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In order to deal with the increasingly serious water pollution caused by dye wastewater, a novel sulfonic acid-modified polyacrylamide magnetic composite (Fe 3 O 4 @SiO 2 /P(AM-AMPS)) was facilely prepared by crosslink reaction. The physicochemical properties and adsorption performances of Fe 3 O 4 @SiO 2 /P(AM-AMPS) were systematically studied by different characterization techniques and a series of batch experiments, respectively. It was found that the adsorption capacities of Fe 3 O 4 @SiO 2 /P(AM-AMPS) towards cationic dyes crystal violet (CV) and methylene blue (MB) were largely enhanced than those of silica-coated Fe 3 O 4 (Fe 3 O 4 @SiO 2) and maintained at relatively high levels in a wide pH range, due to the three-dimensional network structure and abundant functional groups of modified polyacrylamide. Besides, owing to the introduction of Fe 3 O 4 @SiO 2 , Fe 3 O 4 @SiO 2 /P(AM-AMPS) presented a unique magnetic property that helped it to be rapidly separated from water in a magnetic field. The maximum adsorption capacities of Fe 3 O 4 @SiO 2 /P(AM-AMPS) were 2106.37 mg g−1 for CV removal and 1462.34 mg g−1 for MB removal at 298.15 K, much higher than those of other reported magnetic composites. Furthermore, Fe 3 O 4 @SiO 2 /P(AM-AMPS) was effectively regenerated with HCl solution and the regeneration rates were higher than 97% and 80% for CV and MB removal after five adsorption-desorption cycles, respectively. With its excellent adsorption capacity, wide pH applicability, high separation speed, and satisfactory regeneration ability, Fe 3 O 4 @SiO 2 /P(AM-AMPS) was expected to become a promising adsorbent in the purification of cationic dye wastewater. Unlabelled Image • Novel PAM-based magnetic composite was facilely prepared by crosslink reaction. • Fe 3 O 4 @SiO 2 /P(AM-AMPS) presented a wide pH applicability for cationic dyes removal. • The maximum adsorption capacities were 2106 mg g−1 for CV and 1462 mg g−1 for MB. • The superior adsorption ability was attributed to multiple adsorption mechanisms. • Unique magnetism and good reusability facilitated its practical application. [ABSTRACT FROM AUTHOR]