A method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore
A pH-adjusted boric acid-sodium hydroxide buffer solution method addresses pH instability and interference in high-sulfate wastewater, achieving accurate ammonia nitrogen detection in laterite nickel ore hydrometallurgical processes.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- PT ESG NEW ENERGY MATERIAL
- Filing Date
- 2024-10-23
- Publication Date
- 2026-04-23
AI Technical Summary
The existing methods for testing ammonia nitrogen in high-sulfate industrial wastewater from the hydrometallurgical process of laterite nickel ores are inefficient due to pH instability and interference from sulfate ions, leading to inaccurate and complex measurements.
A method using a boric acid-sodium hydroxide buffer solution at pH 9.5 to adjust and maintain pH, combined with sodium thiosulfate and zinc sulfate, followed by filtration and addition of potassium sodium tartrate and a mercuric iodide-potassium iodide-sodium hydroxide solution for stable color development, enabling accurate ammonia nitrogen detection.
The method provides simple, reliable, and accurate ammonia nitrogen testing by controlling pH and minimizing interference, ensuring precise results in high-sulfate wastewater.
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Figure ID2024000040_23042026_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] A METHOD FOR TESTING AMMONIA NITROGEN IN WASTEWATER FROM THE HYDROMETALLURGICAL PROCESS OF LATERITE NICKEL ORE
[0003] FILED OF DISCLOSURE
[0004] This application belongs to the field of water quality testing technology, speci fically involving a method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore .
[0005] BACKGROUND
[0006] The ammonia nitrogen index i s one of the important parameters for water quality control . High levels of ammonia nitrogen can pose risks to human health and the ecological environment , making the monitoring of ammonia nitrogen crucial in environmental quality and pollution control . Moreover, with the development of industriali zation, the volume of industrial wastewater discharge is increasing, and the types of industrial wastewater are becoming more diversi fied, which presents additional challenges for ammonia nitrogen testing .
[0007] Nickel in laterite nickel ores accounts for about 70% of the total terrestrial nickel reserves , and currently, laterite nickel ores are primarily processed to extract nickel using sul furic acid through hydrometallurgical processes . In recent years , with the growing demand for nickel in stainless steel and new energy sectors , the volume of industrial wastewater generated by these hydrometallurgical nickel extraction processes has rapidly increased, bringing its detection and treatment into greater focus .
[0008] The industrial wastewater generated from the hydrometallurgical process of laterite nickel ores contains a high concentration of sul fate ions and metal ions . Currently, in production, the Chinese environmental protection standard HJ535-2009 "Water Quality - Determination of Ammonia Nitrogen by Nessler ' s Reagent Spectrophotometry" is commonly used for testing . The method involves the following steps : adding sodium thiosul fate solution to the wastewater to remove residual chlorine; then adding zinc sulfate solution and mixing, adjusting the pH to 10.5 with a sodium hydroxide solution, and allowing it to settle; filtering to obtain the filtrate, adding potassium sodium tartrate solution to the filtrate, mixing, then adding Nessler's reagent, and measuring the absorbance. However, the inventor has discovered in practice that pH is a critical factor affecting the measurement of ammonia nitrogen in the wastewater from the hydrometallurgical process of laterite nickel ores. Furthermore, the pH condition of 10.5 specified in the environmental standards is not suitable for high- sulfate industrial wastewater. Also, using traditional sodium hydroxide solutions to adjust pH can be slow, challenging to monitor, and difficult to control precisely.
[0009] SUMMARY
[0010] To overcome this disadvantages, this application aims to improve the ammonia nitrogen testing method for high-sulfate industrial wastewater, and the resulting method has the advantages of being simple to operate and providing reliable results.
[0011] To achieve the above objectives, the technical solution of this application is specifically as follows:
[0012] A method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore, which includes at least the following steps:
[0013] 51. Add sodium thiosulfate and zinc sulfate to the wastewater, adjust the pH to 9.5 using a boric acid-sodium hydroxide buffer solution, and allow the mixture to stand.
[0014] 52 . Filter the solution, take an appropriate amount of the filtrate and adjust to a set volume in a colorimetric tube, add potassium sodium tartrate and Nessler's reagent, mix well, and allow to stand.
[0015] 53. Measure the absorbance, and calculate the ammonia nitrogen concentration in the wastewater based on the absorbance.
[0016] Unlike the pH value of 10.5 specified in the environmental protection standard HJ535-2009, the inventor, through repeated comparative verification, found that for high-sulfate industrial wastewater, adjusting the initial pH of the reaction system in step SI to 9.5 using a boric acid-sodium hydroxide buffer solution results in detection outcomes that are consistent with theoretical values. Additionally, the color system obtained by adding Nessler's reagent to the filtered solution from this process is more stable and clear.
[0017] Preferably, in the above method, the boric acid-sodium hydroxide buffer solution is prepared as follows: weigh 5 g of boric acid and dissolve it in 1000 mL of ammonia-free water, then adjust the pH to 9.5 using saturated sodium hydroxide.
[0018] Preferably, in the above method, the volume ratio of the wastewater to the boric acid-sodium hydroxide buffer solution is 10 : (85-90) .
[0019] Preferably, in step SI, the specific procedure is as follows: take the wastewater in a volumetric flask, add sodium thiosulfate solution and zinc sulfate solution, then bring to volume with the boric acid-sodium hydroxide buffer solution at pH 9.5. For the best detection results, in every 100 mL of the mixture, it should contain 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.
[0020] In this application scheme, by using the boric acid-sodium hydroxide buffer solution (pH=9.5) for dilution, not only can the various issues associated with solely using sodium hydroxide for pH adjustment be effectively resolved, making the testing method easier to operate, but the results are also accurate and reliable. Additionally, it is important to note that in this method, the buffer solution is used not only to adjust and maintain the pH during the flocculation in step SI, but its type is also one of the key factors affecting the detection system obtained in step S2. The data from 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 develop color and / or be unstable, making it difficult to calculate the ammonia nitrogen concentration by colorimetry.
[0021] Preferably, in the aforementioned method, step S2 involves filtering using qualitative filter paper; specifically, the reaction liquid obtained from SI is filtered into a clean container using water-rinsed qualitative filter paper, and part of the initial filtrate is discarded.
[0022] Preferably, in the aforementioned method, the Nessler's reagent used is a solution of mercuric iodide, potassium iodide, and sodium hydroxide; specifically, for every 100 mL of solution, the optimal composition includes 16 g of sodium hydroxide, 7 g of potassium iodide, and 10.0 g of mercuric iodide.
[0023] Preferably, in the aforementioned method, the standing time for step SI is 15-30 minutes.
[0024] Preferably, in the aforementioned method, the standing time for step S2 is 10-20 minutes.
[0025] Preferably, in the aforementioned method, the wastewater used is industrial wastewater generated from the hydrometallurgical process of laterite nickel ore.
[0026] Compared to the prior art, the beneficial effects of this application are:
[0027] This application, targeting high-sulfate industrial wastewater, develops a new method for measuring ammonia nitrogen that is simpler to operate, with more controllable operational errors and more accurate and reliable results. The method involves using a boric acid-sodium hydroxide buffer solution with a specific pH to directly form a reaction system with the wastewater sample, sodium thiosulfate, and zinc sulfate by adjusting the volume. The resulting filtrate, when combined with potassium sodium tartrate and a mercuric iodide-potassium iodide-sodium hydroxide solution, forms a stable and color-developing detection system. It is evident that this method can effectively eliminate interference from high concentrations of sulfate ions and metal ions in high-sulfate industrial wastewater, allowing for the accurate detection of ammonia nitrogen in the wastewater.
[0028] BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a flowchart of the method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore provided by this application.
[0030] FIG. 2 shows a comparison of color development results when using different buffer solutions in the method of this application; where A is the boric acid-sodium hydroxide buffer solution (pH=9.5) , B is the boric acid-potassium chloride-sodium carbonate buffer solution (pH=9.5) , and C is the borax-sodium hydroxide buffer solution (pH=10.5) .
[0031] DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0032] 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 terms "comprise" and any variations thereof in the description and claims of this application are intended to cover non-exclusive inclusion.
[0033] Based on the compositional characteristics of high-sulfate industrial wastewater, this application provides a method for testing ammonia nitrogen suitable for high-sulfate industrial wastewater. Specifically, as shown in FIG. 1, it includes the following steps:
[0034] (1) Take an appropriate amount of the wastewater sample into a volumetric flask, add sodium thiosulfate solution and zinc sulfate solution, and bring to volume with a boric acid-sodium hydroxide buffer solution at pH 9.5. Allow the mixture to stand.
[0035] (2) Filter the mixture into a clean beaker using water-rinsed qualitative filter paper (discard the initial filtrate) . Take an appropriate amount of the filtrate, bring to volume in a colorimetric tube with ammonia-free water, add potassium sodium tartrate solution and a mercuric iodide-potassium iodide-sodium hydroxide solution, shake well, and allow it to stand for 10-20 minutes .
[0036] (3) Measure the absorbance at a wavelength of 420 nm, and calculate the ammonia nitrogen concentration using the absorbance and the following formula:
[0037] In the formula: p« is the mass concentration of ammonia nitrogen in the water sample (mg / L) , Asis the absorbance of the water sample, Ab 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) . The calibration curve is drawn using standard ammonia nitrogen solutions (prepared from standard ammonia nitrogen solutions produced by National Center for Quality Supervision and Inspection) , which is a conventional technique and will not be further elaborated here .
[0038] The method of this application utili zes a speci fic buf fer solution to achieve precise pH control in step ( 1 ) , making it not only simple and easy to operate but also ef fectively eliminating human error . Additionally, this buf fer solution helps to avoid interference from substances in the wastewater with the colorimetric system, ensuring accurate and reliable test results .
[0039] The following provides a clear and complete description of the technical solution of this application in conj unction with speci fic embodiments . It should be understood that the embodiments described herein are only for illustration and explanation of this application and are not intended to limit the scope of the application .
[0040] The composition of the hydrometallurgical wastewater from laterite nickel ore used in the following examples and comparative examples is shown in Table 1 .
[0041] Table 1 : Component Analysis of Hydrometallurgical Wastewater from
[0042] Laterite Nickel Ore
[0043] The preparation methods for some of the reagents used in the following examples and comparative examples are as follows :
[0044] (T) Boric acid-sodium hydroxide buf fer solution at pH=9 . 5 : Dissolve 5 g of boric acid in 1000 mL of ammonia- free water, and adj ust the pH to 9 . 5 with saturated sodium hydroxide . @ 3.5 g / L sodium thiosulfate: Dissolve 3.5 g of sodium thiosulfate in 1000 mL of ammonia-free water.
[0045] @ 100 g / L zinc sulfate: Dissolve 100 g of zinc sulfate in 1000 mL of ammonia-free water.
[0046] (?) 500 g / L potassium sodium tartrate: Dissolve 500 g of potassium sodium tartrate in 500 mL of water, heat to boiling to remove ammonia, then cool thoroughly and dilute to 1000 mL .
[0047] @ Mercuric iodide-potassium iodide-sodium hydroxide solution: Dissolve 16 g of sodium hydroxide in 50 mL of water and cool to room temperature. Dissolve 7 g of potassium iodide and 10.0 g of mercuric iodide in water, then slowly pour this solution into the 50 mL sodium hydroxide solution with stirring. Dilute the mixture to 100 mL with water.
[0048] In the following examples, unless specific techniques or conditions are mentioned, the procedures are carried out according to the techniques or conditions described in the literature within this field or in accordance with product manuals. Any reagents or instruments not specified by manufacturer are standard products available for purchase on the market.
[0049] Example 1
[0050] A method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore, comprising the following steps:
[0051] (1) Take 10 mL of wastewater sample in a 100 mL volumetric flask, add 2 mL of sodium thiosulfate solution and 1 mL of zinc sulfate solution, bring to volume with boric acid-sodium hydroxide buffer solution at pH 9.5, and let it stand for 25 minutes.
[0052] (2) Filter the mixture into a clean beaker using water-rinsed qualitative filter paper (discard the initial 20 mL of filtrate) . Take an appropriate amount of the filtrate, bring it to volume in a 50 mL colorimetric tube with ammonia-free water, add 1 mL of potassium sodium tartrate solution and 1 mL of mercuric iodidepotassium iodide-sodium hydroxide solution, shake well, and let it stand for 15 minutes.
[0053] (3) Measure the absorbance at a wavelength of 420 nm, and calculate the ammonia nitrogen concentration based on the absorbance .
[0054] The calibration curve for the method in this example is: Abs = 0.18566C - 0.01128, R = 0.9999,
[0055] Using the method described in this example combined with a spiking test, ammonia nitrogen testing was conducted on water samples from different sampling points during the treatment process of wastewater from the hydrometallurgical process of laterite nickel ore. The results are shown in Table 2.
[0056] Table 2: Spike Recovery Rates Under the Conditions of Example 1
[0057] Note: The standard substance is an ammonia nitrogen standard solution. The spiked recovery rate is calculated as = (Spiked Result-Test Concentration) / Spiked Amountxl00%.
[0058] Comparative Example 1
[0059] In contrast to Example 1, this example replaces the boric acid- sodium hydroxide buffer solution with sodium hydroxide in step (1) , which includes the following steps:
[0060] (1) Take 10 mL of wastewater into a 100 mL beaker, add 2 mL of sodium thiosulfate solution and 1 mL of zinc sulfate solution, then add water to 50 mL . Use a pH meter and adjust the pH to 9.5 with a small amount of saturated sodium hydroxide. Transfer the solution to a 100 mL volumetric flask, rinse the beaker and pH meter, and transfer the rinsing solution to the volumetric flask. Make up to the mark and let it stand for 25 minutes.
[0061] (2) Filter through water-washed qualitative filter paper into a clean beaker (discard the initial 20 mL of filtrate) . Take an appropriate amount of the filtrate, dilute it to 50 mL in a 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, mix well, and let it stand for 15 minutes .
[0062] ( 3 ) Measure the absorbance at a wavelength of 420 nm and calculate the ammonia nitrogen concentration using the absorbance .
[0063] The ammonia nitrogen tests were performed on water samples from di f ferent sampling points during the processing of lateritic nickel ore wet metallurgy wastewater using the methods of Example 1 and Comparative Example 1 . The results are shown in Tables 3 and 4 , respectively .
[0064] Table 3 Statistical Results of Testing Di f ferent Water Samples
[0065] Table 4 pH Changes After Sedimentation Flocculation
[0066] From the results above , it can be seen that the method provided in this application has a good spiking recovery rate , reliable results , and normal pH after flocculation, indicating that the method is suitable for testing high-sul fate wastewater samples . Although the detection results of Comparative Example 1 are similar to those of the method provided in this application, the method has issues such as the risk of over-adding sodium hydroxide, slow adjustment, and the need to rinse the beaker and pH meter. These problems lead to a complex operation, longer time, and potential for human error. The method in this application effectively addresses these issues.
[0067] Comparative Example 2
[0068] Unlike Example 1, in the ammonia nitrogen testing method of this example, boric acid-potassium chloride-sodium carbonate buffer solution (pH=9.5) and borax-sodium hydroxide buffer solution (pH=10.5) are used to replace the boric acid-sodium hydroxide buffer solution. The specific differences between the three buffer solutions are shown in Table 5.
[0069] Table 5 Preparation of Different Buffer Solutions
[0070] For the same wastewater sample, the test results under different buffer solution conditions are shown in FIG. 2. When the boric acid-sodium hydroxide buffer solution was replaced with a boric acid-potassium chloride-sodium carbonate buffer solution, the solution not only failed to exhibit color after adding Nessler's reagent in step (2) , but also immediately formed a white precipitate ( FIG . 2B ) . On the other hand, when the boric acid- sodium hydroxide buf fer solution was replaced with a borax-sodium hydroxide buf fer solution, the solution did exhibit color after adding Nessler ' s reagent , but it gradually became turbid during standing ( FIG . 2C ) . These results indicate that both the boric acid-potassium chloride-sodium carbonate buf fer solution and the borax-sodium hydroxide buf fer solution are unsuitable for ammonia nitrogen detection in high sul fate industrial wastewater .
[0071] In summary, the ammonia nitrogen testing method provided in this application is highly suitable for high sul fate industrial wastewater, particularly for the detection of nickel laterite metallurgy wastewater . The method is simple to operate and yields reliable results , making it of signi ficant importance for the detection and treatment of nickel laterite ore metallurgy wastewater .
[0072] It should be noted that the above examples are only a portion of the embodiments of this application and are not all-encompassing; they are intended to illustrate the technical solutions of this application rather than to limit them . All other embodiments derived by those skilled in the art based on the examples in this application, without any inventive ef fort , fall within the scope of protection of this application .
Claims
WHAT IS CLAIMED IS1. A method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore, characterized by comprising the following steps:
51. Adding sodium thiosulfate and zinc sulfate to the wastewater, adjusting the pH with a boric acid-sodium hydroxide buffer solution to pH 9.5, and allowing the solution to stand.52 . Filter the solution, take an appropriate amount of the filtrate, bring it to a constant volume in a colorimetric tube, add potassium sodium tartrate and Nessler's reagent, mix well, and allow it to stand.
53. Measure the absorbance, and calculate the ammonia nitrogen concentration in the wastewater based on the absorbance.
2. The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1, characterized in that the boric acid-sodium hydroxide buffer solution is specifically prepared by dissolving 5 g of boric acid 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 wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1, wherein the volume ratio of wastewater to boric acid- sodium hydroxide buffer solution is 10: (85-90) .
4. The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1, wherein step SI specifically comprises: taking the wastewater into a volumetric flask, adding a sodium thiosulfate solution and a zinc sulfate solution, and then bringing the volume to a constant with the boric acid-sodium hydroxide buffer solution.
5. The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 4, characterized in that for every 100 mL of the mixed solution, it 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 wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1 , characteri zed in that step S2 involves filtering using qualitative filter paper .7 . The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1 , characteri zed in that the Nessler ' s reagent used is a solution of mercuric iodide , potassium iodide , and sodium hydroxide .8 . The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1 , characteri zed in that the standing time speci fied in step51 is 15-30 minutes .9 . The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1 , characteri zed in that the standing time speci fied in step52 is 10-20 minutes .10 . The method for testing ammonia nitrogen in wastewater from the hydrometallurgical process of laterite nickel ore according to claim 1 , characteri zed in that the wastewater mentioned is speci fically from the hydrometallurgical process of laterite nickel ore .