Nitrogen-doped metal-free granular activated carbons as economical and easily separable catalysts for peroxymonosulfate and hydrogen peroxide activation to degrade bisphenol A.

The fabrication of low-cost, highly efficient, environmentally friendly, and easily separable metal-free heterogeneous catalysts for environmental remediation remains a challenge. In this study, granular nitrogen-doped highly developed porous carbons with a particle size of 0.25-0.30 mm were prepared by preoxidation and subsequent NH3 modification of a commercially available coconut-based activated carbon, and used to activate peroxymonosulphate (KHSO5) or hydrogen peroxide (H2O2) to degrade bisphenol A (BPA). The nitrogen-doped carbon (ACON-950) prepared by NH3 modification at 950 °C, with the addition of only 0.15 g/L could remove 100% of 50 mg/L BPA in 150 min, and more than 90% of the removed BPA was due to degradation. The removal rates of total organic carbon of ACON-950/KHSO5 and ACON-950/H2O2 systems reached 60.4% and 66.2% respectively, indicating the excellent catalytic activity of ACON-950. The reaction rate constant was significantly positively correlated with the absolute content of pyridinic N (N-6) and graphitic N (N-Q) and negatively and weakly positively correlated with pyrrolic N (N-5) and defects. Quenching experiments combined with electron paramagnetic resonance demonstrated that singlet oxygen was the dominant reactive oxidative species for BPA degradation. ACON-950 was characterized before and after the degradation reaction using N2 adsorption-desorption analyzer, Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results confirmed the prominent contribution of both the N-6 and N-Q to the catalytic performance of nitrogen-doped carbons. The reusability of ACON-950 and its application in actual water bodies further demonstrated its remarkable potential for the remediation of organic pollutants in wastewater.

Metal Ion-induced Gelation of High-concentration Graphite-like Crystalline Nanosheet Aqueous Suspensions.

The stability and transformation of nanomaterial aqueous suspensions are essential for their applications. Preparation of high-concentration carbon nanomaterials suspensions remains challenging due to their nonpolar nature. Herein, 200 mg mL-1 carbon nanomaterial aqueous suspensions are achieved by using graphite-like crystalline nanosheets (GCNs) with high hydrophilicity. Furthermore, these high-concentration GCN aqueous suspensions spontaneously transform into gels when induced by mono-, di-, and trivalent metal salt electrolytes at room temperature. Theoretical calculation of potential energy by DLVO theory reveals that the gelatinized GCNs is a new and metastable state between two usual forms of solution and coagulation. It is shown that the gelation of GCNs is due to the preferential orientation of nanosheets in an edge-edge arrangement, which differs from the case of solution and coagulation. High-temperature treatment of GCN gels produces metal/carbon materials with pore structures. This work provides a promising opportunity to create various metal/carbon functional materials.

Drying enables multiple reuses of activated carbon without regeneration.

Traditional regeneration of activated carbon is usually carried out by high-temperature oxidation in industrial processes, which reduces the quality and performance of the adsorbent, thereby increasing costs and damaging the environment. In this study, a simple drying process is proposed to enable reuse of spent activated carbon. The feasibility and merits of this method were evaluated in batch and continuous adsorption modes using dyes as adsorbates. The batch adsorption results showed that the activated carbon could be reused seven times after a simple drying process, because it led to full occupancy of the activated carbon pores by adsorbate molecules. The cumulative adsorption capacities of the activated carbon were as high as 1005.3 mg/g for methyl orange (MO) and 954.8 mg/g for methylene blue (MB). Continuous adsorption experiments in a fixed-bed column demonstrated that the activated carbon column could be reused more than three times after simply drying. Moreover, dye molecules adsorbed by the activated carbon were not leached by the stream of dye solution during reuse. This drying method exhibits three main merits for reuse of activated carbon, including (1) remarkably reduced consumption of fresh activated carbon to 51.5% or below, (2) significantly increased recovery of high-value adsorbate from the liquid phase, and (3) potential integration of multiple steps for industrial adsorption processes.

CO2/CH4 Separation via Carbon-Based Membrane: The Dynamic Role of Gas-Membrane Interface.

Membrane separation is considered one of the most promising CO2/CH4 separation technologies currently available because it is a safe, environment-friendly, and economical method. However, the inability of membrane materials to reconcile the trade-off between permeability and permeation selectivity limits their further applications; moreover, the mechanism underlying this process is unclear, which is mainly determined by the performance of gas adsorption and diffusion. Therefore, this paper describes the effect of gas adsorption and diffusion on membrane separation by assessing the fundamental gas-membrane and gas-gas interactions. Combining molecular simulation methods (Monte Carlo and molecular dynamics simulation) and a thermodynamic model called "linearized nonequilibrium thermodynamic transfer model", we investigate the permeability and permeation selectivity for CO2/CH4 in five carbon-based membranes and propose a general method for screening membrane materials. The interaction-dominated mechanism derived in this work provides new insights into membrane separation and facilitates the screening of high-performance membrane materials.

An interconnected and scalable hollow Si-C nanospheres/graphite composite for high-performance lithium-ion batteries.

Silicon (Si) anode is the most promising alternative for next generation lithium-ion batteries (LIBs) owing to large theoretical capacity, low working voltage and abundant natural resources. However, tremendous volume change of Si during the (de)lithiation processes causes repetitive formation of solid electrolyte interphase (SEI) layers, loss of electrical contact and electrodes pulverization, limiting its commercial application. Herein, we fabricate an interconnected hollow Si-C nanospheres/graphite composite via a facile and scalable approach. Notably, hollow Si-C nanospheres and graphite are homogeneously combined by using the surfactants as surface modifiers of graphite and introducing carbon dioxide (CO2) into magnesiothermic reduction reaction, resulting in the enhanced compatibility between hollow Si-C nanospheres and graphite, and the well-established electrical conductive network. The resultant Si-C nanospheres/graphite composite anode with carbon content of 59 wt% delivers a large reversible specific capacity of 662 mAh g-1 and a high capacity retention of 65.7% at 0.5 A g-1 after 200 cycles. Such excellent rate performance and superior cycling performance are attributed to high electrical conductivity and buffering effect of graphite, superior compatibility between hollow Si-C spheres and graphite, uniform distribution of both Si-C nanospheres with a unique hollow architecture and graphite flakes inside the composites and well-established interconnected electrical conductive carbon networks, which can effectively alleviate Si volume expansion and maintain good electrical contact during cycling. This strategy provides insights into designing Si-based anodes for practical LIBs.

Photocatalytic Oxidation of 5-Hydroxymethylfurfural Over Interfacial-Enhanced Ag/TiO2 Under Visible Light Irradiation.

Photocatalytic conversion of biomass-derived 5-hydroxyfurfural (HMF) to value-added 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) is an environmentally friendly process. Here, Ag nanoparticle (NP) supported on TiO2 (Ag/TiO2 ) materials with different interfacial structures were fabricated via incipient wetness impregnation. In the photocatalytic oxidation of 5-HMF to HMFCA, low-temperature reduction (473 K) on Ag/TiO2 could improve the photoinduced charge separation efficiency and promote the reaction due to the "enhanced" localized surface plasmon resonance (LSPR) effects achieved through strong metal-support interaction (SMSI). In particular, 2.5 % Ag/TiO2 -LTR exhibited superior performance with an HMFCA selectivity of up to 96.7 % under visible-light illumination. In contrast, the photocatalytic efficiency was greatly reduced when the reduction temperature increased to 773 K because of the encapsulation of Ag NPs by a thicker TiOx overlay, which significantly weakened visible-light harvesting. Overall, these findings offer an efficient methodology for designing interfacial enhanced plasmonic photocatalysts for the valorization of biomass.

U-Net combined with multi-scale attention mechanism for liver segmentation in CT images.

BACKGROUND: The liver is an important organ that undertakes the metabolic function of the human body. Liver cancer has become one of the cancers with the highest mortality. In clinic, it is an important work to extract the liver region accurately before the diagnosis and treatment of liver lesions. However, manual liver segmentation is a time-consuming and boring process. Not only that, but the segmentation results usually varies from person to person due to different work experience. In order to assist in clinical automatic liver segmentation, this paper proposes a U-shaped network with multi-scale attention mechanism for liver organ segmentation in CT images, which is called MSA-UNet. Our method makes a new design of U-Net encoder, decoder, skip connection, and context transition structure. These structures greatly enhance the feature extraction ability of encoder and the efficiency of decoder to recover spatial location information. We have designed many experiments on publicly available datasets to show the effectiveness of MSA-UNet. Compared with some other advanced segmentation methods, MSA-UNet finally achieved the best segmentation effect, reaching 98.00% dice similarity coefficient (DSC) and 96.08% intersection over union (IOU).

Efficient Hydrogenation of Xylose and Hemicellulosic Hydrolysate to Xylitol over Ni-Re Bimetallic Nanoparticle Catalyst.

A disadvantage of the commercial Raney Ni is that the Ni active sites are prone to leaching and deactivation in the hydrogenation of xylose to xylitol. To explore a more stable and robust catalyst, activated carbon (AC) supported Ni-Re bimetallic catalysts (Ni-Re/AC) were synthesized and used to hydrogenate xylose and hemicellulosic hydrolysate into xylitol under mild reaction conditions. In contrast to the monometallic Ni/AC catalyst, bimetallic Ni-Re/AC exhibited better catalytic performances in the hydrogenation of xylose to xylitol. A high xylitol yield up to 98% was achieved over Ni-Re/AC (nNi:nRe = 1:1) at 140 °C for 1 h. In addition, these bimetallic catalysts also had superior hydrogenation performance in the conversion of the hydrolysate derived from the hydrolysis reaction of the hemicellulose of Camellia oleifera shell. The characterization results showed that the addition of Re led to the formation of Ni-Re alloy and improved the dispersion of Ni active sites. The recycled experimental results revealed that the monometallic Ni and the bimetallic Ni-Re catalysts tended to deactivate, but the introduction of Re was able to remarkably improve the catalyst's stability and reduce the Ni leaching during the hydrogenation reaction.

Evolution of Phosphorus-Containing Groups on Activated Carbons during Heat Treatment.

Two types of activated carbons have been prepared by H3PO4 activation of lignocellulose and by H3PO4 modification of activated carbon, and then heat-treated at temperatures from 400 to 900 °C in an atmosphere of N2 or H2 to investigate the evolution of phosphorus-containing groups. Elemental analysis, X-ray photoelectron spectroscopy, 31P nuclear magnetic resonance, nitrogen adsorption, and scanning electron microscopy have been used to analyze the physicochemical properties of the activated carbons. The results show that C-O-P linkages of phosphorus-containing groups can progressively evolve into C-P-O, C3-P═O, C3-P, and eventually elemental phosphorus as a result of heat treatment. Phosphate-like groups are much more thermally stable in an N2 than in an H2 atmosphere. In N2, C-O-P linkages significantly evolve into C-P-O and C3-P═O at up to 800 °C, whereas C3-P linkages are not formed even at 900 °C. In H2, the corresponding evolution remarkably occurs at 500 °C, forming C3-P linkages and eventually elemental phosphorus. Moreover, the two activated carbons exhibit different evolution trends, suggesting that the evolution happens more easily for phosphorus-containing groups located on the edges of graphite-like crystallites than those in the lattice. Finally, we propose different evolution pathways of phosphorus-containing groups upon heat treatment in N2 and H2 atmospheres.

Preparation, characterization, and antibacterial activity of silver nanoparticle-decorated graphene oxide nanocomposite.

In this work, we report a facile and green approach to prepare a uniform silver nanoparticles (AgNPs) decorated graphene oxide (GO) nanocomposite (GO-Ag). The nanocomposite was fully characterized by transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra, ultraviolet-visible (UV-vis) absorption spectra, and X-ray photoelectron spectroscopy (XPS), which demonstrated that AgNPs with a diameter of approximately 22 nm were uniformly and compactly deposited on GO. To investigate the silver ion release behaviors, HEPES buffers with different pH (5.5, 7, and 8.5) were selected and the mechanism of release actions was discussed in detail. The cytotoxicity of GO-Ag nanocomposite was also studied using HEK 293 cells. GO-Ag nanocomposite displayed good cytocompatibility. Furthermore, the antibacterial properties of GO-Ag nanocomposite were studied using Gram-negative E. coli ATCC 25922 and Gram-positive S. aureus ATCC 6538 by both the plate count method and disk diffusion method. The nanocomposite showed excellent antibacterial activity. These results demonstrated that GO-Ag nanocomposite, as a kind of antibacterial material, had a great promise for application in a wide range of biomedical applications.