Utilization of Squaramide-Based Small-Molecule Depressant for the Selective Depression of Serpentine in the Flotation of Pentlandite

Serpentine, a magnesium-bearing gangue mineral commonly associated with pentlandite, severely impairs flotation selectivity through electrostatic heterocoagulation and slime contamination. In this study, a squaramide-based small-molecule depressant (SM) was rationally synthesized through amino functionalization of squaric acid and applied for selective serpentine depression. Micro-flotation results demonstrated that SM exhibited stronger depression performance toward serpentine than squaric acid while maintaining the floatability of pentlandite. In artificially mixed mineral flotation, SM effectively reduced serpentine interference and increased pentlandite recovery from 37.2% to 81.6% at pH 8.0. Adsorption measurements, zeta potential analysis, FTIR, and XPS results revealed that SM preferentially adsorbed onto serpentine surfaces through interactions between squaramide functional groups and Mg-containing active sites. This study provides a molecular design strategy for developing selective depressants for magnesium-bearing gangue control in sulfide ore flotation.