Succinic Anhydride-Functionalized Corncob Biosorbent for Rapid and Selective Removal of Cationic Dyes from Water

Abstract

Selective adsorbents capable of efficiently removing cationic dyes from complex effluents are highly desirable for sustainable wastewater treatment and potential resource recovery. In this work, a low-cost corncob-derived biosorbent (CCP) was fabricated through alkaline activation/oxidation followed by succinic anhydride functionalization to enrich surface carboxyl groups. After modification, CCP exhibited a smaller particulate morphology with particle sizes mainly distributed in the range of 100-300 nm and abundant interparticle voids. FTIR spectra confirmed successful succinylation, while N2 adsorption-desorption analysis revealed a pronounced increase in specific surface area from 0.52 to 28.85 m2·g-1. Compared with the pristine corncob powder (CP), CCP showed a more negative zeta potential over pH 4.0-10.0, favoring the selective adsorption of cationic dyes. The maximum adsorption capacities of CCP toward methylene blue (MB) and methyl violet (MV), derived from the Langmuir model, reached 468.18 and 961.54 mg·g-1, respectively, and adsorption equilibrium was achieved within about 10 min. The adsorption kinetics were well described by the pseudo-second-order model. Thermodynamic analysis demonstrated that the adsorption of both dyes was spontaneous and endothermic, with ΔH° values of 10.72 kJ·mol-1 for MB and 46.72 kJ·mol-1 for MV, and ΔG° values ranging from -2.56 to -3.45 kJ·mol-1 for MB and from -6.11 to -9.65 kJ·mol-1 for MV over 298-318 K. In binary dye mixtures, CCP preferentially removed MB and MV over anionic dyes, and after six adsorption-desorption cycles, the adsorption capacities remained at approximately 346 mg·g-1 for MB and 680 mg·g-1 for MV. Moreover, mixed-dye adsorption, flash column, and real textile wastewater treatment experiments demonstrated that CCP not only exhibits excellent adsorption performance toward cationic dyes, but also holds strong potential for practical wastewater treatment applications. Spectroscopic and elemental analyses indicate that adsorption is mainly governed by electrostatic attraction, with additional contributions from hydrogen bonding. Overall, this work provides a simple, low-energy, and sustainable strategy for valorizing agricultural waste into a high-performance biosorbent for selective dye removal in complex wastewater systems.