Mechanism of the novel depressant sodium poly[(naphthaleneformaldehyde)sulfonate] in the flotation separation of cassiterite from calcite

TAMOLL selectively adsorbed on the surface of calcite. • Using TAMOLL can effectively separate cassiterite from calcite. • The S-O - and S=O groups in TAMOLL chemically interacted with the Ca sites on calcite. The flotation separation of cassiterite from calcite has long been a challenge. In this study, the eco-friendly depressant sodium poly(naphthaleneformaldehyde sulfonate) (TAMOLL) was employed. Single-mineral tests demonstrated that TAMOLL strongly depressed calcite while barely affecting cassiterite. In the artificially mixed mineral system, a cassiterite concentrate grading 66.69% with a recovery of 86.59% was obtained at 16 mg/L TAMOLL. Multi-technique characterization, including contact angle, zeta potential, FTIR, XPS, and ToF-SIMS, combined with DFT calculations, systematically elucidated the selective depression mechanism. The sulfonate groups (−SO 3 - ) of TAMOLL coordinate with Ca sites on calcite via S-O - and S=O bonds, accompanied by pronounced electron transfer and orbital hybridization, forming stable S-O-Ca bonds. This leads to a dense, hydrophilic film on calcite, whereas TAMOLL adsorption on cassiterite is negligible, substantially widening the floatability difference. Consequently, cassiterite can be effectively floated by the subsequent NaOL collector. The strong chemisorption between TAMOLL and calcite is therefore the core mechanism, endowing TAMOLL with outstanding selective depression performance in cassiterite-calcite separation. Download: Download high-res image (201KB) Download: Download full-size image