155. C.D. Powell, S. Guo, L.M. Godret-Miertschin, K. Ventura, A.W. Lounsbury, C.A. Clark, D. Villagrán, J.B. Zimmerman, A.J. Atkinson, P. Westerhoff, and M.S. Wong "Magnetically recoverable carbon-coated iron carbide with arsenic adsorptive removal properties" SN Applied Sciences 2, 1690 (2020) DOI: 10.1007/s42452-020-03491-7
Magnetic particles, generally nanostructured and magnetite-based, have been studied extensively to remove drinking water contaminants. Compositions beyond Fe3O4 could address long-standing issues of magnetic recoverability and materials integrity in drinking waters. Herein carbon-coated iron carbide (Fe3C@C) were studied for the first time for their stability, magnetic characteristics, magnetic separability, and arsenic adsorptive properties. Experimental results show that (i) Fe3C@C with a 9-nm thick graphitic shell is chemically stable in simulated drinking water; (ii) is ferromagnetic with small magnetic remanence and a magnetic saturation that is ~2× greater than Fe3O4; (iii) can be separated from water magnetically under continuous-flow conditions with greater than 99% recovery; and (iv) has a surface area-normalized adsorption capacity for arsenic (6.75 µg/m2) of the same order of magnitude as that of Fe3O4 (9.62 µg/m2). Fe3C@C can be a viable alternative to Fe3O4 with further development, for the magnetic removal of arsenic and other contaminants from drinking water sources.
Magnetic catalysts offer the possibility of rapidly eliminating nitrate oxyanions, a ubiquitous drinking water contaminant, without generating a secondary waste stream. Herein, we report the synthesis of a magnetically recoverable bimetallic Pd–In material that exhibits excellent chemical stability, reusability, and high nitrate removal efficiency. This four-component catalyst (Pd–In/nFe3O4@SiO2) contains nanocrystalline magnetite with a silica shell upon which indium-decorated palladium nanoparticles attach. The SiO2 shell slowed down iron leaching from Fe3O4 and the bimetallic nano-domains showed nitrate reduction activity in deionized water without obvious deactivation through multiple recovery and reuse cycles. This magnetically responsive, reusable catalyst, which retained activity in simulated drinking water, can serve as a design basis for materials to degrade other oxyanion water contaminants.
153. T.K. Rogers, P.D. Dongare, A. Alabastri, N.J. Halas, J. Metz, J. Mathieu, P.J.J. Alvarez, L. Carter, M.S. Wong, and R. Verduzco "Nanotechnology for Beyond Earth Water Treatment" International Conference on Environmental Systems (2020) Conference Collection
NASA has embarked on a journey to enable human exploration on the Moon and Mars by 2024. These long duration missions beyond low earth orbit (LEO) will require advanced water treatment and reuse technologies for life support systems to support crew and system needs. Resupply to deep space destinations is not desirable and sustained human presence in a lunar environment increases the necessity for robust and reliable systems. To reduce propulsion costs and transit space allocations, mass, power consumption, and volume must be minimized for all systems. Additionally, a beyond (LEO) water treatment system process must be able to tolerate both operational and dormant periods. Herein, we present nanotechnologies developed by the Nanotechnology-Enabled Water Treatment (NEWT) center as advanced solutions to meet the aforementioned requirements. This survey of fit-for-purpose modular technologies includes room temperature nanocatalysis, nanophotonics, nano-selective scalant control, quorum sensing and biofouling control techniques, and nano enabled fluid management. A case study of integrating nanotechnology into state-of-the-art and developing systems is also presented.
152. H. Javed, J. Metz, T.C. Eraslan, J. Mathieu, B. Wang, G. Wu, A. Tsai, M.S. Wong, and P.J.J. Alvarez "Discerning the Relevance of Superoxide in PFOA Degradation" Environmental Science & Technology Letters 7, 9, 653 - 658 (2020) DOI: 10.1021/acs.estlett.0c0505
Perfluorooctanoic acid (PFOA) is a widely distributed recalcitrant contaminant. In recent years, advanced oxidation processes have been explored for PFOA degradation, yet factors influencing their efficacy and degradation mechanism are not fully understood. Here, we resolve ambiguity in the literature regarding the role of superoxide in PFOA degradation (e.g., by nucleophilic attack) by considering three pure superoxide-producing systems: KO2 in dimethyl sulfoxide, xanthine oxidase with hypoxanthine, and WOx/ZrO2 catalyst with H2O2. Superoxide production was confirmed in all systems by electron paramagnetic resonance spectroscopy and by precipitation of nitroblue tetrazolium, a common superoxide probe. Positive control experiments showed that the produced superoxide degrades ~48% of bisphenol A within 1 day, corroborating the fact that superoxide was sufficiently stable and available for reaction in the test systems. However, no PFOA degradation was observed, which was c