N-doped magnetic carbon aerogel for the efficient adsorption of Congo red

•N-doped magnetic carbon aerogel (N-MCA) with high adsorption performance of 431 mg g−1 towards CR was synthesized by hydrothermal method.•Compared with MCA, the maximum adsorption capacity of CR on N-MCA can be increase 8.6 times.•Coexist dyes have almost no influence on the adsorption of CR on N-MCA, indicating high selectivity to CR.•N-MCA can be reused at least four times without obvious decrease of adsorption capacity of CR.