JP5625396B2 - Purification method of diluent for organic solvent - Google Patents

Description

  The present invention relates to a method for purifying a diluent for an organic solvent, and more specifically, in a metal smelting process using an organic solvent containing an alkylnaphthalene-based diluent, a chemical oxygen demand value ( COD) The present invention relates to a method for purifying a diluent for an organic solvent capable of reducing causative substances and suppressing an increase in COD in waste water.

As a method of refining ores containing valuable metals such as copper, nickel and platinum group elements, acid such as hydrochloric acid and sulfuric acid is added to the ore and leached, and the resulting leachate is mixed with an organic extractant. There is known a method in which valuable metal ions are separated into an extractant, then valuable metal ions are separated from the extractant into an aqueous solution, and recovered from the resulting aqueous solution as metal by electrowinning (for example, a patent) Reference 1).
This Patent Document 1 is a method of mutually separating platinum group elements from platinum group element-containing materials containing impurity elements. The platinum group element-containing materials are suspended in a hydrochloric acid solution, added with an oxidizing agent, and subjected to leaching. A step of obtaining a leaching product solution containing a platinum group element, and then subjecting the leaching product solution to contact with an organic extractant for solvent extraction to form an organic phase containing an impurity element and an extraction residue. Is described.

  Organic extractants such as tri-normal octylamine or triisooctylamine used in the solvent extraction method for separating valuable metals have a specific gravity suitable for operation by adding a diluent to the stock solution of the organic solvent that is the extractant in advance. Adjusted to viscosity. Many organic compounds such as 3rd petroleum have been used as diluents, but recently they are higher than organic solvents such as 3rd petroleum in terms of fire safety and working environment. Compounds with boiling points and low viscosity are considered suitable.

Patent Document 1 also exemplifies an alkylnaphthalene-based diluent obtained as a by-product of a petroleum refining process.
However, in a solvent extraction process using an organic solvent containing an alkylnaphthalene-based diluent, a chemical oxygen demand value (COD) on the aqueous phase side such as an acid solution that contacts with the organic phase of the organic solvent to give and receive metal ions. : Chemical Oxygen Demand) increased, and as a result, the load of the wastewater treatment process increased.
The increase in COD in the aqueous phase is considered to be caused by the physical mixing of the organic solvent into the aqueous phase depending on the viscosity of the organic solvent itself and chemical dissolution of the major components of the organic solvent.
However, the alkylnaphthalene-based organic compound, which is the main component of the diluent, has a certain solubility in water, but the increase in COD in actual operation exceeded the amount commensurate with this solubility.

  On the other hand, in the treatment of wastewater containing organic substances and hardly decomposable compounds, oil / water separators, activated carbon adsorbers, and oxidation / removal devices using ozone, chlorine and ultraviolet rays are generally installed to decompose organic components, Discharge processing has been performed after reducing the COD value to the environmental standard (see, for example, Patent Document 2).

In Patent Document 2, in a method of treating wastewater by irradiating wastewater with ultraviolet rays using an oxidation removing device (reaction tank), the dissolved oxygen (DO) in the reaction tank is controlled.
Thereby, the ultraviolet irradiation efficiency is increased, and COD components and BOD components such as organic substances and reducing sulfur compounds contained in the wastewater are efficiently oxidized and decomposed, and COD and BOD in the wastewater can be reduced.

  Further, for example, in Patent Document 3, waste water containing salt dissolved in organic substances accompanying petroleum refining is brought into contact with an adsorbent (zeolite), and dissolved organic substances in the waste water are adsorbed and removed. A processing method for desorbing and regenerating the adsorbent is shown. This method is characterized in that, before contacting the adsorbent with the wastewater in which organic matter is dissolved in the oil refining (oil field associated water) and the adsorbent, the wastewater is separated into oil or water, or oil droplets in water are separated by magnetic separation. This is a method for removing dissolved organic matter.

  For this reason, even in the smelting process using the solvent extraction step as described above, it is conceivable to perform waste water treatment similar to the methods of Patent Documents 2 and 3. However, there is a problem that requires a specific adsorbent and an oxidation removal device, and requires considerable costs for installation and operation of the device, which is not advantageous for treatment of smelting wastewater.

  As described above, there is no known method for separating a causative substance for increasing COD from an organic solvent containing an alkylnaphthalene-based diluent at low cost, and the emergence of an economical method for purifying an alkylnaphthalene-based diluent. Was desired.

JP 2005-97695 A Japanese Patent Laid-Open No. 10-34171 Republished patent WO2006 / 049149

  In view of the problems of the prior art, the object of the present invention is to cause chemical oxygen demand (COD) contained in an organic solvent in a metal smelting process using an organic solvent containing an alkylnaphthalene-based diluent. An object of the present invention is to provide a method for purifying a diluent for an organic solvent capable of reducing substances and suppressing an increase in COD in waste water.

  As a result of intensive studies to solve the problems of the prior art, the present inventors include a normal salt prior to using an alkylnaphthalene-based diluent in a solvent extraction process for separating valuable metals from ore. By washing with an aqueous solution, removing non-aromatic substances such as sulfolane in the diluent, and purifying the alkylnaphthalene-based diluent, the organic matter-derived components in the wastewater generated from the solvent extraction process are reduced. The present inventors have found that COD in waste water can be reduced, and have completed the present invention.

That is, according to the first invention of the present invention, the purification of an alkylnaphthalene-based diluent for organic solvents used for extracting an acid leaching solution of a non-ferrous metal-containing ore with an organic solvent diluted with a diluent. The alkylnaphthalene-based diluent has a boiling range of 195 to 250 ° C., and the refining has a specific gravity difference of 0.08 g / cm ³ or more with the alkylnaphthalene-based diluent. An aqueous solution containing a certain normal salt was added, washed with shaking, and the non-aromatic sulfolane contained in the alkylnaphthalene-based diluent was separated into the aqueous phase, and the chemical oxygen demand value of the aqueous phase ( method for purifying an organic solvent for dilution agent characterized Rukoto reduce COD) below 50 mg / l is provided.

According to the second invention of the present invention, in the first invention, the normal salt is at least one selected from sodium sulfate, sodium chloride, or calcium chloride. A purification method is provided.
According to the third invention of the present invention, in the first invention, the alkylnaphthalene-based diluent has a specific gravity difference of 0.1 to 0.2 g / cm ³ with respect to the aqueous solution containing the normal salt. A method for purifying a diluent for organic solvents is provided.
According to a fourth aspect of the present invention, there is provided a method for purifying a diluent for an organic solvent according to the first aspect, wherein the organic solvent is tri-normal octylamine or triisooctylamine. Is done.

  According to the present invention, since non-aromatic substances contained in the undiluted solution of the alkylnaphthalene-based diluent are removed, accumulation of non-aromatic substances, which is a heavy load in the wastewater treatment apparatus, is suppressed, so that the operation can be performed. Stabilize. Further, since the COD treatment facility for the drainage process only needs to have a scale that removes only the minimum dissolved components, the load on the drainage process can be reduced. Furthermore, although a large amount of COD is contained in the cleaning water, it is far less than the amount of waste water, and the loss of organic solvent is suppressed, so that the processing cost is greatly reduced.

  Hereinafter, the purification method of the diluent for organic solvents of the present invention will be described in detail.

1. Purification method for organic solvent diluent The organic solvent diluent purification method of the present invention is an organic solvent used to extract an acid leaching solution of a non-ferrous metal-containing ore with an organic solvent diluted with a diluent. The alkylnaphthalene-based diluent has a boiling point range of 195 to 250 ° C., and the alkylnaphthalene-based diluent has a specific gravity difference from the diluent during purification. An aqueous solution containing a normal salt of 0.08 g / cm ³ or more is added, washed with shaking, and the non-aromatic sulfolane contained in the alkylnaphthalene-based diluent is separated into an aqueous phase. chemical oxygen demand value (COD), characterized in Rukoto reduced below 50 mg / l of.
In the present invention, an aqueous solution containing a normal salt is added to a stock solution of an alkylnaphthalene-based diluent, and the mixture is washed with a shaker with a purifier to separate a non-aromatic substance contained in the stock solution into an aqueous phase.

  In the present invention, the organic solvent is not particularly limited as long as it is used in a solvent extraction method for separating valuable metals, but organic compounds such as tri-normal octylamine (TNOA) and triisooctylamine (TIOA) can be used. Can be mentioned. Since these organic compounds have high viscosity, they must be diluted with an alkylnaphthalene-based diluent. Viscosity depends on the power performance of stirring the solvent and aqueous solution and the extraction amount of the extractant, but is generally in the range of 20 to 100 mPa · s, preferably 30 to 50 mPa · s, based on the amount after extraction. A sufficient amount of diluent is blended.

  The alkylnaphthalene-based diluent is produced from a petroleum-based hydrocarbon containing a boiling point range of 140 ° C. or higher and at least 40% by mass of an aromatic hydrocarbon compound. The product is separated from the distillation column of the petroleum refining apparatus, and further, an aromatic hydrocarbon compound is extracted using a solvent such as sulfolane to obtain a specific fraction having a boiling range of 195 to 250 ° C. Alkylnaphthalene is a polycyclic aromatic hydrocarbon compound such as naphthalene, methylnaphthalene, ethylnaphthalene, dimethylnaphthalene, and trimethylnaphthalene.

The commercially available alkylnaphthalene-based diluent has a content of these aromatic hydrocarbon compounds of about 99% by volume, but when mixed in an organic solvent and treated in a solvent extraction step, the resulting aqueous phase contains In addition to the alkylnaphthalene-based organic compound itself, components derived from the non-aromatic sulfolane are contained.
Sulfolane is a cyclic sulfone, also known as tetramethylene sulfone. As mentioned above, benzene, toluene, and xylene are extracted and purified by distillation in the process of producing petroleum hydrocarbons that are raw materials for alkylnaphthalene-based diluents. Although it is used as a solvent to be separated in step (b), it cannot be completely separated from alkylnaphthalene (polycyclic aromatic hydrocarbon compound) and partly remains.

  Therefore, in the present invention, the alkylnaphthalene-based diluent is washed prior to use in the solvent extraction step after being mixed with an organic solvent, and the sulfolane component in the diluent is removed before use.

  Any aqueous solution that does not react with alkylnaphthalene can be used as the cleaning solution used for the purification of the above-mentioned alkylnaphthalene-based diluent. However, in the present invention, a neutral solution that is neutral and has a large specific gravity difference from alkylnaphthalene. It is necessary to use a solution containing salt. The normal salt is a salt in which neither H + nor OH- is contained in the chemical formula, and a normal salt composed of a salt of a strong acid and a strong base is preferable.

  Specific examples of the normal salt preferred in the present invention include neutral salts that do not change the pH of the solution even when dissolved in water, such as sodium chloride, sodium sulfate, and calcium chloride. These may not be particularly pure and can be used alone or in a mixture of two or more. Of these, sodium sulfate is most suitable in consideration of the cost, the influence on the corrosion resistance of the equipment, and the formation of deposits.

The aqueous solution containing the normal salt has a specific gravity difference with the alkylnaphthalene-based diluent of 0.08 g / cm ³ or more, preferably 0.1 g / cm ³ or more. This is because the larger specific gravity difference makes the separation clearer in actual operation, and there are advantages such as effective washing with a small amount of washing water. If the specific gravity difference is too small and less than 0.08 g / cm ³ , physical dissolution will increase, and in addition to sulfolane, the main component alkylnaphthalene will be physically dissolved in the solution. Ingredient loss increases.
The greater the specific gravity difference between the normal salt and the diluent, the better the cleaning efficiency is generally. However, when the specific gravity difference is extremely large, it becomes difficult to make contact during mixing. In addition, when adjusting the concentration of the normal salt, even if the concentration is excessively increased, the cost increases, which is disadvantageous. Therefore, the upper limit is preferably set to 0.2 g / cm ³ or less.

Moreover, the washing | cleaning apparatus of the alkylnaphthalene type diluent by the aqueous solution containing a normal salt is not restrict | limited especially, Processing temperature is not restrict | limited in particular, You may carry out at normal temperature or may heat. Usually, the temperature is within a range from room temperature to 50 ° C.
The number of washings is not particularly limited, but it is more effective to repeat in multiple steps. It is preferable to repeat three or more times so that the non-aromatic substance is reduced to a chemical oxygen demand value (COD) of 50 mg / l or less, but even if it is repeated five or more times, the effect is hardly changed.

  In the present invention, the method for purifying the alkylnaphthalene-based diluent has been described in detail. However, in the solvent extraction step of metal smelting, xylene, trimethylbenzene, tetramethylbenzene, propylbenzene, which are monocyclic aromatic hydrocarbon compounds, Alkylbenzenes such as ethylmethylbenzene and diethylbenzene are also used. The present invention can also be applied to a purification method for these alkylbenzene-based diluents.

2. Use of alkylnaphthalene-based diluent in solvent extraction step The alkylnaphthalene-based diluent purified by the above method is preferably used in the solvent extraction step of metal smelting.

  That is, the organic phase from the purification apparatus is mixed with an organic solvent as an alkylnaphthalene-based diluent and supplied to the extraction apparatus together with the smelting leachate. In the extraction device, the smelting leachate is separated into an organic phase (impurity element) and the extraction residual liquid, and the extraction residual liquid is supplied to the next smelting process.

  Thereby, the organic matter origin component to the waste_water | drain produced | generated from a solvent extraction process reduces, and also reduces the COD in waste_water | drain. Although a large amount of COD is contained in the washing water, the treatment cost is greatly reduced compared with the amount of waste water.

  Next, the method for purifying the diluent for organic solvents of the present invention will be specifically described with reference to examples. However, the present invention is not limited to this example.

Example 1
First, about 80 g of a sodium sulfate aqueous solution as a normal salt was dissolved so as to have a ratio of 1 liter of pure water to prepare a cleaning liquid having a specific gravity of 1.05 g / cm ³ . Next, this cleaning liquid was mixed with an alkylnaphthalene-based diluent (trade name: SWAZOL 1800 manufactured by Maruzen Petrochemical Co., Ltd.) used in the solvent extraction step of metal smelting. At this time, the concentration of the normal salt is such that the specific gravity difference between the organic solvent and the cleaning liquid is 0.12 g / cm ³ .
Diluent and washing liquid are mixed in the same volume and placed in a separatory funnel, shaken at room temperature for 5 minutes using a shaker, and then allowed to stand for 10 minutes to separate the organic phase and aqueous phase. . Thereafter, the aqueous phase side was collected as a sample, filtered through 5C filter paper, made into an aqueous solution after washing, and subjected to COD analysis. Next, a series of steps of adding the cleaning liquid having the same composition as above to the organic solvent and shaking to collect the aqueous phase after the phase separation was repeated a total of 5 times. Table 1 shows the COD analysis values of the washed aqueous solution obtained by phase separation.

  The COD value discharged from the organic solvent to the aqueous phase in the first washing was 1300 mg / l, but as the washing was repeated, COD was discharged from the organic solvent and gradually decreased.

In addition, when the washing | cleaning liquid obtained after the 5 times washing | cleaning of the said Table 1 was analyzed, sulfolane was hardly contained and the whole quantity was the alkyl naphthalene type diluent. In this way, the alkylnaphthalene-based diluent itself dissolves in the aqueous phase to such an extent that the COD value is about 20 mg / l. Therefore, the sulfolane in the diluent was selectively separated by the cleaning method of this example. It will be.
The purified alkylnaphthalene-based diluent is mixed with an organic solvent (such as tri-normal octylamine or triisooctylamine) and supplied to the extraction device together with the smelting leachate, and the organic phase (impurity element) and aqueous phase (extraction) If the residual liquid is separated, the COD substance in the aqueous phase (extracted residual liquid) is greatly reduced, so that wastewater treatment can be performed at low cost.

(Examples 2 and 3) (Comparative Example 1)
When adding sodium sulfate based on pure water, the sodium sulfate concentration was changed to give a specific gravity difference, and the cleaning effect at that time was compared.
As the cleaning solution, the concentration of sodium sulfate was changed for each cleaning, and as shown in Table 2, the cleaning solution was prepared so as to produce a concentration difference of 0.07 to 0.13 g / cm ³ with the organic solvent. Using this washing solution, washing was carried out over 5 stages in the same manner as in Example 1, and the COD value of the obtained 5th-stage washing solution was analyzed. Table 2 shows the COD analysis values of the washed aqueous solution obtained by phase separation.

In Examples 2 and ³ in which the specific gravity difference was 0.08 g / cm ³ or more in the above cleaning, the COD was 50 mg / l or less, whereas the specific gravity difference was less than 0.08 g / cm ^3. In Comparative Example 1, the cleaning liquid became cloudy. Analysis of the cleaning solution is not preferable because it is observed that physical dissolution of the organic solvent in the aqueous solution is progressing, resulting in a large loss of the active ingredient in the organic material. From the above, it can be seen that it is preferable to use a solution having a specific gravity difference of 0.10 g / cm ³ or more in order to prevent loss of the alkylnaphthalene-based diluent in washing.

Claims (4)

A method for purifying an alkylnaphthalene-based diluent for an organic solvent , which is used to extract an acid leaching solution of a non-ferrous metal-containing ore with an organic solvent diluted with a diluent,
The alkylnaphthalene-based diluent has a boiling range of 195 to 250 ° C., and contains a normal salt having a specific gravity difference of 0.08 g / cm ³ or more in the alkylnaphthalene-based diluent during purification. The non-aromatic sulfolane contained in the alkylnaphthalene-based diluent is separated into an aqueous phase, and the chemical oxygen demand value (COD) of the aqueous phase is 50 mg / method for purifying an organic solvent for dilution agent characterized Rukoto reduced to l or less.   The method for purifying a diluent for organic solvents according to claim 1, wherein the normal salt is one or more selected from sodium sulfate, sodium chloride, or calcium chloride. The method for purifying a diluent for an organic solvent according to claim 1, wherein the alkylnaphthalene-based diluent has a specific gravity difference of 0.1 to 0.2 g / cm ³ with respect to an aqueous solution containing a normal salt.   The method for purifying a diluent for organic solvents according to claim 1, wherein the organic solvent is tri-normal octylamine or triisooctylamine.