KR100458402B1 - Recovery of Heavy Metals from Electroplating Waste Water by Solvent Extraction - Google Patents

Abstract

The present invention relates to a method for recovering heavy metals from plating wastewater, and more particularly, to a method for recovering heavy metals such as iron, zinc, copper, and nickel in plating wastewater using a solvent extraction method, which is not saponified as an extractant. A first extraction step of extracting and recovering iron and zinc from the plating wastewater using an organic solution obtained by mixing 2-ethylhexyl hydrogen 2-ethylhexyl phosphate in a state with an organic solvent together with a third phase And a second extraction step of extracting and recovering copper and nickel from the plating wastewater from which iron and zinc have been extracted in the first extraction step using an organic solution mixed with an organic solvent together with a third phase inhibitor in a saponified state. The present invention relates to a method for recovering heavy metals from plating wastewater.

By recovering heavy metals from the plating wastewater by solvent extraction using the method of the present invention, it is possible to selectively separate and recover iron, zinc, copper and nickel, and to recycle waste resources, thereby providing an economical recovery method. It is easy to process and has high recovery rate and concentration effect of heavy metal.

Description

Recovery of Heavy Metals from Electroplating Waste Water by Solvent Extraction}

The present invention relates to a method for recovering heavy metals from plating wastewater, and more particularly, plating wastewater containing heavy metals such as iron, zinc, copper and nickel using 2-ethylhexyl hydrogen 2-ethylhexyl phosphate as an extractant. And a method for recovering heavy metals using a solvent extraction method.

It is estimated that about 3,000 small companies are carrying out plating industry nationwide, and if one company discharges an average of 40 tons / day of wastewater, 36 million tons of wastewater is generated annually, which is 360,000 tons Sludge is generated per year.

The biggest problem in the treatment of the plating wastewater is that the final plating residue and the flushing water are mixed and discharged, and the wastewater of AA (acid / alkali), Cr (chromium) and CN (cyanide) wastewater is discharged. It is collected and treated with mixed plating wastewater rather than separate discharge and treatment, which reduces treatment efficiency and heavy metal removal rate compared to single wastewater, and increases the cost of manufacturing process cost due to high processing cost. have. The current treatment method is a rudimentary step of discharging heavy metal sludge by treating plating wastewater of various components by simple reduction, oxidation, and neutralization process. In this case, as mentioned above, it is effective together with the contamination problem due to the high content of heavy metal sludge. Resources are wasted.

Plating wastewater contains heavy metals such as iron, zinc, copper, and nickel, which must be accompanied by treatment methods to selectively recover them. Although many studies have been made to recover heavy metals from plating wastewater, most of the metal components are recovered as sludge and environmentally treated because of the lack of economical and practical techniques. Heavy metal treatment methods that have been studied up to now are described in Hydrometallurgy 8 (1982), page 309; Plating and Surface Finishing 77-7 (1990) p. 22; Metal Finishing 90-1A (1992), page 786, and US Pat. Nos. 6,214,233, 6,315,906, and 6,346,195.

Sulfuric acid treatment of the treatment method is one of the typical wet treatment method, when the plating sludge is dissolved in sulfuric acid and then zinc powder is added, the cadmium metal is precipitated while the zinc powder is dissolved by the difference in ionization tendency. In the zinc solution, the zinc metal is deposited on the surface of the cathode by electrolysis to separate and recover zinc / cadmium. However, since concentrated zinc cannot be recovered completely, a certain amount of zinc remains in the solution and requires separate water treatment.

In addition, the chlorination volatilization is chlorinated zinc, cadmium, copper, etc. to make pellets, and then burned at a high temperature of about 1,250 ℃ to generate and volatilize the zinc, cadmium, copper chloride. Zinc, cadmium and copper chlorides volatilized with the waste gas are separated from the waste gas by absorption with water. The aqueous metal solution obtained in this manner was recovered copper, iron and zinc by cementation with iron powder and precipitation method by pH adjustment, and then recovered as cadmium sulfide (CdS) by adding sodium sulfide (Na ₂ S) to the remaining solution. Reuse as cadmium raw material. However, since the recovery process is complicated after conversion to chloride and chromium or nickel does not volatilize and remains in the pellet, a separate treatment process is required when recovering these metals.

Meanwhile, the solvent extraction method is also called liquid ion exchange (Liquid Ion Exchange), and in order to extract specific metal ions present in the aqueous solution, the aqueous solution and the organic solution differ in specific gravity when the aqueous solution and the insoluble organic solution are brought into contact with each other at constant ratio. It is a component separation method of extracting by moving the target component to the organic solution by using the phenomenon that the target component is distributed between the two phases while phase separation by. Due to the simplicity of the process, the possibility of efficient extraction separation, and the continuous development of extractants, this method has been extended to the application of rare metals as well as commercial non-ferrous metals and special metals related to the nuclear industry, instead of the existing smelting methods. have.

Separation and recovery of heavy metals from the plating wastewater by solvent extraction can simplify the process compared to recovering heavy metals from the plating sludge and significantly reduce the amount of sludge generated during the neutralization of residual wastewater after recovery. There are advantages to it. Since heavy metals in the plating wastewater are cations, a cation exchange extractant should be used. At this time, if diethylhexylphosphoric acid (D2EHPA) is used as an extractant, the extraction rate is lowered because the pH of the aqueous phase decreases due to the increase of hydrogen ions during extraction. There is this. In the case of using Naphthenic Acid or Versatic Acid-10, the extraction rate of the metal is about 10%, which is less effective than other cationic extractants.

Therefore, the present invention has been devised in view of the problems of the prior art, and the process of recovering heavy metals from the conventional plating waste water is complicated and a separate water treatment process for residues is required to prevent environmental pollution after treatment. It is an object of the present invention to provide a method for recovering heavy metals using solvent extraction from plating plating wastewater, which can solve the disadvantages.

Another object of the present invention is high recovery and concentration effect of heavy metals in the plating wastewater, and it is possible to selectively separate and recover iron, zinc, copper and nickel, and greatly reduce the amount of sludge generated during neutralization of residual wastewater after heavy metal recovery. It is possible to provide a method for recovering heavy metals using solvent extraction from plating waste water, which can minimize environmental pollution.

An object of the present invention is to recover a heavy metal such as iron, zinc, copper and nickel in the plating wastewater by using a solvent extraction method, using 2-ethylhexyl hydrogen 2-ethylhexyl phosphate as an extractant without saponification solvent A first extraction step of recovering iron and zinc by an extraction method; And a second extraction step of recovering copper and nickel by solvent extraction using a saponified extractant.

More specifically, the present invention is a method for recovering heavy metals such as iron, zinc, copper and nickel in the plating wastewater by using a solvent extraction method, 2-ethylhexyl hydrogen 2-ethylhexyl without saponification as an extractant A first extraction step of extracting and recovering iron and zinc from the plating wastewater using an organic solution in which phosphate is mixed with an organic solvent together with a third phase inhibitor and an organic solvent together with the third phase inhibitor in a saponified state. And a second extraction step of extracting and recovering copper and nickel from the plating wastewater from which iron and zinc have been extracted in the first extraction step using an organic solution mixed with the above. do.

As described above, in the solvent extraction method, in order to extract specific metal ions present in the aqueous solution, the aqueous solution and the insoluble organic solution are brought into contact with each other at a constant ratio. It is a component separation method of extracting by moving the target component to the organic solution using the phenomenon distributed between.

In the metal extraction method of the present invention which extracts the metal in the plating wastewater using such a solvent extraction method, 2-ethylhexyl hydrogen 2-ethylhexyl is an extractant for separating and extracting iron and zinc in the first extraction step. Phosphate is used as an organic solution in a concentration of 20% by volume to 30% by volume without mixing with an organic solvent. The ratio of plating wastewater containing heavy metals to organic solution in the first extraction step (A / O) is 1 to 3, and 2% to 4% by volume of the third phase inhibitor based on the total volume of the extractant-containing organic solution in order to prevent the third phase from being produced in the first extraction step. Add to

The organic solvent includes, but is not limited to, kerosene, hexane, benzene, toluene, chloroform and the like. Kerosene is preferred economically.

The third phase inhibitors include, but are not limited to, decanol, octanol, dodecanol, and the like. Decanol is commonly used.

In the second extraction step of extracting copper and nickel after the first extraction step, the concentration and the ratio of the extractant in the extractant-containing organic solution are the same as in the first extraction step, and the saponification degree of the extractant is 10% to 14%. In the second extraction step, the third phase inhibitor is added in an amount of 4% by volume to 8% by volume based on the total volume of the extractant-containing organic solution.

2-ethylhexyl hydrogen 2-ethylhexyl phosphate, an extractant used for the recovery of heavy metals from the plating wastewater, is an organic phosphoric acid, and hydrogen is generated during the extraction reaction. As a result, the pH of each extraction tank changes as the extraction reaction proceeds. Since maintenance of a certain extraction condition is very difficult, saponification is performed as a solution to this.

In general, saponification means neutralizing the organic acid with alkali, and in solvent extraction, saponification reaction adds an alkali such as NH ₄ OH to the cation exchange extractant so that the H ⁺ of the extractant is replaced with NH ₄ ⁺ of the ammonia water. Water is produced and is expressed as in the following equation.

H ₂ R ₂ + NH ₄ OH → NH ₄ (HR ₂ ) + H ₂ O

By controlling the amount of ammonia water added to saponification, the balance of acidity after extraction is controlled, and the balance of acidity has a great influence on the extraction rate. However, when an excess amount of ammonia water is added, the pH is increased, the hydroxide of metal precipitates during the extraction process, and the three phases of the organic metal are formed. Therefore, the saponification reaction must be performed within a pH range in which no three phases are formed.

In the present invention, the first solvent for recovering the iron and zinc by the solvent extraction method using the solvent extraction method to recover the heavy metals from the plating wastewater, using 2-ethylhexyl hydrogen 2-ethylhexyl phosphate not saponified as extractant After performing the extraction step, a second extraction step is performed in which the extractant is saponified with ammonia water to recover copper and nickel in the plating wastewater.

According to the present invention, 2-ethylhexyl hydrogen 2-ethylhexyl phosphate, which is an extractant in the first extraction step of extracting iron and zinc from the plating wastewater, has a concentration of 20 vol% to 30 vol% as a mixed solution with an organic solvent, Preferably at a concentration of 25% by volume. When the concentration of the extractant is less than 20% by volume, the extraction rate of iron and zinc is reduced to 90% or less, and when it exceeds 30% by volume, partial separation and recovery are difficult because nickel and copper are partially extracted in the first extraction step. Become.

In the first extraction step described above, the extractant is used in a state without saponification with ammonia water. Iron and zinc are almost always extracted at pH 2 or less even without saponification. However, when saponification increases the pH, copper and nickel are extracted.

The phase ratio (A / O) of the plating wastewater and the organic solution is 1 to 3, preferably 2 is good. Here, when the ratio (A / O) is out of the range of 1 to 3, that is, when the ratio (A / O) is less than 1, the extraction ratio of iron and zinc is about 100%, but the concentration of iron and zinc in the organic solution is too low. It is not effective for the recovery of iron and zinc. If it is greater than 3, the concentration of iron and zinc in the organic solution is very high, but their extraction rate is considerably reduced.

In the first extraction step, the third phase inhibitor is added to the organic solution in an amount of 2% by volume to 4% by volume based on the total volume of the extractant-containing organic solution. When the amount of the third phase inhibitor is less than 2% by volume, it is difficult to extract three phases in the plating wastewater during extraction, and when the amount of the third phase inhibitor exceeds 4% by volume, the extraction rate of zinc is reduced.

In the first extraction step, 100% of iron and zinc in the plating wastewater are extracted, and copper and nickel are not extracted but remain in the plating wastewater, thereby allowing selective recovery of iron and zinc.

After the first extraction step as described above, the plating wastewater from which iron and zinc have been extracted is subjected to secondary extraction using 2-ethylhexyl hydrogen 2-ethylhexylphosphate. The concentration of extractant in the second extraction step is 20% by volume to 30% by volume as in the first extraction step. In the second extraction step, the extractant is used in a state where a saponification reaction with ammonia water is performed, and a degree of saponification is 10% to 14%. If the degree of saponification is less than 10%, the extraction rate of copper and nickel is low, and if the degree of saponification exceeds 14%, the extraction rate of copper and nickel does not increase even if the degree of saponification increases.

In the second extraction step, the plating ratio of the wastewater and the organic solution (A / O) are 1 to 3, similarly to the first extraction step, and the amount of the third phase inhibitor in the second extraction step is an extractant-containing organic solution. 4% by volume to 8% by volume, preferably 6% by volume, based on the total volume of. If the saponification degree of the extractant is 10% or more, the pH is increased to 4.5 or more, and when the amount of the third phase inhibitor is less than 4% by volume, a third phase is generated, making extraction difficult, and the amount of the third phase inhibitor added is 8% by volume. In the above, the extraction rate of copper is rather decreasing slightly.

In the second extraction step of saponifying and extracting the extractant, copper and nickel contained in the plating wastewater are extracted by 99% or more, and after the first and second extraction, almost all of iron, zinc, copper and nickel can be recovered. have. Therefore, when neutralizing the plating waste liquid from which metal components such as iron, zinc, copper, and nickel have been removed, there is an advantage in that the amount of sludge generated after neutralization as well as the amount of neutralizing agent is greatly reduced.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments of the present invention. However, the present invention is not limited only to the following examples.

<Example 1>

Plating wastewater is the wastewater flowing into the comprehensive treatment plant of the Korea Plating Corporation, the results of the component analysis is shown in Table 1 below. In Table 1, 95 ppm and 149 ppm of iron and zinc are contained, 122 ppm of copper, 130 ppm of nickel, and 25 ppm of chromium.

Component Content of Plating Wastewater (ppm) ingredient Fe Ni Cu Zn Cr ⁶⁺ CN Cl ^- SO ₄ ^2- NO ₃ ^- NH ₄ ⁺ F ^- Furtherance 95.2 130 122 149 <0.01 10.8 960 2900 790 150 108

Solvent extraction method while changing the addition amount of decanol at normal ratio (A / O) 2 using 20 volume% 2-ethylhexyl hydrogen 2-ethylhexyl phosphate and kerosene mixed solution which did not saponify the plating waste water mentioned above as an extractant. The metal was extracted by, and the results are shown in Table 2 below. At this time, the solvent extraction is carried out by mixing the test tube containing the plating waste water and the organic solution in a reciprocating stirrer for 1 hour, and then left to stand for about 30 minutes to perform phase separation of the plating waste water and the organic solution. Samples were analyzed for metal components such as iron, zinc, copper and nickel.

Extraction rate and concentration of each metal according to the amount of decanol added Decanol addition amount iron zinc Copper nickel Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) 0% by volume - - - - - - - - 2% by volume 90 171.4 92 274.2 0.6 1.5 0.4 1.0 4% by volume 89 169.5 91 271.2 0.53 1.3 0.4 1.0 6 vol% 90 171.4 85 253.3 0.61 1.5 0.38 0.99 8% by volume 90 171.4 80 238.4 0.58 1.4 0.38 0.99

As shown in Table 2, when decanol was not added, a third phase occurred during extraction, which made the extraction reaction difficult. In the case of adding decanol, the iron in the plating wastewater is extracted about 90%, and the extraction rate is almost constant regardless of the amount of decanol added, and the extractant-containing organic solution contains about 171 ppm of iron. On the other hand, zinc has a constant extraction rate of 91 to 92% at 4 vol% of decanol and a concentration of zinc of 274 ppm in the organic solution. The increase to 8% by volume reduced the extraction rate to 80%, resulting in a concentration of only 238 ppm of zinc in the organic solution.

On the other hand, since copper and nickel did not saponify the extractant, almost no extraction rate was extracted at about 0.6% and 0.4%, respectively, regardless of the increase in the amount of decanol, and the organic solution contained only 1.5 ppm and 1 ppm of copper and nickel, respectively. It contains.

<Example 2>

The extraction was carried out in the same manner as in Example 1, except that the concentration of 2-ethylhexyl hydrogen 2-ethylhexyl phosphate as an extractant was 25% by volume, and the amount of decanol added was 5% by volume, followed by solvent extraction. The metal was extracted and the results are shown in Table 3.

Extraction rate and concentration of each metal according to the degree of saponification Saponification degree (%) iron zinc Copper nickel Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) 0 99 188.5 99 292 0.6 1.5 0.4 One 4 99 188.5 100 298 30 73.2 14 36.4 8 100 190.4 100 298 85 207.4 61 158.6 10 100 190.4 100 298 96 234.2 95 247 14 100 190.4 100 298 99 241.6 99 257.4 16 100 190.4 100 298 99 241.6 99 257.4

As shown in Table 3, iron and zinc are almost all extracted from 0% of saponification degree to 99% of extraction rate, and thereafter, the extraction rate does not change even if the degree of saponification increases, and iron and zinc are present in the organic phase, respectively. About 190 ppm and about 298 ppm.

On the other hand, copper and nickel are hardly extracted at 0% of saponification degree of 0.6% and 0.4%, respectively. However, as saponification increases, the extraction rate of copper and nickel increases. This is increasing to 30% and 14%, respectively, and saponification is rapidly increasing to 96% and 95% at 10%. When the degree of saponification increased to 14%, the extraction rate of copper and nickel was 99%, and almost all of them were extracted. In the organic phase, copper and nickel contained about 242 ppm and 257 ppm, respectively, but the degree of saponification increased to 14% or more. There is no change in the extraction rates of copper and nickel.

Therefore, iron and zinc in the plating wastewater are first extracted without saponifying the extractant, and the residual wastewater is extracted by saponifying the extractant by about 10% to 14%, and most of the iron and zinc, copper and nickel are selectively separated and It can be seen that it can be recovered.

<Example 3>

The extraction was carried out in the same manner as in Example 2, except that the plating wastewater was first extracted while changing the normal ratio by adding 4% by volume of decanol without saponifying the extractant, and then the saponification degree of the extractant was 12%, followed by extraction. 6 vol% of decanol was added based on the total volume of the first organic solution, and the residual wastewater was extracted secondly while changing the normal ratio, and the results are shown in Table 4 below.

Extraction rate and concentration of each metal according to change of A / O Normal ratio (A / O) First Extraction (0% Soap) Second extraction (12% soap) iron zinc Copper nickel Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) Extraction rate (%) Concentration (ppm) 0.5 100 47.6 100 74.5 100 61 100 65 One 100 95.2 100 149 100 122 100 130 2 99 188.5 99 292 99 241.6 99 257.4 3 95 271.3 96 429.1 96 351.4 96 374.4 4 80 304.6 82 488.7 78 380.6 79 410.8

As shown in Table 4, in the first extraction step, when the ratio (A / O) is 0.5, the extraction rate of iron and zinc is 100%, but the concentration effect in the organic phase is reduced, and the concentration in the organic phase is very low, such as 47.6 ppm and 74.5 ppm, respectively. Appearing. On the contrary, the extraction ratio was about 99% even in the standing ratio 2, and almost all of the extracts were extracted. The concentration in the organic phase was also good due to the increase in the standing ratio, and the concentration in the organic phase was 188.5 ppm of iron and 292 ppm of zinc. In addition, as the ratio increased to 3, the extraction rate decreased slightly to 95% of iron and 96% of zinc, but the concentration in the organic phase was very high at 271.3 ppm and 429.1 ppm, respectively. However, when the standing ratio is increased to 4 or more, the extraction rate of iron and zinc is considerably reduced to 80% and 82%, and the concentration in the organic phase is about 304.6 ppm and 488.7 ppm.

Copper and nickel, on the other hand, have an extraction ratio of 100% at 0.5 (A / O), but the concentration in the organic phase is only 61 ppm and 65 ppm. When the ratio increased to 3, 96% of copper and nickel were extracted, and the concentration in the organic phase reached 351.4 ppm and 374.4 ppm, indicating a high concentration effect. However, when the ratio increased to 4 or more, the extraction ratio of copper and nickel was 78%. And 79%, which shows that the concentration in the organic phase is not as high as 380.6 ppm for copper and 410.8 ppm for nickel.

When the heavy metal is recovered from the plating wastewater by the solvent extraction method using the method of the present invention as described above, the selective separation and recovery of iron, zinc, copper and nickel as compared to the method of recovering the heavy metal from the conventional plating wastewater It is possible to recycle the waste resources, and provides an economical recovery method, as well as the process is easy and has a high recovery rate and enrichment effect of heavy metals. In particular, the amount of sludge produced when neutralizing and sedimenting the residual wastewater after heavy metal recovery can be greatly reduced, thereby reducing the sludge treatment cost and providing environmentally friendly effects to minimize environmental pollution.

Claims (6)

A method for recovering heavy metals such as iron, zinc, copper, and nickel in plating wastewater by using a solvent extraction method, wherein the 2-ethylhexyl hydrogen 2-ethylhexyl phosphate in an unsaponified state is used as a third phase inhibitor. A first extraction step of extracting and recovering iron and zinc from the plating wastewater using an organic solution mixed with an organic solvent together, and using an organic solution mixed with an organic solvent together with a third phase inhibitor in a saponified state of the extractant And a second extraction step of extracting and recovering copper and nickel from the plating wastewater from which iron and zinc have been extracted in the first extraction step. The method of claim 1 wherein the concentration of extractant in the first and second extraction steps is 20% to 30% by volume. The method of claim 1, wherein the saponification degree of the extractant in the second extraction step is 10% to 14%. The amount of the third phase inhibitor in the first extraction step is 2% to 4% by volume based on the total volume of the extractant-containing organic solution, and the amount of the third phase inhibitor in the second extraction step 4% by volume to 8% by volume, based on the total volume of the extractant-containing organic solution. The method according to claim 1, wherein the phase ratio (A / O) of the plating wastewater and the organic solution in the first extraction step and the second extraction step is 1 to 3. The method of claim 1 wherein the third phase inhibitor in the first and second extraction steps is decanol.