N. Nazriati, Istighfarin Meilidya Azhar, Irma Kartika Kusumaningrum
A silica aerogel/MgO composite synthesized from bagasse ash was investigated as a biomass-derived adsorbent for the removal of malachite green from aqueous solutions. The adsorption performance was systematically assessed by examining operational factors together with adsorption kinetics, equilibrium isotherms, and thermodynamic behavior. Equilibrium was attained after 80 min of contact time. Under the optimum conditions, the composite achieved an adsorption capacity of 123.19 mg/g at 45◦ C with an initial concentration of 55 mg/L, while the highest removal efficiency (90.93%) was obtained at pH 9. Comparative experiments demonstrated the superior adsorption capability of the silica aerogel/MgO composite relative to pristine silica aerogel. Adsorption capacities of 96.93 and 22.12 mg/g, respectively, were recorded under the same experimental conditions, highlighting the beneficial interaction between porous silica framework and MgO active sites. Analysis of adsorption kinetic revealed that the pseudo-second-order model most accurately represented the experimental data, yielding an R2 value of 0.9923. Equilibrium studies further indicated that the Freundlich isotherm provided the best fit (R2 = 0.9965–0.9973), suggesting adsorption on energetically heterogeneous surfaces with the possibility of multilayer uptake. Thermodynamic evaluation confirmed that the adsorption process occurred spontaneously and was favored at elevated temperatures. This behavior was evidenced by negative Gibbs free energy values (ΔG◦ = −4.68 to −6.29 kJ/mol), positive enthalpy changes (ΔH◦ = 12.46–15.29 kJ/mol), and positive entropy values (ΔS◦ = 58.76–67.10 J/mol·K. Overall, the results demonstrate the strong potential of the bagasse ash-derived silica aerogel/MgO composite as an efficient and sustainable adsorbent for the removal of cationic dyes from water. © 2026 The Authors.
Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Negeri Malang, East Java, Malang, 65145, Indonesia
