The effective removal of Congo Red using a bio-nanocluster: Fe₃O₄ nanoclusters modified bacteria

A bio-nanocluster (Fe₃O₄@bacteria) was prepared by simply mixture using the bacterial suspension and Fe₃O₄ nanoclusters to remove Congo red (CR) contamination from water resources. The bio-nanocluster was characterized by SEM, TEM and XPS. Adsorption efficiency, adsorption process and adsorption mechanism were comprehensively investigated. The maximum adsorption capacity (Q_m) of CR dye onto the Fe₃O₄@bacteria peaked at 320.1 mg/g, which was 2.88 times that of Fe₃O₄ under the same condition. Based on the equilibrium and kinetic studies, the Langmuir isotherm theory and pseudo-first-order model is appropriate to describe the adsorption process. The adsorption of CR is spontaneous and exothermic according to the thermodynamics parameters (ΔG^θ, ΔH^θ and ΔS^θ). The adsorption force dominated the Van der Waals force, biofloculation and chemisorption. The Fe₃O₄@bacteria could be applied potentially as an absorbent with high efficiency and environmentally friendly remediation of dyeing wastewater.