Amino-functionalization is an effective and facile way to modify the surface of adsorbent. A facile strategy to fabricate polyethyleneimine-functionalized graphene aerogel (PFGA) integrating superhigh adsorption ability, selectivity, pH-sensitivity and reusability was developed. The maximum adsorption capacities of the PFGA for methyl orange and amaranth were as high as 3059.2 mg g (1) and 2043.7 mg g (1), respectively, the highest capabilities among the reported adsorbents for both dyes. The microcosmic interaction models of the two dyes and PFGA were outlined to describe the relationships between dye structures and adsorption behaviors. Owing to the different affinities of PFGA for anionic and cationic dye, anionic dye methyl orange was able to be selectively separated from the dye mixture. In the experiment of competitive adsorption of acid dyes with different structures, amaranth with more sulphonate groups was preferentially adsorbed. In addition, PFGA showed meaningful pH-sensitive adsorption ability, enabling dye-adsorbed PFGA to be fully regenerated as soon as it was exposed to the solution of pH 11. The study on polyethyleneimine-functionalization is meaningful for the development of high adsorption capacity adsorbents and amino-functionalization or other functionalized materials. (C) 2017 Elsevier B.V. All rights reserved.