Effective adsorption of Brilliant Pink-B dye using bio adsorbent synthesized from agriculture waste: isotherm, kinetic, and thermodynamic studies

Avena fatua husks, an agricultural waste, were used to create highly pure silica nanoparticles (SiO₂) and then tested as a bio-adsorbent to eliminate cationic dye from an aqueous solution. SEM and AFM studied silica nanoparticles’ surface morphology and topography, and the result revealed an average particle size of 40 nm. The SiO₂ nanoparticles exhibited high adsorption capacity with a specific surface area of 400 m²g⁻¹. The XRD pattern exhibits the amorphous nature of the material with 2θ = 23° at full-width half maximum (FWHM). The EDX measurements show the composition of nano-silica contains a small amount of carbon, 9.9%. The steady-state data are consistent with the Langmuir and Freundlich models, and the Langmuir model fits them perfectly. Thermodynamic parameters indicate that the adsorption removal process is spontaneous and exothermic. They recycled the SiO₂ nanoparticles after dye adsorption, which was adequately acceptable, with the possibility of reuse more than four times.