Hydrodechlorination of hexachlorobenzene in a miniaturized nano-Pd(0) reaction system combined with the simultaneous extraction of all dechlorination products

• Published in: Applied catalysis. B, Environmental Environmental, 2020-10, Vol.275, p.119100, Article 119100
• Main Authors: Wiltschka, Katrin, Neumann, Larissa, Werheid, Matthias, Bunge, Michael, Düring, Rolf-Alexander, Mackenzie, Katrin, Böhm, Leonard
• Format: Article
• Language: English
• Subjects: Benzene; Biodegradability; Biodegradation; Chlorine; Chlorobenzene; Chlorobenzenes; Dechlorination; Dehalogenation; Dichlorobenzene; Gas chromatography; Hexachlorobenzene; Hydrocarbons; Hydrodechlorination; Intermediates; Mass spectrometry; Mass spectroscopy; Nanomaterials; Nanoparticles; Nanotechnology; Palladium (Pd) nanoparticles; Pentachlorobenzene; Physicochemical properties; Pollutants; Solid phase methods; Solid phases; Solid-phase microextraction (SPME); Specific catalytic activity; Toxicity; Transformation products; Trichlorobenzene
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2020.119100

[Display omitted] •Miniaturized reactor system designed with simultaneous analyte extraction by SPME.•Pd(0) nanoparticles reduced HCB at environmental relevant concentrations.•Dechlorination pathways of all 12 chlorinated benzenes were elucidated.•Vicinal dechlorination pathway from hexachlorobenzene to benzene predominant. The persistent organic pollutant hexachlorobenzene (HCB) and all 11 further chlorobenzenes were hydrodechlorinated at environmentally relevant concentrations in miniaturized reaction systems, catalyzed by low concentrated Pd(0)-nanoparticles, to examine differences in dechlorination rates and pathways. Using solid-phase microextraction coupled to gas chromatography-mass spectrometry allowed the simultaneous extraction and detection of reactants, intermediate products and fully dechlorinated benzene, regardless of their different physicochemical properties. Dechlorination of HCB with formation of intermediates mainly proceeded via pentachlorobenzene, 1,2,3,4-tetrachlorobenzene, 1,2,3-trichlorobenzene, 1,2-dichlorobenzene, and monochlorobenzene to benzene. Specific catalytic activities of Pd(0)-nanoparticles (100–3400 L g−1 min−1) differed depending on chlorination degree of chlorobenzenes and position of chlorine atoms. An inductive effect is assumed to favor a removal of the vicinal chlorine atom. The presented method permits the facile determination and comparison of nanomaterials’ specific catalytic activities and allows the elucidation of dehalogenation pathways. It further enables to specifically examine formed intermediates to assess their toxicity and biodegradability.