International Journal of Coal Science & Technology - Non-isothermal oxidation of brown coal with 5 wt% of Cu(NO3)2, 5 wt% of Ce(NO3)3 and {2.5 wt%... 相似文献
Over the last decade, AMD waters have gained more attention as a potential source of metals due to the emerging need to recover or recycle metals from secondary resources. Metals recovery supports sustainability and the development of a circular economy with benefits for resource conservation and the environment. In this study, five extractants (Acorga M5640, LIX 54, LIX 622, LIX 622 N, and LIX 864) diluted (15% (v/v)) in Shell GTL with 2.5% (v/v) octanol were compared and evaluated for Cu recovery from an extreme AMD sample (5.3?±?0.3 g/L Cu) collected at the inactive São Domingos Mine in the Iberian Pyrite Belt of Portugal. Of the five extractants, Acorga M5640 showed the best selective efficiency. Further tests showed that 30% (v/v) of this extractant was able to selectively extract ≈ 96.0% of the Cu from the AMD in one extraction step and all of the remaining Cu (to below detection) in three steps. Among the different stripping agents tested, 2 M sulfuric acid was the most efficient, with ≈ 99% of the Cu stripped, and the recyclability of the organic phase was confirmed in five successive cycles of extraction and stripping. Furthermore, contact time tests revealed that the extraction kinetics allows the transfer of ≈ 97% of the Cu in 15 min, and aqueous to organic phase ratios tests demonstrated a maximum loading capacity of ≈ 16 g/L Cu in the organic phase. Raising the concentration of Cu in the stripping solution (2 M sulfuric acid) to ≈ 46 g/L through successive striping steps showed the potential to recover elemental Cu using traditional electrowinning. Finally, a biological approach for Cu recovery from the stripping solution was evaluated by adding the supernatant of a sulfate-reducing bacteria culture to make different molar ratios of biogenic sulfide to copper; ratios over 1.75 resulted in precipitation of more than 95% of the Cu as covellite nanoparticles.
The Inco Bessemer Matte Processing Plant (IBMPP) suffers a loss of chalcocite selectivity in flotation separation from heazlewoodite down the rougher bank. Energy dispersive X-ray spectroscopy (EDX) analyses of the feed, concentrate and tail samples reveal a decrease in Cu and corresponding increase in Ni recovery through the primary rougher banks; tail samples can contain on the order of 7% Cu. The aim of this work was to examine any loss of selectivity through the primary flotation stream due to surface chemistry. Mechanisms suggested have included inadvertent activation and depression by the dissolution and solution transfer of Cu and Ni ions, lack of collector selectivity and possible requirement for reaction of the chalcocite surface prior to collector adsorption. The combination of information from SEM/EDX, X-ray photoelectron spectroscopy (XPS) analysis and XPS imaging has clarified the following aspects of the surface chemical mechanisms and control factors in the rougher flotation separation: (1) chalcocite in the feed to the rougher circuit appears to be unoxidized, i.e., all Cu(I) surface species, whereas the surfaces of the heazlewoodite appear to be entirely oxidized to hydroxide species; (2) chalcocite in the tails from the rougher circuit appears to be more oxidized with evident precipitates corresponding to Cu(OH)2 in both composition and morphology adhering to their surfaces; (3) the primary adsorption of diphenylguanidine (DPG) appears to be to Cu(I) sites on the unoxidized chalcocite surface; (4) adsorption of the DPG collector to chalcocite surfaces appears to be inhibited by the formation or concentration of fine Cu(II) hydroxide precipitates in the later rougher cells; (5) the crystalline morphology of some of the discrete, attached Cu(II) hydroxide precipitates may suggest formation in recycle water streams rather than by surface oxidation of the chalcocite through the circuit although this may not be the only form of Cu(II) hydroxide on chalcocite surfaces in cells C and D; (6) heazlewoodite flotation appears to be associated with the attachment or locking of fine unoxidized chalcocite rather than any direct adsorption of DPG; heazlewoodite fines are also found attached or locked to some chalcocite particles in concentrates contributing to loss of grade (i.e., heazlewoodite is not completely liberated); (7) heazlewoodite particles in tails have relatively high surface concentrations of attached more-oxidized chalcocite fines contributing to loss of recovery. 相似文献