RU2247166C2 - Selective recovery of molybdenum(vi) - Google Patents

Abstract

FIELD: hydrometallurgy.

SUBSTANCE: invention relates to sorption-mediated recovery of molybdenum from solutions containing heavy metal cations. Method of invention comprises providing solution to be treated, sorption of molybdenum(VI) on anionite at pH < 7. Sorption is conducted from solutions with anionites AM-2b and AMP at solution pH below pH of hydrolytic precipitation of heavy metal cations but higher than pH of formation of molybdenum cations (pH ~ 1).

EFFECT: increased process selectivity and reduced number of stages in preparation of pure molybdenum.

9 dwg, 3 tbl, 4 ex

Description

The method of selective extraction of molybdenum (VI) from solutions of heavy metal cations relates to the field of extraction of substances using sorbents and can be used in non-ferrous and ferrous metallurgy, as well as for the treatment of industrial and domestic wastes and for the processing of non-ferrous metal wastes containing molybdenum (VI) .

It is known that molybdenum in the form of trisulfide can be isolated from aqueous solutions [Voldman G.M., Zelikman A.N. The theory of hydrometallurgical processes, M.: Metallurgy. - 1993. S.307-311].

The disadvantage of this method is that, along with molybdenum trisulfide, sulfides of other metals precipitate. The method of precipitation of molybdenum trisulfide from sodium tungstate solutions used in practice does not provide high selectivity of the process, since up to 0.2-0.3% of tungsten is precipitated together with molybdenum. In addition, precipitation from acidic solutions leads to the release of hydrogen sulfide.

A known method of extracting molybdenum (VI) from solutions containing heavy metal cations, including preparing a solution, sorption of molybdenum (VI) on anion exchange resin at pH <7 [SU 1777369 A1, IPC C 22 V 34/34, publ. 05/20/1996].

The disadvantage of this method is that the sorption of anion exchangers AM-2b and AMP has not been studied, which could provide high selectivity for the extraction of molybdenum (VI) from solutions containing heavy metal cations.

The problem to which the claimed invention is directed is to find an effective method for the selective extraction of molybdenum (VI) from an aqueous solution of heavy metal cations.

The technical result that can be achieved by carrying out the invention is the high selectivity of extracting molybdenum (VI) ions from solutions of heavy metal cations, while at the same time simplifying and shortening the steps for producing pure molybdenum and its compounds.

This technical result is achieved by the fact that in the method of extracting molybdenum (VI) from solutions of heavy metal cations, including preparing the solution, sorption of molybdenum (VI) on anion exchange resin at pH <7, sorption is carried out from solutions by anion exchangers AM-2b and AMP at a solution pH value lower pH value of hydrolytic precipitation of heavy metal cations and higher pH value of the formation of molybdenum cations (pH ~ 1).

The essence of the method is illustrated by drawings, where Figures 1-8 show the dependences of the residual concentration of molybdenum (VI) on the pH value, sorption time, and sorbent pretreatment method, and Fig. 9 shows a variant of the process flow diagram for processing the initial solution, and the data in tables 1 -3, where the residual concentration of heavy metal cations is given, as well as the degree of their extraction from the solution.

Sorption of Mo (VI) was carried out from 200 cm ^{3 of the} initial solution of Na ₂ MoO ₄ , the mass of the sorbent was 2 g. Macroporous anion exchange grade AM-2b containing exchange groups —CH ₂ —N (CH ₃ ) ₂ , —CH ₂ —N (CH ₃ ) ₃ ,

as well as AMP gel anion exchange resin containing exchange groups

during the day kept in distilled water (graphs 1 - Fig.1-3, 5, 7-8), or 0.1 N. NaOH solution (graphs 2 - figures 1-3, 5, 7-8), or 0.1 n. Hcl solution (graphs 3 of Figs. 1-2, 7-8 and Figs. 4-6).

The concentration of molybdenum ions was determined using a KFK-3 photocolorimeter; the acid-base characteristics of the solution were controlled by a pH-121 brand pH meter.

In the process of sorption, the pH of the solution changed; therefore, in the process of sorption, the setpoint pH was corrected with continuous stirring.

Stirring and maintaining the desired pH value was carried out until in the future, the acid-base characteristics of the system changed slightly. However, for a greater guarantee of achieving equilibrium, the contact of the sorbent and the solution was carried out for at least a day. To maintain a given pH value of the solution during sorption, NaOH or HCl solutions were used as neutralizers. The set pH value was maintained for 5 hours from the start of sorption by neutralization of the solution; subsequently, the pH value changed insignificantly; therefore, the pH value was adjusted once a day.

Sorption was carried out at room temperature.

Using the values of the concentration of molybdenum ions in the initial aqueous solution and after sorption, the SOE, mg / g was calculated.

Examples of specific performance of the method.

Example 1 (Fig.1-2, table 1)

The initial solution contained, g / dm ³ : 12.8 Co (II), 6.5 Mo (VI).

Sorbent AM-2b.

Figure 1-2 shows the results of the extraction of molybdenum (VI) from a solution of CoCl _{2 by} sorption at pH 2.5 (figure 1) and 4.0 (figure ₂ ).

The best indicators of extraction after two days of sorption were obtained at pH 2.5 and aqueous treatment of the sorbent (СОЕ = 530 mg / g, 81.5% recovery).

Table 1 shows the recovery of Co (II) in solution after three days of contact of the solution and the sorbent.

Table 1 Sorbent pretreatment The concentration of Co (II), g / DM ³ Recovery, wt.% From the original source residual pH 2.5 H ₂ O
NaOH
Hcl 12.75
12.75
12.75 12.70
11.65
11.47 0.4
8.6
10.0 pH 4.0 H ₂ O
NaOH
Hcl 12.75
12.75
12.75 12.70
12.70
11.65 0.4
0.4
8.6

Example 2 (Figs. 3-6, Table 2)

The initial solution contained, g / dm ³ : 12.1-13.6 Ni (II), 0.85 and 6.6 Mo (VI).

Sorbent AM-2b.

Figure 3-6 shows the results of the extraction of molybdenum (VI) from a solution of NiCl _{2 by} sorption at pH 2.5 (Fig.3-4) and 4.0 (Fig.5-6).

The best recovery rates after two days of sorption were obtained at pH 4 and acid treatment of the sorbent (СОЕ = 494 mg / g, 74.4% recovery).

Table 2 shows the extraction of Ni (II) in solution after four days of contact of the solution and the sorbent.

table 2 Sorbent pretreatment The concentration of Ni (II), g / DM ³ Recovery, wt.% From the original source residual pH 2.5 H ₂ O
NaOH
Hcl 12.06
12.06
13.60 11.96
10.46
13.52 0.8
8.6
12.1 pH 4.0 H ₂ O
NaOH
Hcl 13.60
13.60
12.86 13.55
13.39
11.81 0.4
1,5
8.2

Example 3 (Figs. 7-8, Table 3)

The initial solution contained, g / dm ³ : 15.6-16.0 Mn (II) and 6.6 Mo (VI).

Sorbent AM-2b.

7-8 show the results of the extraction of molybdenum (VI) from a solution of MnCl _{2 by} sorption at pH 2.8 (Fig.7) and 4.0 (Fig.8).

The best indicators of extraction after 2 days of sorption were obtained at pH 4 and aqueous treatment of the sorbent (SOE = 499 mg / g, recovery of 97.5%).

Table 3 shows the extraction of Mn (II) in solution after four days of contact of the solution and the sorbent.

Table 3 Sorbent pretreatment The concentration of Mn (II), g / DM ³ Recovery, wt.% From the original source residual pH 2.8 H ₂ O
NaOH
Hcl 15.60
15.60
15.60 15,55
11.20
12.40 0.6
28,2
26.9 pH 4.0 H ₂ O
NaOH
Hcl 16.00
16.00
14.47 14.40
12.40
12.21 10.0
22.5
15.6

Example 4

The initial solution contained, g / dm ³ : 12.75 Ni (II) and 6.6 Mo (VI).

Sorbent AMP

After a day of sorption during acid treatment of the sorbent, the following results were obtained:

Sorption time, h The residual concentration of Mo (VI), g / DM ³ , SOYE, mg / g 24 4.8 184

After sorption of Mo (VI), Me (II) cations (Me = Co, Ni, Mn) can be separated from the solution by sorption, hydrolytic precipitation, electrolysis, and other methods.

Figure 9 shows a variant of the basic technological scheme of processing the initial solution.

Compared with the prototype, the proposed method provides high selectivity for the extraction of molybdenum (VI) ions from solutions of heavy metal cations, while simplicity and reduction of the stages of obtaining pure molybdenum and its compounds.

Claims (1)

A method of extracting molybdenum (VI) from solutions containing heavy metal cations, including preparation of the solution, sorption of molybdenum (VI) on anion exchange resin at pH <7, characterized in that the sorption is carried out from solutions by anion exchangers AM-2b and AMP at a pH of less than The pH of the hydrolytic precipitation of heavy metal cations is greater than the pH of the formation of molybdenum cations (pH ~ 1).

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