Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation

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Cordeiro T.G.
Hidalgo P.
Gutz I.G.R.
Pedrotti J.J.
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A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH3CH2OCS 2 - at trace concentrations in pulp solutions from froth flotation process is proposed. The analytical method is based on the decomposition of ethyl xanthate, EtX-, with 2.0 mol L-1 HCl generating ethanol and carbon disulfide, CS2. A gas diffusion cell assures that only the volatile compounds diffuse through a PTFE membrane towards an acceptor stream of deionized water, thus avoiding the interferences of non-volatile compounds and suspended particles. The CS2 is selectively detected by UV absorbance at 206 nm (ε = 65,000 L mol -1 cm-1). The measured absorbance is directly proportional to EtX- concentration present in the sample solutions. The Beer's law is obeyed in a 1 × 10-6 to 2 × 10-4 mol L-1 concentration range of ethyl xanthate in the pulp with an excellent correlation coefficient (r = 0.999) and a detection limit of 3.1 × 10-7 mol L-1, corresponding to 38 μg L -1. At flow rates of 200 μL min-1 of the donor stream and 100 μL min-1 of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD < 2.3% (n = 10, 300 μL injections of 1 × 10-5 mol L-1 EtX-). Two practical applications demonstrate the versatility of the FIA method: (i) evaluation the free EtX- concentration during a laboratory study of the EtX- adsorption capacity on pulverized sulfide ore (pyrite) and (ii) monitoring of EtX- at different stages (from starting load to washing effluents) of a flotation pilot plant processing a Cu-Zn sulfide ore. © 2010 Elsevier B.V. All rights reserved.
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Correlation coefficient , Ethyl xanthate , Flotation process , Flow analysis , Froth flotation process , Gas diffusion , Robust analytical methods , Spectrophotometric determination
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