Substituent-regulated benzoic hydroxamic acid derivatives for selective flotation of bastnaesite: experimental study and structure-activity relationship analysis

First combined application of DFT calculations and RDKit-based analysis for the structure–activity relationship study of BHA derivatives in bastnaesite flotation. • 3OMeBHA achieves 49.06% selectivity index, outperforming BHA and industrial H205 in mixed-ore tests. • Selectivity governed by ΔE (R =  − 0.90); gangue adsorption correlated with I min (0.92) and V max (0.87). The limited selectivity of benzohydroxamic acid (BHA) between rare-earth and calcium-bearing minerals remains a challenge due to their similar surface active sites. In this study, a series of BHA derivatives were synthesized via substituent modification to optimize their electronic and spatial configurations. Among these, the meta -methoxy derivative (3OMeBHA) exhibited superior selectivity, achieving a selectivity index of 49.06% and outperforming the industrial collector H205 in actual ore tests. Integrating flotation experiments with RDKit-based molecular descriptors and density functional theory (DFT), we elucidated the structure–activity relationships. Correlation analysis revealed that calcite recovery is primarily governed by the minimum average local ionization energy and maximum electrostatic potential, while the selectivity index strongly correlates with the energy gap. DFT results indicate that 3OMeBHA’s higher-lying highest occupied molecular orbital (HOMO) and delocalized orbitals promote specific coordination with Ce 3+ on bastnaesite while suppressing non-selective interactions with Ca 2+ on gangue minerals. This work provides a high-performance collector for bastnaesite flotation and clarifies the electronic mechanisms of substituent effects on mineral-collector interactions. Download: Download high-res image (202KB) Download: Download full-size image