Efficient removal of Cr(VI) ions by Staphylococcus aureus CC1956: biosorption isotherm and kinetic modeling

Chromium in its hexavalent form (Cr(VI)) is a highly toxic environmental pollutant that poses severe risks to human health and ecosystems. Staphylococcus aureus can play a role in the removal of Cr(VI) from aqueous solutions, primarily through a process of reduction and subsequent biosorption. While it's not as widely studied for this purpose as some other bacterial species, it has been shown to reduce and bind Cr(VI), potentially offering a way to remediate contaminated environments. This study assessed the biosorption potential of the bacterial strain Staphylococcus aureus CC1956, which tolerates Cr(VI) levels up to 700 mg/L. The strain demonstrated significant Cr(VI) removal across various conditions, including pH values from 5.0 to 9.0, temperatures ranging from 25 to 45 °C, and initial Cr(VI) concentrations between 50 and 300 mg/L. Competing anions exerted minimal influence on biosorption efficiency, whereas adding glucose significantly enhanced Cr(VI) removal. The adsorption data were best described by the Langmuir isotherm model, indicating a monolayer binding of Cr(VI) onto the bacterial surface. The main functional groups involved in the biosorption process revealed by FTIR analysis are hydroxyl, phosphoryl, carboxyl, and amine groups in the binding of Cr(VI). SEM-EDX analysis also confirmed the association of chromium with the cell surface. These findings highlight the potential of S. aureus CC1956 as an effective biosorbent for Cr(VI) and its promising application in the bioremediation of contaminated wastewater.