Experimental investigation and optimization of supercritical carbon dioxide extraction of toxic heavy metals from solid waste using different modifiers and chelating agents

Supercritical carbon dioxide extraction of toxic heavy metals including Uranium (U), Hafnium (Hf), Zirconium (Zr) and Cadmium (Cd) from a synthetic solid waste matrix was carried out using Cyanex 302, Cyanex 301, Cyanex 272, EDTA and TOPO as chelating agents in conjugation with methanol, acetylacetone, MIBK, acetone and acetonitrile as modifier. The dynamic extraction time (10-90min), pressure (8-35 MPa), temperature (40-100 degrees C), type of modifier and chelating agent were investigated as the main effective variables on the extraction yield of toxic heavy metal ions. The quantities of toxic heavy metals in the original and extracted samples were determined by ICP analysis. The optimal conditions for the extraction of heavy metal ions were determined by one factor at a time method (OFAT) to be 80 degrees C, 26 MPa and 70 min (dynamic) using Cyanex 272 as chelating agent and methanol as modifier. The extraction yield of Zr, Hf, U and Cd at optimal conditions was predicted to be 100, 100, 99.1 and 100%, respectively. (C) 2016 Elsevier B.V. All rights reserved.