Removal efficiency of Cu2+, Cd2+, Pb2+ by waste brewery biomass:: pH and cation association effects

In this work two distinct (flocculent and non-flocculent) yeast wastes from Portuguese breweries were used for the selective removal of Cu2+, Cd2+ and Pb2+ from aqueous solutions. One of the goals was to establish both the pH pro files for the removal of each metal ion (1.0 mM) and the effect on the biomass biosorption capacity of pH adjustment during the process. The effect of the presence of multiple metal ions, in the 0.1-1.0 mM range, on metal removal efficiency was also studied. The results showed that, in the absence of pH adjustment, the optimum initial pH for the removal of three cations was in the 4.5-5.5 range for both types of biomass. However, a gradual pH increase was observed during the removal process, up to a final equilibrium value of 7.0-8.0. Regarding the biomass efficiency for metal removal in multi-cation systems, it was verified that only Cu2+ was significantly affected by the presence of the other metals in solution and only when the non-flocculent yeast biomass was used as biosorbent. Cd2+ was only slightly affected by the presence of both Cu2+ and Pb2+, and Pb2+ removal was not affected by the presence of any or both of the interferent metals for the two biosorbents used in this work. The highest and lowest metal removal yields were obtained for Pb2+ and Cu2+, respectively.