Viability and distribution of bacteria immobilized on Sawdust@silica: The removal mechanism of phenanthrene in soil.

Immobilized cells (ICs) have been widely used to enhance the remediation of organic-contaminated soil (e.g., polycyclic aromatic hydrocarbons, PAHs). Once ICs are added to the heterogeneous soil, degradation hotspots are immediately formed near the carrier, leaving the remaining soil lack of degrading bacteria. Therefore, it remains unclear how ICs efficiently utilize PAHs in soil. In this study, the viability of Silica-IC (Cells@Sawdust@Silica) and the distribution of inoculated ICs and phenanthrene (Phe) in a slurry system (soil to water ratio 1:2) were investigated to explore the removal mechanism of PAHs by the ICs. Results showed that the Silica-IC maintained (i) good reproductive ability (displayed by the growth curve in soil and water phase), (ii) excellent stability, which was identified by the ratio of colony forming units in the soil phase to the water phase, the difference between the colony number and the DNA copies, and characteristics of the biomaterial observed by the FESEM, and (iii) high metabolic activity (the removal percentages of Phe in soil by the ICs were more than 95% after 48 h). Finally, the possible pathways for the ICs to efficiently utilize Phe in soil are proposed based on the distribution and correlation of Phe and ICs between the soil and water phase. The adsorption-degradation process was dominant, i.e., the enhanced degradation occurred between the ICs and carrier-adsorbed Phe. This study provided new insights on developing a bio-material for efficient bio-remediation of PAHs-contaminated soil.

Synthesis of highly substituted benzene ring systems through three-component coupling of enyne imines, Fischer carbene complexes, and electron-deficient alkynes.

Three-component coupling of Fischer carbene complexes, enyne aldehyde hydrazones, and electron-deficient alkynes leads to simple benzoate derivatives in a process involving the formation of an N-aminopyrrole derivative, Diels-Alder reaction, and nitrene extrusion. The products are readily converted into isoquinolones through reaction with primary amines. The reaction proceeds best with highly substituted and electron-rich pyrroles even though these are the sterically least favorable substrates, and this reactivity trend is supported by a computational study.

Trade-off between sulfidated zero-valent iron reactivity and air stability: Regulation of iron sulfides by ammonium dihydrogen phosphate.

The reactivity and stability of zero-valent iron (ZVI) and sulfidated zero-valent iron (S-ZVI) are inherently contradictory. Iron sulfides (FeSX) on the S-ZVI surface play multiple roles, including electrostatic adsorption and catalyzing reduction. We proposed to balance the reactivity and air stability of S-ZVI by regulating FeSX. Benefiting from the superior coordination and accelerate electron transport capabilities of phosphate, herein, eco-friendly ammonium dihydrogen phosphate (ADP) was employed to synthesize N, P, and S-incorporated ZVI (NPS-ZVI) and regulate the FeSX. Raman, FTIR, XPS, and density functional theory (DFT) calculations were combined to reveal that HPO42- acts as the main P species on the Fe surface. The superior reactivity of NPS-ZVI was quantified by kobs, kSA, and kM of Cr(VI), which were 210.77, 27.44, and 211.17-fold than ZVI, respectively. NPS-ZVI demonstrated excellent reusability, with no risk of secondary pollution. Critically, NPS-ZVI could effectively maintain FeSX stability under the combination of diffusion limitation and surface protection mechanisms of ADP. The superior reactivity of NPS-ZVI was attributed to the fact that ADP maintains FeSX stability and accelerates electron transport. This study provides a novel strategy in balancing the reactivity and air stability of S-ZVI and offers theoretical support for material modification.

Remediation of Cr(VI)-contaminated soil by sulfidated zero-valent iron: The effect of citric acid as eluant and modifying agent.

Leaching and chemical reduction are two commonly used methods for Cr(VI)-contaminated soil remediation. Leaching focuses more on leaching Cr(VI) out of the soil. Chemical reduction has the disadvantages of poor fluidity of reductant. Combining these two remediation methods, this study investigated the performance of Cr(VI)-contaminated soil when H2O and citric acid were used as eluant separately and sulfidated zero-valent iron (SZVI) as reductant. And based on the properties of Cr(VI) chelated with -COOH to form a complex and the characteristics of -OH anchored to FeSx, citric acid modified SZVI (Cit-SZVI) was prepared. The prepared Cit-SZVI was characterized by SEM-EDS, XPS, XRD to study its surface properties. The transformation of Cr species in soil was explored by BCR sequential extraction. The results indicated Cr(VI) removal by SZVI was significantly promoted when citric acid as eluant compared with H2O. With SZVI dosage of 2.0 wt%, 23.1 mg/L Cr(VI) was basically removed within 60 min when citric acid as eluant, while only 60% Cr(VI) was removed when H2O as eluant even after 3 h. The kobs of Cit-SZVI was 1.4 times that of SZVI when H2O as eluant. The characterization of Cit-SZVI showed that more FeSx was formed on the surface of the Cit-SZVI, and more -OH of citric acid was anchored to FeSx, leaving -COOH available to chelate Cr(VI). Compared with H2O as eluant and SZVI/Cit-SZVI as reducing agent, the removal effect of Cr(VI) was the best when citric acid as eluant and SZVI as reducing agent. BCR sequential extraction showed that Cr(VI) was effectually fixed, weak acid extractable Cr proportion decreased significantly and residual Cr proportion increased in the treated soil. The combination of leaching and chemical reduction proposed in this study can greatly enhance the Cr(VI) removal effect in soil, which is important for the remediation of Cr(VI)-contaminated soil.

Mn(CeZr)Ox chelation-induced synthesis and its hydrothermal aging characteristics for catalytic abatement of toluene.

In this work, Mn(CeZr)Ox was synthesized by using chelation-induced synergistic self-assembly strategy for the combustion of toluene. The physicochemical properties of the synthesized catalysts were characterized by XRD, ICP-MS, SEM, TEM, XPS and N2 sorption. The Mn(CeZr)Ox catalyst with T90 = 225 °C exhibited improved catalytic performance than the original MnOx catalyst (T90 = 260 °C) and had significant low-temperature activity. The relationship between catalyst activity and structure was analyzed. By substituting Ce and Zr elements into the hollow microspheres of MnO2, oxygen vacancies were produced. The main factors affecting the catalytic activity of the catalyst and the reason why it remained high catalytic activity after a long period of hydrothermal treatment were discussed. After hydrothermal aging, the original pore structure of Mn(CeZr)Ox catalyst collapsed and the specific surface area decreased, but the overall crystallinity of the catalyst increased and the content of oxygen species in the lattice increased. The distribution of Mn and oxygen species on the catalyst surface changed significantly after hydrothermal treatment. The appropriate ratio of Mn4+ to Mn3+ and the ratio of lattice oxygen to adsorbed oxygen species are beneficial to the redox reaction cycle.

N-allyl-N-sulfonyl ynamides as synthetic precursors to amidines and vinylogous amidines. An unexpected N-to-C 1,3-sulfonyl shift in nitrile synthesis.

A detailed study of amidine synthesis from N-allyl-N-sulfonyl ynamides is described here. Mechanistically, this is a fascinating reaction consisting of diverging pathways that could lead to deallylation or allyl transfer depending upon the oxidation state of palladium catalysts, the nucleophilicity of amines, and the nature of the ligands. It essentially constitutes a Pd(0)-catalyzed aza-Claisen rearrangement of N-allyl ynamides, which can also be accomplished thermally. An observation of N-to-C 1,3-sulfonyl shift was made when examining these aza-Claisen rearrangements thermally. This represents a useful approach to nitrile synthesis. While attempts to render this 1,3-sulfonyl shift stereoselective failed, we uncovered another set of tandem sigmatropic rearrangements, leading to vinyl imidate formation. Collectively, this work showcases the rich array of chemistry one can discover using these ynamides.

Facile synthesis of Pt-Ce0.63Zr0·37O2-Y catalysts and the application in catalytic oxidation of toluene.

In this work, a series of Pt-Ce0.63Zr0·37O2-Y catalysts were prepared by unique simple mechanical mixing method. The catalytic activity of these catalysts for toluene oxidation was investigated. The physicochemical properties of the catalysts were characterized by XRD, ICP-MS, SEM, TEM, XPS and N2 sorption. Pore size distribution was analyzed according nitrogen adsorption and desorption isotherms. The catalytic results showed that using NaY as support for Pt-Ce0.63Zr0·37O2-Y could enhance the conversion of toluene during the oxidation process in comparison with HY. Further mixing cerium zirconium solid solution with Pt-NaY can improve the oxidation catalytic property of these catalysts. The conversion of toluene over Pt-Ce0.63Zr0·37O2-NaY reached more than 90% at 200 °C. High catalytic stability was obtained for toluene oxidation over Pt-Ce0.63Zr0·37O2-NaY. Platinum, cerium and zirconium can be uniformly dispersed on Y zeolite with small particle size by simple mechanical synthesis. The effect of drying methods on catalytic activity and hydrothermal stability of catalysts were also investigated in this research.

Preliminary research on flow rate and free surface of the accelerator driven subcritical system gravity-driven dense granular-flow target.

A spallation target is one of the three core parts of the accelerator driven subcritical system (ADS), which has already been investigated for decades. Recently, a gravity-driven Dense Granular-flow Target (DGT) is proposed, which consists of a cylindrical hopper and an internal coaxial cylindrical beam pipe. The research on the flow rate and free surface are important for the design of the target whether in Heavy Liquid Metal (HLM) targets or the DGT. In this paper, the relations of flow rate and the geometry of the DGT are investigated. Simulations based on the discrete element method (DEM) implementing on Graphics Processing Units (GPUs) and experiments are both performed. It is found that the existence of an internal pipe doesn't influence the flow rate when the distance from the bottom of the pipe to orifice is large enough even in a larger system. Meanwhile, snapshots of the free surface formed just below the beam pipe are given. It is observed that the free surface is stable over time. The entire research is meaningful for the design of DGT.

A ring-closing yne-carbonyl metathesis of ynamides.

[reaction: see text] An acid-catalyzed ring-closing ynamide-carbonyl metathesis is described here. This hetero RCM methodology is applicable to the construction of carbocycles as well as heterocycles such as chromenes, quinolizidines, indolizidines, and pyrrolizidines.

Brønsted acid-catalyzed highly stereoselective arene-ynamide cyclizations. A novel keteniminium Pictet-Spengler cyclization in total syntheses of (+/-)-desbromoarborescidines A and C.

[reaction: see text] A Brønsted acid-catalyzed highly stereoselective arene-ynamide cyclization is described. These reactions constitute a keteniminium variant of Pictet-Spengler cyclizations, leading to efficient synthesis of nitrogen heterocycles and related alkaloids. Total syntheses of desbromoarborescidines A and C are illustrated here as first applications of this methodology.

Copper-catalyzed stereospecific N-allenylations of amides. Syntheses of optically enriched chiral allenamides.

[reaction: see text] Syntheses of chiral allenamides via a stereospecific amidation of optically enriched allenyl iodides using catalytic copper(I) salt and N,N'-dimethylethylene-diamine are described here.

Synthesis of pyrroles through coupling of enyne-hydrazones with Fischer carbene complexes.

[reaction: see text] The coupling of enyne-imines with Fischer carbene complexes leads to the formation of alkenylpyrrole derivatives. Maximum yields of pyrrole adducts were obtained using N,N-dimethylhydrazones. A mechanism involving alkyne insertion followed by nucleophilic attack of the imine nitrogen at the intermediate alkenylcarbene complex was proposed.

Sonogashira cross-couplings of ynamides. Syntheses of urethane- and sulfonamide-terminated conjugated phenylacetylenic systems.

[reaction: see text] The first successful Sonogashira coupling of ynamides with aryl and vinyl iodides is described here. This study resolves the problem of the competing pathway involving homocoupling of ynamides and provides a practical entry to novel urethane- or sulfonamide-terminated conjugated acetylenic systems. An interesting tandem hydrohalogenation and Sonogashira coupling was also observed to give an en-ynamide.

Copper sulfate-pentahydrate-1,10-phenanthroline catalyzed amidations of alkynyl bromides. Synthesis of heteroaromatic amine substituted ynamides.

A practical cross-coupling of amides with alkynyl bromides using catalytic CuSO(4).5H(2)O and 1,10-phenanthroline is described here. This catalytic protocol is more environmentally friendly than the use of CuCN or copper halides and provides a general entry for syntheses of ynamides including various new sulfonyl and heteroaromatic amine substituted ynamides. Given the interest in ynamides, this N-alkynylation of amides should be significant for the future of ynamides in organic synthesis.

Synthesis of amidines using N-allyl ynamides. A palladium-catalyzed allyl transfer through an ynamido-pi-allyl complex.

A de novo transformation of N-allyl-N-sulfonyl ynamides to amidines is described featuring a palladium-catalyzed N-to-C allyl transfer via ynamido-palladium-pi-allyl complexes.

Copper(II)-catalyzed amidations of alkynyl bromides as a general synthesis of ynamides and Z-enamides. An intramolecular amidation for the synthesis of macrocyclic ynamides.

A general and efficient method for the coupling of a wide range of amides with alkynyl bromides is described here. This novel amidation reaction involves a catalytic protocol using copper(II) sulfate-pentahydrate and 1,10-phenanthroline to direct the sp-C-N bond formation, leading to a structurally diverse array of ynamides including macrocyclic ynamides via an intramolecular amidation. Given the surging interest in ynamide chemistry, this atom economical synthesis of ynamides should invoke further attention from the synthetic organic community.

Synthesis of furano[2,3-c]pyran-3-one and thieno[2,3-c]pyran-3-one derivatives through the coupling of 3-alkynyl-2-heteroaromatic carboxaldehydes with Fischer carbene complexes: total synthesis of a Baccharis-derived cadinene derivative.

The coupling of Fischer carbene complexes with 3-alkynyl-2-heteroaromatic carboxaldehyde derivatives has been examined. The reaction affords pyrones fused to furans or thiophenes in a single step. The compounds are stable enough for isolation. If the carbene complex features a remote alkene substituent, a subsequent Diels-Alder reaction can occur. This reaction has been used as the key step in the synthesis of a naturally occurring cadinene derivative.