Forward　osmosis　(FO)　has　demonstrated　its　merits　in　hybrid　FO　seawater　desalination.　However,　FO　may　have　a　potential　for　other　applications　if　suitable　draw　solutes　are　available.　In　this　study,　a　series　of　novel　draw　solutes　based　on　oxalic　acid　(OA)-transitional　metal　complexes　are　presented.　Influential　factors　of　FO　performance　have　been　systematically　investigated　by　varying　the　transitional　metals,　cations　of　the　complex　draw　solutes　as　well　as　the　experimental　conditions.　Compared　to　NaCl　and　other　recently　synthesized　draw　solutes,　the　OA　complexes　show　superior　FO　performance　in　terms　of　high　water　fluxes　up　to　27.5　and　89.1　LMH　under　the　respective　FO　and　PRO　(pressure　retarded　osmosis)　modes,　both　with　negligible　reverse　solute　fluxes.　The　features　of　octahedral　geometry,　abundant　hydrophilic　groups　and　ionic　species　are　crucial　for　the　OA　complexes　as　appropriate　draw　solutes　with　satisfactory　FO　performance.　Among　the　synthesized　OA　complexes,　the　ammonium　salt　of　chromic　complex　(NH4-Cr-OA)　outperforms　others　due　to　the　presence　of　more　ionic　species　in　its　complex　system.　NH4-Cr-OA　also　performs　better　than　the　typical　NaCl　draw　solute　in　FO　oily　wastewater　treatment　with　higher　water　recovery　and　negligible　reverse　fluxes.　Dilute　solutions　of　OA　complexes　have　been　reconcentrated　through　membrane　distillation　(MD)　and　reused　to　new　round　of　FO　processes.　The　OA　complexes　have　demonstrated　their　suitability　and　superiority　as　a　novel　class　of　draw　solutes　for　the　FO　process　in　this　study.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.