1. Ammonia nitrogen experiment
1.1 Method principle
In the presence of sodium ferrocyanide, ammonium reacts with salicylate and hypochlorite ions to form a blue compound with maximum absorption at a wavelength of 697nm.
1.2 Scope of Application of the Method
Suitable for the determination of ammonia nitrogen in tap water, domestic sewage, and most industrial wastewater.
1.3 Instruments
732PC spectrophotometer; Drip bottle; 10mL stoppered measuring cylinder or colorimetric tube; Volumetric flask (100mL, 1000mL).
1.4 Reagents
10% zinc sulfate solution; 25% sodium hydroxide solution; Ammonium standard storage solution; Ammonium standard intermediate solution; Ammonium standard usage solution; Color developing solution; Sodium hypochlorite solution; Sodium nitrite ferrocyanide solution: Dissolve O.lg sodium nitrite ferrocyanide in 10mL stoppered colorimetric tube, dissolve in water, and dilute to the mark.
1.5 Steps
1) Drawing of calibration curve
2) Determination of water samples
Take 100mL of water sample into a colorimetric tube, add ImL of 10% zinc sulfate solution and 5 drops of 25% NaOH solution, and mix well. Place the sediment, filter it with filter paper, and take an appropriate amount of water sample into a colorimetric tube. Dilute about 8mL with water and add l Mix OOmL of color reagent and 2 drops of sodium ferrocyanide solution. Add 2 drops of sodium hypochlorite solution to dilute to the mark and mix thoroughly. After 1 hour, the absorbance was measured at a wavelength of 697nm. (Simultaneously conducting blank experiments)
1.6 Calculation
Ammonia nitrogen (N, mg/L)=m/v
2 Results and Discussion
2.1 The effect of the dosage of sodium ferrocyanide solution on the color development of water samples
After water sample treatment, different amounts of sodium nitrite ferrocyanide solution were added. At this time, the amount of sodium hypochlorite solution was 0.10mL, and the color change was observed,
According to the experimental results, as the dosage of sodium nitrite ferrocyanide solution gradually increases from low to high, its absorbance also gradually increases. However, when the dosage of sodium nitrite ferrocyanide solution is less than 0.15mL and greater than 0.20mL, the absorbance of the color developing solution is unstable, and the color developing solution appears green. Only when the dosage of this solution is between 0.15-0.20mL, which meets the national standard method and is a blue compound, 0.20mL of sodium nitrite ferrocyanide solution is selected as the best choice for this experiment.
2.2 The influence of sodium hypochlorite solution dosage on water sample color development
After water sample treatment, different amounts of sodium hypochlorite solution are added. At this time, the amount of sodium ferrocyanide solution used is 0.20mL, and the color change is observed