Kinetics and roles of solution and surface species of chalcopyrite dissolution at 650 mV

Abstract

To better understand chalcopyrite dissolution in hydrogeochemical processes and the related environmental issue of acid and metalliferous drainage (AMD), the kinetics as well as the influence of solution composition and the nature of surface species formed during chalcopyrite dissolution have been examined under the controlled conditions of E h 650 mV (SHE), pH 1.0-2.0 and 75°C, with/without 4 mM Fe 2+ addition. SEM and XPS analyses indicate that the surface products, both at micro-and nano-scales, did not passivate dissolution under the conditions examined. Extensive S 0 was formed mostly as discrete particles rather than coatings on the chalcopyrite surface. Jarosite was only observed for dissolution at pH 2.0 with 4 mM added Fe 2+ . Without Fe 2+ addition, the initial dissolution rate was observed to be only correlated to H + activity as a 0:12ðAE0:01Þ H þ , indicating chalcopyrite dissolution was controlled via chemical oxidation of chalcopyrite by H + /O 2 . When reaction between chalcopyrite and Fe 3+ predominated chalcopyrite dissolution (i.e. later stage of dissolution without Fe 2+ addition), the dissolution rate was found to be positively correlated to the activities of Fe 3+ , as a 1:54ðAE0:07Þ Fe 3þ, and H + , as a 0:13ðAE0:05Þ H þ . When 4 mM Fe 2+ was added, no clear correlation was observed between the dissolution rate and the activities of either Fe 3+ or H + . It is proposed that the relative reactive surface area may not be proportional to that predicted by a shrinking sphere model as was assumed for derivation of the rate laws for the systems without added Fe 2+ , with the predicted rate being greater than the measured rate. Irrespective, it is clear that the addition of a relatively low Fe 2+ concentration plays an important role in accelerating the copper dissolution rate at this E h .

The Influencing Mechanisms of Sodium Hexametaphosphate on Chalcopyrite Flotation in the Presence of MgCl2 and CaCl2

“…The presence of a small portion of SO 4 2− indicated that chalcopyrite surface was weekly oxidized by air during grinding or drying process. However, it was reduced to 2 % S and 3 % S when chalcopyrite was treated in 0.01 M CaCl 2 and 0.05 M MgCl 2 solutions, respectively, due possibly to the dissolution of sulfate from chalcopyrite surface into solution [48]. In addition, further decrease was observed when 10 mg/L SHMP was added, indicating that the addition of SHMP was beneficial to SO 4 2− dissolution.…”

“…In other words, SHMP reduced the formation and adsorption of Mg(OH) 2 on chalcopyrite, thereby improving chalcopyrite recovery. Figure 10 shows five S species including monosulfide (S 2− ), disulfide (S 2 2− ), polysulfide (S n 2− ), sulfate (SO 4 2− ) and an energy loss feature (S 3p → Fe 3d) located at 161.3 eV, 162.0 eV, 162.8 eV, 169.1eV and 164.9 eV, respectively [38,[46][47][48][49].…”

“…Noted: All BE with a typical variation of ± 0.1 eV. [38,46,48,50,51]. It should be noted that the hydroxide and sulfate were fitted at 531.3 ± 0.1 eV due to overlapping of the binding energy of these two O species [52].…”

Chalcopyrite Dissolution at 650 mV and 750 mV in the Presence of Pyrite

“…Further study has shown that the chacopyrite dissolution rate at 650 mV is increased in the presence of added soluble iron [20]. However, the effect of pyrite at these two Eh conditions (i.e., 650 and 750 mV SHE) is not yet well understood.…”

The Influence of Impurity Monovalent Cations Adsorption on Reconstructed Chalcopyrite (001)-S Surface in Leaching Process

“…As some previous research works regarding chalcopyrite leaching were conducted in a sulfuric acid system [19,29,30], the adsorption sites of the SO4 2− and cations would play a role in chalcopyrite dissolution.…”