Optimization of conditions for the preparation of activated carbons from olive-waste cakes

An experimental design (Doehlert matrix) has been drawn up to optimize the experimental conditions of the preparation of activated carbon from olive-waste cakes. A series of activated carbons have been prepared by physical activation with steam. Adsorption of N-2 (77 K), CO2 (273 K) and mercury porosimetry experiments have been carried out to determine the characteristics of all carbons prepared. Adsorption of iodine and methylene blue was used as a primary indicator of the adsorption capacity of these carbons. The experimental response varied between: 13-27% for the total yield (Y-1), 115-490 mg/g for the adsorption or methylene blue (Y-2). 741-1495 mg/g for the adsorption of iodine (Y-3), 514-1271 m(2)/g for the BET surface area (Y-4), 0.225-0.377 cm(3)/g for the micropore volume (Y-5), 0.217-0.557 cm(3)/g for the volume of pores with a diameter greater than 3.7 nm (Y-6) and 31.3-132 m(2)/g for the external surface area (Y-7). The results obtained were exploited using response surface methodology. These responses have been represented and studied in all experimental regions of activation time and activation temperature, the most influential factors in activated carbon preparation. Optimization to obtain activated carbons with textural characteristics suitable to use in water treatment has been carried out. The optimal activated carbon is obtained when using 68 min as activation time and 1095 K as activation temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.