Monitoring of organochlorine pesticides in surface waters in Hanoi and detoxification of organochlorine and organophosphorus pesticides in water by applying novel methods using ultraviolet irradation, air ionisation and solar photocatalysis

Abstract

This thesis can be divided into two major parts: Monitoring of selected organochlorine pesticides in surface waters in Hanoi and Study on the applying of novel Advance Oxidation Processes-AOP (Air Ionisation and Solar Photocatalytic Oxidation) for the detoxification of waters containing toxic organochlorine and organophosphorous pesticides, which are some well-known insecticides like Lindane, 4,4à ´-DDT, Methamidophos (Me) and Monocrotophos (Mo). The monitoring process was undertaken with the same procedure in two years (in the Dry Season: Nov. 1998 and in the Rainy Season: Aug. 1999) for an evaluation of the contamination of 15 organochlorine pesticides in surface waters, by sampling of 30 water samples from different sites (Red and Duong Rivers, irrigation canals, lakes and wells) on an area of à » 30 by 20 km in Hanoi and its surroundings. The photodegradation of Me and Mo was first undertaken using the 2 UV High- and Low Pressure Mercury Lamps with addition of H:sub:2:/sub:O:sub:2:/sub:, then with a new developed reactor Ionised Air Pilot System 2 (IAPS-2). The photocatalytic detoxification of Me and Mo (C:sub:0:/sub: = 10 mg l:sup:-1:/sup:) was investigated using a Lab Solar Simulated Reactor (LSSR) and a new kind of solar non-concentrating Double Skin Sheet Reactor (DSSR). 12 diverse different commercial, modified and novel photocatalysists (TiO:sub:2:/sub: at concentrations of 500 and 1000 mg l-1), which are mostly pure anatase TiO:sub:2:/sub: powder, except well-known catalyst P25 Degussa were tested with those reactors in the photocatalytic degradation of Me and Mo at different pH values of 3, 7, 12. An initial detailed possible photocatalytic oxidation mechanisms of the degradation of Me and Mo has been found by combination of a proposed general photocatalytic oxidation mechanism of an organic pollutant (assuming an initial oxidative attack by a hydroxyl radical to a methyl group) with the molecular structures of identified intermediates.