THE USE OF FACTORIAL DESIGN IN OPTIMIZING THE PRODUCTION OF ALUM FROM EGYPTIAN KAOLIN CLAY

摘要

A statistical model based on an orthogonal factorial design was established to optimize the preparation of alum "aluminum sulfate" by leaching a local kaolin clay with sulfuric acid. XRF showed that it contained 25.5% alumina. The effect of the following parameters on the leaching process on the percent alumina recovery was studied: calcination temperature, leaching temperature, acid concentration, leaching time and kaolin particle size. A first order 2~5 model was first elaborated involving performing 32 runs under different conditions besides 5 runs at the center of design and applying the steepest ascent technique to obtain optimum conditions for maximum recovery. This model proved not to be adequate as a maximum point could not be reached. A second order model was then tried. An analytical expression was elaborated that yielded a determination coefficient of 0.91 and maximum recovery was obtained at the following conditions: calcination temperature = 690℃, leaching temperature = 81.5℃, acid concentration = 44.56% and leaching time = 192 min. This corresponded to about 82.5% recovery.