Comparative Study of the Mineral Composition and Its Connection with Some Properties Important for the Sludge Flocculation Process-Examples from Omarska Mine

Abstract

Studied sludge samples are composed of major goethite and quartz; less clay minerals; and minor magnetite, hematite, clinochlore and todorokite. They have quite similar qualitative, but different semi-quantitative compositions. There are similar particle size distributions between the samples, and the highest contents of ~50% belongs to the finest classes of <6 m. Among size classes within the samples, almost identical iron contents are present; indicating their similar mineral compositions, which make these systems very complex for further separation processes. Sludge II has a higher natural settling rate, due to its higher density and mineral composition. With addition of the flocculant, settling rates increase significantly with the increase of the liquid component in both of the samples. The effect of flocculant on the settling rate is different between samples, and depends on their mineral composition. The time of settling does not play a role in selectivity, to the ratio of the mass of floating and sinking parts, and iron content does not change with time. The content of iron partially increases by flocculation; therefore, this method should be considered as an appropriate one. Zeta potential values for sludge are mostly between those for goethite and quartz, indicating their particle mixture and intricately association.