Method for testing ammonia nitrogen in laterite-nickel ore hydrometallurgy wastewater

Abstract

The invention belongs to the technical field of water quality detection, and particularly relates to a method for testing ammonia nitrogen in laterite-nickel ore hydrometallurgy wastewater, which comprises the following steps: adding sodium thiosulfate and zinc sulfate into the wastewater, adjusting the pH by using a boric acid-sodium hydroxide buffer solution with the pH of 9.5, and standing; adding a proper amount of filtrate into a colorimetric tube for constant volume, adding sodium potassium tartrate tetrahydrate and a Nessler reagent, uniformly mixing, and standing; and detecting absorbance, and calculating the ammonia nitrogen concentration in the wastewater according to the absorbance. According to the method, interference of high-content sulfate radicals and metal ions in the high-sulfate industrial wastewater can be effectively eliminated, the obtained color development system is high in stability, and the method has the advantages of being easy to operate, reliable in result and the like and has important significance on detection and treatment of the laterite-nickel ore hydrometallurgy wastewater.

Description

Technical Field

[0001] The present application belongs to the technical field of water quality detection, and specifically relates to a method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater. Background Art

[0002] Ammonia nitrogen is a key indicator of water quality control. Excessive ammonia nitrogen levels can be harmful to both human health and the ecological environment, making monitoring ammonia nitrogen indicators crucial for environmental quality and pollution control. Furthermore, with the development of industrialization, the volume and type of industrial wastewater are increasing, posing additional challenges to ammonia nitrogen detection.

[0003] Nickel in laterite nickel ore accounts for approximately 70% of Earth's total land-based nickel reserves. Currently, nickel is extracted from laterite nickel ore using a hydrometallurgical process using sulfuric acid. In recent years, with the growing demand for nickel for stainless steel and new energy applications, the amount of industrial wastewater generated by the hydrometallurgical nickel extraction process has increased rapidly, and its detection and treatment have gradually attracted attention.

[0004] The industrial wastewater produced by the hydrometallurgical process of laterite nickel ore contains a large amount of sulfate ions and metal ions. Currently, the Chinese Environmental Protection Standard HJ535-2009 "Determination of Ammonia Nitrogen in Water - Nessler's Reagent Spectrophotometry" is mostly used for detection in production. The above detection method mainly includes the following steps: adding sodium thiosulfate solution to the wastewater to remove residual chlorine; then adding zinc sulfate solution and mixing, and adjusting the pH to 10.5 with sodium hydroxide solution, and allowing it to precipitate; filtering the filtrate, adding potassium sodium tartrate solution to the filtrate and mixing, and then adding Nessler's reagent and mixing, and measuring the absorbance. However, for laterite nickel ore hydrometallurgical wastewater, the inventors found in practice that pH value is a key factor affecting the ammonia nitrogen determination results, and the pH = 10.5 condition in the environmental protection standard is not applicable to high-sulfate industrial wastewater. At the same time, the use of traditional sodium hydroxide solution to adjust the pH value has problems such as slow adjustment, difficulty in detection and precise control of pH. Summary of the Invention

[0005] In view of this, the present application aims to improve the ammonia nitrogen testing method for high-sulfate industrial wastewater, and the resulting method has at least the advantages of being simple and easy to operate and having reliable results.

[0006] In order to achieve the above objectives, the technical solutions of this application are as follows: A method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater, comprising at least the following steps: S1. Sodium thiosulfate and zinc sulfate are added to the wastewater, the pH is adjusted with a boric acid-sodium hydroxide buffer solution with a pH of 9.5, and the wastewater is allowed to stand. S2. Filter, take an appropriate amount of the filtrate and dilute to volume in a colorimetric tube, add potassium sodium tartrate and Nessler's reagent, mix well, and let stand; S3. Measure the absorbance and calculate the ammonia nitrogen concentration in the wastewater based on the absorbance.

[0007] Different from the pH value (i.e., 10.5) in the environmental protection standard HJ535-2009, the inventors, through repeated comparisons and verifications, found that for high-sulfate industrial wastewater, only when the initial pH of the reaction system in step S1 is adjusted to 9.5 using a boric acid-sodium hydroxide buffer solution can the test results be consistent with the theoretical value. At the same time, after adding Nessler's reagent to the obtained filtrate, the resulting color development system is more stable and clear.

[0008] Preferably, in the above method, the boric acid-sodium hydroxide buffer solution is prepared by weighing 5 g of boric acid and dissolving it in 1000 mL of ammonia-free water, and adjusting the pH to 9.5 with saturated sodium hydroxide.

[0009] Preferably, in the above method, the volume ratio of wastewater to boric acid-sodium hydroxide buffer solution is 10:(85-90).

[0010] Preferably, step S1 is specifically as follows: taking wastewater into a volumetric flask, adding sodium thiosulfate solution and zinc sulfate solution, and then constant volume with boric acid-sodium hydroxide buffer solution with a pH of 9.5; wherein, the detection effect is better when every 100 mL of the mixed solution contains 1.5-2.5 mL of 3.5 g / L sodium thiosulfate solution and 0.8-1.5 mL of 100 g / L zinc sulfate solution.

[0011] In the present application, the method of constant volume using boric acid-sodium hydroxide buffer solution (pH=9.5) can not only effectively solve the various problems encountered during simple sodium hydroxide adjustment, making the detection method easier to operate, but also provide accurate and reliable detection results. In addition, it should be noted that in the present application method, in addition to being used to adjust and maintain the pH during flocculation in step S1, the type of buffer solution is also one of the key factors affecting the detection system obtained in step S2. The data of this application show that when the boric acid-sodium hydroxide buffer solution is replaced with other buffer solutions (such as borax-sodium hydroxide buffer solution and boric acid-potassium chloride-sodium carbonate buffer solution), the detection system may not show color and / or be unstable, making it difficult to calculate the ammonia nitrogen concentration by colorimetry.

[0012] Preferably, in the above method, step S2 is filtered using qualitative filter paper; specifically, the reaction liquid obtained in S1 is filtered into a clean container through qualitative filter paper washed with water, and part of the initial filtrate is discarded.

[0013] Preferably, in the above method, Nessler's reagent is a mercuric iodide-potassium iodide-sodium hydroxide solution; wherein each 100 mL of the solution preferably comprises 16 g of sodium hydroxide, 7 g of potassium iodide and 10.0 g of mercuric iodide.

[0014] Preferably, in the above method, the standing time in step S1 is 15-30 min.

[0015] Preferably, in the above method, the standing time in step S2 is 10-20 min.

[0016] Preferably, in the above method, the wastewater used is industrial wastewater generated in the hydrometallurgical process of laterite nickel ore.

[0017] Compared with the prior art, the beneficial effects of this application are: This application has developed a new method for determining ammonia nitrogen in high-sulfate industrial wastewater, which is more simple to operate, has more controllable operational errors, and produces more accurate and reliable test results. This method uses a boric acid-sodium hydroxide buffer solution with a specific pH to form a reaction system with the wastewater sample to be tested, sodium thiosulfate, and zinc sulfate in a constant volume manner. The resulting filtrate is then added with potassium sodium tartrate and mercuric iodide-potassium iodide-sodium hydroxide, resulting in a color-developing and stable detection system. This indicates that this method can effectively eliminate the interference of high sulfate and metal ion content in high-sulfate industrial wastewater, achieving accurate detection of ammonia nitrogen in the wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of the method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater provided in this application.

[0019] Figure 2 The following is a comparison of the color development results when different buffer solutions are used in the method of this application; A is a boric acid-sodium hydroxide buffer solution (pH=9.5), B is a boric acid-potassium chloride-sodium carbonate buffer solution (pH=9.5), and C is a borax-sodium hydroxide buffer solution (pH=10.5). DETAILED DESCRIPTION

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The term "comprise" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusions.

[0021] Based on the composition characteristics of high-sulfate industrial wastewater, this application provides a method for testing ammonia nitrogen in high-sulfate industrial wastewater, specifically Figure 1 As shown, the following steps are included: (1) Take an appropriate amount of wastewater sample in a volumetric flask, add sodium thiosulfate solution and zinc sulfate solution, dilute to volume with boric acid-sodium hydroxide buffer solution with pH = 9.5, and let it stand; (2) Filter the sample through a water-washed qualitative filter paper into a clean beaker (discard the initial filtrate), take an appropriate amount of the filtrate, dilute it to volume in a colorimetric tube with ammonia-free water, add potassium sodium tartrate solution and mercuric iodide-potassium iodide-sodium hydroxide solution, shake well, and let it stand for 10-20 minutes; (3) Measure the absorbance at a wavelength of 420 nm and calculate the ammonia nitrogen concentration using the absorbance and the following formula:

[0022] Where: ρ N is the mass concentration of ammonia nitrogen in the water sample (mg / L), A s is the absorbance of the water sample, A b is the absorbance of the blank test, a is the intercept of the calibration curve, b is the slope of the calibration curve, and V is the volume of the water sample (mL). Drawing a calibration curve using an ammonia nitrogen standard solution (prepared from ammonia nitrogen standard solution produced by Gangyan Nanke) is a prior art technique and will not be described in detail here.

[0023] The method of the present application utilizes a specific buffer solution to achieve precise control of the pH in step (1), which is not only simple and easy to operate, but also can effectively eliminate human errors; at the same time, the buffer solution helps to avoid interference of substances in the wastewater with the color development system, making the detection results accurate and reliable.

[0024] The technical solution of the present application will be described clearly and completely below in conjunction with specific embodiments. It should be understood that the embodiments described herein are only used to illustrate and explain the present application and are not intended to limit the present application.

[0025] The composition of the laterite nickel ore hydrometallurgical wastewater used in the following examples and comparative examples is shown in Table 1.

[0026] Table 1 Composition analysis of laterite nickel ore hydrometallurgical wastewater

[0027] The preparation methods of some of the reagents used in the following examples and comparative examples are as follows: ① Boric acid-sodium hydroxide buffer solution with pH = 9.5: Weigh 5 g of boric acid and dissolve it in 1000 mL of ammonia-free water, and adjust the pH to 9.5 with saturated sodium hydroxide; ②3.5 g / L sodium thiosulfate: Weigh 3.5 g of sodium thiosulfate and dissolve it in 1000 mL of ammonia-free water; ③100 g / L zinc sulfate: weigh 100 g of sodium thiosulfate and dissolve it in 1000 mL of ammonia-free water; ④500 g / L potassium sodium tartrate: Weigh 500 g of potassium sodium tartrate and dissolve it in 500 mL of water. Heat to boil to drive off ammonia. Cool thoroughly and dilute to 1000 mL. ⑤ Mercuric iodide-potassium iodide-sodium hydroxide solution: Weigh 16 g of sodium hydroxide and dissolve it in 50 mL of water, then cool to room temperature; weigh 7 g of potassium iodide and 10.0 g of mercuric iodide and dissolve them in water, then slowly pour this solution into the above 50 mL of sodium hydroxide while stirring, and dilute with water to 100 mL.

[0028] If no specific techniques or conditions are specified in the following examples, the procedures were carried out in accordance with the techniques or conditions described in the literature in the field or in accordance with the product instructions; if no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0029] Example 1 A method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater comprises the following steps: (1) Take 10 mL of wastewater sample and place it in a 100 mL volumetric flask. Add 2 mL of sodium thiosulfate solution and 1 mL of zinc sulfate solution. Make up to volume with boric acid-sodium hydroxide buffer solution with pH = 9.5 and let it stand for 25 min. (2) Filter the sample through a water-washed qualitative filter paper into a clean beaker (discard 20 mL of the initial filtrate). Take an appropriate amount of the filtrate and dilute it to a 50 mL colorimetric tube with ammonia-free water. Add 1 mL of potassium sodium tartrate solution and 1 mL of mercuric iodide-potassium iodide-sodium hydroxide solution, shake well, and let it stand for 15 minutes. (3) Measure the absorbance at a wavelength of 420 nm and calculate the ammonia nitrogen concentration using the absorbance.

[0030] The calibration curve of this method is: Abs=0.18566C-0.01128, R=0.9999.

[0031] The method in this example was combined with the spiked test to test ammonia nitrogen in water samples from different sampling points during the treatment of laterite nickel ore hydrometallurgical wastewater. The results are shown in Table 2.

[0032] Table 2 Spiked recovery under the conditions of Example 1

[0033] Note: The standard substance is ammonia nitrogen standard solution, and the spike recovery rate = (spiking result - test concentration) ÷ spike amount × 100%.

[0034] Comparative Example 1 Different from Example 1, in step (1) of this example, sodium hydroxide is used instead of the boric acid-sodium hydroxide buffer solution, which includes the following steps: (1) Take 10 mL of wastewater in a 100 mL beaker, add 2 mL of sodium thiosulfate solution and 1 mL of zinc sulfate solution, add water to 50 mL, use a pH meter, adjust the pH to 9.5 with a small amount of saturated sodium hydroxide, transfer to a 100 mL volumetric flask, wash the beaker and pH meter, transfer the washings to the volumetric flask, adjust to volume, and let it stand for 25 min; (2) Filter the sample through a water-washed qualitative filter paper into a clean beaker (discard 20 mL of the initial filtrate). Take an appropriate amount of the filtrate and dilute it to the volume in a 50 mL colorimetric tube with ammonia-free water. Add 1 mL of potassium sodium tartrate solution and 1 mL of mercuric iodide-potassium iodide-sodium hydroxide solution, shake well, and let it stand for 15 minutes. (3) Measure the absorbance at a wavelength of 420 nm and calculate the ammonia nitrogen concentration using the absorbance.

[0035] According to the methods of Example 1 and Comparative Example 1, ammonia nitrogen tests were performed on water samples at different sampling points during the treatment of laterite nickel ore hydrometallurgical wastewater. The results are shown in Tables 3-4.

[0036] Table 3 Statistics of test results of different water samples

[0037] Table 4 pH changes after static flocculation

[0038] The above results indicate that the present method has a good spike recovery rate, reliable results, and a normal pH after flocculation, demonstrating its suitability for testing high-sulfate wastewater samples. While the results of Comparative Example 1 are comparable to those of the present method, the latter suffers from issues such as excessive sodium hydroxide addition, slow adjustment, and the need to rinse the beaker and pH meter. These issues make the procedure complex, time-consuming, and prone to human error. The present method effectively addresses these issues.

[0039] Comparative Example 2 Different from Example 1, in the ammonia nitrogen testing method of this example, the boric acid-sodium hydroxide buffer solution is replaced by a boric acid-potassium chloride-sodium carbonate buffer solution (pH=9.5) and a borax-sodium hydroxide buffer solution (pH=10.5), respectively. The specific differences between the three buffer solutions are shown in Table 5.

[0040] Table 5 Preparation of different buffer solutions

[0041] For the same wastewater sample, the test results under different buffer solution conditions are as follows Figure 2As shown: When the boric acid-sodium hydroxide buffer solution is replaced with the boric acid-potassium chloride-sodium carbonate buffer solution, the solution not only does not show color after Nessler's reagent is added in step (2), but also immediately produces a white precipitate ( Figure 2 B); When the boric acid-sodium hydroxide buffer solution is replaced with a borax-sodium hydroxide buffer solution, the solution will become turbid gradually during the standing process although it will show color after adding Nessler's reagent in step (2). Figure 2 C). The above results show that boric acid-potassium chloride-sodium carbonate buffer solution and borax-sodium hydroxide buffer solution are not suitable for ammonia nitrogen detection in high-sulfate industrial wastewater.

[0042] In summary, the ammonia nitrogen testing method provided in this application can be well applied to the detection of high-sulfate industrial wastewater, especially laterite nickel ore hydrometallurgical wastewater. It is simple to operate and the results are reliable, which is of great significance for the detection and treatment of laterite nickel ore hydrometallurgical wastewater.

[0043] It should be noted that the above embodiments are only part of the embodiments of this application rather than all the embodiments, and are only used to illustrate the technical solutions of this application rather than to limit them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

Claims

1. A method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater, characterized in that: The following steps are involved: S1. Sodium thiosulfate and zinc sulfate are added to the wastewater, the pH is adjusted with a boric acid-sodium hydroxide buffer solution with a pH of 9.5, and the wastewater is allowed to stand. S2. Filter, take an appropriate amount of the filtrate and dilute to volume in a colorimetric tube, add potassium sodium tartrate and Nessler's reagent, mix well, and let stand; S3. Measure the absorbance and calculate the ammonia nitrogen concentration in the wastewater based on the absorbance.

2. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, wherein: The boric acid-sodium hydroxide buffer solution is specifically prepared by weighing 5 g of boric acid and dissolving it in 1000 mL of ammonia-free water, and adjusting the pH to 9.5 with saturated sodium hydroxide.

3. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical waste water according to claim 1, wherein the volume ratio of the waste water to the boric acid-sodium hydroxide buffer solution is 10: (85-90).

4. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, wherein step S1 is specifically: taking wastewater into a volumetric flask, adding sodium thiosulfate solution and zinc sulfate solution, and then constant to volume with the boric acid-sodium hydroxide buffer solution.

5. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 4, wherein: Each 100 mL of the mixture contains 1.5-2.5 mL of 3.5 g / L sodium thiosulfate solution and 0.8-1.5 mL of 100 g / L zinc sulfate solution.

6. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, characterized in that: Step S2 is filtering with qualitative filter paper.

7. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, characterized in that: The Nessler's reagent is a mercuric iodide-potassium iodide-sodium hydroxide solution.

8. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, wherein: The standing time in step S1 is 15-30 min.

9. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, wherein: The standing time in step S2 is 10-20 min.

10. The method for testing ammonia nitrogen in laterite nickel ore hydrometallurgical wastewater according to claim 1, characterized in that: The wastewater is laterite nickel ore hydrometallurgical wastewater.

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