A study on the preparation of fine and low soda alumina

摘要

A simple process to produce fine and low soda a-alumina (alpha-Al_2O_3) from a commercial grade aluminium trihydroxide (gibbsite, A1(OH)_3) produced by KC Corporation Ltd was developed. There are two options for this process with the first one producing low soda a-alumina (<0.05 percent Na_2O) having a mean particle size of 50 mu m The second option yields a fine product with a mean size of less than 10 p. In the first option, a plant aluminium trihydroxide containing 0.20 percent Na_2O was first fluidized with nitrogen at 400-600 deg C to yield an amorphous activated alumina. This intermediate product was then treated with acetic or oxalic acid, washed with water and heated to 1200 deg C to form calcined a-alumina, having a Na_2O content of less than 0.05 percent. A 20 min leaching using 0.2 M acetic or oxalic acid could yield an alumina product containing 0.04 percent Na_2O. In the second option, a new technique for the preparation of fine and low soda a-alumina was evaluated using an attrition mill working also as a leaching vessel at 80 deg C. Fine (< 10 pm in mean particle size) and low soda (<0.04 percent Na_2O) alumina was produced by a 20 min leaching step with 0.2 M acetic acid and concurrent attrition milling.