Optimization of Methylene Blue Adsorption on Amphiprotic Bagasse Cellulose/TiO2 Magnetic Aerogel by Response Surface Methodology

Abstract

An amphoteric modification strategy was proposed to enhance the adsorption performance of biomass-based magnetic aerogels. Using sugarcane bagasse as the precursor, bagasse cellulose (BC) was extracted using a deep eutectic solvent at ambient temperature. Magnetic aerogels were fabricated by sequential cationization with 3-chloro-2-hydroxypropyltrimethylammonium chloride and anionization with 2-acrylamido-2-methylpropanesulfonic acid and amphiprotic BC/TiO₂ (AP-BC/TiO₂). These aerogels combined TiO₂ (a photocatalytic component) and Fe₃O₄ (a magnetic component) through an energy-efficient atmospheric pressure foaming process. The adsorption capacity for methylene blue (MB) was optimized using response surface methodology, with the mass concentrations of Fe₃O₄, AP-BC, and TiO₂ and initial concentration of MB as independent variables and the MB adsorption capacity as the response. A quadratic regression model was used to determine the optimal conditions. The AP-BC/TiO₂ magnetic aerogels exhibited an exceptional MB adsorption capacity of 1070 mg⋅g⁻¹. Adsorption kinetics and isotherms were modeled, and the structural/ physicochemical properties of the magnetic aerogels were characterized. The results confirmed the formation of a three-dimensional interconnected porous structure with uniform Fe₃O₄/TiO₂ loading and a saturation magnetization of 17.2 emu⋅g⁻¹. This enabled rapid magnetic separation and confirmed the potential application of amphiprotic biomass-based magnetic aerogels as eco-friendly and cost-effective adsorbents for MB.