Development of laccase/graphene oxide membrane for enhanced synthetic dyes separation and degradation

Enzymatic degradation with laccase is a green option for removal of organic compounds from aqueous media. However, the development of high-performance support for immobilization of enzyme is constantly required for the advancement of this technology. In this study the laccase was facilely immobilized on graphene oxide (GO) nanosheets separation membrane, and the membrane's performance as laccase immobilization carrier has been investigated. The results showed that the immobilized laccase on GO-PES membrane exhibited excellent stability towards temperature and pH in the long term and the flux of pure water of biocatalytic membrane was enhanced as well. Synthetic dye degradation was carried out with four representative dyes with different molecular size and structure. The biocatalytic membrane showed substantial improvement of these dyes degradation compared with the GO-PES membrane without laccase immobilized. The relative activity order of the immobilized laccase for the degradation of these dyes was Reactive Brilliant Blue (K-GR) > Reactive Brilliant Blue (KN-R) > Methyl Orange (MO) > Crystal Violet (CV). This order was discussed in terms of correlation between molecular size and structure of dye species. GO coating membranes with catalytic property of laccase offer a new potential approach towards synthetic dye degradation.