Evaluation of Adsorption Capacity of Methylene Blue in Aqueous Medium by Two Adsorbents: The Raw Hull of Lophira Lanceolata and Its Activated Carbon

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 (H3PO4) at 50% (Vacid/Vwater) 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.