Preparation of succinic anhydride-functionalized glucose-based carbon microspheres for selective adsorption of cationic dyes

Abstract

Given the pervasive existence and toxicity of organic dyes, especially benzidine-derived dyes, it is imperative to develop effective wastewater treatment solutions. In this study, a straightforward method was developed to prepare succinic anhydride-modified glucose-based carbon microspheres (SA-CMS). The key functionalization step was performed in molten succinic anhydride without adding organic solvents. By adding a certain amount of succinic anhydride as a functionalization reagent to the reaction system, a large number of functional groups were generated on the surface of the glucose-based carbon microspheres (CMS), which improved their adsorption capacity and selectivity for the cationic dyes, methylene blue (MB) and methyl violet (MV). The maximum adsorption capacity Q_m of SA-CMS for MB and MV reached 571.43 mg g⁻¹ and 500.00 mg g⁻¹ at pH 8 and 25 °C, respectively, and the adsorption data of the cationic dyes by SA-CMS were in accordance with the Langmuir isotherm model and the pseudo-second-order model. SA-CMS demonstrated a stronger affinity for cationic dyes (500.00–571.43 mg g⁻¹) than for anionic dyes (44.38–118.33 mg g⁻¹), and the removal rates of MB and MV by SA-CMS remained above 75% after five adsorption–desorption cycles, confirming its highly selective separation ability and reusability. Systematic characterization revealed that the adsorption mechanisms of MB and MV by SA-CMS mainly included hydrogen bonding and electrostatic interactions. These results indicate that SA-CMS, a green carbon-based adsorbent material prepared by hydrothermal carbonization of glucose, is an environmentally friendly, low-cost, and effective adsorbent with high reusability, offering significant potential for removing cationic dyes from wastewater. Additionally, this adsorbent also exhibits an enhanced adsorption capacity with an increase in ionic strength, which is a systematically studied phenomenon. It is expected to be valuable in industrial wastewater treatment, with considerable economic and social benefits.