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 particles. In this work, rounded grains of two natural clays processed by spray-drying are tested as filtration media. The settling regime of the grains in a filtration column was determined and the chromium removal from water was also tested. Sieved fractions now used (355–1680 μm) show settling behavior according to the transition regime. Preliminary results of chromium removal by the selected 355–420 μm sieved fraction bed show interesting capabilities for the Cr³⁺ species, while chromate (VI) retention is extremely low. Received: 12 January 1998 Accepted: 2 April 1998