in step 4 of the electrodeposition treatment of the nitric acid waste liquid occurs at the electrodeposition treatment cathode, and Fe, Cr, and
Ni is removed.

The electrodeposited treatment solution 5 can be reused 7 as a Ce sulfuric acid aqueous solution by adding sulfuric acid in an amount equivalent to the sulfuric acid adsorbed in the adsorption step 3 in a pH adjustment step 6 as a Ce sulfuric acid aqueous solution.

On the other hand, Fe, Cr, Ni electrodeposited on the cathode for electrodeposition treatment
Since these can be easily removed from the cathode, the cathode for electrodeposition is reused in the electrodeposition process 4, and the electrodeposited metals 10, such as Fe, Cr, and Ni, are stored as waste.

In addition, when the anion exchange resin that has adsorbed SO4''- in adsorption treatment step 3 is brought into contact with sodium hydroxide (NaOH) aqueous solution as a regenerant in adsorbed inorganic acid desorption treatment step 8,
The following exchange reaction occurs and the anion exchange resin can be regenerated.

2R-So4+ 2NaO)l 4 2R-OH+
The Na salt generated in Na, So4 desorption treatment step 8 is
The volume is reduced in the drying-assimilation step 9 and stored 11.

Next, the amount of waste generated when sulfuric acid waste liquid is disposed of using the conventional example and the waste liquid treatment method of the present invention will be compared and explained in order to confirm the effects of the present invention.

The amount of waste generated when 1000ffi of sulfuric acid waste liquid having the composition shown above is treated is determined.

In the waste liquid treatment method according to the present invention, electrodeposited metals 10 such as Fe, Cr, and Ni generated in the electrodeposition treatment step 4 and Na salts generated in the adsorption treatment step 3 and the desorption treatment step 8 are also generated. Note that the amount of Na salt generated is determined for the case of evaporation and drying.

Fe = 0.6mol/QX 100012 x 5
6g/mol/1000=33.6kg Cr=0.073mol/QX 2 X 110001
2X52/mol/1000=7.59kg Ni = 0.06Ev+ol/12 X 10001
2 X 59g/mol/ 1000=: 3.84kg Na25o4: 1mol/Q
142g/mol/1000=142k.

Total = 187 kg Next, calculate the amount of waste generated when disposing of conventional sulfuric acid waste liquid. In order to chemically stabilize Ce4+ and Cr2Q, 2- in the sulfuric acid waste liquid, iron material is added as a reducing agent.

Reduction amount of Fe material required amount Ce'10 = 0.4 mol #! X 1/3=
0.133mol/12 Cr20. ”-reduction amount = 0.073 mol/4X
2=0.146mol# When the reduced sulfuric acid waste solution is neutralized with NaOH, the following compounds are generated (1/2C6, (SO4), + 3NaO)! -+Ce
(OH)3+1/2F192(SO4)3+3Na
O)l →Fe(ON)a +1/2Crz(SO4)
a + 3NaOH-+Cr(OH)a+~1so4
+ 2~aOH-* N1(0)1)2+ Na, So
.

1, 5Na2So4 1.5NaaSO4 1,5Na2So.

When the sulfuric acid waste solution after neutralization is evaporated and dried, hydroxide and Na salt are generated as waste.

Ce(Oll), =0.8+++ol/QX 100
0Rx 191g/mol/1000== 153kg Fe (OH), = (0,6+0.133+0.1
42) mol/ff X 100ORX 107g/m
ol/10(1(1=73.6Xg Cr(OH)a =Q, 146mol#tX 11
00(X 103g/mol/1000=15.0kg N1(OH), =0.065mol/12X1000
i2X93g/mol/1000:6.05kg Na, 5O4=(0,8+0.875+0.146)X
(1,5+0.065)mol/12X100fMX1
42g/mol/101000=481 Total=729kg Table 2 compares and compares the results of examining the amount of waste generated in the waste liquid treatment method when disposing of the sulfuric acid waste liquid in the example according to the present invention and the conventional example.

Table 2 As is clear from Table 2, when sulfuric acid waste liquid 100012 is disposed of, the amount of waste generated is 187 kg in the example according to the present invention, and when disposed of after neutralization in the conventional case, the amount of waste generated is 187 kg. It was confirmed that the weight was 729 kg.

As explained above, in the second embodiment, Ce, Fe, C
Hydrogen peroxide solution, which decomposes into water, is added to the sulfuric acid waste solution 1 in which r, Ni is dissolved to chemically stabilize Ce and Cr, and Fe, Cr, and Ni are converted by ion exchange and electrodeposition treatment.
can be separated. Therefore, compared to conventional waste liquid treatment methods, the amount of waste generated can be reduced, and Ce
The sulfuric acid solution can be reused.

The dried waste can be solidified into plastic, asphalt, cement, or vitrified.

In the second example, the sulfuric acid concentration in the sulfuric acid solution was 1mol
#0.01~lOmol/12.instead of l. Ce(C
e”+Ce”) concentration is 0.0 instead of 0.3 mol#t
1-1. Omol/Q, Fe concentration is 0.6mol/Q
Instead of 0.01-2.0mol/Q, Cr'lj degree is 0, 0.003-2.0m instead of 146mol/Q
ol/+! , Ni concentration is 0.0065mol/1!
It is also possible to use 0.001 to 2.0 IIlol/Q instead. As the reducing agent added in the reduction treatment step 2, an organic acid such as formic acid, formaldehyde, or oxalic acid can be used instead of hydrogen peroxide solution. The current density of electrodeposition process 4 is 0.01 to 2 A/c instead of O, lA/cd.
i, cathode/anode area ratio is 100/1~1 instead of 1/l
15 can also be used. Further, the reduction treatment step 2 and the electrodeposition treatment step 4 can be used in combination instead of being installed individually.

In addition, instead of adding hydrogen peroxide or organic acid in the reduction treatment step 2 according to the second embodiment, a predetermined DC voltage was applied to the reduction treatment cathode and the reduction treatment anode made of an inert metal. Highly oxidized metal ions were reduced to low oxidized metal ions at the reduction cathode.

That is, the above waste liquid is subjected to reduction treatment step 2 by applying a current density of 0, IA/
When an AC voltage of ci is applied, the following electrolytic reduction reaction occurs at the reduction treatment cathode.

Ce” + e Ce” +
1.61VFe” + eFe”
+0.771VCr20. "+141+"+6
e ”-2Cr3+711□O+1.33V Since the reduction potential of Fe3+ is lower than the redox potential of other metal ions, the reduction reaction of Fe:l+ occurs preferentially. Therefore, Ce4+ and Cr2O, ”- are electrolytic reduction reactions. The entire amount is reduced by an oxidation-reduction reaction between Fe2+ and Fe2+ as shown below.

Ce” 10Fe”+→Ce” + Fe”Cr,O,”
-+ 14H" + 6Fe"→ 2Cr'"
+ 6Fe'” + 78.0 After the reduction treatment in this reduction treatment step 2, the adsorption treatment step 3, the electrodeposition treatment step 4, the pH adjustment step 6, the desorption treatment step 8, and the drying/solidification step 9 are carried out in the above-mentioned second step. When processed according to the example of
Effects similar to those of the second embodiment described above were obtained. In addition,
The current density in reduction treatment step 2 is 0. 0 instead of IA/cd
．． It can also be used with a cathode/anode area ratio of 100/1 to 200/1 to 1/l.

Next, a third embodiment of the waste liquid treatment method according to the present invention will be described. In the third embodiment, hydrochloric acid is selected as the acidic waste liquid 1, and Ce, Fe, Cr, and Ni are dissolved in the hydrochloric acid waste liquid. The Ce is Ce4+ and Ce3+, and the Fe is Fe.
3+, Cr is Cr, 07"-, Ni is dissolved in Ni", hydrochloric acid concentration 2 mol/L Ce4+ concentration 0.4
mol/12. Ce3+ concentration 0.4 mol/Q, F
e' ten thick wide concentration 0+ll01/12. Cr2O,”-
Concentration 0.073mol/12, Ni concentration 0.065mol
The treatment of l# waste liquid will be explained.

In the reduction treatment step 2, Ce4+ and Cr in the waste liquid 1 are reduced to 0.
．． 2- is reduced. Hydrogen peroxide solution (■20
□) is selected and added to the waste liquid, the oxidation-reduction reaction explained in the reduction treatment step 2 of the nitric acid waste liquid occurs, and Ce4+
is reduced to Ce3+, and Cr2O,"- is reduced to Cr:I+.

Next, in the free inorganic acid adsorption treatment step 3, when the reduced waste liquid is brought into contact with the anion exchange resin (R-OH), the free hydrochloric acid and the exchange group (OH-) of the anion exchange resin undergo an exchange reaction, Free hydrochloric acid is adsorbed on the anion exchange resin, and 0■- is hydrated with 11+ in the waste liquid and transferred to the waste liquid.

R-011+ HCQ, R-CQ + H
The waste liquid from which the 20ti hydrochloric acid was removed and became a neutral solution was treated with a Denwaka Processor A4 with an electrodeposition treatment cathode and an electrodeposition treatment anode made of an inert metal with an electrode area ratio (cathode/anode) of 1/1. The current density is 0. IA/an? When a DC voltage of
r, Ni is removed.

The electrodeposited treatment solution 5 can be reused 7 as an analytical reagent or the like by adding sulfuric acid in an amount equivalent to the hydrochloric acid adsorbed in the adsorption treatment step 3 in a pH adjustment step 6 to form a Ce hydrochloric acid aqueous solution.

On the other hand, Fe, Cr, Ni electrodeposited on the cathode for electrodeposition treatment
Since these can be easily removed from the cathode, the cathode for electrodeposition is reused in the electrodeposition process 4, and Fe, Cr, and Ni are stored as waste.

In addition, when the anion exchange resin that has adsorbed CQ- in the adsorption treatment step 4 is brought into contact with an aqueous solution of helium hydroxide (NaO+1) as a regenerant in the adsorbed inorganic acid desorption treatment step 8, the following exchange reaction occurs: Anion exchange resins can be regenerated.

R-CQ + NaOH-+ R-Off +
Na salt generated in NaCQ desorption treatment step 8 is dried.
The volume is reduced in the solidification step 9 and stored 11.

Next, a description will be given of a conventional example conducted to confirm the effects of the present invention and a waste liquid treatment method according to the present invention, comparing the amount of waste generated when hydrochloric acid waste liquid is discarded.

The amount of waste generated when 100,012 hydrochloric acid waste liquids having the composition described above are treated is determined.

In the waste liquid treatment method according to the present invention, the electrodeposited metals 10 such as Fe, Cr, and Ni are generated in the electrodeposition treatment step 4 and the Na salts generated in the adsorption treatment step 3 and the desorption treatment step 8. Note that the amount of Na salt generated is determined for the case of evaporation and drying.

Fe=0.6mol/RX 1100OQX56/mo
l/1000=33.6kg Cr=0.073mol/12X 2 X 11000
1X52/mol/1000nia, 59kg N1=0.065mol/12X 1100OI2X5
9/mol/1000=3.84kg NaC+! =2mol/RX 1100OI2X58/
mol/1000 = 116 kg Total = 161 kg Next, calculate the amount of waste generated when disposing of conventional hydrochloric acid waste liquid. An iron material is added as a reducing agent to chemically stabilize Ce4÷ and Cr2O, "- in the hydrochloric acid waste solution.

Reduction amount of Fe material required amount Ce'0 = 0.4 mol/12 X 1/3
=0.133mol/12 Amount of reduction of Cr20.2-=0.073n+ol/RX
2 = 0.14611ol/Q When the reduced hydrochloric acid waste solution is neutralized with NaO)1, the following compounds are generated eCQ3 FeC et rCQ3 NiCf2゜+ 3NaOH→Ce(OH)3 + 3NaO)I - * Fe( OH).

+3NaOH4Cr(OH),.

+ 2NaOH→Ni(OH)2 + 3NaCQ + 3Na(4 + 3NaCj! + 2NaCR When the hydrochloric acid waste solution after neutralization is evaporated and dried, hydroxide and Na salt are generated as waste.

Ce(OH)3=0.8mol/12X 1oooQx
191g/mol/10001000=1 53 (OH), = (0,6+0.133+0.1
42) mol/12 X 1oooQX 107g/m
ol/1000=73.6Kg Cr(Off)a=0.146mol/ffX 1o
ooQx 103g/mol/1000=15.0kg N1(011)2=0.065mol/12X1000
i1X93g/mol/1000=6.05kg NaCR=((0,8+0.875+O,146)X3
+(0,065X2))mol/QX1000QX 5
8 g/mol/ 101000 = 324 Total = 572 kg Table 3 shows a comparison of the results of examining the amount of waste generated according to the waste liquid treatment method when disposing of hydrochloric acid waste liquid in the example according to the present invention and the conventional example. .

Table 3 As is clear from Table 3, when 1000Q of hydrochloric acid waste liquid is disposed of, the amount of waste generated is 161 kg in the case of the example of the present invention, and the amount of waste generated after addition of a reducing agent and neutralization treatment in the conventional example. It was confirmed that the weight would be 571 kg if the weight was 571 kg.

As explained above, in the third embodiment, Ce, Fe,
Hydrogen peroxide solution, which decomposes into water, is added to the hydrochloric acid waste solution in which Cr and Ni are dissolved to chemically stabilize Ce and Cr, and then Fe, Cr, and N are converted by ion exchange and electrodeposition treatment.
i can be separated. Therefore, the amount of waste generated can be reduced compared to conventional waste liquid treatment methods, and
The Ce hydrochloric acid solution can be reused. The dried waste can be solidified into plastic, asphalt, cement 1, or vitrified.

In the third example, the concentration of hydrochloric acid in the hydrochloric acid waste liquid is 2mol
/R instead of 0.01 to 10 mol/ff, Ce(C
e”+Ce”) concentration is O, instead of 0.8mol1/12.
O1-2. Omol/R, Fe concentration is 0.6mol/1
! 0.01 to 3.0 mol/12. The Cr concentration is 0.003 to 2.0 instead of 146 mo1 #2. Om
ol/12. Ni concentration of 0.001 to 2.0 mol/Q can be used instead of 0.0065 mol/Q. As the reducing agent added in the reduction treatment step 2, an organic acid such as formic acid, formaldehyde, or oxalic acid can be used instead of hydrogen peroxide solution. It is also possible to use an IT current density of 0.01 to 2 A/cd instead of 0°IA/ffl in electrodeposition process 4, and a cathode/anode area ratio of 100/] to 115 instead of 1/1.

In addition, in accordance with the third embodiment, instead of adding hydrogen peroxide or organic acid in the reduction treatment step 2, a predetermined DC voltage was applied to the reduction treatment cathode and the reduction treatment anode made of an inert metal. The highly oxidized metal ions were reduced to the low oxidized metal ions using the reduction cathode.

That is, the above waste liquid is subjected to reduction treatment step 2 by applying a current density of 0, IA/
When an AC voltage of cJ is applied, the following electrolytic reduction reaction occurs in the reduction processing lI three electrodes.

Ce"+e"Ce" +1.6+, VFe
" + e "Fe" +
0.771VCr20. ” ”-+ 14P +6e
2Cr3+7H□O+1. ．． Since the reduction potential of 33VFe3+ is lower than the redox potential of other metal ions, the reduction reaction of Fe3+ occurs preferentially. Therefore, Ce'+ and Cr2O, "- are completely reduced by an electrolytic reduction reaction and an oxidation-reduction reaction with Fe2+ described below.

Ce” + Fe” −* Ce” +
Fe”Cr2O7” + 148” + 6F
e”→ 2Cr3÷ + 6Fe” + 7)1.
0 After the reduction treatment in this reduction treatment step 2, adsorption treatment step 3, electrodeposition treatment step 4, PH adjustment step 6, desorption treatment step 8, and drying/solidification step 9 are performed according to the above third embodiment. As a result, effects similar to those of the third embodiment described above were obtained. The current density in the reduction process is 0. IA/cnY
0.01~2A/ad instead of , cathode/anode area ratio is 1
Instead of 00/1, 200/1 to 1/1 can also be used.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(υ Since Fe, Cr, and Ni can be removed by electrodeposition from an acidic waste solution in which Ce, Fe, Cr, and Ni are dissolved, it is possible to reuse Ce, which is a rare metal and is expensive.

(2) Stabilize Ce and Cr by adding reducing agents such as hydrogen peroxide and organic acids that decompose into water or electrolytically reduce them, and remove Fe, C and Ni from the acidic waste liquid by ion exchange and electrodeposition. can. Therefore, compared to a method in which acidic waste liquid is stabilized by adding a reducing agent such as an alkaline earth metal and further adding a neutralizing agent, the amount of waste generated can be reduced.

[Brief explanation of drawings]

The figure is a block flow showing the waste liquid treatment method according to the present invention. 1... Waste liquid, 2... Reduction treatment process, 3
...Adsorption treatment process, 4...Electrodeposition treatment process, 5...
Treatment solution, 6.pt+adjustment step, 7...
Reuse, 8...Desorption treatment process, 9...Drying/solidification process, 10...Electrodeposited metal, 11...Storage. (8733) Agent: Yoshiaki Inomata, patent attorney (and 1 others)
given name)

Claims (1)

[Claims] (1) Cerium (Ce), iron (Fe), nickel (Ni)
), Fe, Ni from acidic waste liquid containing dissolved chromium (Cr)
, a method for treating acidic waste liquid for removing Cr, a reduction treatment step of reducing the Ce, Fe, and Cr having multivalent oxidation states in the waste liquid from metal ions in a high oxidation state to metal ions in a low oxidation state; An adsorption/removal process in which free inorganic acids in the reduced waste liquid are separated and removed using an anion exchange resin, and a desorption process in which the inorganic acids adsorbed to the anion exchange resin are desorbed using a regenerating agent to regenerate the anion exchange resin. a drying and solidifying step of drying and solidifying the desorbed inorganic acid; and a step of drying and solidifying the desorbed inorganic acid, and applying metal ions in a low oxidation state in the waste liquid from which the free acid has been removed to a cathode of Fe, Ni, and Cr at a voltage lower than the Ce electrodeposition voltage. A method for treating acidic waste liquid, comprising an electrodeposition treatment step for electrodeposition, and a pH adjustment step for adding an inorganic acid to the Ce solution after the electrodeposition treatment for reuse.