Benzohydroxamic acid derivatives: Structure-activity relationships in the malachite flotation

Bis-minerophilic groups can improve the flotation performance of the collector and reduce the use concentration. In this study, the benzohydroxamic acid derivatives, phthaloyl hydroxamic acid (PHA), isophthaloyl hydroxamic acid (IHA), and terephthaloyl hydroxamic acid (THA), were synthesized and first introduced as the collectors in the flotation separation of malachite. Compared with the traditional collector, benzohydroxamic acid (BHA), their collecting abilities to malachite were followed as IHA > BHA > PHA >> THA. For the artificial mixed mineral, 3.0 x 10(-4) mol/L IHA without Pb2+ ions recovered about 82 % malachite, 23 % calcite and 17 % quartz at pH 8.0. Under the same conditions, their recoveries with BHA were around 56 %, 17 % and 15 %, respectively. The contact angle and adsorption amount results exhibited that THA could adsorb on the malachite surface but could not enhance its surface hydrophobicity. The ion action and SEM proved that PHA would corrode the malachite surface, resulting in unstable adsorption. XPS and DFT revealed that the suitable molecular structure of IHA could easily chelate with the Cu atoms to form two five-membered rings due to its stronger electron-donating ability and weaker electron-accepting ability. This study provided the theoretical support for the design and application of novel collectors used in the lead-free flotation enrichment of copper oxide resources.