The total nitrogen measured is higher than the blank, how to deal with it?

High-temperature catalytic oxidation.

The high-temperature catalytic oxidation method uses a high-temperature combustion tube or a high-temperature combustion reactor to digest the water sample, and the nitrogen-containing compounds in the sample are converted into NO-gas under the combined action of 850 high-temperature, high-purity oxygen and catalyst. Total nitrogen is determined by continuous flow analysis.

, the sample in the alkaline medium was exposed to potassium persulfate under the condition of 107 110 ultraviolet light.

Oxidized to NO3-.

In the process of measuring total nitrogen by ultraviolet and spectrophotometry, ozone is measured in ultraviolet light.

The free oxygen radicals produced under irradiation react with water to form hydroxyl radicals.

It has strong oxidation ability to organic matter, which can oxidize nitrogen-containing organic matter in water samples to NO3-.

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Ammonia nitrogen is the most important form of nitrogen present in wastewater. Ammonia nitrogen is one of the main pollutants in wastewater treatment because it consumes dissolved oxygen in water when it is converted into nitrite and nitrate in water. Total nitrogen is the sum of organic nitrogen and inorganic nitrogen (including ammonia nitrogen, nitrite nitrogen, nitrate nitrogen), and the total nitrogen content indicates the nutrient status and pollution degree of the water body.

What is the reason for the high absorbance value at the blank value of 275 nm for the determination of total nitrogen in wastewater?

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Ammonia nitrogen is the most important form of nitrogen loss in sewage. Ammonia nitrogen is one of the main pollutants in the treatment of sewage group water because it consumes dissolved oxygen in the water when it is converted into nitrite and nitrate in water. Total nitrogen is the sum of organic nitrogen and inorganic nitrogen (including ammonia nitrogen, nitrite nitrogen, nitrate nitrogen), and the total nitrogen content indicates the nutrient status and pollution degree of the water body.

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You can check whether the C/N ratio is within the control range; 2. In the activated sludge method, the MLSS concentration is to meet the requirements, and whether DO can meet the situation; 3. The total nitrogen is high because your denitrification time is too short, that is, the hypoxia time is too short, or the do control of hypoxia is too high, and the ammonia nitrogen is high because of the nitrification reaction, which is not carried out in time, or the denitrification time is too short.

IDN-BMP is optimized and upgraded on the basis of traditional biological denitrification, and a large number of high-quality denitrifying bacteria can be quickly enriched with special customized fillers, which can recover and play a role within 3 days, and the denitrification efficiency is 3-5 times that of traditional denitrification.

Total nitrogen treatment and enrichment integrated equipment.

Total nitrogen is a general term for nitrate nitrogen, nitrite nitrogen, ammonia nitrogen and organic nitrogen.

The biological denitrification process generally includes three processes of ammonia, nitrification and denitrification, in the whole denitrification process, the microorganisms in each reaction stage are different, there are ammoniating microorganisms, nitrifying microorganisms, denitrifying microorganisms, most of the sewage total nitrogen treatment process completes the conversion of ammonia nitrogen to nitrate and nitrite, but ignores the denitrification reaction, ammonia nitrogen is converted into nitrite nitrogen and nitrate nitrogen, so that ammonia nitrogen decreases, but the total nitrogen is high. In view of this situation, the denitrifying bacteria should be selected firstly, and the IDN-B5 Monterey denitrification complex bacillus can complete the rapid activation of the bacteria within 5 days, meet the requirements of denitrification treatment, and promote the smooth conversion of nitrate nitrogen into nitrogen and release it into the atmosphere.

In an aqueous solution of more than 60, potassium persulfate can be decomposed to produce potassium bisulfate and atomic oxygen, and potassium bisulfate is dissociated in the solution to produce hydrogen ions, so the decomposition process tends to be complete in the alkaline medium of sodium hydroxide.

The decomposed atomic oxygen can convert the nitrogen containing nitride in the water sample into nitrate under the condition of 120 124. And in this process, the organic matter is oxidized and decomposed at the same time. The absorbance A220 and A275 can be measured by ultraviolet spectrophotometry at the wavelengths of 220 nm and 275 nm, respectively, to correct the interference of the absorbance of organic matter at 220 nm.

This method can determine the sum of nitrite nitrogen, nitrate nitrogen, inorganic ammonium salt, dissolved ammonia, and most organic nitrogen-containing compounds in water. The detection range is:

The molar absorbance coefficient of this method is:

Hello Total nitrogen measurement wavelength is 220 and 275nm This is the ultraviolet light area, not the visible light area, so whether you can see the color has nothing to do with the total nitrogen, the effect has not been very good, there are many reasons for Cong Li Da here, no ammonia, drug purity (generally domestic potassium persulfate ammonia nitrogen content is high and can not be used), digestion pressure control (time and gas prevention should be strictly in accordance with the requirements), instrument permeability vertical (two wavelengths you are measured at one time or divided into two times 220 at a time 275 measurement, Some instruments can measure two wavelengths at a time, he has to switch in the middle, a switch wavelength must have an error, of course, it has something to do with the quality of the instrument, anyway, the total nitrogen is not easy to do, you can find experience on the Internet) spectrophotometry to measure the blank value, so what to use as a reference is used to zero, in the measurement of the blank and the sample should not be zeroed, the error may be that the lamp is not enough energy for a long time, the deuterium lamp is not a tungsten lamp, the life is very limited, or the transmittance of the cuvette of the dual-path spectrophotometer is not the same as the silver sample, you have to change two clean, one batch of cuvettes from one manufacturer.

The main methods for determining total nitrogen in water quality are:

1. Alkaline potassium persulfate ultraviolet spectrophotometry (Shishan Jin HJ 636-2012: Nowadays, the main methods of water quality monitoring and search, such as British RAIKING, China Ruiquan and other brands are the mainstream monitoring products optimized on the basis of this standard.

2. Gas phase molecular absorption spectrometry: This method is mainly used in laboratories.

3. Ammonia nitrogen, nitrate, and nitrite are also used for measurement, and then the cumulative value of the results is used as the measurement result of total nitrogen. Typical applications such as the German WTW. In the field of environmental surface water and water quality monitoring, alkaline potassium persulfate ultraviolet spectrophotometry and optimization methods are the main methods at present.

The determination of total nitrogen in water is an important method for environmental monitoring. Total nitrogen is the sum of all nitrogen-containing organic matter and inorganic nitrogen in the water body, including nutrients that are conducive to the growth of organisms, as well as polluting substances that can damage the biological ecological environment. Therefore, the determination of total nitrogen in water is essential for the protection of the environment and the maintenance of human health.

The following is a commonly used method for determining total nitrogen in water, the Kjeldahl method.

1.Principle.

The Kjeldahl method uses amino acids as the standard substance, converts all organic nitrogen and inorganic nitrogen in water into ammonium salts, and then analyzes ammonium salt ammonia into ammonia gas, titrates with acid, and calculates the concentration of total nitrogen. This method is suitable for occasions with high total nitrogen concentration in water samples.

2.Experimental Procedure.

1) Sample processing.

The water sample was added to the beaker, an appropriate amount of sodium hydroxide was added under ventilation conditions, and potassium iodide was used to detect it to neutrality, and then an appropriate amount of ammonium chloride and copper chloride solution was added to neutralize the sodium hydroxide, and then distilled to collect the distillate.

2) Distillation. The sample is poured into a Kjeldahl still for distillation. Heat until the water sample boils, then heat until the sample is dry, then add 40% sodium hydroxide and continue to heat until the water droplets in the collector become lighter.

3) Titration. The distillate is added to the acid for titration until the liquid color changes to light yellow after the addition of HCl. The total nitrogen concentration is then calculated.

Hand Family 3Precautions.

1) Contact with acids and bases should be avoided during the experiment.

2) To prevent ammonia leakage, the experiment should be carried out in a well-ventilated area. Carry silver.

3) Ensure that the distillation time is sufficient to adequately separate the nitrogen elements in the sample.

4) When titrating, it is necessary to pay attention to the titration speed and avoid adding the wrong amount.

In short, there are many methods for the determination of total nitrogen in water, and the Kjeldahl method is one of the more traditional, simple and accurate methods. The required materials and equipment should be fully prepared before the experiment, and the experimental procedures should be strictly followed to ensure the accuracy of the experimental results.