JP2001201495A - Method for quantifying total cyanogen in aqueous solution containing cyano-complex - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for fully separating total cyanogen in an aqueous solution containing a heavy-metal cyano-complex through distillation and simply and accurately determining it. SOLUTION: The quantifying method is comprised of a process to distill an aqueous solution, containing a heavy-metal cyano-complex in the presence of a reducing agent to generate hydrogen cyanide, a process for making an alkali absorbent absorb the generated hydrogen cyanide, and a process for measuring the amount of cyanogen in the absorbent which has absorbed the hydrogen cyanide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for simply and accurately determining the total amount of cyan in an aqueous solution containing a heavy metal cyano complex, particularly a gold cyano complex.

[0002]

2. Description of the Related Art The total cyanide concentration of wastewater is strictly regulated by wastewater standards, and finding this concentration is important in wastewater management such as wastewater treatment.

[0003] A method of analyzing total cyanide in wastewater flowing into public water is described, for example, in JIS K0102.
In this method, wastewater containing almost no heavy metal is acidified with phosphoric acid, distilled in the presence of EDTA, and the separated hydrogen cyanide is absorbed into an absorbing solution for quantification. However, when the total cyan in an aqueous solution such as a plating solution containing a heavy metal such as gold or a plating waste solution is analyzed by a method described in JIS K0102, cyano is difficult to dissociate in the aqueous solution (having a large stability constant). Only a small amount of cyan can be separated during the distillation.

In order to decompose a heavy metal cyano complex with an acid or the like, it is necessary to heat the mixture with sulfuric acid or a mixture of sulfuric acid and phosphoric acid until it becomes white smoke, and it is extremely difficult to collect hydrogen cyanide generated at this time. It is.

As a method for analyzing total cyanide in a solution containing gold or the like, a method by liquid chromatography has been reported (for example, Pohlandt-Watson, C .; Hemmings,
MJ, S. Afr. J. Chem. (1988) 41 (4), 136-140.). In this method, since the cyano complex is directly quantified without distillation, there is no problem that the amount of separated cyan is small unlike the case of analysis by the method described in JIS K0102. However, when this method is used to analyze total cyanide in aqueous solutions such as plating solutions containing various heavy metals and plating wastewater, it is not possible to determine the total cyanide concentration without quantifying all the heavy metal cyano complexes present. It takes.

[0006]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above circumstances, and provides a method for easily and accurately quantifying all the cyanide in an aqueous solution containing a heavy metal cyano complex by distillation. The purpose is to:

[0007]

In order to achieve the above object, the present invention provides a method for determining total cyanide in an aqueous solution containing a cyano complex, comprising the steps of: distilling an aqueous solution containing a heavy metal cyano complex in the presence of a reducing agent; , A step of absorbing the generated hydrogen cyanide in an alkaline absorbing liquid, and a step of measuring the amount of cyan in the absorbing liquid that has absorbed the hydrogen cyanide.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Basically, in the present invention, hydrogen cyanide liberated by a reducing agent is distilled and absorbed in an alkaline absorbing solution, and cyan in the absorbing solution is measured.

In the present invention, a heavy metal cyano complex contained in an aqueous solution such as a plating solution or a plating waste solution is dissociated into heavy metal ions and cyanide ions by a reducing agent.
The dissociated heavy metal ions are relatively easily reduced to metal. On the other hand, cyanide ions are released as hydrogen cyanide when the aqueous solution is acidic, and the released hydrogen cyanide is vaporized by distillation. For this reason, all cyan in the aqueous solution containing the heavy metal cyano complex can be sufficiently separated. The addition of the reducing agent may be performed before, after, or simultaneously with the adjustment of the aqueous solution liquidity.

The reducing agent used in the present invention is required to be acidic and have a reducing action, and that the gas generated during the reducing reaction does not affect the absorption of hydrogen cyanide. Examples of such reducing agents include hydrazine, hydrazine salts, hydroxylamine, sulfurous acid, sulfites, stannous chloride, metallic iron,
Metal zinc, metal aluminum, metal tin and hypophosphorous acid can be mentioned. These have a slow reduction reaction. Since sodium borohydride undergoes a strong reduction reaction and rapidly generates gas, the absorption of hydrogen cyanide becomes insufficient.

In the present invention, a known distillation separation method such as the analysis method of JIS K0102 can be used except for using a reducing agent as described above.

The amount of cyan in the absorbing solution is measured by pyridine-pialazolone spectrophotometry, 4-pyridinecarboxylic acid-
Pyrazolone absorption spectroscopy and ion electrode methods can be used.

FIG. 1 shows the flow of the quantification method of the present invention.

[0014]

[Examples 1 to 3] Aqueous samples A (Example 1) and B containing gold (I) cyanide and gold (III) cyanide
(Example 2) and 50 ml of each of C (Example 3) were prepared. At this time, the total cyan concentration was set to 4.4 for the aqueous solution sample A.
mg / l, B: 7.2 mg / l, C: 10.3 mg / l
I tried to be.

These aqueous samples were placed in a still, and then ammonium amidosulfate, hydrazinium chloride (reducing agent), EDTA and phosphoric acid were added to the aqueous sample in that order. Here, the amount of hydrazinium chloride added was 0.1 g in each of the examples.

Then, the aqueous solution sample was distilled, and the generated hydrogen cyanide was guided to and absorbed by an aqueous sodium hydroxide solution as an absorbing solution.

Further, the volume of the aqueous sodium hydroxide solution having absorbed hydrogen cyanide was made constant, and then cyanide was quantified by 4-pyridinecarboxylic acid-pyrazolone absorptiometry. The calibration curve used at this time was prepared using an aqueous solution of sodium cyanide as a standard solution.

[Conventional Example] Total cyan was determined in the same manner as in Example 1 except that hydrazinium chloride was not used. That is, the total amount of cyan in the aqueous solution sample A was determined by the same method as in JIS K0102.

Table 1 shows the measurement results of all cyan in the example and the conventional example.

[0020]

[Table 1]

[0021]

According to the present invention, an aqueous solution containing a heavy metal cyano complex, for example, all the cyanide in a gold plating solution or a gold plating waste solution can be sufficiently separated by distillation, and therefore can be simply, accurately and accurately performed. It can be quantified. Therefore, the present invention can greatly contribute to this field, for example, the plating solution can be managed in the plating process, and the method and the process management of the plating waste liquid treatment can be performed more quickly and accurately.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of a quantification method of the present invention.

Continued on the front page F term (reference) 2G042 AA01 BA20 BB19 CA10 CB03 EA04 FA02 FA04 HA07 2G054 AA02 AB10 BB02 BB20 CA10 CE01 CE10 EA04

Claims (5)

[Claims] 1. A step of distilling an aqueous solution containing a heavy metal cyano complex in the presence of a reducing agent to generate hydrogen cyanide, a step of absorbing the generated hydrogen cyanide in an alkaline absorbing solution, and a step of absorbing hydrogen cyanide in the absorbing solution having absorbed hydrogen cyanide. A method for determining total cyanide in a cyano complex-containing aqueous solution, comprising a step of measuring the amount of cyanide. 2. The method according to claim 1, wherein the heavy metal is gold. 3. The method according to claim 1, wherein the aqueous solution is a plating solution or a plating waste solution. 4. The reducing agent is hydrazine, hydrazine salt,
Hydroxylamine, sulfite, sulfite, stannous chloride,
The method for quantifying total cyanide in a cyano complex-containing aqueous solution according to claim 1, which is at least one selected from the group consisting of metallic iron, metallic zinc, metallic aluminum, metallic tin and hypophosphorous acid. 5. The method according to claim 5, wherein the amount of cyanide in the absorbing solution is measured by pyridine-pialazolone spectrophotometry,
The method for quantifying total cyanide in a cyano complex-containing aqueous solution according to claim 1, wherein a pyrazolone absorptiometry or an ion electrode method is used.