JPH0770665A - Separation of rhenium and impurity - Google Patents

Abstract

PURPOSE:To remove the anionic impurities of selenium, molybdenum and arsenic which behave in a similar manner to rhenium and are hardly separated from rhenium by anion exchange from a rhenxum-contg. soln. CONSTITUTION:An aq. soln. contg. >=1 element among selenium, molybdenum and arsenic and rhenium is oxidized by an oxidizing agent such as hydrogen peroxide and hypochlorites, a calcium compd., strontium compd. and barium compd. soluble in water are added, and the elements other than rhenium are separated as the precipitate at <=pH10. In this case, the calcium compd. is initially added, the formed precipite is separated, and then the barium compd. is added.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering rhenium from a rhenium-containing solution obtained from a smelting process of copper or molybdenum ore or a waste catalyst.

[0002]

2. Description of the Related Art As a method of relatively selectively recovering rhenium from an exhaust gas cleaning liquid generated in a copper smelting process or a leachate of a rhenium-containing catalyst, a method of adsorbing it onto an anion exchange resin is known. However, selenium, molybdenum, and arsenic, which easily form anions, are adsorbed to some extent. It is difficult to completely separate these elements even if the ion exchange resin is washed with sodium hydroxide as disclosed in JP-A-60-131828. Therefore, these elements are always mixed in the eluent.
Moreover, about 10% of rhenium was lost in the cleaning liquid due to the cleaning operation of the ion exchange resin.

Further, as shown in JP-A-60-131829 or JP-A-62-123020, the pH at which molybdenum, arsenic and selenium precipitate even when an element other than rhenium is separated from the eluent by sulfurization. Under the conditions, most of rhenium also co-precipitated and could not be separated.

Further, when the poorly soluble perrhenate to be the product is crystallized from the eluent by concentration, coexisting anionic impurities alone do not precipitate even if the pH is raised.
Most of these are distributed in the mother liquor (eluent), and are disclosed in JP-A-62-
As shown in 119115, there are limited cases where anionic impurities can be separated by elutriation as a precipitate. Therefore, when the operation of concentrating the mother liquor and recovering the crystals of perrhenate was repeated, the anionic impurities were concentrated in the liquid, and finally rhenium remained in the liquid considerably. However, the high-purity perrhenate used as a product cannot be recovered.

In particular, selenium has a behavior similar to that of rhenium, co-adsorbs in the anion exchange step, and even when sulfur dioxide, which is said to be capable of selectively reducing selenium, is used to precipitate and mutually separate. I couldn't do that.

[0006]

The object of the present invention is to eliminate impurities such as selenium, arsenic, and molybdenum, which are difficult to separate and remove from rhenium by anion exchange method or selective sulfurization method, to completely eliminate impurities. And to provide a method for selective separation.

[0007]

According to the present invention, an aqueous solution containing at least one element selected from selenium, molybdenum and arsenic and rhenium is oxidized by an oxidizing agent such as hydrogen peroxide or hypochlorite. Later, a water-soluble calcium compound,
Add strontium compound and barium compound, pH
A method for separating rhenium and impurities is characterized in that an element other than rhenium is separated as a precipitate at a ratio of 10 or less. In the present invention, preferably, after the oxidation treatment, the calcium compound is added first, the precipitate formed is separated, and then the barium compound is added.

[0008]

Next, the present invention will be described in detail.

The reaction in the oxidation treatment is as follows.

[0010] ^{_{2ReO 3 2- + 3 (O)}} + 2H + → 2ReO 4 - + H 2 O (1) SeO 3 2- + (O) → SeO 4 2- (2) AsO 2 - + (O) + H ₂ O → AsO ₄ ^3- + 2H ⁺ (3)

It should be noted that molybdenum contains M
It exists in the form of oO ₄ ^2- .

[0012] In the present invention, perrhenate ion ReO ₄ ^-
Calcium salt, strontium salt, and barium salt of selenium ion SeO ₄ ²⁻ , arsenate ion AsO ₄ ³⁻ , molybdate ion MoO ₄ ²⁻ of calcium salt, strontium salt, and barium salt are all soluble in water. Also utilizes the phenomenon of being poorly soluble.

Among the anionic impurities that are likely to coexist with rhenium, molybdenum tends to have the highest valence of 6 unless complexed, but rhenium, selenium, and arsenic usually have various valences in an aqueous solution. Is taking. The anions of rhenium, selenium, and arsenic have different salt solubilities depending on the valence of the central element. For example, in the state of rhenium ion ReO ₃ ²⁻ , rhenium is a poorly soluble salt of the alkaline earth metal. On the contrary, selenium is soluble in a similar salt in the state of selenite ion SeO ₃ ²⁻ , and therefore, even if the alkaline earth metal ion is allowed to act on these mixtures as they are, mutual separation is extremely incomplete. . Therefore, it is necessary to act on an oxidizing agent to change the ions into mutually separable ions as shown in the equations (1) to (3).

As the oxidizing agent to be used, any compound can be used as long as it can oxidize all rhenite ions and coexisting impurity ions to the maximum valence. For example, hypochlorites, hydrogen peroxide and the like are suitable as compounds that can be obtained industrially in large quantities at low cost, with few by-products and residuals of heavy metals and COD sources that are problems during drainage. However, even if the oxidant satisfies the above conditions, an oxidant such as peroxodisulfate, which produces a sulfate ion as a by-product after the reaction, consumes the alkaline earth metal ion in a subsequent step and precipitates containing impurities. It is not preferable because it increases the amount. Further, when the liquid contains ammonium ions, the use of hypochlorites increases the consumption amount because the oxidizing agent is consumed for oxidizing the ammonium salt.

If the redox potential is measured, the end point of the oxidation reaction can be judged by the sudden rise in the potential.
The actual potential depends on the pH and type of oxidant,
For example, in the case of sodium hypochlorite, at pH 1, it shows a potential of about 480 to 510 mV against the silver-silver chloride electrode during the reaction, but it rapidly rises to 900 mV or more near the end point, and this potential should be stable. If it is the end point. When the coexisting rhenium coexists as a brown rhenite ion, it becomes almost colorless near the end point, and the color change also greatly helps to know the end point.

The reaction when a calcium compound is added after the oxidation treatment is as follows.

SeO ₄ ^2- + Ca ²⁺ → CaSeO ₄ (4) 2AsO ₄ ^3- + 3Ca ²⁺ → Ca ₃ (AsO ₄ ) ₂ (5) MoO ₄ ^2- + Ca ²⁺ → CaMoO ₄ (6)

After completion of the oxidation, molybdic acid, selenate and arsenate ions are precipitated and separated by calcium ions as sparingly soluble salts.

The solubility of a salt composed of these anions and a metal ion such as calcium ion is similar to that of sulfate, and alkaline earth metal ions having a larger atomic number than calcium or lead ions are used. By adding, the sparingly soluble salt can be precipitated by the reaction represented by the formulas (4) to (6), for example. Among them, lead ion is highly toxic and radium ion is a radioactive element, and therefore, viable elements include calcium, strontium, and barium, which are water-soluble compounds such as chlorides, nitrates, and acetates of these elements. Etc. can be used.

Further, among the three elements, the solubility decreases in the order of calcium, strontium, and barium, so that the use of barium provides the highest removal rate of impurities. However, of these compounds, the calcium compound is the cheapest, so first, most of the impurity elements other than rhenium are precipitated with calcium ions, and after the precipitation is separated, the anion impurities slightly remaining in the liquid are barium. If the precipitation is performed with ions, it is possible to obtain almost the same results as the case where the barium compound alone is recovered at a lower cost. At this time, if the barium compound is added without separating the precipitated calcium salt, the anion in the calcium salt reacts with the barium ion as shown in formula (7). Therefore, be sure to add the barium compound before adding the barium compound. The sparingly soluble calcium salt formed needs to be separated.

CaSeO ₄ + Ba ²⁺ → BaSeO ₄ + Ca ²⁺ (7) CaSeO ₄ + CO ₃ ^2- → CaCO ₃ + SeO ₄ ^2- (8)

Regarding the liquid property in the case of forming precipitates, any of perrhenic acid, molybdic acid, selenate, and arsenate ions becomes more stable as the pH increases, but conversely, when the pH is too high, salts formed are, for example ( Since the metathesis reaction due to the reaction like the formula 7) releases the anion again, the pH is 1 or less.
It is most suitable to be 0 or less, especially around pH 5 to 9.

As for the reaction temperature, the reaction itself proceeds at any temperature, but at the time of precipitation formation, the higher the temperature is, the less coprecipitation of other ions occurs, and the crystal growth is promoted so that the filterability is improved. Is improved.

Further, when the salt to be added is added as an aqueous solution rather than as a solid, the crystal surface is not covered with a precipitate and the reaction is rapid and uniform.

The end point of the reaction can be known by adding the alkaline earth compound solution to the mother liquor so that no more precipitate is formed. If the stirring is continued for about 1 hour after the precipitate is formed, the precipitation is completed and crystals grow to improve the filterability of the precipitated product.

Since the liquid from which impurities have been separated by precipitation does not contain anionic impurities other than perrhenic acid, a perrhenate which can be commercialized can be recovered by concentrating by a known method.

[0027]

[Example 1] (Precipitation generated only with barium salt) Rhenium: 1.11, selenium: 3.03, molybdenum: 23.0, arsenic: 0.3
When a 12% sodium hypochlorite aqueous solution was continuously added to 100 ml of an aqueous solution of pH 6.8 containing 2 (g / l), a stable voltage of 1,000 mV or more was obtained for a silver-silver chloride electrode at pH 2.7. Since it became as shown, it was regarded as the end point, and after adjusting the pH to 7 with sodium hydroxide, the temperature was raised to 90 ° C. Then, a saturated aqueous solution of barium chloride was added until no precipitate was formed, and the mixture was maintained at 90 ° C. for 1 hour while stirring. The precipitate was separated by filtration, washed with 100 ml of water, and the combined solution of the precipitate and the mother liquor and the washing liquid was analyzed.

As a result, 98% or more of selenium, 99.8% of molybdenum, and 93% or more of arsenic were precipitated. The distribution ratio of rhenium to the precipitate was less than 0.2%, which means that the components other than rhenium were almost completely distributed to the precipitate.

[0029]

Example 2 (Used together with calcium and barium) 100 ml of the liquid containing rhenium and impurities used in Example 1 was subjected to the same oxidation treatment, adjusted to pH 7, and heated to 90 ° C.
Then, a saturated aqueous solution of calcium chloride was added until no precipitate was formed, and the mixture was maintained at 90 ° C. for 1 hour while stirring. The precipitate was separated and washed with 100 ml water. The obtained filtrate and the washing solution are combined and heated again to 90 ° C., and a saturated aqueous solution of barium chloride is added until precipitation does not occur,
It was maintained at 90 ° C. for 1 hour with stirring. The precipitate was separated by filtration, washed with 100 ml of water, and then the total precipitate and the combined liquid of the mother liquor and the washing liquid were analyzed.

As a result, 99.4% or more of selenium, 99.9% or more of molybdenum, and 93% or more of arsenic were precipitated. The distribution ratio of rhenium to the precipitate was 0.4%, which was almost the same as that when barium salt alone was used as the precipitant.

[0031]

Comparative Example 1 (Effect of Oxidation) Example 2 was repeated except that no oxidation treatment was performed.
Precipitation separation tests with calcium chloride and barium chloride were carried out exactly as above, and the total precipitation and the liquid were analyzed.

As a result, the distribution ratio to the precipitate was 4 for selenium.
It was found that the precipitation of selenium was incomplete, with 7.2%, molybdenum 99.7%, and arsenic 95% or more. Further, the distribution ratio of rhenium to the precipitate was as high as 19.6%.

[0033]

Comparative Example 2 (Effect of pH) A precipitation separation test using calcium chloride and barium chloride was carried out in the same manner as in Example 2 except that the pH at the time of precipitate formation was lowered to 1.7. Was analyzed.

As a result, the distribution ratio to the precipitate was 9 for selenium.
9.1%, molybdenum 87.6%, arsenic 93% or more, and rhenium 0.4%. It can be seen that, when the pH is low, almost all the impurities can be removed by precipitation, although the precipitation of molybdenum is slightly incomplete.

On the other hand, when the precipitation was adjusted to pH 11.3 with sodium carbonate and the same test was carried out, the distribution ratio to the precipitation was 0.9% or less for selenium and 0.06 for molybdenum. %, Arsenic 7.4%, rhenium 0.3
% Or less, almost no element was precipitated. p
It can be seen that when H exceeds 10, separation of impurities becomes virtually impossible.

[0036]

According to the present invention, it is possible to separate impurity anions such as selenium, molybdenum and arsenic coexisting with rhenium from rhenium selectively and highly efficiently, which is of great industrial significance.

Claims (2)

[Claims] 1. An aqueous solution containing at least one element selected from selenium, molybdenum, and arsenic and rhenium is oxidized with an oxidizing agent, and then any one of water-soluble calcium compounds, strontium compounds, and barium compounds is used. A method for separating rhenium and impurities, characterized in that the above elements are added and elements other than rhenium are fixed as a precipitate at pH 10 or less and separated. 2. The method for separating rhenium and impurities according to claim 1, wherein after the oxidation treatment, a calcium compound is added first, the formed precipitate is separated, and then a barium compound is added.