Molybdenite–pyrite flotation separation under low-alkalinity conditions using trisodium cyanurate as a selective pyrite depressant: Flotation response and interfacial insights

A small-molecule pyrite depressant, trisodium cyanurate (Na 3 CA), is proposed. • Na 3 CA enables selective separation of molybdenite from pyrite under low-alkalinity conditions. • The selectivity originates from preferential Na 3 CA adsorption on pyrite. • O and N donor groups are identified as key sites for Na 3 CA adsorption on pyrite. Conventional molybdenite–pyrite flotation commonly relies on CaO to depress pyrite under strongly alkaline conditions, which requires high reagent dosages and may raise environmental concerns. Developing efficient pyrite depressants for low-alkalinity conditions is therefore highly desirable for molybdenite flotation. This study employed trisodium cyanurate (Na 3 CA) as a pyrite depressant and investigated its flotation selectivity and interfacial interaction mechanism. Single-mineral flotation tests showed that Na 3 CA exhibited high separation selectivity, maintaining molybdenite recovery at 96.78 % while reducing pyrite recovery to 3.10 % at pH 8.0 and 40.0 mg/L. Bench-scale flotation of real molybdenum ore confirmed the applicability of Na 3 CA, achieving a Mo concentrate with a Mo grade of 47.25 % and a recovery of 79.90 %. Integrated interfacial investigations based on wettability, zeta potential, FT-IR, XPS, and DFT analyses indicated that Na 3 CA exhibited a stronger adsorption affinity for pyrite than for molybdenite, thereby markedly enhancing the hydrophilicity of pyrite. FT-IR, XPS, and DFT analyses further indicate that this selectivity is mainly associated with chemisorption interactions involving the O and N donor atoms of Na 3 CA and surface Fe sites on pyrite. These findings indicate that Na 3 CA is a promising selective pyrite depressant for molybdenite–pyrite flotation separation under low-alkalinity conditions.