Lei Sun, Min Liu, Zhou Wang
The synthesis of Cu x Mn (1−x) Fe 2 O 4 magnetic nanoparticles (MNPs) was carried out via self-propagating combustion process, their characterizations were performed using VSM, TEM, and XRD. To achieve an increased surface-to-mass ratio and optimal saturation magnetization for separation, the component ratio, calcination temperature and solvent dosage were optimized. For methyl blue (MB) removal, Cu 0.1 Mn 0.9 Fe 2 O 4 MNPs thermally processed at 400 °C for 2 h demonstrated a mean diameter of 16 ± 4 nm and saturation magnetization of 26.8 emu/g. MB adsorption mechanisms on Cu 0.1 Mn 0.9 Fe 2 O 4 MNPs were resolved via kinetic, isothermal and thermodynamic analyses. MB adsorption on Cu 0.1 Mn 0.9 Fe 2 O 4 MNPs was optimally modeled by pseudo-second-order kinetics and the Langmuir isotherm (R 2 > 0.98), capturing both the uptake dynamics and equilibrium state, signifying monolayer adsorption governed by chemisorption; while, thermodynamic statistical analysis confirmed endothermic MB adsorption on Cu 0.1 Mn 0.9 Fe 2 O 4 MNPs (ΔH° > 0) in the thermodynamic temperature range of 303–323 K, with elevated temperatures significantly enhancing removal efficiency due to favorable energetics. The positive correlation between pH elevation and adsorption capacity revealed pH-tunable adsorption characteristics. After 4 cycles, with 73.3% retention of initial adsorption capacity, Cu 0.1 Mn 0.9 Fe 2 O 4 MNPs demonstrated moderate cyclic stability and significant potential for dye removal applications.