A　novel　thiol-functionalized　graphene　oxide/Fe-Mn　composite　(SGO/Fe-Mn)　was　synthesized　via　three　different　methods,　i.e.,　acetic　acid　method　(SGO/Fe-Mn-ac),　neutral　method　(SGO/Fe-Mn-ne),　and　ammonium　hydroxide　method　(SGO/Fe-Mn-am).　The　composites　were　characterized　and　tested　for　aqueous　methylmercury　removal.　SGO/Fe-Mn　was　prepared　using　3-mercaptopropyltrimethoxysilane　(3-MPTS)　as　a　silanizing　reagent,　and　hydrolyzed　3-MPTS　mainly　interacted　with　GO/Fe-Mn　through　surface　oxygen-containing　groups　(i.e.,　OH,　C=O,　epoxy　C-O-C,　carboxyl　O=C-O,　and　C-O)　and　pi-pi　interactions,　partially　through　self-polymerization.　SGO/Fe-Mn-am　showed　the　largest　hydrodynamic　diameter,　strongest　pi-pi　bond,　fewest　S　oxidation　products,　most　thiol　groups,　negative　charge,　spa　defects,　and　FeOOH.　Pseudo-second-order　kinetic　model　and　Langmuir　and　Freundlich　isotherm　models　fitted　well　with　methylmercury　sorption　kinetic　and　isotherm　data,　respectively,　resulting　in　a　CH3Hg+　maximum　sorption　capacity　of　43.88　mg/g　for　SGO/Fe-Mn-am,　36.33　mg/g　for　SGO/Fe-Mn-ac,　and　28.00　mg/g　for　SGO/Fe-Mn-ne.　The　removal　mechanism　was　described　by　electrostatic　attraction,　ligand　exchange,　and　surface　complexation.　This　study　demonstrates　potential　and　viability　of　SGO/Fe-Mn　for　enhanced　immobilization　of　CH3Hg+　in　surface　water,　groundwater,　and　soil/sediments.　(C)　2017　Elsevier　B.V.　All　rights　reserved.