Interfacial reaction mechanisms of potassium permanganate and sodium persulfate in separating stibnite from arsenopyrite

Arsenopyrite (FeAsS), as an accompanying mineral of stibnite (Sb 2 S 3 ), significantly restricts the efficient recovery and utilization of stibnite. In conventional flotation separation processes, the commonly used oxidizing agents are ineffective, and the oxidation mechanisms remain unclear, resulting in low separation efficiency. In this study, potassium permanganate (KMnO 4 ) and sodium persulfate (SPS) were used as oxidizing agents to investigate the effects of different oxidizing mechanisms on the flotation separation of stibnite and arsenopyrite. Microflotation experiments revealed that using SPS as the oxidizing agent produced an antimony concentrate with an antimony recovery of 73.02 % and an arsenic grade of 6.32 %. However, KMnO 4 failed to achieve effective separation. X-ray photoelectron spectroscopy (XPS) analysis showed that KMnO 4 extensively oxidized stibnite, generating products such as Sb(OH) 6 , HS - , and S 2 O 3 - . In contrast, SPS caused only limited oxidation of stibnite, primarily producing Sb(OH) 3 . Both KMnO 4 and SPS effectively oxidized arsenopyrite, but their selectivity differed, KMnO 4 predominantly oxidized iron, while SPS preferentially oxidized arsenic. Fe concentrations in solution, detected using inductively coupled plasma mass spectrometry (ICP), were 15 times higher under KMnO 4 oxidation conditions than under SPS conditions. Fe³⁺ ions enhance the oxidizing property of SPS, producing SO₄⁻ that oxidizes As, promotes its dissolution, and reduces the floatability of arsenopyrite, with minimal effect on stibnite. Under KMnO₄ oxidation, •O 2 - facilitates the chelation of Fe³⁺ in the form of Fe(OH)₃ with Sb(OH)₆ on stibnite's surface, forming a hydrophilic (HO)FeOOSb(OH)₄ film. This reduces the contact angle from 83.9° to 63.5°, thereby decreasing stibnite's floatability. These findings offer valuable guidance for selecting oxidizing agents to enhance the flotation efficiency of stibnite and arsenopyrite.