Influence of UV Radiation on the Spectral Properties of 2-METYL-4-Chlorophenoxy Propionic Acids
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INFLUENCE OF UV RADIATION ON THE SPECTRAL PROPERTIES OF 2-METYL-4- CHLOROPHENOXY PROPIONIC ACIDS I. V. Sokolova, A. A. Solokha, and O. N. Tchaikovskaya
UDC 539.194:535.37
The influence of UV radiation on the spectral properties of 2-methyl-4-chlorophenoxy propionic acid (mecoprop) is studied. An effective high-power excimer barrier-discharge lamp based on working mixtures of krypton with low-aggressive halogen molecules (λ ~ 222 nm) is used as a source of UV radiation. It has been found that under stationary conditions, the use of a flow-through photoreactor for photodegradation of mecoprop is more efficient than the use of an excilamp. The degree of photodegradation depends on the exposure time. Keywords: 2-methyl-4-chlorophenoxy propionic acid, herbicide mecoprop, absorption, UV radiation, excilamps.
INTRODUCTION The application of herbicides plays an important role in a productivity increase in agriculture. It should be noted that production, application, and assortment of pesticides, including herbicides, increases in the world every year. From the total production and application of pesticides in the world, herbicides account for more than 50% [1]. Over the last decades, the application of pesticides and herbicides in agriculture has led to a significant increase of stable organic compounds in natural water [2]. A study of transformations of stable toxic compounds in nature and a choice of optimal methods of herbicide utilization are important problems of environmental protection and rational use of natural resources. Chlorinated substances are carcinogens and are accumulated in fatty tissues of living organisms [3, 4]. In this connection, the interest increases to removal of these pollutants from the environment after their application [5]. Ultraviolet (UV) radiation with quantum energy comparable to the energy of a chemical bond is the unique tool for initiating and performing many physical and chemical processes on the surface and in the volume of various media [6]. UV radiation can be used not only for disinfection of water and air, that is, for removal of pathogenic microorganisms, but also for decomposition of complex organic compounds. This method can be used both independently and in combination with other technologies [7]. In this regard, a study of the efficiency of new UV radiation sources that may influence various electronically excited states of organic molecules becomes relevant. Such sources are exciplex lamps that are increasingly used for toxicant photolysis [8]. Physical and technical premises for photochemical applications are the following excilamp properties: narrow-band radiation spectrum, high energetic luminosity in the wavelengths ranges where effective sources of radiation of other types are lacking, absence of mercury in the gaseous mixture, ample design possibilities, photon energies from 3 to 10.5 eV sufficient for application in all known photoprocesses in which UV or VUV radiation is required, and long service life (from 1 000 to 10 000 h). The influence of short-wavelength o
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