Removal of Pharmaceuticals from Water Using Laccase Immobilized on Orange Peels Waste-Derived Activated Carbon

The ongoing discharge of containments into the environment has raised concerns about the potential harm they pose to various organisms. In the framework of eliminating pharmaceutical chemicals from aqueous solutions, enzymatic degradation by laccase is an environmentally friendly option. In this investigation, laccase immobilized on biochar derived from agricultural waste (orange peels, OPs) was used for the first time to remove carbamazepine and diclofenac from aqueous media. Different characterizations, such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-Ray diffraction (XRD), specific surface area (SBET), Boehm titration, proximate and ultimate analysis, as well as the point of zero-charge (pHPZC) analysis, were used in this study. The immobilization of laccase results in enhanced stability with respect to storage, temperature, and pH compared to laccase in its free form. The findings showed that the ideal conditions for immobilization were a pH of 4, a temperature of 30 °C, and a laccase concentration of 4.5 mg/mL. These parameters led to an immobilization yield of 63.40%. The stability of laccase immobilized on biochar derived from orange peels (LMOPs) was assessed over a period of 60 days, during which they preserved 60.2% and 47.3% of their initial activities when stored at temperatures of 25 °C and 4 °C, respectively. In contrast, free laccase exhibited lower stability, with only 33.6% and 15.4% of their initial activities maintained under the same storage conditions. Finally, the use of immobilized laccase proved to be effective in eliminating these pollutants in up to five cycles. Upon comparing the two systems, namely LMOPs and modified orange peels (MOPs), it becomes apparent that LMOPs exhibit an estimated 20% improvement in removal efficiency. These results affirmed the viability of activated carbon derived from OPs as a cost-effective option for immobilizing laccase. This approach could potentially be further scaled up to effectively eliminate organic pollutants from water sources.