Method for detecting the content of chromium in laterite nickel ore

Abstract

The application discloses a method for detecting the content of chromium in laterite nickel ore, and comprises the following steps: S1, nitric acid, phosphoric acid, perchloric acid and sulfuric acid are sequentially added into a to-be-detected sample of the laterite nickel ore, and the mixture is uniformly mixed to obtain a mixed solution A; S2, when the amount of the nitric acid is not 0, the mixed solution A is heated to remove water and the nitric acid, and then is heated again to remove the perchloric acid, so as to obtain a mixed solution C; when the amount of the nitric acid is 0, the mixed solution A is directly heated to remove water and the perchloric acid, so as to obtain the mixed solution C; S3, after the mixed solution C is cooled, water is added to dilute the mixed solution C, the mixed solution C is boiled again to dissolve salts, and after being cooled, the mixed solution C is filtered and diluted for standby, and is recorded as a mixed solution D; and S4, the mixed solution D is determined by ICP, and the content of the chromium in the laterite nickel ore is calculated. By means of the oxidation-reduction reaction of the nitric acid, the phosphoric acid, the perchloric acid and the sulfuric acid, and the determination by ICP, the problems of few test analysis methods, long detection time and complicated steps in the hydrometallurgy of the laterite nickel ore are solved.

Description

Technical Field

[0001] This invention relates to the field of chromium content detection, and specifically to a method for detecting chromium content in laterite nickel ore. Background Technology

[0002] With global economic development in the 1990s, nickel demand grew at an average annual rate of over 4% in the first five years, and is projected to grow at 3.5% to 4% over the next 5-10 years, with Asia's nickel demand growth rate expected to be 7%. However, the world's available nickel sulfide resources for near-term development are extremely limited. Globally, approximately 70 million tons of nickel metal reserves have been discovered to date. Laterite nickel resources are abundant, with 41 million tons globally, and exploration costs are low. With the maturation of processing techniques and the significant increase in demand, research on the detection of various target elements in laterite nickel ore has been steadily progressing in recent years, and a series of national and industry standards have been initially established.

[0003] Currently, the main sample pretreatment methods for analyzing various elements in laterite nickel ore include acid dissolution and alkali fusion. Detection methods include inductively coupled plasma atomic emission spectrometry (ICP-AES), atomic absorption spectrometry (AAS), inductively coupled plasma mass spectrometry (ICP-MS), and titration. Chromium, due to the stability of its natural compounds and the difficulty in reduction, has relatively limited detection methods, primarily relying on traditional manual titration analysis. This method demands a high level of expertise from personnel and also suffers from time-consuming and material-intensive issues, hindering future sustainable development. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a method for detecting chromium content in laterite nickel ore, thereby solving the technical problems of long detection time and cumbersome steps in the existing technology for detecting chromium content in laterite nickel ore.

[0005] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows:

[0006] In a first aspect, the present invention provides a method for detecting the chromium content in laterite nickel ore, comprising the following steps: S1, adding 0-5 mL of nitric acid, 1-10 mL of phosphoric acid, 1-10 mL of perchloric acid, and 1-10 mL of sulfuric acid sequentially to the laterite nickel ore sample to be tested, and mixing evenly to obtain a mixture A; S2, when the amount of nitric acid is not zero, heating the mixture A to remove water and nitric acid, obtaining a mixture B; then heating the mixture B to remove perchloric acid, obtaining a mixture C; or when the amount of nitric acid is zero, directly heating the mixture A to remove water and perchloric acid, obtaining a mixture C; S3, cooling the mixture C and diluting it with water, boiling it again to dissolve the salts, cooling it, filtering and diluting it for later use, and recording it as a mixture D; S4, determining the chromium content in the laterite nickel ore by ICP determination of the mixture D.

[0007] Compared with the prior art, the beneficial effects of the present invention include:

[0008] This invention selects and optimizes suitable detection methods, using redox reactions with nitric acid, phosphoric acid, perchloric acid, and sulfuric acid, combined with ICP for determination. This solves the problems of limited sample testing and analysis methods, long detection time, and cumbersome procedures in the hydrometallurgical process of laterite nickel ore. Detailed Implementation

[0009] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0010] For any dated references below, only the dated version applies to this invention; for any undated references, the latest version (including all amendments) applies to the method of this invention.

[0011] Unless otherwise specified, analytical grade reagents and distilled water, deionized water or water of equivalent purity are used in all analytical tests.

[0012] The existing detection methods involved in this invention:

[0013] (1) The chemical analysis method of laterite nickel ore, Part 21: determination of chromium content by ferrous ammonium sulfate titration method stipulates that the determination range is 0.3% to 3.5%. Under repeatability conditions, the absolute difference between the two test results obtained from independent test results shall not exceed the repeatability limit r within the average value range, and the cases exceeding the repeatability limit r shall not exceed 5%.

[0014] (2) The "Determination of Chromium Content by Ferrous Ammonium Sulfate Titration Method" stipulates that the allowable difference is ≤0.4% when the chromium content (mass fraction) is ≥97%.

[0015] (3) According to the "Soil Testing Part 12: Determination of Total Chromium in Soil", the relative difference between repeated test results is allowed to be ≤8%.

[0016] The present invention provides a method for detecting the chromium content in laterite nickel ore, comprising the following steps:

[0017] S1, Digestion of laterite nickel ore sample: Add 0-5 mL of nitric acid, 1-10 mL of phosphoric acid, 1-10 mL of perchloric acid, and 1-10 mL of sulfuric acid to each 0.1 g laterite nickel ore sample, shake well, and obtain mixture A;

[0018] S2, when the amount of nitric acid is not 0, the mixture A is heated on a hot plate to remove water and nitric acid, and the mixture B is obtained; the mixture B is then heated to remove perchloric acid, and kept warm until the perchloric acid fumes are completely removed, and the mixture C is obtained.

[0019] When the amount of nitric acid is 0, mixture A is placed on a hot plate and heated directly to remove water and perchloric acid, resulting in mixture C;

[0020] S3, after removing mixture C from the hot plate and cooling it to room temperature, add a small amount of water and boil it again to dissolve the salts. After cooling to room temperature, filter and dilute to volume in a volumetric flask, then dilute for later use. This mixture is called mixture D.

[0021] S4, the chromium content in the laterite nickel ore is obtained by ICP determination (selecting standard curve points according to the content) and then calculation.

[0022] Preferably, the particle size of the laterite nickel ore sample to be tested is less than 160 μm. It is dried in an oven at 105℃~110℃ for 2 hours, and then cooled to room temperature in a desiccator before use.

[0023] The laterite nickel ore samples to be tested included samples with low chromium content (0.0007% ≤ M). Cr <4%), medium chromium content samples (4% ≤ M) Cr <25%) and high chromium content samples (25% ≤ M) Cr ≤50%); In step S1:

[0024] When the laterite nickel ore sample to be tested is a low chromium content sample, add 0 mL of nitric acid, 2-10 mL of phosphoric acid, 1-3 mL of perchloric acid and 2-10 mL of sulfuric acid per 0.1 g of sample to be tested.

[0025] When the laterite nickel ore sample is of medium chromium content, add 1-5 mL of nitric acid, 5-10 mL of phosphoric acid, 4-8 mL of perchloric acid, and 5-10 mL of sulfuric acid per 0.1 g of sample.

[0026] When the laterite nickel ore sample to be tested is a high-chromium sample, add 1-5 mL of nitric acid, 5-10 mL of phosphoric acid, 5-10 mL of perchloric acid, and 5-10 mL of sulfuric acid per 0.1 g of the sample to be tested.

[0027] Preferably, the concentrations are as follows: perchloric acid is 12.44 mol / L; nitric acid is 13 mol / L; phosphoric acid is 14.63 mol / L; and sulfuric acid is 18 mol / L.

[0028] Preferably, in step S2, when the amount of nitric acid is not 0, mixture A is heated to 200-250°C and kept at that temperature for 5-30 minutes; mixture B is heated to 300-350°C and kept at that temperature for 15-90 minutes.

[0029] Preferably, in step S2, when the amount of nitric acid is 0, the mixture A is heated to 300-350°C and kept at that temperature for 15-40 minutes until the perchloric acid fumes are completely emitted.

[0030] If the heating and holding time is too short, the reaction will be incomplete; if the time is too long, pyrophosphate will be generated, both of which will reduce the accuracy.

[0031] Preferably, in step S3, the ratio of water added to the laterite nickel ore sample to be tested in step S1 is 20-40 mL: 0.1 g; and the boiling time is 1-2 min.

[0032] Preferably, in step S3, the mass concentration of mixture D is 0.0007%-50%. More preferably, if the concentration of mixture D is high, for example, exceeding 50%, then mixture D needs to be diluted to ensure that it can be detected by the instrument. The dilution is specifically to take a portion of mixture D and then make up to volume to obtain mixture E. For example, take 5 ml of mixture D and make up to volume in a 100 ml volumetric flask, with a dilution factor of 20 times. The concentration of mixture E (the final test solution) should be between 0.0007% and 50%.

[0033] Preferably, the ICP parameter settings are shown in Table 1 below.

[0034] Table 1 ICP Parameter Settings

[0035]

[0036] Note: The standard curve uses 2% 1:1 sulfur-phosphoric acid mixture as the medium.

[0037] Because the mixture D contains a large amount of sulfate and phosphate, which can easily cause blockage and equipment shutdown, it is necessary to reduce atomization (carrier gas), increase detection power, and increase cooling gas protection equipment. These measures should be combined to work together to complete the detection.

[0038] Preferably, step S4 specifically includes: under given conditions, obtaining a standard curve of chromium (linearity greater than 0.999) by testing a chromium standard solution; under the same testing conditions, obtaining the concentration value of mixed solution D by testing mixed solution D; and finally, calculating the sample content value.

[0039] The standard curve is obtained by inputting the known values ​​of each point of the chromium standard solution, measuring the intensity value of each point sequentially through ICP, plotting the concentration on the x-axis and the intensity on the y-axis, and then plotting a standard curve through all the points; when the sample to be tested (mixture D) is measured, there will be a corresponding intensity value, and the instrument will automatically calculate the concentration value through the standard curve.

[0040] Formula for calculating chromium content in laterite nickel ore:

[0041] Cr (%) = C * D * V / (10000 * m);

[0042] C: The measured concentration of mixture D (mg / L)

[0043] D: Dilution factor (the dilution factor is 1 when testing mixture D).

[0044] V: Volume at constant volume (mL)

[0045] m: Sample mass (g).

[0046] Main mechanism of action of this invention:

[0047] This invention utilizes nitric acid, phosphoric acid, sulfuric acid, and perchloric acid for redox reactions. The formulation of this invention eliminates the need for hydrochloric acid or hydrofluoric acid, avoiding adverse digestion of the sample due to their reducing properties. Furthermore, this invention treats high-chromium samples because their structure is stable and difficult to reduce; therefore, a strong oxidizing agent is used for oxidation determination, saving time.

[0048] The present invention will be further described in detail below through specific embodiments and comparative examples.

[0049] Experimental sample:

[0050] (1) Laterite nickel ore: purchased from Zhejiang Qingshan Iron & Steel Co., Ltd.

[0051] (2) National Class I standard reference material, chromite composition analysis standard reference material GBW(E)070135, was purchased from Wuhan Ruichen Standard Material Technology Co., Ltd.

[0052] (3) National Class I standard reference material, nickel ore and nickel concentrate composition analysis standard reference material GBW(E)070116, was purchased from Jinan Zhongbiao Technology Co., Ltd.

[0053] The sample particle size should be less than 160 μm. Dry it in an oven at 105℃~110℃ for 2 hours, then cool it to room temperature in a desiccator before use.

[0054] Example 1

[0055] Weigh 0.1000g (±0.0001g) of sample into a 250mL hard conical flask. Rinse the flask wall with a small amount of water. Add 5mL of phosphoric acid, 2mL of nitric acid, 5mL of perchloric acid, and 5mL of sulfuric acid in sequence. Shake well and heat the mixture on a hot plate to 250℃ to remove water and nitric acid. Then heat the mixture to 350℃ to remove perchloric acid until the perchloric acid fumes are completely removed. Remove from heat and cool to room temperature. Add a small amount of water (about 30mL) and boil again for 1min to dissolve the salts. After cooling, dilute to a 250mL volumetric flask for later use. Analyze the sample content using ICP or atomic absorption spectrometry. Calculate the sample content value.

[0056] Detection limit, accuracy and repeatability:

[0057] The method of this invention was performed, with 12 consecutive blank determinations, and the detection limit was calculated using 3 times the standard deviation. The detection limits for each element are shown in Table 2 (the blank result is the lowest detectable value).

[0058] Accuracy (ΔlgC) and repeatability were calculated by continuously measuring 12 times with a national standard reference GBW(E)070135 (which has a standard value and can be used to calculate accuracy and repeatability), and repeatability was calculated by continuously measuring 12 times with an experimental sample (which has no standard value and can only be used to measure repeatability). The results are shown in Table 2.

[0059] Titration test: The national standard material GBW(E)070135 was titrated using the method of "Chemical Analysis Methods for Laterite Nickel Ore Part 21: Determination of Chromium by Ferrous Ammonium Sulfate Titration". The results are shown in Table 2 below.

[0060] Table 2. Detection Limit, Accuracy, and Reproducibility Data

[0061]

[0062]

[0063] As can be seen from Table 2, compared with titration test, the results of the special treatment process of the present invention combined with ICP test are slightly lower. This is mainly because, relatively speaking, the results of human intervention are more stable than those of instrument test. However, the accuracy and repeatability of the results measured by the method of the present invention are within the specifications of the method.

[0064] Standard requirements

[0065] Referring to GB / T 223.11-2008 "Determination of Chromium Content in Iron and Steel and Alloys - Visual Titration or Potentiometric Titration Method", standard solutions with known chromium content were tested, and the results are shown in Table 3 below. As can be seen from Tables 2 and 3, the repeatability of this invention is better than that of the reference standard. Therefore, this method can meet production requirements.

[0066] Table 3 Repeatability and Reproducibility Requirements

[0067]

[0068] Example 2

[0069] The only difference from Example 1 is that the amount of acid and the reaction time are adjusted. All other steps and conditions are the same as in Example 1. The specific parameters and test results are shown in Table 4 below.

[0070] Table 4. Specific parameters and test results for Example 2

[0071]

[0072] The method of this invention can determine the chromium content based on the color (green) of the solution during digestion; the greener the solution, the more perchloric acid is needed. Alternatively, perchloric acid (1-10 mL) can be added based on the sample properties. Table 4 shows that for laterite nickel ore samples with low chromium content, only 1-3 mL of perchloric acid is needed, and nitric acid is not required. For chromium concentrate samples (a type of laterite nickel ore) with medium to high chromium content, more perchloric acid (4-10 mL) needs to be added. In all digestion processes, only 13-22 mL of acid is needed per 0.1 g of sample. The operation is simple, time-efficient (1-1.5 h), and has minimal interference. Table 2 also shows that the accuracy and repeatability of the determination results are within the standard specifications and meet production requirements.

[0073] As shown in Table 4 above, if the reaction time is too short, the reaction will not be completed for the high-content sample (GBW(E)070135), resulting in inaccurate test results. Similarly, sufficient reaction time must be allowed for nitric acid; therefore, the temperature should first be raised to 250℃ and held for 15–30 minutes before being raised to 350℃.

[0074] Comparative Example 1

[0075] The existing detection method was used, specifically as described in "Chemical Analysis Methods for Laterite Nickel Ore, Part 21: Determination of Chromium Content by Ferrous Ammonium Sulfate Titration". The sample was placed in a 30 mL corundum crucible containing 4 g of sodium peroxide, stirred thoroughly, and then covered with 1 g–2 g of sodium oxide. The crucible was first heated and calcined on a high-temperature electric furnace, then melted in a furnace at 750°C–800°C for 5 minutes, shaking once during the process. The crucible was removed and cooled, then placed in a 500 mL beaker. 100 mL–150 mL of hot water was added, and after the vigorous reaction ceased, sulfuric acid was added while stirring until the hydroxide precipitate dissolved, with an excess of 20 mL. 5 mL of phosphoric acid was added, and the crucible was washed out with water. The mixture was then heated to decompose the hydrogen peroxide. After cooling slightly, water was added to a volume of approximately 200 mL. 5 mL of silver nitrate solution, 0.5 mL of manganese sulfate solution, and 20 mL of ammonium persulfate solution were added, and the mixture was shaken well. After heating to a stable purplish-red color, continue boiling for 5 minutes. Add 10 mL of hydrochloric acid and continue boiling for another 5-10 minutes. Cool to room temperature under running water. Titrate with ferrous ammonium sulfate standard solution until the solution turns pale yellow. Add 3 drops of N-benzoic acid solution and continue titrating until the solution changes from rose-red to bright green, which is the endpoint. The process is cumbersome, time-consuming (2.5 hours), and requires highly skilled personnel.

[0076] Comparative Example 2

[0077] The existing detection method is used, specifically as described in "Soil Testing Part 12: Determination of Total Chromium in Soil". Weigh 0.5 g (accurate to 0.0001 g) of air-dried sample (passing through a 0.149 mm sieve) into a 100 mL tall beaker (or Erlenmeyer flask). Add a few drops of water to moisten the sample, add 1.5 mL of concentrated sulfuric acid, and gently shake well. Add 1.5 mL of concentrated phosphoric acid and 3 mL of nitric acid, and gently shake well again. Cover with a watch glass and place on a hot plate (surface temperature controlled below 220°C) to heat and digest until a large amount of white fumes are emitted. If the soil sample does not turn white at this point, remove the beaker and let it cool slightly. Add another 1 mL of nitric acid and continue heating until dense white fumes are emitted, until the soil sample turns white. Remove the beaker and cool. Rinse the watch glass and beaker walls with water. Transfer the contents of the beaker intact into a 50 mL volumetric flask, add water to the mark, shake well, and filter dry or allow to clarify or centrifuge. Perform a blank test simultaneously. Accurately pipette 5.00 mL of clear test solution into a 25 mL colorimetric tube, add 1-2 drops of potassium permanganate solution until a purple-red color appears, and boil in a water bath for 15 minutes. If the purple-red color fades, add another drop of potassium permanganate solution until the purple color persists, and shake well. While still hot, add sodium azide solution, and shake quickly and thoroughly until the purple-red color just disappears. Quickly cool the colorimetric tube in cold water, add 1 mL of phosphoric acid solution, shake well, and add water to the mark. Add 2 mL of diphenylcarbazide solution and shake quickly. After 5 minutes, use a 3 cm cuvette to measure the absorbance at a wavelength of 540 nm, adjusting the instrument's zero point using the zero concentration of the standard series solutions as a reference. This method also suffers from problems such as cumbersome process, long time consumption (3.5 hours), and numerous interferences.

[0078] Comparative Example 3

[0079] The existing detection method is used, specifically: In the "Determination of Chromium Content by Ferrous Ammonium Sulfate Titration Method," the sample is placed in a 500mL Erlenmeyer flask, 70mL of water, 12mL of sulfuric acid, and 5mL of phosphoric acid are added. The mixture is heated at low temperature until the sample is completely dissolved. The flask is then removed and diluted with water to approximately 200mL. 1-2mL of manganese sulfate solution is added, followed by 10mL of silver nitrate solution and 40mL of ammonium persulfate solution. The mixture is boiled to oxidize chromium to dichromic acid, resulting in a slightly reddish color resembling permanganate. Boiling continues for 5 minutes, producing large bubbles, to decompose excess ammonium persulfate. 10mL of sodium chloride solution is added, and the mixture is boiled to completely decompose the permanganate. Boiling continues for 2-3 minutes. The mixture is cooled to room temperature, and water is added to a volume of approximately 200mL. Titration is performed with ferrous ammonium sulfate standard titration solution until the solution changes from orange-yellow to yellow-green. Eight drops of N-phenyl-o-aminobenzoic acid indicator solution are added, and titration continues until the solution changes from purple-red to green, which is the endpoint. The process is complicated, time-consuming (3 hours), and requires a high level of personnel competence.

[0080] Compared with the above comparative examples 1-3, the detection method of the present invention is easy to master, fast and simple, saves more than 1 hour compared with other methods, and the process is refined, saving energy and reducing costs; it introduces high-end equipment to replace traditional processes, and has a wide measurement range (0.0007% to 50%); at the same time, it provides the industry with more detection methods and realizes the diversification of detection.

[0081] Comparative Example 4

[0082] Hydrochloric acid was used instead of phosphoric acid, and the other steps and conditions were the same as in Example 1.

[0083] The results showed that hydrochloric acid is a reducing agent and cannot play the role of phosphoric acid in decomposing the sample in this invention.

[0084] Compared with existing technologies, this invention utilizes acid dissolution instead of alkali fusion and acid extraction, and introduces high-end equipment (inductively coupled plasma atomic emission spectrometry) to replace traditional manual analysis, resulting in a wide detection range (0.0007–50%). In sulfuric acid medium, the sample is decomposed with phosphoric acid, and the analyte is oxidized to a higher oxidation state using nitric acid and perchloric acid. After dilution to a fixed volume, the sample is determined by ICP. With the addition of 5 mL of sulfuric acid, 5 mL of phosphoric acid, 2 mL of nitric acid, and 10 mL of perchloric acid, the detection limit is 0.0007%, and the repeatability is less than or equal to 0.242%. This invention overcomes the shortcomings of existing hydrometallurgical analysis techniques for laterite nickel ore and provides a diversified detection method.

[0085] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting chromium content in laterite nickel ore, characterized in that, Includes the following steps: S1. Add 0-3 mL of nitric acid, 3-7 mL of phosphoric acid, 1-10 mL of perchloric acid and 3-7 mL of sulfuric acid to the laterite nickel ore sample to be tested in sequence, and mix well to obtain mixture A. S2, Mixture A is heated to remove water and nitric acid, yielding mixture B; S3, Mixture B is heated again to remove perchloric acid, resulting in mixture C; S4, after cooling the mixture C, dilute it with water, boil it again to dissolve the salts, cool it, filter and dilute it for later use, and record it as mixture D; S5, the chromium content in laterite nickel ore was calculated by ICP determination of mixed solution D; The chromium content in the laterite nickel ore sample is denoted as M. Cr Including 0.0007%≤M Cr Samples with low chromium content <4%, 4% ≤ M Cr Samples with a chromium content of <25% and ≤25% M Cr For samples with a high chromium content of ≤50%, the amount of nitric acid added to the low chromium content samples is 0; for samples with a medium chromium content and high chromium content samples, 1-2 mL of nitric acid is added per 0.1 g of chromium content. In step S2, mixture A is heated to 200-250°C and kept at that temperature for 5-30 minutes; In step S3, the mixture B is heated to 300-350°C for 15-90 minutes until the perchloric acid fumes are completely emitted; In step S4, the ratio of water added to the laterite nickel ore sample to be tested in step S1 is (20-40) mL: 0.1 g; the boiling time is 1-2 min. In step S4, the mass concentration of mixture D is 0.0007%–50%; For every 0.1g of low chromium content sample, add 0 mL of nitric acid, 5 mL of phosphoric acid, 1–3 mL of perchloric acid, and 5 mL of sulfuric acid; For every 0.1g of chromium content sample, add 1 mL of nitric acid, 5 mL of phosphoric acid, 4–6 mL of perchloric acid, and 5 mL of sulfuric acid; For every 0.1g of high chromium content sample, add 2 mL of nitric acid, 5 mL of phosphoric acid, 8–10 mL of perchloric acid, and 5 mL of sulfuric acid.

2. The method for detecting chromium content in laterite nickel ore according to claim 1, characterized in that, The concentration of perchloric acid was 12.44 mol / L; the concentration of nitric acid was 13 mol / L; the concentration of phosphoric acid was 14.63 mol / L; and the concentration of sulfuric acid was 18 mol / L.

3. The method for detecting chromium content in laterite nickel ore according to claim 1, characterized in that, In step S5, the parameters for ICP measurement are set as follows: cooling gas flow rate 13 L / min, carrier gas flow rate 0.75 L / min, auxiliary gas flow rate 0.8 L / min, plasma power 1350~1400W, detection wavelength 267.716 nm, and pump speed 30 Rpm.

4. The method for detecting chromium content in laterite nickel ore according to claim 1, characterized in that, In step S5, a standard curve for chromium is obtained by testing the chromium standard solution using ICP; then, under the same testing conditions, the mixture D is determined by ICP, and the concentration value of the mixture D is obtained by substituting the determination result into the standard curve, and the chromium content in the laterite nickel ore is calculated.

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