Flow injection analysis of ethyl xanthate by gas diffusion and UV detection as CS2 for process monitoring of sulfide ore flotation.
A sensitive and robust analytical method for spectrophotometric determination of ethyl xanthate, CH(3)CH(2)OCS(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, CS(2). 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 CS(2) is selectively detected by UV absorbance at 206 nm (epsilon=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 1x10(-6) to 2x10(-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 3.1x10(-7) mol L(-1), corresponding to 38 microg L(-1). At flow rates of 200 microL min(-1) of the donor stream and 100 microL min(-1) of the acceptor channel a sampling rate of 15 injections per hour could be achieved with RSD<2.3% (n=10, 300 microL injections of 1x10(-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.
Effects of salinity on xanthate adsorption on sphalerite and bubble–sphalerite interactions
Abstract The adsorption of amyl xanthate on sphalerite in NaCl solutions of different concentrations and in saline water (viz. simulated sea water) and the surface properties of treated minerals were investigated. The interactions between xanthate treated sphalerite particles and air bubbles were examined using induction time measurement, which revealed that the salt ions could inhibit the adsorption of xanthate on sphalerite due to the competitive adsorption, but also could compress the electrical double layer at mineral/water interface. The induction time of sphalerite treated in potassium amyl xanthate (PAX) with saline water was shorter than that of sphalerite treated in PAX with NaCl of the same ion concentration, which implies that the water composition (e.g. Ca 2+ , Mg 2+ ) could play an important role in the bubble–particle interaction. The hydrophobicity, chemical composition, and charge property of PAX treated sphalerite surfaces were characterized using contact angle measurement, Cryo-X-ray photoelectron spectroscopy (Cryo-XPS) and zeta potential determination, respectively, which support the inhibition effect of salt ions on the xanthate adsorption on sphalerite. In the case of saline water, the xanthate decomposition products were confirmed by XPS, which could further lower the hydrophobicity of the treated sphalerite. Our results provide insights into the basic understanding of the salinity effects on the xanthate adsorption on sphalerite and the bubble–mineral interactions in flotation.
Differential pulse polarographic determination of thiol flotation collectors and sulphide in waters.
Thiol collectors and sulphide can be determined together by differential pulse polarography. Ethyl xanthate, diethyl dithiophosphate, and diphenyl dithiophosphate have been determined in concentrations from 10 muM to 2 mM, and sulphide from 1 muM to 0.5 mM. The method is reliable and rapid; however, the exact behaviour of the thiol collectors must be known since the pattern of current peaks changes as the concentration increases. This method has been used in the study of sulphide mineral flotation and could be utilized at full-scale flotation plants.