Air sparging during the solid/liquid separation by microfiltration: application of flotation

A large number of techniques have been used today to limit the membranes fouling and among them, certainly is air bubbling constituting also the transport medium in flotation, as applied in wastewater treatment; flotation is suitable as a pretreatment stage for microfiltration. Ceramic flat-sheet membrane modules were used in this paper, of multi-channel geometry and mainly their fouling tendency and the obtained membrane fluxes were investigated. The objective was to apply, in the laboratory, microtiltration by submerged membranes for the efficient (their observed recovery was of the order of 100%) separation of metal-loaded zeolites. The latter are a typical example of sorbents capable to bond fast and effectively toxic metal cations from contaminated wastewater, however, due to their ultratine size, separation downstream is aenerally required. Promising results were realized, regarding the air presence, bubbles size (experienced by inserting in the solution a frother or changing the porosity of the used air diffuser) and solids concentration against the transmembrane pressure (TMP). Flotation was exercised to a real mine effluent. (C) 2003 Elsevier B.V. All rights reserved.