LU503622B1 - Method for extracting and recovering mixed acid from chemical polishing solution by tributyl phosphate - Google Patents

Abstract

The invention relates to a method for extracting and recovering mixed acid in chemical polishing solution by tributyl phosphate, belonging the technical field of waste acid recovery in chemical polishing solution. The method comprises: S1, adding an organic phase into the chemical polishing solution for extraction to obtain a loaded organic phase and an extracted raffinate phase of the mixed acid; S2, washing the loaded organic phase with dilute acid to obtain a back-extraction dilute acid; S3, contacting the back extraction dilute acid with water for stripping to obtain mixed dilute acid solution, wherein the organic phase is a mixture of sulfonated kerosene and tributyl phosphate with a volume ratio of 1:4. In the invention, tributyl phosphate/sulfonated kerosene is used as an extraction system, and a method of 'extraction+stripping+concentration' is adopted to efficiently extract mixed acid from chemical throwing liquid. The method is simple, the extraction efficiency is high.

Description

DESCRIPTION LU503622

METHOD FOR EXTRACTING AND RECOVERING MIXED ACID FROM

CHEMICAL POLISHING SOLUTION BY TRIBUTYL PHOSPHATE

TECHNICAL FIELD

The invention relates to the technical field of waste acid recovery in chemical polishing solution, in particular to a method for extracting and recovering mixed acid in chemical polishing solution by tributyl phosphate.

BACKGROUND

In order to improve the surface smoothness, brightness and decorative effect of aluminum products, it is necessary to carry out surface finishing treatment. Polishing is an important means to obtain a bright mirror. Among them, because chemical polishing does not need power supply, and the equipment is simple, efficient, low-cost, and not limited by the shape and size of the parts, the quality requirements of aluminum products with no special requirements for finish can be fully met by chemical polishing.

Chemical polishing is a method of eliminating wear marks and leveling by selective dissolution of uneven areas on the surface of samples by chemical etching of chemical reagents. The chemical waste liquid contains a lot of waste acid and various metal impurities, which is hazardous waste, causing environmental pollution and waste of resources. Therefore, it is of great significance to find an efficient method to recycle waste acid, which is of great significance to environmental protection and resource recycling.

At present, there are a lot of methods to try to extract and recover waste acid from chemical polishing solution with different extractants, but it is still necessary to find the best extractant and process to improve the recovery and utilization rate of waste acid.

SUMMARY LU503622

Based on the above contents, the present invention provides a method for extracting and recovering mixed acid from chemical polishing liquid by tributyl phosphate, which uses tributyl phosphate/sulfonated kerosene as an extraction system and adopts the method of "extraction+stripping+concentration" to extract mixed acid from chemical polishing liquid efficiently.

In order to achieve the above objectives, the present invention provides the following scheme:

The present invention provides a method for extracting and recovering mixed acid from chemical polishing solution by tributyl phosphate, comprising:

S1, adding an organic phase into the chemical polishing solution for extraction to obtain a loaded organic phase and an extracted raffinate phase of the mixed acid;

S2, washing the loaded organic phase with dilute acid to obtain a back-extraction dilute acid;

S3, contacting the back extraction dilute acid with water for stripping to obtain mixed dilute acid solution, wherein the organic phase is a mixture of sulfonated kerosene and tributyl phosphate with a volume ratio of 1:4.

The chemical polishing liquid is filtered before extraction, and the filtered liquid is extracted.

Further, in S1, the ratio of the chemical polishing solution to the organic phase is 4:1.

Further, in S1, the extraction temperature is 28°C.

Further, in S1, the extraction is a three-stage countercurrent extraction.

Further, in S1, the concentration of the mixed acid in the loaded organic phase is 0.08-0.10 g/ml.

Further, in S2, the ratio of the loaded organic phase to the diluted acid is 10-15:1.

Further, in S3, the ratio of the stripped dilute acid to water is 1:3-4.

Further, in S3, the back extraction is 3-4 stages.

Further, in S3, the temperature of the back extraction is 65-70°C. LU503622

The technical principle of that invention is as follow:

Tributyl phosphate is a neutral phosphorus-containing extractant, which can extract acid through the coordination of oxygen atoms with P=O bonds with protons or the formation of hydrogen bonds. It has stable chemical properties, high viscosity, strong acid resistance, strong alkali resistance and strong oxidant resistance, and good extraction effect. Because of its high viscosity, diluents are often added to form a composite extractant to extract mixed acids. Sulfonated kerosene is an inert solvent with high fluidity, which can fully adjust the physical properties of extractant, such as viscosity, density, interfacial tension, etc., so that the two phases can fully contact and transfer mass during extraction and separate quickly after extraction. Based on the TBP/ sulfonated kerosene system, the invention studies the extraction effect of the

TBP/sulfonated kerosene system on the waste acid in the chemical polishing solution, investigates the influence of various factors on the extraction behavior, and efficiently extracts the mixed acid from the aluminum alloy chemical polishing solution.

The invention discloses the following technical effects:

In the invention, tributyl phosphate/sulfonated kerosene is used as an extraction system, and a method of extraction+stripping+concentration' is adopted to efficiently extract mixed acid from chemical throwing liquid. The method is simple, the extraction efficiency is high, and it is suitable for wide popularization and application.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows the changes of extraction rate and precipitation rate under different ratios in Example 1;

Fig. 2 shows the change of extraction rate under different effective acid concentrations in Example 1;

Fig. 3 shows the extraction rate of Example 1 in different phases;

Fig. 4 is a trend diagram of the change of the lower washing liquid after washing with dilute acid in different phases in Example 1;

Fig. 5 is a trend diagram of the change of dilute acid loaded with reverse extractidrJ503622 after washing with different dilute acids in Example 1;

Fig. 6 shows the extraction rate of mixed acid and the opposite extraction rate of load at different temperatures in Example 1;

Fig. 7 is a schematic diagram of the final fractional extraction.

DESCRIPTION OF THE INVENTION

A number of exemplary embodiments of the present invention will now be described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention.

Unless otherwise specified, the raw materials used in the embodiment of the present invention can be obtained from the purchase route.

Example 1

S1, collecting: filtering the aluminized polishing liquid in the polishing tank in a polishing waste liquid collecting tank to obtain chemical polishing wastewater;

S2, extraction: prepare tributyl phosphate (TBP) and sulfonated kerosene into an organic phase according to a certain volume ratio, accurately transfer the solution to be extracted (chemical polishing wastewater) with a pipette, put it into a pear-shaped separating funnel, and add the organic phase for extraction; after the mixed solution is diluted by a certain multiple, use inductively coupled plasma emission spectrometer (ICP-OES) to determine the concentration of AI**, and extract the mixed acid in the chemical polishing wastewater into the organic phase extraction solvent to obtain the loaded organic phase and the raffinate phase from which the mixed acid is extracted;

S3, washing: washing the loaded organic phase with dilute acid, and obtaining the stripping dilute acid after washing;

S4, back extraction: the supported phase used for stripping is extracted from the original acid under the conditions of 4:1, 28°C and sulfonated kerosene /TBP 1:4; contact the supported organic phase with pure water for stripping, so that the mixed acid can be stripped from the supported organic phase, and then enter the pure water tdJ503622 obtain the mixed dilute acid solution;

S5, carry out acid-base neutralization titration experiment with basic burette to determine the initial acid concentration and the effective acid concentration after extraction, so as to characterize the extraction effect, by supplementing sulfuric acid and phosphoric acid, adjust the ratio of sulfuric acid and phosphoric acid back to the available range of chemical polishing solution.

On the basis of Example 1, research is conducted: 1. Effects of different extractant ratios on the extraction process.

Using sulfonated kerosene as diluent, TBP extractant is diluted and extracted, and the extraction result is shown in Fig. 1. When the ratio is 4:1, the temperature is 28°C and the dilution ratio is 10%, the extraction rate of mixed acid is 74.57% and the aluminum ion is 55.17%. With the increase of dilution ratio, the extraction rate of mixed acid and aluminum ion decreased, and the extraction rate of mixed acid decreased more obviously and tended to decrease linearly. At the same time, with the increase of dilution ratio, the liquid precipitated from the loaded phase after extraction gradually increased, and the increasing trend is almost linear and proportional. Regression analysis showed that the slope of the regression curve is 0.98, which is close to 1, and the volume of the organic phase generally expanded by 5-10% after extraction, indicating that almost all the added diluents were precipitated after extraction.

However, the experiment shows that there is no solvent precipitation when the diluent is added to 10%. To investigate the dispersion of data points, the correct expression should be: when the data point is closer to the regression curve, the increased diluent corresponding to the data point is almost completely precipitated (incremental precipitation). As can be seen from Fig. 1, when the dilution ratio is more than 40%, the linear fitting of the data point is high, which means that the diluent added on the basis of 40% will be almost completely precipitated. On the contrary, when the dilution ratio is less than 40%, especially less than 25%, the added diluent can really dilute and will not be precipitated in the extraction process. Therefore, the proportion of sulfonated kerosene diluting TBP should not be too low or too high.

2. Effects of different concentrations of raw acid on the extraction process. LU503622

Fig. 2 shows the relationship between the extraction rate of mixed acid and the effective acid concentration in the original acid when the ratio is 4:1 and the temperature is 28°C. With the decrease of effective acid concentration (the increase of dilution ratio), the extraction rate of effective acid also decreases, and the extraction rate is almost linear with the effective acid concentration in the original acid, that is, y = -2.42533x+1.44874, r? is 0.99226, and the linear regression is good.

Similarly, with the decrease of effective acid concentration and aluminum ion content in raw acid, the extraction rate of aluminum ion fluctuates up and down, and the extraction rate of aluminum ion hardly changes with the decrease of effective acid and aluminum ion content, and it is stable at about 10%, mainly because the aluminum ion content is too low. The different trend of extraction rate between them also shows that with the decrease of concentration, the extraction selectivity also decreases, that is, high concentration is beneficial to the selectivity of phosphoric acid to aluminum ions. 3. Effects of different phases on the extraction process

As shown in Table 1, the density of sulfonated kerosene is 0.7526 g mL”.

Experimental determination: the density of the liquid separated from the upper layer is close to that of kerosene no matter how it changes. When the ratio is 4:1, the density of the liquid in the upper layer is 0.7709 g mL”. Therefore, it is speculated that the precipitated liquid is a mixed organic solvent mainly composed of kerosene, that is, the supernatant is kerosene doped with a small amount of TBP and mixed acid.

As shown in Fig. 3, when the ratio of TBP to sulfonated, kerosene is 4:1 and the temperature is 28°C, the liquid precipitation rate in the figure is the percentage of the volume of the precipitated liquid after extraction to the volume of the organic phase after extraction. When the ratio is 5:1, the extraction rate reaches 75%, and when the ratio is 4:1, the extraction rate is more than 70%. With the decrease of the ratio, the extraction rate of effective mixed acids decreased gradually, and the extraction rate of aluminum ions decreased slightly from 15% to 3%. At the same time, with the decrease of extraction phase ratio, the liquid precipitation rate increases continuously, and the growth curve is almost linear, which may be because the lower the phase ratio, the less the amount of organic solvent, the more effective acid is loaded per unit of organi¢J503622 solvent, that is, the higher the concentration of effective acid in the loaded phase, so the increase of mixed acid in the loaded phase will crowd out some sulfonated kerosene from the original system.

Table 1 Density of Precipitated Supernatant in Different Comparisons gm 0.7526 0.7709 0.7558 0.7307 4. Theoretical series of mixed acid extraction

According to the obtained extraction equilibrium curve, the theoretical order required for 80% extraction rate is 3. Take the slope of 4:1 as a parallel line, and make the parallel line tangent to the equilibrium curve. This parallel line is the theoretical maximum extraction rate of 4:1 compared with countercurrent extraction. By calculating this equilibrium line equation, the maximum extraction rate can be 87.2%.

The theoretical series can be obtained by drawing steps, that is, the minimum theoretical series of countercurrent extraction required to achieve the target effective acid extraction rate. The calculation results are shown in Table 2. It can be seen that the extraction rate can reach at least 65% in the first stage, 76% in the second stage, 80% in the third stage and 85% in the sixth stage, that is, in the process of approaching the theoretical maximum extraction rate, the required theoretical stages increase sharply, from 85% to 87.2%, and the theoretical stages increase to infinity. Therefore, the more extraction stages, the better, and the relationship between extraction rate and extraction stages is not linear, so the extraction stages should be considered comprehensively according to the aspects of cost and operability. Therefore, from the economic point of view, it is suggested to choose the extraction rate of 80% with three theoretical stages, but considering that the efficiency of centrifugal extractor stage can not reach 100%, it is expected that it will take 4~5 stages to reach the extraction rate of 80%.

If the ratio is too large, the amount of solvent will increase and the concentration 6503622 product will decrease, whereas if the ratio is too small, the extraction rate will be too low, and the selection of appropriate ratio plays an important role. Therefore, we still need to investigate the minimum theoretical stages required for different phases when the extraction rate reaches 80%. The results are shown in Table 3.

As shown in Table 3, if only one-stage extraction reaches the target extraction rate of 80%, the solvent consumption is very large compared with 38.4:1; the comparison of 6:1 requires two theoretical stages, the comparison of 4:1 and 5:1 requires three theoretical stages, the comparison of 3:1 requires four theoretical stages, and the comparison of 2:1 requires seven theoretical stages. Up to the ratio of 1.6:1, an infinite number of theoretical stages are needed. Therefore, compared with 4:1 and 3-stage countercurrent extraction, it is more suitable.

Table 2 Minimum extraction rate under different stages

Theoretical co 6 3 2 1 series

Extraction 87.2% 85% 80% 76% 64% rate

Table 3 Theoretical stages required to achieve 80% extraction rate in different comparisons

Extraction 1.6:1 2:1 3:1 4:1 5:1 6:1 38.41 rate

Theoretical oo 7 4 3 3 2 1 series

5. Experimental results of dilute acid washing LU503622

Compared with dilute acid, the loaded organic phase is 30:1, 20:1, 15:1 and 10:1, respectively. See Figure 4 for the composition changes of the lower washing liquid (dilute acid) after washing. As shown in Fig. 4, the color of the curve corresponds to the coordinate axis of the corresponding color. With the decrease of the washing process, the density and aluminum ion content also decrease, mainly because the volume of the water phase (dilute acid) becomes larger and the substance is diluted. The content of total acid remained basically unchanged, but it was still about 5% higher than that of unwashed dilute acid, indicating that the two-phase total acid should have reached the extraction equilibrium at this time. The effective acid is increasing, mainly because the content of aluminum ion is decreasing sharply, while the total acid is basically unchanged, and the effective acid should be increasing.

After washing, stripping was carried out with different phase ratios of 4:1, and the composition changes of the lower washing liquid (dilute acid) after washing are shown in

Fig. 5. As shown in Fig. 5, the color of the curve corresponds to the coordinate axis of the corresponding color. With the decrease of the washing process, the aluminum ion content is decreasing, from unwashed 1070mg/mL to 30:1 594 mg/mL, and then to 10:1 170 mg/mL, which shows that dilute acid washing can effectively remove aluminum ions in the loaded phase. The density is increasing, but it should also be noted that the density varies from 1.164 mg/ml to 1.168 mg/ml. Within the allowable range of error, it can be considered that the density has hardly changed. Both total acid and effective acid are decreasing, but the distance between total acid and effective acid is decreasing, which is mainly due to the decrease of aluminum ion content. In addition, considering that the change of acid is only within 1% (unwashed effective acid is 24.97%), it can be considered that washing with dilute acid does not significantly reduce the purity of stripped dilute acid. Therefore, dilute acid washing has a good effect of removing aluminum ion content without affecting the stripping purity (within 1%), and has a good removal stability and operational space. It is suggested that the ratio of dilute acid washing is 10-15:1.

6. Influence of different concentrations of loaded phase on stripping process. LU503622

With the decrease of mixed acid concentration in the loaded phase, the stripping rate is continuously improved, which means that the less mixed acid in the loaded phase, the higher the stripping rate. When the concentration of mixed acid is 0.02g/ml, the stripping rate reaches 87.03%. However, with the decrease of mixed acid concentration and the increase of stripping rate, the concentration of stripped dilute acid decreased continuously. When the mixed acid concentration was 0.02g/ml, the concentration of stripped dilute acid was only 5.68wt%. Because the final product is concentrated acid, dilute acid with too small concentration will increase the cost of concentration. Therefore, the initial mixed acid concentration in the loaded phase should not be too high, otherwise the stripping rate is low; the concentration should not be too low, otherwise the concentration of dilute acid obtained is low, which will increase the concentration cost; considering comprehensively, the concentration of dilute acid in the outlet stripping is preferably above 20%, and the initial mixed acid concentration in the loaded phase is 0.08-0.10 g/mL. 7. Influence of different phases on stripping process.

When the ratio is 1:1, the maximum stripping rate of mixed acid is 86.38%, while when the ratio is 5:1, the maximum concentration of mixed acid is 31.22 wt%. It can be seen that, contrary to the extraction results, with the decrease of the ratio, the stripping rate of mixed acid gradually increases, that is, the more water phase is beneficial to stripping, but at the same time the concentration of mixed acid obtained after stripping also decreases rapidly. Considering comprehensively, the concentration of dilute acid in export stripping should be above 20%, and it is suggested that the stripping ratio should be 3:1-4:1.

8. Theoretical Series of Mixed Acid Stripping LU503622

Because the distribution ratio is not constant, it is too complicated to obtain the series by analytical method, so the theoretical series is obtained by drawing method according to the stripping operation curve and stripping equilibrium curve, and the results are shown in Table 4.

As shown in Table 4, in the stripping process, the stripping rate of the first stripping is 68%, the second stripping is 87%, the third stripping is 95%, and the fourth stripping is 99%. Therefore, it is only one-stage stripping, and the stripping effect is not ideal. It is recommended to carry out two or three-stage stripping. Considering the efficiency of the two-stage stripping, the rate of the second-stage stripping should be at least 80%, and the third-stage stripping should be at least 90%.

Table 4 theoretical stripping rate of different series

Series 1 2 3 4 oo

Back extraction 68% 87% 95% 99% 100% rate 9. Effects of Different Temperatures on Extraction and Stripping

As shown in Fig. 6, the extraction rate of effective acid and extraction solvent at different temperatures gradually decreases with the increase of temperature. When the temperature is 30°C close to room temperature, the extraction rate of effective acid is 82.28%, and when the temperature rises to 70°C, the extraction rate of effective acid is only 67.88%.

Compared with 4:1, when the ratio of TBP to sulfonated kerosene is 4:1, the solvent precipitation rate decreases with the increase of temperature, and when the temperature rises from 30°C to 70°C, the precipitation volume ratio also decreases from 7.9 to 3.5, that is, the precipitation rate is very small. The reasons why the precipitation rate gradually decreases with the increase of temperature are: firstly, the solubility of sulfonated kerosene in TBP/ mixed acid system increases with the increase of temperature; secondly, with the increase of temperature, the extraction rate of mixdd)503622 acid decreases, the mixed acid entering the loaded phase decreases, and the sulfonated kerosene "squeezed out" decreases accordingly.

The influence of different temperatures on the stripping process is shown in Figure 6.

With the increase of temperature, the stripping rate of the extraction process gradually increases. When the temperature is close to room temperature at 30°C, the stripping rate of the effective acid is 67.57%, and when the temperature rises to 70°C, the stripping rate of the effective acid reaches 81.03%. In the stripping process, the stripping rate increases with the increase of temperature, so increasing temperature is beneficial to stripping.

It is generally believed that the change of reaction heat during extraction and stripping is mainly caused by the formation and dissociation of hydrogen bonds.

Generally speaking, hydrogen bonds with bond energy <25 kJ/mol belong to weak hydrogen bonds, those with bond energy of 25-40 kJ/mol belong to medium strength hydrogen bonds, and those with bond energy >40 kJ/mol belong to strong hydrogen bonds. Therefore, weak hydrogen bonds are formed in the process of extraction and stripping. 10. Experimental simulation of extraction-washing-stripping combined process.

According to the above research, the theoretical optimum fractionation extraction conditions and combinations can be given, as shown in Fig. 7. Extraction process: 20-30°C, 80 vol.% TBP, compared with 4:1, three-stage countercurrent extraction (actual production may need 4-5 stages); washing process: 20-30°C, compared with 10-15:1, one-stage countercurrent extraction; stripping process: 50-70°C, compared with 4:1, two-stage countercurrent extraction. In which part of the stripped dilute acid is used as a detergent and finally extracted together with the original acid, instead of washing the partially stripped dilute acid separately. In the whole process, it is estimated that the extraction rate of mixed acid in raw acid can reach 80 wt%.

As shown in Fig. 7, the whole process can be divided into three "flows": solvent circulation flow, raw acid circulation flow and product flow. Circulating flow of solvent refers to the process of TBP/ sulfonated kerosene returning to the solvent tank after extraction, washing and stripping from the solvent tank, in which the solvent is recycledU503622 the circulating flow of raw acid refers to the process that raw acid reaches the raffinate tank after countercurrent extraction from the raw acid tank. During this process, the concentration of mixed acid in raw acid gradually decreases. If the raffinate tank is connected with the raw acid tank, the raw acid will be continuously extracted until the mixed acid is almost completely extracted. Product flow refers to the process that tap water enters back extraction to get back-extracted dilute acid. Part of the stripping dilute acid is used as detergent and finally stripped together with the original acid, and the concentration of stripping dilute acid decreases with the decrease of mixed acid concentration in the upstream original acid. The three "streams" are not completely independent, but interrelated. For example, under the condition of constant extraction rate, if the mixed acid products in the product stream decrease, the mixed acid in the solvent circulation stream increases, and the mixed acid in the raw acid circulation stream increases compared with before, which in turn will reduce the extraction rate.

The above-mentioned embodiments only describe the preferred mode of the invention, and do not limit the scope of the invention. Under the premise of not departing from the design spirit of the invention, various modifications and improvements made by ordinary technicians in the field to the technical scheme of the invention shall fall within the protection scope determined by the claims of the invention.

Claims (9)

CLAIMS LU503622

1. A method for extracting and recovering mixed acid from chemical polishing solution by tributyl phosphate, comprising: s1, adding an organic phase into the chemical polishing solution for extraction to obtain a loaded organic phase and a raffinate phase of the mixed acid; s2, washing the loaded organic phase with dilute acid to obtain a back-extraction dilute acid; s3, contacting the back extraction dilute acid with water for stripping to obtain mixed dilute acid solution, wherein the organic phase is a mixture of sulfonated kerosene and tributyl phosphate with a volume ratio of 1:4.

2. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s1, the ratio of the chemical polishing solution to the organic phase is 4:1.

3. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s1, the extraction temperature is 28°C.

4. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s1, the extraction is a three-stage countercurrent extraction.

5. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s1, the concentration of the mixed acid in the loaded organic phase is 0.08-0.10 g/ml.

6. The method for extracting and recovering the mixed acid from the chemickl503622 polishing solution by tributyl phosphate according to claim 1, wherein in s2, the ratio of the loaded organic phase to the diluted acid is 10-15:1.

7. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s3, the ratio of the back-extraction dilute acid to water is 1:3-4.

8. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s3, the back extraction is 3-4 stages.

9. The method for extracting and recovering the mixed acid from the chemical polishing solution by tributyl phosphate according to claim 1, wherein in s3, the temperature of the back extraction is 65-70°C.