Selective flotation of lepidolite from silicate gangue using a novel epoxypropyl quaternary ammonium collector DEDAC

The selective flotation separation of lepidolite from major silicate gangue minerals such as K-feldspar and quartz has long faced technical challenges due to their similar surface properties. In this study, a novel collector, dodecyldimethyl epoxypropyl ammonium chloride (DEDAC), was designed and synthesized. Its flotation performance was systematically evaluated in comparison with the conventional cationic collector dodecylamine (DDA). The results showed that DEDAC maintained high lepidolite recovery over a wide pH range of 2–10. Its pH adaptability was significantly better than that of DDA. However, at neutral pH without a depressant, all three minerals exhibited similarly high floatability, resulting in poor selectivity. At pH 4 with 20 mg/L DEDAC, the recovery of lepidolite reached 76.5 %, while those of K-feldspar and quartz were both below 25 %, demonstrating excellent selectivity. At pH 7, the addition of sodium hexametaphosphate (SHMP) effectively depressed the gangue minerals, reducing their recoveries to less than 15 %, while retaining about 73.5 % recovery for lepidolite. Artificial mixed ore tests further validated the practical value of DEDAC. Under acidic conditions, the Li 2 O recovery exceeded 93 % in both binary and ternary mixed ores. With SHMP at neutral pH, the recovery remained above 92 %. Mechanistically, DEDAC selectively adsorbs onto lepidolite surfaces primarily through electrostatic attraction, with its superior molecular stability conferring broad pH adaptability and its strong positive charge enhancing adsorption affinity. SHMP selectively inhibits DEDAC adsorption on gangue minerals through competitive adsorption, while exerting only a minor effect on lepidolite, thereby significantly improving flotation selectivity. These findings demonstrate that DEDAC is a promising selective collector for lepidolite flotation with good collecting ability, broad pH adaptability, and synergistic performance with SHMP.