Determination of Cd2+, Cu2+, Mn2+, Pb2+, and Zn2+ in Aqueous Solution after Their Separation and Preconcentation as Metal - Dithizone Complexes on Activated Carbon

Abstract

A simple and sensitive method for preconcentration and determination of Cd2+, Cu2+, Mn2+, Pb2+ and Zn2+ by flame atomic absorption spectrophotometer was developed. The method is based on the sorption of the studied elements as metal-dithizone complexes (M-DZ) on activated carbon (AC). The effect of various parameters (pH, shaking time, AC amount, ligand concentrations, eluent concentration, and solution volume) on quantitative sorption of metal-dithizone chelates using AC was investigated. The studied elements were eluted from AC simply with HNO3 acid. The results revealed that the optimum pH values for the sorption were 4 for Cu2+, 6 for Zn2+, 8 for Pb2+ and 10 for Cd2+ and Mn2+; shaking time was 10 min for Mn2+ and Pb2+, 30 min for Cu2+ and Zn2+ and 50 min for Cd2+; AC amount was 0.2 g for Zn2+, 0.3 g for Cd2+, 0.5 g for Pb2+, 0.6 g for Mn2+ and 0.8 g for Cu2+; metal: ligand ratio was found to be (1:2 ratio), and eluent concentration used was 1 mol L-1 for Cd2+ and Mn2+, 2 mol L-1 for Zn2+ and 4 mol L-1 for Cu2+ and Pb2+. The method can be applied with a preconcentration factor of 20 for Cd2+, and 40 for Cu2+, Mn2+, Pb2+, and Zn2+. Preconcentration from various water samples showed recovery in the range 95-108 %, confirming the effectiveness and precision of the solid-phase method developed using activated carbon for enrichment of metals examined.