Dried and re-hydrated biomass of Spirulina platensis was employed as a sorbent in tests of copper removal from water. Biomass re-hydrated for 24 h before use exhibited a shorter adsorption time as well as an increased percentage removal when compared with simply dried biomass. The combined effects of the concentrations of re-hydrated biomass (from 1.0 to 4.0 g l(-1)) and copper (from 0.1 to 0.4 g l(-1)) were then investigated. Copper was almost entirely removed (91% removal) at relatively high biomass levels (X-0 >= 2.0 g(DM) l(-1)), while 1.0 g(DM) l(-1) removed only 81% of copper present initially, suggesting a situation of excess metal with respect to the adsorption capacity of biomass. Additional tests performed with biomass re-hydrated for variable time demonstrated that no less than 48 h of this treatment are needed to ensure a satisfactory copper removal, while no significant improvement was detected using biomass re-hydrated for longer times. (c) 2005 Elsevier Ltd. All rights reserved.