The effect of phosphoric acid on the properties of activated carbons made from Myrtus communis leaves: Textural characteristics, surface chemistry, and capacity to adsorb methyl orange

• Published in: Journal of molecular structure 2025-02, Vol.1321, p.140038, Article 140038
• Main Authors: Megherbi, Hamza, Runtti, Hanna, Tuomikoski, Sari, Heponiemi, Anne, Hu, Tao, Lassi, Ulla, Reffas, Abdelbaki
• Format: Article
• Language: English
• Subjects: Activated carbons; Adsorption; Methyl orange; Myrtus communis leaves; Phosphoric acid; Specific surface area
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2024.140038

•A new activated carbon (AC) with high specific surface area of 1237m2/g was achieved through straightforward heat treatment, utilizing (MC-Leaves) biomass and phosphoric acid as the chemical catalyst.•The effects of phosphoric acid impregnation ratios were shown to include changes in surface chemistry, pore formation, structural morphology, and surface area expansion.•High (MO) (qmax) of 326.54±37.67 mg g-1 was obtained at temperature of 22 °C using 150 wt.% of phosphoric acid impregnation ratio.•Adsorption capacity impacted by phosphoric acid, and increased as phosphoric acid concentration rose. In this work, chemical activation was employed to produce activated carbons and assess the impact of phosphoric acid (H3PO4) on their physicochemical properties. Using Myrtus communis Leaves (MC-Leaves) as the precursor and varying H3PO4 impregnation ratios (30 %, 60 %, 100 %, and 150 wt.%). The activation was conducted at 450 °C (10 °C/min) for 1 h in a room atmosphere. The effects of H3PO4 were evaluated through various techniques, including BET surface area analysis, FESEM-EDS imaging, XPS, FT-IR-ATR, Raman spectroscopy, CHNS-(O) elemental analysis, and Methyl orange (MO) adsorption studies. The specific surface area (SSA) and total pore volume increased from 642m2/g to 1237m2/g, total pore volume increased from 0.29cm3/g to 0.97cm3/g, and the mean pore diameter increased from 1.9 nm to 3.2 nm by increasing the impregnation ratio from 30 wt.% to 150 wt.%. The pH(pzc) of MC-ACs exhibited an acidic character, owing to the presence of oxygen-containing functional groups such as hydroxyl, carboxyl, metaphosphate (-PO3-), phosphates, and pyrophosphate groups, as indicated by XPS and FT-IR analysis. At a room temperature of 22 °C and an ideal pH of 2.06, the maximum adsorption capacity (qmax) rose from 46.02±4.63 mg g-1 to 326.54±37.67 mg g-1 as the impregnation ratio increased from 30 wt.% to 150 wt.%. Freundlich isotherm well explained the adsorption equilibrium at 22 °C for all MC-ACs. The effect of temperature illustrates that the adsorption of MO onto MC-AC30 % was endothermic, while the adsorption of MO onto MC-AC150 % was an exothermic. The kinetic study was conducted at 22 °C, when the equilibrium time was at 4hours, and it was a pseudo-second order (PSO) model. [Display omitted]