Supercritical extraction of toxic heavy metals from aqueous waste via Cyanex 301 as chelating agent

Extraction of toxic heavy metals such as uranium (U), hafnium (Hf) and zirconium (Zr) using supercritical carbon dioxide (SC-CO2) and Cyanex 301 (Bis(2,4,4-trimethylpentyl) dithiophosphinic acid) as chelating agent were carried out from a synthetic wastewater sample. The static (10–90 min) and dynamic extraction time (10–90 min), pressure (8–36 MPa) and temperature (40–100 °C) of supercritical fluid, as the main effective variables on extraction yield of toxic heavy metals were investigated. The response surface methodology was used for design of experiments. The optimal conditions were determined to be 78.2 °C, 25.54 MPa, 75 min (static) and 70 min (dynamic). The extraction yield of U, Hf and Zr at optimal conditions was predicted by response surface methodology (RSM) to be 98.1, 28.9 and 65.2%, respectively and was also validated experimentally with very close compatibility.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Supercritical extraction of toxic heavy metals “U, Hf and Zr” was modeled via RSM. ► Optimal conditions were determined to obtain maximum recovery. ► Yield of U, Hf and Zr at optimal conditions was predicted by RSM. ► RSM predictions were experimentally validated.