FeN_X(C)-Coated Microscale Zero-Valent Iron for Fast and Stable Trichloroethylene Dechlorination in both Acidic and Basic pH Conditions

Abstract

FeN X in Fe single-atom catalysts can be the active site for adsorption and activation of reactants. In addition, FeN X species have been shown to facilitate electron transfer between Fe and the carbon supports used in newly developed metal−air batteries. We hypothesized that the combination of FeN X species with granular zero-valent iron (ZVI) might result in catalyzed reductive decontamination of groundwater contaminants such as trichloroethylene (TCE). Here, such materials synthesized by ball milling microscale ZVI with melamine and the resulting N species were mainly in the form of pyridinic, pyrrolic, and graphitic N. This new material (abbreviated as N−C-mZVI bm ) dechlorinated TCE at higher rates than bare mZVI bm (about 3.5-fold) due to facilitated electron transfer through (or around) the surface layer of iron oxides by the newly formed Fe−N X (C). N−C-mZVI bm gave higher k TCE (0.4−1.14 day −1 ) than mZVI bm (0−0.4 day −1 ) over a wide range of pH values (4− 11). Unlike most ZVI systems, k TCE for N−C-mZVI bm increased with increasing pH values. This is because the oxide layer that passivates Fe 0 at a high pH is disrupted by Fe−N X (C) formed on N−C-mZVI bm , thereby allowing TCE dechlorination and HER under basic conditions. Serial respike experiments gave no evidence of decreased performance of N−C-mZVI bm , showing that the advantages of this material might remain under field applications.

Coincorporation of N and S into Zero-Valent Iron to Enhance TCE Dechlorination: Kinetics, Electron Efficiency, and Dechlorination Capacity

“…Higher [S/Fe] (i.e., 0.1–0.2) reversed the trends of the SA and particle size simultaneously, likely because excessive S 0 with increased viscidity during ball-milling lowered the efficiency of particle crushing . Compared with S-mZVI bm ([S/Fe] = 0.1), SA and particle size of S-N­(C)-mZVI bm (with [S/Fe] = 0.1) were larger, likely caused by the melamine-assisted breakdown of the ZVI particles …”

“…To synthesize S-N­(C)-mZVI bm , ZVI, melamine and sulfur powder were mixed in a sealed jar under an argon (Ar) atmosphere, followed by ball-milling under anoxic conditions . The S/Fe molar ratio ([S/Fe]) was varied from 0.01 to 0.2, while the N/Fe molar ratio ([N/Fe]) was set at 0.05 unless otherwise noted, based on our previous work . The milling was carried out in a planetary ball mill (Boyuntong Instrument Technology, Nanjing, China) with stainless steel jars (100 mL) and 50 zirconia balls (6 mm in diameter).…”

“…Incorporation of heteroatoms (e.g., C, N, S, P) of differing electronegativity is an effective modification method that can tune the electronic structure of host materials (e.g., carbon or metal materials) by producing charge redistribution, and has been widely used in energy-related applications. − Recently, S, C, or N incorporation has also been extended to ZVI technology for groundwater remediation, including S-ZVI ,,− ,− and P-, , N-, and C , -modified ZVI (i.e., nitridation and carbonization, denoted as N-C-ZVI and C-ZVI). Despite these efforts, S-ZVI, N-C-ZVI, and C-ZVI particles require further improvement in terms of chemical composition and surface speciation to obtain higher reactivity and electron efficiency in CHC dechlorination. ,,− ,,,, It has been reported that introduction of S to Fe single-atom catalysts could induce uneven charge distribution in a carbon framework and affect the itinerant Fe d-electrons to favor adsorption of reactant species and improve electrocatalytic efficiency. − It is, therefore, expected that rational design of N/C/S-incorporated ZVI with an optimal chemical composition would further improve their reductive dechlorination reactivity and electron efficiency, and ultimately achieve longevity and successful application in the field.…”

Optimization of Dechlorination Experiment Design Using Lightweight Deep Learning Model

“…Layered bimetallic hydroxide is a kind of anionic clay with a layered structure. The calcined products of bimetallic hydroxides can reabsorb water and anions under certain conditions by using the structural memory effect to partially restore the layered structure of lactate dehydrogenase [ 29 ]. Layered double-layer hydroxide has a stable effect and high chloride ion removal efficiency, but chloride ions will be affected by the presence of other anions [ 30 , 31 ].…”

Designing an Electron-Deficient Pd/NiCo2O4 Bifunctional Electrocatalyst with an Enhanced Hydrodechlorination Activity to Reduce the Consumption of Pd

“…The excessive use of COCs has caused a number of serious environmental problems and its bioaccumulation and bioamplification through food webs are potentially toxic and dangerous to the natural environment and human health. , Reductive dechlorination is proposed as a promising method, which could remove chlorine atoms to potentially reduce the toxicity of COCs and produce chlorine-free organic compounds to be utilized as feedstocks in industries . Currently, the most widely applied reductive dechlorination approaches of COCs include the electrocatalytic hydrodechlorination (EHDC) treatment, − biological reductive dechlorination technology, − and zero-valence iron (ZVI) process. − In this work, EHDC treatment with advantages such as simple operation, mild reaction conditions, and no secondary pollution has been used in the reductive dechlorination of COCs.…”