A novel green flotation approach: mechanism and simulation of Fe(Ⅲ)-enhanced small molecule acid for fluorite-calcite separation

Using Fe 3+ enhanced the inhibitory effect of MA on calcite. • Fe 3+ adsorbs on calcite CO 3 2– sites, providing new sites for MA adsorption. • A novel, efficient, and eco-friendly inhibitor based on the Fe–MA complex was proposed. Due to the similar surface properties of fluorite and calcite, selective adsorption of collectors remains a challenge in their separation. In this study, a novel composite inhibition system using Fe 3+ -enhanced Malic acid (MA) was developed to selectively suppress calcite by regulating interface coordination interactions. A systematic investigation was conducted through flotation tests, contact angle measurements, molecular dynamics simulations, and surface analysis (FTIR, ToF-SIMS, XPS). Micro-flotation results showed that the recovery of calcite decreased from 64.67% to 8.75% with the addition of Fe 3+ , while the fluorite recovery remained above 92%, indicating significant enhancement in selectivity. Contact angle and molecular dynamics simulations revealed that the Fe–MA complexes markedly increased the hydrophilicity of calcite surfaces. FTIR and ToF-SIMS confirmed the presence of carboxyl groups (–COOH) and iron species (FeO – , FeOH – ) on calcite surfaces, indicating Fe–MA complex adsorption. XPS and DFT results demonstrated that MA adsorbs onto calcite via weak Ca–O bonds, and Fe promotes multi-site adsorption through Fe–O bonds, strengthening the adsorption and enhancing separation efficiency. This study highlights a cooperative coordination mechanism between metal ions and small organic acids, offering a novel strategy for designing low-dose, highly selective green inhibitors for calcium minerals.