Metal–organic framework (MOF)-embedded magnetic polysaccharide hydrogel beads for rapid and selective adsorption of malachite green and crystal violet

Abstract

This study aims to tackle water pollution caused by toxic triphenylmethane dyes—specifically malachite green (MG) and crystal violet (CV)—by developing a metal–organic framework (MOF)-based magnetic hydrogel microsphere (MMOF) using sodium alginate as the matrix. Magnetic MOF particles were embedded into the sodium alginate hydrogel to form porous, stable magnetic microsphere adsorbents. Scanning electron microscopy confirmed their morphology and structural features, showing abundant active sites and well-defined adsorption channels. Under the optimized conditions, the adsorption rate of MMOF for MG reached 97.67%, and the adsorption equilibrium time was 50 minutes. The adsorption rate of MMOF for CV was 97.33%, and the adsorption equilibrium time was 60 minutes, with maximum adsorption capacities of 1008.6 mg g⁻¹ and 1100.1 mg g⁻¹, respectively, demonstrating outstanding dye removal ability. These magnetic microspheres also enabled rapid solid–liquid separation under an external magnetic field, supporting convenient operation and reusability. Overall, these composite microspheres represent a promising adsorbent for efficient removal of organic dye contaminants from aquatic product matrices, with strong potential for food safety applications.