Pollution characteristics and microbial community succession of a rural informal landfill in an arid climate.

Informal landfills pose potential threats to the environment and human health due to the lack of anti-seepage measures. However, little research has been conducted on the distribution of pollutants in informal landfill sites situated in arid climates, as well as the underlying interaction mechanisms between environmental factors and microbial structure. In this study, we sought to investigate the pollution characteristics and microbial community succession of the landfill in northern China. The results revealed that heavy metals in the landfill showed poor mobility and migration. The lower layers of the garbage samples had higher water-soluble contents of heavy metals compared to the upper layers. The landfill-derived dissolved organic matter (DOM) was found to originate from microbial production, and four fluorescent components were identified, including fulvic acid-like substances, humus-like substances, and protein-like components. Fluorescence intensity and humification degree increased with increasing depth. The microbial diversity and richness decreased with sampling depth. The most abundant phyla in the samples were Proteobacteria, unidentified_Bacteria, Bacteroidota, Firmicutes, Myxococcota, Gemmatimonadota, Actinobacteria, and Deinococcota. As the sampling depth increased, Proteobacteria decreased, while Bacteroidota and Firmicutes showed a remarkable increase, with little variation observed in the other phyla. The partial least-squares path model (PLS-PM) results indicated that pH had the most significant effect on microbial abundance and diversity (direct effect value = -5.560), while DOM and heavy metals had the opposite effect, with direct effects of 1.838 and 3.231, respectively. DOM was identified as the driving factor for the variation in other environmental factors. The redundancy analysis (RDA) showed that the dominant genera were greatly influenced by Cu, humic-like substances, and protein-like substances. Among them, Bacillus, Alcanivorax, Devosia, and Chryseolinea may play important roles in the remediation of landfills. Our study not only gains a deeper understanding of the pollution risk of informal landfills in arid climates, but also provides a scientific basis for the future treatment and restoration of contaminated sites associated with landfills.

Incorporation of Ce3+ ions into dodecatungstophosphoric acid for the production of biodiesel from waste cooking oil.

A series of cerium-exchanged dodecatungstophosphates CexH3-3xPW12O40 (CexH3-3xPW, x = 0.4, 0.6, 0.7, 0.8, 0.9, and 1.0) were designed and characterized by Fourier transform infrared spectroscopy (FT-IR), pyridine adsorption IR spectra, X-ray diffraction (XRD), and temperature programmed desorption of ammonia (NH3-TPD). The activity of these catalysts was evaluated for the generation of biodiesel from waste cooking oil (WCO) with 27 wt% of free fatty acids (FFAs) and 1 wt% of water. Compared to theri parent H3PW12O40, CexH3-3xPW showed higher activity for esterification of FFAs and transesterification of triglyceride to mono-alkyl esters of fatty acids (FAMEs) in one-pot. The acidic properties of CexH3-3xPW depended on the amount of Ce3+ ions in the secondary structure of Keggin heteropolyacids, while conversion of triglycerides and FFAs depended on their increasing acid contents. Among CexH3-3xPW, Ce0.7H0.9PW showed significant activity due to its high Brønsted acidity and Lewis acidity with 98% conversion of WCO and almost 100% selectivity to FAME at the molar ratio of methanol to WCO = 21:1 and 65 °C for 12 h. The reaction adhered to first-order kinetics with the activation energy (Ea) of 71 kJ/mol and the frequency factor (A) of 1.8 × 108 min-1, while the reaction rates were not influenced by the internal mass transport. The catalyst behaved as a heterogeneous catalyst, which can achieve the regeneration and be used more than five runs but without obvious decrease in activity. The characteristics of the WCO methyl ester were found to be close to the engine requirement.

Ultra-deep desulfurization via reactive adsorption on peroxophosphomolybdate/agarose hybrids.

A catalyst system composed of peroxophosphomolybdates as catalytic center and agarose as matrix material had been designed. The [C16H33N(CH3)3]3[PO4{MoO(O2)2}4]/agarose (C16PMo(O2)2/agarose) hybrid was found to be active for oxidation desulfurization (ODS) of dibenzothiophene (DBT) or real fuel into corresponding sulfone by H2O2 as an oxidant, while the sulfur content could be reduced to 5ppm. The higher activity comes from its components including [PO4{MoO(O2)2}4] catalytic sites, the hydrophobic quaternary ammonium cation affinity to low polarity substrates, and agarose matrix affinity to H2O2 and sulfone. During the oxidative reaction, the mass transfer resistance between H2O2 and organic sulfurs could be decreased and the reaction rate could increase by the assistance of agarose and hydrophobic tails of [C16H33N(CH3)3]3[PO4{MoO(O2)2}4]. Meanwhile, the oxidative products could be adsorbed by agarose matrix to give clean fuel avoiding the post-treatment. In addition, the hybrid was easily regenerated to be reused.

Investigations on ferroelectric liquid crystal by high resolution TEM and solid state 13C NMR.

In order to investigate the structural and dynamical properties of ferroelectric liquid crystal (FLC) in different phases a model compound [4-(3)-(S)-methyl-2-(S)-chloropentanoyloxy)]-4'-nonyloxy-biphenyl (3M2CPNOB) is synthesized. High resolution transmission electron microscopy (HR-TEM) is applied to observe the morphology of 3M2CPNOB and temperature-dependent solid state (13)C NMR to record (13)C chemical shifts at different phases. A liquid nitrogen quenching method is used to maintain the conformation of the mesophases for HR-TEM experiments. TEM images show that all the smectic A (SmA), smectic C* (SmC*) and crystalline phases have lamellar morphology. The interplanar distances in the crystalline phase are smaller than those in SmA and SmC* phases because of denser arrangement of the molecules. Both (13)C chemical shifts and line shape vary with different phases. The experimental results suggest that SmC* phase as an intermediate occurs in the anisotropy transition process from SmA to crystalline phase, the helical structure of the SmC* phase unwinds in the magnetic field and the conformations of the SmA and isotropic phase are very similar.

Ag nanoparticles/PPV composite nanofibers with high and sensitive opto-electronic response.

The novel Ag nanoparticles/poly(p-phenylene vinylene) [PPV] composite nanofibers were prepared by electrospinning. The transmission electron microscope image shows that the average diameter of composite fibers is about 500 nm and Ag nanoparticles are uniformly dispersed in the PPV matrix with an average diameter of about 25 nm. The Fourier transform infrared spectra suggest that there could be a coordination effect to a certain extent between the Ag atom and the π system of PPV, which is significantly favorable for the dissociation of photoexcitons and the charge transfer at the interface between the Ag nanoparticle and the PPV. The Au top electrode device of the single Ag/PPV composite nanofiber exhibits high and sensitive opto-electronic responses. Under light illumination of 5.76 mW/cm2 and voltage of 20 V, the photocurrent is over three times larger than the dark current under same voltage, which indicates that this kind of composite fiber is an excellent opto-electronic nanomaterial.

Photoresponse of a single poly(p-phenylene vinylene)-CdSe bulk-heterojunction submicron fiber.

Bulk-heterojunction PPV (poly(p-phenylene vinylene))-CdSe submicron fibers have been prepared by introducing electrostatic interaction between thioglycolic acid capped CdSe nanocrystals and PPV precursor, subsequently with electrospinning and thermal conversion. The photoconductive device on a single PPV-CdSe fiber showed notable photoresponse, good response speed, wavelength-sensitivity, and reproducibility.

Vilsmeier reaction of enaminones: efficient synthesis of halogenated pyridin-2(1H)-ones.

A facile and efficient one-pot synthesis of halogenated pyridin-2(1H)-ones from a series of readily available enaminones under Vilsmeier conditions is described, and a mechanism involving sequential halogenation, formylation, and intramolecular nucleophilic cyclization is proposed.