Chuanhai Xia

The Pd-catalyzed hydrodechlorination of chlorophenols in aqueous solutions under mild conditions: A promising approach to practical use in wastewater

Catalytic hydrotreating of chlorophenols was carried out in water with Pd/C at 25 degrees C under atmospheric pressure. 1.0% (w/w) monocholophenols was completely dechlorinated within 60 min. Phenol, cyclohexanone and cyclohexanol were formed. In contrast to the dechlorination of monochlorophenols, the hydrogenation reaction of polychlorinated phenols became difficult and reaction rates were strongly dependent upon the number of the chlorine atoms. The solvent property had a considerably important influence on the dechlorination reaction. Water as a solvent showed more advantages than organic solvents. It was much easier to be hydrodechlorinated for chlorophenols in aqueous solutions. However, the presence of THF, dioxane, DMSO or DMF in water was disadvantageous to the reaction and easily to cause Pd/C deactivation. Additionally, when different halogenated organic compounds were present in aqueous solution, the dehalogenation reaction was the competitive hydrogenation process.

Preliminary enrichment and separation of chlorogenic acid from Helianthus tuberosus L. leaves extract by macroporous resins

In the present study, a simple and efficient method for the preparative separation of 3-CQA from the extract of Helianthus tuberosus leaves with macroporous resins was studied. ADS-21 showed much higher adsorption capacity and better adsorption/desorption properties for 3-CQA among the tested resins. The adsorption of 3-CQA on ADS-21 resin at 25°C was fitted best to the Langmuir isotherm model and pseudo-second-order kinetic model. Dynamic adsorption/desorption experiments were carried out in a glass column packed with ADS-21 to optimise the separation process of 3-CQA from H. tuberosus leaves extract. After one treatment with ADS-21, the content of 3-CQA in the product was increased 5.42-fold, from 12.0% to 65.2%, with a recovery yield of 89.4%. The results demonstrated that the method was suitable for large-scale separation and manufacture of 3-CQA from H. tuberosus leaves.

The activity and selectivity of catalytic peroxide oxidation of chlorophenols over Cu–Al hydrotalcite/clay composite

Liquid phase catalytic oxidation of chlorophenols (CPs) was carried out over Cu-Al hydrotalcite/clay composite at ambient temperature and pressure using hydrogen peroxide as oxidant. The results showed that the catalyst had high catalytic activity, with complete oxidation of 4-CP within 40 min at 40 °C. The content and position of chlorine on the aromatic ring had significantly different effects on the oxidation rate of CPs, with the rate sequence of phenol > monochlorophenol (MCP) > dichlorophenol (DCP) > trichlorophenol (TCP), 3-CP > 2-CP > 4-CP, and 3,5-DCP > 3,4-DCP > 2,5-DCP > 2,4-DCP > 2,6-DCP. This was ascribed to the interactions among σ-electron withdrawing conductive effect, π-electron donating conjugative effect, and steric hindrance effect of chlorine. It was evidenced that the catalytic peroxide oxidation of CPs in the first step was selective and rate-limiting, where chlorinated 1,4-benzoquinones formed.

Two new withanolides from the halophyte Datura stramonium L.

Eight steroids, including five withanolides (1–5) and three other ergostane-type steroids (6–8), were isolated from the aerial parts of the halophyte Datura stramonium L., which were collected from the Yellow River Delta in China. Their structures were elucidated on the basis of extensive spectroscopic methods, especially 1D and 2D NMR techniques. Compounds 1 and 2 were new compounds and characterised as (22R)-27-hydroxy-7α-methoxy-1-oxowitha-3,5,24-trienolide and its 27-O-β-d-glucopyranoside. Compound 3 was a new natural product and identified as (22R)-27-hydroxy-1-oxowitha-2,5,24-trienolide and isolated from nature for the first time.

Combination of hydrodechlorination and biodegradation for the abatement of chlorophenols

A method for abatement for chlorophenols (CPs) in contaminated water based on successive steps of catalytic hydrodechlorination (HDC) over Pd/C at ambient temperature and pressure, followed by aerobic biodegradation using yeast Candida tropicalis (C. tropicalis) was studied. The results showed that 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) could be easily and completely dechlorinated under mild conditions, ultimately yielding phenol as product. Subsequently, phenol (0-900 mg L(-1)) could be completely degraded by C. tropicalis within 30 h. Moreover, during the biodegradation of phenol, definite mass of ethanol (≤0.5%) caused a modest increase in the duration of the lag phase, but led to a great increase in the maximum degradation rates. This means that CPs with higher concentration could be efficiently detoxified under mild conditions by a combination of HDC and biodegradation in water or water-ethanol systems.

The possible role of bacterial signal molecules N-acyl homoserine lactones in the formation of diatom-biofilm (Cylindrotheca sp.)

Bacterial quorum sensing signal molecules N-acyl homoserine lactones (AHLs) (C10-HSL, 3-OXO-C10-HSL and 3-OH-C10-HSL) as possible chemical cues were employed to investigate the role in the formation of fouling diatom-biofilm (Cylindrotheca sp.). Results showed that AHLs promoted Chlorophyll a (Chl.a) and extracellular polymeric substance (EPS) contents in the diatom-biofilm. In the presence of AHLs-inhibitor 3, 4-Dibromo-2(5)H-furanone, which was used to avoid the possible interference of AHLs from bacteria, AHLs also increased the Chl.a and EPS contents. Scanning electron microscope and confocal laser scanning microscope analysis further demonstrated that AHLs promoted the formation of the diatom-biofilm. Non-invasive micro-test technique showed that AHLs promoted Ca(2+) efflux in Cylindrotheca sp., which implied that Ca(2+) might be correlated with AHLs-induced positive effect on the formation of diatom-biofilm. This study provides direct evidences that AHLs play an important role in developing the diatom-biofilm and AHLs-inhibitors might be promising active agents in marine antifouling.

Ecotoxicity and Preliminary Risk Assessment of Nonivamide as a Promising Marine Antifoulant

The unclear environmental performance of nonivamide limits its application as a marine antifoulant. In this study, the natural degradation of nonivamide was studied in seawater and tap water. The half-life was 5.8 d, 8.8 d, 12.2 d, and 14.7 d in seawater and tap water in photolysis and biolysis, respectively. Furthermore, the ecotoxicity of nonivamide was assessed using marine microalgae, Chlorella vulgaris and Platymonas sp.; values on the growth of Chlorella vulgaris and Platymonas sp. were 16.9 mg L−1 and 19.21 mg L−1, respectively. The toxicity and environmental risk of nonivamide on microalgae were significantly decreased due to the natural degradation in seawater.

A new minor diketopiperazine from the sponge-derived fungus Simplicillium sp. YZ-11

Chemical investigation of the cultures of a sponge-derived fungus Simplicillium sp. YZ-11 led to the isolation of a new minor diketopiperazine alkaloid cyclo-(2-hydroxy-Pro-Gly) (1) and a natural lactone (S)-dihydro-5-[(S)- hydroxyphenylmethyl]-2(3H)-furanone (2), together with five known ergostane-type sterols (3–7). Their structures were established based on extensive spectroscopic methods (1H and 13C NMR, 1H-1H COSY, HSQC and HMBC) and optical rotation analysis.

Metal fluoride promoted catalytic hydrogenation of aromatic nitro compounds over RANEY® Ni

The catalytic hydrogenation reactivity of aromatic nitro compounds over RANEY (R) Ni was substantially improved when a moderate amount of metal fluoride (NaF, KF, MgF2, and CaF2) was added into the reaction system.

Seasonal variations in fouling diatom communities on the Yantai coast

Fouling diatoms are a main component of biofilm, and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater, on the Yantai coast, northern Yellow Sea, China, using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3, 7, 14, and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca, Nitzschia, Navicula, Amphora, Gomphonema, and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions, we found that Cylindrotheca grew very fast, which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques.