Electric arc furnace dust as magnetic carrier particles for removal of micro-fine particles from suspensions

[Display omitted] •EAF dust was first used as a magnetic carrier to remove micro-fine particles.•EAF dust was found to mainly consist of γ-Fe2O3 and be partly in nanoscale.•97.72% of SS was removed by EAF dust magnetic flocculation within 30s.•External magnetic fields can accelerate settling and compress settling sludge.•EAF dust magnetic flocculation was a novel low-cost method for SS removal. Electric arc furnace (EAF) dust, as a typical industrial waste, was often used as absorbents or building materials, which ignored its magnetic properties. In this study, EAF dust was first used as magnetic carrier particles to remove micro-fine particles from suspensions in hydrometallurgical processes. This dust was found to mainly consist of γ-Fe2O3 and 28.6% of it was below 900nm. Even though in fine particle size, the EAF dust still showed an excellent settleability under the combined assistance of polyacrylamide and external magnetic field. As an application example, EAF dust magnetic flocculation process was employed to remove micro-fine particles from oxygen pressure acid leachate of vanadium bearing stone coal, which was difficult to separate. The results revealed a maximum suspended solids (SS) removal rate of 97.72% within 30s. The SEM micrographs showed that SS particles either overlapped on the surface of coarse EAF dust or predominant agglomerated with fine EAF dust due to polymer bridging, forming large and compact SS-loaded magnetic floccules. The zeta potential analysis and DLVO theory calculations confirmed that the charge neutralization and mutual adsorption between micro-fine quartz and EAF dust. This study demonstrated that the EAF dust magnetic flocculation could efficiently remove micro-fine particles from suspensions, which may provide a cost-effective method for solid-liquid separation in hydrometallurgy.