Adsorption of Congo Red Using Magnetically LDHs Immobilized Lipase Bionanomaterials in Wastewater

The removal of dye pollutants from water bodies is a significant global issue due to their negative effects on both ecosystems and human health. For this purpose, effective and selective α-FeOOH-Fe₃O₄@Chitosan-LDHs@Lipase (MF@CS-LDHs@LIP) magnetically bionanomaterials were synthesized via co-precipitation and cross-linking methods for uptake of Congo red (CR) from wastewater. Comprehensive characterization of both the carrier and MF@CS-LDHs@LIP was performed using SEM, FTIR, XRD, BET, VSM, and EDX. The analytical results confirmed the successful immobilization of lipase on the composite carrier. The immobilization conditions and enzymatic properties of the enzyme were investigated. The results demonstrated that the immobilized lipase maintained over 60% relative activity within a pH range of 7.0-11.0. Notably, at pH 11.0, its activity was 1.69 times higher than that of free lipase. Both immobilized and free lipase exhibited significant activity reduction at temperatures exceeding 40 °C. At 55 °C, the immobilized lipase exhibited 2.32 times higher relative activity compared to its free counterpart. However, after five reuse cycles, the immobilized lipase retained 40.30% of its initial activity. Furthermore, after being stored at 4 °C for 30 days, the relative activity of immobilized lipase was slightly higher than that of free lipase, approximately 24.32% and 14.81%, respectively. The adsorption kinetics and isotherm studies revealed that the adsorption process followed pseudo-first-order kinetic and the Temkin isotherm model. A maximum adsorption capacity of 87.82 mg/g was present in CR solution at 25 °C, pH = 6.0, 420 min, 50 mg dosage, and 100 mL of an initial concentration of 120 mg/L. Furthermore, the immobilized lipase exhibited excellent reusability, maintaining a CR removal efficiency above 70% after 5 consecutive cycles.