Synthetic polymer-modified magnetically responsive biocomposites for the separation of cationic dye from wastewater

The presence of dye in wastewater has become a matter of concern around the globe. In this work, carboxyl-functionalized polymer-coated magnetic microcrystalline cellulose composites were synthesized for the removal of cationic dye from aqueous solution. First, microcrystalline jute cellulose (MCJC) was prepared from raw jute fiber by bleaching, delignification, and a hydrolysis process. MCJC/Fe₃O₄ biocomposites were prepared by the co-precipitation of Fe²⁺ and Fe³⁺ in the presence of MCJC followed by modification with copolymers of glycidyl methacrylate (GMA) and methacrylic acid (MAA), prepared by free radical copolymerization. The surface morphology of the final MCJC/Fe₃O₄/P(MAA-GMA) biocomposites analyzed by using Scanning Electron Microscopy (SEM) indicated an agglomerated spherical shape, while the characteristic rod-like structure of the MCJC disappeared after polymer modification. Energy Dispersive X-ray (EDX) spectra revealed the presence of a fair amount (32.82%) of Fe₃O₄ with polymer layers on the surface. The thermogravimetric analysis (TGA) demonstrated that approximately 32% of the composite weight remained at 800 °C, while the magnetization value of 4.3 emu g^-1, as revealed via Vibrating Sample Magnetometry (VSM), confirmed the magnetic properties of the MCJC/Fe₃O₄/P(MAA-GMA) composites.The survey spectrum from X-ray Photoelectron Spectroscopy (XPS) showed distinctive C 1s and O 1s peaks, which confirmed the successful coating of the composite particles with P(MAA-GMA). Also, the mesoporous structure of the composite particles was verified by Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) analysis. The final composites MCJC/Fe₃O₄/P(MAA-GMA) exhibited efficient adsorption of cationic methylene blue (MB) dye, with a maximum adsorption capacity of 181 mg g^-1 at pH 8. The equilibrium details are well described by Langmuir and Freundlich isotherm models, where the Langmuir isotherm with an R ² value of 0.9998 fitted the process better. The adsorption kinetics are best described by the pseudo-first-order model than a pseudo-second-order model. The composites also showed good recyclability and could be regenerated simply by washing with alcohol. These findings highlight the potential of biocomposites for wastewater treatment.