Xue-Gang Chen

Adsorption of Methylene Blue by Rice Hull Ash

Rice hull ash (RHA) is an effective and low-cost adsorbent for water purification. In this study, we systematically investigated the effects of ashing temperature and atmosphere on the physic-chemical characteristics of RHA and its adsorption for methylene blue (MB). XRD, SEM, and BET analyses indicate that all RHA samples are porous materials that consist of carbon and amorphous silica. RHA ashed in nitrogen (BRHA) exhibit higher BET surface areas and lower mesopore fractions than that of ashed in air (WRHA) due to the retention of carbon. The pore volumes and surface area of BRHA increase with ashing temperature, while that of WRHA exhibit a first increase and subsequently decrease. The adsorption kinetics of MB adsorption by RHA fit pseudo-second-order model. The calculated q e values exhibit linear relationships with the mesopore volumes of RHA. The adsorption isotherms fit the Langmuir isotherm rather than the Freundlich equation, indicating the monolayer adsorption of MB. WRHA that ashed at 450°C and BRHA that ashed at 750°C present the highest adsorption capacities for MB with q 0 values of greater than 45 mg g−1. This systematic study will provide essential information on the effects of ashing conditions on the physico-chemical characteristics and dye removal of RHA.

Facile preparation of MnFe2O4/halloysite nanotubular encapsulates with enhanced magnetic and electromagnetic performances

We synthesized novel magnetic nanotubular encapsulates with ferrite nanoparticles embedded into the inner channels of halloysite nanotubes (HNTs) for the first time. The nano-encapsulates with enclosed ferrite nanoparticles show significantly enhanced magnetic and electromagnetic performance when compared to that with external particles.

Stress-driven discovery of a cryptic antibiotic produced by Streptomyces sp. WU20 from Kueishantao hydrothermal vent with an integrated metabolomics strategy

Marine hydrothermal microorganisms respond rapidly to the changes in the concentrations and availability of metals within hydrothermal vent microbial habitats which are strongly influenced by elevated levels of heavy metals. Most hydrothermal vent actinomycetes possess a remarkable capability for the synthesis of a broad variety of biologically active secondary metabolites. Major challenges in the screening of these microorganisms are to activate the expression of cryptic biosynthetic gene clusters and the development of technologies for efficient dereplication of known compounds. Here, we report the identification of a novel antibiotic produced by Streptomyces sp. WU20 isolated from the metal-rich hydrothermal vents in Taiwan Kueishantao, following a strategy based on metal induction of silent genes combined with metabolomics analytical methods. HPLC-guided isolation by tracking the target peak resulted in the characterization of the novel compound 1 with antimicrobial activity against Bacillus subtilis. The stress metabolite 1 induced by nickel is structurally totally different compared with the normally produced compounds. This study underlines the applicability of metal induction combined with metabolic analytical techniques in accelerating the exploration of novel antibiotics and other medically relevant natural products.

An Unusual Conformational Isomer of Verrucosidin Backbone from a Hydrothermal Vent Fungus, Penicillium sp. Y-50-10

A new verrucosidin derivative, methyl isoverrucosidinol (1), was isolated from the marine fungus Penicillium sp. Y-50-10, dwelling in sulfur rich sediment in the Kueishantao hydrothermal vents off Taiwan. The structure was established by spectroscopic means including HRMS and 2D-NMR spectroscopic analysis. The absolute configuration was defined mainly by comparison of quantum chemical TDDFT calculated and experimental ECD spectra. Among hitherto known compounds with a verrucosidine backbone isolated from natural resource, compound 1 represents the first example of a new conformational isomer of its skeleton, exhibiting antibiotic activity against Bacillus subtilis with MIC value 32 μg/mL.

A novel Cu+-doped Li[Fe0.9Cu0.1Li0.1]PO4/C cathode material with enhanced electrochemical properties

LiFePO4 is an effective battery material which has gained global focus. In this study, we prepared a novel Cu+-doped Li[Fe0.9Cu0.1Li0.1]PO4/C cathode material via a carbothermal reduction method using glucose as carbon source. X-ray diffraction (XRD) patterns and Rietveld refinement on the samples are consistent with the orthorhombic phase and showed that the substituting Cu+ ions and excess Li+ ions occupy the Fe sites. The micro-morphology of the samples indicates that Cu+ doping can decrease the particle size and maintain the crystal structure of LiFePO4/C. XP spectra confirmed that the surface oxidation states of Fe and Cu are +2 and +1, respectively. The as-prepared Li[Fe0.9Cu0.1Li0.1]PO4/C composite exhibits enhanced initial discharge capacity (148.8 mA h g−1) compared to the un-doped LiFePO4/C. The discharge capacity remains at 149.8 mA h g−1 after 50 cycles at a rate of 0.2C, which displayed an excellent cycling stability. Furthermore, the cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) results showed that the Cu+-doped LiFePO4/C composite exhibits a higher lithium-ion diffusion coefficient and lower charge transfer resistance than the undoped counterparts. This study presents a novel Cu+-doped LiFePO4/C cathode material with enhanced electrochemical properties, which could be potentially applied as a battery material.

Ecological risk and contamination history of heavy metals in the Andong tidal flat, Hangzhou Bay, China

ABSTRACT In this study, we collected two sediment cores (C1 and C2) from the Andong tidal flat, Hangzhou Bay, and studied the temporal variations of heavy metals in the cores. Vertical distributions of heavy metals were almost unchanged in both the cores before 2000. After 2000, however, the heavy metal concentrations increased dramatically, suggesting that the sediments have been affected by enhanced human pollution in the recent decade. In the core C1, the sediments were severely polluted by Pb, moderately to considerably polluted by Cr and Zn, and low to moderately polluted by other heavy metals. The core C2 was relatively unpolluted before 2000 and low to moderately polluted after 2000. Multi-statistical analyses indicated that the core C1 was additionally contaminated by local human activities such as wastewater discharge and the Hangzhou Bay Bridge. The heavy metals in the core C2, however, were largely contributed by the Yangtze River and controlled by sedimentation process. The calculated sedimentary flux (4–8 g m−2 a−1) of heavy metals generally increased with time. It was closely related to the wastewater discharge in adjacent areas. This study reconstructed the local heavy metal pollution history and provides important information for environmental protection and policy making.

PREPARATION AND MICROWAVE ABSORPTION OF MICRO-FIBROUS Fe/C NANOCOMPOSITE

Wide-band absorption with low density is essential for microwave absorbers. We fabricated a novel micro-fibrous Fe/C nanocomposite with bulk density of only 0.47 ± 0.03 g cm-3 using carbonized cotton fibers as template. Monodisperse iron nanoparticles with diameter of about 100 nm covered on the fibers and significantly increased the complex permittivity and permeability, and therefore enhanced the reflection loss (RL) for electromagnetic waves. The optimum thickness for the nanocomposite is 1.5–1.8 mm, with maximum RL of -14 dB and bandwidth of RL < -5 dB from 10 to 18 GHz, similar to that of Fe/C nanocomposite without using carbonized cotton fibers. Because of its low density and broad bandwidth at thin matching thickness, micro-fibrous Fe/C nanocomposite is a promising light-weight microwave absorber.

Submarine Groundwater Discharge helps making nearshore waters heterotrophic

Submarine groundwater discharge (SGD) is the submarine seepage of all fluids from coastal sediments into the overlying coastal seas. It has been well documented that the SGD may contribute a great deal of allochthonous nutrients to the coastlines. It is, however, less known how much carbon enters the ocean via the SGD. Nutrients (NO3, NO2, NH4, PO4, SiO2), alkalinity and dissolved inorganic carbon (DIC) in the submarine groundwater were measured at 20 locations around Taiwan for the first time. The total N/P/Si yields from the SGD in Taiwan are respectively 3.28 ± 2.3 × 104, 2.6 ± 1.8 × 102 and 1.89 ± 1.33 × 104 mol/km2/a, compared with 9.5 ± 6.7 × 105 mol/km2/a for alkalinity and 8.8 ± 6.2 × 105 mol/km2/a for DIC. To compare with literature data, yields for the major estuary across the Taiwan Strait (Jiulong River) are comparable except for P which is extremely low. Primary production supported by these nutrient outflows is insufficient to compensate the DIC supplied by the SGD. As a result, the SGD helps making the coastal waters in Taiwan and Jiulong River heterotrophic.

Preparation of hollow iron/halloysite nanocomposites with enhanced electromagnetic performances

Nanostructures loaded on halloysite nanotubes (HNTs) have attracted global interest, because the nanotubular HNTs could extend the range of their potential applications. In this study, we fabricated a novel nanocomposite with hollow iron nanoparticles loaded on the surface of HNTs. The structure of the iron nanoparticles can be adjusted by ageing time. Owing to the increased remnant magnetization and coercivity values, the nanocomposites loaded with hollow iron nanoparticles showed better electromagnetic performance than that with solid iron nanoparticles. This study opens a new pathway to fabricate halloysite nanotubular nanocomposites that may gain applications in the catalytic degradation of organic pollutants and electromagnetic wave absorption.

Four Verrucosidin Derivatives Isolated from the Hydrothermal Vent Sulfur-Derived Fungus Penicillium sp. Y-50-10

Four verrucosidin derivatives, penicyrone (1), norpenicyrone (2), methyl norpenicyrone (3), and methyl penicyrone (4) were isolated from the hydrothermal vent sulfur-derived fungus Penicillium sp. Y-50-10. Compounds 1–4 were obtained as a mixture of two epimers. Compounds 2–4 have been proved to be new secondary metabolites. The chemical structures were determined by comparing with literature data and HR-MS and 2D NMR spectroscopic analysis. The migration of the double bond from C8=C9 to C7=C8 in compounds 1–4 allowed the assignment of a rearranged verrucosidin skeleton. Compounds 1–4 showed activity against B. subtilis, with MIC values of 32 μg/mL.