Study On The Photodegradation Of Nitrbenzene In Water

The nitrobenzene and its ramification are commonly used as the organic chemistry raw material for the industries of dye, medicine, agricultural chemicals, rubber and spice. However, if they enter the waters, they will become the virulent harmful pollutants. Nitrobenzene is toxious, and its toxicity is generally 20-30 times higher than that of other compounds, and it is weakly mutagenic. The long-term contact with it is deleterious for the human and the animals. At the present, the industry developing process brings structural pollution to the domestic big rivers, causing the organic pollution in the water environment becomes more and more serious, and the nitrobenzene pollutants have be listed as the pollutants which we should give priority to control home and abroad. So in laboratory conditions, we do research about the distribution of nitrobenzene in ice and water at icing processes, and about photodegradation of nitrobenzene in ice and water, the factors influencing photodegradation. And the intermediate products and synthetic biological toxicity of the photodegradation of nitrobenzene in water are preliminarily studied in this paper.In the paper we establish the method to test nitrobenzene in the water. We test nitrobenzene in the water sample by means of liquid chromatography, and the test results show that when the nitrobenzene concentration is between 1.0 and 1000μg·L^-1, the peak area correlates linearly with the nitrobenzene concentration well, so the result is satisfactory.We investigate the distribution of nitrobenzene in ice and water at icing processes through simulation of nature water's icing experiments, the result shows that in the course of nitrobenzene aqueous solution ice accretion, nitrobenzene reapportion in water and ice. Most of the nitrobenzene(96%⁹8%) in water, the concentration of nitrobenzene in ice is less(2%⁴%).With different irradiation sources, the photochemical degradation of NB was studied. And the influence of different illumination intensity, pH Value and soluble matter in river water on the photodegradation of NB was investigated. Nitrobenzene could be degraded remarkably under ultraviolet radiation, and the photodegradation of NB is first-order reaction. The rate constants(k) of the photodegradation of nitrobenzene in ice under ultraviolet radiation is 0.268h^-1, the half-life is 2.59h. The rate constants(k) of the photodegradation of nitrobenzene in water under ultraviolet radiation is 0.00585min^-1, the half-life is 118.5min. Exposed to intensity of solar radiation in February and march , The rate constants(k) of the photodegradation of nitrobenzene in ice is 0.045h^-1, the half-life is 13.6h, the rate constants(k) of the photodegradation of nitrobenzene in water under ultraviolet radiation is 0.042⁰.059h^-1, the half-life of photodegradation of NB in river water which below the river surface about 30⁴0mm is about two days. The attenuation regularity of ultraviolet light intensity in ice or water follows an exponentially attenuation law. The rate constants(k) of the photodegradation of nitrobenzene decreases with the increase of the ice layer thickness.when layer thickness more than 30mm, it can be neglected. Under the acidic condition the reaction rate increased while unchanged under alkalinity condition. And the photodegradation rate of NB has been stimulated when there were humic substance and various impurities in river water.LC-MS analysis on nitrobenzene aqueous solution of different photodegradation stages showed that some new material were produced in the process, whose cytoplasma/nucleus ratio.is 108.04, was thought as nitrophenol.Nitrobenzene aqueous solution in different stages of photodegradation was analyzed by DeltaTOX toxic analysor. The detection index is photogenic bacteria loss ratio. The result shows that at the initial stage the comprehensive toxicity is slightly increased, whereas with the prolonging of reaction time the comprehensive toxicity decreased, lower than original sample.