The galvanic interaction between two minerals leads to redox reactions that change the surface of minerals, affecting their floatabilities. In the present work, the galvanic interaction between pyrite and arsenopyrite was studied through measurements of electrode potentials with and without electrical contact allied to contact angle determinations. The influence of nitrogen gas on those measurements was also investigated. When in contact with arsenopyrite, the contact angle of pyrite was almost twice the value without electrical contact between these sulfides, indicating that the interaction inhibited pyrite oxidation and caused an increase in contact angle. In the case of arsenopyrite, galvanic interaction caused a decrease of about 50 % in contact angle from that without interaction. This is explained by surface oxidation with the formation of FeOOH. Nitrogen bubbling leads to higher contact angles and lower potential values for both minerals with and without interaction between each other.
IntroductionSulfide minerals are an important source for metals extraction. The semiconductive characteristics of these minerals allows the study of their surface properties from the electrochemical point of view focusing oxidation, reduction and adsorption reactions that play an important role on both flotation and leaching process (1, 2, 3). Pyrite is the most abundant of the sulfide minerals, being economically negligible, unless it is associated with gold and other valuable metals. As sulfides normally occur in nature in a polymetallic form, a galvanic interaction must take place when two or more sulfide minerals are together into an aqueous solution.The galvanic interaction between two sulfide minerals is caused by their different electrochemical reactivity. When sulfide minerals in aqueous solution are in contact to each other, or even in contact with the metallic grinding environment, a galvanic cell is formed leading to redox reactions which strongly affects their surface properties. The electrochemical reactivity can be indicated by the rest potential of the sulfide mineral. Then, in a galvanic cell, the mineral with the higher rest potential is the more noble and the mineral with lower rest potential is the more active, being more susceptible to oxidation and behaving as an anode in the cell. The galvanic current which flows ECS Transactions, 2 (3) 35-45 (2006) 10.1149/1.2195996, copyright The Electrochemical Society 35 ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 142.103.171.55 Downloaded on 2015-06-29 to IP 36between these minerals is associated with surface modifications which affect their floatability. Furthermore, the presence of dissolved oxygen in the aqueous solution also affects the galvanic interaction, since it acts as an electron receptor, reacting to form OHions on the surface of nobler minerals. Galvanic interaction models can be established for binary systems, however, for a multiple component system the interaction bec...