A sample preparation method and detection method for ammonia nitrogen in high-sulfate wastewater

Abstract

The application relates to the technical field of water quality detection, and particularly provides a sample preparation method and a detection method for ammonia nitrogen detection in high-sulfate wastewater, the sample preparation method comprises the following steps: S1, first mixing sodium thiothiosulfate, zinc sulfate, to-be-detected wastewater and a boric acid-sodium hydroxide buffer solution, and carrying out first standing to obtain a first mixture; S2, carrying out solid-liquid separation on the first mixture in step S1, carrying out constant volume on the obtained liquid phase after separation to obtain a second solution; second mixing potassium sodium tartrate, Nash reagent and the second solution, and carrying out second standing to obtain a to-be-detected sample. The method can effectively eliminate the interference of high-content sulfate radicals and metal ions in high-sulfate industrial wastewater, the obtained color developing system has high stability, and has the advantages of simple operation, reliable results and the like, and has important significance for detection and treatment of laterite nickel ore hydrometallurgy wastewater.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water quality detection, and particularly relates to a sample preparation method and a detection method for ammonia nitrogen detection in high sulfate wastewater. BACKGROUND

[0002] The ammonia nitrogen index is one of important items for water quality control, and high ammonia nitrogen content can cause harm to human health and the ecological environment, so the monitoring of the ammonia nitrogen index is very important in environmental quality and pollution control. Moreover, with the development of industrialization, the amount of industrial wastewater is increasing, and the types of industrial wastewater are also becoming more and more diversified, which brings more challenges to ammonia nitrogen detection.

[0003] Nickel in laterite nickel ore accounts for about 70% of the total land-based nickel reserves on earth, and at present, the laterite nickel ore is mostly extracted by a wet metallurgical process using sulfuric acid. In recent years, with the increasing demand for nickel for stainless steel and new energy, the amount of industrial wastewater generated by the wet nickel extraction process has rapidly increased, and its detection and treatment have gradually attracted attention.

[0004] The industrial wastewater generated by the laterite nickel ore wet metallurgical process contains a large amount of sulfate ions and metal ions, and it is difficult to test by using the traditional absorbance detection method, and there are problems such as inaccurate detection data and long detection time.

[0005] Therefore, for the laterite nickel ore wet metallurgical wastewater, a new detection method for the ammonia nitrogen content in wastewater needs to be developed. SUMMARY

[0006] In view of the deficiencies in the prior art, the purpose of the present application is to provide a sample preparation method and a detection method for ammonia nitrogen detection in high sulfate wastewater, which has the advantages of being simple and easy to operate, and the results are reliable.

[0007] To achieve this purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a sample preparation method for ammonia nitrogen detection in high sulfate wastewater, which comprises the following steps:

[0009] S1, first mix sodium thiosulfate, zinc sulfate, wastewater to be tested, and boric acid-sodium hydroxide buffer solution, and then stand for a first time to obtain a first mixture;

[0010] S2, the first mixture obtained in step S1 is subjected to solid-liquid separation, and the liquid phase after separation is subjected to constant volume to obtain a second solution; second mix potassium sodium tartrate, Nessler's reagent and the second solution, and then stand for a second time to obtain a sample to be tested.

[0011] The sample preparation method for ammonia nitrogen detection in high sulfate wastewater provided by the application removes residual chlorine by using sodium thiosulfate solution; then zinc sulfate solution is added and mixed uniformly, so as to carry out subsequent flocculation and precipitation; the boracic acid-sodium hydroxide buffer solution is the key of the application, the pH in the system is adjusted by the boracic acid-sodium hydroxide buffer solution, the interference of sulfate and metal ions in the wastewater to be detected can be avoided, the detection result is accurate, and after subsequent separation, the color system obtained after adding Nash reagent to the liquid phase is more stable and clear, the detection speed is faster, and the application prospect is wide.

[0012] It needs to be further explained that the boracic acid-sodium hydroxide buffer solution added in the system is matched with the zinc sulfate solution and the subsequent potassium sodium tartrate and Nash reagent, when these reagents are replaced by other reagents, the stable and efficient flocculation effect of the boracic acid-sodium hydroxide buffer solution cannot be achieved, and the detection result is also greatly affected.

[0013] Preferably, the wastewater to be detected in step S1 is high sulfate wastewater, preferably red soil nickel ore hydrometallurgy wastewater.

[0014] It is worth noting that the red soil nickel ore hydrometallurgy wastewater is different from the conventional wastewater in that it contains a large amount of sulfate and metal ions, and the sulfate is easy to change the color intensity in the process of ammonia nitrogen detection, thereby causing the inaccuracy of absorbance detection data and the difficulty of detection.

[0015] Preferably, the content of sulfate in the wastewater to be detected is 20-40 g / L, for example, it can be 20 g / L, 23 g / L, 25 g / L, 27 g / L, 29 g / L, 32 g / L, 34 g / L, 36 g / L, 38 g / L or 40 g / L, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0016] Preferably, the content of magnesium element in the wastewater to be detected is 6-8 g / L, for example, it can be 6 g / L, 6.3 g / L, 6.5 g / L, 6.7 g / L, 6.9 g / L, 7.2 g / L, 7.4 g / L, 7.6 g / L, 7.8 g / L or 8 g / L, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0017] Preferably, the content of sodium element in the wastewater to be detected is 2-4 g / L, for example, it can be 2 g / L, 2.3 g / L, 2.5 g / L, 2.7 g / L, 2.9 g / L, 3.2 g / L, 3.4 g / L, 3.6 g / L, 3.8 g / L or 4 g / L, but is not limited to the listed values, and other values not listed in the range are also applicable.

[0018] Preferably, the manganese content in the wastewater to be tested is 2-50 mg / L, for example, it can be 2 mg / L, 3 mg / L, 5 mg / L, 10 mg / L, 12 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 28 mg / L, 30 mg / L, 32 mg / L, 35 mg / L, 40 mg / L, 45 mg / L or 50 mg / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0019] Preferably, the pH of the sodium borate-sodium hydroxide buffer solution is 9.4-9.6, for example, it can be 9.4, 9.5 or 9.6, etc.

[0020] The pH of the sodium borate-sodium hydroxide buffer solution in the present application is very critical. According to the research, when the pH of the sodium borate-sodium hydroxide buffer solution is not within the above range, it is difficult to obtain accurate detection results.

[0021] Preferably, the preparation of the sodium borate-sodium hydroxide buffer solution comprises: dissolving boric acid in water to obtain a boric acid solution, adjusting the pH of the boric acid solution to the target pH with a saturated sodium hydroxide solution to obtain the sodium borate-sodium hydroxide buffer solution.

[0022] It is further pointed out that in the present application, by means of the sodium borate-sodium hydroxide buffer solution (pH = 9.4-9.6) for constant volume, not only can the various problems in the simple sodium hydroxide adjustment be effectively solved, but also the detection method is easier to operate, and the detection result is accurate and reliable. In addition, it should be noted that in the present application, in addition to being used for adjusting and maintaining the pH during flocculation in step S1, the type of the buffer solution is also one of the key factors affecting the sample to be tested obtained in step S2. The data of the present application show that when the sodium borate-sodium hydroxide buffer solution is replaced by other buffer solutions (such as borax-sodium hydroxide buffer solution and boric acid-potassium chloride-sodium carbonate buffer solution), the detection system may not be colored and / or unstable, resulting in difficulty in calculating the ammonia nitrogen concentration by colorimetry.

[0023] Preferably, the sodium thiosulfate is added in the form of a sodium thiosulfate solution.

[0024] Preferably, the zinc sulfate is added in the form of a zinc sulfate solution.

[0025] Preferably, the mass concentration of the sodium thiosulfate solution is 3.0-4.0 g / L, for example, it can be 3.0 g / L, 3.2 g / L, 3.3 g / L, 3.4 g / L, 3.5 g / L, 3.6 g / L, 3.7 g / L, 3.8 g / L, 3.9 g / L or 4.0 g / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0026] Preferably, the mass concentration of the zinc sulfate solution is 80–120 g / L, for example, it can be 80 g / L, 85 g / L, 89 g / L, 94 g / L, 98 g / L, 103 g / L, 107 g / L, 112 g / L, 116 g / L or 120 g / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0027] Preferably, the volume ratio of the sodium thiosulfate solution to the zinc sulfate solution is (1.5–2.5):(0.8–1.5), wherein the number of parts of sodium thiosulfate solution can be, for example, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5, etc. The number of parts of zinc sulfate solution can be, for example, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, or 1.5, etc.

[0028] Preferably, the volume ratio of the sodium thiosulfate solution to the wastewater to be tested is (1.5 to 2.5):10, for example, it can be 1.5:10, 1.7:10, 1.8:10, 1.9:10, 2:10, 2.1:10, 2.2:10, 2.3:10, 2.4:10 or 2.5:10, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] Preferably, the volume ratio of the boric acid-sodium hydroxide buffer solution to the wastewater to be tested is (86-87.7):1, for example, it can be 86:1, 86.2:1, 86.4:1, 86.6:1, 86.8:1, 87:1, 87.2:1, 87.4:1, 87.6:1 or 87.7:1, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0030] Unlike existing detection methods, this invention does not add a trace amount of boric acid-sodium hydroxide buffer solution before adding water to make up the volume. Instead, it directly uses boric acid-sodium hydroxide buffer solution to make up the volume. This can greatly improve the stability of the analyte in the entire system and avoid interference from sulfate and metal ions in the detection.

[0031] Preferably, the first mixing includes: placing the wastewater to be tested in a volumetric flask, adding sodium thiosulfate solution and zinc sulfate solution, and then making up to volume using boric acid-sodium hydroxide buffer solution.

[0032] Preferably, the first settling time in step S1 is 15 to 30 minutes, for example, it can be 15 minutes, 17 minutes, 19 minutes, 20 minutes, 22 minutes, 24 minutes, 25 minutes, 27 minutes, 29 minutes or 30 minutes, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] Preferably, the solid-liquid separation in step S2 comprises filtration, preferably using qualitative filter paper.

[0034] Preferably, the Nessler's reagent is a mercury iodide-potassium iodide-sodium hydroxide solution.

[0035] Preferably, the concentration of mercury iodide in the Nessler's reagent is 9.5-10.5 g / L, for example, it can be 9.5 g / L, 9.7 g / L, 9.8 g / L, 9.9 g / L, 10 g / L, 10.1 g / L, 10.2 g / L, 10.3 g / L, 10.4 g / L or 10.5 g / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0036] Preferably, the concentration of potassium iodide in the Nessler's reagent is 5-10 g / L, for example, it can be 5 g / L, 5.6 g / L, 6.2 g / L, 6.7 g / L, 7.3 g / L, 7.8 g / L, 8.4 g / L, 8.9 g / L, 9.5 g / L or 10 g / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0037] Preferably, the concentration of sodium hydroxide in the Nessler's reagent is 12-20 g / L, for example, it can be 12 g / L, 12.9 g / L, 13.8 g / L, 14.7 g / L, 15.6 g / L, 16.5 g / L, 17.4 g / L, 18.3 g / L, 19.2 g / L or 20 g / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0038] Preferably, the potassium sodium tartrate is added in the form of a potassium sodium tartrate solution.

[0039] Preferably, the concentration of the potassium sodium tartrate solution is 450-500 g / L, for example, it can be 450 g / L, 456 g / L, 462 g / L, 467 g / L, 473 g / L, 478 g / L, 484 g / L, 489 g / L, 495 g / L or 500 g / L, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0040] Preferably, the volume ratio of the potassium sodium tartrate solution to the Nessler's reagent is (0.8-1.2):1, for example, it can be 0.8:1, 0.85:1, 0.89:1, 0.94:1, 0.98:1, 1.03:1, 1.07:1, 1.12:1, 1.16:1 or 1.2:1, etc., but not limited to the listed values, other values not listed in this range are also applicable.

[0041] Preferably, the volume ratio of the sodium potassium tartrate solution to the separated liquid phase is (0.8-1.2):20, for example, it can be 0.8:20, 0.85:20, 0.89:20, 0.94:20, 0.98:20, 1.03:20, 1.07:20, 1.12:20, 1.16:20 or 1.2:20, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0042] Preferably, the second mixing comprises: taking the separated liquid phase into a colorimetric tube and adding a sodium potassium tartrate solution and a Nessler's reagent.

[0043] Preferably, the second standing time is 10-20 min, for example, it can be 10 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min or 20 min, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0044] In a second aspect, the present application provides a method for detecting ammonia nitrogen in laterite nickel ore hydrometallurgy wastewater, which uses the sample obtained by the sample preparation method for detecting ammonia nitrogen in high sulfate wastewater in the first aspect.

[0045] The method for detecting ammonia nitrogen in laterite nickel ore hydrometallurgy wastewater provided in the second aspect of the present application can realize rapid, efficient and accurate detection of ammonia nitrogen content, and has a wide application prospect.

[0046] Preferably, the detection method uses absorbance.

[0047] Preferably, the wavelength detected in the detection method is 400-450 nm, for example, it can be 400 nm, 406 nm, 412 nm, 417 nm, 423 nm, 428 nm, 434 nm, 439 nm, 445 nm or 450 nm, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0048] Compared with the prior art, the present application has at least the following beneficial effects:

[0049] The application provides a sample preparation method for ammonia nitrogen detection in high-sulfate wastewater, which is suitable for laterite nickel ore hydrometallurgy wastewater containing a large amount of sulfate, and a new ammonia nitrogen determination method is developed, which is simple in operation, does not need a distillation process, and is more controllable in operation error and more accurate and reliable in detection result. Specifically, a specific pH borate-sodium hydroxide buffer solution is used to directly form a reaction system with the to-be-detected wastewater, sodium thiosulfate and zinc sulfate in a constant volume manner, and the liquid phase obtained after solid-liquid separation is added with potassium sodium tartrate and Nash reagent to form a detection system which can develop color and is stable. It can be seen that the method provided by the application can effectively eliminate the interference of high content of sulfate and metal ions in high-sulfate industrial wastewater, realize accurate detection of ammonia nitrogen in the wastewater, and the standard addition recovery rate of ammonia nitrogen detection is 97.2-101.1% under the preferred conditions, and the detection error of the standard solution is less than 0.013 mg / L. BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 A detection method flow chart for ammonia nitrogen detection in high-sulfate wastewater provided by the application.

[0051] Figure 2 A color development chart for adding mercury iodide-potassium iodide-sodium hydroxide solution in step S2 in Example 1 of the application and after the second standing.

[0052] Figure 3 A color development chart for adding mercury iodide-potassium iodide-sodium hydroxide solution in step S2 in Comparative Example 2 of the application and after standing.

[0053] Figure 4 A color development chart for adding mercury iodide-potassium iodide-sodium hydroxide solution in step S2 in Comparative Example 3 of the application and after standing. DETAILED DESCRIPTION

[0054] In order to facilitate the understanding of the present application, the present application lists the following examples. Those skilled in the art should understand that the examples are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0055] It should be understood that the terms "first", "second" and the like are used only for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0056] As a specific embodiment of the present application, a detection method for ammonia nitrogen detection in high-sulfate wastewater is provided, referring to Figure 1 , the detection method comprises the following steps:

[0057] S1, first mixed sodium thiosulfate, zinc sulfate, wastewater to be measured and boric acid-sodium hydroxide buffer solution, and after first standing, a first mixture is obtained.

[0058] S2, the first mixture in step S1 is subjected to solid-liquid separation, and the obtained liquid phase after separation is subjected to constant volume to obtain a second solution; second mixed sodium potassium tartrate, Nash reagent and the second solution are mixed, and after second standing, a sample to be measured is obtained.

[0059] S3, the absorbance of the sample to be measured in step S2 is measured, and the ammonia nitrogen concentration is calculated by using the absorbance and formula (1).

[0060]

[0061] In the formula: 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). The calibration curve is drawn by using an ammonia nitrogen standard solution (prepared by Jiangyan Nake) and the drawing of the calibration curve is prior art, which will not be described here.

[0062] The present application uses a specific buffer solution to realize the accurate control of pH in step (1), which is not only simple and easy to operate, but also can effectively eliminate human error; at the same time, the buffer solution is beneficial to avoid the interference of substances in the wastewater to the color developing system, so that the detection result is accurate and reliable.

[0063] The technical solutions of the present application will be described clearly and completely in combination 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 used to limit the present application.

[0064] The composition of the laterite nickel ore hydrometallurgical wastewater used in the following examples and comparative examples is shown in Table 1. Since the wastewater is extracted at different equipment and different running time during the process of laterite nickel ore hydrometallurgy, the indicators will fluctuate within the range of Table 1.

[0065] Table 1

[0066] Item Range pH 7-8 Mn (mg / L) 2～50 Mg (g / L) 6.2-8.3 Na (g / L) 2-3.8 TSS (total suspended solids, mg / L) ＜20 [NH3-N (mg / L)] ＜10 Cl - (mg / L) 25-50 COD (chemical oxygen demand, mg / L) 20-45 SO4 2- (g / L) 20-40 TDS (total dissolved solids, g / L) 23-60

[0067] In the present application, if not otherwise specified, in order to ensure the accuracy of the ammonia nitrogen content detection, the water used is ammonia-free water.

[0068] The preparation methods of some reagents used in the following examples and comparative examples are as follows:

[0069] ① pH = 9.4 ~ 9.6 borate-sodium hydroxide buffer solution: 5 g of boric acid was dissolved in 1000 mL of ammonia-free water, and the pH was adjusted to 9.4 ~ 9.6 with saturated sodium hydroxide;

[0070] ② 3.0 ~ 4.0 g / L sodium thiosulfate: 3.0 ~ 4.0 g of sodium thiosulfate was dissolved in 1000 mL of ammonia-free water;

[0071] ③ 80 ~ 120 g / L zinc sulfate: 80 ~ 120 g of sodium thiosulfate was dissolved in 1000 mL of ammonia-free water;

[0072] ④ 450 ~ 500 g / L potassium sodium tartrate: 450 ~ 500 g of potassium sodium tartrate was dissolved in 500 mL of water, heated and boiled to remove ammonia, and diluted to 1000 mL after cooling;

[0073] ⑤ Mercuric iodide-potassium iodide-sodium hydroxide solution: 12 ~ 20 g of sodium hydroxide was dissolved in 50 mL of water, cooled to room temperature; 5 ~ 10 g of potassium iodide and 9.5 ~ 10.5 g of mercuric iodide were dissolved in water, and then the solution was slowly poured into the above 50 mL sodium hydroxide solution under stirring, and diluted to 100 mL with water.

[0074] The following examples are not specified in the specific technology or condition, according to the literature described in the art or according to the product specification; the reagents or instruments used are not specified by the manufacturer, which are conventional products that can be obtained by market.

[0075] Example 1

[0076] The present embodiment provides a sample preparation method for detecting ammonia nitrogen in high sulfate wastewater, which comprises the following steps:

[0077] S1, 10 mL of wastewater to be tested was taken in a 100 mL volumetric flask, 2 mL of 3.5 g / L sodium thiosulfate solution and 1 mL of 100 g / L zinc sulfate solution were added, and the volume was adjusted with pH = 9.5 borate-sodium hydroxide buffer solution, and the first mixture was obtained after first standing for 25 min;

[0078] S2, the first mixture was filtered into a clean container with a water-washed qualitative filter paper, and 20 mL of the initial filtrate was discarded to obtain a separated liquid phase; 20 mL of the separated liquid phase was diluted to 50 mL in a colorimetric tube with ammonia-free water, and 1 mL of 500 g / L potassium sodium tartrate solution and 1 mL of mercuric iodide-potassium iodide-sodium hydroxide solution (16 g / L sodium hydroxide, 7 g / L potassium iodide, 10.0 g / L mercuric iodide) were added and shaken, and then second standing for 15 min to obtain the sample to be tested.

[0079] Example 2

[0080] The embodiment provides a sample preparation method for detecting ammonia nitrogen in high-sulfate wastewater, and the sample preparation method comprises the following steps:

[0081] S1, 10mL of to-be-detected wastewater is taken into a 100mL volumetric flask, 2.5mL of sodium thiosulfate solution with a concentration of 3.0g / L and 0.8mL of zinc sulfate solution with a concentration of 80g / L are added, the solution is diluted with a boric acid-sodium hydroxide buffer solution with a pH value of 9.4, and the first mixture is obtained after first standing for 15min;

[0082] S2, the first mixture is filtered into a clean container by using a qualitative filter paper washed with water, 20mL of the initial filtrate is discarded, and the separated liquid phase is obtained; 20mL of the separated liquid phase is diluted in a 50mL colorimetric tube with ammonia-free water, 0.8mL of potassium sodium tartrate solution with a concentration of 450g / L and 1mL of mercury iodide-potassium iodide-sodium hydroxide solution (12g / L of sodium hydroxide, 10g / L of potassium iodide and 10.5g / L of mercury iodide) are added, the solution is shaken uniformly, and the to-be-detected sample is obtained after second standing for 20min.

[0083] Embodiment 3

[0084] The embodiment provides a sample preparation method for detecting ammonia nitrogen in high-sulfate wastewater, and the sample preparation method comprises the following steps:

[0085] S1, 10mL of to-be-detected wastewater is taken into a 100mL volumetric flask, 2.5mL of sodium thiosulfate solution with a concentration of 3.0g / L and 0.8mL of zinc sulfate solution with a concentration of 80g / L are added, the solution is diluted with a boric acid-sodium hydroxide buffer solution with a pH value of 9.4, and the first mixture is obtained after first standing for 15min;

[0086] S2, the first mixture is filtered into a clean container by using a qualitative filter paper washed with water, 20mL of the initial filtrate is discarded, and the separated liquid phase is obtained; 20mL of the separated liquid phase is diluted in a 50mL colorimetric tube with ammonia-free water, 0.8mL of potassium sodium tartrate solution with a concentration of 450g / L and 1mL of mercury iodide-potassium iodide-sodium hydroxide solution (12g / L of sodium hydroxide, 10g / L of potassium iodide and 10.5g / L of mercury iodide) are added, the solution is shaken uniformly, and the to-be-detected sample is obtained after second standing for 20min.

[0087] Embodiment 4

[0088] The embodiment provides a sample preparation method for detecting ammonia nitrogen in high-sulfate wastewater, and the sample preparation method comprises the following steps:

[0089] The pH of the filtered 1.0 mg / L ammonia nitrogen standard solution was 8.79, and the test result was 0.957 mg / L, which was lower than the actual value.

[0090] Example 5

[0091] The present example provides a sample preparation method for detecting ammonia nitrogen in high sulfate wastewater. The sample preparation method is the same as that of Example 1 except that the volume is adjusted with a pH = 10.0 boric acid-sodium hydroxide buffer solution. The details are not repeated here.

[0092] According to Example 5, the pH of the filtered 1.0 mg / L ammonia nitrogen standard solution was 9.62, and the test result was 1.101 mg / L, which was higher than the actual value.

[0093] Example 6

[0094] The present example provides a sample preparation method for detecting ammonia nitrogen in high sulfate wastewater. The sample preparation method is the same as that of Example 1 except that the volume is adjusted with a pH = 8.8 boric acid-sodium hydroxide buffer solution. The details are not repeated here.

[0095] According to Example 6, the pH of the filtered 1.0 mg / L ammonia nitrogen standard solution was 8.46, and the test result was 0.942 mg / L, which was lower than the actual value.

[0096] Comparative Example 1

[0097] The present example provides a sample preparation method for detecting ammonia nitrogen in high sulfate wastewater. The sample preparation method is the same as that of Example 1 except that the volume is adjusted with a pH = 9.5 boric acid-sodium hydroxide buffer solution. The details are not repeated here.

[0098] Taking Example 1 and Comparative Example 1 as examples, the pH of the first mixture after the first standing was detected, and the pH of the wastewater at different positions in the nickel laterite hydrometallurgical process was tested. The pH values are shown in Table 2.

[0099] Table 2

[0100] Water sample source Example 1 Comparative Example 1 Blank 9.15 8.34 1.0 mg / L ammonia nitrogen standard solution 9.19 8.21 Discharge pool 9.01 8.14 Raw water pool 9.04 8.07 B12 overflow 9.10 8.64 Inlet-1.21 9.08 8.60 Out-1.21 9.12 8.68

[0101] The discharge pool, raw water pool, B12 overflow, Inlet-1.21 and Out-1.21 in Table 2 are wastewater discharged at different positions in the nickel laterite hydrometallurgical production process.

[0102] From Table 2, it can be seen that the method provided by the present application has normal pH after flocculation, while the detection results of Comparative Example 1 are not much different from those of the method of the present application, but at least the scheme of Comparative Example 1 has problems such as easy over-adding of sodium hydroxide, slow adjustment, need to flush the beaker and pH meter, etc., resulting in complex operation, long time and easy human error, and large change in pH after flocculation, leading to low accuracy of subsequent detection results.

[0103] Comparative Example 2

[0104] The present comparative example provides a sample preparation method for ammonia nitrogen detection in high sulfate wastewater, which is the same as Example 1 except that the pH = 9.5 boric acid-sodium hydroxide buffer solution is replaced by a pH = 9.5 boric acid-potassium chloride-sodium carbonate buffer solution, which will not be repeated here.

[0105] The configuration of the pH = 9.5 boric acid-potassium chloride-sodium carbonate buffer solution in the present comparative example includes: dissolving 6.18 g of boric acid and 15 g of potassium chloride in 1000 mL of ammonia-free water, and adjusting the pH to 9.5 with saturated sodium carbonate.

[0106] Comparative Example 3

[0107] The present comparative example provides a sample preparation method for ammonia nitrogen detection in high sulfate wastewater, which is the same as Example 1 except that the pH = 9.5 boric acid-sodium hydroxide buffer solution is replaced by a pH = 10.5 borax-sodium hydroxide buffer solution, which will not be repeated here.

[0108] The configuration of the borax-sodium hydroxide buffer solution in the present comparative example includes: dissolving 9.5 g of borax in 1000 mL of ammonia-free water, and adjusting the pH to 10.5 with saturated sodium hydroxide. Since borax is alkaline, in order to avoid too small amount of sodium hydroxide, the pH is adjusted to 10.5.

[0109] Taking Example 1 and Comparative Examples 2-3 as examples, the reaction of different pH buffer solutions is analyzed, wherein the solution states after the wastewater at different positions in Example 1 and Comparative Examples 2-3 is treated and then the Nash reagent is added are shown in Figures 2-4 The boric acid-sodium hydroxide buffer solution in Example 1 is clear and transparent after the Nash reagent is added. In Comparative Example 2, the boric acid-sodium hydroxide buffer solution is replaced by a boric acid-potassium chloride-sodium carbonate buffer solution, and after the Nash reagent is added in step S2, the solution not only does not color, but also produces white precipitate immediately, see Figure 3 In Comparative Example 3, the boric acid-sodium hydroxide buffer solution is replaced by a borax-sodium hydroxide buffer solution, and after the Nash reagent is added in step S2, the solution has color, but it will gradually become turbid in the second standing process, see Figure 4Therefore, the borate-potassium chloride-sodium carbonate buffer solution and the borax-sodium hydroxide buffer solution are difficult to be applied to the detection of ammonia nitrogen in the hydrometallurgy wastewater of laterite nickel ore.

[0110] Comparative Example 4

[0111] The present comparative example provides a sample preparation method for the detection of ammonia nitrogen in high sulfate wastewater, which is the same as Example 1 except that the mercury iodide-potassium iodide-sodium hydroxide solution is replaced by a mercury dichloride-potassium iodide-potassium hydroxide solution, which will not be described here.

[0112] Specifically, the preparation of the mercury dichloride-potassium iodide-potassium hydroxide solution is as follows: 15.0 g of potassium hydroxide is dissolved in 50 mL of water and cooled to room temperature. 5.0 g of potassium iodide is dissolved in 10 mL of water. Under stirring, 2.50 g of mercury dichloride powder is added to the potassium iodide solution in multiple times until the solution is dark yellow or a light red precipitate slowly dissolves. Stir well and change to dropwise addition of a saturated mercury dichloride solution. When a small amount of carmine red precipitate no longer dissolves, stop dropping. Under stirring, the cooled potassium hydroxide solution is slowly added to the above-mentioned mixture of mercury dichloride and potassium iodide and diluted to 100 mL. Stand in the dark for 24 h. Pour out the supernatant to obtain the mercury dichloride-potassium iodide-potassium hydroxide solution.

[0113] Application Examples 1-6 and Comparative Examples 1-4

[0114] The present application example provides a detection method for the detection of ammonia nitrogen in high sulfate wastewater, which comprises: respectively determining the absorbance of the samples to be tested prepared in Examples 1-6 and Comparative Examples 1-4 at a wavelength of 420 nm, and calculating the ammonia nitrogen concentration by using the absorbance and formula (1):

[0115]

[0116] In the formula, 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).

[0117] In Comparative Examples 2-3, the replacement of the buffer solution leads to turbidity of the sample to be tested, thereby making it difficult to continue the detection. In Comparative Example 4, although the borate-sodium hydroxide buffer solution is still used, the mercury dichloride-potassium iodide-potassium hydroxide solution is replaced by a mercury dichloride-potassium iodide-potassium hydroxide solution, and the accuracy of the detection data is not as good as that of Example 1, indicating that the borate-sodium hydroxide buffer solution is preferably combined with a specific reaction system to significantly improve the accuracy of the detection results.

[0118] First, taking application example 1 and application comparative example 1 as examples, the ammonia nitrogen content of wastewater in the discharge pool, raw water pool, B12 overflow, Inlet-1.21 and Out-1.21 at a certain time was detected, and the results are shown in Table 3.

[0119] Table 3

[0120] Water sample source Example 1 Comparative Example 1 Difference 1.0 mg / L ammonia nitrogen standard solution 0.987 mg / L 0.952 mg / L 0.035 mg / L Discharge pool 6.41 mg / L 6.08 mg / L 0.33 mg / L Raw water pool 6.44 mg / L 6.34 mg / L 0.1 mg / L B12 overflow 6.32 mg / L 5.55 mg / L 0.77 mg / L Inlet-1.21 25.4 mg / L 25.53 mg / L -0.13 mg / L Out-1.21 3.40 mg / L 3.28 mg / L 0.12 mg / L

[0121] As can be seen from Table 3, by comparing application example 1 and application comparative example 1, it can be seen that the method provided by the present application has higher detection accuracy, the standard solution is closer to the actual result, and the buffer solution is directly used for constant volume, so the detection speed is faster.

[0122] The ammonia nitrogen concentration in the discharge pool, raw water pool and B12 overflow at a certain time was detected by the method in application examples 1-6 and application comparative example 1, and the standard addition recovery rate was detected, and the results are shown in Table 4.

[0123] Table 4

[0124]

[0125]

[0126] From Table 4, the following points can be seen:

[0127] (1) From application examples 1-3, it can be seen that the sample preparation method for ammonia nitrogen detection in high sulfate wastewater provided by the present application can achieve high detection accuracy, with a standard addition recovery rate of 97.2-101.1%, and the sample preparation process is simple, fast and has wide application prospects.

[0128] (2) From application example 1 and application examples 4-6, it can be seen that in application example 4, the pH=9.5 boric acid-sodium hydroxide buffer solution is not used for constant volume, but 50 mL of pH=9.5 boric acid-sodium hydroxide buffer solution is added, and constant volume is performed with ammonia-free water, and the final standard addition recovery rate is below 96.4%, and the standard addition recovery rate is low; in application example 5, the pH=10.0 boric acid-sodium hydroxide buffer solution is used for constant volume, and the final standard addition recovery rate is above 106.4%, and the standard addition recovery rate is high; in application example 6, the pH=8.8 boric acid-sodium hydroxide buffer solution is used for constant volume, resulting in a standard addition recovery rate of 95.1% or less; thus, it is shown that the pH of the boric acid-sodium hydroxide buffer solution is controlled within a reasonable range, and the direct constant volume method is used, which can better guarantee the accuracy of the detection and the standard addition recovery rate.

[0129] (3) The final detection recovery rate of the added standard sample in the application of sodium hydroxide solution to adjust pH in Comparative Example 1 is low, indicating that the detection data is low, thus indicating that the application preferably adopts the boric acid-sodium hydroxide buffer solution, which can significantly improve the accuracy of the detection result.

[0130] In summary, the sample preparation method and the detection method for detecting ammonia nitrogen in high sulfate wastewater provided by the application can be well applied to the detection of high sulfate industrial wastewater, especially the detection of laterite nickel ore hydrometallurgy wastewater, and the operation is simple and the result is reliable, which has important significance for the detection and treatment of laterite nickel ore hydrometallurgy wastewater.

[0131] The application is described by the above examples to illustrate the detailed features of the application, but the application is not limited to the above detailed features, that is, it does not mean that the application must rely on the above detailed features to be implemented. It should be understood by those skilled in the art that any improvement of the application, equivalent replacement of the selected technical features of the application, addition of auxiliary technical features, selection of specific modes, etc. fall within the protection scope and disclosure scope of the application.

Claims

1. A sample preparation method for detecting ammonia nitrogen in high sulfate wastewater, characterized in that, The sample preparation method includes the following steps: S1. A first mixture of sodium thiosulfate, zinc sulfate, the wastewater to be tested, and a boric acid-sodium hydroxide buffer solution is prepared and allowed to stand for a first time to obtain a first mixture. The wastewater to be tested is hydrometallurgical wastewater from laterite nickel ore. The sulfate content in the wastewater to be tested is 20~40 g / L. The pH of the boric acid-sodium hydroxide buffer solution is 9.4~9.

6. The volume ratio of the boric acid-sodium hydroxide buffer solution to the wastewater to be tested is (86~87.7):

1. The first mixing process includes: placing the wastewater to be tested in a volumetric flask, adding sodium thiosulfate solution and zinc sulfate solution, and then making up to volume using boric acid-sodium hydroxide buffer solution; S2, Step S1: The first mixture is subjected to solid-liquid separation. The separated liquid phase is then diluted to a final volume to obtain a second solution. The second mixture consists of potassium sodium tartrate, Nessler's reagent, and the second solution, and is allowed to stand for a second time to obtain the sample to be tested.

2. The sample preparation method of claim 1, wherein The magnesium content in the wastewater to be tested was 6~8 g / L.

3. The sample preparation method of claim 1, wherein The sodium content in the wastewater to be tested is 2~4 g / L.

4. The sample preparation method of claim 1, wherein The manganese content in the wastewater to be tested is 2~50 mg / L.

5. The method of claim 1, wherein, The preparation of the boric acid-sodium hydroxide buffer solution includes: dissolving boric acid in water to obtain a boric acid solution, adjusting the pH of the boric acid solution to a target pH using a saturated sodium hydroxide solution, and obtaining the boric acid-sodium hydroxide buffer solution.

6. The sample preparation method according to any one of claims 1 to 3, characterized by, The sodium thiosulfate is added in the form of a sodium thiosulfate solution.

7. The method of claim 1, wherein, The zinc sulfate is added in the form of a zinc sulfate solution.

8. The sample preparation method of claim 1, wherein The sodium thiosulfate solution has a mass concentration of 3.0~4.0 g / L.

9. The method of claim 1, wherein, The zinc sulfate solution has a mass concentration of 80~120 g / L.

10. The sample preparation method according to claim 1, characterized in that, The volume ratio of the sodium thiosulfate solution to the zinc sulfate solution is (1.5~2.5):(0.8~1.5).

11. The sample preparation method according to claim 1, characterized in that, The volume ratio of the sodium thiosulfate solution to the wastewater to be tested is (1.5~2.5):

10.

12. The sample preparation method according to claim 1, characterized in that, Step S1: The first settling time is 15-30 minutes.

13. The sample preparation method according to claim 1, characterized in that, The solid-liquid separation in step S2 includes filtration.

14. The sample preparation method according to claim 1, characterized in that, The solid-liquid separation in step S2 is achieved by using qualitative filter paper filtration.

15. The sample preparation method according to any one of claims 1 to 3, characterized in that, Nessler's reagent is a solution of mercuric iodide, potassium iodide, and sodium hydroxide.

16. The sample preparation method according to claim 15, characterized in that, The concentration of mercuric iodide in the Nessler reagent is 9.5~10.5 g / L.

17. The sample preparation method according to claim 15, characterized in that, The concentration of potassium iodide in the Nessler reagent is 5~10 g / L.

18. The sample preparation method according to claim 15, characterized in that, The concentration of sodium hydroxide in the Nessler reagent is 12~20 g / L.

19. The sample preparation method according to claim 15, characterized in that, The potassium sodium tartrate is added in the form of a potassium sodium tartrate solution.

20. The sample preparation method according to claim 19, characterized in that, The concentration of the potassium sodium tartrate solution is 450~500g / L.

21. The sample preparation method according to claim 15, characterized in that, The volume ratio of the potassium sodium tartrate solution to Nessler's reagent is (0.8~1.2):

1.

22. The sample preparation method according to claim 1, characterized in that, The volume ratio of the potassium sodium tartrate solution to the separated liquid phase is (0.8~1.2):

20.

23. The sample preparation method according to claim 1, characterized in that, The second mixing process includes: taking the separated liquid phase and making up to a volume in a colorimetric tube, and adding potassium sodium tartrate solution and Nessler's reagent.

24. The sample preparation method according to claim 1, characterized in that, The second settling time is 10-20 minutes.

25. A method for detecting ammonia nitrogen in wastewater from laterite nickel ore hydrometallurgical processes, characterized in that, The detection method uses the sample preparation method for ammonia nitrogen detection in high-sulfate wastewater as described in any one of claims 1 to 24 to test the sample.

26. The detection method according to claim 25, characterized in that, The detection method uses absorbance.

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