Abstract
Metal ions in liquid samples can be extracted by supercritical CO2, containing a suitable ligand. This paper presents the first experimental data for the extraction of three heavy metals Cu, Zn and Cd from aqueous samples in the presence of Dithizone as chelating agent. Extractions by supercritical CO2 have been performed at 120 bars with 50°C used dynamic technique. After adding the CO2 on the aqueous metal solution, the pressure and temperature 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 CO2 2 mL min-1. After the extraction, the CO2 was released 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 remaining aqueous solution in the extractor was analyzed for its metal content by Atomic Absorption Spectrophotometer (AAS), determining the recovery of the metal by CO2. During dynamic extraction noticed increased of extraction in function of time for 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).
Highlights
Chelating combined with solvent extraction is one of the most widely used techniques for preconcentration and separation of metal ions from aqueous samples for analytical purposes Chein (1991)
Authors Chein et al, (1993) during their research concluded that metal ions can be extracted with Supercritical Fluid Extraction (SFE) using CO2 in the presence of suitable ligands
They have reported the application of SFE for the extraction of Cu 2+, Cd2+, Zn2+ and Hg2+ in the presence of ligand lithium bis dithiocarbamate (LiFDDC)
Summary
Chelating combined with solvent extraction is one of the most widely used techniques for preconcentration and separation of metal ions from aqueous samples for analytical purposes Chein (1991). The technology of Supercritical Fluid Extraction (SFE), offers the opportunity to efficiently extract both relatively non-polar analytes as well as ionic materials (such as metal ions) that can be mobilized with the addition of complexing agents Kronholm (2007). The supercritical fluid extraction SFE method is becoming popular alternative technique for the extraction of a wide range organo-metallic and inorganic analytes Wang and Marshall (1995). The main objective of this research was to develop SC-CO2 extraction procedure for metal ions in liquid samples and to elucidate further the parameters linked to the SFE extraction process. The main goal was to optimize the extraction factors to give better results in qualitative and quantitative scope, without neglecting the use of statistical and instrumental analytical methods to achieve fast quantitative verification
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