CN113607878A - Assay method for concentration of free acid and ferrous ion in pickling waste hydrochloric acid and application - Google Patents
Assay method for concentration of free acid and ferrous ion in pickling waste hydrochloric acid and application Download PDFInfo
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Abstract
The invention provides a method for testing the concentration of free acid and ferrous ions in pickling waste hydrochloric acid, belonging to the technical field of production of pickling and acid regeneration systems, and comprising the following steps: primary titration: dropwise adding a sodium hydroxide solution into the pickling waste hydrochloric acid until the Ph of the pickling waste hydrochloric acid is 4-6; and (3) carrying out secondary titration: adding a shielding agent into the acid-washing waste hydrochloric acid subjected to primary titration, and then dripping a sodium hydroxide solution until no precipitate is generated; and obtaining the concentration of free acid and the concentration of ferrous ions in the pickling waste hydrochloric acid according to the OH < - > content of the sodium hydroxide solution in the primary titration and the secondary titration. The method does not use dichromate which is harmful to human body, improves the safety of the test, and effectively improves the test efficiency of free acid and ferrous ions in the waste hydrochloric acid. The invention also provides the application of the assay method of the concentration of free acid and ferrous ions in the pickling waste hydrochloric acid in a pickling process control or acid regeneration system.
Description
Technical Field
The invention belongs to the technical field of production of pickling and acid regeneration systems, and particularly relates to a method for testing the concentrations of free acid and ferrous ions in pickling waste hydrochloric acid and application thereof.
Background
The main components of the generated waste hydrochloric acid are free acid (free hydrochloric acid) and ferrous chloride, the concentrations of the two substances have important influence on the control of the pickling process and the production of an acid regeneration system, and continuous assay tracking is required.
In the case of assaying free acid and ferrous ion with an automatic titrator, the conventional method is to titrate the free acid concentration with sodium hydroxide, the ferrous ion concentration with potassium dichromate, and the two assays are performed separately. The dichromate is I grade (extreme harm) in the classification of occupational toxicant exposure harm degree, the harm to human bodies is great, and the same waste acid sample is assayed twice, which wastes working hours and equipment.
Disclosure of Invention
In order to solve the technical problems of low assay efficiency of free acid and ferrous ions in the waste hydrochloric acid and great harm of dichromate to human bodies, the invention provides the assay method of the concentrations of the free acid and the ferrous ions in the acid-washing waste hydrochloric acid, which does not use dichromate which has great harm to human bodies, improves the assay safety and effectively improves the assay efficiency of the free acid and the ferrous ions in the waste hydrochloric acid.
The invention also provides the application of the assay method of the concentration of free acid and ferrous ions in the pickling waste hydrochloric acid in a pickling process control or acid regeneration system.
The invention is realized by the following technical scheme:
the application provides an assay method for concentrations of free acid and ferrous ions in acid-washing waste hydrochloric acid, which comprises the following steps:
primary titration: dropwise adding a sodium hydroxide solution into the pickling waste hydrochloric acid until the Ph of the pickling waste hydrochloric acid is 4-6;
and (3) carrying out secondary titration: adding a shielding agent into the acid-washing waste hydrochloric acid subjected to primary titration, and then dripping a sodium hydroxide solution until no precipitate is generated;
according to the beginningSub-titration and OH of sodium hydroxide solution in said sub-titration-And (4) obtaining the concentration of free acid and the concentration of ferrous ions in the acid-washing waste hydrochloric acid.
Optionally, the shielding agent is sodium thiosulfate or a sodium thiosulfate solution.
Optionally, the mass of the sodium thiosulfate added is 0.2-0.3 g/ml of the waste pickling hydrochloric acid;
or, in the added sodium thiosulfate solution, the following relation exists between the mass of the sodium thiosulfate and the volume of the pickling waste hydrochloric acid:
1ml of the acid-washing waste hydrochloric acid corresponds to 0.2-0.3 g of sodium thiosulfate.
Optionally, in the primary titration, the initial volume of the waste acid washing hydrochloric acid is 1-4 ml.
Optionally, in the secondary titration, the molar concentration of the sodium thiosulfate solution is 0.5-2 mol/L, and the dropping volume is 1.5-6 ml.
Optionally, in the primary titration and the secondary titration, the concentrations of the sodium hydroxide solutions are the same or different, and the molar concentration of the sodium hydroxide solution is controlled to be 0.2-2 mol/L.
Optionally, the OH of the sodium hydroxide solution in the primary titration and the secondary titration-Obtaining the concentration of free acid and the concentration of ferrous ions in the waste hydrochloric acid after acid washing, and specifically comprises the following steps:
OH of sodium hydroxide solution according to said first titration-Obtaining the concentration of free acid in the pickling waste hydrochloric acid by the content and the initial volume of the pickling waste hydrochloric acid;
OH of sodium hydroxide solution according to the second titration-The content and the initial volume of the pickling waste hydrochloric acid are obtained to obtain the concentration of ferrous ions in the pickling waste hydrochloric acid.
Optionally, the pickling waste hydrochloric acid is a waste liquid obtained by pickling a steel plate.
Optionally, the precipitate is ferrous hydroxide.
Based on the same inventive concept, the application also provides the application of the assay method for the concentration of free acid and ferrous ions in the pickling waste hydrochloric acid in a pickling process control or acid regeneration system.
One or more technical schemes in the invention at least have the following technical effects or advantages:
1. the invention relates to a method for testing the concentration of free acid and ferrous ion in pickling waste hydrochloric acid, wherein primary titration is to titrate the free acid in the pickling waste hydrochloric acid by using a sodium hydroxide solution, when the pH is 4-6, the free acid is neutralized, a shielding agent is added into the pickling waste hydrochloric acid subjected to primary titration to shield impurity metal ions in the pickling waste hydrochloric acid, then, the sodium hydroxide solution is continuously dripped until no precipitate is generated, the ferrous ion titration is finished, and OH of the sodium hydroxide solution consumed by the primary titration and the secondary titration is used according to the OH of the sodium hydroxide solution-The method does not use dichromate which has great harm to human bodies, improves the safety of the test, is simple and easy to operate, and effectively improves the test efficiency of the free acid and the ferrous ions in the waste hydrochloric acid.
2. The invention relates to a method for testing the concentration of free acid and ferrous ion in acid-washing waste hydrochloric acid.A shielding agent selects sodium thiosulfate or a solution thereof, the waste acid contains more impurity metal ions which are easy to react with sodium hydroxide to influence the accuracy of secondary titration, and the sodium thiosulfate can generate complex reaction with the metal ions to form a complex compound due to the structural particularity of the sodium thiosulfate but does not react with the ferrous ion, so the impurity ions in the waste acid can be shielded by the sodium thiosulfate, but the sodium thiosulfate is unstable under the acidic condition and is easy to generate disproportionation reaction, and therefore, the invention selects to add sufficient sodium thiosulfate after the primary titration reaction is finished.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
In order to more clearly illustrate the technical solutions in the present application, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a flow chart of an assay method for the concentration of free acid and ferrous ions in acid-washed waste hydrochloric acid according to the present invention;
FIG. 2 is a parameter setting interface diagram of an automatic titrator in accordance with an embodiment of the invention;
FIG. 3 is a diagram showing the completion of the primary titration by the automatic titrator in accordance with the present invention;
FIG. 4 is a diagram showing the end of the second titration by the automatic titrator according to the embodiment of the invention.
In the figure: 1-mV/pH titration parameters were selected, 2-end jump was set to "Medium", 3-Instrument auto-capture endpoint, 4-endpoint numerical display, 5-Instrument auto-capture endpoint, 6-endpoint numerical display.
Detailed Description
The present invention will be described in detail below with reference to specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly apparent therefrom. It will be understood by those skilled in the art that these specific embodiments and examples are for the purpose of illustrating the invention and are not to be construed as limiting the invention.
Throughout the specification, unless otherwise specifically noted, terms used herein should be understood as having meanings as commonly used in the art. Accordingly, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. If there is a conflict, the present specification will control.
Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment and the like used in the present invention are commercially available or can be prepared by existing methods.
It should be further noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions.
In order to solve the technical problems, the general idea is as follows:
at present, when an automatic titrator is used for testing free acid and ferrous ions, the traditional method is to titrate the concentration of the free acid by sodium hydroxide, titrate the concentration of the ferrous ions by potassium dichromate, and respectively carry out two tests. The dichromate is I grade (extreme harm) in the classification of occupational toxicant exposure harm degree, the harm to human bodies is great, and the same waste acid sample is assayed twice, which wastes working hours and equipment.
Based on the method, sodium thiosulfate solution with low hazard is used for shielding impurity ions in waste acid, sodium hydroxide solution is uniformly used for titration, and two results of free acid and ferrous iron concentration are obtained by performing one-time waste acid assay according to different sequences of chemical reaction. The labor hour is saved and the medicine with great harm is replaced.
According to an exemplary embodiment of the present invention, there is provided an assay method for concentrations of free acid and ferrous ions in acid-washing waste hydrochloric acid, as shown in fig. 1, the method including:
s1, primary titration: dropwise adding a sodium hydroxide solution into the pickling waste hydrochloric acid until the Ph of the pickling waste hydrochloric acid is 4-6;
s2, secondary titration: adding a shielding agent into the acid-washing waste hydrochloric acid subjected to primary titration, and then dripping a sodium hydroxide solution until no precipitate is generated;
s3, according toOH of the sodium hydroxide solution in the primary titration and the secondary titration-And (4) obtaining the concentration of free acid and the concentration of ferrous ions in the acid-washing waste hydrochloric acid.
According to the method, primary titration is carried out by titrating free acid in pickling waste hydrochloric acid through a sodium hydroxide solution, when Ph is 4-6, the free acid is neutralized, a shielding agent is added into the pickling waste hydrochloric acid subjected to primary titration to shield impurity metal ions in the pickling waste hydrochloric acid, the sodium hydroxide solution is continuously dripped until precipitation is not generated, ferrous ions are titrated, and OH of the sodium hydroxide solution consumed by primary titration and secondary titration is used-The method does not use dichromate which has great harm to human bodies, improves the safety of the test, is simple and easy to operate, and effectively improves the test efficiency of the free acid and the ferrous ions in the waste hydrochloric acid.
The main principle of the assay method of the invention is as follows: in the titration process by using the sodium hydroxide, two chemical reactions are involved, the acid-base neutralization reaction of the free acid and the sodium hydroxide is preferentially carried out, and after the reaction is finished, the concentration of the free acid is calculated according to a reaction equation through the volume and the concentration of the consumed sodium hydroxide. At this point the solution is weakly acidic. Continuing to start the titration, the ferrous iron undergoes a metathesis reaction with sodium hydroxide which produces a precipitate. Since the waste acid contains a plurality of impurity ions, the waste acid is easy to react with sodium hydroxide, so that the measurement result is inaccurate or the terminal point cannot be judged. Due to the structural particularity of the sodium thiosulfate, the sodium thiosulfate can perform a complex reaction with metal ions to form a complex, but does not react with ferrous ions, so that impurity ions in waste acid can be masked. The concentration of ferrous ions can be calculated by the volume and concentration of sodium hydroxide consumed by secondary titration. The assay method is simple, easy to operate, high in safety and high in accuracy rate through long-time tracking comparison.
As an alternative embodiment, the shielding agent is sodium thiosulfate or a sodium thiosulfate solution.
In the invention, the shielding agent is sodium thiosulfate or a solution thereof, because the waste acid contains more impurity metal ions which are easy to react with sodium hydroxide, the accuracy of secondary titration is influenced, and because the sodium thiosulfate can generate a complex reaction with the metal ions to form a complex compound due to the structural particularity of the sodium thiosulfate, but does not react with ferrous ions, the impurity ions in the waste acid can be shielded by the sodium thiosulfate, but the sodium thiosulfate is unstable under an acidic condition and is easy to generate a disproportionation reaction, so that a sufficient amount of sodium thiosulfate is added after the primary titration reaction is finished.
As an optional embodiment, the mass of the sodium thiosulfate added is 0.2-0.3 g/ml of the acid-washing waste hydrochloric acid;
or, in the added sodium thiosulfate solution, the following relation exists between the mass of the sodium thiosulfate and the volume of the pickling waste hydrochloric acid:
1ml of the acid-washing waste hydrochloric acid corresponds to 0.2-0.3 g of sodium thiosulfate.
In this application, sodium thiosulfate can adopt the mode of weighing the solid and once only add, also can configure into solution, preferably add with the mode of solution, so that dissolve fast and react, sodium thiosulfate's addition quality is the useless hydrochloric acid of 0.2 ~ 0.3g/ml pickling, can guarantee that sodium thiosulfate is the abundant compared with impurity metal ion, this is decided according to the conventional concentration of impurity metal ion in the useless hydrochloric acid of pickling, if sodium thiosulfate addition quantity is too big, then can cause unnecessary waste, can also influence the judgement of reaction terminal point simultaneously.
As an alternative embodiment, in the primary titration, the initial volume of the pickling waste hydrochloric acid is 1-4 ml.
In the application, the initial volume of the waste acid washing hydrochloric acid is 1-4 ml, and a larger or smaller initial volume can be selected according to actual needs.
In an optional embodiment, in the secondary dropping, the molar concentration of the sodium thiosulfate solution is 0.5 to 2mol/L, and the dropping volume is 1.5 to 6 ml.
In the application, the solution molar concentration of the sodium thiosulfate solution is 0.5-2 mol/L, the dropping volume is 1.5-6 ml, and the amount of the sodium sulfate can be ensured to meet the requirement of effectively removing impurity metal ions.
In an alternative embodiment, the concentrations of the sodium hydroxide solutions in the primary titration and the secondary titration are the same or different, and the molar concentration of the sodium hydroxide solution is controlled to be 0.2-2 mol/L.
In this application, the molar concentration control of sodium hydroxide solution is at 0.2 ~ 2mol/L to guarantee to titrate the effect, the detection accuracy can be reduced to the concentration is too high, and the concentration is crossed lowly and then can prolong titration time.
As an alternative embodiment, the OH of the sodium hydroxide solution according to the primary titration and the secondary titration-Obtaining the concentration of free acid and the concentration of ferrous ions in the waste hydrochloric acid after acid washing, and specifically comprises the following steps:
OH of sodium hydroxide solution according to said first titration-Obtaining the concentration of free acid in the pickling waste hydrochloric acid by the content and the initial volume of the pickling waste hydrochloric acid;
OH of sodium hydroxide solution according to the second titration-The content and the initial volume of the pickling waste hydrochloric acid are obtained to obtain the concentration of ferrous ions in the pickling waste hydrochloric acid.
In the application, the primary titration and the secondary titration are uniformly titrated by using the sodium hydroxide solution, and according to different sequences of chemical reactions, two results of free acid and ferrous concentration are obtained respectively by performing one-time waste acid assay, so that the labor hour is saved, and meanwhile, a drug with large harm is replaced.
As an alternative embodiment, the pickling waste hydrochloric acid is waste liquor obtained by pickling a steel plate.
As an alternative embodiment, the precipitate is ferrous hydroxide.
According to another exemplary embodiment of the present invention, there is provided a use of an assay method for free acid and ferrous ion concentration in acid pickling waste hydrochloric acid in an acid pickling process control or acid regeneration system.
The following will describe in detail the assay method of the free acid and ferrous ion concentration in the pickling waste hydrochloric acid according to the present application with reference to examples, comparative examples and experimental data.
Examples
The embodiment of the invention relates to an assay method for the concentration of free acid and ferrous ions in acid-washing waste hydrochloric acid, which comprises the following steps:
1) firstly, the concentration and the dosage of the sodium thiosulfate are determined according to the components of the pickling waste hydrochloric acid. The free acid concentration range of the moving steel pickling waste acid is 20-80g/l, and the ferrous iron range is 70-210 g/l. Through a large number of tests, the use concentration of the sodium thiosulfate is determined to be 1mol/l, and 3ml is used in each test, so that the test requirements can be met.
2) Adjusting parameters of the automatic titrator. The experiment used a thunder magnetic model ZDJ-5 automatic titrator. And (3) selecting a pre-titration mode, wherein in the mV/pH titration parameter options, both mV titration and pH titration can be selected, the assay result is not influenced, the size of the jump quantity is selected to be 'middle', the end point judgment of two assay reactions can be met, and the others are instrument default values, as shown in figure 2. Once the parameters are set, they do not need to be modified again.
3) Determining assay flow and calculation method
Experimental apparatus and drugs:
model ZDJ-5 automatic titrator, 231-01PH glass electrode, 212 reference electrode, 1mol/L sodium hydroxide solution, 1mol/L sodium thiosulfate solution
(4) And (3) assay steps:
taking 2mL of acid-washing waste hydrochloric acid by a pipette into a special conical flask for an automatic titrator; adding 100mL of distilled water into a special conical flask, and adding magnetic particles; placing the special conical flask on a magnetic stirrer of a titrator, carrying out automatic titration by using 1mol/L sodium hydroxide solution, after the end point is prompted (the pH of the end point is within the range of 4-6), pressing a stop button, and recording a titration end point reading V1, as shown in figure 3;
after titration, 3mL of 1mol/L sodium thiosulfate standard solution was added to the acid solution, the titration was continued, the endpoint was automatically indicated, and the titration endpoint reading V2 was recorded, as shown in FIG. 4.
The calculation method comprises the following steps:
concentration of free acid (g/L) ═ volume consumed sodium hydroxide V1(ml) × 18.23
Concentration (g/L) of ferrous ion (volume of sodium hydroxide consumed V2(ml) × 14)
Total acid concentration (g/L) ═ 1.3 divalent iron concentration + free acid concentration.
And (4) related tests:
taking 2ml of waste hydrochloric acid samples generated by 5 pickling lines with different concentrations respectively, and naming the samples as 1-5, and performing assay on the concentrations of free acid and ferrous ions by adopting the steps respectively.
And simultaneously, the existing titration method is also adopted to test the samples 1-5. The existing titration method comprises the following steps:
the free acid concentration was titrated with sodium hydroxide: taking 2mL of acid-washing waste hydrochloric acid by a pipette into a special conical flask for an automatic titrator; adding 100mL of distilled water into a special conical flask, and adding magnetic particles; the special conical flask is placed on a magnetic stirrer of a titrator, 1mol/L sodium hydroxide solution is used for automatic titration, after the end point is prompted, an end button is pressed, and a titration end point reading V1' is recorded.
The ferrous iron concentration was titrated with potassium dichromate:
reagents and materials:
0.1000mol/L 1/6K2Cr2O7a standard solution;
mixed sulfuric-phosphoric acid solution (15+15+ 70): 150mL of sulfuric acid and 150mL of phosphoric acid were measured, dissolved in 500mL of water, and diluted to 1000 mL.
0.5% sodium diphenylamine sulfonate indicator: 0.5g of sodium diphenylamine sulfonate is weighed out, dissolved in 100mL of water and, if necessary, 1 to 2 drops of sulfuric acid are added.
The operation method comprises the following steps:
sucking 1mL of sample with a clean pipette, placing the sample in a 500mL triangular flask which is pre-filled with 150mL of distilled water, shaking uniformly, adding 10-15mL of sulfur-phosphorus mixed acid solution, adding 3-4 drops of 0.5% sodium diphenylamine sulfonate indicator, and using 0.1 mol/L1/6K2Cr2O7The standard solution was titrated and the end point was the solution changed from green to bright purple.
Wherein the concentration (g/L) of free acid is equal to the volume of sodium hydroxide consumed V1' (ml). times.18.23
Concentration (g/L) of divalent iron ion, volume of potassium dichromate consumed V2' (m1) × 5.585
Concentration of total acid (g/L) ═ 1.3 divalent iron concentration + free acid concentration
The assay results are shown in table 1:
TABLE 1 concentration of free acid and ferrous ion
As can be seen from Table 1, the concentration data of the free acid and the ferrous ion obtained by the assay method of the present invention is basically consistent with the data obtained by the existing titration method, which proves that the assay method of the present invention has high accuracy, and compared with the existing titration method, the assay method of the present invention has higher assay efficiency and does not use harmful potassium dichromate.
Comparative example
Comparative example the only difference compared to the examples is that: the same procedure was followed without addition of sodium thiosulfate.
The present application performs assays on the above samples 1 to 5 by using the method of comparative example, and the results are shown in table 2:
TABLE 2 concentration of free acid and ferrous ion
In Table 2, the V1 "reading indicates the volume of sodium hydroxide consumed for the first titration as indicated by the comparative automatic titrator, and the V2" reading indicates the volume of sodium hydroxide consumed for the second titration as indicated by the comparative automatic titrator.
As can be seen from Table 2, the free acid concentration obtained by the detection method of the comparative example was closer to that of the example, and the concentration of the ferrous ion was much different from that of the example and the existing assay method or the endpoint could not be determined.
Detailed description of the drawings 2-4:
as shown in FIG. 2, an instrument parameter setting interface of the present invention is depicted, wherein 1 represents mV/pH titration parameter selection, which allows real-time display of the variation of the corresponding parameter during the assay without affecting the assay result. The experiment was performed using a pH titration. 2 represents the jump amount setting, which is "medium" in this experiment, i.e., the end point capture that can satisfy the double titration. Other parameters are defaults. All parameters can be set and adjusted according to actual conditions.
As shown in fig. 3, a display of the initial titration, i.e., free acid titration to the end volume of sample 1 of the example of the present invention is depicted. Where 3 denotes the end point on the titration curve and 4 denotes the volume consumption of sodium hydroxide solution and the pH value corresponding to the end point of the titration curve.
As shown in fig. 4, a display screen of sample 1 of the example of the present invention when the volume reaches the end of the second titration, i.e., the titration of the ferrous ion, is depicted. Where 5 denotes the end point on the titration curve showing the volume consumption and pH of the sodium hydroxide solution corresponding to the end point of the titration curve.
One or more technical solutions in the present application at least have the following technical effects or advantages:
(1) the application provides a test method of free acid and ferrous ion concentration in pickling waste hydrochloric acid, the initial titration is to titrate the free acid in the pickling waste hydrochloric acid through a sodium hydroxide solution, when Ph is 4-6, the free acid is neutralized and finished, a shielding agent is added into the pickling waste hydrochloric acid subjected to the initial titration to shield impurity metal ions in the pickling waste hydrochloric acid, the sodium hydroxide solution is continuously dripped until precipitation is not generated, then the ferrous ion titration is finished, and OH of the sodium hydroxide solution consumed according to the initial titration and the secondary titration is OH-The method does not use dichromate which has great harm to human bodies, improves the safety of the test, is simple and easy to operate, and effectively improves the test efficiency of the free acid and the ferrous ions in the waste hydrochloric acid.
(2) The invention discloses a method for testing the concentration of free acid and ferrous ion in acid-washing waste hydrochloric acid.A shielding agent selects sodium thiosulfate or a solution thereof, the waste acid contains more impurity metal ions which are easy to react with sodium hydroxide to influence the accuracy of secondary titration, and the sodium thiosulfate can generate a complex reaction with the metal ions to form a complex compound due to the structural particularity of the sodium thiosulfate but does not react with the ferrous ion, so that the impurity ions in the waste acid can be shielded by the sodium thiosulfate, but the sodium thiosulfate is unstable under an acidic condition and is easy to generate a disproportionation reaction, and therefore, the sufficient amount of sodium thiosulfate is added after the primary titration reaction is finished.
Finally, it should also be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. An assay method for free acid and ferrous ion concentration in acid-washing waste hydrochloric acid, which is characterized by comprising the following steps:
primary titration: dropwise adding a sodium hydroxide solution into the pickling waste hydrochloric acid until the Ph of the pickling waste hydrochloric acid is 4-6;
and (3) carrying out secondary titration: adding a shielding agent into the acid-washing waste hydrochloric acid subjected to primary titration, and then dripping a sodium hydroxide solution until no precipitate is generated;
according to OH of sodium hydroxide solution in the primary titration and the secondary titration-And (4) obtaining the concentration of free acid and the concentration of ferrous ions in the acid-washing waste hydrochloric acid.
2. The method for assaying the concentrations of free acids and ferrous ions in acid-washed waste hydrochloric acid according to claim 1, wherein the shielding agent is sodium thiosulfate or a sodium thiosulfate solution.
3. The assay method for the concentrations of free acid and ferrous ions in acid-washing waste hydrochloric acid according to claim 2, wherein the mass of sodium thiosulfate added is 0.2-0.3 g/ml of the acid-washing waste hydrochloric acid;
or, in the added sodium thiosulfate solution, the following relation exists between the mass of the sodium thiosulfate and the volume of the pickling waste hydrochloric acid:
1ml of the acid-washing waste hydrochloric acid corresponds to 0.2-0.3 g of sodium thiosulfate.
4. The method for assaying the concentrations of free acid and ferrous ions in acid-washing waste hydrochloric acid according to claim 2, wherein the initial volume of acid-washing waste hydrochloric acid in the primary titration is 1-4 ml.
5. The method for assaying concentrations of free acids and ferrous ions in acid-washing waste hydrochloric acid according to claim 4, wherein in the secondary titration, the molar concentration of the sodium thiosulfate solution is 0.5-2 mol/L, and the dropping volume is 1.5-6 ml.
6. The method for assaying concentrations of free acids and ferrous ions in acid-washing waste hydrochloric acid according to claim 1, wherein in the primary titration and the secondary titration, the concentrations of the sodium hydroxide solutions are the same or different, and the molar concentration of the sodium hydroxide solution is controlled to be 0.2-2 mol/L.
7. The method for assaying concentrations of free acids and ferrous ions in acid-washing waste hydrochloric acid according to claim 1, wherein the OH of sodium hydroxide solution according to the primary titration and the secondary titration-Obtaining the concentration of free acid and the concentration of ferrous ions in the waste hydrochloric acid after acid washing, and specifically comprises the following steps:
OH of sodium hydroxide solution according to said first titration-Obtaining the concentration of free acid in the pickling waste hydrochloric acid by the content and the initial volume of the pickling waste hydrochloric acid;
OH of sodium hydroxide solution according to the second titration-The content and the initial volume of the pickling waste hydrochloric acid are obtained to obtain the concentration of ferrous ions in the pickling waste hydrochloric acid.
8. The method for assaying concentrations of free acids and ferrous ions in pickling waste hydrochloric acid according to claim 1, wherein the pickling waste hydrochloric acid is a waste liquid obtained from steel plate pickling.
9. The method for assaying the concentration of free acid and ferrous ions in acid-washing waste hydrochloric acid according to claim 1, wherein the precipitate is ferrous hydroxide.
10. Use of an assay method for the concentration of free acid and ferrous ions in acid wash waste hydrochloric acid as defined in any one of claims 1 to 9 in an acid wash process control or acid regeneration system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110867797.5A CN113607878A (en) | 2021-07-29 | 2021-07-29 | Assay method for concentration of free acid and ferrous ion in pickling waste hydrochloric acid and application |
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