Degradation of Levofloxacin by a green zero-valent iron-loaded carbon composite activating peroxydisulfate system: Reactivity, products and mechanism.

In this study, a green zero-valent iron-loaded carbon composite (ZVI-SCG) was synthesized using coffee grounds and FeCl3 solution through two-steps method, and the synthesized ZVI-SCG was used in the activation of peroxydisulfate (PDS) to degrade Levofloxacin (LEX). Results revealed that ZVI-SCG exhibited a great potential for LEX removal by adsorption and catalytic degradation in the ZVI-SCG/PDS system, and 99% of LEX was removed in the ZVI-SCG/PDS system within 60 min. ZVI-SCG/PDS system showed a high reactivity toward LEX degradation under realistic environmental conditions. Also, the ZVI-SCG/PDS system could effectively degrade several quinolone antibiotics including gatifloxacin, ciprofloxacin and LEX in single and simultaneous removal modes. A potential reaction mechanism of LEX degradation by ZVI-SCG/PDS system was proposed, SO4•-, HO•, O2•- and 1O2 involved in radical and non-radical pathways took part in catalytic degradation of LEX by ZVI-SCG/PDS system, but HO• might be the main reactive species for LEX degradation. The possible degradation pathway of LEX was also proposed based on the identified ten intermediate products, LEX degradation was successfully achieved through decarboxylation, opening ring and hydroxylation processes. The potential toxicity of LEX and its oxidation products decreased significantly after treatment. This study provides a promising strategy of water treatment for the antibiotics-containing wastewater.

Three-dimensional heterogeneous electro-Fenton system with reduced graphene oxide based particle electrode for Acyclovir removal.

New pollutant pharmaceutical and personal care products (PPCPs), especially antiviral drugs, have received increasing attention not only due to their increase in usage after the outbreak of COVID-19 epidemics but also due to their adverse impacts on water ecological environment. Electro-Fenton technology is an effective method to remove PPCPs from water. Novel particle electrodes (MMT/rGO/Fe3O4) were synthesized by depositing Fe3O4 nanoparticles on reduced graphene oxide modified montmorillonite and acted as catalysts to promote oxidation performance in a three-dimensional Electro-Fenton (3D-EF) system. The electrodes combined the catalytic property of Fe3O4, hydrophilicity of montmorillonite and electrical conductivity of graphene oxides, and applied for the degradation of Acyclovir (ACV) with high efficiency and ease of operation. At optimal condition, the degradation rate of ACV reached 100% within 120 min, and the applicable pH range could be 3 to 11 in the 3D-EF system. The stability and reusability of MMT/rGO/Fe3O4 particle electrodes were also studied, the removal rate of ACV remained at 92% after 10 cycles, which was just slightly lower than that of the first cycle. Potential degradation mechanisms were also proposed by methanol quenching tests and FT-ICR-MS.

An ultra sensitive and rapid SERS detection method based on vortex aggregation enhancement effect for anti-infective drug residues detection in water.

The environmental pollution and human health risks caused by anti-infective residual drugs in the environment have attracted much attention. More convenient and effective detection methods to achieve the rapid and high sensitivity detection for such pollutants are required. In this work, a novel surface-enhanced Raman scattering (SERS) strategy based on vortex aggregation of AgNPs was proposed for the detection of anti-infective drugs in environmental water. The method enhanced the Raman signal of the targets by 2-7.4 times. The mechanism of aggregation enhancement effect under the low-frequency oscillation procedure which significantly enhanced the SERS signal of targets molecular on the aggregated AgNPs was revealed by UV-vis and ICP-MS methods. Three drugs of cefazolin sodium, pefloxacin, and chloroquine phosphate were determined. The detect limits were 3.97 × 10-9 mol/L, 2.42 × 10-10 mol/L, and 7.34 × 10-9 mol/L for cefazolin sodium, pefloxacin, and chloroquine phosphate, respectively. The quantitative relationships were obtained in a wide linear range of 4-5 orders as well as good accuracy and stability with the recoveries of 84.0%-97.1% and the relative standard deviations (RSDs) less than 4.6% for spiked in actual water samples. This method also had excellent repeatability and stability, which have potential application for rapid detection of trace pollutants in water environment.

One Step Synthesis of Tetragonal-CuBi2O4/Amorphous-BiFeO3 Heterojunction with Improved Charge Separation and Enhanced Photocatalytic Properties.

Tetragonal CuBi2O4/amorphous BiFeO3 (T-CBO/A-BFO) composites are prepared via a one-step solvothermal method at mild conditions. The T-CBO/A-BFO composites show expanded visible light absorption, suppressed charge recombination, and consequently improved photocatalytic activity than T-CBO or A-BFO alone. The T-CBO/A-BFO with an optimal T-CBO to A-BFO ratio of 1:1 demonstrates the lowest photoluminescence signal and highest photocatalytic activity. It shows a removal rate of 78.3% for the photodegradation of methylene orange under visible light irradiation for 1 h. XPS test after the cycle test revealed the reduction of Bi3+ during the photocatalytic reaction. Moreover, the as prepared T-CBO/A-BFO show fundamentally higher photocatalytic activity than their calcinated counterparts. The one-step synthesis is completed within 30 min and does not require post annealing process, which may be easily applied for the fast and cost-effective preparation of photoactive metal oxide heterojunctions.

A rapid analytical method for the quantitative determination of the sugar in acarbose fermentation by infrared spectroscopy and chemometrics.

In this article, a rapid analytical method for the quantitative determination of the glucose and maltose in the industrial acarbose fermentation was established by the combination application of infrared spectroscopy and chemometrics. The spectra of the 398 acarbose samples were collected by a portable infrared fast analyzer and the concentration of the glucose and maltose in the acarbose fermentation solution were determinate by high performance liquid chromatography (HPLC) as the referent database. Four spectral pretreatment methods, first derivative (FD), second derivative (SD), Savitzky-Golay (SG) convolution smoothing and mean center (MC) were employed to eliminate the optical interference from background and other noise information. The best result was obtained with FD+SG(21, 3)+MC method. The effects of different principal component numbers (PCs) on the parameters were also optimized. Two models of PLS and MLR, were used to predict the concentration of the glucose and maltose. The FD+SG(21, 3)+MC method was chosen as best method, with 12 PCs for glucose and 11 for maltose as optimized parameters. The PLS model was significantly better than the MLR model. Furthermore, both the predicted values and the reference values of glucose and maltose models showed superior linear relationship within the calibration range. The absolute errors of the predicted values and their corresponding reference values of glucose and maltose in the PLS model were within ±0.14 and ±0.35 confidence intervals, respectively. The prediction correct rate was 98.3%, which indicated that the prediction results of model were excellent.

The fabrication of paper separation channel based SERS substrate and its recyclable separation and detection of pesticides.

In this article, a modified paper separation channel SERS substrate was fabricated by a pen writing method for the simultaneous separation and detection of thiuram and dimethoate. The hydrophilic channel was fabricated with both sides of hydrophobic barrier by the Alkylketene dimer (AKD) modified paper substrate, of which the flow dynamic was well conformed to the Lucas-Washburn model and could be used to separate pesticides effectively. As modified by Ag nanoparticles (AgNPs) and ZnO nanoparticles (ZnONPs), the hydrophilic channel exhibited high recyclable SERS detection activity and stability. The separation and detection performance with different target proportion, channel width and sample volume were studied in detail, which have significant influence on the diffusion process. Additionally, the Raman detects intensity on the substrate also showed linear relationship from 100 to 1000 µg/L. The calculated limit of detects (LODs) under optimal experimental conditions were 54.57 and 19.16 µg/L for dimethoate and thiuram, respectively. Due to the loading of ZnONPs, the substrate could be used repeatably with good stability. The convenient preparation, effective separation and repeatability make this paper based separation channel SERS substrate have great potential application on the fast separation and simultaneous detection of various pesticides in complex field.

The fabrication of a covalent triazine-based organic framework for the solid-phase extraction of fourteen kinds of sulfonamides from meat samples.

A novel covalent triazine-based organic framework (CTF), SCAU-2, was fabricated and used as an adsorbent for the solid-phase extraction of fourteen kinds of sulfonamides (SAs) from meat. Another CTF, SCAU-1, was adopted as a comparison material, as it has a similar motif. A series of structural characterization steps was carried out on the synthesized materials and several parameters were investigated during the extraction process, including the amount of adsorbent, the dilution ratio, the pH of the sample, and the washing and elution solvents. After detection with UHPLC-Q/TOF-MS/MS, the results revealed that SCAU-2 showed high extraction efficiencies towards the selected SAs. The LOD values are from 0.05 to 0.54 ng g-1, and the recoveries are from 84.1% to 91.9%, with RSDs ranging from 3.2% to 4.8% for SCAU-2 when spiked at 50 ng g-1. The results demonstrated that the proposed method has good applicability for the determination of SAs in complicated samples.

Exploration of a novel triazine-based covalent organic framework for solid-phase extraction of antibiotics.

Covalent organic frameworks (COFs) are a new class of porous materials with a large surface area and potential superiority in sample pretreatment. Herein a novel triazine-based COF named SCAU-1 was fabricated via a hydrothermal method, and SNW-1 was also prepared as a contrastive COF material. After characterization, SCAU-1 was used as solid-phase extraction (SPE) adsorbent to concentrate five sulfanilamides (SAs) and four tetracyclines (TCs). Several parameters were investigated in the extraction process, including the amount of adsorbent, the flow rate, the washing and elution solvent, the loading capacity and breakthrough volume. After detected by UPLC-MS/MS, the results revealed that SCAU-1 showed high extraction efficiency towards the selected antibiotics. According to the comparison with SNW-1, SCAU-1 showed better performance for the adsorption of TCs. While for SAs, the recoveries of SCAU-1 is close to that of SNW-1. The LODs are from 0.031 to 0.55 µg L-1, and the recoveries are from 88.0% to 93.4% for SCAU-1 with the RSDs ranging from 2.5% to 4.8%. The results demonstrated that SCAU-1 is a kind of promising adsorbent for the enrichment of organic pollutants.

Short-Time Hydrothermal Synthesis of CuBi2O4 Nanocolumn Arrays for Efficient Visible-Light Photocatalysis.

In this article, a short-time hydrothermal method is developed to prepare CuBi2O4 nanocolumn arrays. By using Bi(NO3)3·5H2O in acetic acid and Cu(NO3)2·3H2O in ethanol as precursor solutions, tetragonal CuBi2O4 with good visible light absorption can be fabricated within 0.5 h at 120 °C. Tetragonal structured CuBi2O4 can be formed after 15 min hydrothermal treatment, however it possesses poor visible light absorption and low photocatalytic activity. Extending the hydrothermal treatment duration to 0.5 h results in a significant improvement invisible light absorption of the tetragonal CuBi2O4. The CuBi2O4 obtained through 0.5 h hydrothermal synthesis shows a band gap of 1.75 eV and exhibits the highest photocatalytic performance among the CuBi2O4 prepared with various hydrothermal time. The removal rate of methylene blue by the 0.5 h CuBi2O4 reaches 91% under visible light irradiation for 0.5 h. This study proposes a novel strategy to prepare photoactive CuBi2O4 nanocolumn arrays within 0.5 h at a moderate temperature of 120 °C. The hydrothermal method provides a facile strategy for the fast synthesis of metal-oxide-based photocatalysts at mild reaction conditions.

The preparation of a flexible AuNP modified carbon cloth electrode and its application in electrochemical detection of Hg(ii) by continuous flow in environmental water.

In this article, a carbon cloth composite electrode modified with gold nanoparticles (AuNPs) was prepared by a facile in situ electrodeposition method and applied to the detection of mercury ions in water. With the optimized electrochemical detection conditions and methods, the limit of detection (LOD) was 0.6 µg L-1 with the linearity ranging from 2 to 200 µg L-1 by the SWSV detection method, and the electrode showed good repeatability after many cycles. Based on this detection method, a continuous flow electrochemical detection system was constructed and applied to the detection of Hg ions in environmental water samples. The standard addition experimental results of two real water samples with an addition level of 10 and 50 µg L-1 showed that the recoveries were between 92.4% and 108.9% with RSDs from 2.01% to 3.22%. These results showed the same performance as that of the ZAAS mercury detection method (recovery: 94-102.4%, RSD 2.09-5.4%). Compared with other electrode materials, a shorter detection time, a wider linear range and high stability with a similar LOD can be achieved by a continuous flow detection method by using the composite electrode. The established continuous flow electrochemical detection system would have promising application in online and real-time detection of heavy metals in environmental water.

MRI Contrast Agents Based on Conjugated Polyelectrolytes and Dendritic Polymers.

Three complexes of gadolinium-based on dentritic molecules are reported as magnetic resonance imaging (MRI) contrast agents. Their ligands feature four carboxylate groups, which contribute to good water solubility and a strong combination with metal ions. As a new attempt, coupling polymerization is carried out to make a combination of conjugated polyelectrolytes and dendrimers for MRI contrast agents. For comparison, mononuclear and binuclear complexes are also reported. The investigation suggests that the contrast agent with the newly designed macromolecular skeleton provides higher longitudinal relaxivity value (36.2 mm -1 s-1 ) and more visible enhancement in in vivo and in vitro MR images than the small molecular ones. In addition, extremely low cytotoxicity and main clearance via hepatobiliary are confirmed, which reduces the deterioration of chronic kidney disease. All the results indicate that these three complexes are generally applicable as promising clinical contrast agents.

Fabrication of Metal-Organic Framework MOF-177 Coatings on Stainless Steel Fibers for Head-Space Solid-Phase Microextraction of Phenols.

Direct head-space solid-phase microextraction (HS-SPME) of phenols in water is usually difficult due to its polarity and solubility in aqueous matrix. Herein we report the fabrication of metal-organic framework MOF-177 coated stainless steel fiber for the HS-SPME of phenols (2-methylolphenol, 4-methylolphenol, 2,4-dimethylolphenol, 2,4-dichlorphenol, and 3-methyl-4-chlorophenol) in environmental water samples prior to the gas chromatography-mass spectrometry detection. Several parameters affecting the extraction efficiency were optimized in the experiment, including extraction temperature and time, the pH value and salt addition. The results indicated that the coated fiber gave low detection limits (0.015-0.043 µg L-1) and good repeatability with the RSD ranging from 2.8% to 5.5% for phenols. The recoveries are between 84.5%-98.6% with the spiked level of 10 µg L-1 for the real water samples. The established method may afford a kind of potential enrichment material and a reference method for the analysis of methylphenols in water samples.

Exploration of metal-organic framework MOF-177 coated fibers for headspace solid-phase microextraction of polychlorinated biphenyls and polycyclic aromatic hydrocarbons.

Metal-organic frameworks (MOFs) have received much attention in analytical science for their large langmuir surface and high thermostability. Herein MOF-177-coated solid-phase micro-extraction (SPME) fibers were fabricated on etched stainless steel by an adhensive method, and applied to the enrichment of polychlorinated biphenyls (PCB01, PCB05, PCB29, PCB47, PCB98, PCB154, PCB171, PCB201) and polycyclic aromatic hydrocarbons (ANY, ANA, FLU, PHE, ANT, FLT, PYR) from environmental water samples. Several parameters affecting the extraction efficiency were optimized prior to the gas chromatography-mass spectrometry analysis, including extraction temperature and time, desorption time, stirring rate and salt addition. The results indicated that the coated fiber gave low detection limits (0.69-4.42 ng L(-1)) and good repeatability with the RSD ranging from 1.47% to 8.67% for PCBs and PAHs. The recoveries were between 81.8% and 113% with the spiked level of 10 ng L(-1) for the real water samples. Besides, the MOF-177 coated fiber was stable enough over 100 extraction cycles and the RSD for fiber-to- fiber reproducibility was less than 9.82% during the experiment.

[Distribution Characteristics of Heavy Metals in Environmental Samples Around Electroplating Factories and the Health Risk Assessment].

This study aimed to investigate the pollution degree and human health risk of heavy metals in soil and air samples around electroplating factories. Soil, air and waste gas samples were collected to measure 8 heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in two electroplating factories, located in Baiyun district of Guangzhou city. Geoaccumulation index and USEPA Risk Assessment Guidance for Superfund (RAGS) were respectively carried out. Results showed that concentrations of Hg and Pb in waste gas and Cr in air samples were higher than limits of the corresponding quality standards, and concentrations of Cd, Hg and Zn in soil samples reached the moderate pollution level. The HQ and HI of exposure by heavy metals in air and soil samples were both lower than 1, indicating that there was no non-carcinogen risk. CRAs and CRCr in soil samples were beyond the maximum acceptable level of carcinogen risk (10(-4)), and the contribution rate of CRCr to TCR was over 81%. CRCr, CRNi and TCR in air samples were in range of 10(-6) - 10(-4), indicating there was possibly carcinogen risk but was acceptable risk. CR values for children were higher than adults in soils, but were higher for adults in air samples. Correlation analysis revealed that concentrations of heavy metals in soils were significantly correlated with these in waste gas samples, and PCA data showed pollution sources of Cd, Hg and Zn in soils were different from other metals.

[Characteristics of speciation and evaluation of ecological risk of heavy metals in sewage sludge of Guangzhou].

Contents of heavy metals in different sewage sludges were analyzed and the speciation distribution and bioavailability of heavy metals were investigated, and the risk assessment code (RAC) and toxicity characteristic leaching procedure for solid waste were used to evaluate the potential ecological risk and leaching toxicity risk of heavy metals in sludge samples, respectively. The results showed that contents of Cu, Cr, Pb and Zn were high and presented a great difference by different sources in sewage sludges. Most of heavy metals existed in non-residual fractions and percentages of the mobile fraction (acid soluble fraction) of heavy metals in acidic sludge were higher. According to the results of single extraction, 1 mol x L(-1) NaOAc solution (pH 5.0) and 0.02 mol x L(-1) EDTA + 0.5 mol x L(-1) NH4OAc solution (pH 4.6) were suitable for evaluating bioavailable heavy metals in acidic and alkaline sludge, respectively. Percentages of bioavailable heavy metals were higher with the stronger of sludge acidity. The mobile ability of heavy metals resulted in the high ecological risk of sludge samples, and the bioavailability of heavy metals caused acidic sludges with a very high ecological risk but alkaline sludges with the middle ecological risk. Leaching toxicity risk was very high in sludge samples except domestic sewage sludge. After the removal of bioavailable heavy metals, leaching toxicity risk of sludge samples was still high in spite of its decrease; however, part type of sludges could be implemented landfill disposal.

A two-dimensional network containing an -Mn-O-C-O-Mn- chain: poly[diaqua[1,2-bis(pyridin-4-yl)ethylene][µ3-3-carboxy-5-(carboxylatomethoxy)benzoato]manganese(II)].

In the title compound, [Mn(C10H6O7)(C12H10N2)(H2O)2]n or [Mn(HOABDC)(bpe)(H2O)2]n [H3OABDC is 5-(carboxymethoxy)isophthalic acid and bpe is 1,2-bis(pyridin-4-yl)ethylene], each Mn(II) cation is at the centre of a distorted octahedron formed by three carboxylate O atoms from three different HOABDC(2-) ligands, one pyridyl N atom from the terminal bpe ligand and two water molecules. The flexible oxyacetate group bound to a methylene C atom of the HOABDC(2-) ligand links the Mn(II) centres into -Mn-O-C-O-Mn- chains, and the carboxylate group bound directly to the benzene ring extends the chains into two-dimensional layers which lie parallel to the (010) plane and present herringbone patterns. Intermolecular O-H...N and C-H...O hydrogen bonds connect the layers into a three-dimensional supramolecular structure.

A fourfold interpenetrating diamondoid three-dimensional coordination polymer: poly[[[µ2-1,2-bis(pyridin-4-yl)ethene-κ2N:N'](µ2-5-hydroxyisophthalato-κ2O1:O3)zinc(II)] 1,2-bis(pyridin-4-yl)ethene hemisolvate].

In the title compound, {[Zn(C8H4O5)(C12H10N2)]·0.5C12H10N2}n or {[Zn(HO-BDC)(bpe)]·0.5bpe}n [HO-H2BDC is 5-hydroxyisophthalic acid and bpe is 1,2-bis(pyridin-4-yl)ethene], the asymmetric unit contains a Zn(II) atom, one HO-BDC ligand, one coordinated bpe ligand and half a noncoordinating bpe molecule with crystallographic inversion symmetry. Each Zn(II) centre is four-coordinated by two O atoms from two distinct HO-BDC ligands and two N atoms from two different bpe ligands in a ZnO2N2 coordination environment. The three-dimensional topology of the title compound corresponds to a fourfold interpenetrating diamondoid coordination polymer network, with the uncoordinated bpe ligands located in the cavities, hydrogen bonded to the main network via the hydroxy group of the HO-H2BDC ligand.

Rare-earth-doped bifunctional alkaline-earth metal fluoride nanocrystals via a facile microwave-assisted process.

Rare-earth-doped magnetic-optic bifunctional alkaline-earth metal fluoride nanocrystals have been successfully synthesized via a facile microwave-assisted process. The as-prepared nanocrystals were monodisperse and could form stable colloidal solutions in polar solvents, such as water and ethanol. They show bright-green fluorescence emisson. Furthermore, Gd(3+)-doped ones exhibit paramagnetic behavior at room temperature and superparamagnetic behavior at 2 K.

Microwave-assisted synthesis of hydrophilic BaYF5:Tb/Ce,Tb green fluorescent colloid nanocrystals.

Hydrophilic Ce, Tb doped BaYF(5) nanocrystals with uniform size were synthesized by a microwave-assisted route. The synthesized nanocrystals can be well dispersed in hydrophilic solutions (DMSO, DMF, EG, H(2)O). This synthesis procedure represents a less time consuming method, with high product yield and without using any assistant or/and template reagents, which may be expected to be a general method for rapid synthesis of other hydrophilic RE doped fluoride fluorescent nanocrystals. The Ce(3+), Tb(3+) codoped BaYF(5) nanocrystals show bright green fluorescence emission. The Ce(3+) acts as an effective energy transfer medium and the emission at the high (5)D(3) energy level of Tb is enhanced in this host material.

Near-infrared luminescent copolymerized hybrid materials built from tin nanoclusters and PMMA.

Novel near-infrared (NIR) luminescent copolymerized hybrid materials were prepared by covalently grafting and physically doping Ln complexes (Ln = Er, Sm, Yb, and Nd) into a copolymer matrix built from nanobuilding blocks. The structures of the obtained hybrid materials were investigated by Fourier transform infrared (FTIR) spectra, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). In the photoluminescence studies, the hybrid materials showed characteristic NIR luminescence of corresponding Ln(3+) ions through intramolecular energy transfer from ligands to Ln(3+) ions. Transparent films of these materials can be easily prepared through spin-coating on indium tin oxide (ITO) glasses taking advantage of the matrix nature.