Carbon nitride nanotubes anchored with Cu(I) triggers peracetic acid activation with visible light for removal of antibiotic contaminants: Probing mechanisms of non-radical pathways and identifying active sites.

The peracetic acid (PAA)-activation process has attracted much attention in wastewater treatment. However, the low electron efficiency at the interface between heterogeneous catalysts and PAA has affected its practical application. For this study, we developed a carbon nitride hollow-nanotube catalysts with dispersed Cu(I) sites (Cu(I)-TCN) for the photocatalytic activation of PAA for antibiotics degradation. The obtained Cu(I)-TCN catalyst demonstrated an enhanced capacity for visible light harvesting along with increased charge transfer rates. Specifically, the developed Cu(I)-TCN/visible light/PAA system was able to completely remove antibiotics within 20 min, with a kinetic constant that was 25 times higher than a Cu(I)-TCN/visible light system, and 83 times higher than Cu(I)-TCN/PAA systems. Scavenging experiment and electron paramagnetic resonance (EPR) indicated that singlet oxygen was dominant reactive specie for sulfisoxazole (SIZ) removal. Besides, electrochemical tests and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy verified that the electron transfer efficiency of PAA activation was promoted due to the formation of inner-sphere interactions between PAA and Cu(I)-TCN, resulting in the quick removal of antibiotics. Further, after exposure to visible light, the Cu(I)-TCN excited photogenerated electrons which supplemented the electrons consumed in the reaction and drove the valence cycle of Cu ions. Overall, this research offered novel insights into the non-radical pathway for heterogeneous visible light-driven advanced oxidation processes and their potential for practical wastewater remediation.

Purification of MDI Isomers Using Dynamic Falling Film Melt Crystallization: Experiment and Molecular Simulation.

In this work, the isomer mixture of 4,4'-diphenylmethane diisocyanate (MDI) and 2,4'-MDI was separated and purified by dynamic falling film melt crystallization, and 99.3% purity and 50.8% yield of 4,4'-MDI could be obtained under optimized conditions. The separation mechanism was simulated by density functional theory (DFT) and molecular dynamics (MD) simulation. Results showed that compared with 2,4'-MDI, 4,4'-MDI molecules could form a more stable and symmetrical crystal structure due to their stronger charge density symmetry and electrostatic potential energy. Furthermore, the separation phenomenon and the formation of the crystal structure were observed according to the radial distribution function (RDF) and orientation correlation function obtained from MD simulation. Finally, the attachment energy (AE) model was used to observe and compare different crystal surfaces; it was proposed that the aggregation of 4,4'-MDI was attributed to the polar attraction between isocyanate groups according to the results of the orientation correlation function. It was also observed that compared with 2,4'-MDI, 4,4'-MDI molecules on the (110) crystal surface were easier to form crystal structures.

Optimization of the Ultrasonic-Assisted Extraction Technology of Steroidal Saponins from Polygonatum kingianum Collett & Hemsl and Evaluating Its Quality Planted in Different Areas.

Polygonatum kingianum Collett & Hemsl is one of the famous traditional Chinese herbs with satisfactory therapeutic effects on invigorating Qi, nourishing Yin and moistening lungs, in which steroidal saponins are one class of important active substances. The main purpose is to determine the optimal extraction technology of steroidal saponins and evaluate the quality of P. kingianum planted in five different areas. The optimal ultrasonic-assisted extraction (UAE) technology was established by using single-factor experiments and the response surface methodology (RSM), and the determination method of high-performance liquid chromatography (HPLC) for dioscin and diosgenin, two primary types of acid-hydrolyzed steroidal saponins, was constructed with good linear range and precision. The results showed that UAE was an efficient extraction method for steroidal saponins, and the extraction yield was significantly affected by the liquid-solid ratio. The optimal extraction technology was generated following a liquid-solid ratio of 10:1 (mL/g), an ethanol concentration of 85% (v/v), an extraction time of 75 min, an extraction temperature of 50 °C and three extractions, of which these parameters were in line with the predicted values calculated by RSM. Considering only dioscin and diosgenin, the quality of P. kingianum planted at five sample plots presented non-significant difference. However, the content of diosgenin in Pingbian Prefecture (PB) was higher than that of the other four areas with a value of 0.46 mg/g. Taken together, the optimal UAE technology for P. kingianum steroidal saponins was determined via RSM. The quality evaluation revealed that there was a non-significant difference among P. kingianum planted in different areas based on the contents of the sum of dioscin and diosgenin. This work has important reference value for the exploitation and utilization of P. kingianum.

Ru/g-C3N4 as an efficient catalyst for selective hydrogenation of aromatic diamines to alicyclic diamines.

A series of Ru/g-C3N4 materials with highly dispersed Ru were firstly prepared by an ultrasonic impregnation method using carbon nitride as a support. The catalysts were characterized by various techniques including BET and elemental analysis, ICP-AES, XPS, XRD, CO2-TPD and TEM. The results demonstrated that Ru/g-C3N4 materials with a mesoporous structure and highly dispersed Ru were successfully prepared. The chemo-selective hydrogenation of p-phenylenediamine (PPDA) to 1,4-cyclohexanediamine (CHDA) over Ru/g-C3N4 as a model reaction was investigated in detail. PPDA conversion of 100% with a CHDA selectivity of more than 86% could be achieved under mild conditions. It can be inferred that the carbon nitride support possessed abundant basic sites and the Ru/g-C3N4-T catalysts provided suitable basicity for the aromatic ring hydrogenation. Compared to the N-free Ru/C catalyst, the involvement of nitrogen species in Ru/g-C3N4 remarkably improved the catalytic performance. In addition, the recyclability of the catalyst demonstrated that the aggregation of Ru nanoparticles was responsible for the decrease of the catalytic activity. Furthermore, this strategy also could be expanded to the selective hydrogenation of other aromatic diamines to alicyclic diamines.

The synthetic evaluation of CuO-MnOx-modified pinecone biochar for simultaneous removal formaldehyde and elemental mercury from simulated flue gas.

A series of low-cost Cu-Mn-mixed oxides supported on biochar (CuMn/HBC) synthesized by an impregnation method were applied to study the simultaneous removal of formaldehyde (HCHO) and elemental mercury (Hg0) at 100-300° C from simulated flue gas. The metal loading value, Cu/Mn molar ratio, flue gas components, reaction mechanism, and interrelationship between HCHO removal and Hg0 removal were also investigated. Results suggested that 12%CuMn/HBC showed the highest removal efficiency of HCHO and Hg0 at 175° C corresponding to 89%and 83%, respectively. The addition of NO and SO2 exhibited inhibitive influence on HCHO removal. For the removal of Hg0, NO showed slightly positive influence and SO2 had an inhibitive effect. Meanwhile, O2 had positive impact on the removal of HCHO and Hg0. The samples were characterized by SEM, XRD, BET, XPS, ICP-AES, FTIR, and H2-TPR. The sample characterization illustrated that CuMn/HBC possessed the high pore volume and specific surface area. The chemisorbed oxygen (Oß) and the lattice oxygen (Oα) which took part in the removal reaction largely existed in CuMn/HBC. What is more, MnO2 and CuO (or Cu2O) were highly dispersed on the CuMn/HBC surface. The strong synergistic effect between Cu-Mn mixed oxides was critical to the removal reaction of HCHO and Hg0 via the redox equilibrium of Mn4+ + Cu+ ↔ Mn3+ + Cu2+.

A novel adaptive level set segmentation method.

The adaptive distance preserving level set (ADPLS) method is fast and not dependent on the initial contour for the segmentation of images with intensity inhomogeneity, but it often leads to segmentation with compromised accuracy. And the local binary fitting model (LBF) method can achieve segmentation with higher accuracy but with low speed and sensitivity to initial contour placements. In this paper, a novel and adaptive fusing level set method has been presented to combine the desirable properties of these two methods, respectively. In the proposed method, the weights of the ADPLS and LBF are automatically adjusted according to the spatial information of the image. Experimental results show that the comprehensive performance indicators, such as accuracy, speed, and stability, can be significantly improved by using this improved method.