Conversion of almond shell to activated carbons: Methodical study of the chemical activation based on an experimental design and relationship with their characteristics

The objective of this work is to carry out a methodical study of the preparation conditions of almond shell based chemically activated carbons and its influence on the characteristics of the activated carbons. An experimental design was used to optimize the preparation conditions of activated carbons from almond shell via chemical activation with phosphoric acid. Temperatures from 400° to 800 °C, impregnation ratios in the range 0.5–1.5 and carbonization times varying from 30 to 120 min were defined as continuous parameters to be introduced in a simplex mixture experimental design giving a total of 12 experiments to carry out. The response surface methodology was applied in order to study the influence of all the production parameters on the selected responses. The optimization of all the characteristics of the activated carbons under the same experimental conditions is not possible because the influence of activation temperature, impregnation ratio and activation time is different. However using the response surface methodology it is possible to determine the ranges of each experimental preparation condition to obtain optimal characteristics of the activated carbon. ► “Activated carbon” and “Chemical activation”: First study in the literature on optimization of the production of activated carbon from almond shell. ► “Response surface”: Three variables of preparation of activated carbons studied and optimized simultaneously. ► “Porosity” and “Functional Groups”: A compromise between surface area and porosity is found in a range of preparation conditions.