Highly permeable twinned alumina nanoparticles for the precoat filtration of fine colloids

Abstract

Abstract Pretreatment is key to the success of any fine filtration process. Precoat filtration is a common method to reduce fine particulate matter in feed streams. In this study, precoat filters were formed by the deposition of the diatomaceous earth (DE) or twinned alumina nanosheets (TAN) particles on a substrate. The TAN particles were produced via metal salt hydrolysis. The performance of the precoat filters was investigated during the constant-pressure filtration of a bentonite solution. The results showed that the TAN precoat exhibited enhanced flow properties and reduced the turbidity of the filtrate more rapidly than either of the DE precoats. The TAN precoat reached the required turbidity level of ≤0.10 NTU at a flux that was up to 28 times higher than the fluxes obtained by the DE precoats. The superior performance of the TAN precoat was explained by (1) the ability of the TAN precoat to resist compaction during filtration due to the unique twinning of the alumina nanosheets forming the TAN particles, (2) the strong attractive forces between the bentonite and TAN particles based on their opposite surface charges, and (3) the isotropic permeability of the TAN aggregates.