Effects of Different Types of Zeolites on the Degradation Kinetics of Malathion Pesticide in Water
Elly Tety Osewe *
Kinyanjui Technical Training Institute, Nairobi, Kenya.
Victor Shikuku
Kaimosi Friends University College, Kaimosi, Kenya.
Cristiane A. Pereira
Federal University of Sao Carlos, Sao Carlos, Brazil.
Stephen O. Otieno
Maseno University, Kisumu, Kenya.
Audrey Okoyo
Maseno University, Kisumu, Kenya.
*Author to whom correspondence should be addressed.
Abstract
The study examined the effects of selected types of zeolites as an environmentally benign and friendly way to degrade, S-1, 2-bis (ethoxycarbonyl) ethyl O, O-dimethylphosphorodithioate (malathion), used as a model pesticide, from river water. The effect of the size of zeolite channels and dimensionality (such as 1D, 2D, and 3D), Si/Al ratio, and operating pH were studied to find a suitable type of zeolite and conditions to optimize the pesticide degradation. Mordenite (MOR (1D): Si/Al=6.83, and Si/Al=10.72), ferrierite (FER (2D): Si/Al=10.71), ZSM-5 (MFI (3D): Si/Al=6.83 and Si/Al=10.72) and USY (FAU (3D): Si/Al=2.77) zeolites were individually mixed with a water sample collected from Monjolinho River in São Carlos (SP), Brazil and the degradation trend studied. The results showed that all the zeolites accelerated the degradation of malathion. Nevertheless, lower zeolite Si/Al ratio and larger 3D channels or cavities had a positive influence on the degradation rate. The FAU zeolite presented the stronger degradation of the malathion with a half-life of 16.5 followed by ZSM-5 with 24.8, ferrierite with 29.7, and finally mordenite with 30.3 hours.
Keywords: Zeolites, malathion degradation, kinetics