Selectivity of 2-mercaptobenzimidazole derivatives on metal ions studied by UV–vis spectromentry and DFT calculations

• Selectivity of MBI derivatives towards Ag+ as compared with the other metal ions was determined by UV–vis spectrum.
• The binding stoichiometry and constants of MBI derivatives with Ag+ was found by Job-plot and B-H methods.
• The binding energies of MBI derivatives with Ag+ were calculated by DFT method.
• BMBI was confirmed as a highly selective and efficient collector which can enhance the recovery of silver associated in lead–zinc sulfide minerals.

UV–vis absorption spectrometry and DFT calculations were used to study the selective binding of 2-mercaptobenzimidazole derivatives (MBI, EMBI, PMBI and BMBI) as chelating collectors with metal ions, including Fe3+, Cu2+, Pb2+, Zn2+ and Ag+. The results showed superior selectivity of these collectors towards Ag+ as compared with the other metal ions. The binding stoichiometry of MBI derivatives with Ag+ was found by Job-plot method to be 1:1. The binding constant determined using Benesi–Hildebrand (B-H) method showed the following order of BMBI-Ag > PMBI-Ag > EMBI-Ag > MBI-Ag. The binding energies of MBI derivatives with Ag+ calculated by DFT method followed the same order as the binding constant calculated by B-H method. All the calculation results were in good agreement with the results of UV–vis experiments which showed the highest selectivity and binding energies of BMBI towards Ag+. This study clearly shows that the BMBI is a good sensor for Ag+ ion. Therefore, the BMBI could be a highly selective and efficient collector to enhance the recovery of silver from silver-rich lead–zinc sulfide minerals.

Changes in UV–vis spectrum with addition of different amounts (0–9 equiv.) of Ag+ in CH3OH/H2O (4:1, v/v)-collector solutions.Figure optionsDownload as PowerPoint slide