Application of fractional factorial and Doehlert designs for optimizing the preparation of activated carbons from Argan shells

• Valorization of agricultural by-product
• Optimization of activated carbon preparation
• Good adsorption proprieties

A high quality activated carbon has been obtained, by physical activation with steam, from a Moroccan agricultural by-product (Argan shells) and their characteristics were investigated. In order to optimize experimental conditions of the preparation, a combination of a fractional factorial design and a Doehlert design was applied. In the first step of this work, a two-level fractional factorial design 2(5–1) was used to study effects and first order interactions of various factors such as atmosphere in carbonization step, carbonization time at 400 °C, activation temperature, activation time and steam flow. The results reveal that the most influential factors on the yield and the methylene blue adsorption are activation temperature, activation time, steam flow and the presence of a significant interaction between activation temperature and activation time in both cases. In the second step, activation temperature and activation time were optimized using Response Surface Methodology with a Doehlert design, and Desirability function. The optimal conditions for the preparation of activated carbon have been identified to be an activation temperature of 880 °C, an activation time of 96 min and steam flow fixed at this positive level of 0.2 cm3 min− 1. The characteristics of prepared activated carbon obtained at the optimal conditions were determined using adsorption capacity of methylene blue, iodine and phenol, BET surface area, pHpzc, and surface functions based on Boehm method. Those characteristics (MB adsorption: 608.9 mg g− 1, iodine adsorption: 1026.4 mg g− 1, phenol adsorption: 633.3 mg g− 1, BET surface area: 1292 m2 g− 1) were shown greater than those of a commercial activated carbon used in water treatment and those reported by other researchers studying activated carbon preparation from various solid wastes by steam activation method.On the other hand, this work showed that Argan shells are a good precursor for the production of activated carbon, by steam physical activation, with high performance to be used in water treatment applications.