Laccase immobilized on reduced graphene oxide sponges for simultaneous adsorption and enzymatic degradation of endocrine disrupting chemicals.

Abstract

The presence of endocrine disrupting chemicals (EDCs) in water can impart detrimental effects on public health by mimicking the behaviors of natural hormones and their associated receptors in human body. Studies have demonstrated that ligninolytic enzymes such as laccase can degrade various phenolic compounds, including a broad range of EDCs. In this study, the technique of covalent immobilization of laccase through carbodiimide coupling chemistry on highly adsorptive reduced graphene oxide (rGO) sponges was utilized to effectively remove two representative EDCs; namely, bisphenol A (BPA) and triclosan (TCS) from water. The bio-functionalized adsorbent (rGO-LA) showed a significant improvement in removing BPA (87 % after 24 h) compared to pristine rGO sponge, (~40 % after 24 h). The removal efficiency of both adsorbents for TCS was as high as 84 %, with faster kinetics being observed for rGO-LA. Further investigation using gas-chromatography-mass spectroscopy revealed that the bio-functionalization not only improved the removal efficiency of the adsorbent, but also facilitated the adsorption of the metabolites generated during the biodegradation of BPA and TCS. When temperature was increased to 40 °C, the removal efficiency and kinetics of rGO-LA sponges were improved significantly for BPA (83 % removal in 4 h) and TCS (73 % removal after 4 h). The study highlights the synergy of enzymatic degradation and adsorption, with enhanced performance observed at elevated temperatures, offering a promising solution for effective EDCs mitigation in water treatment, while also ensuring comprehensive contaminant removal by adsorbing the generated metabolites.