Activated carbon derived from palm date seeds as an adsorbent for methylene blue: kinetic and thermodynamic studies

Abstract

The present work shed light on the investigation of the textural and compositional properties of Activated Carbons derived from palm Date Seeds (DSAC). Initially, DS were pyrolyzed and chemically activated using H₃PO₄ activating agent at different ratio/temperatures. In that sense, various techniques were performed, particularly, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetry–differential thermal analysis (TGA/DTG), Brunauer–Emmett–Teller (BET) surface area analysis and energy dispersive spectroscopy (EDS) coupled to scanning electron microscopy (SEM). Our outcomes showed that the activation with H₃PO₄ at lower and higher ratio produced activated carbons with higher pore volume (0.507 and 0.680 cm³/g), narrower average pore diameter (1.10 and 1.49 nm) and higher surface areas (917.082 and 828.60 m²/g). DSAC were used for the adsorption of methylene blue (MB) dye from an aqueous solution. The adsorption efficiency of the studied samples was investigated varying the amount of activated carbon, contact time, temperature and initial dye concentration. Acid-activated samples showed improved adsorption capacity for MB compared to pyrolyzed ones: up to 302 mg/g. This was mainly attributed to a more adequate texture as confirmed by the presence of a pronounced porosity in the SEM analyses. The adsorption equilibria were analyzed; the Langmuir isotherm revealed the best correlation with the experimental data, and the pseudo-second-order kinetic model was the most suitable for the adsorption of MB dye. The thermodynamic parameters revealed the spontaneity and endothermicity nature of the MB adsorption process. According to the obtained results our synthesized added-value product can be used to remove dyes contained in industrial effluent.