Abstract <p>To effectively remove dyes from wastewater, carboxyl-functionalized and amine-functionalized Fe₃O₄ magnetic nanoparticles were synthesized by hydrothermal method and co-precipitation method, respectively, then coated with BSA through reverse emulsion. Their difference in morphology and structure of different functionalized magnetic nanoparticles are recognizable by X-ray diffraction, Fourier transform infrared (FT-IR) and scanning electron microscope (SEM). And their thermal stability and magnetic properties were examined through thermogravimetric analysis (TGA) and magnetic hysteresis curves. In addition, their dye removal behavior was examined. Results demonstrated that the composite particles have a good removal effect on Congo red and Alizarin red. The experimental maximum adsorption capacity of composite particles BSA-coated carboxyl-functionalized Fe₃O₄ for Congo red and Alizarin red is 546.914 and 89.25 mg/g, respectively. The maximum adsorption capacity of BSA-coated amine-functionalized Fe₃O₄ is 486.25 and 71.34 mg/g, respectively. Both the adsorption processes of dyes on the composite particles fitted well with the pseudo-second-order kinetic model. Their adsorption isotherm were more in line with the Langmuir model than the Freundlich model. It was inferred that the adsorption process was spontaneous adsorption from the values of the thermodynamic parameters of the reaction between dyes and composite particles. The two types of composite particles show potential applications in the removal of dyes from wastewater. This expands their application fields, as previously only the use of such BSA/Fe₃O₄ composite particles for treating heavy metals in wastewater had been reported.</p>