The　chiral　nematic　properties　of　carboxylatedcellulosenanocrystals　isolated　by　oxalic　acid　hydrolysis　were　investigatedsystematically,　aiming　to　achieve　sustainable　production　of　CNCs　foradvanced　applications.　Carboxylated　cellulose　nanocrystals　(OA-CNCs)　isolatedby　aqueousrecyclable　oxalic　acid　hydrolysis　from　degreasing　cotton　were　usedto　observe　its　self-assembly　behavior　and　chiral　nematic　properties.The　oxalic　acid　here　served　as　the　sole　catalyst　to　esterify　and　hydrolyzethe　degreasing　cotton.　The　results　indicated　that　the　obtained　OA-CNCsuspensions　were　spontaneously　phase-separated　into　a　chiral　nematicmesophase　above　a　critical　concentration,　and　the　occurrence　of　chiralself-assembly　is　highly　dependent　on　the　aspect　ratio　and　the　surfacecharge　of　the　OA-CNC　suspension.　Scanning　electron　microscopy　imagesof　the　cross　section　of　OA-CNC　solid　films　revealed　a　periodic　orderedmultilayer　structure.　The　residual　OA　was　easily　recovered　throughsimple　re-crystallization　method　after　reactions　with　a　high　recoveryrate　of　at　least　90%.　The　recycled　OA　(ROA)　had　excellent　performancein　terms　of　ROA-CNC　yield　even　after　reusing　for　five　cycles.　Moreover,the　resultant　ROA-CNCs　from　recycled　OA　could　also　form　chiral　nematicordered　phases　with　little　change　in　the　critical　concentration　andpitch,　suggesting　excellent　suitability　for　sustainable　OA-CNC　productionfor　photonics　and　other　specialty　applications.