A novel nZVI–bentonite nanocomposite to remove trichloroethene (TCE) from solution. (November 2021)

• Record Type: Journal Article
• Authors: Baldermann, Andre; Kaufhold, Stephan; Dohrmann, Reiner; Baldermann, Claudia; Letofsky-Papst, Ilse; Dietzel, Martin
• Is Part Of: Chemosphere. Volume 282(2021)
• Publication Date: 2021-11
• Subjects: Chlorinated hydrocarbons -- Nanoscale zero valent iron -- Environmental pollution -- Groundwater -- Heavy metals -- Bentonite clay; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.131018
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Nanoscale zero-valent iron (nZVI) based (nano)composites supported by clay mineral substrates are a promising technology for the in-situ remediation of groundwater and (sub)soils contaminated with chlorinated hydrocarbons, such as trichloroethene (TCE). However, the physicochemical processes and interaction mechanisms between nZVI particles, clay minerals and TCE are poorly understood, yet. We immobilized nZVI particles on a commercial bentonite substrate to prepare a novel nZVI-B nanocomposite and tested its performance for TCE removal from solution against pure nZVI in batch reactors. The nZVI-B exhibited a higher reactivity (2.2·10 −3 L h −1 ·m −2 ) and efficiency (94%) for TCE removal than nZVI (2.2·10 −4 L h −1 ·m −2 ; 45%). Sorption of TCE onto the clay surfaces and reductive de-chlorination in "micro-reactors" developing within the nZVI-B controlled the kinetics and the magnitude of TCE loss from solution. Contrary to pure nZVI, no signs of nZVI particle agglomeration or inactivation due to oxide shell formation were found in nZVI-B. We attribute this to the uptake of dissolved Fe species that are liberated via progressing nZVI particle corrosion by the bentonite substrate to form Fe-smectite (nontronite domains), which prevented from a deterioration of the properties and reactivity of the nZVI-B. The use of nZVI-B in permeable reactive barriers at contaminated field sites could be feasible, where a system-inherent reduction of the soil-bearing capacity has to be minimized. Highlights: nZVI-B showed a better performance than pure nZVI for TCE removal from solution. TCE removal was due to reductive de-chlorination and sorption onto clay surfaces. Fe-smectite formed in "reactive micro-cells" and prevented from nZVI burn out. Fe uptake by clay substrate reduced iron oxide shell formation and nZVI passivation.