Synthesis of silica nanoparticles from blast furnace slag as cost-effective adsorbent for efficient azo-dye removal

Abstract

Synthesis of silica nanoparticles (NSBFS) from commercial blast furnace slag (BFS) and its efficiency to remove methylene blue (MB) from water as well as the desilicated blast furnace slag (DBFS) were investigated in this study. The sorbent materials were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), N2 adsorption-desorption isotherms, dynamic light scattering (DLS), scanning electron microscopy (SEM), and Energy Dispersive X-ray Analysis (EDAX). Different physiochemical parameters such as initial pH of the dye, sorbent dosage, contact time, and initial dye concentration were studied. The pseudo-first-order and pseudo-second-order models were applied to evaluate the kinetic mechanism of the adsorption process. The results show that the process follows the pseudo-second-order kinetics using NSBFS or DBFS. The adsorption equilibrium values were obtained using Langmuir and Freundlich equations, Langmuir model showed the best correlation indicate that NSBFS and DBFS are homogeneous surface. The batch adsorption experiments showed that the maximum sorption was observed at pH = 10 and 8 and the maximum uptake capacities (qm) for MB were 80.8 and 109.8 mg/g using DBFS and NSBFS, respectively.