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 (Qm) 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 (ΔGθ, ΔHθ and ΔSθ). 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.