Journal
ENVIRONMENTAL SCIENCE & TECHNOLOGY
Volume -, Issue -, Pages -Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.est.2c07317
Keywords
membrane catalyst reactor; halogenated herbicides; hydrodechlorination; hydrosaturation; hydrolysis
Categories
Funding
- U.S. Department of Defense (DOD) Strategic Environmental Research and Development Program (SERDP) [ER-2721]
- National Science Foundation [EEC-1449500]
- Nanosystems Engineering Research Center on Nanotechnology-Enabled Water Treatment
- Nanotechnology Collaborative Infrastructure Southwest [NNCI-ECCS-1542160]
- National Natural Science Foundation of China [52200087]
- China Postdoctoral Science Foundation [2022 M710654]
- Fundamental Research Funds for the Central Universities [2412022QD019]
- generous donations from the Swette Family Endowment and ASU's Fulton Chair of Environmental Engineering
- China Scholarship Council
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More food production requires intensive use of herbicides, but the widespread application and persistence of herbicides pose environmental risks. This study demonstrates that palladium nanoparticles can catalyze the reductive dehalogenation of halogenated organic pollutants, including herbicides. The findings suggest a promising method for the removal and detoxification of halogenated herbicides in aqueous environments.
More food production required to feed humans will require intensive use of herbicides to protect against weeds. The widespread application and persistence of herbicides pose environmental risks for nontarget species. Elemental palladium nanoparticles (Pd0NPs) are known to catalyze reductive dehalogenation of halogenated organic pollutants. In this study, the reductive conversion of 2,4dichlorophenoxyacetic acid (2,4-D) was evaluated in a H2-based membrane catalyst film reactor (H2-MCfR), in which Pd0NPs were in situ-synthesized as the catalyst film and used to activate H2 on the surface of H2-delivery membranes. Batch kinetic experiments showed that 99% of 2,4-D was removed and converted to phenoxyacetic acid (POA) within 90 min with a Pd0 surface loading of 20 mg Pd/m2, achieving a catalyst specific activity of 6.6 +/- 0.5 L/g-Pd-min. Continuous operation of the H2-MCfR loaded with 20 mg Pd/m2 sustained >99% removal of 50 mu M 2,4-D for 20 days. A higher Pd0 surface loading, 1030 mg Pd/m2, also enabled hydrosaturation and hydrolysis of POA to cyclohexanone and glycolic acid. Density functional theory identified the reaction mechanisms and pathways, which involved reductive hydrodechlorination, hydrosaturation, and hydrolysis. Molecular electrostatic potential calculations and Fukui indices suggested that reductive dehalogenation could increase the bioavailability of herbicides. Furthermore, three other halogenated herbicides-atrazine, dicamba, and bromoxynil- were reductively dehalogenated in the H2-MCfR. This study documents a promising method for the removal and detoxification of halogenated herbicides in aqueous environments.
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