阅读说明：本技术 高氯高盐废水中低浓度重金属元素的测定方法 (Method for determining low-concentration heavy metal elements in high-chlorine high-salt wastewater ) 是由 程龙军 彭娟 吉飞 温炎燊 郑晓凤 马千里 于 2020-05-13 设计创作，主要内容包括：本发明提供一种高氯高盐废水中低浓度重金属元素的测定方法,包括：以高氯高盐废水为样品,将样品分成若干份；在若干份样品中加入酸进行消解,并用乙酸钠溶液转移并定容以得到若干份待测样品；在若干份样品中分别加入混合标准溶液,加入酸进行消解,并用乙酸钠溶液转移并定容以得到若干份加标样品；对待测样品和加标样品分别进行固相萃取,并收集洗脱液；通过光谱法测定待测样品和加标样品相应的洗脱液中待测重金属元素的含量。本发明提供的测定方法能够对高氯高盐废水中低浓度的重金属元素进行测定,测定结果具有较好的准确度和精密度,且不影响测试仪器的使用寿命。(The invention provides a method for determining low-concentration heavy metal elements in high-chlorine high-salt wastewater, which comprises the following steps: dividing a sample into a plurality of parts by taking high-chlorine high-salt wastewater as the sample; adding acid into a plurality of samples for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of samples to be detected; respectively adding the mixed standard solution into a plurality of samples, adding acid for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of standard-added samples; respectively carrying out solid phase extraction on a sample to be detected and a labeled sample, and collecting eluent; and measuring the content of the heavy metal element to be measured in the corresponding eluent of the sample to be measured and the standard sample by a spectrum method. The determination method provided by the invention can be used for determining the low-concentration heavy metal elements in the high-chlorine high-salt wastewater, and the determination result has better accuracy and precision and does not influence the service life of a testing instrument.)

1. A method for determining low-concentration heavy metal elements in high-chlorine high-salt wastewater comprises the following steps:

dividing a sample into a plurality of parts by taking high-chlorine high-salt wastewater as the sample;

adding acid into a plurality of samples for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of samples to be detected; respectively adding the mixed standard solution into a plurality of samples, adding acid for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of standard-added samples;

respectively carrying out solid phase extraction on a sample to be detected and a labeled sample, and collecting eluent;

and measuring the content of the heavy metal element to be measured in the corresponding eluent of the sample to be measured and the standard sample by a spectrum method.

2. The method of claim 1, wherein the solid phase extraction column is prepared by selecting iminodiacetic acid-based chelating resin as a solid phase extraction material, and the pH value of the solid phase extraction is controlled by using 2mol/L sodium acetate solution as a buffer system.

3. The method according to claim 1, characterized in that the step of solid phase extraction comprises in particular: the method comprises the steps of performing column activation by using an ammonium acetate solution, extracting a sample, performing first leaching by using the ammonium acetate solution, performing second leaching by using ultrapure water, and performing elution by using a nitric acid solution.

4. The method of claim 3, wherein the optimized conditions for solid phase extraction are: the pH value is 5-7, the extraction flow rate is 0.8 ml/min-1.5 ml/min, and the concentration of the elution nitric acid solution is 5% -10%.

5. The method of claim 4, wherein the method further comprises: preparing a sodium chloride solution with 10% of chloride ion content and a standard solution thereof, and measuring the content of heavy metal elements in the eluent after solid-phase extraction by using an ICP-MS method to obtain the optimized condition of the solid-phase extraction.

6. The method of claim 1, wherein the heavy metal elements comprise one or more of copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), and cadmium (Cd).

7. The method according to claim 6, wherein the mixed standard solution is a nitric acid solution with 100mg/L of each element to be measured and 10% of mass fraction.

8. The method of claim 7, wherein the content of each heavy metal element to be measured in the eluate corresponding to the sample to be measured and the spiked sample is determined by an ICP-OES method.

9. The method of claim 8, wherein the ICP-OES operating parameters are: the RF power was 1.2kW, the argon flow rate was 15.0L/min, the pump speed was 6rpm, the detection wavelength of cadmium was 214.439nm, the detection wavelength of nickel was 231.604nm, the detection wavelength of zinc was 206.200nm, the detection wavelength of copper was 327.395nm, and the detection wavelength of lead was 220.353 nm.

Technical Field

The invention relates to the technical field of wastewater detection, in particular to a method for determining low-concentration heavy metal elements in high-chlorine high-salt wastewater.

Background

At present, methods for detecting heavy metals in water and wastewater mainly comprise a photometric method, an electrochemical method, a spectroscopic method (including an atomic absorption method, an ICP-OES method, an ICP-MS method) and the like. The photometric method mainly aims at respectively carrying out color development and then measuring on single elements, cannot simultaneously measure the single elements, and is relatively complex to operate; the electrochemical method needs to use a mercury electrode, and mercury belongs to a highly toxic substance; the high-salt matrix has serious matrix background interference on the spectrometry, and a high-salt matrix sample easily blocks a sample introduction system pipeline of the spectrometry, so that the sensitivity of elements to be detected is reduced, and the service lives of related instrument parts, such as an ICP-OES or ICP-MS atomizer, an isoplast torch tube, a cone and the like, are shortened.

Disclosure of Invention

In view of the above, it is necessary to provide a method for determining low concentration heavy metal elements in high chlorine and high salt wastewater to solve the above problems.

The embodiment of the invention provides a method for determining low-concentration heavy metal elements in high-chlorine high-salt wastewater, which comprises the following steps:

dividing a sample into a plurality of parts by taking high-chlorine high-salt wastewater as the sample;

adding acid into a plurality of samples for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of samples to be detected; respectively adding the mixed standard solution into a plurality of samples, adding acid for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of standard-added samples;

respectively carrying out solid phase extraction on a sample to be detected and a labeled sample, and collecting eluent;

and measuring the content of the heavy metal element to be measured in the corresponding eluent of the sample to be measured and the standard sample by a spectrometry method.

Further, iminodiacetic acid type chelating resin is selected as a solid phase extraction material to prepare a solid phase extraction column, and 2mol/L sodium acetate solution is used as a buffer system to control the pH value of solid phase extraction.

Further, the solid phase extraction step specifically comprises: the method comprises the steps of performing column activation by using an ammonium acetate solution, extracting a sample, performing first leaching by using the ammonium acetate solution, performing second leaching by using ultrapure water, and performing elution by using a nitric acid solution.

Further, the optimized conditions of the solid phase extraction are as follows: the pH value is 5-7, the extraction flow rate is 0.8 ml/min-1.5 ml/min, and the concentration of the elution nitric acid solution is 5% -10%.

Further, the method further comprises: preparing a sodium chloride solution with 10% of chloride ion content and a standard solution thereof, and measuring the content of heavy metal elements in the eluent after solid-phase extraction by using an ICP-MS method to obtain the optimized condition of the solid-phase extraction.

Further, the heavy metal elements include one or more of copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), and cadmium (Cd).

Further, the mixed standard solution is a nitric acid solution with the content of each element to be detected being 100mg/L and the mass fraction being 10%.

Further, the content of the heavy metal elements to be detected in the corresponding eluent of the sample to be detected and the standard sample is determined by an ICP-OES method.

Further, the operating parameters of ICP-OES are as follows: the RF power was 1.2kW, the argon flow rate was 15.0L/min, the pump speed was 6rpm, the detection wavelength of cadmium was 214.439nm, the detection wavelength of nickel was 231.604nm, the detection wavelength of zinc was 206.200nm, the detection wavelength of copper was 327.395nm, and the detection wavelength of lead was 220.353 nm.

The method for determining the heavy metal elements in the high-chlorine high-salt wastewater comprises the steps of firstly digesting and carrying out solid-phase extraction on the high-chlorine high-salt wastewater, and then determining the content of the heavy metal elements in an eluent by a spectrum method. The method can automatically perform solid phase extraction operation through equipment, can realize separation and enrichment of elements to be detected, and has certain advantages particularly for detection of five heavy metal elements with low concentration content in high-chlorine high-salt wastewater. The method has the advantages that the measuring result has good accuracy and precision, the defect that the sample of the high-salt base sample is easy to block the pipeline of the sample injection system of the spectroscopy instrument is overcome, and the service life of the testing instrument is not influenced.

Drawings

Fig. 1 is a flowchart of a method for determining heavy metal elements in high-chlorine high-salt wastewater according to an embodiment of the present invention.

Fig. 2 is a schematic structural diagram of a solid phase extraction column according to an embodiment of the present invention.

FIG. 3 is a graph of adsorption pH versus recovery for spiking in accordance with an embodiment of the present invention.

FIG. 4 is a diagram showing the relationship between the concentration of the eluting nitric acid solution and the content of the element to be detected according to one embodiment of the present invention.

FIG. 5 is a graph of extraction flow rate versus spiking recovery in accordance with one embodiment of the present invention.

Description of the main elements

Solid phase extraction column 10

Column 11

A first filter plate 12

Second filter plate 13

Detailed Description

In order that the above objects, features and advantages of the present invention can be more clearly understood, the present invention will be described in detail below with reference to specific embodiments. In addition, the embodiments and features of the embodiments of the present application may be combined with each other without conflict.

In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention, and the described embodiments are merely a subset of the embodiments of the present invention, rather than a complete embodiment. 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.

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. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The invention provides a method for determining heavy metal elements in high-chlorine high-salt wastewater, in the embodiment, the high-chlorine high-salt wastewater contains low-concentration heavy metal elements, for example, the concentration of the heavy metal elements can be less than 0.1 mg/L; the heavy metal elements to be measured include one or more of copper (Cu), nickel (Ni), zinc (Zn), lead (Pb) and cadmium (Cd).

Referring to fig. 1, a method for determining heavy metal elements in high-chlorine high-salt wastewater according to an embodiment of the present application includes the following steps.

S1: sample preparation: the high-chlorine high-salt wastewater is taken as a sample, and the sample is divided into a plurality of parts.

The upper limit of the content of chloride ions in the high-chlorine high-salt wastewater is up to 10%, the high-chlorine high-salt wastewater can be sodium chloride-containing wastewater, ammonium chloride-containing wastewater or sodium chloride and ammonium chloride-containing wastewater, and the parts of the samples to be divided can be determined according to actual conditions.

S2: sample digestion: adding acid into a plurality of samples for digestion, transferring by using a sodium acetate solution and fixing the volume to obtain a plurality of samples to be detected; and respectively adding the mixed standard solution into a plurality of samples, adding acid for digestion, transferring by using sodium acetate solution and fixing the volume to obtain a plurality of standard-added samples.

In the present embodiment, the high-chlorine high-salt wastewater is sodium chloride-containing wastewater.

Specifically, 25ml of high-chlorine high-salt wastewater is measured and placed in a beaker, an electric heating plate is adjusted to 350 ℃, the wastewater is heated and boiled to 10 ml-15 ml in volume, 10ml of concentrated nitric acid is added for heating and micro-boiling for 5min, acid is removed to be nearly dry at 250 ℃, a proper amount of water is added after cooling to completely dissolve precipitated salt, acid is removed to be nearly dry at 250 ℃, sodium acetate solution with the concentration of 2mol/L is used for transferring after cooling and fixing the volume to 25ml, and a sample to be detected is obtained. Wherein, the standard adding sample can be added with a certain volume of mixed standard solution after the high-chlorine high-salt wastewater sample is added into the beaker, and then the digestion is carried out according to the digestion steps.

Wherein the preparation steps of the sodium acetate solution are as follows: 164g of sodium acetate (guaranteed reagent) is weighed, water is added for dissolution, the pH value is adjusted to 6.5 by acetic acid (guaranteed reagent), and the volume is adjusted to 1000 mL.

S3: solid phase extraction: and respectively carrying out solid phase extraction on the sample to be detected and the labeled sample, and collecting the eluent.

Specifically, iminodiacetic acid type chelating resin (Chelex, 100-200 meshes) is selected as a solid phase extraction material to prepare a solid phase extraction column, and a sodium acetate solution (2mol/L) is used as a buffer system to control the pH value of solid phase extraction.

When preparing the solid phase extraction column, washing the iminodiacetic acid type chelating resin for 3 times, sucking the mixed solution of the resin and water by an injector, and injecting the mixed solution into the solid phase extraction empty column until the resin is filled in the extraction small column.

Referring to fig. 2, the solid phase extraction column 10 includes a column 11, and a first filter plate 12 and a second filter plate 13 respectively disposed at two sides of the column 11. The cylinder 11 is substantially in the shape of a truncated cone, and the first filter plate 12 and the second filter plate 13 are both cylindrical

In one embodiment, the height of the column 11 is 12mm, the diameter of the first filter plate 12 is 10mm, the diameter of the second filter plate 13 is 9mm, and the resin filling amount is 0.2 g.

Before use, the solid-phase extraction column 10 is rinsed with 10ml of 5% nitric acid solution to ensure that no heavy metal ions to be detected remain in the solid-phase extraction column 10, and then the solid-phase extraction operation is performed according to the following steps of table 1. As shown in table 1, the solid phase extraction procedure specifically included: the method comprises the steps of performing column activation by using an ammonium acetate solution, extracting a sample, performing first leaching by using the ammonium acetate solution, performing second leaching by using ultrapure water, and performing elution by using a nitric acid solution.

Wherein, the optimized conditions of the solid phase extraction are as follows: the pH value is 5-7, the extraction flow rate is 0.8 ml/min-1.5 ml/min, and the concentration of the elution nitric acid solution is 5% -10%. Wherein the extraction flow rate is any value of 0.8ml/min to 1.5ml/min, for example, 0.8ml/min, 0.9ml/min, 1ml/min, 1.1ml/min,1.2ml/min, 1.3ml/min, 1.4ml/min, 1.5ml/min, etc. The concentration of the nitric acid solution to be eluted is any value of 5% to 10%, for example, 5%, 6%, 7%, 8%, 9%, 10%, or the like. The flow rate of the eluted nitric acid solution can be the same as the extraction flow rate, and in a preferred embodiment, the extraction flow rate is 1ml/min, and the concentration of the eluted nitric acid solution is 5%.

After the extraction operation is completed, the next extraction of the sample solution may be performed, and so on.

TABLE 1 solid phase extraction procedure

Serial number	Step (ii) of	Reagent/sample	Volume of
				1	Column activation	Ammonium acetate solution	5ml
2	Sample extraction	Sample solution	10ml
				3	Leaching 1	Ammonium acetate solution	5ml
4	Leaching 2	Ultrapure water	10ml
				5	Elution is carried out	Nitric acid solution	10ml

Wherein the preparation steps of the ammonium acetate solution are as follows: 38.5g of ammonium acetate (guaranteed reagent) is weighed, dissolved in water and added to 1000mL of water.

In table 1, the volume of the nitric acid eluting solution is the same as the volume of the extraction sample, but is not limited thereto, and the enrichment of the element to be measured can be achieved by adjusting the ratio of the volume of the extraction sample to the volume of the nitric acid eluting solution.

S4: content determination: and measuring the content of the heavy metal element to be measured in the corresponding eluent of the sample to be measured and the standard sample by a spectrum method.

In one embodiment, the content of the element to be measured is determined by the ICP-OES method. In other embodiments, the content of the test element may be measured by an ICP-MS method or an atomic absorption method.

In one embodiment, the contents of copper (Cu), nickel (Ni), zinc (Zn), lead (Pb), and cadmium (Cd) are simultaneously measured by the ICP-OES method. The ICP-OES working parameters are as follows: the RF power is 1.2kW, the argon flow rate is 15.0L/min, the pump speed is 6rpm, the reading time is 3s, the number of readings is 3, the cadmium detection wavelength is 214.439nm, the nickel detection wavelength is 231.604nm, the zinc detection wavelength is 206.200nm, the copper detection wavelength is 327.395nm, and the lead detection wavelength is 220.353 nm.

According to the method for determining the heavy metal elements in the high-chlorine high-salt wastewater, provided by the embodiment of the invention, the high-chlorine high-salt wastewater is firstly subjected to digestion and solid-phase extraction, and then the content of the heavy metal elements in an eluent is determined by a spectrometry method. The method can automatically perform solid phase extraction operation through equipment, can realize separation and enrichment of target elements to be detected, and has certain advantages particularly for detection of low concentration content ranges of five heavy metal elements in high-chlorine high-salt wastewater. The method can be used for simultaneously measuring five heavy metal elements, and has high testing efficiency. The method has the advantages that the measuring result has good accuracy and precision, the defect that the sample of the high-salt base sample is easy to block the pipeline of the sample injection system of the spectroscopy instrument is overcome, and the service life of the testing instrument is prolonged.

In one embodiment, the method for determining heavy metal elements in high-chlorine high-salt wastewater further comprises the following steps: preparing a sodium chloride solution with 10% of chloride ion content and a standard solution thereof, and measuring the content of heavy metal elements in the eluent after solid-phase extraction by using an ICP-MS method to obtain the optimized condition of solid-phase extraction.

The ICP-MS analysis conditions were He mode, RF power 1550W, sampling depth 9mm, atomization gas flow rate of 1.05L/min, pump speed of 0.1rpm, compensation gas flow rate of 0L/min, atomization chamber temperature of 2 ℃, and collision cell He flow rate of 5 ml/min. The mass number, integration time, and internal standard selection of each analytical element are shown in table 2.

TABLE 2 selection table of mass number, integration time, and internal standard of each analysis element

Analytical elements	Ni	Cu	Zn	Cd	Pb
						Analysis of mass number	60	63	66	111	208
Integration time(s)	0.1	0.1	0.2	0.1	0.1
						Internal standard element and mass number	70Ge	70Ge	70Ge	103Rh	185Re

Specifically, 14 parts of sodium chloride solution (2mol/L sodium acetate buffer system) containing 10% of chlorine are taken, wherein 7 parts of sodium chloride solution are added with 0.1mg/L of standard, the pH is adjusted by nitric acid, the flow rate of the fixed solid phase extraction is 1ml/min, the concentration of the elution nitric acid is 5%, the content of each element in each eluent is measured by ICP-MS, the influence of different pH values on the solid phase extraction effect is examined, and the measurement result is shown in figure 3. As can be seen from FIG. 3, the recovery rate of each element is more than 95% when the adsorption pH value is in the range of 5-7, so that the optimum adsorption pH value is determined to be in the range of 5-7.

4 parts of 10% chlorine-containing sodium chloride solution (2mol/L sodium acetate buffer system) were taken and the pH was adjusted to 6.5 with nitric acid, the amount added being 0.1 mg/L. The flow rate of the fixed solid phase extraction was 1ml/min, and the elution was carried out with nitric acid of various concentrations, and the concentration of each eluate was measured by ICP-MS, and the measurement results are shown in FIG. 4. As can be seen in fig. 4: when the concentration of the elution nitric acid reaches 5% or more, the concentration of each element is not greatly changed, so that the concentration of the elution nitric acid is determined to be more than 5%, and preferably, the concentration of the elution nitric acid is 5% -10%.

Taking 8 parts of sodium chloride solution (2mol/L sodium acetate buffer system) containing 10% of chlorine, adjusting the pH value to 6.5 by using nitric acid, fixing the concentration of the eluting nitric acid to be 5%, measuring the content of each element by using ICP-MS, observing the adding standard recovery rate conditions under different flow rates, and obtaining the calculation result shown in figure 5. As can be seen from fig. 5: the normalized recovery of each element decreases with increasing flow rate. When the flow rate of the solid phase extraction is 0.8 ml/min-1.5 ml/min, the standard recovery rate of the solid phase extraction of each element under the condition can reach more than 95 percent, thereby determining that the flow rate of the solid phase extraction is 0.8 ml/min-1.5 ml/min. Wherein, when the flow rate of the solid phase extraction is 1ml/min, the standard recovery rate of the solid phase extraction of each element under the condition can reach more than 97.5 percent.

It is to be understood that in the above embodiment, the adjustment of the pH is not limited to the use of nitric acid, and other solutions may be used.

Table 3 is a summary table of the optimized conditions of the solid phase extraction, and the flow rates corresponding to different rotation speeds of different peristaltic pumps or pump tubes can be measured, and then the rotation speed and time can be set according to the required flow rate.

TABLE 3 summary of solid phase extraction optimization conditions

The solubility of sodium chloride in sodium acetate buffer solution is about 12.5% calculated as Cl, the upper limit of the content of chloride ions is determined to be 10%, and the lower limit of the content of chloride ions is determined to be 1%; the content of chloride ion less than 1% can be directly measured by ICP-OES.

Preparing 25ml of solution with the chlorine content of 10% and the element content of 10mg/L by using a sodium chloride solution (the Cl ion content is 15%) and a mixed standard solution in a beaker, wherein the mixed standard solution is a nitric acid solution with the element content to be detected of 100mg/L and the mass fraction of 10%. The acid was heated to almost dryness, cooled and transferred to 25ml with sodium acetate buffer. Solid-phase extraction was performed under the optimized conditions for solid-phase extraction, and ICP-OES was used to determine the contents of each element in the eluate, the results of which are shown in Table 4.

TABLE 410 results (unit: mg/L) of standard solution (Cl content 10%) after solid-phase extraction

Serial number	Ni	Cu	Zn	Cd	Pb
						1	8.71	9.93	10.80	9.36	8.51
2	8.62	9.78	10.66	9.28	8.47
						Average	8.66	9.85	10.73	9.32	8.49

As can be seen from the measurement results shown in Table 4, the measurement results of each element in the eluate were all greater than 8mg/L, and the upper limit of the measurement of each element by this method was determined to be 8 mg/L.

The following describes a method for measuring heavy metal elements in high-chlorine high-salt wastewater provided by the present application by embodiments.