Superparamagnetic enzyme-graphene oxide magnetic nanocomposite as an environmentally friendly biocatalyst: Synthesis and biodegradation of dye using response surface methodology

The unique properties of graphene oxide (GO) nanosheets were integrated with the superparamagnetic characteristics of the CuFe2O4 nanoparticles to synthesize the magnetic graphene oxide (MGO), which was chemically modified with 3-amino propyl trimethoxy silane (APTMS) to functionalize the amine group on MGO (MGO-NH2). Afterward, MGO-NH2 was activated with glutaraldehyde (GLU) as a crosslinking agent to synthesize the functionalized MGO (fMGO) and its capability toward covalent Laccase immobilization was investigated. The comprehensive structural analysis using various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) clearly confirmed the covalent attachment of laccase onto MGO. The response surface methodology (RSM), based on Central Composite Design (CCD), was applied to optimize the immobilized Laccase (nanobiocatalyst)-mediated biodegradation of Direct Red 23 (DR23), as an azo dye, by considering independent variables such as nanobiocatalyst dosage, dye concentration, and pH. The optimal conditions to obtain the maximum decolorization yield (95.33%) were nanobiocatalyst dosage = 290.23 mg/L, dye concentration = 19.60 mg/L, and pH = 4.23. The obtained correlation coefficient and the adjusted one of 0.9651 and 0.9336, respectively, imply the nice model fitness. Therefore, structural characterization along with the experimental decolorization results introduced the synthesized superparamagnetic GO as an environmentally friendly nanobiocatalyst for effective decolorization purposes.