| abstract |
The present invention relates to a process for purifying water or for dewatering sludge, comprising the steps of contacting a surface-treated natural calcium carbonate, a natural bentonite and an anionic polymer with the water or the sludge, by aggregation of contained in the water or sludge particulate matter flakes are formed, and separating the flakes formed to obtain purified water or separating water to obtain a dewatered sludge. The surface-treated natural calcium carbonate is a reaction product of a natural calcium carbonate with an acid and carbon dioxide formed in situ by the acid treatment and / or externally supplied, and is prepared as an aqueous suspension having a pH measured at 20 ° C, from more than 6.0. The present invention further relates to a composition comprising the surface-treated natural calcium carbonate, a natural bentonite and an anionic polymer, for purifying water or for dewatering sludge. |