Improvement of Carbonyl Groups and Surface Defects in Carbon Nanotubes to Activate Peroxydisulfate for Tetracycline Degradation.

Carbon nanotubes (CNTs) were considered a promising activator for persulfates due to their high electrical conductivity, large specific surface area and low toxicity. The functional groups and surface defects of CNTs could significantly affect their activation performance. In this study, CNTs with high C=O ratio and defect density (CNT-O-H) were prepared through a facile treatment of raw CNTs with HNO3 oxidation followed by calcination at 800 °C under an argon atmosphere. X-ray photoelectron spectroscopy (XPS) and Raman results showed that the C=O proportion and defect degree (ID/IG) rose to 75% and 1.53, respectively. The obtained CNT-O-H possessed a superior performance towards peroxydisulfate (PDS) activation, and the degradation efficiency of tetracycline (TC) in the CNT-O-H/PDS system was increased to 75.2% from 56.2% of the raw CNTs/PDS system within 40 min. Moreover, the activity of CNT-O-H after use could be easily recovered with re-calcination. In addition, the CNT-O-H/PDS system exhibited high adaptabilities towards wide solution pH (2-10), common coexisting substances and diverse organic pollutants. Singlet oxygen (1O2) was confirmed to be the dominant reactive oxygen species (ROS) generated in the CNT-O-H/PDS system. It was inferred that surface C=O groups and defects of CNTs were the key site to activate PDS for TC degradation.

Investigation on visible-light photocatalytic performance and mechanism of zinc peroxide for tetracycline degradation and Escherichia coli inactivation.

In this study, zincperoxide (ZnO2) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO2 (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4-12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO2 could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O2-) and singlet oxygen (1O2) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H2O2 under the catalysis of Zn(OH)2 from the hydrolysis of partial ZnO2, respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO2 for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation andE. coli inactivation over ZnO2.

Efficient degradation of tetracycline in wide pH range using MgNCN/MgO nanocomposites as novel H2O2 activator.

Currently existing Fenton-like catalysts were limited in wastewater treatment owing to their potential transition-metal poisoning, narrow applicable pH range and high dependence on external energy excitation. In this work, the MgNCN/MgO nanocomposites were firstly synthesized by a facile one-pot calcination of melamine and basic magnesium carbonate, and used as novel H2O2 activator for antibiotic removal. It was found that the MgNCN/MgO composite calcined at 550°C with the mass ratio of melamine to basic magnesium carbonate at 2:1, exhibited an excellent catalytic ability to tetracycline (TC) degradation in a wide pH range of 4-10 without any external energy input. More than 90% of TC (100 mL, 50 mg/L) could be degraded within 30 min by 10 mg of the nanocomposite in the presence of 0.2 mL of 30 wt% H2O2. Based on the experimental results, it was concluded that the Mg-N coordination between MgNCN and MgO in MgNCN/MgO nanocomposites activated H2O2 to produce primary singlet oxygen (1O2) and minor hydroxyl radicals (·OH), responding for TC degradation. In addition, the degradation pathways of TC were deduced by determining the generated intermediates during the degradation process. This work provided a novel idea for designing transition-metal-free catalysts for nonradical activation of H2O2 in the absence of external energy excitation.

Dramatically enhanced degradation of recalcitrant organic contaminants in MgO2/Fe(III) Fenton-like system by organic chelating agents.

Herein, the application of organic acids as chelating agent, including citric acid (CA), tartaric acid (TA), oxalic acid (OA) and ethylenediaminetetraacetic acid (EDTA), to enhance the degradation performance of MgO2/Fe(III) system was investigated in the terms of chelating agent dosage, Fe(III) dosage, reaction temperature, initial solution pH and inorganic anion. When the molar ratio of MgO2/Fe(III)/chelating agent was 1 : 0.7 : 0.3, the degradation efficiencies of Rhodamine B (RhB) increased from 6.7% (without chelating agent) to 42.3%, 98.5%, 48.9% and 25.8% within 30 min for CA, TA, OA, and EDTA, respectively. The promotion effect was mainly attributed to the chelation between chelating agents and Fe(III), rather than the acidification of chelating agents. The pseudo-first-order kinetic model well fitted RhB degradation in MgO2/Fe(III)/TA system, and the kinetic rate constant reached up to 0.295 min-1. Hydroxyl radical was confirmed to be the dominant active species to degrade organics in the MgO2/Fe(III)/TA system. Notably, the degradation system could work in a broad pH (3-11) and temperature (5-35 °C) range. Moreover, the MgO2/Fe(III)/TA system can also effectively degrade methylene blue, tetracycline and bisphenol A. This work provided a new, efficient and environmentally-friendly Fenton-like system for stubborn contaminant treatment.

Facile one-step synthesis of 3D hierarchical flower-like magnesium peroxide for efficient and fast removal of tetracycline from aqueous solution.

Hierarchically three dimensional (3D) flower-like magnesium peroxide (MgO2) nanostructures were synthesized through a facile one-step precipitation method. The effects of magnesium salt, reaction temperature, precipitant and surfactant on the morphology and structure of MgO2 were systematically investigated. The as-obtained samples using magnesium sulfate, ammonia and trisodium citrate were composed of 3D flowers assembled by numerous nanosheets, and SO42- played a vital role in the formation of flower-like nanostructures. The 3D flower-like MgO2 possessed high active oxygen content of 24.10 wt% and large specific surface area of 385 m2/g. Ten mg of flower-like MgO2 could efficiently degrade 90 % of tetracycline (TC) within 60 min under stirring condition. ESR tests and radical quenching experiments suggested that hydroxyl radicals were crucial for TC degradation. Moreover, the column filled with flower-like MgO2 could quickly and efficiently eliminate TC with the assistance of air flow, and the degradation efficiency almost had no decrease even after twenty consecutive runs. Significantly, the concentrations of magnesium and iron ions dissolved in the filtrate from the column were far below the limits of drinking water standards. Additionally, the possible degradation pathways of TC were also proposed according to the determination of generated intermediates during the degradation process.

Enhanced dark adsorption and visible-light-driven photocatalytic properties of narrower-band-gap Cu2S decorated Cu2O nanocomposites for efficient removal of organic pollutants.

The Cu2S-decorated Cu2O nanocomposites were synthesized by a facile co-precipitation and calcination method, and used as adsorbent and photocatalyst to remove organic pollutants from wastewater. Batch adsorption experiments were conducted to investigate the influences of molar ratio of Cu2O to Cu2S, initial solution pH, coexisting anion and temperature on the adsorption performances. As-obtained Cu2O/Cu2S-9/1 nanocomposite with high specific surface area (45.88 m2/g) exhibited superior adsorption ability towards Congo red, methyl orange and tetracycline in aqueous solution. The adsorption of organics onto the nanocomposite was a spontaneous and exothermic process, and the adsorption processes could be well described by the Freundlich isothermic and Pseudo-second-order kinetic models. The Cu2O/Cu2S-9/1 nanocomposite also showed excellent photocatalytic degradation activities for organic pollutants. Optical properties characterization suggested that the decoration of Cu2S could effectively enhance visible-light absorption and inhibit the recombination of photo-generated electron-hole pairs. ESR tests and trapping experiments of reactive species indicated that both superoxide radicals (O2-) and holes (h+) were crucial for the photocatalytic degradation of organic pollutants. Moreover, the photocatalytic efficiency of Cu2O/Cu2S-9/1 nanocomposite had no significant decrease even after four consecutive runs. The bifunctional nanocomposite as adsorbent and photocatalyst presents a great potential in treating organic-contaminated wastewater.

Application of fast-track surgery in the perioperative period of laparoscopic partial nephrectomy for renal tumors.

OBJECTIVES: This study aimed to examine application of fast-track surgery (FTS) in the perioperative period of laparoscopic partial nephrectomy for renal tumors, and to discuss its effects and safety. METHODS: Eighty patients who received laparoscopic partial nephrectomy in urinary surgery from January 2016 to December 2017 were selected and randomly classified as the observation group (n = 40) and control group (n = 40). Traditional treatments were performed in the control group, while FTS was applied in the observation group. The complication rate after the operation was recorded. RESULTS: The duration of the operation and intraoperative blood loss were not different between the groups. The duration of anesthesia and fluid transfusion volume on the day of the operation were significantly less in the observation group than in the control group. The rates of infection of the incisional wound, nausea and vomiting, and anastomotic stomal bleeding were not significantly different between the groups. However, the rates of postoperative urinary tract infection, abdominal distension, thirst, hypothermia, and pulmonary infection were significantly lower in the observation group than in the control group. CONCLUSION: Application of FTS in laparoscopic partial nephrectomy contributes to postoperative recovery and reduction of postoperative complications.

Highly pure MgO2 nanoparticles as robust solid oxidant for enhanced Fenton-like degradation of organic contaminants.

In typical Fenton/Fenton-like reactions, H2O2 was usually used as an oxidant to degrade organic contaminants. However, liquid H2O2 is unstable, easy to decompose and has high biological toxicity especially at high concentration. Herein, highly pure magnesium peroxide (MgO2) nanoparticles were first synthesized and used instead of H2O2 to degrade organic dyes. The structure and morphology of as-prepared products were confirmed by XRD, SEM, TEM and FTIR techniques. The active oxygen content of MgO2 nanoparticles reached up to 26.93 wt%, suggesting a high purity of the as-prepared sample. The degradation performance of MgO2 nanoparticles towards organic contaminants was systematically investigated in the terms of the molar ratio of Fe3+ to MgO2, the dosage of MgO2, initial solution pH and different organic dyes. The results indicated the as-prepared MgO2 exhibited excellent degradation ability to various types of organic dyes. 10 mg of MgO2 nanoparticles could almost completely degrade 200 mL of 20 mg/L methylene blue (MB) in 30 min with a TOC removal rate of 70.2%. The efficient degradation performance was ascribed to the generation of hydroxyl radicals in the MgO2/Fe3+ system. The pathways of MB degradation were also proposed based on the determination of the reaction intermediates.

Hydrophobic modification of nanoscale zero-valent iron with excellent stability and floatability for efficient removal of floating oil on water.

Usually, nanoscale zero-valent iron (NZVI) cannot float on water because of high density and hydrophilic surface. Herein, alkyltrimethoxysilanes with different carbon chain lengths (C1, C8 and C16) were used as "water-repellent legs" to graft onto NZVI, enduing NZVI with hydrophobic and floatable characteristics like a water strider. The hydrophobic performance of as-modified NZVI materials was found to be better when NZVI was modified by alkyltrimethoxysilane with longer carbon chain, and a large contact angle of 151.2°(>150°) was obtained in C16-NZVI, indicating the superhydrophobic characteristic of C16-NZVI. The oil-absorption experiments showed that the absorption capacity of C16-NZVI for lubricating oil reached 9.73 g/g within 30 s. After seven consecutive runs, the oil-absorption capacity of C16-NZVI still maintained at 9.26 g/g, indicating high reusability of C16-NZVI. Also, C16-NZVI exhibited excellent stability in NaCl solution without being oxidized for 32 d. Significantly, C16-NZVI possessed admirable chemical stability with high hydrophobic property in acid and alkaline solutions (pH 3-12). Considering the advantages of easy preparation, high stability and reusability, excellent oil-absorption capacity as well as magnetic recovery property, C16-NZVI is expected to have remarkable potential in the treatment of floating oil on water/seawater.

Facile modification of nanoscale zero-valent iron with high stability for Cr(VI) remediation.

In this study, a highly stable nanoscale zero-valent iron composite (HS-NZVI) was obtained via modifying nanoscale zero-valent iron (NZVI) with tetraethyl orthosilicate (TEOS) and hexadecyltrimethoxysilane (HDTMOS), and used for Cr(VI) remediation in aqueous solution. The obtained HS-NZVI remained stable in water without being oxidized for over 12h. After four consecutive runs, the Cr(VI) removal efficiency of HS-NZVI maintained a value of more than 82%. Moreover, the Cr(VI) removal capacity per unit weight of NZVI in HS-NZVI reached 292.8mg/g within 60min at the initial Cr(VI) concentration of 120mg/L at pH5. The Cr(VI) removal efficiency of HS-NZVI increased with decreasing solution pH, and the experimental data for Cr(VI) removal by HS-NZVI were well-described by the pseudo-first-order reaction model. Additionally, scanning electron microscope (SEM) images, X-ray diffraction (XRD) patterns and X-ray photoelectron spectroscopy (XPS) measurements of the product after reaction revealed that the mechanism of Cr(VI) remediation by HS-NZVI mainly involved adsorption, reduction and co-precipitation. Considering the advantages of easy preparation, excellent stability and reusability, and high Cr(VI) removal capacity as well as the magnetic recovery property, HS-NZVI is expected to have notably promising applications for the remediation of Cr(VI) contaminated sites.

Anchoring of silver nanoparticles on graphitic carbon nitride sheets for the synergistic catalytic reduction of 4-nitrophenol.

In this paper, a facile process was developed for anchoring of silver nanoparticles on graphitic carbon nitride sheets (Ag/g-C3N4) with high catalytic activity for reduction of 4-nitrophenol. The morphology and structure of the as-prepared Ag/g-C3N4 composite were investigated by FESEM, TEM, XRD and XPS. The reaction mechanism and the reduction kinetics of 4-nitrophenol under different light irradiation were systematically studied. The results showed that the obtained Ag/g-C3N4 composite exhibited a much higher electro/photo catalytic activity and stability for reduction of 4-nitrophenol. Significantly, due to the synergistic effect and interaction between highly dispersed Ag nanoparticles (Ag NPs, ∼7.2 nm) and lamellar g-C3N4, not only transfer of interfacial charge, but also the separation of photoinduced electrons occurred when the reaction was proceeded under light. In addition, the composite exhibited high stability and reusability during the cycling experiments. The results showed that the Ag/g-C3N4 composite is an effective and stable electro/photo catalyst for reduction of 4-nitrophenol.

Influence of water on room-temperature preparation of silver nanoparticles using poly(vinyl pyrrolidone) as reducing agent.

Silver nanoparticles (Ag NPs) were prepared via a wet-chemical method in the presence of poly(vinyl pyrrolidone) (PVP) without other reducing agents at room temperature. The influence of the addition of water on the preparation of Ag NPs was investigated. It was found that water addition has a significant influence on the reduction reaction, resulting in changes of shape, size and optical properties of the particles. When large amounts of water were added, the reduction rate was very slow. However, when small amounts of water were used, the opposite effects on the reaction process were observed, initial inhibition effect and final promotion effect. Two main possible mechanisms were proposed to explain the opposite effects of two reaction stages with small amounts of water addition: (1) the initial inhibition effect was induced by free oxygen in water, which would react preferentially with the reducing species in the system; (2) the promotion effect thereafter may be due to the differences of chain extension of PVP molecules and electron transfer rate in ethanol and water.

Synthesis and characterization of highly crystalline MgO nanopowders via a modified chemical-precipitation process.

A modified chemical-precipitation method is proposed to synthesize MgO nanopowders with high crystallinity at a low temperature of 400 degrees C using acetic acid as a modifier. The as-obtained intermediates and final products were investigated by Fourier-transformed infrared spectroscopy, thermogravimetric analysis, X-ray diffraction and transmission electron microscopy, respectively. The influence of acetic acid in the MgO preparation process was also investigated by a comparison of the samples without acetic acid, and the mechanism of acetic acid modification is also proposed. The carboxyl group of acetic acid could coordinate with Mg atom in a monodentate mode to form a new organic ligand intermediate Mg(OH)(OCOCH3), which facilitates the thermal decomposition of the intermediate at low temperature and enhances the crystallization of MgO.

Facile, template-free synthesis of silver nanodendrites with high catalytic activity for the reduction of p-nitrophenol.

Here we report a facile, surfactant-free and template-free synthesis process of highly uniform dendritic silver nanostructures with high catalytic activity for the reduction of p-nitrophenol. By controlling the concentration of AgNO(3) aqueous solution and the reaction time, various shapes of silver nanodendrites (SNDs) could be obtained easily. The effects of different parameters such as concentrations of the reagents and reaction time on the morphology and structure of as-prepared tree-like nanostructures have also been investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Also, the X-ray photoelectron spectroscopy (XPS) has been used to identify the oxidation state of SNDs. In addition, the catalytic activity of the as-prepared SNDs samples at 200 mM AgNO(3) aqueous solution was evaluated by a redox reaction of p-nitrophenol in the presence of an excess amount of NaBH(4). It was found that the highly symmetrical SNDs with roughly 60-120 nm in stem and branch diameter and 3-12 µm in length obtained after 120 s reaction time do have higher catalytic activity than other SNDs prepared at different reaction time, several times stronger catalytic activity in the sodium borohydride reduction of p-nitrophenol to p-aminophenol, compared to some other silver nanoparticles reported in literature. The crystallinity provided by X-ray diffraction (XRD) analysis indicates that the improvement of the crystallinity is also very crucial for SNDs' catalytic activities. The SNDs are very promising catalytic candidates for the reduction of p-nitrophenol because of easily simple preparation route and high catalytic activity.

Convenient synthesis of silver nanowires with adjustable diameters via a solvothermal method.

Silver nanowires have been successfully synthesized via a simple solvothermal method by adding sodium sulfide (Na(2)S) into the solution. The Ag(2)S colloids produced in the initial stage help reduce the concentration of free Ag(+) ions in the initial formation of silver seeds and subsequently release Ag(+) ions to the solution. Otherwise, there is no oxidative etching owing to the absence of oxygen. In these cases, silver nanowires are grown preferentially. Furthermore, silver nanowires with adjustable diameters can be obtained by adjusting the concentration of Na(2)S. Electron microscopy, X-ray diffraction, and absorption spectra have been used to investigate the products, and a mechanism is proposed to interpret the controlled synthesis of silver nanowires. Finally, our results indicate that this approach provides a versatile route to prepare silver nanowires with controllable diameters.

Convenient, rapid synthesis of silver nanocubes and nanowires via a microwave-assisted polyol method.

Silver nanostructures have been synthesized via a microwave-assisted polyol method by adding sodium sulfide (Na(2)S) into the solution. An interesting morphology evolution can be observed by adjusting the concentration of Na(2)S and the heating power. It is found that the ideal concentration of Na(2)S is 31.25-500 microM for the fast reduction of Ag(+) at 300 W under optimal conditions for producing monodispersed silver nanocubes. When the heating power is increased to 400 W, 62.5-250 microM is the ideal concentration of Na(2)S for the synthesis of silver nanocubes. On increasing the concentration of Na(2)S (>500 microM), a mixture of silver nanowires, nanocubes, bipyramids, and irregular/quasispherical particles is synthesized at 300 and 400 W. In particular, an increase in the concentration of Na(2)S to 750 microM at 400 W leads to the production of a quantity of silver nanowires. In addition, silver nanocubes with controllable sizes can be obtained by changing the concentration of Na(2)S and the heating power. Compared to traditional wet-chemical methods, this method has the advantage of a marked decrease in reaction time to 3.5 min. Finally, our work provides a simple strategy for fabricating silver nanostructures with controllable morphologies and sizes.

[Controllable synthesis and UV-Vis spectral analysis of silver nanoparticles in AOT microemulsion].

Colloidal silver nanoparticles were synthesized in water-in-oil microemulsion using silver nitrate solubilized in the water core of a microemulsion as source of silver ions, hydrazine hydrate solubilized in the water core of another one as reducing agent, cyclohexane as the continuous phase, and sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as the surfactant. The main factors affecting the formation of silver nanoparticles were systematically studied. Ultraviolet-visible (UV-Vis) spectra were used for analyzing the effects of reaction parameters, including the type of reducing agents, the molar ratio of water to surfactant and the concentration of AgNO3 and AOT and so on, on the formation of silver nanoparticles. Original results for the controllable synthesis of silver nanoparticles were obtained when the synthesis proceeded in AOT-cyclohexane-AgNO3 microemulsion. The UV-Vis spectra of silver sols formed in the microemulsion with various parameters were studied systematically. The results show that the amount and average size of the obtained nanoparticles obviously depend on the above parameters. When the concentration of AgNO3 is lower, smaller silver nanoparticles are easy to form by increasing the concentration of AgNO3 appropriately. The higher W value was found to form larger numbers of silver nanoparticles with larger particle size. Compared to the solubility of NaBH4 in AOT reverse micelles, hydrazine hydrate is well soluble in these micelles, and thus it is favorable to reduce the silver ions solubilized in the water core of AOT-cyclohexane-AgNO3 microemulsion. The increase in the concentration of AOT induces an increase in the number of AOT micelles and a decrease in the molar ratio of water to surfactant. As a result, the solubilization capacity of reactants in the micelles increases and the radii of the micelles decrease. That is to say, with the increase in AOT concentration, the amount of the formed nanoparticles increases and the average size of the particles decreases.

The synthesis of MP-CDCA conjugates and dissolution kinetics of model cholesterol gallstones.

The comb-like copolymers of polycarboxylic acid were synthesized and then reacted with chenodeoxycholic acid (CDCA) to obtain a series of conjugates, MPn-CDCA, where n is the number of the groups of oxyethylene in each graft chain. This was confirmed by infrared spectroscopy and thin-layer chromatography. We investigated the effects of dissolving model cholesterol gallstones with the MPn-CDCA conjugates in phosphate-buffered saline at pH 7.4. The dissolution rates of CDCA, MP40-CDCA, MP30-CDCA, MP20-CDCA and MP10-CDCA were 5.33, 5.717, 17.59, 6.868 and 9.615x10(-7)kgm(-2)s(-1), micellar solubilities were 0.2431, 3.095, 12.972, 5.248 and 5.790kgm(-3) and total resistances were 5.33, 5.717, 17.59, 6.868 and 9.615x10(-7)kgm(-2)s(-1), respectively. These studies suggested that the interfacial resistance was the dominant rate-determining factor in dissolving model cholesterol gallstones. Model cholesterol gallstones could be more effectively dissolved by increasing the steric interactive potential energy of side chains and ensuring that the hydrophilic-lipophilic properties of MP-CDCA are within an appropriate range. The micellar dissolution rates of model cholesterol gallstones by MP20-CDCA were significantly faster than by the other conjugates.

Preparation of silver nanoparticles in water-in-oil AOT reverse micelles.

Colloidal silver nanoparticles were synthesized in AOT microemulsions. The effects of the precursors' concentration and the molar ratios of water to AOT on the particle size and size distribution were investigated. UV-vis spectra showed that the Ag+4 intermediates formed at low N2H4 concentration. TEM micrographs confirmed that the silver nanoparticles are all spherical with mean diameters in the range 2-5 nm and have a narrow size distribution. Not only the particle size but also the size distribution was increasing with the W value. The silver colloid has favorable stability and can be preserved for a long time without precipitation.