Insights into the Glyphosate Adsorption Behavior and Mechanism by a MnFe2O4@Cellulose-Activated Carbon Magnetic Hybrid

To enhance the removal of the negatively charged organophosphorus pesticide (OPP) glyphosate (GLY), we prepared a positively charged MnFe2O4@cellulose activated carbon (CAC) hybrid by immobilizing MnFe2O4 nanoparticles on the CAC surface via a simple one-pot solvothermal method, scanning electron microscopy, BET, transmission electron microscopy, IR, Raman, X-ray diffraction, and X-ray photoelectron spectroscopy analysis which proved the successful synthesis of MnFe2O4 with a particle size of 100-300 nm. The particles were distributed on the surface of CAC to form the MnFe2O4@CAC hybrid. MnFe2O4@CAC exhibited a positive charge at pH below 6 and had good magnetic properties and dispersion stability. The maximum GLY adsorption capacity of MnFe2O4@CAC (167.2 mg/g) was much higher than that of CAC (61.44 mg/g) and MnFe2O4 nanoparticles (93.48 mg/g). The adsorption process was dominated by chemisorption, and the formation of new chemical bonds between GLY and MnFe2O4 was confirmed by simulations. The newly formed chemical bonds were attributed to the conjugation between p electrons of the adsorbent and the d electrons of the adsorbate. Collectively, the results indicate that the as-prepared MnFe2O4@CAC is promising for anionic pollutant adsorption and the removal of OPPs, and our mechanistic results are of guiding significance in environmental cleanup.