斑铜矿在电化学溶解过程中表面钝化物的演变

Evolution of passivating species on bornite surface during electrochemical dissolution

在斑铜矿(生物)浸出过程中,中间产物的产生与氧化还原电位之间的关系尚不清楚。本文作者采用一系列电化学试验和表面分析方法研究天然斑铜矿的电化学溶解行为和表面硫物种的形成。电化学试验表明,在宽阳极电位下(300~800 mV(vs Ag/AgCl)),斑铜矿电极表面经历3种不同的变化,即“活化”(<400 mV(vs Ag/AgCl)),“钝化”(400~700 mV(vs Ag/AgCl))和“过钝化”(>700 mV(vs Ag/AgCl))。XPS结果表明,在斑铜矿电化学溶解过程中表面产生的含硫中间产物包括类铜蓝、S_(n)^(2−)/S_(0)和不溶性SO_(4)^(2-)。此外,原子力显微镜结果证实:当施加的电位分别为600和700 mV(vs Ag/AgCl)时,由于S_(n)^(2−)/S_(0)的积累,斑铜矿表面会受到严重钝化。斑铜矿(生物)浸出最有利的电位为400 mV(vs Ag/AgCl)。

During bornite(bio)leaching,the relationship between the production of intermediate products and redox potential is unknown.In this study,a series of electrochemical tests and surface analytical methods were adopted to investigate the electrochemical dissolution of natural bornite and the formation of the sulfur species on the bornite surface.Electrochemical tests demonstrated that the surface of bornite experienced three distinct variations over a broad anodic potential(300−800 mV(vs Ag/AgCl)):“activation”(<400 mV(vs Ag/AgCl)),“passivation”(400−700 mV(vs Ag/AgCl)),and“transpassivation”(>700 mV(vs Ag/AgCl)).XPS results indicated that covellite-like species,S_(n)^(2−)/S_(0),and insoluble SO_(4)^(2-)were considered as intermediate products during bornite electrochemical dissolution.Furthermore,AFM results proved that the accumulation of S_(n)^(2−)/S_(0)made bornite surface suffer severe passivation when applied potentials were 600 and 700 mV(vs Ag/AgCl),respectively.The most advantageous potential for bornite(bio)leaching was shown to be 400 mV(vs Ag/AgCl).