Monitoring and reuse: a way to generating smaller amounts of effluents in mineral flotation systems

IGNACIO PEDRE; GRACIELA A. GONZÁLEZ; LUCILA MÉNDEZ DE LEO; FERNANDO BATTAGLINI

Berlin

Conferencia; 2nd Green and sustainable Chemistry Conference; 2017

Introduction: Xanthates (R-O-CS2-K+) are organosulphur compounds used in the mineral treatment industry as collector agents for the flotation of sulphides. Over 2x109 tons of ores are processed by flotation each year worldwide, and 50 to 300 g of xanthate are required to treat one ton of ore (1,2).These compounds are unstable at pH < 6.5, the main decomposition products being carbon disulfide and the corresponding alcohol. Since xanthate and CS2 are highly toxic to the aquatic flora and fauna (3), from the environmental point of view it is important to measure its concentration in the flotation slurry, in the processed ore, and in wastewater (1,4,5). In this work, we used ethyl xanthate as a model system to develop sensors applicable to flotation baths where the concentration is usually between 10 and 100 µM (6), with the goal of reducing the impact of ore processing activities.Method: The sensor consisted in a disposable screen printed graphite electrode (Fig. 1) modified with a polymeric matrix (polyallylamine and dodecylsulfate). Fig. 1. Used disposable graphite screen printed electrodeThe determinations were carried out by exposing the disposable sensors to solutions with varying concentrations of xanthate, and after an oxidative treatment, electrochemical impedance measurements using ferrocyanide as a probe were made (Fig. 2).Results: The obtained spectra were fitted with a circuit similar to the Randles circuit. The obtained charge transfer resistance showed a linear relationship with the xanthate concentration even for solutions from mineral flotation baths. Fig. 2: EIS measurements: xanthate solutions in the concentration range of 0 to 100 µMIn order to clarify how the sensor works, attenuated total reflectance (ATR) measurements of the electrodes were made. It was found that during the oxidative treatment, xanthate dimerized to dixanthogen, thus making it more difficult for ferrocyanide to reach the electrode.Discussion: This sensor is economic and easy to use for untrained personnel and constitutes an important tool for the monitoring of flotation slurries and reducing the environmental impact of the ore processing industry.Bibliography:1. Hidalgo P, Gutz IG. Talanta 2001;54(2):403-92. McKetta JJ, editor. Unit operations handbook. New York: Marcel Dekker; 1993. 2 p3. Fontenele RS, Hidalgo P, Gutz IGR, Pedrotti JJ. Talanta 2007;72(3):1017-224. Crnogorac G, Schwack W. TrAC Trends Anal Chem. 2009;28(1):40-505. Kesari R. Talanta 1998;45(6):1097-1026. Ivaska A. Talanta 1986;33(10):801-6