The effect of solvents on metal ion adsorption by the alga Chlorella vulgaris

The dead dried alga, Chlorella vulgaris, was used for metal ion sequestering. The uptake of each of Cu(II), Cd(II), Fe(III), and Sn(IV) from their aqueous solutions decreased upon reuse of the biomass. Introducing mixed ethanol/water (50% v/v) metal ion solutions in batch systems enhanced the metal uptake of the exhausted biomass by 90% for iron, 40% for tin and only 14% for cadmium. In the column system, 20% v/v ethanol/water proved to be superior to acetone/water and isopropanol/water metal solutions in enhancing metal uptake. This increase in uptake offers a new method for regeneration of the algal capacity to remove metal ions from their solutions. Mössbauer results of iron and tin loaded algae from aqueous and mixed ethanol water solutions exhibited the characteristic doublet for (FeCl4-) at 0.350-0.565 mm s−1 respectively and the major doublet for inorganic Sn(IV) moieties at −0.217 to −0.365 mm s−1 respectively, excluding the possibility of microprecipitation of iron and tin, which is expected at such high concentrations of metals in the alga.