JPS595656B2 - Method for separating arsenic from acidic aqueous solution - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for reductively separating arsenic ions contained therein from an acidic aqueous solution.

Arsenic is widely contained in copper ore, lead ore, zinc ore, and various other ores, and in the process of smelting these ores, arsenic is distributed into dust, sulfuric acid waste, blister copper, spices, etc.

These dusts, sulfuric acid waste, blister copper, spices, etc. are further processed dry or wet, and arsenic is converted into arsenite, iron arsenate,
It is separated and recovered in the form of calcium arsenate or arsenic sulfide.

Among these, when arsenous acid and arsenic sulfide are separated from aqueous solutions, the solid-liquid separation is not very easy, so although various efforts are currently being made, a more efficient arsenic separation method is desired. By the way.

Furthermore, when arsenic is separated in the form of iron arsenate or calcium arsenate, although these have better solid-liquid separation properties than arsenous acid or arsenic sulfide, large amounts of iron hydroxide and calcium hydroxide Because they are mixed and discharged at the same time, the quantity is bulky and there are many difficulties.

As a result of repeated research into the form and processing method of arsenic, which has excellent solid-liquid separation properties and minimizes the bulk of the separated product in wet processing of arsenic, the present inventor found that arsenic can be processed as metallic arsenic. We have discovered that the best method is to perform reduction precipitation from an aqueous solution.

Currently, known methods for reducing and precipitating arsenic as a metal from an aqueous solution include adding stannous chloride, hypophosphorous acid, or copper pieces to a hydrochloric-acidic solution, but these methods do not allow qualitative analysis of minute amounts of arsenic. However, there are still many difficulties in using this method as an economical method for separating and recovering arsenic.

The reaction formula for reduction of arsenic using stannous chloride and copper pieces is (1)
~ (4) It is shown in formula.

2AsC13+3SnC12=2As+3SnC14(
1) 2HAsO2+3SnC12+6HC1=2As+
3SnC14+4H20(2)AsC13+3Cu-A
s+3CuC1(3)HAs02+3Cu+3HC1=
As+3CuC1+2H20 (4) Although it is possible to separate arsenic as metal arsenic using an electrolytic method, there are currently no examples of actually collecting arsenic as a single metal arsenic using an electrolytic method.

Examples of arsenic being extracted as an alloy with copper can be seen in the copper electrolytic refining process.

During the copper electrolytic refining process, some of the arsenic contained in the blister copper at the anode is eluted into the electrolyte as the electrolysis progresses.
As electrolysis is repeated, the arsenic concentration in the electrolyte increases.

If the arsenic concentration becomes too high, arsenic also begins to be deposited on the cathode, reducing the purity of the electrolytic copper.

Therefore, decoppering film electrolysis is performed in the copper electrolytic refining process, but in this case, an alloy of copper and arsenic is electrodeposited, and pure metallic arsenic cannot be obtained.

The chloride ion concentration of the aqueous solution is increased by adding IJum (the inventor has added IJum, etc.), and the solution is kept at a temperature of 50°C to 100°C, preferably 80°C to 95°C, and is constantly stirred in a tank that does not allow air to enter. However, they discovered that arsenic ions can be reduced to metallic arsenic or arsenic amalgam with excellent sedimentation properties using copper, lead, and cadmium amalgams, or metallic copper or metallic cadmium.

This provides a method for efficiently separating and recovering arsenic from an acidic aqueous solution containing arsenic ions.

Copper, lead, etc., which are eluted into the aqueous solution by reducing arsenic ions, become chlorocomplexes with chlorine ions such as sodium chloride, so the reduction reaction proceeds smoothly.

These reaction formulas are shown in formulas (4) to (8). HAs
'2+3Cu+3HC1=As+3CuC1+2H20
(4) (Previously) CuC1+NaC1=NaCuC12 (
5) 2HAs02+3Pb+6HC1=2As+3Pb
C12+4H20(6)PbC12+NaC1=NaP
bC13(7)2HAs02+3 Cd+6HC1=2
As+3 CdCl2+4H20 (8) A higher liquid temperature shows better results for the solubility of each ion in the solution, the fluidity of each amalgam, the reduction reaction rate of arsenic, etc., but when the liquid temperature is set to 100°C or higher This requires an autoclave or the like, which is complicated in terms of equipment and operability.

The maximum temperature under normal pressure is 100°C, but when considering the material of the industrial reduction tank, etc., it can be said that the optimum liquid temperature is 80°C to 95°C.

Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Trivalent arsenic 0.5 P, NaC1100? pH0 including
, 40 TL of copper amalgam containing 4.01 copper was added to the acidic aqueous solution 11 of 5, and while stirring constantly in a glass tank that did not allow air to enter, trivalent arsenic was reduced at a liquid temperature of 90 ° C. As a result, the concentration of trivalent arsenic in the solution was 0.2' at a reaction time of 15M? /l was shown.

The entire amount of reduced arsenic is incorporated into the copper amalgam,
It became arsenic amalgam.

The fluidity of the amalgam was excellent, and the reduction reaction proceeded almost according to the theoretical formula (Cu/As = 2.54 in weight ratio).

Since the eluted copper existed as a monovalent copper chlorocomplex, it did not precipitate (the solution was almost colorless and transparent).

Separability between copper and arsenic amalgam and the solution was also good.

The same reduction reaction was repeated by changing the liquid temperature from 50°C to 100°C, but higher temperatures were better in terms of fluidity of the amalgam, reduction reaction rate, etc.

Considering the material and operability of industrial reduction tanks, it can be said that the optimum liquid temperature is 80 to 95°C.

Example 2 Trivalent arsenic concentration 0.1? /7310.01g/11
NaCl concentration O? /73.50? /73.100g/l, 150'f! /l, and when trivalent arsenic was reduced with copper amalgam using each combination under the same conditions as in Example 1, the reaction time was 15 mV.
t was sufficient.

The residual arsenic in the solution is greatly affected by the initial concentration of arsenic and the NaC1 concentration; if the NaC1 concentration is O'if/l, most of the arsenic remains in the solution without being reduced. , the reduction rate of arsenic increased.

The initial concentration of arsenic is 0.1' at NaC1 concentration x'ooP/A
? /l, the residual arsenic concentration in the solution is 0,04'?
/l, and when the initial arsenic concentration was 0.01 g/l, the residual arsenic concentration was 5~/l.

The conditions of the amalgam and solution were the same as in Example 1, and the amalgam containing arsenic could be successfully separated from the solution.

Example 3 When monovalent copper ions, lead ions, etc. are mixed in the solution, the reduction rate of arsenic by the copper amalgam is greatly affected, and as the mixed ions increase, the residual arsenic content shows a high value.

Is the monovalent copper ion concentration 10? At a high concentration of /l, most of the arsenic remained in the solution.

Arsenic concentration 1.31 g/l, lead concentration 4.3 g/l, NaC
1 concentration 200? When trivalent arsenic is reduced by adding copper amalgam to a /l solution and reducing trivalent arsenic in the same manner as in Example 1, the residual arsenic concentration in the solution is 0.98P/l, and the copper concentration in the solution due to the copper eluted from the copper amalgam is 0.98P/l. is o, t1? /l was shown.

In this case as well, the conditions of the amalgam and solution were the same as in Example 1, and the amalgam and solution could be separated smoothly.

Example 4 Trivalent arsenic 2.0? , pH 0 containing NaC1100P,
Lead 12. When 40 ml of lead amalgam containing 1 ml of lead amalgam was added and trivalent arsenic was reduced in the same manner as in Example 1, the concentration of trivalent arsenic in the solution was 0.07 ml/l at a reaction time of 151 ruIL.

The reduced arsenic is incorporated into the lead amalgam, but because the solubility of arsenic in this amalgam is limited, excess metallic arsenic was suspended in solution.

This metallic arsenic had excellent sedimentation properties, and the solution became clear in a short time when stirring of the solution was stopped.

The fluidity of the amalgam was excellent, and the reduction reaction proceeded almost according to the theoretical formula (weight ratio pb/As=4.15).

Separability between the lead and arsenic amalgam and the metallic arsenic precipitated in the solution was good, and by squeezing the lead and arsenic amalgam with a cloth, most of the arsenic in the amalgam could be collected on the cloth. .

The same reduction reaction was repeated by changing the liquid temperature from 50°C to 100°C, but in addition to the case of Example 1, the liquid temperature was high due to the sedimentation of metal arsenic suspended in the solution. It was better.

Example 5 Trivalent arsenic concentration 1.3x? /l: When trivalent arsenic was reduced with lead amalgam in the same manner as in Example 4 in a solution containing no NaCl, the reaction time was 15 m17!
The trivalent arsenic concentration of the solution is 1. o? /l.

As in the case of reduction with copper amalgam, in this case too N
It was greatly influenced by aC1 concentration.

Also, it is influenced by the lead ion concentration in the solution, and the lead concentration in the solution is set to 7? /l: In the case of closing, the reduction of trivalent arsenic hardly progressed even if lead amalgam was added thereto.

Example 6 Trivalent arsenic 2.0s, NaC1100? / p containing l
When 401 rLl of cadmium amalgam containing 6.0 L of cadmium was added to 11 of the acidic aqueous solution of H0.5 and trivalent arsenic was reduced in the same manner as in Example 1, the trivalent arsenic concentration of the solution decreased after a reaction time of 15 mm. showed 0.04 g/l.

The reduced arsenic was incorporated into the cadmium amalgam, but because the solubility of arsenic in this amalgam was limited, excess metallic arsenic was suspended in solution.

As in Example 4, the sedimentation properties of the metal arsenic and the fluidity of the amalgam were excellent, and the reduction reaction proceeded almost according to the theoretical formula (weight ratio Cd/As=2.25).

The separation between the cadmium and arsenic amalgam and the metallic arsenic precipitated in the solution was good, and by squeezing the cadmium and arsenic amalgam with a cloth, most of the arsenic in the amalgam could be collected on the cloth. .

The reduction reaction was repeated by changing the liquid temperature from 50°C to 100°C, but as in the case of the lead amalgam in Example 4, the higher the liquid temperature, the better.

Example 7 Trivalent arsenic concentration 1.0? When trivalent arsenic was reduced using cadmium amalgam in the same manner as in Example 6 in a solution containing no NaC1 at a concentration of
Is the trivalent arsenic concentration in the solution at VL 0.05? /l was shown.

Further, when reduction was performed in the same manner at trivalent arsenic concentrations of 0.1 g/l and 0.01 g/l, the arsenic concentration was 5 ynq/l or less.

Compared to reduction with copper amalgam or lead amalgam,
Not significantly affected by NaCl concentration.

Furthermore, it was not significantly affected by cadmium ion concentration or zinc ion concentration.

Example 8 Trivalent arsenic 1.0 P, NaC1100? pH0 including
, 5 to the acidic aqueous solution 11, add a small piece of metallic copper (approximately 5 x 3
When the trivalent arsenic was reduced in the same manner as in Example 1, the trivalent arsenic concentration of the solution was 0.1 P/l after a reaction time of 1 hour.

The reduced black metal arsenic peeled off from the metal copper plate and became cloudy in the solution, but its sedimentation properties were excellent, and when stirring of the solution was stopped, the solution became clear in a short time.

Unreacted metallic copper, precipitated metallic arsenic, and aqueous solution could be easily separated.

The reduction reaction proceeded almost according to the theoretical formula.

Example 9 In the same manner as in Example 2, the trivalent arsenic concentration was set to 1.0? /l
, 0.1 f/73.0.01? /l, NaCl concentration 0 g/l, 50 g/l, 100 g/l, 150 g/l
When trivalent arsenic was reduced with a small piece of metallic copper using each combination under the same conditions as in Example 8, the reaction time required about 1 hour.

Is the NaCl concentration o? /l:, arsenic was not reduced and most of it remained in the solution.

If the NaCl concentration was high (the arsenic reduction rate increased as with copper amalgam).

The initial concentration of arsenic is 0.1 at 3 degrees NaCl and 100 ft/l.
In the case of P/l, the residual arsenic concentration in the solution was 8~/l, and in the case of a cord cutting concentration of 0.01 g/l, the residual arsenic concentration was 0.8/n9/l: .

In this case as well, metallic copper, precipitated metallic arsenic, and aqueous solution could be easily separated.

Example 10 When the trivalent arsenic concentration is as high as 2.3 P/l, the precipitated metallic arsenic exhibits a black and white color, and is more plate-like than a copper plate compared to when the arsenic concentration is low. Curled and peeled off (
showed a tendency to

Further, when this material was analyzed, the component ratio was approximately Cu2As.

NaCl concentration 200? /73, the residual arsenic concentration is 1. , l/l: The copper concentration was 2.21/l.

In addition, when we looked at the influence of monovalent copper ions in the same manner as in Example 3, we found that the reduction rate of arsenic increased as the concentration of monovalent copper ions increased.
There was a significant decline.

NaCl concentration 1001/l: and arsenic concentration 0.5 ft/l
: When the monovalent copper ion concentration is 15? /l, almost no precipitation of metallic arsenic was observed.

Example 11 Trivalent arsenic 2. Or, NaC1100? pH0, including
For 11 of the acidic aqueous solution of 5, 20 of small particles of metal cadmium
When P was added and trivalent arsenic was reduced in the same manner as in Example 1, the trivalent arsenic concentration in the solution was reduced to 0.
4? /l: was shown.

The reduced black metal arsenic peeled off from the cadmium grains and became cloudy in the solution, but its sedimentation properties were excellent.

It was possible to separate unreacted metal cadmium, precipitated metal arsenic, and aqueous solution.

Moreover, the reduction reaction proceeded almost according to the theoretical formula.

The reduction reaction proceeded smoothly also when the trivalent arsenic concentration was 0.1 g/l and 0.0 IP/l.

Claims (1)

[Claims] 1. When separating arsenic from an acidic aqueous solution containing arsenic ions, copper amalgam, lead amalgam, A method for separating arsenic from an acidic aqueous solution in which arsenic ions are reduced to metallic arsenic using cadmium amalgam, metallic copper, or metallic cadmium, and then solid-liquid separation is performed.