Ammonium Citrate Strengthens the Surface Sulfide Layer on Cerussite and Improves Flotation

Abstract Cerussite is an important lead oxide mineral that is commonly recovered by sulfidization followed by SBX flotation. In the flotation process, prolonged sulfidization can cause the surface sulfide layer to detach and degrade. This decreases surface hydrophobicity and floatability, resulting in lower flotation recovery. To address this limitation, ammonium citrate (AC) was introduced as an enhancer to promote the formation of surface sulfidization products and stabilize their adsorption. Microflotation tests showed that the flotation recovery of cerussite reached 89.18% after 3 min of sulfidization, but decreased to 62.63% after 30 min. In the 30 min sulfidization system, AC increased flotation recovery to 88.35%. ICP-OES and UV–vis results indicate that extended sulfidation time decreases the adsorption of sulfur species and sodium butyl xanthate on cerussite, and AC markedly enhances such adsorption. SEM-EDS and LEIS analyses showed that AC promoted uniform, compact growth of the surface sulfide layer and strengthened interfacial bonding. X-ray photoelectron spectroscopy further showed that AC enhanced the formation of Pb–S species on cerussite after prolonged Na2S treatment. AC also optimized the surface speciation of polysulfide species. Together, these effects stabilized the surface sulfide layer, increased surface hydrophobicity, and improved flotation recovery.