BACKGROUNDCr(VI) is being increasingly used in a variety of fields, including electroplating, metallurgy, pigment synthesis and leather tanning. The possible application of a microbial extracellular polymeric substance (EPS) from Klebsiella sp. J1 with abundant functional groups in remediating Cr(VI) pollution in water system was demonstrated. RESULTSThe maximum biosorption capacity of EPS for Cr(VI) was found to be 53.3mgg(-1) at an EPS dose of 1.5gL(-1), which was better than the majority of reported biosorbents. The adsorption of EPS for Cr(VI) was a spontaneous and endothermic process. The removal mechanism of Cr(VI) in aquatic environments was explored qualitatively and quantitatively by Zeta-potential meter, X-ray photoelectron spectrometer (XPS) as well as Fourier transform infrared spectrometer. The superior Cr(VI) removal performance was attributed mainly to Cr(VI) adsorption on EPS via chelation and ion-exchange sorption, and the efficient reduction (82.3%) of Cr(VI) to Cr(III) by benzenoid amine (-NH-) on EPS, followed by generated Cr(III) immobilization on the surface of EPS via surface physical sorption and chelation, which might control the reaction rate of Cr(VI) removal process. CONCLUSIONThe removal of Cr(VI) by EPS from Klebsiella sp. J1 was attributed mainly to simultaneous sorption and reduction of Cr(VI) by EPS. The results demonstrated that EPS from Klebsiella sp. J1 has great potential in treating Cr(VI)-contaminated water. (c) 2018 Society of Chemical Industry