Dried cell of a new strain, known as Acinetobacter baylyi, showed appropriate biological removal of Cr (VI) under acidic condition. The adsorption parameters optimised were: biomass dose (2.0 g/L), initial pH (2.0), agitation speed (250 rpm), initial Cr (VI) concentration (10–60 mg/L), temperature (30 °C), and time (72 h). The experimental data in the 20–60 mg/L Cr(VI) concentration range fitted well to the Langmuir isotherm (R2 = 0.9545, maximum capacity 11.96 mg/g) and pseudosecond-order adsorption model. The adsorption mechanism was best described by the Boyd plot and an intraparticle diffusion model. TEM-EDX studies revealed that the noticeable chromium precipitates on bacterial surfaces and within the bacterial inner portions after Cr (VI) adsorption. An XPS study recommended that this bacterium use carbonyl/hydroxy/carboxy groups on the surface for adsorption of Cr (VI).
