TiO2 Sol-Gel Coated PAN/O-MMT Multi-Functional Composite Nanofibrous Membrane Used as the Support for Laccase Immobilization: Synergistic Effect between the Membrane Support and Enzyme for Dye Degradation

Abstract

Removal of a triphenylmethane dye (crystal violet, CV) by a simultaneous enzymatic-photocatalytic-adsorption treatment was investigated in this work. A desirable synergistic effect on dye treatment was achieved by decorating laccase (Lac) onto the surface of TiO₂ sol-gel coated polyacrylonitrile/organically modified montmorillonite (PAN/O-MMT) nanofibers prepared by electrospinning. The assembly of Lac on the surface of PAN/O-MMT/TiO₂ nanofibers was confirmed by confocal laser scanning microscope (CLSM). In comparison with free Lac, the immobilized Lac showed better pH, temperature and operational stabilities, reaching highest relative activity at an optimum pH of 3 and optimum temperature of 50 °C. Therefore, the immobilized Lac displayed a higher degradation efficiency of CV at an initial dye concentration of 100 mg/L, an optimum pH of 4.5 and temperature at 60 °C. Under UV illumination, the CV removal efficiency was further improved by ~20%. These results demonstrated that the Lac-immobilized PAN/O-MMT/TiO₂ composite nanofibers with a combined effect between the immobilized enzyme and the polymeric support have potential for industrial dye degradation.