Carbon nanotubes (CNTs) had meaningful adsorption capacities for Pb2+, Cu2+, Zn2+ and Cd2+, while Pb2+ showed the highest adsorption in the competitive adsorption evaluations. The desorption behaviors of heavy metal ions were completely different in various biofluids, where the desorption was significantly influenced by pH and the presence of proteins/other cations. The desorption was most effective in simulated stomach juice, and much less effective in other simulated biofluids. More Pb2+ stuck to CNTs than others, resulting in less desorption. Interestingly, the competitive desorption behaviors of four ions were largely changed comparing to the individual desorption behaviors. The implications to the biosafety evaluations and synergistic effects of CNT are discussed. (C) 2015 Elsevier Inc. All rights reserved.