Search

Soil aggregates play a key role in preserving soil organic carbon (SOC). However, the mechanisms controlling aggregate formation and SOC distribution in different sizes of aggregates remain unclear. Here, we studied the dynamics of aggregate formation and associated SOC transferring among different aggregate fractions using an isotopic tracer technique ( 14 C-labeled wheat residues). The year-long incubation results demonstrate that the wheat residue carbon applied to soil (Typic Hapludoll) was initially mainly stored in the pores between microaggregates that were agglomerated to form macroaggregates (>250 μm). The wheat carbon started to transfer to the inside of microaggregates (250–53 μm) after six months of the incubation. The newly formed humic acid carbon (HA 14 C) and fulvic acid carbon (FA 14 C) in the macroaggregates were 57–90% and 60–84% more than in microaggregates (250–53 μm), respectively. Later, the sequestrated SOC was decomposed or chemically transformed, resulting in a decrease in the ratio of HA 14 C/FA 14 C in macroaggregates and an increase in the silt/clay fraction (<53 μm). This result indicated that the SOC in the macroaggregates was vulnerable to degradation due to less protection by soil macrostructure, while it experienced a slow degradation due to strong surface adsorption or pore protection in soil microstructure. This study suggests that macroaggregates considerably control SOC turnover and thereby their stability considerably influences how much newly introduced organic carbon could be sequestrated into stable carbon pools like microaggregates. The turnover dynamics of macroaggregates provided insights into the potential of humic carbon formation that facilitates long-term carbon preservation in soil. [ABSTRACT FROM AUTHOR]

Abstract: Silicon-containing sulfonated polystyrene/acrylate-poly(vinyl alcohol) (Si-sPS/A-PVA) and Si-sPS/A-PVA-phosphotungstic acid (Si-sPS/A-PVA-PWA) composite membranes were fabricated by solution blending and physical and chemical crosslinking methods to improve the properties of silicon-containing sulfonated polystyrene/acrylate (Si-sPS/A) membranes. FTIR spectra clearly show the existence of various interactions and a crosslinked silica network in composite membranes. The potential of the composites to act as proton exchange membranes in direct methanol fuel cells (DMFCs) was assessed by studying their thermal and hydrolytic stability, swelling, methanol diffusion coefficient, proton conductivity and selectivity. TGA measurements show that the composite membranes possess good thermal stability up to 190°C, satisfying the requirement for fuel cell operation. Compared to the unmodified membrane, the composites exhibit less swelling and a superior methanol barrier. Most importantly, all of the composite membranes have significantly lower methanol diffusion coefficients and significantly higher selectivity than those of Nafion® 117. The Si-sPS/A-20PVA-20PWA membrane is the best applicant for use in DMFCs because it exhibits an optimized selectivity value (5.93×105 Sscm−3) that is approximately 7.8 times of that of the unmodified membrane and is 27.8 times higher than that of Nafion® 117. [ABSTRACT FROM AUTHOR]

Abstract: A series of silicon-containing sulfonated polystyrene/acrylate (Si-sPS/A) nanoparticles are successfully synthesized via simple emulsion polymerization method. The Si-sPS/A latexes show good film-forming capability and the self-crosslinked organic/inorganic proton exchange membranes are prepared by pouring the Si-sPS/A nanoparticle latexes into glass plates and drying at 60°C for 10h and 120°C for 2h. The potential of the membranes in direct methanol fuel cells (DMFCs) is characterized preliminarily by studying their thermal stability, ion-exchange capacity, water uptake, methanol diffusion coefficient, proton conductivity and selectivity (proton conductivity/methanol diffusion coefficient). The results indicate that these membranes possess excellent thermal stability and methanol barrier due to the existence of self-crosslinked silica network. In addition, the proton conductivity of the membranes is in the range of 10−3–10−2 Scm−1 and all the membranes show much higher selectivity in comparison with Nafion® 117. These results suggest that the self-crosslinked organic/inorganic proton exchange membranes are particularly promising in DMFC applications. [Copyright &y& Elsevier]

Abstract A novel process integration occupying high cell-density culture (HCDC) and simultaneous saccharification and fermentation (SSF) in one bioreactor achieved an efficient ethanol production in this study. The effect of inoculum sizes of S. cerevisiae for ethanol production in SSF was investigated. High ethanol production was obtained with high inoculums size of cells from 4 to 30 kg﹒m−3. The process integration including HCDC and SSF in one reactor was achieved. A production of 35.2 kg﹒m−3 cells was obtained with HCDC in aerobic conditions. Cellulase and pretreated corn stover were added into the fermentation broth in the same bioreactor, and the SSF procedure was initiated in anaerobic conditions. The highest ethanol titer of 17.08kg﹒m−3 corresponding to 101.50% theoretical yield was obtained, and the peak value time was 24 h with β-glucosidase addition in the HCDC-SSF system. The highest ethanol titer of 11.01 kg﹒m−3, corresponding 65.41% theoretical yield, was obtained at 72 h with regular SSF. Graphical abstract Image 1 Highlights • The high cell density of yeast promoted the ethanol production in SSF. • A novel process integration occupying high cell density culture and SSF shortened the overall process time and enhanced the ethanol production. • The yeast culturing and SSF were combined in one bioreactor. [ABSTRACT FROM AUTHOR]

A series of poly(vinyl alcohol) (PVA)-based organic–inorganic crosslinked polymer electrolyte membranes with PVA and poly(methacrylic acid-2-acrylamido-2-methyl-1-propanesulfonic acid-vinyltriethoxysilicone) (PMAV) are prepared for direct methanol fuel cell applications. Fourier transform infrared (FTIR) spectroscopy measurements clearly reveal the existence of crosslinking reactions and molecular interactions in PVA–PMAV membranes. The results of TGA show that the PVA–PMAV membranes possess good thermal stability. The uptake behavior, methanol diffusion coefficient, proton conductivity and selectivity of membranes also are investigated as function of PMAV content. The results indicate that the PVA-based organic–inorganic crosslinked membranes are particularly promising to be used as polymer electrolyte membranes due to their excellent methanol barrier property, suitable proton conductivity and high selectivity. [ABSTRACT FROM AUTHOR]

Biogas slurry is not suitable for liquid fertilizer due to its high amounts of volatile materials being of complicated composition and peculiar smell. In order to remove volatiles from biogas slurry efficiently, the dynamic headspace and gas chromatography-mass spectrometry were used to clear the composition of volatiles. Nitrogen stripping and superfluous ozone were also used to remove volatiles from biogas slurry. The results showed that there were 21 kinds of volatile compounds in the biogas slurry, including sulfur compounds, organic amines, benzene, halogen generation of hydrocarbons and alkanes, some of which had strong peculiar smell. The volatile compounds in biogas slurry can be removed with the rate of 53.0% by nitrogen stripping and with rate of 81.7% by the oxidization and stripping of the superfluous ozone. On this basis, the removal rate of the volatile compounds reached 99.2% by chloroform and n -hexane extraction, and almost all of odor was eliminated. The contents of some dissolved organic compounds decreased obviously and however main plant nutrients had no significant change in the biogas slurry after being treated. [ABSTRACT FROM AUTHOR]