Microbial desulfurization of waste latex rubber with Alicyclobacillus sp.

A microbe with desulfurizing capability, Alicyclobacillus sp., was selected to recycle waste latex rubber (WLR). The growth characteristics of the microorganism and the technical conditions in the co-culture desulfurization process were studied. The desulfurization effect of Alicyclobacillus sp. on the WLR was characterized, and the mechanism for the microbial desulfurization of WLR was tentatively explored. The results showed that adding 5% (w/v) WLR into medium had little effect on the growth of Alicyclobacillus sp. The surfactant polysorbate 80 (Tween 80) had a toxic effect on Alicyclobacillus sp., but the growth of the microbe was vigorous if the proper technique was used: the mixing of WLR with Tween 80, followed by the addition of the mixture into the culture media. With the increase of desulfurization time, the swelling value of desulfurizated waste latex rubber (DWLR) increased, but the crosslink density decreased. After co-culture desulfurization for 8–10 days, a DWLR with good desulfurization effect was obtained. The mechanical properties of natural rubber (NR)/DWLR composite improved significantly over those of NR/WLR composite. XPS and FTIR results revealed that Alicyclobacillus sp. could break the crosslinked sulfur bonds and oxidize them to sulfones groups. The increase of O element content on the surface of DWLR was confirmed by water contact angle measurements. The relationship between the crosslink density and sol fraction of DWLR with different desulfurization times agreed with the Horikx equation, an indication that the microorganisms could break the crosslinked sulfur bonds on the surface of WLR, but leaving the main chains intact.     

Trigonal‐Bipyramidal and Square‐Pyramidal Chromium?Manganese Chalcogenide Clusters, [E2CrMn2(CO)n]2− (E=S,Se, Te; n=9, 10): Synthesis,Electrochemistry, UV/Vis Absorption,and Computational Studies

The reactions of E powder (E=S, Se) with a mixture of Cr(CO)₆ and Mn₂(CO)₁₀ in concentrated solutions of KOH/MeOH produced two new mixed Cr? Mn? carbonyl clusters, [E₂CrMn₂(CO)₉]^2? (E=S, 1 ; Se, 2 ). Clusters 1 and 2 were isostructural with one another and each displayed a trigonal‐bipyramidal structure, with the CrMn₂ triangle axially capped by two μ₃‐E atoms. The analogous telluride cluster, [Te₂CrMn₂(CO)₉]^2? ( 3 ), was obtained from the ring‐closure of Te₂Mn₂ ring complex [Te₂Mn₂Cr₂(CO)₁₈]^2? ( 4 ). Upon bubbling with CO, clusters 2 and 3 were readily converted into square‐pyramidal clusters, [E₂CrMn₂(CO)₁₀]^2? (E=Se, 5 ; Te, 6 ), accompanied with the cleavage of one Cr? Mn bond. According to SQUID analysis, cluster 6 was paramagnetic, with S=1 at room temperature; however, the Se analogue ( 5 ) was spectroscopically proposed to be diamagnetic, as verified by TD‐DFT calculations. Cluster 6 could be further carbonylated, with cleavage of the Mn? Mn bond to produce a new arachno‐cluster, [Te₂CrMn₂(CO)₁₁]^2? ( 7 ). The formation and structural isomers, as well as electrochemistry and UV/Vis absorption, of these clusters were also elucidated by DFT calculations.     

Synthesis of racemic and enantiomerically pure 2′-thia-2′,3′-dideoxycytidine as potential anti-hepatitis B virus agents

A novel class of nucleosides with the C₁, atom bonded to three hetero atoms was synthesized. 2′-Thia-2′,3′-dideoxycytidine was the pilot compound of this series. (±)-β-2′-Thia-1′,3′-dideoxycytidine ( 6 ) and (±)-α-2′-thia-2′,3′-dideoxycytidine ( 7 ) were synthesized from (±)-3-mercapto-1,2-propanediol. The synthesis of the enantiomerically pure 2′-thia-2′,3′-dideoxycytidines (α-D-form, β-D-form, α-1-form and β-L-form) from optically pure (S)-(2,2-dimethyl-1,3-dioxalan-yl)methyl p-toluenesulfonate ( 8 ) and its (R)-isomer 18 was also described. The preliminary biological results showed that (+)-β-D-2′-thia-2′,3′-dideoxycytidine ( 26 ) was the most active against human hepatitis B virus with an ED₅₀ of 3 μM.     

Chemical Speciation of Amphoteric Ions on Semi‐Dry Scrubber Residue and Bag‐House Ash from MSWI

Two series of size‐fractionated combusted residues, a bag‐house ash and a scrubber residue, from a municipal solid waste incinerator (MSWI) were prepared and extracted by means of sequential chemical extraction (SCE) procedures proposed by Tessier. Concentrations of water‐soluble phase, exchangeable phase, carbonated phase, Fe/Mn oxide phase, organic matter phase, and residual phase bound amphoteric metals (Pb and Zn) were obtained, and have been compared with those of single batch extraction of toxic characteristic leaching procedure (TCLP). In each size fraction of baghouse ash or scrubber residue, lead or zinc shows a common phenomena that the TCLP value is always lower than the content of the water‐soluble fraction. For lead, baghouse ash has a significant size‐dependent distribution on the water‐soluble phase to perform a size‐dependent test of lead in the TCLP test. The zinc TCLP data having less size dependence might be due to that neither the baghouse ash nor the scrubber residue has a size‐dependent distribution on the water‐soluble zinc phase.     

Merging Photoredox and Nickel Catalysis: The Direct Synthesis of Ketones by the Decarboxylative Arylation of α‐Oxo Acids

The direct decarboxylative arylation of α‐oxo acids has been achieved by synergistic visible‐light‐mediated photoredox and nickel catalysis. This method offers rapid entry to aryl and alkyl ketone architectures from simple α‐oxo acid precursors via an acyl radical intermediate. Significant substrate scope is observed with respect to both the oxo acid and arene coupling partners. This mild decarboxylative arylation can also be utilized to efficiently access medicinal agents, as demonstrated by the rapid synthesis of fenofibrate.     

Detection of ClSO with time-resolved Fourier-transform infrared absorption spectroscopy

ClSO was produced as an intermediate upon irradiating a flowing mixture of Cl2SO and Ar with a KrF excimer laser at 248 nm. A step-scan Fourier-transform infrared spectrometer coupled with a small multipass absorption cell was employed to detect time-resolved absorption spectrum of ClSO. A transient spectrum in the region 1120-1200 cm(-1), which diminished on prolonged reaction, is assigned to the S-O stretching (nu1) mode of ClSO. A spectrum with a resolution of 0.3 cm(-1) partially reveals rotational structure with the Q-branch at 1162.9 cm(-1). Calculations with density-functional theory (B3LYP/aug-cc-pVTZ) predict the geometry, vibrational, and rotational parameters of ClSO. An IR absorption spectrum of ClSO simulated based on predicted rotational parameters agrees satisfactorily with experimental results. ClSO produced from photolysis of Cl2SO at 248 nm is internally hot.     

Voltammetric Detector for Liquid Chromatography: Determination of Triclosan in Rabbit Urine and Serum

A flow-electrolytic cell containing a strand of carbon fibers has been designed and characterized for use in a voltammetric detector for high-performance liquid chromatography. The detector was used for determination of triclosan (2,4,4-trichloro-2-hydroxydiphenyl ether) in rabbit serum and urine. Analysis of rabbit serum and urine 1 day and 1 to 5 days, respectively, after ingestion of oral triclosan revealed that the concentration of triclosan was higher than for control serum and urine. The concentration reached maximum levels after 6 h and 34 h or 44 h in serum and urine, respectively. When triclosan was determined in rabbit samples with the method proposed the results obtained were comparable with those obtained by high-performance liquid chromatography with ultraviolet detection.     

Determination and Differentiation of Two Seemingly Identical Medicinal Herbs by Capillary Electrophoresis with Electrochemical Detection

A high-performance capillary electrophoresis with electrochemical detection (CE-ED) method has been employed for the determination of six bioactive ingredients in traditional Chinese herbs, Herba cepbalanoplosis segeti and Herba cirsii japonici. The effects of several factors such as the acidity and concentration of running buffer, the separation voltage, the applied potential and the injection time on CE-ED were investigated. Under the optimum conditions, the six analytes could be well separated within 21 min in a 75 cm length capillary at the separation voltage of 15 kV in a 50 mmol L^–1 borax running buffer (pH 8.4). A 300 m diameter carbon disk electrode was used as the working electrode positioned carefully opposite the outlet of the capillary in a wall-jet configuration at potential of +950 mV (vs. SCE). Good linear relationship was established between peak current and concentration of analytes over two orders of magnitude with detection limits (S/N=3) ranged from 1.5×10^–7 to 6.0×10^–7 g mL^–1 for all six analytes. This proposed method has been successfully applied for the analysis of traditional Chinese herbs after a relatively simple extraction procedure, further on, for the differentiation of these above two seemingly identical herbs based on their electropherograms or characteristic electrochemical profiles.     

Postfunctionalization of BN‐Embedded Polycyclic Aromatic Compounds for Fine‐Tuning of Their Molecular Properties

New BN‐embedded, thiophene‐fused, polycyclic aromatic compounds with planar geometry were designed and synthesized. The molecules showed excellent stability and chemical robustness. Postfunctionalization on this skeleton was demonstrated with a series of electrophilic bromination, palladium‐catalyzed cross‐coupling, and Knoevenagel condensation reactions. The π skeleton remained intact during these late‐stage transformations. The optical and electronic properties have been well tuned through incorporation of electron‐rich and ‐deficient groups on the backbone. This work shows the great advantage of the postfunctionalization strategy on BN‐containing polycyclic aromatic compounds for fast diversification and materials screening.