ECAFE
The study of the effect of organic complexing agents of Fe(III) or Fe(II) on iron monosulfide oxidative dissolution
PROJECT OBJECTIVES CONSORTIUM RESEARCH PUBLICATIONS


Scientific results


YEARS 2012 and 2013

Influence of 2,2'-bipyridine on oxidative dissolution of FeS

The aim of this study was to determine the effect of 2,2'-bipyridine (a Fe(II) ligand) on FeS oxidative dissolution. It was found that the corrosion current density decreases when the concentration of 2,2'-bipyridine increases from 0 up to 0.75 mM. Then, it slightly increases when the concentration of 2,2'-bipyridine becomes 1 mM. The study encloses the analysis of the reacted FeS surfaces by Raman spectroscopy and Scanning Electron Microscopy. Our conclusion is that the oxidative dissolution of FeS in the presence of 2,2'-bipyridine is the result of two processes with opposite effect: 1) the inhibiting adsorption of 2,2'-bipyridine on the FeS surface and 2) the promoting effect of 2,2'-bipyridine on the breakage of Fe-S bond


The effect of 1,10-phenanthroline on the oxidative dissolution of FeS

The effect of 1,10-phenanthroline (a Fe (II) ligand) on the oxidative dissolution of synthetic FeS was tested by using electrochemical methods. The experiments were performed in air-saturated HCl solutions with the concentration of 1,10-phenanthroline in range 0-1 mM, at pH 5 and 25oC. The corrosion current densities values are quasi-constant when the concentration of 1,10-phenanthroline varies between 0 and 0.5 mM. When the concentration of 10-phenanthroline exceeds the value of 0.5 mM, corrosion current density increases. The interaction between FeS and 1,10-phenanthroline was proved by FTIR spectroscopy. The morphology of reacted FeS surface was analyzed under Optical Microscope


Effect of inorganic anions on FeS oxidative dissolution

The oxidative dissolution of FeS range in the presence of inorganic anions (NO3- and Cl-) was investigated by electrochemical methods. In air-equilibrated aqueous solutions with pH between 5.5-6.0 the reaction rates increased with increasing [NO3-] and [Cl-], demonstrating the ionic nature of activated complex of FeS oxidative dissolution. The structure of FeS/water interface was characterized by Electrochemical Impedance Spectroscopy. The results indicate that the FeS reactivity may be significantly affected by a change in the composition of natural water, and imply that any dissolution model at the FeS surface should also take into account the specific impact of these anions


The inhibiting effect of new organic compounds on the oxidative dissolution of FeS

The inhibiting effect of some new organic compounds (potential ligands of iron) on the oxidative dissolution of FeS in air-saturated HCl solutions was investigated by electrochemical methods. The studied organic inhibitors were: 4-(5-bromo-2-hydroxyphenyl)-5-methyl-2-(morpholin-4-yl)-1,3-thiazol (Pr01); 4-(2-hydroxyphenyl)-2-(morpholin-4-yl)-1,3-thiazol (Pr02) and 1-(5-bromo-2-hydroxyphenyl)-1-oxaethan-2-yl-N,N-diethyldithiocarbamate (Pr03). The best inhibition efficiency was observed for Pr01 (54 %). The other inhibition efficiencies were: 13% (Pr02) and 31% (Pr03). The interaction between FeS and Pr01 was analyzed by Raman spectroscopy, and the surface of reacted FeS was inspected under Scanning Electron Microscope


Inhibition of FeS oxidative dissolution in air saturated acidic solutions by O-ethyl-S-2-(2-hydroxy-3,5-diiodophenyl)-2-oxoethylxantogenate (EHDO)

The effect of EHDO (a potential ligand of iron) on the oxidative dissolution of synthetic FeS was investigated. It was found that EHDO is an effective inhibitor of oxidative dissolution of FeS in air saturated HCl solutions. Inhibition efficiency increased when the concentration of EHDO in the solutions used for pretreatment increased from 0 (0%) up to 0.5 mM (81%). Then, it slightly decreased to 69% when the concentration of EHDO becomes 1 mM. The pretreated FeS samples were investigated by Raman spectroscopy and Scanning Electron Microscopy


The effect of other organic compounds on the oxidative dissolution of FeS

The effect of ethylenediaminetetraacetate (a Fe(III) ligand) on FeS oxidative dissolution in air saturated solutions, 2-(3,5-Dibromo-2-hydroxyphenyl)-2-oxoethyl-N,N-diethyldithiocarbamate, 2-(2-Hydroxy-3,5-diiodophenyl)-2-oxoethyl-N,N-diethyldithiocarbamate and 2-(5-Bromo-2-hydroxy-3-methylphenyl)-2-oxoethyl-O-ethylxantogenate on FeS oxidative dissolution in air saturated acidic solutions was investigated. The obtained data suggest a minor effect of these organic compounds on the FeS dissolution


Pyrrhotite oxidative dissolution

The kinetics of pyrrhotite (nonstoichiometric FeS) oxidative dissolution was investigated in the absence of organic compounds. The obtained results are used as a benchmark for understanding FeS dissolution in the presence of organic compounds.



YEAR 2014

The effect of 1,10-phenanthroline and EDTA on the oxidative dissolution of FeS

The experimental data obtained during the oxidative dissolution of synthetic FeS in the presence of 1,10-phenanthroline (a Fe (II) ligand) at pH between 2.5 and 5 and 25 oC were analyzed and a theoretical model of mineral oxidation was proposed. The corresponding paper was submitted to publication. Also the results of the experiments of FeS oxidative dissolution in the presence of 0.1-1 mM EDTA (a ligand of both Fe(II) and Fe(III)) at pH 2.5 and 25 oC were analyzed and presented to a conference.

It is important to note that several papers which report the results of the Partner 1 (the synthesis of the organic compounds used in the experiments carried out by Coordinator and Partner 2) were published in 2014. Also, a serie of the experimental results obtained during previous year (2013) were presented to Goldschmidt Conference 2014 and GES-10.


The effect of newly synthesized organic compounds (ligands or potential ligands of Fe(II)) on the oxidative dissolution of PbS, ZnS and CuFeS2

The effect of 4-Fenil-2-N-morfolinil-tiazol (Pr02); N,N-dietilditiocarbamat de 1-(3,5-dibromo-2-hidroxifenil)-1-oxoetan-2-il (Pr04) and O-Etilxantogenat de 1-(5-bromo-2-hidroxi-3-metilfenil)-1-oxoetan-2-il (Pr06) on the oxidative dissolution of PbS, ZnS and CuFeS2 (mineral sulfides with similar reactivity with FeS) in aerated HCl solutions at pH 2.5 and temperatures between 25 and 30 oC was investigated by electrochemical techniques (Potentiodynamic Polarization, Cyclic Voltammetry and Electrochemical Impedance Spectroscopy), aqueous batch experiments, SEM/EDX analysis, FTIR and Raman spectroscopy. The results indicate that the rate of the oxidative dissolution of PbS, ZnS and CuFeS2 is strongly influenced by the pretreatment of mineral sulfide and temperature.

Details about the results obtained in 2014 can be found in:

» Technical Report 2014



YEAR 2015

The effect of ligands or potential ligands of ferric iron on the oxidative dissolution of PbS and CuFeS2

Details about the results obtained in 2015 can be found in:

» Technical Report 2015



YEAR 2016

The behaviour of the PbS, ZnS or CuFeS2 in the presence of ligands or potential ligands of Pb, Zn or Cu

Details about the results obtained in 2016 can be found in:

» Technical Report 2016



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