Abstract
Copper is toxic to living organisms and is listed as a major pollutant by the U.S. Environmental Protection Agency (EPA) and liquid-liquid extraction has shown great capabilities for its removal from aqueous extraction, particularly when adequate extracting agents and diluents are used.
The present work concerns chelate extraction of copper traces from aqueous solutions by means of Sodium Diethyldithiocarbamate (NaDDC) as the extractant. The effect of several parameters such as the mass of the extractant, the shaking time, the ratio of the organic phase volume to that of the aqueous one, the pH of the aqueous solution, on the copper extraction from synthesised solutions, was investigate.
The SDDT mass in presence of chloroform as the diluent was increased gradually from 1 to 12 mg, fixing the initial concentration of metal, the volumes of the aqueous and organic phases, the shaking time and the stirring velocity. The extraction ratio increased up to a value of 99.94 % as the SDDT mass increased up to 9 mg, before reaching a constant value.
The aqueous and organic phases should be well agitated, increasing the contact and homogenising the concentrations of the different species in order that the complexation reaction would not be limited by diffusion. This parameter was varied from 5 up to 120 min and for an extractant mass equal to 7 mg, the extraction percentages were not far from an average value of 90 %.
The volume ratio of the organic phase to that of the aqueous one was varied from 0.2 up to 4, keeping all the other parameters constant. The optimum value of the volume ratio was 1:1 corresponding to an extraction percentage of 92.45 %.
The pH of the aqueous solution before extraction was varied from 2 to 11 and the extraction percentage increased reaching a value 99.39 % for pH= 9. For a pH greater than 9, a decrease was observed.
The analysis of the organic phases obtained after separation by UV-visible spectrophotometer confirmed the formation of Cu(DDC)2 complex in Chloroform, assuming a dissociation as [(C2H5)2NCSS]- and Na+ in the aqueous phase.
