SPRAY-DRIED CALCINED CLAYS IN WATER FILTRATION COLUMNS USED FOR CHROMIUM REMOVAL

Well-rounded grains are normally used as filtration media, because the spherical shape seems to be most suitable to get rapid and efficient removal operations. In this sense, the direct use of natural clays as filtration media is problematic, due to the plate-type shape of the pa l-tides. In this work, rounded grains of two natural clays processed b y spray-drying are tested as filtration media. The settling regime of the grains in a filtration column was determined and the chromium remo val from water was also tested. Sieved fractions now used(355-1680 mu m) show settling behavior according to the transition regime. Prelimin ary results of chromium removal by the selected 355-420 mu m sieved fr action bed show interesting capabilities for the Cr3+ species, while c hromate (VI) retention is extremely low.