β-Amino-hydroxamate surfactants: Preparation, and adsorption mechanism in bastnaesite flotation

beta-Amino-hydroxamate surfactants including N-(3-(dodecylamino)) hydroxamic acid (DAHA), N-(3-(octylamino)) hydroxamic acid (OAHA) and N-(3-(hexylamino)) hydroxamic acid (HAHA) were synthesized and firstly used as flotation collectors in bastnaesite flotation. Micro-flotation results indicated that DAHA, OAHA and HAHA displayed strong collecting affinity toward bastnaesite. And HAHA floated out 92.4% bastnaesite and 37.1% calcite from their artificially mixed minerals, inferring its excellent flotation selectivity toward bastnaesite versus calcite. The existence of HAHA elevated the zeta potential of bastnaesite, while had a slight effect on calcite. The entropy change Delta S, enthalpy change Delta H, free energy change Delta G (298 K) and activation energy E-a for bastnaesite adsorption of HAHA were 317.36 J.mol(-1).K-1, 74.53 kJ.mol(-1) 20.04 kJ.mol(-1) and 13.20 kJ.mol(-1), respectively, deducing an endothermic-spontaneous chemisorption process. FTIR and XPS recommended that HAHA chelated with surface Ce atom(s) to form five-membered hydroxamate-(O,O)-Ce complexes. And the amino group of HAHA facilitated its adsorption onto bastnaesite surfaces, thereby accelerated to generate surface complexes, resulting in a significant intensification toward bastnaesite flotation recovery.