Recyclable magnetic chitosan microspheres with good ability of removing cationic dyes from aqueous solutions

Sr_3.8Fe_25.7O_70.4-chitosan magnetic microparticles (Sr_3.8Fe_25.7O_70.4-CMNs) with a core-shell structure were synthesized, characterized and applied for the removal of two model cationic dyes. The results showed that these magnetic microparticles possess fast adsorption rate and high adsorption efficiency for both crystal violet (CV) and basic red 9 (BR9) at a temperature ranging 30 °C to 40 °C and suitable pH range (pH ≥ 7). The maximum removal efficiency for CV and BR9 attained to 94.5% and 97.5% in 30 min, which was significantly faster and higher than that of chitosan (<50% in 60 min) (P<0.01). And its maximum adsorption capacity for CV and BR9 reached 29.46 mg/g and 32.16 mg/g, respectively. The adsorption process of Sr_3.8Fe_25.7O_70.4-CMNs follows the Langmuir isotherm with a high correlation coefficient (R² > 0.97) and the pseudo-second-order model. Additionally, the synthesized Sr_3.8Fe_25.7O_70.4-CMNs were easy to regeneration and reuse, and the removal rate remained above 90% after 5 recycle times. This study would provide a new more environmental friendly material and method for the treatment of wastewater containing toxic dyes.