Leaching of rare-earth elements and their adsorption by using blue-green algae

Abstract

In the present study, REEs were leached from a Vietnamese ore, by using (NH4)2SO4 and REEs were adsorbed from this leachate by blue- green algae (phormidium). In addition, the biosorption characteristics of phormidium for the adsorption of Nd has been studied. When the concentration of ammonium sulfide was 1%, leaching time was 3h, and S/L ratio was 0.09, the leaching ratio of Nd was 67.3%. In the adsorption process, when dosage of phormidium was 0.2 kg/L, the contact time was 30 min, and the temperature was 298 K, while pH was kept at the initial value (i.e. pH 5.6), the adsorption density of Nd was 182 mg/kg. These results were similar with the adsorption density of other absorbents, such as: activated carbon, Fe-based absorbent, and calcinated dolomite. Moreover, the equilibrium sorption isotherm of Nd onto phormidium was described by the Langmuir isotherm equation and the pseudo-second-order kinetic model fits the experimental data well. © 2011 The Japan Institute of Metals.