Atomically Dispersed Fe-N4 Site as a Conductive Bridge Enables Efficient and Stable Activation of Peroxymonosulfate: Active Site Renewal, Anti-Oxidative Capacity, and Pathway Alternation Mechanism.

Atomically dispersed metal sites anchored on nitrogen-doped carbonaceous substrates (M-NCs) have emerged as promising alternatives to conventional peroxymonosulfate (PMS) activators; however, the exact contribution of each site still remains elusive. Herein, isolated Fe-N4 active site-decorated three-dimensional NC substrates (FeSA-NC) via a micropore confinement strategy are fabricated to initiate PMS oxidation reaction, achieving a specific activity of 5.16 × 103 L·min-1·g-1 for the degradation of bisphenol A (BPA), which outperforms most of the state-of-the-art single-atom (SA) catalysts. Mechanism inquiry reveals enhanced chemisorption and electron transfer between PMS and FeSA-NC, enabling an inner electron shuttle mechanism in which Fe-N4 serves as a conductive bridge. The Fe-N4 sites reduce the energy barrier for the formation of SO5* and H*, thereby transforming the reaction pathway from directly adjacent electron transfer into reactive oxygen species (ROS)-dominated oxidation. Theoretical calculations and dynamic simulations reveal that the Fe-N4 sites induce facilitated desorption of reaction intermediates (PMS*/BPA*), which collectively contribute to the renewal of active sites and eventually enhance the catalytic durability. This work offers a reasonable interpretation for the important role of the Fe-N4 moiety in altering the activation mechanism and enhancing the antioxidative capacity of NC materials, which fundamentally furnishes theoretical support for SA material design.

Blocking polymerization of CTFs induces plentiful structural terminations for synchronous removal of organics and Cr(VI).

Herein, an ultramild block polymerization strategy was employed to precisely control the exposure of structural terminations in the skeleton of covalent triazine-based frameworks (CTFs). The generated structural terminations with cyano (-CN) and hydroxy (-OH) groups (STCHs) could serve as not only the optimal adsorption sites for enriching targets, but also π-conjugated electron donor-acceptor dyads to accelerate the charge transfer. With spatial separation of charge localization sites, STCH-CTF exhibited a photoactivity of 2.5-4 times higher than that of pristine CTFs in the simultaneous oxidation of bisphenol A (BPA) and the reduction of hexavalent chromium (Cr(vi)).

Improved oxidation of refractory organics in concentrated leachate by a Fe2+-enhanced O3/H2O2 process.

Concentrated leachate from membrane processes, which contains a mass of refractory organics and salt, has become a new problem for wastewater engineers. In this study, removal of organic contaminants in concentrated landfill leachate was investigated by applying the ferrous ion (Fe2+) catalyzed O3/H2O2 process. The maximum chemical oxygen demand (COD) and absorbance at 254 nm (UV254) removal efficiencies under the optimal conditions (initial pH = 3.0, Fe2+ dosage = 6.500 mM, H2O2 dosage = 18.8 mM and O3 dosage = 52.65 mg min-1) were 48.82% and 63.59%, respectively. These were higher than those achieved using the Fe2+/O3, O3/H2O2, and O3 processes, and biodegradability of the leachate was improved significantly. Moreover, compared with other processes, the Fe2+ had a stronger catalytic effect. Molecular distribution analysis and three-dimensional excitation and emission matrix analysis both indicated that the fulvic acid and humic acid in the concentrated leachate were greatly degraded. Ultraviolet-visible spectra showed that the Fe2+/O3/H2O2 process mainly destroyed unsaturated bonds and decreased the aromatic degree of the leachate. The reaction mechanism of the Fe2+/O3/H2O2 process mainly was attributed to three factors: (1) O3 and H2O2 reacting to produce •OH; (2) H2O2 and O3 decomposing into •OH through the oxidation of Fe2+ to Fe3+; and (3) coagulation by Fe (OH)3. The •OH can rapidly degrade recalcitrant organics, and coagulation also increases the removal of organic matter. Therefore, the Fe2+/O3/H2O2 process was an effective method for treating concentrated landfill leachate.

Meta-analysis of laparoscopy assisted distal gastrectomy and conventional open distal gastrectomy for EGC.

In recent decades, laparoscopy assisted distal gastrectomy (LADG) has been introduced to treat early gastric cancer (EGC). This study evaluated the safety and efficacy of laparoscopy assisted and conventional open distal gastrectomy for EGC. Comprehensive searches of PubMed, EmBase, Cochrane Controlled Trials Register and Chinese Biomedical Database (CBM) were performed. Included literature was evaluated using the Newcastle-Ottawa Scale. Original data were extracted, pooled odds ratio (OR) and 95% confidence intervals (CI) were calculated using RevMan 5.0. Eight RCTs of 734 patients were included in the study. Compared to CODG, LADG increases the operation time (weighted mean difference [WMD]: 63.35; 95% confidence interval [CI]: 57.96, 68.74; P<0.01), reduces intraoperative blood loss (WMD: -127.95; 95% CI: -147.97, -107.93; P<0.01), decreases number of harvested lymph nodes (WMD: -4.21; 95% CI: -6.10, -2.31; P<0.01), forwards oral intake time (WMD:-0.43; 95% CI: -0.61, -0.24; P<0.01), and shortens hospital stay(WMD: -1.29; 95% CI: -1.76, -0.83; P<0.01). There is no significant difference in postoperative complications(OR: 0.70; 95% CI: 0.46, 1.06; P=0.09). All these findings indicate that LADG for EGC is feasible and safe.