A　cellulose-based　bio-absorbent　with　various　and　plenty　of　amino　groups　was　successfully　prepared　from　corn　stalk　to　achieve　quantitative　removal　of　Congo　red　from　wastewater　with　wide　pH　values　(5　≤　pH　≤　10).　The　maximum　removal　amount　was　8.0　mmol·g−1　(5572　mg·g−1)　under　pH　=　6.0　and　45　°C,　which　was　obviously　higher　than　reported　absorbents.　Investigation　on　dynamic　adsorption　and　recyclability　in　authentic　wastewater　found　that　the　removal　efficiency　of　Congo　red　was　＞98　%　within　180　min　and　decreased　slightly　in　industrial　water　after　five　cycles,　denoting　this　adsorbent　with　great　potential　for　environmental　application.　The　characterization　results　proved　that　7.58　mmol·g−1　of　different　amino　groups　(-NH2,　-NH-　and　-NR2)　were　introduced　on　adsorbent　surface　by　two　steps　of　modification　and　were　the　major　functional　groups　for　adsorption　of　Congo　red.　The　inferred　adsorption　mechanism　revealed　that　Congo　red　could　be　adsorbed　equivalently　on　the　amino　groups　by　strong　electrostatic　interactions　or　hydrogen　bonds.　Different　amino　groups　played　different　roles　in　adsorption　due　to　great　differences　in　protonation　ability　in　5　≤　pH　≤　10.　The　study　was　expected　to　high-efficiently　remove　Congo　red　from　acidic　or　alkaline　wastewater,　and　offered　an　alternative　strategy　for　biowaste　treatment　of　corn　stalks　in　a　high　value-added　manner.　©　2023　Elsevier　B.V.