Pyrite-assisted degradation of methoxychlor by laccase immobilized on Fe3S4/earthworm-like mesoporous SiO2

Abstract

Laccase immobilized and cross-linked on Fe₃S₄/earthworm-like mesoporous SiO₂ (Fe₃S₄/EW-mSiO₂) 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 8 h, 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 Fe₃S₄/EW-mSiO₂ was attributable to the pyrite (FeS₂) impurity in Fe₃S₄, which could act as an electron donor in reductive dehalogenation. Sulfide groups and Fe²⁺ 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 Fe₃S₄/EW-mSiO₂ was determined via mass spectroscopy of the degradation products. This study is a new attempt to use pyrite to support immobilized laccase degradation.

Keywords: Fe3S4/earthworm-like mesoporous SiO2; Immobilized laccase; Methoxychlor.