Minor chromium passivation of S-ZVI enhanced the long-term dechlorination performance of trichlorethylene: Effects of corrosion and passivation on the reactivity and selectivity.

The corrosion and surface passivation of sulfidized zero-valent iron (S-ZVI) by common groundwater ions and contaminants are considered to be the most challenging aspects in the application of S-ZVI for remediation of chlorinated contaminants. This study investigated the impacts of corrosive chloride (Cl-) and passivation of hexavalent chromium (Cr(VI)) on the long-term reactivity, selectivity, corrosion behavior, and physicochemical properties during the 60-day aging process of S-ZVI. Although the co-existing of Cl- promoted the initial reactivity of S-ZVI, the rapid consumption of Fe° content shortened the reactive lifetime owing to the insufficient electron capacity. Severe passivation by Cr(VI) (30 mg L-1) preserved the Fe° content but significantly interfered with the reductive sulfur species, resulting in an increase in electron transfer resistance. In comparison, minor passivated S-ZVI (5.0 mg L-1 Cr(VI)) inhibited the hydrogen evolution while concurrently mitigating the further oxidation of the reductive iron and sulfur species, which significantly enhanced the long-term reactivity and selectivity of S-ZVI. Furthermore, the enhancement effect of minor passivation could be detected in the aging processes of one-step, two-step, and mechanochemically synthesized S-ZVI particles with different S/Fe ratios and precursors, which further verified the advantages of minor passivation. This observation is inspirable for the development of innovative strategies for environmental remediation by S-ZVI-based materials.

Tetrabromobisphenol A transformation by biochar supported post-sulfidated nanoscale zero-valent iron: Mechanistic insights from shell control and solvent kinetic isotope effects.

Post-sulfidated nanoscale zero-valent iron with a controlled FeSX shell thickness deposited on biochar (S-nZVI/BC) was synthesized to degrade tetrabromobisphenol A (TBBPA). Detailed characterizations revealed that the increasing sulfidation degree altered shell thickness/morphology, S content/speciation/distribution, hydrophobicity, and electron transfer capacity. Meanwhile, the BC improved electron transfer capacity and hydrophobicity and inhibited the surface oxidation of S-nZVI. These properties endowed S-nZVI/BC with highly reactive (∼8.9-13.2 times) and selective (∼58.4-228.9 times) over nZVI/BC in TBBPA transformation. BC modification improved the reactivity and selectivity of S-nZVI by 1.77 and 1.96 times, respectively. The difference of S-nZVI/BC in reactivity was related to hydrophobicity and electron transfer, particularly FeSX shell thickness and morphology. Optimal shell thickness of ∼32 nm allowed the maximum association between Fe0 core and exterior FeSX, resulting in superior reactivity. A thicker shell with abundant networks increased the roughness but decreased the surface area and electron transfer. The higher [S/Fe]surface and [S/Fe]particle were conducive to the selectivity, and [S/Fe]particle was more influential than [S/Fe]surface on selectivity upon similar hydrophobicity. The solvent kinetic isotope effects (SKIEs) exhibited that increasing [S/Fe]dose tuned the relative contributions of atomic H and electron in TBBPA debromination but failed to alter the dominant debromination pathway (i.e., direct electron transfer) in (S)-nZVI/BC systems. Mechanism of electron transfer rather than atomic H contributed to higher selectivity. This work demonstrated that S-nZVI/BC was a prospective material for the remediation of TBBPA-contaminated groundwater.

Chiral Ionic Covalent Organic Framework as an Enantioselective Fluorescent Sensor for Phenylalaninol Determination.

Phenylalaninol (PAL) is a significant chemical intermediate widely utilized in drug development and chiral synthesis, for instance, as a reactant for bicyclic lactams and oxazoloisoindolinones. Since the absolute stereochemical configuration significantly impacts biological action, it is crucial to evaluate the concentration and enantiomeric content of PAL in a quick and convenient manner. Herein, an effective PAL enantiomer recognition method was reported based on a chiral ionic covalent organic framework (COF) fluorescent sensor, which was fabricated via one-step postquaternization modification of an achiral COF by (1R, 2S, 5R)-2-isopropyl-5-methylcyclohexyl-carbonochloridate (L-MTE). The formed chiral L-TB-COF can be applied as a chiral fluorescent sensor to recognize the stereochemical configuration of PAL, which displayed a turn-on fluorescent response for R-PAL over that of S-PAL with an enantioselectivity factor of 16.96. Nonetheless, the single L-MTE molecule had no chiral recognition ability for PAL. Moreover, the ee value of PAL can be identified by L-TB-COF. Furthermore, density functional theory (DFT) calculations demonstrated that the chiral selectivity came from the stronger binding affinity between L-TB-COF and R-PAL in comparison to that with S-PAL. L-TB-COF is the first chiral ionic COF employed to identify chiral isomers by fluorescence. The current work expands the range of applications for ionic COFs and offers fresh suggestions for creating novel chiral fluorescent sensors.

The Effects of Dandelion Polysaccharides on Iron Metabolism by Regulating Hepcidin via JAK/STAT Signaling Pathway.

Recent studies have claimed that iron overload was correlated with the risk of hepatocellular carcinoma (HCC), and our previous studies have also demonstrated that dandelion polysaccharide (DP) suppressed HCC cell line proliferation via causing cell cycle arrest and inhibiting the PI3K/AKT/mTOR pathway, but the effect of DP on metabolism is still not very clear. Here, we aim to clarify the effects of DP on iron metabolism and the underlying mechanism. In this study, we found that DP could reduce iron burden in hepatoma cells and grafted tumors. Hepcidin is a central regulator in iron metabolism. We confirmed that the expression of hepcidin in HCC tumor tissues was significantly higher than that in the adjacent nontumor tissues. The expression of hepcidin was downregulated in the liver of mouse model treatment with DP, as well as in hepatoma cells. Moreover, RNA sequencing and western blot data revealed that DP inhibited the IL-6-activated JAK-STAT signaling pathway. In summary, our results revealed that DP might be a new potential drug candidate for the regulation of iron burden and the treatment of HCC.

Enhanced two-phase anaerobic digestion of waste-activated sludge by combining magnetite and zero-valent iron.

Previous studies have found that magnetite can promote the hydrolysis-acidification but inhibit the methanogenesis, while zero-valent iron (ZVI) only promoted the methanogenesis. Therefore, a new two-phase anaerobic digestion model, in which magnetite was added to the first phase, and ZVI was added to the second phase, was proposed to promote both hydrolysis-acidification and methanogenesis and avoid magnetite inhibition. The results showed that in the new model, methane production was improved by 10.2% and 18.1% and chemical oxygen demand (COD) removal was improved by 7.9% and 10.9% compared with reactors that included only magnetite and only ZVI, respectively. In the new model reactors, inhibition of methanogenesis by magnetite was avoided compared with that of the magnetite-only reactors, and hydrolysis efficiency was improved via dissimilatory iron reduction (DIR) compared with that of ZVI-only reactors. The data on volatile fatty acids (VFAs), coenzyme F420 and electron transfer system (ETS) further confirmed these conclusions.

Operation adjustments of an electrochemically coupled system for total nitrogen removal and the associated mechanism.

A coupled system consisting of sequencing batch reactor and microbial fuel cell (SBR-MFC) was designed to buffer pH drift and purify wastewater. The addition of nitrifying sludge and the adjustment of hydraulic retention time (HRT) were performed to achieve better removal of total nitrogen (TN). When anaerobic/aerobic/anoxic phases in one cycle were 6/4/2 h, the removal efficiency of ammonium was 99.0 ± 1.3%, whereas denitrification was insufficient and the overall removal efficiency of TN was only 29.1 ± 5.8%. When the phases were adjusted to 6/2/4 h, the removal efficiencies of ammonium were 100.0 ± 0.0% in both closed and open circuits, and the overall removal efficiencies of TN were 91.4 ± 0.2% and 71.7 ± 4.2%, respectively, improved by 20% in MFC mode; the maximum voltage (200 Ω) maintained at 0.1 V. Ammonium-oxidizing bacteria (AOB) and Nitrite-oxidizing bacteria (NOB) in the sludge carried out nitrification. The main denitrification pathways in anoxic phase involved polyhydroxyalkanoate (PHA) denitrification by denitrifying glycogen accumulating organisms (GAOs) and electrochemical denitrification by electrochemical active bacteria (EAB). Few polyphosphate accumulating organisms (PAOs) were present, which accounted for poor P removal.

Effect of bamboo vinegar powder as an antibiotic alternative on the digesta bacteria communities of finishing pigs.

This study investigated the use for bamboo vinegar powder as an antibiotic alternative in the diet of growing-finishing pigs by examining their digestive bacterial communities. Forty-five Duroc × Landrace × Yorkshire growing-finishing pigs were randomly allocated to five diet groups: 0%, 0.5%, 1.0%, or 1.5% bamboo vinegar levels and antibiotics. After 37 days, the digesta in duodenum of four pigs from each treatment were analyzed for their bacterial community compositions using 16S rRNA gene sequencing. The addition of 1.5% bamboo vinegar powder had an effect on the intestinal microflora most similar to that of antibiotics, indicating its potential to promote the growth and development of finishing pigs. We also found the 1.5% bamboo vinegar powder group to have an increased abundance of Firmicutes/Bacteroidetes compared with the other bamboo vinegar powder groups, which may enhance the ability of the host to absorb food energy and store more body fat. Additionally, the effects of bamboo vinegar powder on promoting the abundances of Lactobacillus and Thalassospira and on inhibiting Streptococcus and Prevotella growth revealed it may play an important role in animal production. Moreover, functional predictions of microbes via PICRUSt indicated that feed supplemented with 1.5% bamboo vinegar powder could promote many vital metabolic pathways.