Removal of methylene blue using trifunctional magnetic polyethersulfone microcapsule: process parameters and optimization study

Water pollution from dye-contaminated effluents poses a critical environmental threat. Current dye removal methods often rely on activated carbon, which is expensive and challenging to recover. This study focuses on the removal of methylene blue (MB), a cationic dye, using trifunctional polyethersulfone (PES)-encapsulated polydimethyldiallyl ammonium chloride-functionalized iron oxide (PDDA-Fe3O4) microcapsules with adsorptive, catalytic, and magnetic properties. The negatively charged PES facilitates MB adsorption through electrostatic interactions, while Fe3O4 enhances Fenton degradation and imparts magnetic responsiveness. Characterization techniques, including Fourier transform infrared spectroscopy and scanning electron microscopy with energy-dispersive X-ray analysis, confirmed the presence of PDDA-coated Fe3O4 and the formation of porous structures and finger-like cavities in the microcapsules. Process parameters such as microcapsule loading (10-30 g/L), MB concentration (10-50 ppm), pH (2-10), contact time (60-240 min), and H2O2 concentration (0.1-1 mol/L) were optimized using response surface methodology with a central composite design. Optimal conditions for MB removal (92.94%) were achieved with 21 g/L of microcapsules, 25 ppm of MB, pH 7, 127 minutes of contact time, and 0.45 mol/L of H2O2. These results demonstrate the efficacy of PDDA-Fe3O4@PES microcapsules for dye removal and suggest their potential for application in industries such as textiles and cosmetics, which generate high volumes of dye-contaminated wastewater.