Structural modification of hydroxamic acid collectors to enhance the flotation performance of malachite and associated mechanism

A series of N-hydroxy-N-aryl amide collectors, including N-hydroxy-N-benzyl acetamide (NHNBA), N-hydroxy-N-benzyl butyramide (NHNBB), N-hydroxy-N-phenyl acetamide (NHNPA) and N-hydroxy-N-phenyl butyramide (NHNPB), was designed in this study and employed for the first time in malachite flotation. Flotation tests conducted in the absence of frothers and activators revealed that the N-hydroxy-N-aryl amide collectors realized effective separation of malachite from calcite and quartz, which could not be readily achieved with benzohydroxamic acid (BHA). NHNBB exhibited optimal collection ability and selectivity for malachite over calcite and quartz. Quantum chemistry calculations, solution chemistry analysis and FTIR spectroscopy and XPS analyses revealed that in addition to electrostatic attraction, NHNBB possibly interacted with the malachite surface via chemisorption by forming five-membered-ring complexes, resulting in an efficient collection capacity for malachite.