Fly ashes from two fluidised bed power plants were tested to remove Pb2+, CU2+, Cr(III), Ni2+, Zn2+ and Cr(VI) from aqueous solutions. Experimental design methodology was used to study the removal and the leaching as a function of (i) the water pollutant content, (ii) the metal concentration in water, (iii) the pH of the solution and (iv) the addition of lime to fly ashes. The results show that the percentage of adsorbed ions was greater when they were in contact with silico-aluminous fly ashes than sulfo-calcic fly ashes, except in the case of the ion Ni2+. The removal of metallic ions increases with increasing pH. A comparison of the adsorption capacity with similar tests carried out with activated carbon or low-cost sorbents shows that adsorption onto fly ash is an interesting alternative.