Precoat filtration of a deflocculated mineral suspension in the presence of a dispersant

This article presents the study of the filtration of an aqueous calcium carbonate suspension in the presence of dispersants in order to obtain filter cakes in the form of highly concentrated liquefied dispersions. Two methods were used in this investigation. The first method consisted of the filtration of a deflocculated (via dispersants) suspension (FDS). The second method involved a precoated filter cake that was initially formed from a free-dispersant suspension and then deflocculated by a dispersants suspension (DS) that was filtered through the precoat. Both methods allowed the liquefaction of the filter cakes after homogenisation. The precoat filtration of the deflocculated suspension (PFDS) nevertheless showed noticeable advantages compared to FDS. Precoat formed from a free-dispersant suspension resulted in the protection of the filtrate from molecules of the dispersant and from fine particles of the DS. The filter cake obtained by PFDS had lower specific resistance and liquefied at lower concentrations of the dispersant. The results of this study show that the PFDS process may be a new way of obtaining highly concentrated liquefied dispersions. (C) 2004 Elsevier B.V. All rights reserved.