Probing the hydrophobic mechanism of N-[(3-hydroxyamino)-propoxy]-N-octyl dithiocarbamate toward bastnaesite flotation by in situ AFM, FTIR and XPS

The hydrophobic mechanism of N-[(3-hydroxyamino)-propoxy]-N-octyl dithiocarbamate (OAHD) toward bastnaesite flotation. [Display omitted] •N-[(3-hydroxyamino)-propoxy]-N-octyl dithiocarbamate collector was designed.•Both dithiocarbamate and hydroxamate groups had weak affinity to Ca2+ ions.•In situ AFM clearly observed that OAHD aggregated on bastnaesite surface.•OAHD’s dithiocarbamate and hydroxamate groups co-anchored on bastnaesite.•OAHD returned a selective flotation separation of bastnaesite from calcite. Both hydroxamate and dithiocarbamate groups exhibit a unique bonding characteristic toward rare earth ions. A hydroxamic acid surfactant containing a dithiocarbamate group should possess a specific affinity to hydrophobize bastnaesite [(Ce, La)CO3F] flotation. N-[(3-hydroxyamino)-propoxy]-N-octyl dithiocarbamate (OAHD) was synthesized, and its flotation mechanism toward bastnaesite was investigated by in situ AFM, FTIR, XPS, micro-flotation and contact angle. In situ AFM clearly observed that OAHD aggregated on bastnaesite surface, which improved the contact angle and surface hydrophobicity of bastnaesite. FTIR spectra and XPS recommended that OAHD’s dithiocarbamate and hydroxamate groups co-anchored on bastnaesite surface through strong chemisorption, which strengthened the bonding affinity of bastnaesite toward OAHD. UV spectra showed that both dithiocarbamate and hydroxamate groups exhibited weak affinity toward Ca2+ ions, which benefited OAHD’s selective flotation separation of bastnaesite from calcite. The co-adsorption and special hydrophobic structure improved OAHD’s flotation performance. As a result, OAHD returned higher flotation selectivity for bastnaesite than OHA (n-octyl hydroxamic acid) which chemisorbed on bastnaesite surface only through the hydroxamate group and used the heptyl as hydrophobic group.