CN111337488B - Method for measuring soil cyanide and total cyanide - Google Patents

Abstract

The invention discloses a method for measuring soil cyanide and total cyanide, which comprises the steps of adjusting the pH value of a soil sample to be alkaline, preparing an impurity-free soil sample, and quantitatively weighing a soil sample; and distilling the soil sample, collecting distillate by using the absorption liquid, and determining by using a continuous flow analyzer to obtain the concentration of cyanide or total cyanide in the soil. The method for measuring the total cyanide content of the soil by adopting the distillation of the soil sample and the measurement of the continuous flow analyzer can eliminate interference, avoid damaging the instrument, is safer for detection personnel, is favorable for protecting analysis equipment from being damaged, and has more efficient detection work. The method has the advantages that the soil sample with more standardized characteristics can be obtained by adopting treatments such as low-temperature drying, electrostatic adsorption and sieving, the influence of metal impurities and organic impurities on the measurement result is avoided, the soil is adjusted to be alkaline before drying, cyanide does not overflow in the low-temperature drying process, and the precision and the accuracy of the detection result are fully ensured.

Description

Method for measuring soil cyanide and total cyanide

Technical Field

The invention belongs to the technical field of environmental detection, and relates to a method for determining cyanide, in particular to a method for determining total cyanide in soil and a method for determining cyanide in soil.

Background

Cyanide refers to a compound containing a cyano group (-CN) in the molecule of the compound, and belongs to a highly toxic compound.

Total cyanide refers to the sum of organic cyanide, free cyanide ion, complex and simple metal cyanide. Cyanide complexes of cobalt and thiocyanide are excluded. Free cyanide refers to the sum of free cyanide ions and simple metal cyanides, excluding organic cyanides.

Mainly HCN, CN in the environment^-And in the form of a complex cyanide ion. Human activities such as gold production, electroplating chemical industry, organic chemical industry and other industries bring a large amount of cyanide-containing wastewater; causing great harm to ecological environments such as water, soil and the like. Therefore, in environmental monitoring, it is very important to measure the cyanide concentration.

In the laboratory analysis process, the determination method of cyanide in soil generally adopts an isonicotinic acid-pyrazolone spectrophotometry, and specifically adopts the spectrophotometry to perform colorimetric determination on distillate after soil pre-distillation.

In the process of implementing the invention, the inventor finds that at least the following problems exist in the prior art:

1. in the spectrophotometric method, phosphoric acid is added during color development, and for a high-content cyanide solution, virulent hydrogen cyanide is easily generated in the operation process and overflows a colorimetric tube, so that great harm is caused to the health of an analyst;

2. the colorimetric determination is carried out by adopting a spectrophotometry, the color development is carried out by completely adopting a manual method in the colorimetric process, 3 reagents are required to be added during the color development, and the operation is complicated;

3. colorimetric determination is carried out by spectrophotometry. The water bath needs 40min when the sample is developed, and the developing time is longer.

4. In the prior art, the detected soil samples are all fresh samples, and the uniformity of the fresh soil samples cannot be guaranteed during sampling, for example, the fresh soil samples have different soil water contents, so that the detection accuracy of the method is influenced.

Disclosure of Invention

In view of the above, the present invention aims to provide a safe, convenient and efficient method for determining soil cyanide and/or total cyanide.

The inventor provides a technical scheme for solving the technical problems by continuously reforming and innovating through long-term exploration and trial and a plurality of experiments and endeavors, and the method for measuring the soil cyanide and the total cyanide comprises the following steps:

step 1) adjusting the pH value of a soil sample to be alkaline, preparing an impurity-free soil sample, and quantitatively weighing a soil sample;

step 2), distilling the soil sample, and collecting distillate by using absorption liquid to obtain a solution A;

step 3), fixing the volume of the solution A to obtain a solution B;

and 4) using the solution B in the step 4) for determination by a continuous flow analyzer to obtain the concentration of cyanide or total cyanide in the soil.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in the present invention, in the step 1), the preparation of the soil sample without impurities is specifically: collecting soil, drying at low temperature, pulverizing soil sample, removing organic impurities in the soil sample by electrostatic adsorption, and sieving with 16 mesh sieve.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in the present invention, in the step 2), the step of distilling the soil sample comprises: distilling with a distilling device, sequentially adding soil sample, water, stannous chloride solution and copper sulfate solution into a distilling flask, and mixing uniformly; adding phosphoric acid quickly and then covering the stopper immediately; and (3) carrying out gradient heating on the distillation flask, condensing the distillate, and collecting the distillate by using an absorption liquid for measuring the total cyanide.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in the present invention, the soil sample distillation comprises the following specific steps: distilling with a distilling device, sequentially adding soil sample, distilled water, 50g/L stannous chloride solution and 200g/L copper sulfate solution into a distilling flask, and mixing uniformly; 1.69g/ml phosphoric acid is added rapidly, and the stopper is covered immediately; and (3) carrying out gradient heating on the distillation flask for 5-30min until the distillation flask is boiled, condensing the distillate, and collecting the distillate by using an absorption liquid for measuring the total cyanide.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in the present invention, the soil sample distillation comprises the following specific steps: distilling with a distilling device, sequentially adding 10.00g of soil sample, 200ml of distilled water, 2.0ml of stannous chloride solution and 10ml of copper sulfate solution into a 500ml distilling flask, and uniformly mixing; quickly adding 10ml of phosphoric acid, and immediately covering a stopper; and (3) carrying out gradient heating on the distillation flask, heating for 10-15min until the distillation flask is boiled, condensing the distillate, and collecting the distillate by using an absorption liquid for measuring the total cyanide.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in the present invention, the soil sample distillation comprises the following specific steps: distilling with a distilling device, sequentially adding a soil sample, distilled water, a zinc nitrate solution and a copper sulfate solution into a distilling flask, dropwise adding methyl orange, and uniformly mixing; rapidly adding tartaric acid until the solution keeps red, and immediately capping; and (3) carrying out gradient heating on the distillation flask, heating for 10-15min until the distillation flask is boiled, condensing the distillate, and collecting the distillate by using an absorption liquid for cyanide determination.

According to a preferred embodiment of the method for measuring soil cyanide and total cyanide of the present invention, the distillation rate of the distillate is 2ml/min to 4 ml/min.

According to an alternative embodiment of the method for determining soil cyanide and total cyanide according to the present invention, sodium hydroxide solution is added to the soil sample, and the pH is not lower than 12.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide of the present invention, when the volume of the solution a is 90 to 97ml, the distillation is stopped; washing the distillate catheter with 2-3ml of distilled water, and taking out the receiving bottle; the volume of the solution B is 100ml, and the solution is distilled water.

According to a preferred embodiment of the method for determining soil cyanide and total cyanide in accordance with the present invention, the absorption solution is 10ml of 10g/L sodium hydroxide solution.

According to a preferred embodiment of the method for the determination of soil cyanide and total cyanide according to the present invention, the continuous flow analyzer is seaalaa 3.

Compared with the prior art, one of the technical solutions has the following advantages:

a) in one embodiment of the method for measuring the soil cyanide and the total cyanide, the total cyanide content of the soil is measured by adopting a soil sample distillation and continuous flow analyzer, so that the interference can be eliminated, the instrument is prevented from being damaged, the method is safer for detection personnel, the analysis equipment is protected from being damaged, and the detection work is more efficient.

b) In one embodiment of the method for measuring the soil cyanide and the total cyanide, the soil sample with standardized characteristics can be obtained by adopting low-temperature drying, electrostatic adsorption, sieving and other treatments, the influence of metal impurities and organic impurities on the measurement result is avoided, the soil is adjusted to be alkaline before drying, the cyanide does not overflow in the low-temperature drying process, and the precision and the accuracy of the detection result are fully ensured.

c) In one embodiment of the method for determining the soil cyanide and the total cyanide, stannous chloride, copper sulfate, phosphoric acid and the like are used as reaction solutions, and the reaction solutions are gradually heated in a gradient manner, so that the chemical reaction is more sufficient, and the total cyanide can be fully distilled.

d) In one embodiment of the method for measuring soil cyanide and total cyanide, 10g/L sodium hydroxide solution is used as a receiving solution, so that the color reaction is more favorably carried out under the test condition, and the precision and the accuracy of the measurement result are not influenced.

e) In one embodiment of the method for measuring soil cyanide and total cyanide of the invention, the continuous flow analyzer is selected from SEAALAA 3, and AA3 colorimeter with 10mm flow cell and 600nm filter to make the measurement work smooth.

f) The detection limit of the method for measuring the soil cyanide and the total cyanide is 0.01mg/kg and is lower than that of the national environmental protection standard 'spectrophotometry for measuring the soil cyanide and the total cyanide' (HJ745-2015) (the detection limit is 0.04mg/kg), which indicates that the method has high sensitivity.

g) The invention provides a method for measuring soil cyanide and total cyanide, which is different from a national environmental protection standard measuring method, and provides a brand new idea for measuring the cyanide and the total cyanide in soil. In the existing standard detection method, 2.5mol/L sodium hydroxide solution is used for leaching for 16h in pretreatment, and the leaching solution is used for detection. The pretreatment time is obviously shortened, and the method has the characteristics of safety, high efficiency, high precision and high accuracy, and has practical value.

Detailed Description

The following description will be given with reference to specific examples.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail and completely with reference to the accompanying drawings. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention. Thus, the following detailed description of embodiments of the invention is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention.

Example 1

Collecting soil, adjusting the pH value of a soil sample to be alkaline, preferably adding 1mol/L sodium hydroxide solution, and adjusting the pH value of the soil sample to be 12. After being adsorbed and dried at a low temperature of 4-30 ℃, the soil can be dried under the condition that the temperature is lower than the natural environment temperature within the range of 5 ℃, 10 ℃, 15 ℃, 20 ℃, 25 ℃, 30 ℃ and 4-30 ℃ to obtain a dry soil sample. Crushing the soil sample, picking out obvious impurities such as stones, metal particles, tree roots, plastic particles, fiber yarns and the like, removing organic impurity particles in the soil sample by using electrostatic adsorption, and sieving by using a 16-mesh sieve to obtain a soil sample for later use. Sieving to remove granular impurities in soil. The screened fine powdery soil sample can be more fully mixed with the reaction solution, so that the reaction is more fully performed.

10.00g of soil sample was accurately weighed into a distillation flask.

The distillation was performed using an all-glass distiller. Full glass distiller belongs to prior art, and this application is not innovated the distiller. Generally, a distiller includes a distillation flask, a condenser tube, a distillate conduit and a receiving flask, and a heating device, such as an adjustable electric furnace, for heating the distillation flask. The adjustable electric furnace with the maximum power of 800 watts is selected in the embodiment, and the adjustable electric furnace is also the conventional heating equipment. In the heating process, the temperature gradually rises from low grade to high grade, and the soil sample and the reaction liquid are ensured to be fully chemically reacted in the heating process. The distiller needs to be airtight, distillate can only enter the receiving bottle, liquid is condensed and flows into receiving liquid, and gas is collected by the receiving liquid.

The specific steps of soil sample distillation are as follows: distilling with a distilling device, sequentially adding 10.00g soil sample, 200ml distilled water, 2.0ml stannous chloride solution 50g/L and 10ml copper sulfate solution 200g/L into a 500ml distilling flask, and sufficiently shaking; quickly adding 10ml of 1.69g/ml phosphoric acid, and immediately plugging; heating the distillation flask in gradient for 5-30min, preferably 10-15min, in this example 10 min. And condensing the distillate, and collecting the distillate by using an absorption liquid, wherein the distillation rate of the distillate is 2-4 ml/min. When the volume of the liquid in the receiving flask was 97ml, the distillation was stopped. The distillate catheter was rinsed with 2ml of distilled water and the receiving vial was removed to give solution A. And finally, fixing the volume to 100ml to obtain a solution B, wherein the solution B is a solution to be detected and is used for detecting the total cyanide.

Or the soil sample distillation comprises the following specific steps: distilling with a distilling device, sequentially adding 10.00g of soil sample, 200ml of distilled water, 10ml of 100g/L zinc nitrate solution and 10ml of 200g/L copper sulfate solution into a 500ml distilling flask, dropwise adding methyl orange, and uniformly mixing; rapidly adding tartaric acid until the solution keeps red, and immediately capping; heating the distillation flask in gradient for 10-15min to boil, condensing the distillate, and collecting with absorption solution to obtain solution A. And finally, fixing the volume to 100ml to obtain a solution B, wherein the solution B is a solution to be detected and is used for detecting cyanide.

The receiving flask was charged with 10ml of 10g/L sodium hydroxide solution as a receiving solution.

Solution B was used for continuous flow measurements using SEAL AA3, AA3 colorimeter with a 10mm flow cell and 600nm filter, the pH of the distilled reagent was very important and was carefully adjusted to pH 3.8. Incorrect pH of the distillation reagent reduces the overall cyanide recovery. The test condition is in the range of 0-200 mug/L as CN^-And a colorimeter: 10mm, flow cell: 600nm, sample injection rate of 30L/h, sample injection: wash ratio 3:1, reagent uptake 0.01-0.02. Unlike the determination of total cyanide, the apparatus does not need to be opened to a UV digestor when determining cyanide. When detecting cyanide, 1% zinc sulfate solution is added into the solution B.

Reagent

1mol/L of sodium hydroxide solution, 0.4mol/L of sodium hydroxide solution, 1mol/L of hydrochloric acid, citric acid, water + polyoxyethylene lauryl ether Brij-35, 10g/L of zinc sulfate solution, potassium hydrogen phthalate buffer solution (pH adjusted to 5.2), chloramine-T solution (stabilized for one week), color developing agent (pH adjusted to 5.2, filtered before use, stabilized for 3 months), and distilled reagent (pH adjusted to 3.8).

Starting a cooling circulation tank, firstly turning on a power switch, and then turning on a refrigeration switch; turning on a distiller switch, and pressing an OK key to start heating; checking whether the pipeline connection is correct, covering a pump pressure plate, starting the pump and sucking the reagent.

And an ultraviolet digester of the total cyanide module and a power plug of the heater are plugged. When the cyanide is measured, the ultraviolet digestion device is closed.

Open the injector, detector switch, start software, click system window "chart" key to select and activate the channel window.

An analysis method or run is set. And clicking a stop key of the system window after the baseline of the channel window is stable, then clicking an operation key, selecting and starting to operate.

And (5) after the operation is finished, firstly, turning off the power supplies of the distiller, the total cyanide module ultraviolet digestor and the heater. And taking all the reagent pipelines out of the reagent bottle, wiping the tube wall or washing the tube wall with pure water, and then putting the tube wall into the pure water for washing for 5 minutes.

Then putting cyanide distilled reagent and water + Brij pipelines into pure water, putting other reagent pipelines into 1mol/L NaOH solution for 5 minutes, and then putting the reagent pipelines into the pure water for at least 30 minutes for cleaning.

Finally, all reagent pipelines are taken out from the pure water, the pump is adjusted to be fast, and the module is drained.

The pump power is turned off. And (4) taking down the pump pressure plate, loosening the plastic clamping strip of the right pump pipe, and putting the pump pressure plate at the original position.

And turning off the power supply of the sample injector and the detector, and turning off the power supply of the cooling circulation tank. And finishing the detection.

Soil samples from different sources were tested using the method.

TABLE 1 test of detection limit and lower limit of measurement

As can be seen from the results in Table 1, the detection limit of soil cyanide and total cyanide measured by this method was 0.01mg/kg, which was lower than that of "spectrophotometry for measuring soil cyanide and total cyanide" (HJ745-2015) (the detection limit of isonicotinic acid-pyrazolone spectrophotometry was 0.04mg/kg), indicating that this method is highly sensitive.

TABLE 2 precision measurement data

As can be seen from the results of table 2, the relative standard deviations of the soil total cyanide determinations in the present method were 10.3%, 7.8% and 4.0%, and the relative standard deviations of the soil cyanide determinations were 13.2%, 8.6% and 5.4%. Meets the requirements that the relative standard deviation of the total cyanide is less than 15 percent and the relative standard deviation of the cyanide is less than 25 percent in the spectrophotometry for measuring the soil cyanide and the total cyanide (HJ 745-2015).

Table 3: accuracy test data

As can be seen from the results in Table 3, the measured recoveries of soil total cyanide in the present method were 80.0%, 92.0% and 93.3%, and the measured recoveries of soil cyanide were 80.0%, 88.0% and 91.1%. The standard recovery rates of the total cyanide and the cyanide in the soil are controlled between 70% and 120% in the spectrophotometry for measuring the total cyanide and the soil (HJ 745-2015).

The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and the protection scope of the present invention should be subject to the scope defined by the claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and these modifications and adaptations should be considered within the scope of the invention.

Claims (7)

1. A method for measuring soil cyanide and total cyanide, which comprises a soil sample distillation step and a continuous flow analysis measurement step, and is characterized by comprising the following steps:

step 1) preparing an impurity-free soil sample: collecting soil, and adjusting the pH value of a soil sample to be alkaline, wherein the pH value is not lower than 12; adsorbing and drying at a low temperature of 4 ℃, crushing a soil sample, removing organic impurities in the soil sample by using electrostatic adsorption, sieving by using a 16-mesh sieve for later use, and quantitatively weighing a soil sample;

step 2), distilling the soil sample, and collecting distillate by using absorption liquid to obtain a solution A;

distilling with a distilling device, sequentially adding soil sample, distilled water, stannous chloride solution and copper sulfate solution into a distilling flask, and mixing uniformly; adding phosphoric acid quickly and then covering the stopper immediately; heating the distillation flask in gradient for 5-30min to boil, condensing the distillate, and collecting with absorption liquid for determination of total cyanide;

or distilling with a distilling device, sequentially adding the soil sample, distilled water, a zinc nitrate solution and a copper sulfate solution into a distilling flask, dropwise adding methyl orange, and uniformly mixing; rapidly adding tartaric acid until the solution keeps red, and immediately capping; heating the distillation flask in gradient for 10-15min to boil, condensing the distillate, and collecting with absorption liquid for cyanide determination;

step 3), fixing the volume of the solution A to obtain a solution B;

and 4) using the solution B in the step 4) for determination by a continuous flow analyzer to obtain the concentration of cyanide and/or total cyanide in the soil.

2. The method for determining soil cyanide and total cyanide in accordance with claim 1, wherein in step 2), the concentration of the stannous chloride solution is 50g/L, the concentration of the copper sulfate solution is 200g/L, and the concentration of the phosphoric acid is 1.69g/ml phosphoric acid.

3. The method for assaying soil cyanide and total cyanide according to claim 1, wherein the distillate has a distillation rate of 2ml/min to 4 ml/min.

4. The method for determining soil cyanide and total cyanide as claimed in claim 1, wherein the step of adjusting the pH of the soil sample to alkaline is carried out by adding sodium hydroxide solution into the soil sample.

5. The method for determining soil cyanide and total cyanide according to claim 1, wherein the distillation is stopped when the volume of the solution A is 90 to 97 ml; washing the distillate catheter with 2-3ml of distilled water, and taking out the receiving bottle; the volume of the solution B is 100ml, and the solution is distilled water.

6. The method for assaying soil cyanide and total cyanide according to claim 1, wherein the absorption solution is 10ml of 10g/L sodium hydroxide solution.

7. The method of claim 1, wherein the continuous flow analyzer is SEAL AA 3.