Abstract
A novel biocomposite denoted Ns-AGS was synthesized from Alaeis guineensis Shells and nanosilica extracted from rice husk through a sol-gel method. The final product was applied in the adsorption of an azo dye namely Azocarmin G in synthetic aqueous solution. The characterization of the biocomposite by X-ray diffraction (XRD), Scanning Electron Microscopy, Fourier transform infrared spectroscopy (FTIR) and FTIR/TGA Analysis revealed an amorphous and porous microstructure with a random distribution of nanosilica particles in the lignocellulosic matrix evidencing several functional groups. The influence of contact time (0-120min), adsorbent dose (0.1-0.3g), initial dye concentration (25-100mg/L) and initial pH (3.5-6.5) were investigated at different temperatures (298°K, 316°K and 327°K). This study showed that adsorption of Azocarmin G onto Ns-AGS is favored by acidic pH values leading to more than 90% removal under optimal conditions of pH = 3.5; 60 min; 327°K for an adsorbent dose of 0.3g/25mL. The experimental kinetics data preferentially fitted the Hô model with a correlation coefficient R2 = 0.9992, indicating that adsorption is the determining step of the process illustrating adsorbate-adsorbent affinity. The equilibrium models demonstrated competitiveness, which may be related to the complex nature of the biocomposite. However, the Redlich-Paterson model, which combines Langmuir and Freundlich models, was more suitable at 327°K. The thermodynamic parameters demonstrated the spontaneity of the adsorption process (ΔG 0). The low activation energy value (2.92 kJ/mol < 20 kJ/mol) calculated using the Arrhenius equation reflects a physical adsorption that would involve weak Van der Waals and hydrogen bond interactions which combined to Hô model evolved competitivity between chemical and physical processes.