Study on the enhanced flotation performance of fine coal slime by microemulsion collector: simulation and experiment

Fine coal slime generally exhibits poor floatability, while conventional hydrocarbon oil collectors often suffer from limited flotation efficiency. To address these challenges, a microemulsion collector (OPAOW) was developed by integrating dissipative particle dynamics (DPD) simulations with experimental characterisations to enhance the flotation performance of fine coal. DPD simulations revealed that the interfacial-layer thickness initially increased and subsequently decreased with increasing mass ratio of surfactant to co-surfactant (Km), reaching an optimum at Km = 1.6. An Smix(S + CoS) content of 30–50% was identified as suitable for microemulsion formation, whereas n-hexanol produced the largest single-phase region among the co-surfactants evaluated. Mixture-design optimization identified a formula containing 43.42% Mix (S + CoS), 26.67% diesel, and 29.91% water before model restoration. The microemulsion prepared at this optimised composition exhibited a mean droplet size of 18.61 nm, closely matching the predicted value. At comparable clean-coal ash contents, OPAOW increased the clean-coal yield and combustible-matter recovery by 16.17% and 18.93%, respectively, relative to diesel. Flotation with OPAOW followed the classical first-order kinetic model, yielding a theoretical maximum combustible-matter recovery of 92.44%. Overall, OPAOW exhibited superior collecting performance, lower reagent consumption, and enhanced flotation selectivity, highlighting its potential as an efficient collector for fine coal slime flotation.