Reductive dechlorination of chlorinated ethenes by ball milled and mechanochemically sulfidated microscale zero valent iron: A comparative study

Ball milling is an effective technique to not only activate and reduce the size of commercial microscale zero valent iron (mZVI) but also to mechanochemically sulfidate mZVI. Yet, little is known about the difference between how chlorinated ethenes (CEs) interact with ball milled mZVI (mZVIbm) and mechanochemically sul-fidated mZVI (S-mZVIbm). We show that simple ball milling exposed the active Fe0 sites, while mechanochemical sulfidation diminished Fe0 sites and meanwhile increased S2-sites. Mechanochemical sulfidation with [S/Fe]dosed increased from 0 to 0.20 promoted the particle reactivity most for TCE dechlorination (-14-fold), followed by PCE and 1,1-DCE while it diminished the reactivity for trans-DCE (-0.4-fold), cis-DCE (-0.02-fold) and VC (-0.002-fold) compared to simple ball milling. Sulfidation also improved the electron efficiency of CE dechlo-rination, except for cis-DCE and VC. The kSA of cis-DCE, VC and trans-DCE dechlorination positively correlated

Automated summary

Ball milling is effective in activating and reducing the size of microscale zero valent iron (mZVI) and sulfidating mZVI mechanochemically. However, there are differences in the interaction between chlorinated ethenes (CEs) and ball milled mZVI (mZVIbm) and mechanochemically sulfidated mZVI (S-mZVIbm) that are not well understood. This study found that simple ball milling exposed active Fe0 sites, while mechanochemical sulfidation decreased Fe0 sites and increased S2 sites. The sulfidation process enhanced the reactivity of TCE dechlorination the most, followed by PCE and 1,1-DCE, but reduced the reactivity of trans-DCE, cis-DCE, and VC compared to simple ball milling. Sulfidation also improved the electron efficiency of CE dechlorination, except for cis-DCE and VC. The kSA of cis-DCE, VC, and trans-DCE dechlorination positively correlated with the sulfide content.