Inclusion effect of alpha-cyclodextrin on chemical degradation of malathionin water

Chemical degradation of malathion in water is one of the important environmental processes of malathion, and plays a critical role in detoxification of malathion. Alpha-cyclodextrin (alpha-CD), one of the cyclic oligosaccharides different from beta-cyclodextrin (beta-CD) in glucose units, solubility, and size of cavity, is capable of producing an environmental effect different from those of the latter CD and its derivatives. This work evaluated the effect of alpha-CD on chemical degradation of malathion in water in an attempt to further study the effects of different CDs on hydrolysis of malathion and assess the potential applications of alpha-CD in remediation of malathion contamination. The results showed that alpha-CD had a remarkable facilitative effect on the hydrolysis of malathion in both buffer solutions and natural surface waters. The facilitative effects of alpha-CD were an obverse function of pH value and inverse function of temperature. The rate constant of malathion hydrolysis increased with increasing the concentration of alpha-CD in both types of waters. Urea, a compound widely used in agriculture, decreased the facilitative effect of alpha-CD at 25 degrees C and pH 9.0. The formation of inclusion complexes between alpha-CD and malathion was evidenced by nuclear magnetic resonance studies.