Effect of sulfidation on nitrobenzene removal from groundwater by microscale zero-valent iron: Insights into reactivity, reaction sites and removal pathways.

While it has been recognized that sulfidation can effectively improve the reactivity of microscale zero valent iron (mZVI), there is limited understanding of nitrobenzene (ArNO2) removal by sulfidated mZVI. To understand the reduction capacity and pathway of ArNO2 by sulfidated mZVI, ball-milling sulfidated mZVI (S-mZVIbm) with different S/Fe molar ratios (0-0.2) was used to conduct this experiment. The results showed that sulfidation could efficiently enhance ArNO2 removal under iron-limited and iron excess conditions, which was attributed to the presence of FeSx sites that could provide higher Fe(0) utilization efficiency and stronger passivation resisting for S-mZVIbm. The optimum ArNO2 reduction could be obtained by S-mZVIbm with S/Fe molar ratio at 0.1, which could completely transform ArNO2 to aniline (ArNH2) with a rate constant of 4.36 × 10-2 min-1 during 120-min reaction. FeSx phase could act as electron transfer sites for ArNO2 reduction and it could still be reserved in S-mZVIbm after reduction reaction. The product distribution indicated that sulfidation did not change the types of reduction products, while the removal of ArNO2 by S-mZVIbm was a step-by-step reduction progress along with the adsorption of ArNH2. In addition, a faster reduction of ArNO2 in groundwater/soil system further demonstrated the feasibility of S-mZVIbm in the real field remediation.

Enhanced dechlorination of trichloroethene by sulfidated microscale zero-valent iron under low-frequency AC electromagnetic field.

In this study an electromagnetic heating strategy is proposed for remediation of trichloroethene (TCE) by ball milled, sulfidated microscale zero valent iron (S-mZVIbm) particles. S-mZVIbm is ferromagnetic, which generates heat under the application of a low-frequency alternating current electromagnetic field (AC EMF). We found that the temperature reached up to ~120 â„ƒ during 30-min electromagnetic induction heating of 10 g/L S-mZVIbm (with S/Fe molar ratio of 0.1), compared with ~55 â„ƒ and ~80 â„ƒ for ZVI and ball milled mZVIbm, respectively. The application of AC EMF accelerated the TCE degradation rate (kTCE = 5.5 × 10-1 h-1) by up to 4-fold without compromising or even enhancing electron efficiency of S-mZVIbm compared to no-heating. Furthermore, this process halved the generation of chlorinated intermediate, cis-DCE. In contrast, water-bath heating only increased the dechlorination rate 2-fold with unchanged cis-DCE generation and lowered electron efficiency. This is attributed to both rising temperature by induction heating and accelerated ZVI corrosion and surface Fe0 exposure caused by AC EMF. In real groundwater, the AC EMF maintained the same promoting effects for TCE dechlorination by S-mZVIbm. This study shows that combination of filed-scale available AC EMF with S-mZVIbm provides a promising approach for remediation of chlorinated hydrocarbons in contaminated groundwater.

Multifunctional nitrogen-doped graphene nanoribbon aerogels for superior lithium storage and cell culture.

Nitrogen-doped graphene nanoribbon aerogels (N-GNRAs) are fabricated through the self-assembly of graphene oxide nanoribbons (GONRs) combined with a thermal annealing process. Amino-groups are grafted to the surface of graphene nanoribbons (GNRs) by an epoxy ring-opening reaction. High nitrogen doping level (7.6 atm% as confirmed by elemental analysis) is achieved during thermal treatment resulting from functionalization and the rich edge structures of GNRs. The three dimensional (3D) N-GNRAs feature a hierarchical porous structure. The quasi-one dimensional (1D) GNRs act as the building blocks for the construction of fishnet-like GNR sheets, which further create 3D frameworks with micrometer-scale pores. The edge effect of GNRs combined with nitrogen doping and porosity give rise to good electrical conductivity, superhydrophilic, highly compressible and low density GNRAs. As a result, a high capacity of 910 mA h g(-1) is achieved at a current density of 0.5 A g(-1) when they are tested as anode materials for lithium ion batteries. Further cell culture experiments with the GNRAs as human medulloblastoma DAOY cell scaffolds demonstrate their good biocompatibility, inferring potential applications in the biomedical field.