Determination Of Total Nitregen Based On Ultrasonic Oxidation And Ultraviolet Spectra

With the rapid development of human society, there are increasing wastewater and domestic sewage poured into rivers, lakes and sea, which aggravated water eutrophication. What’s more, total nitrogen is the main factor that caused water eutrophication. Therefore, it is the importance of detecting the content of total nitrogen(TN) in order to strengthen controlling the emission of polluted water. The traditional detection of TN with the complicated operation based on chemical reagents can easily give rise to the recontamination. As a result, it is of considerable realistic significance to build a environmental friendly and efficient detection system, which could have limitless applications.This paper have been studied in oxidative digestion, interfering substance and model selecting, building the water total nitrogen detection system and data analysis model. The main achievements are as follows.First, there is a introduction of basic principle of ultrasonic cavitation and chemometrics algorithms of ultraviolet spectrum. MLR(Multiple Linear Regression) algorithm and PLS(Partial Least Squares) algorithm are explained in detail.Second, spectral characteristics of the main substance which have absorbance in ultraviolet band are studied. Based on the composition of seawater, experimental study of the influence of other substances in seawater on the measurement of nitrogenous substances using UV absorption spectra are made. The main interfering substances are chlorideion and bromineion. Meanwhile, the linear absorption range of nitrogenous substances is researched.Third, the detection system based on ultrasound oxidative digestion and UV absorption spectrometer is designed. Analysing the factor that affect ultrasonic cavitation, the optimal frequency range is confirmed. Experimental study of the optimal reaction time for ammonia- nitrogen are made. Oxidizing the TN liquid in the presence of ultrasonic wave.Finally, Established the best modeling method for measuring the concentration of nitrogenous substances using ultraviolet spectra. Different concentration and combinations of four compounds were added into distilled water to build the modeling samples. Established the correction model through MLR(Multiple Linear Regression) algorithm and PLS(Partial Least Squares) algorithm. After comparing the result, the PLS algorithm is recognized as the optimal model approach.