Desulfurizing agents, desulfurization systems, methods and applications for cyanide determination

Abstract

This invention relates to the field of cyanide determination technology, specifically disclosing a desulfurizing agent, desulfurization system, and method and application for cyanide determination, including the following steps: S1, pretreatment of the sample to be tested; S2, setting up a distillation apparatus; S3, after adding the sample to be tested to the distillation flask, first add water and sodium hydroxide solution, then add copper sulfate solution and EDTA-2Na solution; then add phosphoric acid; based on 5g of sample weight, the amount of copper sulfate solution used is 5-20mL, the amount of EDTA-2Na solution used is 10-20mL, and the sulfur content in the sample is 1 ug / g-1.5 ug / g; S4, heating and distillation; S5, measuring the cyanide content. This invention is suitable for the determination of cyanide in samples with high sulfur concentrations. It can not only effectively shield the interference of sulfides on cyanide determination, but also minimize (CN⁻) loss after distillation, thereby improving the accuracy of cyanide determination in samples with high sulfur concentrations.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cyanide determination, in particular to a desulfurizer for cyanide determination, a desulfurization system, a cyanide determination method and application. BACKGROUND

[0002] Cyanide is a class of compounds containing cyanide group (-C≡N), and its characteristics vary significantly due to its specific type (inorganic cyanide, organic cyanide, etc.) and metal ions. Regardless of which cyanide, its core commonality is highly toxic. Cyanide ion (CN - ) can bind tightly with the trivalent iron (Fe 3+ ) in cytochrome c oxidase in human cell mitochondria, making it unable to be converted into divalent iron (Fe 2+ ), thereby causing the interruption of the cell respiration chain. Cells cannot utilize oxygen in the blood, causing suffocation inside the cells.

[0003] Many solid and liquid wastes contain cyanide, which needs to be detected. Common detection methods include silver nitrate titration, isonicotinic acid-pyrazolone spectrophotometry, pyridine-barbituric acid spectrophotometry, ion selective electrode method, and flow injection-spectrophotometry. Regardless of which method is used for detection, in order to improve the accuracy of the results, interfering substances need to be shielded, including sulfides, ammonium ions, etc. Among them, sulfides are difficult to shield, especially when the sample to be tested contains high concentrations of sulfur. The interference mechanism of sulfides on cyanide determination is complex and diverse. On the one hand, sulfides and cyanides can react with each other to generate thiocyanide compounds, consuming cyanide; on the other hand, sulfides will react with reagents such as chloramine T added during the cyanide color development process, competing with cyanide ions. Therefore, in summary, the concentration of sulfides has a negative effect on the absorbance of cyanide determination.

[0004] Since cyanide needs to be stored in alkaline conditions, sulfides are also easily preserved in alkaline conditions. During distillation, the pH of the distillate needs to be adjusted to be acidic, so both sulfides and cyanides are easily distilled out, so it is necessary to remove the interference of sulfides as much as possible before distillation. Under acidic conditions, sulfides mainly exist as H2S, which is volatile, but cyanides are also not easy to store under acidic conditions, so the removal of sulfide interference is mostly done using heavy metal precipitation method.

[0005] The shielding agent used in heavy metal precipitation method mainly includes cadmium carbonate method, silver nitrate method, potassium permanganate method and copper sulfate method. For specific operations, refer to the standard methods of CJT 221-2023 and HJ 745-2015.

[0006] For example: CN111337488B discloses a method for determining soil cyanide and total cyanide. In the determination of cyanide and total cyanide, stannous chloride, copper sulfate, phosphoric acid and the like are added as reaction solution. By gradually heating by gradient, the chemical reaction is more fully ensured to realize sufficient distillation of total cyanide. However, when the reaction solution is used for solid waste treatment containing high concentration of sulfur, although the interference of sulfide can be shielded, loss after distillation (CN - ) will occur, and finally the detection result will be low.

[0007] CN107991429B discloses a method for determining easily released cyanide in cyanide-containing wastewater containing sulfide. In the method, secondary distillation is used to improve the accuracy of the detection result. In the first distillation, zinc nitrate and tartaric acid are used to ensure that the easily released cyanide enters the first distillate. However, most of the sulfur ions also enter the first distillate. In the second distillation, silver nitrate is used as a shielding agent. Silver nitrate reacts with sulfide to form silver sulfide precipitate, removing the interference of sulfide. At the same time, it is considered that silver nitrate will also combine with cyanide. Therefore, EDTA and 10ml phosphoric acid solution are added for the second distillation. EDTA reacts with silver ions to release cyanide ions, thereby improving the measurement accuracy of cyanide. However, the concentration of sulfide in the sample is not fully considered. Silver nitrate as a shielding agent can only be applied to low-sulfur samples and cannot be applied to samples with high sulfur concentration. SUMMARY

[0008] The purpose of the present application is to provide a desulfurizing agent for cyanide determination, a desulfurizing system, a cyanide determination method and application, which is suitable for cyanide determination of samples with high sulfur concentration. It can not only effectively shield the interference of sulfide on cyanide determination, but also has less loss after distillation (CN - ), and can improve the accuracy of cyanide determination of samples with high sulfur concentration.

[0009] The present application is realized by the following technical solutions:

[0010] A cyanide determination method, comprising the following steps:

[0011] S1, pretreatment of the sample to be tested;

[0012] S2, building a distillation device: connecting the distillation flask and the receiving bottle by pipeline, and loading sodium hydroxide solution as absorption liquid in the receiving bottle;

[0013] S3, after adding the sample to be tested in the distillation flask, first add water and sodium hydroxide solution to adjust the system to alkaline, then add copper sulfate solution and EDTA-2Na solution; then add phosphoric acid, cover the plug; wherein the concentration of copper sulfate solution is 200mg / L, the concentration of EDTA-2Na solution is 100g / L; the amount of copper sulfate solution is 5-20mL, the amount of EDTA-2Na solution is 10-20mL, based on the weight of 5g sample to be tested, the content of sulfur in the sample to be tested is 1 ug / g -1.5 ug / g;

[0014] S4, heating distillation;

[0015] S5, the absorption liquid containing the distillate is measured for cyanide content by spectrophotometry.

[0016] The biggest difference between the present application and the prior art is that:

[0017] For the determination of cyanide in samples with high sulfur concentration (sulfur content in solid is greater than 0.5 ug / g), the desulfurizer is optimized and designed, the present application uses a combination of copper sulfate solution and EDTA-2Na solution, and the concentration and amount of copper sulfate solution and EDTA-2Na solution are limited, which realizes the desulfurization and shielding of the interference of sulfur on the determination of cyanide, and reduces the loss of (CN - ) in the distillate. The specific principle is as follows:

[0018] Similar to silver nitrate, copper sulfate reacts with sulfide on one hand and reacts with cyanide on the other hand to form copper cyanide, and even further form copper cyanide complex; but divalent copper is blue, which is easier to identify than silver nitrate precipitation. Therefore, if only copper sulfate solution is used, the loss of (CN - ) in the distillate will be large, which will make the measurement result of cyanide significantly lower. When copper sulfate solution and EDTA-2Na solution are used at the same time, EDTA-2Na as a strong chelating agent, complexes with metal ions in the sample, prevents these metal ions from reacting with cyanide, and helps to release cyanide from the complex.

[0019] The prior art uses stannous chloride solution and copper sulfate solution for cyanide determination to shield the interference of sulfur, but the present application finds through experiments that when stannous chloride and copper sulfate are combined for measuring the content of cyanide in samples with high sulfur concentration, although stannous chloride acts as a reducing agent in the distillation process and is added to the distillation flask together with copper sulfate, it promotes the decomposition of complex cyanide and converts various forms of cyanide into measurable hydrogen cyanide. However, stannous chloride is not effective in decomposing copper cyanide complex, so the combination of stannous chloride solution and copper sulfate solution will also cause a large loss of (CN - ) in the distillate.

[0020] In summary, the present application designs the desulfurizer used for measuring cyanide content as a combination of copper sulfate solution and EDTA-2Na solution; can be applied to cyanide determination of samples with high sulfur concentration, can effectively shield the interference of sulfides on cyanide determination, and has less loss after distillation (CN - ), and can improve the accuracy of cyanide determination of samples with high sulfur concentration.

[0021] In addition, since copper sulfate is a strong acid weak base salt, attention should be paid to the pH of the solution before distillation. In particular, the copper sulfate used for impurity removal is a 200 mg / L near saturated solution, and the pH is about 3, so after adding copper sulfate, the distillation liquid will become acidic, and then the cyanide will escape. The present application solves this problem from two aspects: first, add water and sodium hydroxide solution to adjust the system to alkaline, and then add copper sulfate solution and EDTA-2Na solution, so as to avoid the escape of cyanide due to pH change after directly adding copper sulfate solution to the sample; second, contact copper sulfate with the sample as late as possible, and seal the distillation flask immediately after adding reagents such as copper sulfate for distillation.

[0022] In a preferred mode, in step S1, the pretreatment process is:

[0023] Add sodium bicarbonate and quartz powder to the sample to be measured, then crush and sieve, and take an equal amount of powder from the sample to be measured as a test sample for testing.

[0024] In actual measurement process, the distribution of sulfides and cyanides in the sample to be measured is not uniform. In order to avoid measurement error caused by sampling, the sample to be measured needs to be pretreated to improve the uniformity of the distribution of sulfides and cyanides in the sample to be measured, so as to ensure the consistency of batch measurement results and the accuracy of single measurement results of the same sample to be measured.

[0025] In the prior art, the conventional pretreatment method is to mix the sample to be measured. In the present application, sodium bicarbonate and quartz powder are added, wherein sodium bicarbonate is a weak base, and by adding a certain amount of sodium bicarbonate, the sulfides and cyanides in the sample to be measured can be better preserved. The use amount of the sample to be measured in the present application is small, and if the mixing method is directly used, the effect of uniform distribution of sulfides and cyanides is limited. The addition of sodium bicarbonate and quartz powder in the present application can not only increase the overall amount of materials to facilitate better mixing, but also improve the mixing effect of the sample to be measured. Both of them do not contain sulfides and cyanides and other substances that affect the measurement results of cyanides.

[0026] In a preferred mode, in steps S2 and S3, the concentration of sodium hydroxide solution is 10 g / L.

[0027] In a preferred embodiment, in step S3, the copper sulfate solution and the EDTA-2Na solution are added simultaneously with the addition of the ferric chloride solution and the sodium citrate solution, wherein the concentration of the ferric chloride solution is 50 g / L, and the concentration of the sodium citrate solution is 10 g / L; the amount of the ferric chloride solution is 10-20 mL, and the amount of the sodium citrate solution is 2-5 mL, based on the weight of 5 g of the sample to be measured.

[0028] By using the combination of the copper sulfate solution, the EDTA-2Na solution, the ferric chloride solution and the sodium citrate solution, the release of (CN - ) is further improved, the loss of (CN - ) in the distillate is further reduced, and the accuracy of cyanide measurement is improved.

[0029] In a preferred embodiment, in step S3, the concentration of the phosphoric acid is 1.6-1.7 g / mL, and the amount is 10 mL.

[0030] In a preferred embodiment, in step S4, the distillate is heated and distilled at a speed of 2 mL / min-4 mL / min.

[0031] In a preferred embodiment, in step S4, when the volume of the liquid in the receiving bottle is close to 10 times the volume of the sodium hydroxide solution, the distillation is stopped.

[0032] In a preferred embodiment, in step S5, the spectrophotometry includes isonicotinic acid-pyrazolone spectrophotometry.

[0033] A desulfurizer for cyanide determination in a cyanide determination method, the desulfurizer comprising a copper sulfate solution and an EDTA-2Na solution; wherein the concentration of the copper sulfate solution is 200 mg / L, and the concentration of the EDTA-2Na solution is 100 g / L; the amount of the copper sulfate solution is 5-20 mL, and the amount of the EDTA-2Na solution is 10-20 mL, based on the weight of 5 g of the sample to be measured, and the content of sulfur in the sample to be measured is 1 ug / g-1.5 ug / g.

[0034] For the amount of the copper sulfate solution, the shielding effect on sulfides and the change in pH after addition need to be considered comprehensively, so that the copper sulfate solution is used as little as possible while meeting the shielding effect on sulfides.

[0035] For the EDTA-2Na solution, more (CN - ) needs to be released as much as possible to reduce the loss of (CN - ) in the distillate; therefore, the amount of EDTA-2Na should be increased as much as possible, but when the amount of EDTA-2Na cannot be increased to further improve the release of (CN -When the content of the copper sulfate solution and the EDTA-2Na solution is increased, the amount of EDTA-2Na is increased, which results in waste of resources.

[0036] The concentration and amount of the copper sulfate solution and the EDTA-2Na solution are set as above, so that the sulfides are shielded, more (CN - ) is released, and waste of resources is avoided.

[0037] In a preferred mode, the amount of the copper sulfate solution is 5-10 mL, and the amount of the EDTA-2Na solution is 15-20 mL, based on 5 g of the sample to be tested.

[0038] In a preferred mode, the desulfurizing agent further comprises a ferric chloride solution and a sodium citrate solution, the concentration of the ferric chloride solution is 50 g / L, and the concentration of the sodium citrate solution is 10 g / L; the amount of the ferric chloride solution is 10-20 mL, and the amount of the sodium citrate solution is 2-5 mL, based on 5 g of the sample to be tested.

[0039] The amount of the ferric chloride solution and the sodium citrate solution is also based on the purpose of releasing more (CN - ) and reducing the loss of (CN - ) in the distillate, the above amount of the ferric chloride solution and the sodium citrate solution can release more (CN - ), and waste of resources is avoided.

[0040] In a preferred mode, the amount of the ferric chloride solution is 10-15 mL, and the amount of the sodium citrate solution is 2-5 mL, based on 5 g of the sample to be tested.

[0041] A desulfurizing system comprises a desulfurizing agent for cyanide determination, and further comprises a sodium hydroxide solution, phosphoric acid and water.

[0042] The desulfurizing agent for cyanide determination or the desulfurizing system is applied to cyanide determination of solid waste with a sulfur content of greater than or equal to 1 ug / g.

[0043] The solid waste comprises powdery solid and block solid.

[0044] The process of pretreatment of the powdery solid before testing is as follows: sodium bicarbonate and quartz powder are added to the sample to be tested, and then the sample is crushed and sieved.

[0045] The process of pretreatment of the block solid before testing is as follows: the block solid is first crushed to obtain particles, and then sodium bicarbonate and quartz powder are added to the sample to be tested, and then the sample is crushed and sieved.

[0046] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0047] 1. The application is based on the characteristics of high sulfur concentration in the sample, and adopts the combination of copper sulfate solution and EDTA-2Na solution, and limits the concentration and dosage of copper sulfate solution and EDTA-2Na solution, which can realize the desulfurization shielding of sulfur to cyanide determination, reduce the loss of (CN - ), and improve the accuracy of cyanide determination of samples with high sulfur concentration.

[0048] 2. By adopting the combination of copper sulfate solution, EDTA-2Na solution, ferric chloride solution and sodium citrate solution, compared with the combination of copper sulfate solution and EDTA-2Na solution, the cyanide detection amount in the measurement distillate liquid added with ferric chloride solution and sodium citrate solution is higher when the same sample is measured. BRIEF DESCRIPTION OF DRAWINGS

[0049] The drawings described herein are used to provide further understanding of the embodiments of the application, constitute a part of the application, and do not constitute a limitation on the embodiments of the application. In the drawings:

[0050] Figure 1 The picture of the sample with high concentration of sulfide used in the embodiments of the application is shown in the figure, and each sample is numbered as 1#, 2#,..., 28# from bottom to top and from left to right, wherein 1-20# is an iron oxide desulfurizer, and 21-28# is a coke desulfurizer. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the following will be further described in detail, the schematic embodiment and its description are only used to explain the present application, and do not constitute a limitation on the present application, the following described embodiments are part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the scope of protection of the present application.

[0052] In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, it is apparent to those skilled in the art that the specific details need not be used to practice the present application. In other embodiments, in order to avoid confusion of the present application, well-known structures, materials or methods are not specifically described. The materials, instruments and reagents used in the following embodiments, etc. can be obtained from commercial channels if not otherwise specified. The technical means used in the embodiments, if not otherwise specified, are conventional means known to those skilled in the art.

[0053] In addition, the terms "first", "second", "third", etc. are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an ordered ranking of the indicated technical features. Thus, features defined with "first", "second" or "third" can explicitly or implicitly include one or more of such features. In the description of the present application, the meaning of "a plurality" is two or more, unless otherwise expressly and specifically defined.

[0054] Embodiments:

[0055] A cyanide determination method, comprising the following steps:

[0056] S1, pretreatment of the sample to be tested; the solid waste used by the sample to be tested includes powdery solid and massive solid; the process of pretreatment before testing of the powdery solid is: adding sodium bicarbonate and quartz powder to the sample to be tested, and then crushing and sieving; the process of pretreatment before testing of the massive solid is: first crushing to obtain particles, and then adding sodium bicarbonate and quartz powder to the sample to be tested, and then crushing and sieving with a mesh size of 16; the mass ratio of the sample to be tested to sodium bicarbonate and quartz powder is 1:0.2:1.

[0057] S2, setting up a distillation device: connecting a distillation flask and a receiving flask by a pipeline, and filling 10 mL of sodium hydroxide solution with a concentration of 10 g / L into the 100 mL receiving flask as an absorption liquid.

[0058] S3, after adding the sample to be tested into the distillation flask, specifically, taking 5 g of the sample to be tested after step S1 as a test sample, first adding 200 mL of water and 10 mL of sodium hydroxide solution with a concentration of 10 g / L to adjust the system to be alkaline, and then adding copper sulfate solution and EDTA-2Na solution; then adding 10 mL of phosphoric acid with a concentration of 1.6-1.7 g / L, and covering the plug.

[0059] Among them, the concentration of copper sulfate solution is 200 mg / L, and the concentration of EDTA-2Na solution is 100 g / L; based on the weight of 5 g of the sample to be tested, the amount of copper sulfate solution is 5-20 mL, the amount of EDTA-2Na solution is 10-20 mL, and the content of sulfur in the sample to be tested is 1 ug / g -1.5 ug / g.

[0060] Preferably, the iron chloride solution and the sodium citrate solution are added at the same time as the copper sulfate solution and the EDTA-2Na solution are added, wherein the concentration of the iron chloride solution is 50 g / L, and the concentration of the sodium citrate solution is 10 g / L; based on the weight of 5 g of the sample to be tested, the amount of the iron chloride solution is 10-20 mL, and the amount of the sodium citrate solution is 2-5 mL.

[0061] Preferably, the amount of copper sulfate solution is 5-10 mL, and the amount of EDTA-2Na solution is 15-20 mL, based on the weight of 5 g of the sample to be measured.

[0062] Preferably, the amount of iron chloride solution is 10-15 mL, and the amount of sodium citrate solution is 2-5 mL, based on the weight of 5 g of the sample to be measured.

[0063] S4, heating distillation; the distillate is subjected to heating distillation at a speed of 2 mL / min~4 mL / min, when the sample in the receiving bottle is about 100 ml, the distillation is stopped, a small amount of water is used to flush the distillate pipe, then the receiving bottle is taken out, and the sample in the receiving bottle is diluted with water to a constant volume. The sample in the receiving bottle is an absorption solution containing distillate, which is used for measuring the cyanide content in the subsequent method.

[0064] S5, the absorption solution containing distillate is used to measure the cyanide content by isonicotinic acid-pyrazolone spectrophotometry.

[0065] In this embodiment, the copper sulfate solution used in the desulfurization system reacts with sulfides in the sample to shield the sulfides from affecting the measurement of cyanide. The EDTA-2Na solution, iron chloride solution and sodium citrate solution are used to reduce the loss of copper sulfate solution to (CN - ), so as to increase the content of (CN - ) in the distillate, and thus improve the accuracy of cyanide measurement in solid waste. The desulfurizer designed in this embodiment is particularly suitable for the determination of cyanide in solid waste with a sulfur content of greater than or equal to 0.5 ug / g.

[0066] In order to better illustrate the technical effect of this embodiment, the following specific cases are used for illustration.

[0067] Example 1:

[0068] In order to compare and analyze the shielding effect of cadmium carbonate, silver nitrate and copper sulfate on sulfides when measuring cyanide in solid waste with different sulfur contents, the following experiments are performed:

[0069] 5 g of the sample to be measured is added to the distillation flask, wherein, experiments 1-3 come from the same sample 9#, experiments 4-6 come from the same sample 10#, and experiments 7-8 come from the same sample 11#. The actual samples of 9#, 10# and 11# are shown in Figure 1For each experiment, three parallel samples were tested, and the absorbance was measured and averaged. First, 200 mL of water and 10 mL of 10 g / L sodium hydroxide solution were added to adjust the system to alkaline pH. Then, 10 mL of copper sulfate solution, cadmium carbonate solution, or silver nitrate solution (the concentration of cadmium carbonate or silver nitrate solution was the same as that of copper sulfate solution) and 10 mL of EDTA-2Na solution were added. Next, 10 mL of 1.6-1.7 g / L phosphoric acid was added. The system was then stoppered and distilled. The sulfur content in the distillation flask was measured before and after adding the desulfurizing agent. The results are shown in Table 1.

[0070] Table 1

[0071]

[0072] Note: In Table 1, when using lead acetate test paper to test the liquid system in the distillation flask after distillation, the absence of white indicates that sulfur was not detected, and the sulfur content after distillation does not need to be measured. When the lead acetate test paper changes color, it indicates that sulfur was detected, meaning that the corresponding desulfurizing agent could not completely remove the sulfur. The sulfur content after distillation can be further measured, or the sulfur content after distillation can be omitted.

[0073] Note: Since samples 1-22# of this invention are all derived from desulfurizing agents, the sulfur content in samples with the same number may vary depending on the adsorption properties of the desulfurizing agent. However, this does not affect the measurement, because the purpose of this invention is not to verify the accuracy of spectrophotometry in measuring the sulfur content in samples, but to determine the effect of different desulfurizing agents on removing sulfur from samples. Table 1 can also be used for qualitative detection simply by checking whether the lead acetate test paper changes color.

[0074] The data in Table 1 shows that:

[0075] When the sulfur content in the sample is low, copper sulfate solution, cadmium carbonate solution, and silver nitrate solution can all remove sulfur. However, when the sulfur content in the sample is high, cadmium carbonate solution and silver nitrate solution cannot effectively remove sulfur and have limited shielding effect on sulfur during cyanide measurement. Even by increasing the amount of cadmium carbonate solution and silver nitrate solution, sulfur cannot be completely removed. In contrast, copper sulfate solution can effectively remove sulfur in samples with both low and high sulfur content.

[0076] Therefore, copper sulfate must be used as a desulfurizing agent when measuring cyanide in high-concentration sulfur samples.

[0077] Example 2:

[0078] In this embodiment, to verify the effect of the amount of copper sulfate solution added on the sulfur removal of the sample and to determine the minimum amount of copper sulfate solution to be added, experiments 1-2 were conducted using the same sample 9#, experiments 3-4 using the same sample 15#, and experiments 5-6 using the same sample 10#. Three parallel samples were tested for each experiment, and the absorbance was measured and averaged. The testing procedure was the same as in Example 1. The results are shown in Table 2.

[0079] Table 2

[0080]

[0081] As shown in Table 2:

[0082] Even with just 5 mL of copper sulfate added, the distillate from a sample with a very high sulfide content showed no reaction with lead acetate test paper. This means that adding 5 mL or more of copper sulfate solution effectively removes sulfur from the sample. However, as the amount of copper sulfate solution added increases, the amount of cyanide consumed by copper sulfate needs to be considered. Therefore, when copper sulfate reacts with sulfides, it also consumes cyanide ions. Specifically, besides precipitating sulfides, copper sulfate also undergoes a displacement reaction, reacting with stable cyanides to generate more volatile copper cyanide complex ions ([Cu(CN)3)3). 2- This could be due to an excess of Cu. 2+ It may react with other anions in the solution (such as phosphate PO4). 3- This process forms slightly soluble copper phosphate salts or precipitates. These newly formed tiny precipitates or colloidal particles have a large specific surface area and high surface energy, and strongly adsorb cyanide ions (CN-1,2-dicyandiamide) from the solution. - The presence of copper sulfate or copper cyanide complex ions can lead to incomplete cyanide release. Therefore, the present invention sets the amount of copper sulfate solution to 5-20 mL, taking into account that the sulfur content in some samples may be higher than 1 ug / g. This embodiment is based on the sulfur content in the sample being tested being 1 ug / g - 1.5 ug / g, and sets the amount of copper sulfate solution to 5-20 mL.

[0083] Example 3:

[0084] Copper sulfate is a salt of a strong acid and a weak base. If added before distillation, the pH of the solution should be carefully considered. In particular, copper sulfate used for impurity removal is a near-saturated solution (200 mg / L) with a pH of around 3. Therefore, adding copper sulfate will cause the distillate to become acidic, leading to the release of cyanide. Table 3 shows the cyanide determination results for different samples (samples 1#, 8#, 22#, and 28#) after adding 10 mL of copper sulfate and allowing them to stand for different times.

[0085] Table 3

[0086]

[0087] As shown in Table 3:

[0088] Although the cyanide leaching levels varied among different samples, they all showed a decreasing trend. Therefore, the distillation flask needed to be sealed immediately after adding copper sulfate solution to prevent the leached cyanide from causing cyanide ions (CN). - )loss.

[0089] Example 4:

[0090] Five g samples were taken from three different samples (0901 (9#), 1201 (12#), and 2801 (28#)) for spiking experiments. The distillation process was the same as in Example 1 to verify whether there was a good recovery rate. The results are shown in Table 4.

[0091] Table 4

[0092]

[0093] As shown in Table 4:

[0094] Although the spiked recoveries of the samples were in a low range, they were still acceptable.

[0095] Example 5:

[0096] To better illustrate the application effect of this embodiment, the following experiment was conducted. The soil samples to be tested were pretreated according to the sample pretreatment in the above embodiment to ensure uniformity of sulfide and cyanide content in the samples, thus achieving good homogeneity of samples taken from different batches. 5g samples were taken from each batch, and the sulfur content of each experiment was tested. All samples were around 1.2 ug / g, indicating high sulfur content, and the samples were uniform. The effects of adding different amounts of DETA-2Na solution, stannous chloride solution, ferric chloride solution, and sodium citrate solution on the cyanide measurement in the distillate were verified with the addition of 10mL of copper sulfate solution. The results are shown in Table 5.

[0097] Table 5

[0098]

[0099] Note: Each experiment in Table 5 measures two parallel samples, namely 001A and 001B, which are two parallel sample tests performed for the experiment in which 10 mL of DETA-2Na was added.

[0100] The data in Table 5 shows that:

[0101] 1) The distillation efficiency of cyanide using EDTA-2Na is better than that using stannous chloride. When using EDTA-2Na and stannous chloride together, the distillation efficiency is reduced compared to using EDTA-2Na or stannous chloride alone. This means that for samples with high sulfur content, stannous chloride and EDTA-2Na cannot play a synergistic role.

[0102] 2) Increasing the amount of EDTA-2Na used results in an increase in absorbance, indicating that increasing the amount of EDTA-2Na can improve distillation efficiency to some extent. Therefore, in order to ensure the accuracy of cyanide concentration measurement in the sample, the amount of EDTA-2Na used should be increased. However, when the amount of EDTA-2Na used is increased to 30 mL, the distillation efficiency does not improve significantly. Therefore, the amount of EDTA-2Na solution used should be 10-20 mL.

[0103] 3) Adding EDTA-2Na solution, ferric chloride solution and sodium citrate solution simultaneously improves distillation efficiency compared to using EDTA-2Na or ferric chloride or sodium citrate solution alone. The amount of ferric chloride solution used is 10-20 mL, and the amount of sodium citrate solution used is 5-7 mL, which have a good synergistic effect with EDTA-2Na solution.

[0104] 4) Adding EDTA-2Na solution and ferric chloride solution simultaneously improves distillation efficiency compared to using EDTA-2Na, ferric chloride, or sodium citrate solution alone, but the improvement in distillation efficiency is far less than that of adding EDTA-2Na solution, ferric chloride solution, and sodium citrate solution simultaneously.

[0105] Example 6:

[0106] To verify the effect of different pretreatment methods on the homogeneity of soil samples, the following experiment was conducted:

[0107] 30g of soil sample to be tested was pretreated according to the sample pretreatment method in the above embodiment. Then, three 5g samples were taken and labeled A1, A2, and A3. 30g of soil sample to be tested was directly pulverized and sieved through a 16-mesh sieve. Then, three 5g samples were taken and labeled B1, B2, and B3. The sulfur content of the sample before adding the desulfurizing agent and the cyanide content after distillation were measured respectively. The cyanide content detection refers to the desulfurizing agent numbered 001 in Example 4. The results are shown in Table 6.

[0108] Table 6

[0109]

[0110] The data in Table 6 shows that:

[0111] Compared with conventional methods, the sample pretreatment method of the present invention has a better mixing effect.

[0112] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for determining cyanide, characterized by, The method comprises the following steps: S1, pretreatment of the sample to be measured; S2, setting up a distillation device: connecting a distillation flask and a receiving flask through a pipeline, and loading sodium hydroxide solution as an absorption liquid in the receiving flask; S3, after adding the sample to be measured in the distillation flask, first adding water and sodium hydroxide solution to adjust the system to be alkaline, and then adding copper sulfate solution and EDTA-2Na solution; then add phosphoric acid, cover the plug; wherein the concentration of the copper sulfate solution is 200 mg / L, the concentration of the EDTA-2Na solution is 100 g / L; the amount of copper sulfate solution is 5-20 mL, the amount of EDTA-2Na solution is 10-20 mL, based on the weight of 5 g of the sample to be measured, and the content of sulfur in the sample to be measured is 1 ug / g-1.5 ug / g; S4, heating distillation; S5, measuring the content of cyanide in the absorption liquid containing the distillate by spectrophotometry; In step S3, the iron chloride solution and the sodium citrate solution are added at the same time as the copper sulfate solution and the EDTA-2Na solution are added, wherein the concentration of the iron chloride solution is 50 g / L, and the concentration of the sodium citrate solution is 10 g / L; the amount of the iron chloride solution is 10-20 mL, and the amount of the sodium citrate solution is 2-5 mL, based on the weight of 5 g of the sample to be measured.

2. The cyanide determination method according to claim 1, characterized by, In step S1, the pretreatment process is: Add sodium bicarbonate and quartz powder to the sample to be measured, then crush and process, and sieve.

3. The cyanide determination method according to claim 1, characterized by, In steps S2 and S3, the concentration of the sodium hydroxide solution is 10 g / L.

4. The cyanide determination method according to claim 1, characterized by, In step S3, the concentration of the phosphoric acid is 1.6-1.7 g / mL, and the amount is 10 mL.

5. The cyanide determination method according to claim 1, characterized by, In step S4, the distillate is heated and distilled at a speed of 2 mL / min-4 mL / min.

6. The cyanide determination method according to claim 1, characterized by, In step S4, when the volume of the liquid in the receiving flask is close to 10 times the volume of the sodium hydroxide solution, stop distillation.

7. The cyanide determination method according to any one of claims 1 to 6, characterized in that, In step S5, the spectrophotometry includes isonicotinic acid-pyrazolone spectrophotometry.

8. A desulfurizer for cyanide measurement for use in the cyanide measurement method according to any one of claims 1 to 7, characterized by, The desulfurizer comprises copper sulfate solution and EDTA-2Na solution; wherein the concentration of the copper sulfate solution is 200 mg / L, the concentration of the EDTA-2Na solution is 100 g / L; the amount of the copper sulfate solution is 5-20 mL, and the amount of the EDTA-2Na solution is 10-20 mL, based on the weight of 5 g of the sample to be measured, and the content of sulfur in the sample to be measured is 1 ug / g-1.5 ug / g; the desulfurizer further comprises iron chloride solution and sodium citrate solution, the concentration of the iron chloride solution is 50 g / L, and the concentration of the sodium citrate solution is 10 g / L; the amount of the iron chloride solution is 10-20 mL, and the amount of the sodium citrate solution is 2-5 mL, based on the weight of 5 g of the sample to be measured.

9. The desulfurizer for cyanide determination according to claim 8, characterized by The amount of the copper sulfate solution is 5-10 mL, and the amount of the EDTA-2Na solution is 15-20 mL, based on the weight of 5 g of the sample to be measured.

10. The desulfurizer for cyanide determination according to claim 9, characterized by The amount of the iron chloride solution is 10-15 mL, and the amount of the sodium citrate solution is 2-5 mL, based on the weight of 5 g of the sample to be measured.

11. A desulfurization system comprising the desulfurizer for cyanide measurement according to any one of claims 8 to 10, characterized by The desulfurizer for cyanide determination further comprises sodium hydroxide solution, phosphoric acid, and water.

12. Use of the desulfurizing agent for cyanide determination according to any one of claims 8 to 10 or the desulfurizing system according to claim 11 in cyanide determination of solid waste with sulfur content of 1 ug / g or more.

13. Use according to claim 12, characterized in that, The solid waste includes powdered solid and block solid.

14. Use according to claim 13, characterized in that, The pretreatment process of the powdered solid before testing is adding sodium bicarbonate and quartz powder to the sample to be tested, then crushing and sieving.

15. The use according to claim 13, characterized in that, The pretreatment process of the block solid before testing is first crushing to obtain particles, then adding sodium bicarbonate and quartz powder to the sample to be tested, then crushing and sieving. The pretreatment process of the block solid before testing is first crushing to obtain particles, then adding sodium bicarbonate and quartz powder to the sample to be tested, then crushing and sieving.

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