Oxygen Vacancy Induced Strong Metal-Support Interactions on Ni/Ce0.8Zr0.2O2 Nanorod Catalysts for Promoting Steam Reforming of Toluene: Experimental and Computational Studies.

To develop an efficient Ni-based steam reforming catalyst for tar removal from the products of biomass gasification, Ni/Ce0.8Zr0.2O2 nanorods were designed. The Ni/Ce0.8Zr0.2O2 nanorod was used as a catalyst in steam reforming of toluene, which was regarded as a model compound of biomass gasification tar. At gas hourly space velocity (GHSV) of 24,000 h-1 and Ni loading of 5 wt %, the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst achieved 100% of toluene conversion at 600 °C. After 10 h of operation, toluene conversion still reached 87.6%, and the carbon deposition rate was only 1.9 mg/gcat h-1. The experimental results demonstrated that the 5Ni/Ce0.8Zr0.2O2 nanorod catalyst showed much higher catalytic activity and coking resistance than other Ni-based catalysts reported in the literature. Through different characterization technologies and density functional theory calculations, it was confirmed that the excellent catalytic performance was attributed to the strong metal-support interaction (SMSI) between Ni and the {100} facet of Ce0.8Zr0.2O2. The special surface structure of {100} allowed Ni atoms to anchor to the surface oxygen vacancies and maintained its reduced state by electron transport between surface atoms. The anchored Ni facilitated oxygen vacancies formation and H2O dissociation on the support, while the support modulated the electronic structure of Ni, which promoted its ability to toluene activation.

Microbiologically induced calcite precipitation for in situ stabilization of heavy metals contributes to land application of sewage sludge.

Microbiologically induced calcite precipitation (MICP) has shed new light on solving the problem of in situ stabilization of heavy metals (HMs) in sewage sludge before land disposal. In this study, we examined whether MICP treatment can be integrated into a sewage sludge anaerobic digestion-land application process. Our results showed that MICP treatment not only prevented the transfer of ionic-state Cd from the sludge to the supernatant (98.46 % immobilization efficiency) but also reduced the soluble exchangeable Pb and Cd fractions by up to 100 % and 48.54 % and increased the residual fractions by 22.54 % and 81.77 %, respectively. In addition, the analysis of the stability of HMs in MICP-treated sludge revealed maximum reductions of 100 % and 89.56 % for TCLP-extractable Pb and Cd, respectively. Three-dimensional fluorescence, scanning electron microscopy-energy-dispersive X-ray spectroscopy, X-ray diffraction, and Fourier-transform infrared spectroscopy analyses confirmed the excellent performance of the ureolytic bacteria Sporosarcina ureilytica ML-2 in the sludge system. High-throughput sequencing showed that the relative abundance of Sporosarcina sp. reached 53.18 % in MICP-treated sludge, and the urease metabolism functional genes unit increased by a maximum of 239.3 %. The MICP technology may be a feasible method for permanently stabilizing HMs in sewage sludge before land disposal.

Mechanism of microbiologically induced calcite precipitation for cadmium mineralization.

Microbiologically induced calcite precipitation (MICP) technology shows potential for remediating heavy metal pollution; however, the underlying mechanism of heavy metal mineralization is not well-understood, limiting the application of this technology. In this study, we targeted Cd contamination (using 15:1, 25:1, and 50:1 Ca2+/Cd2+ molar ratios) and showed that the ureolytic bacteria Sporosarcina ureilytica ML-2 removed >99.7 % Cd2+ with a maximum fixation capacity of 75.61 mg-Cd/g-CaCO3 and maximum precipitation production capacity of 135.99 mg-CaCO3/mg-cells. Quantitative PCR analysis showed that Cd2+ inhibited the expression of urease genes (ureC, ureE, ureF, and ureG) by 70 % in the ML-2 strain. Additionally, the pseudo-first-order kinetics model (R2 = 0.9886), intraparticle diffusion model (R2 = 0.9972), and Temkin isotherm model (R2 = 0.9828) described the immobilization process of Cd2+ by bio calcite in MICP-Cd system. The three Cd2+ mineralization products generated by MICP were attributed to surface precipitation (Cd2+ → Cd(OH)2), direct binding with the CO32-/substitution calcium site of calcite (Cd2+ → CdCO3, otavite), and calcite lattice vacancy anchors (Cd2+ → (CaxCd1-x)CO3). Our findings improve the understanding of the mechanisms by which MICP can achieve in situ stabilization of heavy metals.

Microbiologically induced calcite precipitation technology for mineralizing lead and cadmium in landfill leachate.

As a new bioremediation technology for toxic metals, microbiologically induced calcite precipitation (MICP) is gradually becoming a research focus. This study investigated the application of MICP to mineralize toxic metals (lead and cadmium) in landfill leachate for the first time. In the experiment of remediating synthetic landfill leachate (SLL) contaminated by Pb2+, 100% of the 20 mg/L Pb2+ was removed when the maximum urease activity was only 20.96 U/ml. Scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) and laser particle size characterizations of the precipitates indicate the formation of agglomerated square particles, 76.9% of which had sizes that ranged from 33.93 to 57.06 µm. Fourier transform infrared spectroscopic and X-ray diffraction analyses confirmed that the precipitates consisted predominantly of calcite crystals, and the unit cell lattice constants of the precipitates (a = b = 4.984 Å, c = 17.171 Å) matched those of calcite, while lead was fixed as hydrocerussite. In addition, the Pb-MICP precipitates were stable under continuous acid degradation (pH = 5.5), and only 1.76% of the lead was released after 15 days. In the verification test of toxic metals remediation in a real landfill leachate (RLL), all of the Pb2+ and Cd2+ (initial concentrations: Pb2+ = 25 mg/L; Cd2+ = 5.6205 mg/L) was mineralized simultaneously, which further confirmed the feasibility of MICP for toxic metal remediation in landfill leachate. However, optimizing the urea dosage and combining the ammonium recovery are necessary strategies required for improving the economic and environmental benefits of the MICP process.

Study on the feasibility of using monolithic catalyst in the in-situ catalytic biomass pyrolysis for syngas production.

In-situ catalytic biomass pyrolysis for syngas production is a competitive technology for the recovery of energy in biomass. However, in conventional in-situ catalytic pyrolysis process, the mode of catalyst introduction makes it difficult to separate the catalyst from the char after pyrolysis, resulting in difficulty in catalyst recycling. We considered that the use of monolithic catalyst which has larger size than the biomass feedstock might solve the problem of the separation difficulty between the catalyst and char. In order to verify the feasibility of this strategy, NiO/γ-Al2O3 was respectively supported on ceramic honeycomb, metal foam, and metal wire mesh to produce three monolithic catalysts with different outer surface areas. Their catalytic performance for cattle manure pyrolysis was tested and the result revealed that compared with the granular NiO/γ-Al2O3, using monolithic catalysts with ceramic honeycomb, metal foam, and metal wire mesh carrier respectively increased the gas production by 37%, 33%, and 11%. The use of monolithic catalyst in in-situ catalytic biomass pyrolysis, not only simplified the separation process of catalyst and char, but also enhanced the catalysis performance.

Interfacial Titanium Diffusion Self-Adapting Layer in Ultrathin Epitaxial MnO2/TiO2 Heterostructures.

The electrochemical performance of supercapacitors is suppressed by a large number of defects in the interface of heterostructure due to lattice mismatch. In this paper, the (001) oriented rutile MnO2 thin films with different thicknesses were grown on rutile TiO2 substrates. The lattice mismatch between film and substrate was minimized through a Ti diffusion self-adapting layer. The energy-dispersive spectroscopy mappings were used to measure the diffusion range of Ti. The results of high-resolution X-ray diffraction confirmed that the dependence of the out-of-plane lattice parameter on the thickness was consistent with the self-adapting interface model, indicating that Ti diffusion can indeed alleviate the lattice mismatch. In addition, the results of the synchrotron soft X-ray absorption spectrum indicated that the capacitance of the thin films with a large proportion of Ti diffusion increased with electrons involved in the reaction. Although the decrease of carrier density and conductivity of the thinner films depressed the electrochemical activity, it is worth mentioning that the film we designed still has considerable specific capacitance even when it is very thin, which can provide a new idea for the development of thinner and larger capacity potential micro-supercapacitors.

A strategy of using recycled char as a co-catalyst in cyclic in-situ catalytic cattle manure pyrolysis for increasing gas production.

Cattle manure is a major livestock waste in agroecosystem, and in-situ catalytic pyrolysis is considered as a potential technology for its disposal. In order to increase the gas production during cattle manure pyrolysis and alleviate the problem of frequent regeneration-separation of the in-situ catalyst, a strategy of in-situ catalytic pyrolysis was proposed in this work, in which the pyrolytic char product was not separated from the pyrolysis catalyst of NiO/γ-Al2O3 but mixed with it and recycled for several times as the co-catalyst for cattle manure pyrolysis instead. Adopting this strategy, it was observed that the mixed-type catalyst could lead to 70% increase in gas production and 82% promotion in syngas energy conversion rate compared with the circumstance of no catalyst added. Through different means of characterization, it was found that there are synergistic effects between char and NiO/γ-Al2O3, which enhance the catalytic performance of catalyst. On one hand, during the pyrolysis process, char can translate NiO into Ni that has higher cracking activity through in-situ reduction. On the other hand, due to its rich porous texture and large pore volume, char can act as an additional adsorbent for the reactants. Based on the experimental results of this work, the proposed strategy of cyclic in-situ catalysis with the recycled char as the co-catalyst can be a promising scheme in the practical biomass pyrolysis process for gas production.

Visualization analysis of graphene and its composites for heavy metal wastewater applications.

In order to explore the research trends and hotspots related to the treatment of heavy metals in wastewater by graphene and its composites, this study collected information on 511 publications from the Science Citation Index-Expanded (SCIE) and conducted a quantitative and visual analysis. The article on the adsorption of heavy metals in wastewater by graphene and its composites first appeared in 2006 and continued to grow since 2011. It broke through 100 articles for the first time in 2016 and the overall trend is on the rise. The 511 articles were published in 185 journals, of which RSC Advances is the most dynamic journal, and Journal of Materials Chemistry A is the most authoritative journal. Asian authors published about 87.14% of papers, and China, Iran, and India played a leading role compared with other countries. The University of Chinese Academy of Sciences is the largest research institution for the adsorption of heavy metals in wastewater by graphene and its composites. Hot keywords are "heavy metal removal," "water sample," "recent advance," "reusable adsorbent," "graphene-based material," and "composite nanosheet." Combined with keywords and cluster analysis, the chemical modification of graphene oxide has become a hot research direction for graphene materials to remove heavy metals from wastewater. Among them, MnFe2O4-graphene composite is a hot spot for graphene modification. In general, HNO3, HCl, and EDTA are desorption reagents for graphene and its composites.

Enhancing oxygen evolution efficiency of multiferroic oxides by spintronic and ferroelectric polarization regulation.

Regulating the electronic structure of catalysts is the most efficient strategy yet, despite its limitations, to improve their oxygen evolution efficiency. Instead of only adjusting the electronic structure, here we utilize ferroelectric polarization to accelerate the oxygen evolution reaction as well. This is demonstrated on a multiferroic layered perovskite Bi5CoTi3O15 with in-situ grown BiCoO3. Thanks to the superimposed effects of electronic regulation and ferroelectric polarization, the as-prepared multiferroic electrocatalysts are more efficient than the benchmark IrO2 (with a final 320 mV overpotential at the current density of 10 mA cm-2 and a 34 mV dec-1 Tafel slope). This work not only demonstrates a low-cost and high-efficient OER electrocatalyst, but also provides a strategic design for multi-component electrocatalytic material systems by consideration of both spin and polarization degrees of freedom.

miR-548k regulates CXCL13 expression in myasthenia gravis patients with thymic hyperplasia and in Jurkat cells.

Myasthenia gravis (MG) is a B cell-mediated and T cell-dependent autoimmune disease. Thymic hyperplasia has great significance for MG pathogenesis and treatment. MicroRNAs (miRNAs) are a newly recognized type of gene expression regulatory factor that regulate gene expression at the post-transcriptional level. Additionally, miRNAs are involved in immune regulation of the thymus and the occurrence and development of autoimmune diseases. In this study, we found 33 miRNAs that were significantly dysregulated in thymic tissues from MG patients with thymus hyperplasia (MGH) compared with thymic tissues from normal controls using a miRNA microarray chip. We found a negative correlation between the miR-548k and CXCL13 mRNA levels in a large set of samples using quantitative real-time polymerase chain reaction (qRT-PCR). We found that the CXCL13 3'-untranslated region (UTR) was a target of miR-548k using bioinformatics analysis. Next, we obtained direct evidence that CXCL13 is a target of miR-548k using a luciferase reporter assay. Finally, we demonstrated negative regulation between mir-548k and CXCL13 in Jurkat cells. Thus, miR-548k regulates the mRNA expression of its target gene CXCL13 in the thymus of MGH patients and plays an important role in MGH pathogenesis.

Simple fabrication of Chitosan/Graphene nanoplates composite spheres for efficient adsorption of acid dyes from aqueous solution.

A facile method for the fabrication of crosslinked chitosan/graphene nanoplates composite sphere (CS/GNPs) was presented. The obtained samples were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopic (XPS) and thermogravimetric analysis (TGA). The adsorption activities of CS/GNPs for methyl orange (MO) and acid red 1 (AR1) were evaluated such as the effect of pH and GNPs content, as well as adsorption kinetics and isotherms. In view of practical, the reusability of CS/GNPs was also tested. The resulting adsorption capacity for MO is 230.91mgg-1 and 132.94mgg-1 for AR1, respectively. After saturated adsorption, CS/GNPs can be efficiently regenerated and reused with little uptake loss. Therefore, CS/GNPs is the apromising adsorbent with non-toxic, efficient, low-cost and easy to prepare for the dye removal.

Nanoscale Structural Modulation and Low-temperature Magnetic Response in Mixed-layer Aurivillius-type Oxides.

Nanoscale structural modulation with different layer numbers in layer-structured complex oxides of the binary Bi4Ti3O12-BiFeO3 system can give rise to intriguing phenomena and extraordinary properties, originating from the correlated interfaces of two different phases with different strain states. In this work, we studied the nanoscale structural modulation induced by Co-substitution in the Aurivillius-type oxide of Bi11Fe3Ti6O33 with a unique and naturally occurred mixed-layer structure. Nanoscale structural evolution via doping occurred from the phase-modulated structure composed of 4- and 5-layer phases to a homogeneous 4-layer structure was clearly observed utilizing x-ray diffraction and electron micro-techniques. Significantly, magnetic response for the samples under various temperatures was recorded and larger magnetic coercive fields (e.g. H c ∼ 10 kOe at 50 K) were found in the phase-modulated samples. Analyses of the x-ray absorption spectra and magnetic response confirmed that the low-temperature magnetic behaviour should be intrinsic to the phase-modulated structure inside the structural transformation region, mainly arising from structural distortions at the correlated interfaces.

Oxidative degradation stability and hydrogen sulfide removal performance of dual-ligand iron chelate of Fe-EDTA/CA.

Catalytic oxidation desulfurization using chelated iron catalyst is an effective method to remove H2S from various gas streams including biogas. However, the ligand of ethylenediaminetetraacetic acid (EDTA), which is usually adopted to prepare chelated iron catalyst, is liable to be oxidative degraded, and leads to the loss of desulfurization performance. In order to improve the degradation stability of the iron chelate, a series of iron chelates composed of two ligands including citric acid (CA) and EDTA were prepared and the oxidative degradation stability as well as desulfurization performance of these chelated iron catalysts were studied. Results show that the iron chelate of Fe-CA is more stable than Fe-EDTA, while for the desulfurization performance, the situation is converse. For the dual-ligand iron chelates of Fe-EDTA/CA, with the increase of mol ratio of CA to EDTA in the iron chelate solution, the oxidative degradation stability increased while the desulfurization performance decreased. The results of this work showed that Fe-EDTA/CA with a mol ratio of CA:EDTA = 1:1 presents a relative high oxidative degradation stability and an acceptable desulfurization performance with over 90% of H2S removal efficiency.

Superlattice-like structure and enhanced ferroelectric properties of intergrowth Aurivillius oxides.

Aurivillius oxides with an intergrowth structures have been receiving increasing interest because of their special structures and potential outstanding ferroelectric properties. In this work, Bi3LaTiNbFeO12-Bi5Ti3FeO15 and Bi3TiNbO9-Bi3LaTiNbFeO12 compounds were successfully synthetised using a simple solid-state reaction method. X-Ray diffraction patterns and scanning transmission electron microscopy high angle annular dark field (STEM-HAADF) images confirm the 2-3 and the 3-4 intergrowth structures in Bi3TiNbO9-Bi3LaTiNbFeO12 and Bi3LaTiNbFeO12-Bi5Ti3FeO15 compounds, respectively. A superlattice-like distortion in these oxides was proposed resulting from the combination of sub-lattices with different a and b parameters, which was validated by XRD refinements and Raman spectra. Polarization-electric field tests and pulsed polarization positive-up negative-down measurements demonstrate that such superlattice-like structures can effectively enhance the intrinsic ferroelectric polarization and coercive field of these oxides, especially when compared with their component oxides Bi3TiNbO9, Bi3LaTiNbFeO12 and Bi5Ti3FeO15. Simultaneously, ferroelectric Curie temperatures of Bi3TiNbO9-Bi3LaTiNbFeO12 and Bi3LaTiNbFeO12-Bi5Ti3FeO15 oxides are lowered because of the internal stress in the superlattice-like structure. Nevertheless, the paramagnetism of the samples is hardly influenced by their structure, while mainly related to their iron content, in which iron has a similar effective magnetic moment around 3.4-3.9.

Altered expression of miR-125a-5p in thymoma-associated myasthenia gravis and its down-regulation of foxp3 expression in Jurkat cells.

Myasthenia gravis is an autoantibody-mediated and T cell-dependent autoimmune disease of neuromuscular junctions. Thymomas may play a crucial role in the pathogenesis of thymoma-associated myasthenia gravis (TAMG), but the thymic pathogenesis of TAMG is unknown. MicroRNAs (miRNAs) are non-coding RNA molecules 21-24 nt in length that regulate the expression of their target genes in a post-transcriptional manner. In this study, we used a miRNA microarray chip to identify, for the first time, 137 miRNAs in normal tissue adjacent to the thymoma from TAMG patients that were significantly dysregulated compared with normal thymus controls. We confirmed the differential expression of miR-125a-5p in larger samples using quantitative real-time polymerase chain reaction (qRT-PCR). Using bioinformatics analysis, we identified the foxp3 3' untranslated region (UTR) as a target of miR-125a-5p. Importantly, miR-125a-5p expression exhibited a negative correlation with foxp3 expression in normal tissue adjacent to the thymoma from TAMG patients. Furthermore, we demonstrated that the expression of the foxp3 gene was modulated by miR-125a-5p in Jurkat cells. Taken together, our results suggest that the abnormal expression of miR-125a-5p and its effect on foxp3 expression are likely involved in the pathogenesis of TAMG.

Detecting and classifying linear structures in mammograms using random forests.

Detecting and classifying curvilinear structure is important in many image interpretation tasks. We focus on the challenging problem of detecting such structure in mammograms and deciding whether it is normal or abnormal. We adopt a discriminative learning approach based on a Dual-Tree Complex Wavelet representation and random forest classification. We present results of a quantitative comparison of our approach with three leading methods from the literature and with learning-based variants of those methods. We show that our new approach gives significantly better results than any of the other methods, achieving an area under the ROC curve A(z) = 0.923 for curvilinear structure detection, and A(z) = 0.761 for distinguishing between normal and abnormal structure (spicules). A detailed analysis suggests that some of the improvement is due to discriminative learning, and some due to the DT-CWT representation, which provides local phase information and good angular resolution.

Impact of using high-density polyethylene geomembrane layer as landfill intermediate cover on landfill gas extraction.

Clay is widely used as a traditional cover material for landfills. As clay becomes increasingly costly and scarce, and it also reduces the storage capacity of landfills, alternative materials with low hydraulic conductivity are employed. In developing countries such as China, landfill gas (LFG) is usually extracted for utilization during filling stage, therefore, the intermediate covering system is an important part in a landfill. In this study, a field test of LFG extraction was implemented under the condition of using high-density polyethylene (HDPE) geomembrane layer as the only intermediate cover on the landfill. Results showed that after welding the HDPE geomembranes together to form a whole airtight layer upon a larger area of landfill, the gas flow in the general pipe increased 25% comparing with the design that the HDPE geomembranes were not welded together, which means that the gas extraction ability improved. However as the heat isolation capacity of the HDPE geomembrane layer is low, the gas generation ability of a shallow landfill is likely to be weakened in cold weather. Although using HDPE geomembrane layer as intermediate cover is acceptable in practice, the management and maintenance of it needs to be investigated in order to guarantee its effective operation for a long term.

Overview on LFG projects in China.

Since the first landfill gas (LFG) power plant in China was built in 1998, by now more than 10years have passed. In this period the LFG utilization process has progressed greatly in China. An overall review of the process is presented in this paper, which includes the background of policies, the information about the approval procedure of LFG projects, and the theoretical methods used to estimate the amount of LFG's generation. Detailed analysis on the project practice, such as LFG collection techniques, LFG utilization condition in China, is made. According to statistic data, before the end of 2008, 26 LFG power projects have been built and put into operation with total power capacity around 56.8MW, and 2.234 million tons of carbon dioxide equivalent abatement has been achieved annually by all of these LFG projects. The future of LFG industry in China is expected that there is still considerable developing space for LFG utilization in the near coming years, however after 2012, the progress speed may slow down because of some adverse aspects, such as available landfill resource becomes scarce, new laws implemented in China might exclude Chinese landfills from future CDM activities, etc.

[Effect of ethanol on sulfate reduction and methanogenesis].

Base on the different niche characteristics of sulfate-reducing bacteria (SRB), acidogenic bacteria (AB) and methane-producing bacteria (MPB), this experiment used two-stage anaerobic treatment and circular gas stripping. Sucrose and ethanol were used as organic substrate (COD = 6 000 mg x L(-1). The effect of ethanol concentration on sulfate reduction, COD removal and methanogenesis, the effect of sulfide stripping and the best recycle ratio were investigated respectively at different COD/SO4(2-) ratios. The results indicate that the addition of ethanol promotes SO4(2-) reduction, reduces inhibition of competition resulted from COD/SO4(2-) decreasing, and makes SRB, AB and MPB in good synergetic metabolism. The efficiency of the system was improved obviously after ethanol/SO4(2-) ratio enhanced from 0 to 2. When the ratios of COD/SO4(2-) were 12, 6 and 4, SO4(2-) reduction efficiencies increased from 7.7%, 8.1%, 14.1% to 84.7%, 87.6%, 82.5%, COD removal efficiencies increased from 83.3%, 76.5%, 69.6% to 92.8%, 93.5%, 89.7%, and CH4/COD increased from 225.7, 204.6, 178.6 mL x g(-1) to 278.5, 253.7, 236.1 mL x g(-1), respectively. Dilution at a recycle ratio of 10 and stripping 30%-55% sulfide controlled sulfide concentrations less than 27.8, 38.4, 52.4 mg x L(-1), which inhibited effectively the toxicity of H2S. But higher recycle ratio (r = 20) made substrate gradient too little and SO4(2-) reduction efficiency reduced, while lower recycle ratio (r = 5) made sludge bed shrunken and COD removal efficiency reduced.