A Synergistic Platform for Continuous Co-removal of 1,1,1-Trichloroethane, Trichloroethene, and 1,4-Dioxane via Catalytic Dechlorination Followed by Biodegradation

Abstract

Groundwater co-contaminated with 1,4-dioxane, 1,1,1-trichloroethane (TCA), and trichloroethene (TCE) is among the most urgent environmental concerns of the U.S. Department of Defense (DoD), U.S. Environmental Protection Agency (EPA), and industries related to chlorinated solvents. Inspired by the pressing need to remove all three contaminants at many sites, we tested a synergistic platform: catalytic reduction of 1,1,1-TCA and TCE to ethane in a H2-based membrane palladium-film reactor (H2-MPfR), followed by aerobic biodegradation of ethane and 1,4-dioxane in an O2-based membrane biofilm reactor (O2-MBfR). During 130 days of continuous operation, 1,1,1-TCA and TCE were 95–98% reductively dechlorinated to ethane in the H2-MPfR, and ethane served as the endogenous primary electron donor for promoting 98.5% aerobic biodegradation of 1,4-dioxane in the O2-MBfR. In addition, the small concentrations of the chlorinated intermediate from the H2-MPfR, dichloroethane (DCA) and monochloroethane (MCA), were fully biodegraded through aerobic biodegradation in the O2-MBfR. The biofilms in the O2-MBfR were enriched in phylotypes closely related to the genera Pseudonocardia known to biodegrade 1,4-dioxane.

Hydrodehalogenation of Trichlorofluoromethane over Biogenic Palladium Nanoparticles in Ambient Conditions

“…Since O 2 was rapidly reduced by H 2 with Pd 0 NPs as the catalyst, O 2 at relevant concentrations did not inhibit dehalogenation by competing for H 2 , and, because of the high H 2 /O 2 molar ratio (>30:1), competition of H* between CFC-11 and O 2 was negligible. Further evidence supporting a lack of impact comes from a continuous study in which dissolved O 2 ∼ 8 mg/L did not affect TCE, TCA, or chlorophenol halogenation catalyzed by Pd 0 NPs in continuous operation. , …”

“…Further evidence supporting a lack of impact comes from a continuous study in which dissolved O 2 ∼ 8 mg/L did not affect TCE, TCA, or chlorophenol halogenation catalyzed by Pd 0 NPs in continuous operation. 38,75 An H* Scavenger Significantly Inhibited Dehalogenation of CFC-11. tert-Butanol is widely used as a scavenger of reactive H* on catalyst surfaces.…”

Molybdenum-Catalyzed Perchlorate Reduction: Robustness, Challenges, and Solutions

“…If the treated brine is recycled for resin regeneration, further studies are warranted to evaluate the potential transfer of leached Mo from waste brine treatment to drinking water. Second, the use of H 2 gas for reductive pollutant degradation has been widely adopted in environmental engineering projects. − Third, inorganic sulfide, a potent Pd poison that may be present in the wastes, can be instantly oxidized into inert SO 4 2– using common oxidants to avoid catalyst fouling. Fourth, although dissolved organics might not be significant constituents in the waste brine, our data show that 10–50 mg/L of humic acid did not inhibit the ( L )­Mo–Pd/C catalyst (Figure d).…”

Modification of Pd Nanoparticles with Lower Work Function Elements for Enhanced Formic Acid Dehydrogenation and Trichloroethylene Dechlorination

“…Catalytic reduction of organic and inorganic contaminants via heterogeneous catalysts has been widely studied as a promising technology for environmental remediation. − Pd is one of the most frequently used catalysts that can induce the H 2 dissociation to form active atom H for the hydrogenolysis of halogenated contaminants. − However, the storage, transportation, and utilization of H 2 remain challenging, as well as the easy poisoning of Pd catalyst, − restricting the applications of this technology for efficiency and selective dehalogenation.…”