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

Abstract

β-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 ΔS, enthalpy change ΔH, free energy change ΔG (298 K) and activation energy Ea 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.