GB/T 4918-1985 Determination of total nitro compounds in industrial wastewater - Spectrophotometric method
Some standard content:
National Standard of the People's Republic of China
Determination of total nitro compounds in industrial wastewater
Spectrophotometric method
Waste water from manufacturing processDeterminsttan of taral ttrs copoundsSpectrophotometric method
UDC 628.54
GB4918-85
This method is applicable to the determination of the sum of trinitro compounds (calculated as 2,4.6-nitrotoluene), mononitro compounds and dinitro compounds (calculated as 2,4-dinitrotoluene) in TNT wastewater. The nitro compounds determined by this method refer to the determination of mononitro compounds (in terms of 2,4,6-nitrotoluene) in wastewater by sodium sulfite-chlorohexadecylpyridine-diethylaminoethanol (referred to as CPC method), and the determination of 1-nitro compounds and dinitro compounds (in terms of 2,4-dinitrotoluene) in wastewater by zinc powder reduction, sodium nitrite diazotization, N-methylvinyl dihydrochloride (referred to as zinc powder reduction method). It is believed that the sum of the above is close to the concentration of total nitro compounds. 1 Determination of trinitro compounds (EPC method)
1.1 Principle
1.1.1 Trinitro compounds such as 2,4,6-nitroformaldehyde (α-TNT) generate sensitive colored addition compounds in sodium sulfite-chlorohexadecylpyridine-diethylaminoethanol solution. The absorbance is measured at a wavelength of 465nm and its concentration is calculated (in terms of α-TNT).
1.2 Instruments
In addition to general electrochemical analysis instruments, the following should be available: 1.2.1 Spectrophotometer
1.2.2 Colorimetric tube with stopper: 25ml.
t.3 Reagents
The reagents used in this method are analytically pure except those specified; all percentage concentrations are weight-volume percentages except those specified.
Sodium sulfite: 5% is valid for three days.
Fluorohexadecanepyridine: 0.3%, expressed as CPC. Ethylamine ethanol: 3%, expressed as DEAE, valid for two days. Concentrated sulfuric acid: specific gravity 1.84.
Sulfuric acid: 7.5% solution.
2,4.6-Dinitrotoluene standard solution: Accurately weigh 10.0mg (accurate to 0.0002g) of 2,46-trinitrotoluene standard sample, add 2-3ml of concentrated sulfuric acid, and transfer it to a 1000ml bottle after complete decomposition, and dilute it to the scale with distilled water. 1ml of this solution is equivalent to 10ug 2,4.6-nitrotoluene. 1.4 Operation steps
1.4.1 Standard 1. Draw the curve
Pipette 0, 0.5, 1.0, 3.0, 5.0, 7.0 ml of the standard solution into a 25 ml colorimetric tube, dilute to 10 ml, add 2.0 ml of 7.5% sulfuric acid solution, shake, add 1.5 ml of 5% sodium sulfite solution, shake well, add 2 ml of 0.3% oxo-1-hexadecylpyridine solution National Environmental Protection Agency 19 May 01-18 Issue 172
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GB 491B85
and 2% diethylhydrogen alcohol solution, ml, dilute to 25 ml, shake and then use 1 cm colorimetric blood to zero with distilled water, and measure the absorbance at a wavelength of 465nm. The ordinate is absorbance, and the abscissa is the 2.4,6-trinitrotoluene content (g). Take the average value of 3 times and calculate by the back door method to draw a standard curve.
1.4.2 Determination of water samples
Take a certain amount of water sample (determine the sampling volume according to the content, and dilute to 10ml when it is less than 10ml). Add reagents according to the same operating steps as the standard working curve to develop the color, and then measure the absorbance. 1.5 Calculation
Dinitrotoluene compound concentration (calculated as 2,4.6-trinitrotoluene) Calculate the trinitrotoluene compound (mg/l) according to formula (1)\
Where: w-
The content of 2,4.6-trinitrotoluene in the standard working curve obtained by the absorbance of the water sample to be tested,! - the volume of the water sample, ml.
1.6 Determination error
When the wastewater concentration is less than 1.0mg/1, the relative error is allowed to be no more than 10%. When the wastewater concentration is greater than 1.0mg/1, the relative error is no more than 5%.
1.7 Notes
When the wastewater chromaticity is large, the same volume of water sample can be taken and diluted with water to make a 25㎡ empty space to offset the influence of chromaticity. 1.72When the acidity of the water sample is very high and the volume of the water sample is large, the amount of sulfuric acid added can be reduced to keep the pH of the solution after color development equal to 7.0~9.0.
1.7.3When there are visible suspended matter in the water sample, it should be filtered before measurement. 1.7.4If the water sample concentration is very high, it can be diluted before measurement. 2
Principle of determination of mononitro compounds and dinitro compounds
In strong acid, aromatic mononitro compounds and dinitro compounds can be reduced to amino compounds by zinc powder, and then sodium nitrosaldehyde is added to undergo diazotization reaction to generate diamine compounds. Excess nitrate ions are removed by ammonium sulfonate, and then N-methylethyleneamine dihydrochloride is added to couple with the diazonium compound to generate a purple-red azo compound. 2.2 Instruments
In addition to general chemical analysis instruments, the following should be available: 2.2.1 Spectrophotometer
2.2.2 Colorimetric tube with stopper.
2.3 Reagents
The reagents used in this method are analytically pure except those specified. All percentage concentrations are weight-volume percentages except those specified.
2.3.1 Hydrochloric acid: 1:1, specific gravity 1.19.
Sodium nitrite: 0.5%, valid for two days. 2.9.3 Zinc powder.
Concentrated sulfuric acid: specific gravity 1.84.
Ammonium sulfamate: 2.6%, valid for X weeks. 2.3.6N-naphthylamine dihydrochloride: 1%, valid for three days. 2.3.72.4~_Dinitrotoluene standard solution: Accurately weigh 10.0mg (accuracy 0.0002g) 2,4-dinitrotoluene standard sample r, add 2-3ml sulfuric acid, dissolve it completely, transfer it to a 1000ml volumetric flask, and dilute it to the mark with distilled water. 1ml of this solution is equivalent to 10.0μg 2,4-dinitrotoluene.
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2.4 Operation steps
: 2.4.1 Draw the curve on the standard
GB4918--85
Take 0, 0.5, 1.0, 1.5, 2.0, 2.5ml of standard solution respectively Liquid in a 25ml colorimetric tube, add 0.2g zinc powder, dilute to 3ml, add 3ml 1:1 hydrochloric acid, and then add 1 drop of 2% copper sulfate. After reacting for 30min, filter into another colorimetric tube, wash the colorimetric tube and funnel 3-5 times with 2-3ml distilled water each time (the total volume of the solution after filtering and washing does not exceed 20ml), cool the colorimetric tube in cold water (10-15℃), add 1.5ml sodium nitrite solution, shake and mix well, and then place for 5min, add 2.5ml ammonium sulfamate, shake 2-3 times, and place for 5mi1, then add 0.5ml N-naphthyl-diamine dihydrochloride, accurately dilute to 25ml with distilled water, mix, and place for 20min. Use 1cm colorimetric pipette to adjust to zero with distilled water, and measure the absorbance at a wavelength of 540nm. Take the average value of 3 measurements, and draw a standard working curve with the ordinate as the absorbance and the abscissa as the equivalent of 2,4-dinitrotoluene (). Determination of water samples
Take 0.5~3.0ml of water sample, up to 5ml, and measure its absorbance according to the standard curve exploration steps (24). In order to eliminate the interference of other components, take another water sample of the same volume without adding zinc powder, and measure its absorbance according to the standard working curve operation ().
2.5 Calculationwww.bzxz.net
Nitro compounds and dinitro compounds (calculated as 2,4-dinitrotoluene) Connect formula (2) to calculate the amount of mononitro compounds and dinitro compounds (mg/1), V
Formula: W——-modified absorbance element-A From the curve, the equivalent 2.4~dinitrotoluene content is obtained, V=the volume of the water sample taken, ml.
2.6 Determination error
When the wastewater concentration is less than -1.0m/1, the allowable determination error is not more than 15%, and the wastewater siltation is greater than 1.0mg/1, the allowable measurement error is not more than 10%.
2.7 Precautions
2.7.1 During the reaction process of this method, the product is easily decomposed by light, so it should be operated away from direct light or strong light. 2.7.2 When the concentration is greater than 50m/1, it should be diluted for determination. 2.7.3 When the sample contains trinitrotoluene, it can be determined and corrected according to Chapter 2 (CPC method). The correction method is shown in formula (3). The actual measured content = C,
where: Cl
the concentration of trinitrotoluene,
the concentration of mononitro compounds and dinitro compounds determined by zinc powder reduction. 3 Calculation of the total nitro compound concentration in wastewater The total nitro compound concentration (mg/1) in wastewater is calculated according to formula (4). Total nitro compound concentration (m/) = X + X,
formula, X, the concentration of blue nitrotoluene calculated as 1.5, ng/1; X, the concentration of nitro compounds and dinitro compounds calculated as 2.5, mg/]. 174
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(3)
Additional remarks:
GB 4918-85
This standard was proposed by the former State Council Environmental Protection Leading Group. This standard was drafted by the Fifth Design Institute of the Ministry of Ordnance Industry and the State-owned Qingyang Chemical Plant. The main drafters of this standard are Lu Yongsen, Sun Lin and Yuan Shuqing. This standard is entrusted to the environmental protection department of the Ministry of Ordnance Industry for interpretation.
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