GF-AAS Determination of Trace Amount of Copper in Copper Tailings with Microwave Assisted Sample Digestion and Separation by Cloud Point Extraction

Sample of copper tailings was digested with a mixture of HCl-HNO3 (3+1) and H2O2 in a microwave digestor. An aliquot was taken from the solution obtained and 1-(2-pyridineazo)-2-naphthol (PAN), Triton X-100, NaOH-KH2PO4 buffer solution of pH 3.0 as well as NaCl saturated solution were added. After diluting to 15 mL with water, the solution was heated at 70 ℃ for 30 min, to have the Cu2+ separated in form of its complex with PAN by the cloud point extraction. After discarding the water phase, the Triton X-100 phase was taken up with water and 3 drops of HCl. The content of copper in this solution was determined by GF-AAS. Linear relationship between values of absorbance and mass concentration of Cu2+ was kept in the range of 0.5-20 μg·L-1, with detection limit (3σ) of 0.36 μg·L-1. The proposed method was applied to the analysis of a sample of copper tailings, and recovery was tested by standard addition method giving values of recovery and RSD′s (n=6) in the ranges of 101%-105% and 3.0%-3.8% respectively.