Development Of A Technology For Flash Detection Of Organic Pollutants In Water

Pollutants, especially organic pollutants, increased remarkably in wasted water with the fast increase of population and development of economy. It is very important for the environmental protection to detect pollutants quickly and precisely. Spectrophotometry has been one of the most important techniques for water quality analysis for the past hundred years, featuring low cost, easy operation, good sensitivity and high selectivity for many organic pollutants. However, the large volume of the routine spectrophotometer, thus importable, hampers the applications of spectrophotometry in water quality analysis in situ.In this thesis, a new and portable water quality analyzer based on spectrophotometry using photo-diode as the light source is developed for measuring typical organic pollutants, formaldehyde, anionic surfactants and nitrobenzene, in water quickly. The miniaturization of spectrophotometer has been achieved by using a new absorption cell taking advantage of light reflection on a metal film deposited on the internal surface of the cell. Therefore, the light absorbency increases significantly for a given test sample with this reflecting cell owing to increase of the light path, which, in turn, improves the detection limit.The first chapterThis chapter summarizes the pollution in water, especially the sorts of organic pollutants and the corresponding analysis methods, focusing on the principle of spectrophotometry and its applications in the detection of organic pollutants. The principle, properties and advantages of photo-diode as the light source of spectrophotometry is also introduced briefly.The second chapterAnalysis of formaldehyde in aqueous samples was investigated using our spectrophotometry-based water quality analyzer. The detection limit, linear range and the rate of recovery was studied systematically. Comparing with the traditional spectrophotometer, the technique proved to be simple, sensitive and repeatable, showing a great potential for determination of formaldehyde in the water in situ.The third chapterThe methylene blue spectrophotometric method is the national standard to determine the anionic surfactants in water. With our portable water quality analyzer, determination of the anionic surfactants in water by the methylene blue spectrophotometric method has been studied. The results indicates that our technique is not only satisfactory in precision and accuracy but also fast, making it possible to detect water pollution in situ.The forth chapterDetermination of nitrobenzene in aqueous samples with our new technique is described in this chapter based on the N-(1-naphthyl)-ethylenediamine spectrophotometric method. The detection limit, linear range and the rate of recovery were studied and gave satisfactory results, promising an in-situ detection of nitrobenzene in the water.The fifth chapterDesign of a portable spectrophotometer for detecting organic pollutants in water was described in this chapter. The key for miniaturization of instrument is the adoption of reflecting absorption cell and photo-diode light source. The new micro-spectrophotometer is stable and portable.The sixth chapterAn absorption cell for our portable spectrophotometry-based water quality analyzer is described. The surface of the colorimetric plate was deposited a metallic film by vacuum vapor. Light reflects when passing through the test solution, leading to a great increase of absorbency for a given sample, thus increasing the sensitivity and improving the detection limit.