The　facile　synthesis　and　functionalization　of　graphene　quantum　dots　(GQDs)　have　shown　benefits　in　membrane　separation　processes　since　it　could　augment　their　performance.　Here,　the　fine-structure　characteristics　and　alcohol　dehydration　performance　of　a　polymeric　pervaporation　composite　membrane　integrated　with　either　nitrogen-doped　graphene　quantum　dots　(NGQDs)　or　oxygen-passivated　graphene　quantum　dots　(OGQDs)　were　evaluated.　Calcium　ion　cross-linked　sodium　alginate　(Alg)　was　used　as　the　polymer　matrix　since　the　multiple　hydroxyl　and　carboxyl　groups　could　form　hydrogen　bonds　with　GQDs.　The　interfacial　interaction　between　the　two　types　of　GQDs　and　Alg　was　evaluated　through　the　pervaporation　dehydration　of　isopropanol/water　(i-PrOH/water)　mixture　and　further　analyzed　using　positron　annihilation　lifetime　spectroscopy　(PALS).　The　PALS　results　revealed　that　different　functionalized　GQDs　affect　the　fine-structure　characteristics　of　Alg　matrix　and　resulted　to　different　alcohol　dehydration　performance.　In　dry　state,　both　NGQD　and　OGQD　integrated　membranes　have　smaller　free　volume　spaces　than　the　pristine　Alg　membrane　indicating　improved　interfacial　interaction　between　the　GQD　and　Alg.　However,　in　wet　state,　larger　free　volume　spaces　appeared　and　it　was　shown　that　OGQD　integrated　membranes　have　the　largest.　These　data　explained　the　higher　permeation　flux　and　separation　factor　of　Alg-OGQD　membranes　than　Alg-NGQD　and　Alg.　The　total　flux　reached　to　5580　g　m(-2)　h(-1)　with　a　water　concentration　in　permeate　of　similar　to　99.95%　in　dehydrating　i-PrOH/water　(70/30　wt%)　at　70　degrees　C　for　Alg-OGQD　membrane　with　100　ppm　of　OGQD　(Alg-OGQD100).　Furthermore,　the　membrane　remained　stable　for　720　h　of　operation　at　70　degrees　C　with　a　water　concentration　in　permeate　＞　99%　showing　potential　for　practical　applications.