Three physico-chemical characteristics of Acacia activated charcoals were determined: the degree of activation, the specific surface and surface functions. The coals are prepared from Acacia auriculaeformis and Acacia mangium, leguminous and fast growing trees, available in Côte d’Ivoire. They were activated by chemical means, by impregnation with phosphoric acid (H3PO4). Analysis of the results indicates that the activation yields are below 50% for both types of coal. In addition, the activated carbon-based Acacia auriculaeformis has a larger surface area than that based Acacia mangium. The two activated coals have mixed surface functions, predominantly acid, which give them a dual reactivity for both anionic and cationic adsorbates.
Four lots of chars have been produced from woods of Acacia auriculaeformis and Acacia mangium, 8-9 and 23-24 years old. The aim of this study is to determine the optimal age of the woods in order to obtain high quality activated carbon. From the comparative analysis of physico-chemical properties of the chars, it has been found that the relative densities increase from 8-9 years old trees to 23-24 years old trees (0.39 to 0.43 for A. auriculaeformis and 0.31 to 0.38 for A. mangium. The ashes rate decreases with the increasing of the age of wood: from 1.075 to 0.990% for A. auriculaeformis, from 1.025 to 0.925% for A. mangium. Otherwise, the rate of volatiles of the chars don't practically change whatever the age and the species (from 23.24 to 23.66% for A. auriculaeformis and from 24.40 to 24.92% for A. mangium). The same tendency is observed with the rate of fixed carbon: from 74.69% and 73.58% for 8-9 years old woods, they are, respectively 74.35% and 73.16%. We can conclude that technical, economic and environmental point of view the activation of chars produced from 8-9 years old woods can be recommended.
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