Flotation separation of phosphate ore is achieved through selective inhibition by hydroxyethylidene diphosphonic acid

Phosphorus, a vital strategic mineral, finds broad industrial applications, yet continuous depletion of high-grade phosphate deposits renders efficient clean separation of apatite and dolomite from low-grade phosphate ores a pressing challenge in mineral processing. This work adopts hydroxyethylidene diphosphonic acid (HEDP) as a high-efficiency selective depressant for apatite-dolomite flotation separation, evaluates its separation performance systematically, and reveals its micro-interfacial regulation mechanism through multi-scale characterizations. Micro-flotation and mixed mineral tests confirm HEDP delivers outstanding selective inhibition under weak alkaline conditions. For artificial mixed ores, it boosts P 2 O 5 grade to 37.18% with 85.6% recovery. Closed-circuit reverse flotation of Yunnan sedimentary low-grade magnesium-rich phosphate rock yields concentrate containing 27.52% P 2 O 5 at 96.04% recovery, while lowering concentrate MgO to merely 0.43%. Combined contact angle, zeta potential, FTIR and XPS analyses illustrate the underlying mechanism. Phosphonic acid groups of HEDP preferentially form strong chelating chemical adsorption with surface Ca 2+ sites of apatite, generating a compact, highly hydrophilic barrier that thoroughly obstructs hydrophobic attachment of NaOL. In contrast, HEDP only weakly binds dolomite via trivial physical adsorption or hydrogen bonds without altering its surface electronic environment, allowing NaOL to adsorb readily and retain strong floatability. SEM-EDS and ToF-SIMS further validate such divergent interfacial adsorption behaviors. This study elucidated the selective regulation mechanism of HEDP at the interface of Ca/Mg non-metallic minerals, providing important theoretical guidance for the efficient removal of magnesium, improvement of grade, and high-value development of complex, difficult-to-select, and low-grade phosphate rock ores.