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 (CuFeS 2 ) and molybdenite (MoS 2 ) 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 D 90 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 D 10 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, Δ G = –43.12 kJ/mol) via binding at the Fe sites while exhibiting physisorption onto molybdenite surfaces (fitting the Freundlich model, Δ G = –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.