Kinetic Studies of Malathion Dissipation Degradation in Lake Victoria Water in the Presence of Zeolite

Abstract

Malathion is an organophosphorus pesticide widely employed in controlling pests in agriculture, household, stored grains, greenhouse, forestry and public health. Malathion usually adsorbs on soilsand through surface runoff or leaching, it fmds its way into rivers and lakes whose waters the local population rely on for their domestic use. The current water treatment methods are not efficient in getting rid of malathion and its degradation products. Zeolites which are crystalline aluminosilicates with tetrahedral framework structure enclosing cavities can be effective alternatives for mopping malathion from water due to their abilities to abstract and enhance degradation of water pollutants. Although zeolites have" been reported to degrade malathion faster, the kinetics of such zeolitic action has not been documented. The objective of this study was to determine the degradation kinetics of malathion in fresh water and to compare the effectiveness of Faujasite X and Y in removal of malathion. Experiments were set up in a laboratory at 27°C and repeated three times. Water samples were collected from Asembo bay (0010'S, 34°25'E) and different concentrations (10 and 20 ppm) of malathion spiked in the water samples. After 1, 2, 4, 6 hours and thereafter increasing the previous time upto 768 hours, 40 mL was sampled from each concentration, extracted using dichloromethane and cleaned on a florisil column then analyzed using GC-NPD to determine the concentrations and GC-MS for confirmation ofthe degradation products. Quantification was based on peak area responses using the internal standard method and concentrations corrected for recovery. The solid Faujasites were characterized using IR to establish ifthere was adsorption in the zeolite matrix and XRD to determine any changes in the position of the Na+. The data was linearly regressed to obtain the relationship between time and malathion concentration. Malathion degradation in fresh water followed a pseudo first order kinetics with a rate constant of -0.144 ± 0.010 hr-I. The calculated