Synthesis of nano-silica-coated peanut shell-derived bio-char composite for removal of safranin dye present in aqueous solution: batch and optimization using response surface methodology

Safranin is widely used in textile industries, and its discharge makes the effluent harmful to the environment. In this study, peanut shell biochar after chemical and thermal activation was coated with silica nanoparticles to make novel SiAcPNS 1:10 and was used to remove safranin dye present in solution. Detailed characterization of the nanocomposite was done using various equipment. The effect of different parameters was studied and adsorption isotherm, kinetics, and thermodynamic studies were done. Data derived from adsorption confirms Freundlich isotherm fitted best with R² value of 0.995. The highest adsorption capacity was 19.646 mg.g⁻¹. Furthermore, the negative ΔG value calculated from the thermodynamic study indicated that the process was spontaneous. Kinetic studies indicated that the adsorption followed the pseudo-second-order model. Experimentally, the highest removal of 97.22% was observed with the adsorbent dosage of 2 g.L⁻¹, initial dye concentration of 10 mg.L⁻¹, at 303 K, pH 8, and agitation speed of 130 rpm. Further optimization of the batch study was performed by response surface methodology (RSM).