Etude de propriétés de physico-chimiques de charbons obtenus après activation chimiques de résidus ligneux du DIBETOU (Lovoa tyrichilioides Harms), de l'IROKO (Milicia excelsa C.C. Berg) et du MOABI (Baillonella toxisperma Pierre=.

Abstract

Our work has focused on the preparation, activation and study of physico-chemical properties of carbons from plant origin of three sub-products: chips of DIBETOU (Lovoa trichilioides Harms), IROKO (Milicia excelsa C.C. Berg) and MOABI (Baillonella toxisperma Pierre). We first carried out the chemical characterization (mineral analysis, chemical composition, humidity and dryness, infrared spectroscopy); determining the physical properties (density, porosity, and degree of crystallinity); morphological characterization (Scanning Electronic Microscopy). Then, in order to enhance these subs–products, activated carbons were prepared from theirs chips using chemical activation with the aqueous solutions of: NaOH, H2SO4 and H3PO4. The methodology of the experimental design was used to determine for each byproduct identified, the optimal conditions for carbonization and activation leading to the activated carbon which the effectiveness could be compared to those of commercial carbons. This methodology yielded the information sought by performing a minimum of experiments. Finally, we carried out the chemical characterization (determination of chemical properties, mineral analysis and determination of functional groups) and the physical characterization (specific surface area and porosity) of the carbons obtained. The best non activated carbon (IR75*) and activated carbon (6IRS601) have respectively the specific surface areas BET (SBET = 467 and 509 m2/g), the Langmuir surface areas (SL = 603 and 659 m2/g) while the best commercial activated carbon has a surface area BET (SBET = 900 m2/g). However, the best activated carbons from chips of DIBETOU, IROKO and MOABI indexed respectively 6DIS602 (C3), 6IRS601 (C7) and 2MON201 (C12) have specific surface areas, using iodine adsorption of 1518, 1571 and 1197 m2/g, while the best commercial carbon studied indexed F300 (C15) has a specific surface area of 1686 m2/g. Values of zero point charge of carbons activated by NaOH and those activated by H3PO4 indicate that these activated carbons contain acid and basic functions on their surface. These carbons are microporous. The values of specific surface areas indicate that IROKO is the best raw material while the sulfuric acid is the best activating agent.