Electrochemical study of the pyrite-oxygen-xanthate system

Considering the effect of pulp chemistry during flotation on froth stability

“…Improved valuable mineral grades achieved over and above those obtained from Test 13 were observed for Test 21 (1 IS, pH 9, DO 0 and 50 mV) for all valuable minerals determined with the difference between the two tests being the decrease in DO from 8 ppm to 0 ppm in Test 21. This may have been due to a lack of dixanthogen adsorption when little to no oxygen was present in the system (Usul and Tolun, 1974) and could mean that composite particles containing valuable and gangue minerals may have been lost to the tails. Flotation under nitrogen has been found to reduce the pulp potential to a less anodic potential, thereby requiring a higher pulp potential for xanthate interaction, and increasing the selectivity of certain minerals.…”

On the cathodic reaction coupled with the oxidation of xanthates at the pyrite/aqueous solution interface

“…Rest potential (Majima and Takeda, 1968;Allison et al, 1972;Usul and Tolun, 1974), electrokinetic (Fuerstenau et al, 1968(Fuerstenau et al, , 1990 and cyclic voltametry (Janetski et al, 1977;Woods, 1988) studies have corroborated the formation of dixanthogen on pyrite. Flotation recovery-potential curves for the pyrite-ethyl xanthate system at pH 8 (Trahar, 1984) and pH 9.2 (Richardson, 1995) indicate that the onset of flotation corresponds to the reversible potential for the xanthate/ dixanthogen couple.…”

“…Majima and Takeda (1968) have indicated that pyrite acts as a catalyst allowing the one redox pair O 2 (ad)/OH À (aq) to equilibrate with the other given by X À (ad)/X 2 (aq). Usul and Tolun (1974) based on polarogram studies on pyrite concluded that the presence of air or oxygen caused electrochemical conditions creating a catalytic surface suitable for the oxidation of xanthate ions to dixanthogen directly on the surface of pyrite. Ball and Rickard (1976) in their review on the chemistry of pyrite flotation and depression stated that when oxygen is present xanthate ions adsorb on pyrite through oxidation to dixanthogen coupled with the reduction of adsorbed oxygen.…”

Electrochemistry aspects of pyrite in the presence of potassium amyl xanthate and a lignosulfonate-based biopolymer depressant

“…Pyrite responds strongly with xanthates (X À ) in acidic to neutral pH conditions and it is generally acknowledged that dixanthogen (X 2 , oxidation product of xanthate ions) is the main product responsible for pyrite flotation [3,8]. The formation of dixanthogen is an electrochemical process involving charge transfer between pyrite and xanthate accompanied by the reduction of ferric hydroxides species on pyrite surface formed by surface oxidation [8][9][10]. Due to the semi-conductive nature of pyrite, electrochemical techniques have been widely applied in studying pyrite oxidation [7] and the fundamental interaction of xanthate with pyrite [9].…”

“…The formation of dixanthogen is an electrochemical process involving charge transfer between pyrite and xanthate accompanied by the reduction of ferric hydroxides species on pyrite surface formed by surface oxidation [8][9][10]. Due to the semi-conductive nature of pyrite, electrochemical techniques have been widely applied in studying pyrite oxidation [7] and the fundamental interaction of xanthate with pyrite [9]. The previous studies have showed that dixanthogen is only formed on pyrite when the mineral surface reaches a potential higher than the X À /X 2 equilibrium value [11].…”