Supercritical CO2 extraction of heavy metals Cu, Zn and Cd from aqueous solution using D ithizone as chelating agent

Abstract

Metalions in liquid samples can be extracted by supercritical CO2,containing a suitable ligand. This paper presents the first experimental datafor the extraction of three heavy metals Cu, Zn and Cd from aqueous samples inthe presence of Dithizone as chelating agent. Extractions by supercritical CO2have been performed at 120 bars with 50°C used dynamic technique. After addingthe CO2 on the aqueous metal solution, the pressure andtemperature were set and extraction was performed in three periodical times;30, 60 and 120 min at constant temperature and pressure with a flow rate of CO22 mL min-1. After the extraction, the CO2 wasreleased slowly through a restrictor. Methanol was used as a modifier (v/v) 10%and the pH value was set (10). After the extraction process, the remainingaqueous solution in the extractor was analyzed for its metal content by AtomicAbsorption Spectrophotometer (AAS), determining the recovery of the metal by CO2.During dynamic extraction noticed increased of extraction in function of timefor all three metals; Cu (61.12-73.52%, RSD = 2.694, n = 3); Zn (78.33-87.00%,RSD = 1.243, n = 3) and Cd (70.60-82.40%, RSD = 2.227, n = 3).