Reductive lindane degradation with tea extracts in aqueous phase

Abstract

Lindane is a persistent organochlorine pesticide (OCP) that is chemically stable, and has high lipid solubility. These characteristics allow it to bioaccumulate through the food chain, and therefore its presence in the environment is of great concern. An environment friendly chemical reductive process using tea in conjunction with Fe2+ was developed to degrade lindane in the aqueous phase. Tea containing rich polyphenols is a reducing and chelating agent. This bench-scale study investigated the potential of various tea extracts to reductively degrade lindane, and the results revealed that green tea extract (GTE) exhibited the greatest reducing power, and radical scavenging ability, compared with other tea extracts. The GTE/Fe2+ system produced polyphenol organometallic iron complexes, resulting in a highly reducing environment, and was able to completely degrade lindane within 3 h in a pH 10 (bi)carbonate buffer solution at 20 °C. Moreover, it was observed that increasing the concentration of GTE from 0.05 to 1.00 g (60 mL)−1 in a fixed 30 mM Fe2+ solution resulted in increases of initial lindane reaction rates (r0, lindane) from 1.32 to 7.80 μM h−1. However, as the Fe2+ dosage increased, with a fixed concentration of GTE, the r0, lindane decreased due to GTE deficiency and a reduced Fe2+/Fe3+ ratio in the iron complexes. Based on the lindane degradation intermediates detected by Gas Chromatography/Mass Spectrometry, the lindane degradation mechanism was postulated to be via alkaline hydrolysis and sequential reductive dechlorination.