Method for measuring thallium in lead smelting slag through polyurethane foam plastic adsorption enrichment-inductively coupled plasma atomic emission spectrometry

Abstract

The invention relates to the technical field of analytical chemistry, and discloses a method for measuring thallium in lead smelting slag through polyurethane foam plastic adsorption enrichment-inductively coupled plasma atomic emission spectrometry. The preparation method comprises the following steps: putting a sample into a polytetrafluoroethylene beaker, sequentially adding hydrochloric acid, nitric acid, hydrofluoric acid, perchloric acid and sulfuric acid, heating and decomposing, after completely decomposing, adding aqua regia, heating and dissolving salts, adding water for diluting, dropwise adding bromine water into the solution until the solution is in stable light yellow, shaking uniformly, adding a piece of polyurethane foam plastic, carrying out vibration adsorption, taking out the foam plastic after adsorption, and drying to obtain the polyurethane foam plastic. The method comprises the following steps: washing with water, squeezing water, putting the foamed plastic into a test tube, adding a sulfurous acid-hydroquinone mixed solution for releasing, taking out the foamed plastic after releasing, uniformly shaking, and measuring on an inductively coupled plasma emission spectrum. The method is simple and rapid to operate, and has reference value in the fields of lead smelting slag analysis method standard formulation, standard sample development, environmental protection and the like.

Description

Technical Field

[0001] This invention relates to the field of analytical chemistry and discloses a method for determining thallium in lead smelting slag by polyurethane foam adsorption enrichment-inductively coupled plasma atomic emission spectrometry. Background Technology

[0002] Thallium has a wide range of uses and is a typical highly toxic heavy metal element. Its toxicity to humans exceeds that of mercury, cadmium, copper, and lead, posing a serious threat to human health. In the crude lead smelting process, thallium in lead ore is distributed throughout various stages of the process. With increasingly stringent environmental protection requirements, accurate determination of thallium content in lead smelting slag is essential. Currently, there are few reports on the determination of thallium in lead smelting slag in China; regarding standardization, no relevant national, industry, or local standards have been found. Literature in similar related fields (such as rocks, minerals, and soils) can be categorized by method as polarography, spectrophotometry, atomic absorption spectrometry, inductively coupled plasma atomic emission spectrometry (ICP-AES), and inductively coupled plasma mass spectrometry (ICP-MS). Among them, polarography and spectrophotometry have many interfering elements, are complex to operate, and are not easy to improve the testing efficiency; atomic absorption spectrometry is suitable for the determination of high thallium content, but graphite furnace atomic absorption spectrometry is required for trace thallium, and usually requires pre-separation and enrichment; although ICP-MS can determine multiple elements at the same time, the instrument is expensive; ICP-AES has fewer interferences and also has the ability to determine multiple elements at the same time, but the detection limit for thallium is high, and it is difficult to meet the detection requirements of low thallium content samples without pre-enrichment. Summary of the Invention

[0003] In view of this, this invention, targeting the elemental composition characteristics of lead smelting slag samples, first employs hydrofluoric acid to remove silicon and perchloric acid to remove carbon, then utilizes polyurethane foam to adsorb and enrich thallium, effectively separating and removing most interfering elements. This invention uses bromine water, with higher oxidizing power, as the oxidant to promote more complete and rapid oxidation of thallium, which is more conducive to the adsorption process. In the desorption stage, reductive desorption is performed to reduce Tl³⁺ to Tl⁺, using a sulfurous acid-hydroquinone mixed solution as the reducing agent. The desorption rate using the sulfurous acid-hydroquinone mixed solution as the desorption solution is significantly faster than that using nitric acid as the desorption solution. This invention is simple and rapid to operate, significantly reducing the detection limit of thallium, and has reference value in the fields of lead smelting slag analysis method standardization, standard sample development, and environmental protection.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for determining thallium in lead smelting slag by polyurethane foam adsorption enrichment-inductively coupled plasma atomic emission spectrometry, the method comprising the following steps: (1) Weigh a certain amount of lead smelting slag sample for later use; (2) Place the above sample in a polytetrafluoroethylene beaker, add hydrochloric acid, nitric acid, hydrofluoric acid, perchloric acid and sulfuric acid in sequence, and heat to decompose until white fumes are emitted; (3) After it cools slightly, add aqua regia and heat to dissolve the salts; (4) Transfer the solution to an Erlenmeyer flask, dilute with water, add bromine water dropwise to the solution until it turns a stable light yellow color, warm it, cool it to room temperature, and shake well; (5) Add a piece of polyurethane foam and vibrate it on the shaker; (6) Take out the foam plastic, rinse it with water, squeeze out the water, and place the foam plastic in a test tube; (7) Add sulfurous acid-hydroquinone mixed solution and decompose in a boiling water bath; (8) After removing the foam plastic, shake well; (9) The above-mentioned test solution was measured by inductively coupled plasma atomic emission spectrometry.

[0005] As can be seen from the above technical solutions, the method for determining thallium in lead smelting slag by adsorption enrichment-inductively coupled plasma atomic emission spectrometry using polyurethane foam disclosed in this invention has the following advantages compared with the prior art: (1) Hydrofluoric acid is used to remove silicon, perchloric acid is used to remove carbon, and then polyurethane foam is used to adsorb and enrich thallium, effectively separating and removing most of the interfering elements.

[0006] (2) Using bromine water, which has a higher oxidizing power, as an oxidant promotes more complete and rapid oxidation of thallium, which is more conducive to the adsorption process.

[0007] (3) In the decomposition process, the reduction decomposition is carried out for the reduction of Tl³⁺ to Tl⁺. A sulfurous acid-hydroquinone mixed solution is used as the reducing agent. The decomposition rate of the sulfurous acid-hydroquinone mixed solution as the decomposition liquid is also significantly faster than that of the decomposition rate of the nitric acid as the decomposition liquid.

[0008] (4) The combination of pre-enrichment and ICP-AES can meet the detection requirements of low-content thallium samples in lead smelting slag.

[0009] (5) The present invention is simple and quick to operate, and greatly reduces the detection limit of thallium. Detailed Implementation

[0010] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] This invention employs hydrofluoric acid to remove silicon and perchloric acid to remove carbon during sample decomposition, effectively separating and removing most interfering elements. It uses bromine water, with higher oxidizing power, as an oxidant to promote more complete and rapid oxidation of thallium, thus facilitating the adsorption process. A sulfurous acid-hydroquinone mixed solution is used as a reducing agent to improve the desorption rate, significantly lowering the detection limit of thallium. The detailed content of this application regarding the method for determining thallium in lead smelting slag using polyurethane foam adsorption enrichment-inductively coupled plasma atomic emission spectrometry is as follows: 1. Main instruments and working conditions ICAP-PRO Inductively Coupled Plasma Atomic Emission Spectrometer (Thermo Fisher Scientific, USA). ICP-AES operating conditions: RF power 1150 W; analytical pump speed 45 r / min; nebulizer gas flow rate 0.65 L / min; nebulizer gas pressure 0.48 MPa; auxiliary gas flow rate 0.50 L / min; cooling gas flow rate 12.5 L / min; analyte wavelength Tl 190.80 nm; horizontal observation mode.

[0012] 2. Main reagents and standard solutions Thallium single-element standard stock solution (National Center for Analysis and Testing of Nonferrous Metals and Electronic Materials): 1000 µg / mL, nitric acid medium; Thallium standard working solution: 20 µg / mL, prepared by stepwise dilution of thallium single-element standard stock solution, medium is sulfuric acid (1+19).

[0013] Ferric chloride solution: 25 g / L. Weigh 2.5 g of ferric chloride hexahydrate and dissolve it in 100 mL of hydrochloric acid (1+1) solution, then mix well. Decomposition solution: Weigh 0.5 g of hydroquinone and dissolve it in 100 mL of water. Add 5 mL of sulfurous acid solution and shake well. Prepare fresh before use.

[0014] Flexible polyurethane foam: Polyether-type flexible polyurethane foam conforming to the national standard GB / T 10802—2023 "General Flexible Polyurethane Foam" is used, with an open cell ratio greater than 5%. It is cut into 2 cm × 1.5 cm × 1.5 cm blocks, each weighing approximately 0.2 g. Two to three cuts are made in the middle of each foam block. Pretreatment includes rinsing with water, soaking in hydrochloric acid (1+9) for 1 hour, and finally rinsing with water and air-drying for later use.

[0015] All reagents used in the experiment were of analytical grade; the water used in the experiment was deionized water (resistivity not less than 18 MΩ·cm).

[0016] 3. Preparation of standard solution series Transfer 0, 0.25, 0.50, 1.00, 1.50, 2.00, 2.50, 5.00, and 10.00 mL of thallium standard working solution into a set of 250 mL Erlenmeyer flasks. Add 10 mL of aqua regia (1+1) and 2 mL of ferric chloride solution to each flask sequentially, and dilute with water to approximately 100 mL. Add bromine water dropwise until the solution turns a stable pale yellow color, warm for 10 min, and cool to room temperature. Then add the same amount of calcium salt as the sample matrix and shake well. Add a piece of polyurethane foam and shake on a shaker for 30 min. Remove the foam, rinse thoroughly with water, squeeze out excess water, and place it in a 25 mL test tube. Add 10.00 mL of descaling solution and incubate in a boiling water bath for 20 min. Remove the foam and shake the contents of the test tube well. Finally, a calibration curve was plotted with the mass concentration of thallium (0, 0.50, 1.0, 2.0, 3.0, 4.0, 5.0, 10, 20 µg / mL) as the abscissa and the corresponding emission spectral intensity as the ordinate.

[0017] 4. Experimental Methods Weigh 0.25 g (accurate to 0.0001 g) of sample and place it in a 50 mL polytetrafluoroethylene beaker. Add 15 mL hydrochloric acid, 5 mL nitric acid, 10 mL hydrofluoric acid, 2 mL perchloric acid, and 5 drops of sulfuric acid (1+1) sequentially. Heat the beaker on a hot plate at 350 °C until no white fumes are emitted. After slightly cooling, add 10 mL aqua regia (1+1) and heat to dissolve the salts. Transfer the solution to a 250 mL Erlenmeyer flask and dilute with water to approximately 100 mL. Add bromine water dropwise to the solution until a stable pale yellow color is achieved, warm for 10 min, then cool to room temperature and shake well. Add a piece of polyurethane foam and shake on a shaker for 30 min. Remove the foam, rinse thoroughly with water, squeeze out excess water, and place it in a 25 mL test tube. Add 10.00 mL of desiccant and maintain in a boiling water bath for 20 min. Remove the foam, shake well, and perform the determination under the selected instrument conditions.

[0018] 5. Sample Analysis 5.1 Precision Test According to the experimental method, the thallium in three lead smelting slag samples (numbered 1# to 3#) was measured nine times in parallel to examine the precision. The results are shown in Table 1.

[0019] Table 1. Precision test results of thallium in lead smelting slag samples (µg / g) Sample number Measurement 1 Measurement 2 Measurement 3 Measurement 4 Measurement 5 Measurement 6 Measurement 7 Measurement 8 Measurement 9 RSD / % 1# 19.6 20.0 18.3 19.4 18.8 18.2 19.5 20.6 19.4 4.0 2# 28.1 28.4 29.4 27.3 27.6 28.5 28.3 29.2 30.1 3.1 3# 36.5 36.1 34.8 35.2 37.6 37.9 36.5 36.5 39.1 3.6 5.2 Spiked Recovery Test Three lead smelting slag samples (numbered 1# to 3#) were selected and spiked for recovery tests according to this method. The results are listed in Table 2.

[0020] Table 2 Results of thallium recovery tests in lead smelting slag samples Sample number Sample mass / g Thallium background amount / µg Thallium addition scalar amount / µg Total thallium determination / µg Thallium recovery rate / % 1# 0.5000 9.65 10 19.82 101.7 2# 0.5000 14.25 10 23.80 95.5 3# 0.5000 18.35 10 27.97 96.2 5.3 Comparative Test Since it is currently impossible to verify the correctness of this method using standard samples of lead smelting slag, a method comparison test was conducted with reference to the inductively coupled plasma mass spectrometry (ICP-MS) method specified in GB / T14353.13—2014 "Chemical Analysis Methods for Copper, Lead and Zinc Ores - Part 13: Determination of Gallium, Indium, Thallium, Tungsten and Molybdenum Contents". The results are shown in Table 3. The results indicate that the determination results of this method are basically consistent with those of ICP-MS.

[0021] Table 3 Comparison of thallium determination results using this method and ICP-MS Sample number ICP-MS measured value (µg / g) The measured value by this method (µg / g) 1# 21.2 19.3 2# 27.7 28.5 3# 37.4 36.7 The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.

[0022] Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for determining thallium in lead smelting slag by polyurethane foam adsorption-enrichment-inductively coupled plasma atomic emission spectrometry, characterized in that, The method includes the following steps: (1) Weigh a certain amount of lead smelting slag sample for later use; (2) Place the above sample in a polytetrafluoroethylene beaker, add hydrochloric acid, nitric acid, hydrofluoric acid, perchloric acid and sulfuric acid in sequence, and heat to decompose until white smoke is emitted; (3) After cooling slightly, add aqua regia and heat to dissolve the salts; (4) Transfer the solution to an Erlenmeyer flask, dilute with water, add bromine water dropwise to the solution until it is a stable light yellow color, warm it, cool it to room temperature, and shake it well; (5) Add a piece of polyurethane foam and shake it on a shaker; (6) Take out the foam, rinse it with water, squeeze out the water, and place the foam in a test tube; (7) Add a sulfurous acid-hydroquinone mixed solution and decompose it in a boiling water bath; (8) Take out the foam after decomposition and shake it well; (9) Measure the above test solution using inductively coupled plasma atomic emission spectrometry.