JPS6237716B2 - - Google Patents

Description

[Detailed description of the invention]

In the present invention, HCl and H ₂ SO ₄ containing a large proportion of Fe ions used for surface treatment of metals are treated,
The present invention relates to a metal surface treatment method that consists of oxidizing Fe ions or removing Fe ions in an aqueous solution and repeating the surface treatment process. Conventionally, HCl and H ₂ SO ₄ are commonly used in surface treatment processes for metal materials and metal products. Special materials such as stainless steel and titanium steel
A mixed acid of HNO ₃ and HF is used. If these acids contain a large amount of Fe ions, which are the main dissolved metal ions, the pickling effect will decrease and they will eventually be discarded, and the metal ions will be converted to hydroxide or oxidized by neutralization methods. There are methods to remove the metal ions from the system as sulfate and chloride crystals by evaporation and concentration, or to remove the metal ions from the system into a furnace kept at high temperature in the steel industry where large quantities are used. Methods such as injecting a large amount of waste acid and recovering metal oxides and acids have been adopted. All of these prior art technologies consume a large amount of energy and are no longer economical in these days of rapidly rising energy prices.Furthermore, their structure allows humid HCl gas to come into contact with high-temperature areas, which can lead to equipment corrosion. The drawback is that maintenance costs are significantly increased. In addition, methods that combine electrodialysis or diffusion dialysis have been announced as methods for regenerating pickling solutions using electrolytic methods, and both of these methods directly electrolyze the waste acid discharged during the metal surface treatment process. This method collects Fe ions as metallic iron, but since the concentration of H ⁺ ions in the aqueous solution is high and Fe ions are more base than H ⁺ ions, it is necessary to
Since H ⁺ ions are discharged and generated as H ₂ gas, the current efficiency is low and it is not economical. Also, Fe ²⁺ ions in the waste acid are oxidized to Fe ³⁺
Patent application No. 51-118516 as a method for converting into ions
There is a number. This is aimed at simply converting Fe ²⁺ ions into Fe ³⁺ ions to improve the pickling effect by increasing the oxidizing power, but ultimately if the Fe ions increase, the pickling power decreases. In either case, it cannot be used repeatedly for a long time unless the Fe ions in the aqueous solution are removed. As a result of various studies, the present inventors have overcome these drawbacks of the prior art and have completed the present invention. That is, the gist of the present invention is that H ₂ SO ₄ or
The HCl solution is introduced into the anode chamber of the diaphragm electrolytic cell, the valence of Fe ions in the solution is changed to improve the oxidizing power, and a part of the acid solution flowing out from the anode chamber is recycled to the surface treatment process. , and the other part is then sent to a solvent extraction step, where one or more extractants selected from the group consisting of alkyl phosphoric acids, phosphoric esters, oximes, or primary to quaternary amines are added to petroleum Fe in the effluent acid solution is removed by contacting with an organic solvent diluted with a hydrocarbon-based acid solution.
The ions are extracted into the organic phase and the acid solution free of Fe ions is recycled again to the metal surface treatment process, while the organic phase from which Fe ions are extracted is sent to the conversion process where it is treated in the presence or absence of a catalyst. After contacting with a gaseous reducing substance to facilitate stripping of Fe ions, water or a mineral or organic acid (e.g. HCl, H ₂ SO ₄ , HNO ₃ or sulfuric acid,
A metal surface treatment method characterized in that the organic solvent is regenerated by stripping off Fe ions by contacting with a stripping aqueous solution containing (Gysan), and the organic solvent is recycled to the extraction step again. The alkyl phosphoric acids used in the present invention are the compounds shown below.

【formula】

【formula】

【formula】

[expression] or

##STR1## where R is generally an alkyl group of 4 to 14 carbon atoms. Further, the phosphoric acid ester is represented by the following.

【formula】 【formula】

[Formula] Also teeth

[Formula] (wherein R is an alkyl group of 4 to 14 carbon atoms). Next, primary amines to quaternary amines are as follows, and an example of the extractant used in the test is shown for each type, but all are representative examples and similar amines can of course be used. can. Primary amine: represented by RN or _RNH2 , where R is 4
It is an alkyl group of ~18 carbon atoms. The following were used in the test: Secondary amine: _R2N or _R2NH , where R is an alkyl group of 4 to 18 carbon atoms. The following were used in the test: Tertiary amine: R ₃ N or R ₃ NH, where R is an alkyl group of 4 to 18 carbon atoms. The following were used in the test: Quaternary amine: Those used in the test are shown below. R represents an alkyl group having 6 to 18 carbon atoms, and an example is a Cl type, and this Cl is SO ₄ OH
A modified version of HSO ₃ , NO ₃ , etc. can also be used.

[expression] or

[Formula] Oxime is shown next, but similar oximes can of course be used.

[Formula] In addition to the oxime shown on the left, a mixture of two oximes such as SME-529 (trade name of Shell Chemical) or L-65N (trade name of General Mills Chemical) can also be used. Diluents that can be used in the present invention include aromatic hydrocarbons, aliphatic hydrocarbons, and mixtures of miscellaneous hydrocarbons such as kerosene. The concentration of these is determined by the properties of the liquid to be treated or the conditions in which it is recovered. Generally, the extractant concentration is 2
%~95% (volume). Next, the gaseous reducing substances used in the present invention include H ₂ , SO ₂ , CO or H ₂ S. In addition, when reducing using a reducing gas, a catalyst is used to accelerate the reaction, and as a catalyst, metal nickel, cobalt, nickel oxide, cobalt oxide, molybdenum oxide, etc. may be used alone or in combination. It can be used as Furthermore, activated carbon and metallic iron can also be used, and at the same time as the catalyst is used, the aforementioned reducing gas can be blown into the organic phase kept under pressure to convert Fe ions in the organic phase. In addition, the organic phase is passed through the cathode chamber of the electrolytic cell as dispersed droplets or retained in the upper part, and the Fe ³⁺ in the organic phase is converted to Fe ²⁺ by the H ₂ gas from the generator generated in the cathode chamber. It can be converted into ions. The present invention will be explained below with reference to the drawings. First, the processing method shown in FIG. 1 will be explained. H ₂ SO ₄ or HCl waste acid containing a large proportion of Fe ²⁺ ions discharged from the metal surface treatment process is sent to the anode chamber of the diaphragm electrolysis process, where Fe ²⁺ →Fe ³⁺
A portion of the waste acid discharged from the anode chamber with improved oxidizing power is recycled to the surface treatment process. In the metal surface treatment step, the surface of the metal is dissolved, so the Fe ³⁺ ions generated in the anode chamber change to Fe ²⁺ ions as the surface treatment progresses, as shown in the following equation. 2Fe ³⁺ +Fe3Fe ²⁺ Thus the total amount of iron ions (T·Fe ions) increases in the circulating acid (HCl·H ₂ SO ₄ ). The waste acid containing Fe ions in an amount approximately corresponding to the accumulated amount of Fe ions is led to the next extraction step, and as shown in the following equation, Fe ³⁺ ions in the waste acid are extracted from the above-mentioned extractant - petroleum hydrocarbon diluent. The waste acid of the raffinate is recycled to the metal surface treatment process as a circulating acid. Fe ³⁺ +3 (RO) ₂ POOHFe [(RO) ₂ POO] ₃ +
3H ⁺ Fe ³⁺ +3RHFeR ₃ +3H ⁺ or in the case of a chloride solution, it is extracted as a chloride complex as shown in the following formula. FeCl ₃ +HCl + 2TBPHFeCl ₄ 2TBP (TBP: tributyl phosphate)FeCl ₃ +HCl + R ₃ N
R ₃ NH ⁺・FeCl ₄ ^- Mixing the extractants of the group of alkyl phosphates and oximes, which can extract iron as Fe ³⁺ ions, and the group of phosphates and amines, which can extract it with the complex of FeCl ₄ ^- . However, by making the extraction amounts the same, the following extraction becomes possible. Fe ³⁺ +FeCl ₃ +HCl+2Org HFe ³⁺・FeCl ₄ ^-・Org+3H ⁺ (Org indicates an organic solvent containing an extractant) Recovered acid (contains virtually no Fe ions)
H ₂ SO ₄ .HCl) is recycled again to the metal surface treatment process. FIG. 5 shows an extraction equilibrium curve for extracting Fe ³⁺ ions from HCl, H ₂ SO ₄ and HNO ₃ solutions using an alkyl phosphoric acid (D2EHPA)-paraffin organic solvent. In the figure, the curve marked with ●―● is H ₂ SO ₄ 380g/
The acid solution, the curve marked △-△ is HNO ₃ 150g/
+HF20g/acid solution, the curve marked □-□
The equilibrium curve for extraction with alkyl phosphoric acid from a waste acid solution containing 150 g of HCl is shown. Also in Figure 3
When extracting iron in acid using D2EHPA-paraffin, an extraction (exfoliation) equilibrium curve showing the relationship between the extraction rate of Fe ³⁺ ions and Fe ²⁺ ions and PH is shown. Fe ³⁺ is extracted into the organic phase in the low PH region,
This shows that extraction from waste acid is advantageous compared to Fe ²⁺ . Figure 4 shows the relationship between HCl concentration (g/) and extraction rate when Fe ³⁺ ions and Fe ²⁺ ions are extracted as Fe/chloride complexes using an alkylamine such as trioctylamine (TOA). shows. Fe ³⁺
It can be seen that it is extracted more advantageously than Fe ²⁺ .
FIG. 6 shows an example of an extraction equilibrium curve of a Fe chloride complex using a phosphate ester [TBP (tributyl phosphate)] amine (TOA)-paraffin organic solvent. In the figure, the curve marked with 〓 shows an extraction equilibrium curve using an organic solvent containing phosphate ester (TBP), and the curve marked △-△ shows an extraction equilibrium curve using an organic solvent containing amine (TOP). On the other hand, Fe ³⁺ ions transferred to the organic phase have a PH of Figure 3.
As shown in the HCl concentration and extraction rate curve in Figure 4, since stripping is not possible (a good extraction rate indicates that stripping is difficult), in the organic phase Fe ³⁺ → Fe ² You need to convert it to ⁺ . HFeCl ₄・2TBP＋H ₂ OFeCl ₃ +HCl＋2TBP In this case, it can be removed with water, but the
If the concentration of FeClC+HCl increases, it will be extracted into the organic phase, so if it is transferred to the aqueous phase and converted from Fe ³⁺ to Fe ²⁺ , the Fe concentration in the stripping solution can be increased. The conversion from Fe ³⁺ to Fe ²⁺ can be performed by electrolysis as shown below (first
Figure, “conversion” process). Fe ³⁺・R ₃ +e ^- +3H ⁺ →3RH＋Fe ²⁺ H・Fe ³⁺・
FeCl ⁻ ₄・2Org＋2e ⁻ +2H ⁺ +H ₂ O→2FeCl ₂ +
2Org・3H ⁺ (Org indicates an organic solvent consisting of an extractant/diluent) Alternatively, the organic phase containing Fe ³⁺ is brought into contact with the aforementioned gaseous reducing substance to convert Fe ³⁺ to Fe ²⁺ Let me,
By contacting with a stripping solution (S in Figure 1), for example, water or an aqueous solution containing mineral acid or organic acid, Fe ions are stripped from the organic solvent (the "stripping" step in Figure 1) and the organic solvent is regenerated; Recirculate to extraction process. The stripping solution with increased Fe ion concentration is led to the cathode chamber of the diaphragm electrolysis process, where Fe ²⁺ →
Precipitate and recover as Fe (“metallic iron” in Figure 1)
Then, the liberated Cl ^- ions and SO ₄ ^2- ions are transferred as anions to an anode chamber separated by a diaphragm and recovered. Figure 7 shows the Fe peeling equilibrium curve.
The peeling equilibrium curve using a stripping solution, the curve marked with ▲-▲, is the peeling curve with 50 g/H ₂ SO ₄ after contact with a gaseous reducing substance. From FIG. 7, it can be seen that after reduction from Fe ³⁺ to Fe ²⁺ by contact with a gaseous reducing substance, most of the Fe is stripped from the organic phase into the stripping solution. Furthermore, according to FIG. 3, it is seen that Fe ²⁺ ions can be removed using an aqueous solution with a pH of 3 or lower. Moreover, FIG. 8 shows the peeling equilibrium curve of the Fe chloride complex. In the figure, the curve marked with x--x is a peeling equilibrium curve using water, and the curve marked with ▲-▲ is a peeling equilibrium curve using a reducing solution. According to Figure 4, it is difficult to remove Fe ³⁺ by using an HCl remover for Fe ³⁺ /Fe ²⁺ chloride complexes, and it is more advantageous to remove Fe ²⁺ , and the lower the HCl concentration, the more Fe Shows that it is advantageous for ²⁺ peeling. In the example shown in the flow sheet of Figure 2, the electrolytic cell that oxidizes the Fe ²⁺ ion-containing acid solution from the metal surface treatment process consists of a three-chamber diaphragm electrolytic cell, and the stripping solution after contact with the organic solvent is introduced into the cathode chamber. However, this procedure differs from the operation shown in Figure 1 in that the anions in the stripping solution only enter the intermediate chamber and do not migrate to the anode chamber, and therefore do not enter the metal surface treatment circulating acid. This figure shows an operation similar to that in Figure 1. In the method of the present invention, as shown in FIGS. 1 and 2, waste acid from the metal surface treatment process or Fe-containing acid solution from other treatments is converted from Fe ²⁺ →Fe ³⁺ in the anode chamber of the diaphragm electrolytic cell. It is essential to oxidize and it is essential to recirculate the Fe ³⁺ -containing waste acid to the metal surface treatment process as a circulating acid. As shown in Figure 9, the curve marked with △...△ (Fe ²⁺ 102.45g/T.Cl ^- 201.81g/) is different from the curve marked with ●-● (Fe ³⁺ 61.58g/.
This shows that the pickling effect (pickling temperature 25-30°C) is low despite the high concentration of hydrochloric acid represented by T·Cl ^{- ( 153.89} g/). In other words
This shows that the presence of Fe ³⁺ has a significant effect on accelerating pickling (the sample loss after 60 minutes in the Fe ²⁺ pickling curve is 0.3%). Example 1 From the group of alkyl phosphates D2EHPA (di-2 ethylhexyl phosphoric acid) was selected and added to the organic phase by contacting the organic solvent diluted with kerosene to 50% concentration with 60 g of Fe ³⁺ ions/containing H ₂ SO ₄ 18.6
The organic solvent after extracting g/g of Fe and regenerating H ₂ SO ₄ was used for the test. See FIG. 5 for the extraction equilibrium curve. Peeling test: When the organic solvent (O) was shaken and peeled with the following stripping agent aqueous solution (A) and O/A = 1 (volume) for 10 minutes, the measured value of Fe concentration in the above aqueous solution (aqueous phase) was calculated. Shown below.

[Table] Next, the same organic phase as above was contacted with _H2 gas in the presence of metal nickel, and then shaken and peeled with the following stripping agent aqueous solution at O/A = 1 for 10 minutes. The measured values of Fe concentration in the liquid were as follows:

[Table] Example 2 Waste acid was Fe ²⁺ 60g/used for surface treatment of wire rod.
, waste acid containing 182 g/T・HCl was added to the first
As shown in the flow sheet in the figure, it was introduced into the anode chamber of the diaphragm electrolysis process to oxidize Fe ²⁺ ions. It was converted to Fe ³⁺ ions with an oxidation efficiency of approximately 100% at the anode. At the same time, because Cl ^- ions moved through the diaphragm, the T·HCl concentration changed to 215 g/. The anodized waste acid was then selected as extractants D2EHPA from the group of alkyl phosphoric acids and TBP (tributyl phosphate) from the group of phosphoric acid esters, each at 30% in n-paraffin (diluent).
and an organic solvent prepared to have a concentration of 20%, in a countercurrent ratio of O/A = 3/1 (O...organic phase, A...aqueous phase, i.e., waste acid in this case). Extraction was performed using In the exit organic phase
The Fe ³⁺ ion concentration is 18.6 g/Fe ³⁺ in the outlet aqueous phase.
The ion concentration decreased to 4.2g/, and the T・Cl ^- concentration decreased to
It decreased to 110g/. Next, the organic solvent is poured into the cathode chamber of the electrolytic cell by 1 to 2 mm.
The electrolytic stripping solution forms a continuous phase, and the composition of this aqueous phase is Fe ²⁺ 100g/
, T.Cl ^- 138 g/, NH ₄ Cl 20 g/ and thiourea 5 g/residual water are stirred so that the H ₂ gas generated at the cathode comes into contact with the droplets of the organic phase. Thus, with O/A=1 and cathode chamber temperature of 38°C, the aqueous phase outlet Fe concentration is 126.4 g/Fe at the first stage outlet, 151.4 g/Fe concentration at the second stage outlet, and 151.4 g/Fe concentration at the third stage outlet.
The Fe concentration was 158.1g/, and at the fourth stage exit 158.9g/, almost complete peeling was possible. The T·Cl ^- concentration of the stripping solution was also 210 g/, indicating that Cl/Fe was transferred from the organic phase to the stripping solution at a ratio of about 2. Example 3 Fe ²⁺ 120g/, used for metal surface treatment
T.Cl ^- 210g/waste acid was used. First, this waste acid was introduced into the anode chamber of the diaphragm electrolytic cell and subjected to electrolytic oxidation as shown in the flow sheet of FIG. The current efficiency was almost 100%, and Fe ²⁺ ions were changed to Fe ³⁺ ions. Since a cation selectively permeable membrane was used as the anode chamber diaphragm, the Cl ^- concentration at the aqueous phase outlet (anode chamber effluent) was not measured, assuming that there was no change. From the group of alkyl phosphates for the extraction of Fe ³⁺ ions
D2EHPA (di-ethylhexyl phosphate), TOA (trioctylamine) from the group of alkyl amines
A mixed organic solvent was used, which was prepared by diluting with an aromatic hydrocarbon to give a concentration of 45% and 5%, respectively. The extraction test was carried out by countercurrent contact at an O/A ratio of 6/1, and the Fe concentration in the organic phase at the outlet was measured to be 19.6 g/Fe. Fe at water phase outlet
Concentration is Fe ³⁺ 2.4g/, T.Cl ^- concentration is 198.5g/
It was hot. Peeling test: When the obtained organic solvent was directly peeled with water (O/A = 1), the Fe concentration in the aqueous phase after shaking for 10 minutes was
It was 1.2g/. (Comparative Example) The Fe concentration of the aqueous phase after shaking for 10 minutes at O/A=1 with a stripping solution of 100 g/HCl was 2.1 g/. (Comparative Example) The Fe concentration of the aqueous phase after shaking for 10 minutes with HCl 200 g/stripping solution O/A=1 was 11.2 g/HCl. (Comparative Example) The equilibrium (peeling) curve shown in FIG. 6 shows the peeling situation when Fe ³⁺ ions are not converted to Fe ²⁺ ions. Next, the case where an organic solvent is brought into contact with a reducing substance will be described below. After passing _H2S gas through the organic solvent phase for 10 min,
Fe ²⁺ 72g/, T・Cl ^- 120g/, NH ₄ Cl53g/
, N ₂ H ₄ 5g/ catholytic circulating fluid (aqueous phase) and O/
The Fe ²⁺ concentration of the aqueous phase after contact at the ratio A=1 was 91 g/, and the T.Cl ⁻ concentration changed to 125 g/. Electrolysis experiment example 1 Fe110g/, T・SO ₄ ^2-200g /,
(NH ₄ ) ₂ SO ₄ 80g/PH1.8 solution is passed through the cathode chamber,
Electrolysis was carried out at a current density of 5 amperes/dm ² . The cathode chamber contains acid (containing Fe ²⁺ ions) used in the metal surface treatment process.
is circulated, and the intermediate chamber contains the Fe100 that has left the cathode chamber.
g/, T・SO ₄ ^2- 180g/, (NH ₄ ) ₂ SO ₄ 80
When the liquid was circulated, 220g/ of T・SO ₄ was
Fe21gr was precipitated in the cathode chamber (current efficiency 91%), and the efficiency of the anode was 100%. Electrolysis experiment example 2 Fe ²⁺ 100g/, T・Cl ^- 130g/ in the cathode chamber
, NH ₄ Cl 53 g/, N ₂ H ₄ 2 g/ are circulated, and the anode chamber contains Fe ²⁺ 120 g/, T・Cl ^- 210 g/
The liquid was circulated. A cation-selective permeable membrane (manufactured by DuPont, trade name: Nafion) was used as the diaphragm separating both chambers. The current density was 5 amperes/dm ² , the distance between electrodes was 150 mm, and the electrolytic voltage was 3.8 volts. During continuous electrolysis, the conversion efficiency of the anode chamber outlet liquid from Fe ²⁺ to Fe ³⁺ was 100%, with Fe ²⁺ 6.2 g/,
Fe ³⁺ is 113.8g/, T・Cl ^- 242g/, and the cathode chamber outlet liquid is Fe74g/, T・Cl ^- 98.8g/,
NH ₄ Cl53g/(however, twice as much of the cathode-passing liquid as the anode chamber-passing liquid was passed through the anode chamber-passing liquid).
The current efficiency at the cathode was 93%. Further, when the present invention is implemented, there are the following advantages. (1) In the hydrometallurgical process in the non-ferrous metallurgy industry,
The solvent extraction method can be used in the separation process of Fe ions and is also economical, so in addition to removing conventional Fe ions, the loss of coexisting valuable metals is reduced, making it highly economical. (2) In addition to valuable metals, unused resources such as leaching residue, slag, tailings, or silicate ore, which contain relatively large amounts of Fe, can be leached out using strong acids, making it possible to treat solid industrial waste. By doing so, it becomes possible to obtain valuable metals and electrolytic iron economically. (3) Waste acids (mineral acids or organic acids) used for surface treatment of metal products and materials can be economically recovered, creating a closed circuit, making it possible to prevent pollution and recover resources. , (4) Waste disposal using the conventional thermal decomposition method
Compared to HCl recovery, it uses less energy and is more economical; since it operates at room temperature, it is easy to select corrosion-resistant materials; and because it is a simple device, it is possible to manufacture a device with low maintenance costs. 5) It is possible to manufacture both large and small devices, and the range of available factories is wide because expansion is possible. (6) Compared to the neutralization method, there is no generation of sludge, so there is no need for disposal costs, and
Since high-purity electrolytic iron is recovered, there is no need to consider sludge treatment in the location conditions of the equipment.

[Brief explanation of the drawing]

Figures 1 and 2 are flow sheets for implementing the method of the present invention, Figure 3 is a diagram showing the relationship between the extraction rate of Fe ³⁺ ions and Fe ²⁺ by D2EHPA-paraffin organic solvent and PH; Figure 4 shows the extraction rate of Fe chloride complex by TOA-paraffin organic solvent.
Figure 5 shows the relationship with HCl concentration (g/).
Fe ³⁺ extraction equilibrium curve with D2EHPA-paraffin organic solvent. FIG. 6 is a diagram showing the extraction equilibrium curve of Fe/chloride complex with TOA-n-paraffin and TBP-n-paraffin. FIG. 7 is a Fe stripping equilibrium curve, FIG. 8 is a stripping equilibrium curve of Fe chloride complex, and FIG. 9 is a diagram showing the Fe ³⁺ pickling effect.

Claims (1)

[Claims] 1. After introducing the H ₂ SO ₄ or HCl solution containing a large proportion of Fe ions used for metal surface treatment into the anode chamber of the diaphragm electrolytic cell and converting the valence of Fe ions in the solution. , a part of it is circulated to the metal surface treatment process, and another part of the acid solution flowing out from the anode chamber is recycled to the alkyl phosphoric acid group, phosphoric ester group, oxime group, or primary to primary in the next extraction process. Fe in the waste acid is removed by contacting an organic solvent prepared by diluting one or more extractants selected from the group consisting of quaternary amines with a petroleum hydrocarbon.
The ions are extracted and the waste acid is regenerated and recycled again to the metal surface treatment process, while the organic phase from which the Fe ions have been extracted is contacted with a gaseous reducing substance in the presence or absence of a catalyst and then treated with water or mineral acid. Alternatively, a method for surface treatment of metal, which comprises stripping Fe into the stripping solution by contacting it with a stripping solution containing an organic acid or by electrolytic reduction, and regenerating the organic solvent. 2 The organic phase from which Fe ions have been extracted is passed through the cathode chamber of the electrolytic process to convert the valence of Fe ions in the organic phase, and
The method according to claim 1, which strips off Fe ions. 3. The method according to claim 1, wherein the organic phase from which Fe ions have been extracted is brought into contact with a reducing gas in the presence of a catalyst to convert the valence of Fe ions in the organic phase.