Abstract
Environmentally acceptable lubricants (EALs) are increasingly being recognized in many fields including waterpower, hydraulics, water transport, agricultural machinery, offshore wind turbines, etc. Specifically, high-performance EALs are demanded for tidal turbomachinery to ensure high efficiency and reliability and avoid the significant risk of direct contamination of the marine ecosystem upon leaks. Here we report a new development of ionic liquid (IL)-enhanced EALs for tidal energy. One short-chain phosphonium phosphate and one short-chain ammonium phosphate ILs were used as the candidate additives and the IL-containing EALs demonstrated significantly improved lubricating performance, much lower toxicity, and increased biodegradability compared with commercial baselines. Specifically, in a rolling-sliding test simulating the operation of a model tidal turbine gearbox bearing, an EAL containing the ILs at a 0.5 wt % concentration demonstrated 40% lower friction, 45% less wear loss, substantially reduced rolling contact fatigue-induced surface damage, and one order of magnitude lower vibration noise compared with a commercial gear oil. In an EPA standard toxicity test, 90 and 70% survival of marine biota was observed when exposed to an EAL containing 5 wt % of the short-chain phosphonium phosphate and ammonium phosphate ILs, respectively, while the selected commercial gear oil and bioderived additive killed all marine biota. In a standard biodegradability test, 2 wt % addition of the phosphonium phosphate IL not only retained the EAL’s ready biodegradability but further boosted the oil decomposition from a range of 60-80% to a higher level of 80-95%. Conversely, adding the commercial bioderived additive downgraded the EAL from readily to inherently biodegradable. This work offers scientific insights for development of ILs as potential EAL additives for marine energy and broader applications.
| Original language | English |
|---|---|
| Pages (from-to) | 12482-12495 |
| Number of pages | 14 |
| Journal | ACS Sustainable Chemistry and Engineering |
| Volume | 13 |
| Issue number | 31 |
| DOIs | |
| State | Published - Aug 11 2025 |
Funding
The authors thank V. Neary from SNL and R. Cavagnaro from PNNL for providing the design information and operating parameters of the model tidal turbine gearbox, E. Conrad from Syensqo for providing the phosphonium cation feedstock, M. Woodfall, T. Thompson, and J. Holland from Biosynthetic Technologies for supplying the synthetic esters, L. Huffman from Dow Chemical for providing the PAG, and Y.F. Su from ORNL for assistance with the STEM/EDS data acquisition. Research was supported by the Water Power Technologies Office, Office of Energy Efficiency and Renewable Energy, U.S. Department of Energy (DOE). This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05- 00OR22725 with the U.S. Department of Energy (DOE). The U.S. government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. government purposes. The U.S. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan Access Plan ( http://energy.gov/downloads/doe-public-access-plan ).
Keywords
- additives
- biodegradability
- environmentally acceptable lubricants (EALs)
- ionic liquids
- marine toxicity