Synthesis, flotation behavior, and structure-performance relationship of three hydroxyl-containing cationic collectors

Removal of quartz from hematite by reverse flotation using cationic collectors is an effective approach for iron concentrate upgrading. In this paper, three hydroxyl-containing cationic collectors, i.e., N-Dodecylethanolamine (NDEA), N-Dodecylpropanolamine (NDPA), and N-Dodecylbutanolamine (NDBA), were synthesized and characterized. The flotation performance and the structure-performance relationship of the collectors were systematically investigated by micro-flotation experiments and various surface analysis techniques. At the concentration of 20 mg/L, the flotation recoveries of quartz by NDEA, NDPA, and NDBA were 94.9 %, 93.5 %, and 93.3 %, respectively. Collectors with shorter hydroxyl-substituted carbon chains exhibited stronger collecting ability and enhanced hydrophobicity of quartz surface, as confirmed by contact angle measurements. Zeta potential measurements and molecular simulations revealed that the collectors adsorb onto the quartz surface through electrostatic and hydrogen bonding interactions. The introduced hydroxyl groups could enhance the formation of hydrogen bonds between collectors and mineral surface. However, as the carbon chain length increases, the adsorption area of a single collector on the mineral surface increases, the number of collector molecules adsorbed per unit area decrease, reducing the collecting ability of the collector for quartz. This research could provide theoretical guidance for the design of novel cationic collectors.