A Comparative Study on the Oxidation Mechanisms of Substituted Phenolic Pollutants by Ferrate(VI) through Experiments and Density Functional Theory Calculations.

In this work, the oxidation of five phenolic contaminants by ferrate(VI) was comparatively investigated to explore the possible reaction mechanisms by combined experimental results and theoretical calculations. The second-order rate constants were positively correlated with the energy of the highest occupied molecular orbital. Considering electronic effects of different substituents, the easy oxidation of phenols by ferrate(VI) could be ranked as the electron-donating group (-R) > weak electron-withdrawing group (-X) > strong electron-withdrawing group (-(C═O)-). The contributions of reactive species (Fe(VI), Fe(V)/(IV), and •OH) were determined, and Fe(VI) was found to dominate the reaction process. Four main reaction mechanisms including single-oxygen transfer (SOT), double-oxygen transfer (DOT), •OH attack, and electron-transfer-mediated coupling reaction were proposed for the ferrate(VI) oxidation process. According to density functional theory calculation results, the presence of -(C═O)- was more conducive for the occurrence of DOT and •OH attack reactions than -R and -X, while the tendency of SOT for different substituents was -R > -(C═O)- > -X and that of e--transfer reaction was -R > -X > -(C═O)-. Moreover, the DOT pathway was found in the oxidation of all four substituted phenols, indicating that it may be a common reaction mechanism during the ferrate(VI) oxidation of phenolic compounds.

Promoting Effect of Silver Oxide Nanoparticles on the Oxidation of Bisphenol B by Ferrate(VI).

Bisphenol B (BPB, 2,2-bis(4-hydroxyphenyl) butane), as a substitute for bisphenol A, has been widely detected in the environment and become a potential threat to environmental health. This work found that silver oxide nanoparticles (Ag2O) could greatly promote the removal of BPB by ferrate (Fe(VI)). With the presence of 463 mg/L Ag2O, the amount of Fe(VI) required for the complete removal of 10 µM BPB will be reduced by 70%. Meanwhile, the recyclability and stability of Ag2O have been verified by recycling experiments. The characterization results and in situ electrochemical analyses showed that Ag(II) was produced from Ag(I) in the Fe(VI)-Ag2O system, which has a higher electrode potential to oxidize BPB to enhance its removal. A total of 13 intermediates were identified by high-resolution mass spectrometry, and three main reaction pathways were proposed, including oxygen transfer, bond breaking, and polymerization. Based on the toxicity assessment through the ECOSAR program, it is considered that the presence of Ag2O reduced the toxicity of BPB oxidation intermediates to aquatic organisms. These results would deepen our understanding of the interaction between Fe(VI) and Ag2O, which may provide an efficient and environmentally friendly method for water and wastewater treatment.

Clostridium difficile carriage in hospitalized cancer patients: a prospective investigation in eastern China.

BACKGROUND: Clostridium difficile carriage has been considered as a potential source for the deadly infection, but its role in cancer patients is still unclear. We aimed to identify the clinical and immunological factors that are related to C. difficile carriage in Chinese cancer patients. METHODS: A total of 400 stool samples were collected from cancer patients who received chemotherapy in three hospitals of eastern China. Bacterial genomic DNA was extracted and two toxin genes (tcdA and tcdB) were detected. PCR ribotyping was performed using capillary gel electrophoresis. Concentrations of prostaglandin E2 (PGE2), transforming growth factor beta (TGF-ß) and interleukin-10 (IL-10) were measured using enzyme-linked immunosorbent assay (ELISA) kits. RESULTS: Eighty-two (20.5%) samples were confirmed to be C. difficile-positive and positive for tpi, tcdA, and tcdB genes. The C. difficile-positive rates in patients with diarrhea and no diarrhea were 35% and 19.7%, respectively (p = 0.09). Patients who were younger than 50 years old and were hospitalized for at least 10 days had a C. difficile-positive rate as high as 35%. In contrast, patients who were older than 50 years old and were hospitalized for less than 10 days had a C. difficile-positive rate of only 12.7% (p = 0.0009). No association was found between C. difficile carriage and chemotherapy regimen, antibiotic drug use, or immunosuppressive mediators, such as prostaglandin E2 (PGE2), transforming growth factor beta (TGF-ß), or interleukin-10 (IL-10). Twelve ribotypes of C. difficile were identified, but none of them belonged to ribotype 027. CONCLUSIONS: We conclude that younger patients and those with longer hospitalization stays may be more prone to C. difficile carriage. Studies of larger populations are warranted to clarify the exact role of C. difficile carriage in hospitalized cancer patients in China.

Ferrate(VI) oxidation of bisphenol E-Kinetics, removal performance, and dihydroxylation mechanism.

Bisphenol E (bis (4-hydroxyphenyl) ethane, BPE), as a typical endocrine disrupting chemical, is commonly detected in source water and drinking water, which poses potential risks to human health and ecological environment. This paper investigated the removal of BPE by ferrate(VI) (FeVIO42-, Fe(VI)) in water. Under the optimal condition of [Fe(VI)]0:[BPE]0 = 10:1 and pH = 8.0, a removal efficiency of 99% was achived in 180 s. Sixteen intermediates of BPE were detected, and four possible reaction pathways were proposed, which mainly involved the reaction modes of double-oxygen and single-oxygen transfer, bond breaking, carboxylation and polymerization. The double-oxygen transfer mechanism, different from traditional mechanisms, was newly proposed to illustrate the direct generation of di-hydroxylated products from parent BPE, which was demonstrated by theoretical calculations for its rationality. Significantly, NO2-, HCO3-, Cu2+, and humic acid, constituents of water promoted the removal of BPE. Additionally, samples from river, tap water, synthetic wastewater, and secondary effluent were tested to explore the feasibility of Fe(VI) oxidation for treating BPE in water. It was found that 99% of BPE was degraded within 300 s in these waters except for synthetic wastewater. The toxicity of BPE and its intermediates was evaluated by ECOSAR program, and the results showed that Fe(VI) oxidation decreased the toxicity of reaction solutions. These findings demonstrated that the Fe(VI) oxidation process was an efficient and green method for the treatment of BPE, and the new insights into the double-oxygen transfer mechanism aid to understand the reaction mechanisms of organic pollutants oxidized by Fe(VI).

Experimental and theoretical study on the degradation of Benzophenone-1 by Ferrate(VI): New insights into the oxidation mechanism.

The oxidation of Benzophenone-1 (BP-1) by ferrate (Fe(VI)) was systemically investigated in this study. Neutral pH and high oxidant dose were favorable for the reaction, and the second order rate constant was 1.03 × 103 M-1·s-1 at pH = 7.0 and [Fe(VI)]0:[BP-1]0 = 10:1. The removal efficiency of BP-1 was enhanced by cations (K+, Ca2+, Mg2+, Cu2+, and Fe3+), while inhibited by high concentrations of anions (Cl- and HCO3-) and low concentrations of humic acid. Moreover, intermediates were identified by LC-MS, and five dominating reaction pathways were predicted, involving single hydroxylation, dioxygen transfer, bond breaking, polymerization and carboxylation. Theoretical calculations showed the dioxygen transfer could occur by Fe(VI) attacking the CC double-bond in benzene ring of BP-1 to form a five-membered ring intermediate, which was hydrolyzed twice followed by H-abstraction to generate the dihydroxy-added product directly from the parent compound. Dissolved CO2 or HCO3- might be fixed to produce carboxylated products, and Cl- led to the formation of two chlorinated products. In addition, the toxicity assessments showed the reaction reduced the environmental risk of BP-1. This work illustrates Fe(VI) could remove BP-1 in water environments efficiently, and the newly proposed dioxygen transfer mechanism herein may contribute to the development of Fe(VI) chemistry.

Association between the methylation status of the MGMT promoter in bone marrow specimens and chemotherapy outcomes of patients with acute myeloid leukemia.

The O(6)-methylguanine-DNA methyltransferase (MGMT) gene is a tumor suppressor gene that is associated with the risk of developing acute myeloid leukemia (AML). However, the association between the methylation status of the MGMT promoter and the chemotherapeutic outcomes of patients with AML remains unknown. In the present study, 30 bone marrow samples derived from patients with AML were collected prior and subsequent to chemotherapy. The methylation status of the MGMT promoter in the bone marrow specimens was determined by methylation-specific polymerase chain reaction. The results indicated that the methylation status of the MGMT promoter was influenced by different chemotherapeutic regimens. The MGMT methylation status of M4 patients (3 out of 6) were more chemosensitive, compared with that of patients with other AML subtypes (M1, 1 out of 3; M2, 0 out of 8; M3, 3 out of 7; M5, 0 out of 3; and M6, 1 out of 3). Age-based analysis revealed that the group aged ≤60 years (7 out of 24 patients) exhibited more methylation changes than patients aged >60 years (1 out of 6). Male patients (4 out of 13) were more susceptible to chemotherapy-induced methylation changes than female patients (4 out of 17). Thus, the methylation status of the MGMT promoter may serve as a potential biomarker to predict the therapeutic outcomes in male AML patients. However, further studies in larger sample sets are required to confirm the present findings.