The adsorption of Cu2+ and Zn2+ by extracellular polymeric substances (EPS) extracted from Klebsiella sp. J1 and competitive adsorption mechanism were investigated. Equilibrium adsorption capacities of Cu2+ (1.77 mM g (1)) on Klebsiella sp. J1 EPS were higher than those of Zn2+ (1.36 mM g (1)) in single systems. The competitive Langmuir and Langmuir-Freundlich isotherm models were proven to be effective in describing the experimental data of binary component system. The three dimensional sorption surfaces of binary component system demonstrated that the presence of Cu2+ more significantly decreased the sorption of Zn2+, but the sorption of Cu2+ was not disturbed by the presence of Zn2+. FTIR and EEM results revealed the adsorption sites of Cu2+ entirely overlapped with those of Zn2+. Cu2+ and Zn2+ showed competitive adsorption in binary systems, and Cu2+ was preferentially adsorbed because of the stronger complexation ability of the protein-like substances in Klebsiella sp. J1 EPS. (C) 2015 Elsevier Ltd. All rights reserved.