Forward osmosis for oily wastewater reclamation: Multi-charged oxalic acid complexes as draw solutes

Qingchun Ge, Gary L. Amy, Neal Tai-Shung Chung

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44 Scopus citations


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.
Original languageEnglish (US)
Pages (from-to)580-590
Number of pages11
JournalWater Research
StatePublished - Jun 11 2017

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: This research is supported by both the National Research Foundation- Prime Minister's office, Republic of Singapore under its Competitive Research Program entitled “Advanced FO Membranes and Membrane Systems for Wastewater Treatment, Water Reuse and Seawater Desalination” (Grant numbers: R-279-000-336-281 & R-279-000-339-281), and the financial supports from the National Natural Science Foundation of China (grant number: 21677035), the Natural Science Foundation of Fujian Province (grant number: 2016J01056) and Fuzhou University (grant number: XRC-1259).


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