Abstract:The purpose of this study is to evaluate the adsorption capacity of two adsorbents from the lignocellulosic residues of Lophira Lanceolata. The raw hull of Lophira Lanceolata and its activated carbon produced by chemical activation with orthophosphoric acid (H 3 PO 4 ) at 50% (Vacid/V water ) of the said hull. The ratio of impregnation to orthophosphoric acid used is 4.5. Activation and carbonization were carried out at 400°C. The physicochemical properties of the prepared activated carbon were determined and methylene blue adsorption tests were performed. On the basis of the results obtained, the iodine test revealed that the activated carbon produced had a microporosity of 646.81 mg/g, a density of 0.3156, a moisture content of less than 15% and ash content equal to 2%. Regarding the adsorption, results showed that methylene blue (100 ppm) adsorbed more easily on the activated carbon produced than on the crude residues with respective contact time of 10 minutes and 40 minutes. The removal rate was of the order of 100% for the activated carbon and of 83.56% for the raw hulls. Furthermore, an influence of the mass of the support, of the initial concentration and of the pH on the kinetics and on the adsorption capacity was observed. Kinetics obeyed to the pseudo-second order model; the diffusion was intra-particular and the Freundlich and Langmuir models satisfactorily described the adsorption of methylene blue respectively on the crude residues and on the produced activated carbon.

In this work, we valorized two wastes of plant origin in activated carbon (AC) by chemical activation, with a view to their use for the elimination of industrial dyes and artisanal dyeing simulated by methylene blue and iodine in the water. These are coconut shells (Coco nucifera) and teak wood chips (Tectona grandis). For the preparation of activated carbon based on coconut residues, the chemical activation was carried out by citric acid extracts of lemon juice (Citrus aurantiifolia) and then compared to that carried out with phosphoric acid and hydroxide of potassium. For the preparation of activated carbon from the teak residue, the activating agent used is potassium hydroxide. The results obtained show that activated carbon based on the coconut are microporous and mesoporous with an iodine number between 338.9 and 487.9 mg/g, a methylene blue number between 369.2 and 447.2 mg/g and a more pronounced post-treatment residual acidity for phosphoric acid than with lemon juice. The test conditions (the impregnation ratio, the duration, and the carbonization temperature) made it possible to prepare six activated carbons from the teak residue. The carbonization time does not have a significant effect on the adsorption efficiency although it does have a considerable effect on the carbonization efficiency. The adsorption kinetics of methylene blue on these materials is second order and the adsorption isotherm is more of the Langmuir type than that of the Freundlich model; this isotherm is characteristic of a wide distribution of microporosity and a well-developed mesoporosity. These activated carbons can therefore be used in the treatment of wastewater, in particular for the removal of industrial dyes and artisanal dyeing.