title: Degassing, gas retention and release in Fe(0) permeable reactive barriers.
abstract: Corrosion of Fe(0) has been successfully utilized for the reductive treatment of multiple contaminants. Under anaerobic conditions, concurrent corrosion leads to the generation of hydrogen and its liberation as a gas. Gas bubbles are mobile or trapped within the irregular pore structure leading to a reduction of the water filled pore volume and thus decreased residence time and permeability (gas clogging). With regard to the contaminant transport to the reactive site, the estimation of surface properties of the reactive material indicated that individual gas bubbles only occupied minor contact areas of the reactive surface. Quantification of gas entrapment by both gravimetrical and tracer investigations revealed that development of preferential flow paths was not significant. A novel continuous gravimetrical method was implemented to record variations in gas entrapment and gas bubble releases from the reactive filling. Variation of grain size fractions revealed that the pore geometry had a significant impact on gas release. Large pores led to the release of comparably large gas amounts while smaller volumes were released from finer pores with a higher frequency. Relevant processes are explained with a simplified pictorial sequence that incorporates relevant mechanisms.
authors.affiliation: Berlin Institute of Technology, Water Quality Control, Straße des 17. Juni 135, 10623 Berlin, Germany. Electronic address: aki.s.ruhl@tu-berlin.de.
authors.forename: Aki S
authors.initials: AS
authors.lastname: Ruhl
authors.affiliation: Berlin Institute of Technology, Water Quality Control, Straße des 17. Juni 135, 10623 Berlin, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Jekel
mesh_terms: D003343:Corrosion; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation; D005740:Gases / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D010539:Permeability; D014874:Water Pollutants, Chemical
chemical_list: D005740:Gases; D014874:Water Pollutants, Chemical; D006859:Hydrogen; D007501:Iron
keywords: Anaerobic corrosion; Degassing; Gas clogging; Hydrogen bubble; PRB; Permeable reactive barrier; Zero-valent iron