A novel process has been developed for the direct extraction of heavy metal ions from their oxides using ligand assisted supercritical carbon dioxide (SC CO2) without and with a cosolvent. A systematic investigation has been carried out to ascertain the mechanism of direct in situ supercritical fluid extraction, which involves three essential steps, namely ionisation, complexation and extraction. The present work involves direct extraction of metal ions from their oxides using neodymium (Nd) as candidate metal utilizing a synergy of thenoyl tri fluoroacetone (TTA) and tri butyl phosphate (TBP). The mechanism has been established by analysing the conversion of neodymium oxide to Nd-3 and metal complex. By the reaction with carbonic acid, the metal oxide is converted into metal cation. SC CO2 facilitates tautomerisation and dissolution of TTA required for the chelation. Addition of methanol to SC CO2 enhances the formation of metal complex which is being extracted in the SC fluid phase. Effects of process parameters have been evaluated on the performance of the process to ascertain the optimum conditions. (C) 2008 Elsevier B.V. All rights reserved.