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 µm. 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.

Bentonite a natural raw material from the Šipovo mining deposits (Republic of Srpska), which contains a high percentage of montmorillonite, was treated to obtain montmorillonite clay ready for further investigations. Al-pillared montmorillonite was doped with 12-tungstophosphoric acid (WPA) by the sol-gel method. Substantial increase in proton conductivity of this new material was achieved. Different physicochemical methods were used to characterize new materials such as X-ray powder diffraction (XRD), thermogravimetric (TG) analysis, porosity measurements, scanning electron microscopy (SEM), and infrared measurements (IR). Impedance spectroscopy technique was applied in order to study the proton conductivity and its dependence on the frequency and tungstophosphoric acid concentration.

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The waste sludge generated during processing of iron ore in the Omarska mine (The Republic of Srpska, Bosnia and Herzegovina) is fine-grained (15μm), containing relatively high concentrations of iron, and quartz as its major impurity. The flocculation behaviour of the primary natural raw “quartz” sample from Omarska mine was studied in the present paper. This sample is composed of major quartz which dominates over minor contents of clay minerals and feldspars, and contain 92.9% of SiO2. Particle size distribution analysis confirm that it is present as fine and ultra-fine particles. The zeta potential of quartz depends on pH value. Settling experiments were performed by using three different dispersants (Na-hexamethaphosphate, Na-pyrophosphate and Na-silicate), and anionic polyacrylamide as flocculants. The best results were achieved with Nahexametaphosphate (1000 g/t) and anionic polyacrylamide A 100. The effect of a flocculant on the settling rate depends on solid concentration. Settling rates increase significantly with the increase of the liquid component in both cases (natural settling and hindered settling by addition of a flocculant).