Influence of binder composition on hematite-rich mixed minerals agglomeration behaviour and product properties

Physicochemical interactions between the mineral particles and liquid binder play a pivotal role in controlling the agglomeration behaviour and defining the agglomerate attributes. In this study, the effect of tap water, saline water (2 M NaCl) and 30% and 44% w/w H2SO4 solutions as binders on agglomeration behaviour and product attributes (compressive strength, re-wetting stability and microstructure) of a hematite-rich mixed minerals was investigated. The results revealed that at equivalent binder mass dosage of 13 wt.%, albeit different binder volume dosages, the agglomeration with tap and saline water displayed markedly faster nucleation and coalescence-controlled agglomerate growth behaviour. The acidic solutions led to slower nucleation followed by pseudo-layering agglomerate growth behaviour, the extent of which was greater at 44% than at 30% w/w H2SO4 binder addition. Generally greater compressive strength and re-wetting stability were displayed by the acid-bound agglomerates compared with tap water and saline water-bound ones. The internal microstructural analysis revealed that the pore volume fractions of the wet agglomerates were almost independent of the binder type. In the dry state, however, the pore volume fractions of the water-bound agglomerates were slightly lower than that of acid-bound ones, both were, however, markedly higher than those observed for wet agglomerates. The increase is believed to be due to particles' shrinkage resulting from interfacial stresses and strains following moisture loss during drying. The observed outcomes highlight the importance of binder type and their impact on agglomeration behaviour and product characteristics.