Facile and Controlled Fabrication of Cu–Al Layered Double Hydroxide Nanosheets/Laccase Hybrid Films: A Route to Efficient Biocatalytic Removal of Congo Red from Aqueous Solutions

The development of biobased hybrid materials that can efficiently remove environmentally contaminants has broad practical applications for areas. In this work, a novel biomaterial–inorganic hybrid film was fabricated with Cu–Al layered double hydroxide (LDH) nanosheets as host and laccase as guest by using exfoliation/self-assembly monolayer technology. It included two processes: first, a nitric acid intercalation Cu–Al–NO3– LDHs was prepared with Cu–Al–CO32– LDHs through the ion-exchange method, and then Cu–Al–NO3– LDHs was exfoliated into a single-layer nanodispersion system with abundant Cu2+ ions on the surface of the positively charged layered double hydroxides to assemble the (LDHs/laccase)n hybrid multilayer film. The resulting (LDHs/laccase)n hybrid film was characterized by X-ray diffraction, scanning electron microscope, high-resolution transmission electron microscopy, scanning probe microscope, and UV–visible absorption spectroscopy, which all supported the formation of the layer-by-layer sandwich structures. The performance of the as-prepared film was evaluated for efficient biocatalytic removal of congo red from aqueous solutions. The loaded amounts of laccase of (LDHs/laccase)n were estimated to be 0.0626 mg/cm2 (n = 10), 0.1731 mg/cm2 (n = 30) and 0.2809 mg/cm2 (n = 50) by Bradford protein assay method. Taking advantage of the combined benefits of LDH and protein, the as-prepared (LDHs/laccase)n hybrid film exhibited high uptake removal performance and high storage stability in contrast with free laccase. The superior removal performance of (LDHs/laccase)n hybrid film supports a potential strategy for decontamination of congo red dye from wastewater, and it may provide new insights for efficient removal of dye in environmental pollution cleanup.