Electrochemical oxidation and advanced oxidation processes using a 3D hexagonal Co3O4 array anode for 4-nitrophenol decomposition coupled with simultaneous CO2 conversion to liquid fuels via a flower-like CuO cathode.

A novel electrocatalytic system was developed to realize one-pot conversion of organic pollutants into liquid fuels such as methanol (CH3OH) and ethanol (C2H5OH). The process combines the catalytic oxidation of organic pollutants with electrocatalytic reduction of CO2. We first coupled the electrocatalytic process with SO4•--based advanced oxidation processes (AOPs) for the degradation of 4-nitrophenol (4-NP) using a 3D-hexagonal Co3O4 anode. In this step, 4-NP was mineralized to CO2, and then the CO2 was converted to CH3OH and C2H5OH by electrocatalytic reduction using a flower-like CuO cathode. The experimental results show the destruction of 4-NP (60 mL, 10 mg/L) can be as high as 99%. In addition, the yields of CH3OH and C2H5OH were 98.29 µmol/L and 40.95 µmol/L, respectively, which represents a conversion of 41.8% of 4-NP into liquid fuels; the electron efficiency was 73.1%. In addition, we found that 3D-hexagonal arrays of Co3O4 with different morphologies can be obtained by adding different amounts of urea. We also investigated the formation mechanism of novel 3D-hexagonal Co3O4 arrays for the first time. A mechanism was proposed to explain the electrocatalytic steps involved in the conversion of 4-NP to CH3OH and C2H5OH and the synergetic effects between AOPs and electrocatalysis.

Preparation of CeO2-Quantum Dots/Cu2O Nanocomposites with Enhanced Photocatalytic Properties.

To improve the efficiency of photocatalysts, a composite of CeO2-quantum dots/Cu2O (CeO2-QDs/Cu2O) was prepared through a one-step hydrothermal procedure in alkaline carbonate solution with Cu2(OH)2CO3 and Ce(NO3)3. 6H2O as precursors and glucose as reducing agent. The morphologies and structures of the prepared photocatalysts were well characterized utilizing Transmission Electron Microscopy (TEM), X-ray Diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS) and UV-Vis Diffuse Reflectance Spectrophotometer (DRS). The results indicated that the CeO2-QDs with 5 to 10 nm diameters were well dispersed and had a good contact with Cu2O. As observed in the photocatalytic experiments, Rhodamine B could be degraded more effectively under simulated sunlight using CeO2-QDs/Cu2O as the photocatalysts. Also, the obtained photocatalytic kinetics constant was higher than that in the experiments using CeO2 or Cu2O nano particles as photocatalysts. The enhanced photocatalytic activities might be attributed to the efficient separation of photo-generated charge carriers with the help of the p-n heterojunction and the morphology of quantum dots.

Three-Dimensional Reduced Graphene Oxide Coupled with Mn3O4 for Highly Efficient Removal of Sb(III) and Sb(V) from Water.

Highly porous, three-dimensional (3D) nanostructured composite adsorbents of reduced graphene oxides/Mn3O4 (RGO/Mn3O4) were fabricated by a facile method of a combination of reflux condensation and solvothermal reactions and systemically characterized. The as-prepared RGO/Mn3O4 possesses a mesoporous 3D structure, in which Mn3O4 nanoparticles are uniformly deposited on the surface of the reduced graphene oxide. The adsorption properties of RGO/Mn3O4 to antimonite (Sb(III)) and antimonate (Sb(V)) were investigated using batch experiments of adsorption isotherms and kinetics. Experimental results show that the RGO/Mn3O4 composite has fast liquid transport and superior adsorption capacity toward antimony (Sb) species in comparison to six recent adsorbents reported in the literature and summarized in a table in this paper. Theoretical maximum adsorption capacities of RGO/Mn3O4 toward Sb(III) and Sb(V) are 151.84 and 105.50 mg/g, respectively, modeled by Langmuir isotherms. The application of RGO/Mn3O4 was demonstrated by using drinking water spiked with Sb (320 µg/L). Fixed-bed column adsorption experiments indicate that the effective breakthrough volumes were 859 and 633 mL bed volumes (BVs) for the Sb(III) and Sb(V), respectively, until the maximum contaminant level of 5 ppb was reached, which is below the maximum limits allowed in drinking water according to the most stringent regulations. The advantages of being nontoxic, highly stable, and resistant to acid and alkali and having high adsorption capacity toward Sb(III) and Sb(V) confirm the great potential application of RGO/Mn3O4 in Sb-spiked water treatment.

Hydrogen Evolution from Water Coupled with the Oxidation of As(III) in a Photocatalytic System.

A series of heterostructured CdS/Sr2(Nb17/18Zn1/18)2O7-δ composites with excellent photocatalytic ability for simultaneous hydrogen evolution and As(III) oxidation under simulated sunlight were synthesized and characterized. Among them, 30% CdS/Sr2(Nb17/18Zn1/18)2O7-δ (30CSNZO) has the highest in activity, exhibiting a H2 production rate of 1669.1 µmol·h(-1)·g(-1) that is higher than that of many photocatalysts recently reported in the literature. At pH 9, As(III) is completely oxidized to As(V) over 30CSNZO in 30 min of irradiation of simulated sunlight. In the photocatalytic system, H2 production rate decreases with the increase of As(III) concentration, and the recycle experiments show that 30CSNZO exhibits excellent stability, durability, and recyclability for photocatalytic hydrogen evolution and As(III) oxidation. We propose a mechanism in which superoxide radical (·O2(-)) is the active species for As(III) oxidation and the oxidation of As(III) has an effect on hydrogen evolution. For the first time, it is demonstrated that simultaneous hydrogen evolution and arsenite oxidation is possible in a photocatalytic system.

Quality control of medicinal herbs Fructus gardeniae, Common Andrographis Herb and their preparations for their active constituents by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry.

Dehydroandrographolide, andrographolide and geniposide are the main active constituents of many herbal medicines, e.g., Fructus gardeniae, Common Andrographis Herb. They are used as the markers to control the quality of such herbal medicines and their herbal preparations. In this paper, a simple and sensitive high-performance liquid chromatographic (HPLC) method coupled with photodiode array detection (DAD) and electrospray mass spectrometry (ESI/MS) were developed to determine the three compounds simultaneously in extracts of medicinal herbs and herbal preparations produced by different companies. The extracts were separated on a C(18) reversed phase HPLC column, with a gradient solvent system, the time for the separation of the three target analytes was 1 0min. The abundance ions were recorded using selected ion monitoring (SIM) mode with m/z 297.3, 297.3 and 411.1 for dehydroandrographolide, andrographolide and geniposide, respectively. The limit of detection for dehydroandrographolide, andrographolide and geniposide were 20, 30 and 150 ng mL(-1), respectively. The proposed method was successfully applied to the determination of the contents of the compounds in related to medicinal herbs and preparations.

Rapid determination of protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata by microwave-assisted solvent extraction and HPLC-ESI/MS.

An isocratic high-performance liquid chromatographic method coupled with electrospray mass spectrometry was developed to determine protopine, allocryptopine, sanguinarine and chelerythrine in fruits of Macleaya cordata. The sample was extracted with hydrochloric acid aqueous solution using microwave-assisted extraction method. The extracts were separated on a C8 reversed-phase HPLC column with acetonitrile:acetate buffer as mobile phase, and full elution of all analytes was realized isocratically within 10 min. The abundance of pseudomolecule ions was recorded using selected ion recording at m/z 354.4, 370.1, 332.5, 348.5 and 338.5 for protopine, allocryptopine, sanguinarine, chelerythrine and the internal standard, jatrorrhizine, respectively. Internal standard curves were used for the quantification of protopine, allocryptopine, sanguinarine and chelerythrine, which showed a linear range of 0.745-74.5, 0.610-61.0, 0.525-105 and 0.375-75 microg/mL, respectively, with correlation coefficients of 0.9995, 0.9992, 0.9993 and 0.9989, and limits of detection of 3.73, 3.05, 1.60 and 1.11 ng/mL, respectively.

Simultaneous analysis of caffeic acid derivatives and alkamides in roots and extracts of Echinacea purpurea by high-performance liquid chromatography-photodiode array detection-electrospray mass spectrometry.

High-performance liquid chromatography (HPLC) coupled with UV photodiode-array detection and electrospray ionization mass spectrometry was developed for the simultaneous analysis of caffeic acid derivatives and alkamides in the roots and extracts of Echinacea purpurea. Caffeic acid derivatives and alkamides produced very abundant peaks in the total ion current chromatogram during negative and positive cone voltage switching. Cichoric acid and the isomer pair, dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamide, were used as a standard for quantification of caffeic acid derivatives and alkamides in E. purpurea. This novel method surpasses previously published ones in product quality control and providing the HPLC chromatographic fingerprints of biological active components in E. purpurea.