DE2318822C2 - Process for separating metal ions from aqueous media - Google Patents

Description

The invention relates to a method for separating metal ions from aqueous media.

The pollution of sea or inland waters by heavy metal ions is an important one Environmental problem.

The object of the invention is therefore to provide an effective method for separating and recovering To ship metal ions from aqueous solutions.

The method of the invention is characterized in that the aqueous media containing metal ions with one in hydrophobic solvents brings dissolved comenic acid ester into contact.

Comenic acid ester, d. h. ^ - Oxo ^ H-pyran-S-hydroxy-2-carboxylic acid ester, are easily soluble in organic solvents. They form with those in the aqueous Solutions contain metal cations at a pH of at least 3 stable metal chelates. in the migrate the organic phase.

Specific examples of suitable 'Komensaureeslcr are lower alkyl esters, such as the propyl, butyl, isobutyl, amyl or isoamyl ester, medium or higher alkyl esters, which can have, for example 6 to 15 carbon atoms, such as the octyl, nonyl, lauryl or myristyl esters, aralkyl esters, such as the benzyl ester. and cycloalkyl esters such as the cyclohexyl ester. Some of the higher alkyl esters are particularly preferred, especially those with aliphatic C ₅ _ ₈ -Kohlenwasscrstoff-Eslerresten.

The esters mentioned form with metal ions. z. B. Fe. Cu. CD. Pb. Ni. Co. Zn. Sn, Au. Pt, Al. Sb. Bi. Cr and Y and uranium group oxides such as UO ₂ . metal chelates in water. which are easily soluble in organic solvents.

The solubility of various metal chelalc of Octyl common acid at 25 ° C. is shown in Table I.

Table;

-solutionmiltcl Benzo Chelal Fe ^{2 +} H- + Sn ^{2 +} - Co ^{2 +} 4- 4- Ni ²⁴ 4- + Cu " ¹ 4th Zn ²⁴ + + Cd ^{2 4} 4-4- Al ¹⁴ 4 4- Pb ² " - Y x ^{1 +} 4- UO ²⁴ 4- + Sb ^{2 +} 4- Bi ²¹ 4- Au ³⁴ - Pi ^{2 +} 4- Cr ^{2 +} 4-

4- 4-4- F

+
4- 4-

4-

i-

Note:

+ 4- -I- = readily soluble (1 g / l ml never less).

4- 4- = Soluble (I g / l IO ml).

4- = Slightly soluble (1 g / 10 30 ml).

- = Poorly soluble (I g, 100 KK) O ml).

toluene

4-4-4-

Xylene

4- 4 -I

4- 4

-t- 4-

4 4

4- f

.MJichloriiihiini Mc «h> li> Ui.M- | AlhUaccliH

! ketone j

+ 4- 4-4

4-

4 4

■ + ■

4- 4-.

■ -t 4 4-

4 4- 4-

4- t

+ -i

^; 4- f

τ 4-

4th 4-4 4-U-

4-

4-4-

• f

4- 4-

4th ■ F 4-

4-

4- 4-

t'lilorolorm

4- 4- -

Mr
+ 4- 4 4-

4 4- 4-4- - ¹ '

• \

4-

4- + -t-

In the process of the invention, one of the mentioned comenic acid esters is first converted into a hydrophobic one organic solvent dissolved. The organic solution is then mixed with the aqueous one, the metal ions containing solution z. B. brought into contact by shaking or stirring the two phases, at the same time by adding a base the pH of the aqueous solution is regulated to be too low Avoid pH values due to the proton dissociating during complex formation. This proton namely forms an acid together with residual anions in the aqueous solution. After all, you isolate the metal chelate from the hydrophobic organic phase.

The method of the invention is thus suitable for both the recovery of precious metals or transuranic elements from their solutions as well as to the separation of harmful heavy retals from industrial wastewater suitable. It is also used in analytical chemistry because the metal chelates formed have specific colors listed in Table II, which are colorimetrically used to determine the Metal concentration can be evaluated. The metal chelates can e.g. B. the structures I or II own

/ ° \ COOR

COOR

COOR

111)

where M is a divalent metal ion and M 'is a divalent metal ion and R is an alkyl, cycloalkyl or aralkyl radical.

To recover the metal ions themselves, those isolated from the organic phase are treated s chelate compound under cooling with a mineral acid, z. B. hydrochloric acid, whereby the comensic acid ester and the corresponding metal salt are released. Suitable organic solvents are water-immiscible solvents, e.g. B. benzene, toluene,

ίο xylene. Chloroform, 1,2-dichloroethane or trichlorethylene. The comenic acid esters are preferably used in an amount of at least 2 to 3 moles per 1 mole the metal ions used.

When performing the method according to the invention precise pH control of the aqueous solution is required. The addition of a base becomes Too strong acidification avoided, otherwise the pH value with decreasing metal ion concentration decreases in the aqueous phase. The particular permissible pH range depends on the type of together with the Metal ions from the anions present in the water. In the case of a heavy metal salt of a strong acid, like copper sulfate, can be operated at relatively low pH values (but not lower than 3) while in the case of a weak anion base, e.g. B. the acetate ion, the permissible pH limit is close to the neutral value is, but not below pH 4. When working in the more acidic pH range, no effective results are achieved Separation, since under these conditions the return

jo reaction of the reaction equilibrium is favored. In general, the pH is not below 3; the range from pH 4 to 7 is particularly preferred. In the alkaline range there is a risk that, at higher concentrations of shear metal ions, hydioxides will form deposit. The method can therefore also be carried out at higher pH values, if the concentration of ions is not too high.

The method of the invention is easy to carry out and enables the simultaneous separation of different ions present in the solution. Examples of the effectiveness of the separation of metal ions are shown in Table 11. Should it may be necessary to separate cations in a concentration lower than that given in Table 11.

repeating the procedure or combining it with other procedures is recommended.

Tables

Mctallion concentration Grain. uiecsler % Kon / ciin.ilioii η " 0.224 Alcohol test CHCI., Fe ^{2 +} 0.112 Amyl 1.35 Fe ^{2 +} 0.056 Amyl 1.35 IFc ²⁺ 0.198 Amyl 1.35 Cu ^{2 +} 0.311 Octyl Ld 7 Pb ² " 0.348 Amyl 1.35 Cd ²⁺ 0.02 Octyl 1.67 Cd ²¹ 0.02 Lauryl 1.80 Cu ^{2 +} 0.02 Lauryl 1.80 Pb ²⁺ Lauryl 1.80

Mohcr ratio
Metal / n Ustcr

concentration

in \ Vas-.ei after i degree of extraction

the treatment

98.61
98.61
98.53
99.79
99.84
97.85
97.56
98.65
95.50

3,104 10 1,111 ■ 10 0.824 10 0.915 ■ 10 0.5 ■ 10 7.5 · H) 0.488 ■ H) 0.27 10 0.90 ■ 10

The results in tables show that metal ions can be extracted effectively with a solution of comenic acid esters in organic solvents. Fe ²⁺ was quantified colorimetrically as nitroso-R-salt; see Keiji Y an o, The Kagaku no Ryoiki, special issue 3 ;, Electrophotocolorimetry (1), p.23; Nankodo. Saneo Noda, Biochemistry, vol. 29, p. 199. Other metaüionen were determined quantitatively with the aid of atomic absorption spectral analysis with the aid of an atomic absorption spectrometer type 208 from Hitachi Seisakusho. The individual metal ions correspond to the following wave-

lengths: Cu ²⁺ : 3247 A; Cd ⁺² : 2288Ä; Pb ⁺² : 283? V

The degree of extraction is calculated according to the following

Formula:

Metal ion concentration in water

". . ,, ". before treatment

Degree of extraction (%) =

Metal ion concentration in water
after treatment

Metal ion concentration in water before treatment

The examples illustrate the invention.
example 1

3.34 g of octyl comenate are dissolved in 200 ml of chloroform. In addition, 1.5475 g of copper sulfate (CuSO ₄ · H ₂ O) are dissolved in 200 ml of deionized water, so that 20 ml of this solution contain 0.0395 g of Cu ² Morten. 20 ml each of both solutions are poured together and shaken. The pH of the aqueous layer is kept at 4.0 by adding 1% strength aqueous ammonia solution. As soon as the pH value remains constant even without the addition of ammonia solution, the aqueous phase is separated off from the chloroform phase and made up to 40 ml with water. The total content of Cu ²⁺ ions is 0.0183 · 10 ~ ² g, which corresponds to a degree of extraction of 99.79%.

Example 2

1.3 g of cadmium sulfate (CdSO ₄ ) are dissolved in 200 ml of deionized water. 20 ml of this solution, which contain 0.06975 g of Cd ²⁺ -loncn, are combined with 20 ml of a solution of the octyl comenate in toluene and shaken, the ester concentration corresponding to that of Example 1. The pH of the aqueous phase is kept at 4.6. According to Example 1, a Cd ²⁺ ion content of 0.0015 g can be determined.

Example 3

1.138 g of lead acetate [Pb (CH ₃ COO) ₂ 3H ₂ O] are dissolved in 200 ml of deionized water. At the same time, 2.715 g of amyl amyl ester are dissolved in 200 ml of 1,2-dichloroethane. 200 ml of the lead salt solution containing 0.0622 g of blood ions are then combined with 20 ml of the other solution and shaken. According to Example 1, a blood ion content of 0.01 ^{× 10 2 can be} determined. which corresponds to a degree of extraction of 99.84%.

Example 4

1.11212 g of iron (II) sulfate (FeSO ₄ · 7H ₂ O) are dissolved in deionized water and made up to 100 ml. In addition, 2.175 g of amyl comensate are dissolved in 200 ml of trichlorethylene. In each case 20 ml of this solution are mixed with 5 ml (Fe ²⁺ : 0, Oi 1195 g). 10 ml (Fe ²⁺ Γ 0.02239 g) and 20 ml (Fe ^2+: 0.04478 g).! Iron (Il mixed salt solution according to Example 1 can be the following Fe ^{2 +} quantities determine:

volume

F (r * -Men «e

5 ml
10 ml
2U ml

0.1648 · 10 *
0.222 · i (T ³
0.6208 ■ 10 ³

B e i s ρ i e! 5

98.53
98.61
98.61

39.29 mg copper sulfate. 18.54 mg of cadmium sulfai and 18.31 mg of lead acetate are dissolved in deionized water and made up to 50 ml so that each metal ion is 10 mg. In addition, 900 mg of lauryl comonate are dissolved in 50 ml of chloroform. Both solutions are combined and shaken. During the shaking, the pH of the aqueous phase is kept at 3.8 by adding aqueous ammonia solution. As soon as the pH value remains constant without the addition of ammonia solution, the aqueous phase is separated from the chloroform layer and made up to 100 ml with water. The content of Cu ²⁺ ions is 0.135-10 g (degree of extraction: 98.65%). that of Cd ² "ions" 0.244 · " ³ g (degree of extraction: 97.56",. ι and that of Pb ²⁺ ions 0.45 · 10 ³ g (degree of extraction: 95.5%).

Thus, following the procedure of Examples 1 to 5, various metal ions are transferred from aqueous solution the corresponding Metallchclatc separated in organic solvents hzw. regained. the Properties of these chelals are shown in Table III. The Extraktionsgiadc achieved in each case correspond to those of Examples I to 5.

Menilldida ' Mctallion Table 111 Summation formula I ark- Fe " Sn ² ' SdiiiK'l / punkl. ( ; IC ₁₄ H ₁₁₁ Os), Dark red Hslcrrest Co- " j SnIC ₁₄ H ₁ OOi) ₂ Helluelb Octyl No. ⁴ 108 ί Co (C ₁₄ H ₁₁₁ OO ₂ Red-brown Octyl Cu ² * 118 ί Ni (C ₁₄ H ₁₁₁ O ₅ ), Yellow-brown Octyl > 245 j Cu (C ₁₄ H ₁₁₁ Os) ₂ Green yellow Octyl > 223 Octyl > 184

Resolution

Mctallchclal Esterresl Metal ion Melting point, 'C Molecular formula color Oclyi Zn ²⁴ Octyl Al ¹⁴ > 241 Zn (Q ₄ H ₁₉ O ₅ ), - Light yellow Octyl Cd ^{2 4th} 112 Al (C ₁₄ H ₁₉ Os) ₃ Light yellow Oclyl UO ₂ ' > 245 Cd (C ₁₄ H ₁₉ Os) ₂ Light yellow Octyl γΛί 179 UO ₂ (C ₁₄ H ₁₉ Os) ₂ orange methyl Al ^{3 +} > 3 (X) Y (C ₁₄ H ₁₉ Os) ₃ Light yellow methyl Ni ²⁴ 142 A1 (C ₇ H ₍₁ O ₅ ) ₃ Colorless methyl Zn ^{2 +} > 245 Ni (C ₇ H ₁₁ O ₅ J ₂ -2H ₂ O Yellow-brown Butyl Cu ²⁴ > 254 Zn (C ₇ H ₁₁ Oj) ₂ -2H ₂ O Yellow-brown Butyl Co ^{2 +} > 192 Cu (C ₁₀ H _n O ₅ ) ₂ Green yellow Isobutyl Cu ²⁴ > 3 (X) Co (C ₁₀ H _n Os) ₂ Red-brown isobutyl Co ²⁴ > 184 Cu (C ₁₀ H _n Os) ₂ Green Blue Amyl Cu ²⁴ > 300 Co (C ₁₀ H ₁₁ Os) ₂ Red-brown Amyl Co ²⁴ > 172 Cu (Q ₁ H ₁₃ Os) ₂ Green yellow hoamyl Cu ²⁴ > 278 Co (C _n H ₁₃ Os) ₂ Red-brown Isoamyl Co ²⁴ > 174 Cu (Q ₁ H ₁₃ Os) ₂ Green yellow Allyl Cu ^{2 +} > 265 Co (Q ₁ H ₁₃ Os) ₂ Red-brown Allyl Co ²⁴ > 169 Cu (QH ₇ Oj) ₂ Green yellow Cyclohexyl Cu ²⁴ > 300 Co (C ₉ H ₇ Os) ₂ Red-brown Cyclohexyl Co ^{2 +} > 227 Cu (C ₁₂ H ₁₃ Os) ₂ Green yellow Cyclohexyl Sb ^{2 +} > 260 Co (Q ₂ H ₁₃ Os) ₂ Red-brown Nonyl UO ^{2 +} 124-127 Sb (Q ₂ H ₁₃ Os) ₂ Light yellow Decyl Cu ^{7 +} 169-180 UO ₂ (Q ₅ H ₂₁ Os) ₂ orange > 193 Cu (C ₁₆ H ₂₃ Os) ₂ Green yellow

Claims (7)

Patent claims: 1. A method for separating metal ions from aqueous media, characterized in that that the aqueous media containing metal ions with an in hydrophobic Comenic acid ester dissolved in solvents. 2. The method according to claim i, characterized in that that the aqueous phase is kept at a pH of at least 3. 3. The method according to claim 2, characterized in that that the aqueous phase is kept at a pH of 4 to 7. 4. The method according to claim 1, characterized in that ions of the metals Fe, Cu, Cd, Pb, Ni, Co, Zn, Au, Pt, Al, Sb, BL Sn, Cr, Y and / or U (ie UO ₂ ) separates. 5. The method according to claim 1, characterized in that one alkyl, aralkyl and / or cycloalkyl esters the comenic acid used. 6. The method according to claim 1, characterized in that a Komensäureester with an aliphatic C ₅ _ ₈ -KohlenwasserstofTesterrest used. 7. The method according to claim 1, characterized in that benzene, toluene, xylene, chloroform, 1,2-dichloroethane and / or trichlorethylene used as a hydrophobic solvent.