Pyrite-Assisted Degradation of Methoxychlor by Laccase Immobilized on Fe3s4/Ew-Msio2

Abstract Laccase immobilized and cross-linked on Fe 3 S 4 /earthworm-like mesoporous SiO 2 (Fe 3 S 4 /EW-mSiO 2 ), was used to degrade methoxychlor (MXC) in aqueous environments. The effects of various parameters on the degradation of MXC were determined using free and immobilized laccase. Immobilization improved the thermal stability and reuse of laccase significantly. Under the conditions of pH 4.5, temperature 40°C and reaction time 8h, the degradation rate of MXC by immobilized laccase reached a maximum value of 40.99% and remained at 1/3 of the original after six cycles. The excellent degradation performance of Fe 3 S 4 /EW-mSiO 2 was attributable to the pyrite (FeS 2 ) impurity in Fe 3 S 4 , which could act as an electron donor in reductive dehalogenation. Sulfide groups and Fe 2+ reduced the activation energy of the system resulting in pyrite-assisted degradation of MXC. The degradation mechanism of MXC in aqueous environments by laccase immobilized on Fe 3 S 4 /EW-mSiO 2 was determined via mass spectroscopy of the degradation products. This study is a new attempt to use pyrite to support immobilized laccase degradation.