Mechanisms of 1,4-Dioxane Biodegradation and Adsorption by Bio-Zeolite in the Presence of Chlorinated Solvents: Experimental and Molecular Dynamics Simulation Studies

Abstract

The use of bioaugmented zeolite (bio-zeolite) can be an effective technology for irreversibly removing recalcitrant organic pollutants in aqueous mixtures. Removal of 1,4-dioxane by a bio-zeolite (Pseudonocardia dioxanivorans CB1190-bioaugmented ZSM-5) in the presence of several chlorinated volatile organic compounds (CVOCs) was superior to removal by adsorption using abiotic zeolite. Mixtures containing 1,1-dichloroethene (1,1-DCE) were an exception, which completely inhibited the bio-zeolite system. Specific adsorption characteristics were studied using adsorption isotherms in single-solute and bisolute systems accompanied by Polanyi theory-based Dubinin−Astakhov (DA) modeling. Adsorption behavior was examined using characteristic energy (E a/H ) from modified DA models and molecular dynamics simulations. While the tight-fit of 1,4-dioxane in the hydrophobic channels of ZSM-5 appears to drive 1,4dioxane adsorption, the greater hydrophobicity of trichloroethene and cis-1,2-dichloroethene cause them have a greater affinity over 1,4-dioxane for adsorption sites on the zeolite. 1,4-Dioxane was desorbed and displaced by CVOCs except 1,1-DCE because of its low E a/H value, explaining why bio-zeolite only biodegraded 1,4-dioxane in 1,1-DCE-free CVOC mixtures. Understanding the adsorption mechanisms of solutes in complex mixtures is crucial for the implementation of sorption-based treatment technologies for the removal of complex contaminant mixtures from aquatic environments.

Bioelectrochemical Treatment of 1,4-Dioxane in the Presence of Chlorinated Solvents: Design, Process, and Sustainability Considerations

“…1,1-DCE Inhibition and Removal. CVOCs often cooccur with 1,4-dioxane and inhibit its degradation; 4,31,46,49 therefore, it was critical to assess the fate and impact of 1,1-DCE in the column experiments. Figure 3 depicts 1,1-DCE normalized concentrations throughout the column reactors under the five experimental conditions tested.…”

“…PH-06, Pseudonocardia sp . ENV478, Methylosinus trichosporium OB3b, Mycobacterium austroafricanum JOB5, and Rhodococcus ruber ENV425. − However, in both metabolic and cometabolic degradations of 1,4-dioxane, it has been a challenge to reduce 1,4-dioxane concentrations to sub-ppb regulatory limits for in situ application of bioremediation either due to dependency on 1,4-dioxane as the only carbon source or lack of sufficient primary substrates. , Furthermore, it is well-documented that the presence of CVOCs significantly inhibits 1,4-dioxane-degrading microorganisms due to delayed ATP production as well as down-regulation of both 1,4-dioxane monooxygenase ( dxmB ) and aldehyde dehydrogenase ( aldH ) genes. , Consequently, the lack of oxygen and the presence of chlorinated co-contaminants limit the effectiveness of biodegradation as the sole water treatment strategy.…”

“…47,48 Furthermore, it is well-documented that the presence of CVOCs significantly inhibits 1,4-dioxanedegrading microorganisms due to delayed ATP production as well as down-regulation of both 1,4-dioxane monooxygenase (dxmB) and aldehyde dehydrogenase (aldH) genes. 46,49 Consequently, the lack of oxygen and the presence of chlorinated co-contaminants limit the effectiveness of biodegradation as the sole water treatment strategy.…”

“…As a model CVOC, we chose 1,1-DCE to challenge the process with worst-case conditions as 1,1-DCE has shown the highest inhibition effect on 1,4-dioxane biodegradation by CB1190. 46,49 Finally, we characterized the reactor effluent for disinfection byproducts (DBPs) and toxicity to obtain a holistic evaluation of bioelectrochemical oxidation systems as an effective treatment for 1,4-dioxanecontaminated water.…”

Non-Thermal Plasma-Modified Ru-Sn-Ti Catalyst for Chlorinated Volatile Organic Compound Degradation

“…It was shown that the specific surface area of the plasma-treated sample increased to 46.807 m 2 /g (37.397 m 2 /g with RST-C). The high specific surface area favored the exposure of more active sites to improve the catalytic activities of DCM oxidation [36][37][38][39]. It was proposed that the plasma preferred to discharge near the inner walls of pores [40,41], destroying the original pore structure and sequentially reconstructing it, resulting in the increase of specific surface area with almost the same total pore volume.…”