Herein,　an　emerging　vertically　oriented　alginate　aerogel　composites　(QLHC@A　aerogel)　was　constructed　by　combining　the　mild　ionic　crosslinking　technique　with　directed　freeze-casting　to　achieve　adsorptive　removal　of　ReO4−　(the　chemical　analogue　of　TcO4−).　The　lignin　hydrochar　in　aerogel　composites　served　as　a　bridge　connecting　quaternary　ammonium　groups　to　fabricate　functional　addition,　among　the　PDDA-modified　lignin　hydrochar　investigated,　QLHC100　exhibited　the　best　adsorption　performance,　up　to　212.95　mg/g,　while　the　regular　lamellar　structure　and　good　hydrophilic　property　of　alginate-based　aerogel　allowed　rapid　diffusion　of　ReO4−　anion　in　water.　When　the　usage　amount　of　QLHC100　powder　became　0.8　g,　the　optimal　ReO4−　removal　efficiency　of　QLHC@A　aerogel　reached　188.90　mg/g　at　pH　4,　0.1　g/L　and　303　K.　Batch　adsorption　experiments　also　validate　that　the　ReO4−　adsorption　process　was　mightily　pH-dependent　behavior,　and　adsorption　behavior　fitted　both　the　pseudo-second-order　kinetic　model　and　the　Langmuir　isothermal　model　well.　Meanwhile,　QLHC@A　aerogel　had　a　high　adsorption　selectivity,　excellent　chemical　tolerance,　and　good　reuse　performance.　Based　on　various　characterization　techniques　and　DFT　calculation　result,　the　adsorption　mechanism　of　ReO4−　on　QLHC@A　aerogel　is　mainly　dominated　by　electrostatic　adsorption　and　strong　affinity　between　quaternary　ammonium　groups　and　ReO4−.　Significantly,　this　strategy　can　be　expanded　to　include　high-performance　aerogel　composites　for　the　remediation　of　nuclear　effluent　contaminated　with　TcO4−.　©　2025　Elsevier　B.V.