DE2318822B1 - PROCESS FOR SEPARATING METALLIONS FROM AQUATIC 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 create metal ions from aqueous solutions.

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

Comenic acid ester, d. H. 4-oxo-4H-pyran-5-hydroxy-2-carboxylic acid ester, are easily soluble in organic solvents. They form with those in the aqueous Solutions containing metal cations at a pH of at least 3 stable metal chelates that are present in migrate the organic phase.

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

The esters mentioned form with metal ions, for. B. Fe, Cu, Cd, Pb, Ni, Co, Zn, Sn, Au ₅ Pt ₃ Al, Sb, Bi, Cr and Y and oxides of the uranium group, such as UO ₂ , metal chelates in water, which are easily in organic solvents are soluble.

The solubility of various metal chelates of octyl comenate at 25 ° C. is shown in Table I.

Table I. solvent benzene toluene Xylene 1,2-dichloroethane Methylethyl Ethyl acetate chloroform Chelate eon Fe ²⁺ + + + + + + + + + + + + + + + + + + + + + Sn ²⁺ - - - - + - - Co ²⁺ + + + + + + + + Ni ²⁺ + + + + + + + + + + + + + Cu ²⁺ + + + Zn ² + + + + + + + + + + + + + Cd ² + + + + + + + + + -J- + + Al ³ + + + + + + + + + ■ + + + + - + + Pb ²⁺ - - - + + + + Y ³⁺ + + + + + + + UOf ⁺ + + + + + + + + + + + + + + Sb ²⁺ + + + + + Bi ²⁺ + + + + + Au ³ + - - - + + - - Pt ² + + ₊ + - - + Cr ²⁺ + + + + + + + + + + + + +

Annotation:

+ + + = Well soluble (1 g / l ml or less).

+ + = Soluble (1 g / l-10 ml).

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

- = Poorly soluble (1 g / 100-1000 ml).

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 for the separation of harmful heavy metals from industrial suitable for sewage. 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, for example, have the structures I or II own

COOR

COOR

O> = O -> M <- O = CO

O> = 0—> M '<- O

(I)

25th

30th

35

40

COOR

(H)

where M is a divalent metal ion and M 'is

45 is trivalent metal ion and R represents an alkyl, cycloalkyl or aralkyl radical.

To recover the metal ions themselves, those isolated from the organic phase are treated Chelate compound under cooling with a mineral acid, ζ. Β. Hydrochloric acid, the comenic acid ester and the corresponding metal salt are released. Suitable organic solvents are water immiscible solvents, e.g. B. benzene, toluene, 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 carrying out the process according to the invention, precise pH control of the aqueous Solution required. Too strong acidification is avoided by adding a base, otherwise the The pH value decreases with decreasing metal ion concentration in the aqueous phase. The respectively admissible The pH range depends on the type of anions present in the water with the metal ions. In the case of a heavy metal salt, a strong acid, such as copper sulfate, can occur at relatively low pH levels be worked (but not lower than 3), while in the case of a weak anion base, e.g. B. des Acetations, the permissible pH limit is close to the neutral value, but not below pH 4. When working In the more acidic pH range, no effective separation succeeds, since under these conditions the reverse reaction the reaction equilibrium is favored. In general, the pH value is not below 3, The range from pH 4 to 7 is particularly preferred. In the alkaline range, there is a risk that Separate hydroxides at higher heavy metal ion concentrations. The procedure can therefore also can be carried out at higher pH values if the cation concentration is not too high.

The process of the invention is simple to carry out and enables simultaneous separation various ions present in the solution. Examples of the effectiveness of the separation of Metal ions are listed in Table II. Should it be necessary to use cations lower than that in To separate the concentration given in the tables, it is advisable to repeat the procedure or a combination with other methods. -

Table II

Metal ion Fe ²⁺ concentration Comenic acid ester Concentration in
CHCl ₃ Molar ratio concentration
in water after Degree of extraction Fe ² + 0.224 Alcohol residue 1.35 Metal to ester the treatment % Fe ²⁺ 0.112 Amyl 1.35 1: 3 , 3.104 · ΙΟ " ³ . 98.61 Cu ²⁺ 0.056 Amyl 1.35 1: 6 1,111-10-3 98.61 Pb ²⁺ 0.198 Amyl 1.67 1:12 0.824-10-3 98.53 Cd ² + 0.311 Qctyl 1.35 1: 2 0.915 · ΙΟ- ³ 99.79 Cd ² + 0.348 Amyl 1.67 1: 2 '0.5 · ΙΟ " ³ 99.84 Cu ²⁺ 0.02 Octyl 1.80 1: 2 97.85 Pb ²⁺ 0.02 Lauryl 1.80 1: 2 97.56 0.02 Lauryl 1.80 1: 2 '7.5 · ΙΟ " ³ · 98.65 Lauryl 1: 2 0.488-10-3 95.50 ; 0.27 · ίο- ³ ; o, 9o -ίο- ³

The results in tables show that metal ions can be extracted efficiently with a solution of comenic acid esters in organic solvents. Fe ²⁺ was quantified colorimetrically as nitroso-R-salt; see Keiji Yano, The Kagaku no Ryoiki, special issue 33, Electrophotocolorimetry (1), p.23; Nankodo, Saneo No da, Biochemistry, Vol. 29, p. 199. Other metal ions were quantitatively determined with the aid of atomic absorption spectral analysis using an atomic absorption spectrometer Type 208 from Hitachi Seisakusho. The * individual metal ions correspond to the following wavelengths: Cu ²⁺ : 3247Ä; Cd ⁺² : 2288Ä; Pb ⁺² : 2833Ä. The degree of extraction is calculated using the following formula:

Degree of extraction (%) =

Metal ion concentration in water before treatment 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⁺ ions. 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 x 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⁺ ions, 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. Then combine 200 ml of the lead salt solution containing 0.0622 g of lead ions with 20 ml of the other solution and shake it. According to Example 1, a content of lead ions of 0.01 -10 ~ ² g 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+} : 0.011195 g), 10 ml (Fe ²⁺ : 0.02239 g) and 20 ml (Fe ²⁺ : 0.04478 g) of the iron (II) - saline solution mixed. According to example 1, the following Fe ²⁺ -MeUgCn can be determined:

volume Fe ² + quantity Degree of extraction,% 5 ml 0.1648 ■ 10 ~ ³ 98.53 10 ml 0.222 -10 " ³ 98.61 20 ml 0.6208 - ΙΟ " ³ 98.61 Example 5

39.29 mg of copper sulfate, 18.54 mg of cadmium sulfate 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 ^-3 g (degree of extraction: 98.65%), that of Cd ²⁺ ions is 0.244 × 10 ^-3 g (degree of extraction: 97.56%) and that of Pb ^{2 +} Ions 0.45 x 10 ^-3 g (degree of extraction: 95.5%).

Following the procedure of Examples 1 to 5, various metal ions are transferred from aqueous solution the corresponding metal chelates separated or recovered in organic solvents. the Properties of these chelate compounds are given in Table III. The degree of extraction achieved in each case correspond to those of Examples 1 to 5.

Table III

Metal chelate Ester residue Metal ion Melting point, ⁰ C Molecular formula colour Octyl Fe ³⁺ Octyl Sn ²⁺ 108 (Q ₄ H ₁₉ O ₅ ) S. Dark red Octyl Co ²⁺ 118 Sn (Q ₄ H ₁₉ O ₅ ) ₂ Light yellow Octyl Ni ²⁺ > 245 Co (Q ₄ H ₁₉ O ₅ ) ₂ Red-brown Octyl Cu ²⁺ > 223 Ni (Q ₄ H ₁₉ O ₅ ) ₂ Yellow-brown > 184 Cu (Q ₄ H ₁₉ Os) ₂ Green yellow

Continuation,

Metal chelate Ester residue Metal ion Melting point, ° C Molecular formula colour Octyl Zn ²⁺ Octyl Al ³⁺ > 241 Zn (Q ₄ H ₁₉ O ₅ ) ₂ Light yellow Octyl Cd ²⁺ 112 Al (Q ₄ Hi ₉ Os) ₃ Light yellow Octyl uor > 245 Cd (Q ₄ H ₁₉ O ₅ ) ₂ Light yellow Octyl Y ^{3 +} 179 UO ₂ (Q ₄ Hi ₉ Os) ₂ orange methyl Al ^{3 +} > 300 Y (Q ₄ Hi ₉ Os) ₃ Light yellow methyl Ni ²⁺ 142 Al (C ₇ H ₆ Os) ₃ Colorless methyl Zn ²⁺ > 245 Ni (C ₇ H ₆ O ₅ ) ₂ • 2H ₂ O Yellow-brown Butyl Cu ²⁺ > 254 Zn (C ₇ H ₆ Os) ₂ • 2H ₂ O Yellow-brown Butyl Co ²⁺ > 192 . Cu (Q ₀ H _u O ₅ ) ₂ Green yellow Isobutyl Cu ²⁺ > 300 Co (Q ₀ HuOs) ₂ Red-brown Isobutyl Co ²⁺ > 184 Cu (Q ₀ HuOs) ₂ Green Blue Amyl Cu ²⁺ > 300 Co (Q ₀ H ₁₁ Os) ₂ Red-brown Amyl Co ²⁺ > 172 Cu (QiHi ₃ Os) ₂ Green yellow Isoamyl Cu ²⁺ > 278 Co (QiHi ₃ Os) ₂ Red-brown Isoamyl Co ^{2 +} > 174 Cu (QiHi ₃ Os) ₂ Green yellow Allyl Cu ^{2 +} > 265 Co (C _u H ₁₃ O ₅ ) ₂ Red-brown Allyl Co ²⁺ > 169 Cu (C ₉ H ₇ Os) ₂ Green yellow Cyclohexyl Cu ²⁺ > 300 Co (C ₉ H ₇ O ₅ ) ₂ Red-brown Cyclohexyl Co ²⁺ > 227 Cu (Q ₂ H ₁₃ Os) ₂ Green yellow Cyclohexyl Sb ²⁺ > 260 . Co (Q ₂ H ₁₃ O ₅ ) ₂ Red-brown Nonyl uor 124-127 Sb (Q ₂ Hi ₃ Os) ₂ Light yellow Decyl Cu ^{2 +} 169-180 UO ₂ (Q ₅ H ₂₁ Os) ₂ orange > 193 Cu (Q ₆ 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 are mixed with a comenic acid ester dissolved in hydrophobic solvents brings in touch. 2. The method according to claim 1, characterized in that the aqueous phase at a Maintains a pH of at least 3. 3. The method according to claim 2, characterized in that the aqueous phase at a Maintains pH 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, Bi, Sn, Cr ₅ Y and / or U (ie Separates UO ₂ ). 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 comenic acid ester with an aliphatic C _s _ ₈ hydrocarbon ester radical is 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.