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Solvent Extraction of Copper(II) as a Thiocyanate Complex

Extraction of copper(II) from sulphuric and hydrochloric acid solutions containing an excess of thiocyanate ions with tetraphenylphosphorium (TPP) chloride and cetyltrimethylammonium (CTMA) bromide in chloroform was investigated. The effect of acidity, anion concentration of the mineral acid used, and of the thiocyanate and extractant concentrations on the extraction behaviour was examined. The copper(II) thiocyanate complex from pH 5.5 to 3M H2SO4 or 0.5 M HCl by both extractants. At higher acidity extraction very slowly decreased. For complete extraction of the copper(II) thiocyanate complex with TPP in chlorophorm the minimum molar ratio of thiocyanate to copper was 300:1 and of TPP to copper 27:1. For the complete extraction of the copper(II) thiocyanate complex with CTMA a low excess of thiocyanate and extractant was required. The optimium molar ratio of thiocyanate to copper was 200:1 and of CTMA to copper 17:1. At optimium acidity copper extraction was independent of chloride and sulfate ion concentrations in the aqueous phase. The copper(II) extracted as the thiocyanate complex with TPP or CTMA could be quantitatively stripped with M ammonium hydroxide. The extraction described can also be used for the spectrophotometric determination of copper(II) in the organic phase.The extracted complex with CTMA in chloroform had a maximum absorbance at 420 nm and obeyed Beer˘s law in the range of 3.50 ppm of copper. The molar absorptivity of the method was 2.4 x 103 dm3 mol-4 cm-1. The composition of the extracted copper(II) complex was determined by distribution (slope analysis) and spectrophotometric (continuous variation) methods.The molar ratio Cu:NCS:TPP (CTMA) of the extracted complex was 1:4:2.This indicates that the composition of the extracted complex was [R4X]2 [Cu(NCS)4] ([R4X]1= TPP or CTMA).

Solvent Extraction ; Copper(II)

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