The chemical-looping gasification (CLG) of coal is a clean and effective technology for syngas generation. Sharing principles with chemical-looping combustion (CLC), CLG also uses oxygen carriers to transfer lattice oxygen to the fuel. Investigations into CLG with different O/C ratios are carried out in a fluidized bed reactor with steam used as the gasification− fluidization medium. The effect of the active component content of the oxygen carrier on the gas selectivity is performed, and reaction mechanisms between the Fe 2 O 3 oxygen carrier and coal with steam as the gasification agent are discussed. Moreover, we also assessed the reactivity of the CaO-decorated iron-based oxygen carrier particles in multicycle reactions. The carbon conversion efficiency is increased from 55.74 to 81% with increasing O/C ratio, whereas the content of H 2 first decreases and then increases. The addition of CaO can increase the carbon conversion efficiency and the gasification rate substantially and reduce the generation rate of H 2 S from 1.89 × 10 −3 to 0.156 × 10 −3 min −1 . Furthermore, X-ray diffraction (XRD) images indicate that the CaO-decorated iron-based oxygen carrier particles were completely regenerated after six redox cycles. Finally, the peak fitting of gasification reaction rate curves is used to explore the reaction mechanism between coal char and the CaOdecorated iron-based oxygen carrier, indicating that the reactions in the CLG include three stages: the complex reactions involved an oxygen carrier, coal char, and steam; the gasification of coal char; and the reduction of Fe 3 O 4 to FeO. The two-segment modified random pore model (MRPM) fits the experiment data well.
Aggregation-caused quenching (ACQ)
and poor photostability in aqueous
media are two common problems for organic fluorescence dyes which
cause a dramatic loss of fluorescence imaging quality and photodynamic
therapy (PDT) failure. Herein, a local hydrophobic cage is built up
inside near-infrared (NIR) cyanine-anchored fluorescent silica nanoparticles
(FSNPs) in which a hydrophobic silane coupling agent (n-octyltriethoxysilane, OTES) is doped into FSNPs for the first time
to significantly inhibit the ACQ effect and inward diffusion of water
molecules. Therefore, the obtained optimal FSNP-C with OTES-modification
can provide hydrophobic repulsive forces to effectively inhibit the
π–π stacking interaction of cyanine dyes and simultaneously
reduce the formation of strong oxidizing species (•OH and H2O2) in reaction with H2O, resulting
in the best photostability (fluorescent intensity remained at 90.1%
of the initial value after 300 s of laser scanning) and a high PDT
efficiency on two- and three-dimensional (spheroids) HeLa cell culture
models. Moreover, through molecular engineering (including increasing
covalent anchoring sites and steric hindrance groups of cyanine dyes),
FSNP-C exhibits the highest fluorescent intensity both in water solution
(12.3-fold improvement compared to free dye) and living cells due
to the limitation of molecular motion. Thus, this study provides an
effectively strategy by combining a local hydrophobic cage and molecular
engineering for NIR FSNPs in long-term bright fluorescence imaging
and a stable PDT process.
Chemical looping combustion (CLC) is an attractive technology
for CO2 capture with high energy efficiency. In this article,
an Fe2O3/Al2O3 (Fe:Al
= 3:1) oxygen carrier was first prepared by the solution combustion
approach for the CLC process. The prepared oxygen carrier was characterized
by different means. XRD identification has substantiated the necessity
of calcinations to synthesize Fe2O3/Al2O3 oxygen carrier. SEM and TEM images showed the regular
spherical and cubical shape and abundant porous structure in Fe2O3/Al2O3 oxygen carrier,
respectively. Structural characteristics displayed that the pore shape
of Fe2O3/Al2O3 particles
was heterogeneous. The average pore size and surface area were 64.76
nm and 4.01 m2/g, respectively. Further, H2 temperature
programmed reduction (TPR) of Fe2O3/Al2O3 oxygen carrier indicated that the reduction reaction
had only one distinct DTG peak with the weight loss rate reaching
4.75 wt %/min. Finally, five cycles of red–ox reaction by alternating
with CH4 and air demonstrated that Fe2O3/Al2O3 oxygen carrier had excellent
reactivity and sintering resistance and consequently was capable of
the CLC process.
Agricultural soils have been increasingly subject to heavy metal pollution worldwide. However, the impacts on soil microbial community structure and activity of field soils have been not yet well characterized. Topsoil samples were collected from heavy metal polluted (PS) and their background (BGS) fields of rice paddies in four sites across South China in 2009. Changes with metal pollution relative to the BGS in the size and community structure of soil microorganisms were examined with multiple microbiological assays of biomass carbon (MBC) and nitrogen (MBN) measurement, plate counting of culturable colonies and phospholipids fatty acids (PLFAs) analysis along with denaturing gradient gel electrophoresis (DGGE) profile of 16S rRNA and 18S rRNA gene and real-time PCR assay. In addition, a 7-day lab incubation under constantly 25°C was conducted to further track the changes in metabolic activity. While the decrease under metal pollution in MBC and MBN, as well as in culturable population size, total PLFA contents and DGGE band numbers of bacteria were not significantly and consistently seen, a significant reduction was indeed observed under metal pollution in microbial quotient, in culturable fungal population size and in ratio of fungal to bacterial PLFAs consistently across the sites by an extent ranging from 6% to 74%. Moreover, a consistently significant increase in metabolic quotient was observed by up to 68% under pollution across the sites. These observations supported a shift of microbial community with decline in its abundance, decrease in fungal proportion and thus in C utilization efficiency under pollution in the soils. In addition, ratios of microbial quotient, of fungal to bacterial and qCO2 are proved better indicative of heavy metal impacts on microbial community structure and activity. The potential effects of these changes on C cycling and CO2 production in the polluted rice paddies deserve further field studies.
A field experiment was conducted with cultivation of hybrid and conventional cultivars in a rice paddy from China. Rhizosphere soil was sampled and CO 2 flux was measured at tillering (S1), grain filling (S2) and ripening (S3) across the growth stages. Microbial community structure, abundance and activity were analyzed using a combination of functional (enzymes) and denaturing gradient gel electrophoresis (DGGE) and real-time PCR molecular approaches. Invertase and urease activities, total microbial biomass carbon, bacterial 16S rRNA and fungal internal transcribed spacer rRNA gene copies were found to be the highest at S2 under both cultivars, being greater under the hybrid cultivar than under the conventional cultivar across the stages. Moreover, the CO 2 flux was 11%, 16% and 25% higher under the hybrid cultivar than under the conventional cultivar at S1, S2 and S3, respectively. Principal component analyses of the PCR-DGGE profile revealed a significant difference between conventional and hybrid cultivars across growth stages. Sequencing DGGE bands of the bacterial 16S rRNA gene showed that a particular bacterial group of Alphaproteobacteria was enhanced and several distinct operational taxonomic units markedly resembled Ascomycota under the hybrid cultivar. These illustrate a significant selection of a particular group of bacteria and fungi of the hybrid cultivar. However, the potential impacts of these cultivar effects in soil C and N cycling deserve further field studies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.