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A comprehensive process of pretreatment and oxidation of lignin char was developed to optimize the production of activated carbon. The lignin char was obtained by carbonization of lignin under nitrogen at 600°C for 2 hours. The optimum time and temperature used to oxidize the char without destruction were, respectively, 6 hours and 245°C. The oxygen improves the reactivity of the sample in CO2and evolved the sample of a thermoplastic behaviour to a thermosetting behaviour. The oxygenation in air of the lignin char does not change the mode of deformation acquired by the material during the carbonization. The preoxidized coal reacts more than the nonoxidized coal during the CO2activation, whereas the reduction in volume in the first case is smaller than in the second. The preoxidized and then activated carbon shows the formation and the development of microporosity at the expense of macroporosity. This microstructure is one of the main characteristics of activated carbon, which can be used as adsorbent for different pollutants.

a b s t r a c tThis work focuses on the adsorption in aqueous solution of methylene blue (MB) and methyl orange (MO) on raw lignin (RL), on its derivative charcoals (LC and ACL) and on commercial activated carbon (CAC) taken as reference. Derivative charcoals are the lignin char (LC) and the activated carbon of lignin (ACL). The adsorbents were characterized by infrared spectroscopy, transmission electron microscopy and specific surface area measurements. The optimum conditions determined using experimental designs are 50 mg of lignin, 5 mg/L of dye and 30 min contact time. The studied response is the retention rate. As regards the RL, MB is better adsorbed than MO. As for LC, the adsorption of MB and that of MO are equivalent but are significantly lower than on RL. On the other hand, with ACL, the adsorption of MB and that of MO are higher than those on RL and LC. Infrared analysis reveals that the responsible functional groups of adsorption are present in RL and in ACL, but not in LC. Besides, the specific surface area value of LC is significantly lower than those of RL and ACL. The adsorption of MB on ACL is comparable to that on CAC, while that of MO is higher. IR analysis showed the fixation of MB and MO on ACL. The adsorption process of the two dyes both on RL as on ACL is controlled by chemisorption and the two dyes are adsorbed in multilayers on heterogeneous surfaces.