Mechanistic Investigation and Industrial Validation of TBHB as a Dual-Functional Grinding Additive: Enhanced Grinding Efficiency and Surface Oxidation Suppression

In copper–molybdenum (Cu–Mo) beneficiation circuits, the incomplete liberation and extensive surface oxidation of chalcopyrite (CuFeS2) and molybdenite (MoS2) critically constrain their selective separation efficiency. To address this issue, we designed 3,4,5-trihydroxy-N,N-bis(2-hydroxyethyl)benzamide (TBHB), a derivative of the traditional grinding aid diethanolamine. TBHB demonstrates a dual-functional mechanism: on the one hand, it enhances grinding efficiency by promoting crack propagation in coarse chalcopyrite particles, reducing the D90 size (i.e., 90% passing size) by 67.26%; on the other hand, it suppresses overgrinding by inhibiting the agglomeration of fine molybdenite particles, thereby limiting the D10 size (i.e., 10% passing size) reduction to 28.42% compared to controls. This selective grinding action optimizes mineral liberation. Concurrently, FT-IR and XPS analyses confirmed that TBHB inhibits surface oxidation, preserving the inherent hydrophobicity of both chalcopyrite and molybdenite, essential for flotation. Adsorption studies revealed distinct adsorption mechanisms: TBHB chemisorbs onto chalcopyrite surfaces (fitting the Langmuir model, ΔG = –43.12 kJ/mol) via binding at the Fe sites while exhibiting physisorption onto molybdenite surfaces (fitting the Freundlich model, ΔG = –2.51 kJ/mol). The small-scale closed-loop experimental validation showed a 21.48% reduction in grinding energy consumption. Copper recovery and grade reached 99.93 and 26.20%, respectively, while molybdenum achieved 88.19% recovery and 49.26% grade, indicating superior metallurgical performance in the selective separation of Cu–Mo. This work underscores a molecular-design strategy for developing multifunctional additives that synergistically integrate the grinding and flotation processes for complex sulfide ores.