Search

pH/Laccase responsive microcapsules with tailorable shells were prepared by the layer-by-layer deposition of sodium lignosulfonate and chitosan for protecting photosensitive avermectin.

Pretreatment is the initial stage of lignocellulosic biorefinery process, but is limited by the time-consuming processes, harsh conditions and/or undesirable products. Herein, a mild (60 °C) and highly efficient pretreatment strategy is developed. The novel mechanocatalytical reaction system driven by fluid shear force helps to exfoliate cellulose from lignocellulose, and the heat generated by the shear process can be used to precipitate and recover the dissolved cellulose from the precooled NaOH/urea solution. The regenerated cellulose shows satisfying crystal structure (cellulose II), significantly decreased crystallinity and nearly tripled enzymolysis glucose yield. Almost 90% of lignin and hemicellulose could be rapidly separated. The separated lignin shows a nearly native structure with 64% β-O-4 linkage, which is even higher than the ball-milling lignin (60%). This research provides a theoretical guidance for the mild pretreatment of lignocellulosic biomass, which will push the application of mechanocatalytical reaction system in biorefinery processes on a large scale.

Aqueous reactions may turn precursors into light-absorbing and toxic products, leading to air quality deterioration and adverse health effects. In this study, we comprehensively investigated eugenol photooxidation (a representative biomass-burning-emitted, highly substituted phenolic compound) in the bulk aqueous phase with direct photolysis, a hydroxyl radical (OH), and an organic triplet excited state (3C∗). Results show that the degradation rates of eugenol followed the order of 3C∗> OH > direct photolysis. During the 3C∗-initiated oxidation, different reactive oxygen species (ROS), including 3C∗, OH, 1O2, and O2⚫-, can participate in the oxidation of eugenol, quenching experiments verified 3C∗ was the most important one, while, during OH-initiated oxidation, O2⚫- was a more important ROS than OH for degrading eugenol. The rate constants under saturated O2, air, and N2 followed the order of kO2>kAir>kN2 for both direct photolysis and OH-initiated oxidation but changed to kAir>kN2>kO2 for 3C∗-mediated oxidation. pH and dissolved oxygen (DO) levels both decreased during oxidation, indicating the formation of acids and the participation of DO in oxidation. Ultraviolet and visible (UV-vis) light absorption spectra of the reaction products showed a clear absorbance enhancement in the 300–400 nm range for all three sets of experiments, and new fluorescence at excitation/emission =250/ (400–500) nm appeared, suggesting the formation of new chromophores and fluorophores (brown carbon species). These species were likely attributed to humic-like substances (HULIS), as shown by the increases in HULIS concentrations during oxidation. Large mass yields of products (140 %–197 %) after 23 h of illumination were obtained, and high oxidation degrees of these products were also observed. Correspondingly, a series of oxygenated compounds were identified, and a detailed reaction mechanism with functionalization as a dominant pathway was proposed. At last, the dithiothreitol (DTT) assay was applied to assess the oxidation potential of the reaction products, and the end products of all three sets of experiments showed higher DTT consumption rates than those of eugenol, indicating that more toxic species were produced upon aqueous oxidation. Overall, our results from using eugenol as a model compound, underscore the potential importance of the aqueous processing of biomass burning emissions in secondary organic aerosol (SOA) formation.

To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e., variation in initial concentration of total carbon, glucose content in initial carbon substrate, and light intensity, were experimentally investigated using response surface methodology (RSM) with a Box-Behnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6 mL h−1 L−1 was attained under conditions of 39 mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate, and 12.6 W m−2 light intensity at light wavelength of 590 nm. Synergic effects of metabolizing such a well-formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production, were attributed to this carbon substrate that can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

The soil arching effect can significantly impact the bearing characteristics of the slope anchored anti-slide pile. Therefore, it is very important to investigate the internal force characteristics of the soil arch and the mechanism of pile-soil interaction. In this paper, the evolution mechanism and influencing parameters of the soil arching effect of anchored anti-slide pile are analyzed, from a qualitative and quantitative perspective through model tests and numerical simulation methods. Findings are summarized as follows: 1) the formation and evolution of the soil arches can be roughly divided into three stages: the initial stage, the development and formation of soil arches, and the failure and re-formation of soil arches. The stable arch feet are firstly formed, and a complete arch is generated. Then the landslide thrust is transmitted to form a stable anti-slide pile structure, so the anchored anti-slide pile can play a role in slope anti-slide. 2) During the formation and evolution of the soil arches, the soil particles between the piles transfer the landslide thrust to the anti-slide pile through the soil arches. 3) The bearing capacity of the soil arches decreases with the increase of the pile spacing. And the increase of the soil compaction can efficiently increase the bearing capacity of the soil arches and give full play to the role of slope anti-slide. 4) The growing of soil particle size, the enhancement of soil particle friction coefficient, and the decreasing of corresponding soil void ratio are all conducive to the formation of the soil arches. These can benefit the anti-sliding effect of the anchored anti-slide piles in engineering application.

Atmospheric aerosols consisting of organic and inorganic components may undergo liquid–liquid phase separation (LLPS) and liquid–solid phase transitions during ambient relative humidity (RH) fluctuation. However, the knowledge of dynamic phase evolution processes for mixed organic–inorganic particles is scarce. Here we present a universal and visualized observation of LLPS, efflorescence and deliquescence transitions as well as hygroscopic growth of laboratory-generated mixed 1, 2, 6-hexanetriol / ammonium sulfate (AS) particles with different organic–inorganic mole ratios (OIR = 1:4, 1:2, 1:1, 2:1 and 4:1) with high time resolution (0.5 s) using an optical microscope operated with a video camera. The optical images suggest that an inner AS solution phase is surrounded by an outer organic-rich phase after LLPS for all mixed particles. The LLPS mechanism for particles with different OIRs is found to be distinct; meanwhile, multiple mechanisms may dominate successively in individual particles with a certain OIR, somewhat inconsistently with previously reported observations. More importantly, another phase separation in the inner AS solution phase, defined as secondary LLPS here, is observed for OIR = 1:1, 1:2 and 1:4 particles. The secondary LLPS may be attributed to the formation of more concentrated AS inclusions in the inner phase and becomes more obvious with decreasing RH and increasing AS mole fraction. Furthermore, the changes in size and number of AS inclusions during LLPS are quantitatively characterized, which further illustrate the equilibrium partitioning process of organic and inorganic components. These experimental results have significant implications for the revelation of complex phase transitions of internally mixed atmospheric particles and evaluation of liquid–liquid and liquid–solid equilibria in thermodynamic models.

The nitrate depletion and HNO3 release in internally mixed nitrate and dicarboxylic acids (DCAs) particles have been widely detected in field and laboratory studies. Nevertheless, considerable discrepancies are still present among these measurements, and the influence factors for this acid-displacement reaction have not yet been elucidated. In this work, the hygroscopic growth and chemical composition evolution of mixtures of NaNO3 and DCAs, i.e., oxalic acid (OA), malonic acid (MA), and glutaric acid (GA), were measured using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and vacuum FTIR techniques. The HNO3 release from NaNO3/OA mixtures was observed in both the measurements, owing to the relatively high acidity of OA. At the same time, the NaNO3 phase state was found to act as a key regulator of nitrate depletion. Amorphous NaNO3 solids at relative humidity (RH) < 5 % were inert to liquid OA. With increasing RH, the mixtures experienced three interesting stages of phase changes showing different HNO3 release rates, e.g., at around 15 % RH, the slow HNO3 release was detected by the vacuum IR spectra, potentially indicating the transformation of amorphous solids to semisolid NaNO3; in the second stage (sudden RH increase from ~ 15 % to 61 %), the HNO3 release rate was increased by about an order of magnitude; when NaNO3 deliquescence occurred in the third stage, this displacement reaction proceeded due to more available NO3- ions formation. Compared to OA, MA and GA reacted with nitrate only in vacuum FTIR measurement, while in ATR-FTIR measurement, the mixtures tended to be effloresced completely without nitrate depletion. Further, the influences of ambient pressure, chemical composition, and water activity on HNO3 release rates were estimated via Maxwell steady-state diffusive mass transfer equation. The results showed that weaker acidity of MA and GA as well as relatively lower HNO3 diffusion rate in ambient gas phase mainly contributed to the unobserved nitrate depletion in ATR-FTIR measurement. Our findings reveal that chemical component, phase state, and water activity of particles, as well as HNO3 gas phase diffusion play crucial roles on HNO3 release from nitrate and DCAs mixtures. This work may provide a new perspective on nitrate depletion in the aging processes during transport of atmospheric aerosols.

The hygroscopic behaviors and phase changes of inorganic aerosols have been widely explored, but little is known on the hygroscopicity of soluble carbonates. The hydrated states of solid Na2CO3 particles in an air environment remain largely unclear. In this work, the hygroscopic growth, hydrated form transformations, and influence of internal Li2CO3 on phase transitions of Na2CO3 particles are investigated in linear and pulsed relative humidity (RH) changing modes by the vacuum Fourier transform infrared (FTIR) technique. For pure Na2CO3, aqueous droplets effloresced to a mixture of anhydrous Na2CO3 and Na2CO3·H2O with the initial efflorescence relative humidity (ERH) of 50.8%, probably concerning the formation of Na2CO3·10H2O in the conversion from aqueous to anhydrous Na2CO3. A reverse process is presented during the three-stage deliquescence transition beginning at ∼60.1% RH; i.e., anhydrous Na2CO3 transforms into aqueous Na2CO3 and Na2CO3·10H2O in stage I, Na2CO3·10H2O dissolves to aqueous Na2CO3 in stage II, and Na2CO3·H2O dissolves into aqueous Na2CO3 in stage III. For internally mixed Na2CO3/Li2CO3 particles, a double salt, LiNaCO3, is found in mixed crystalline phases for the first time, leading to the eutonic composition with Na2CO3. The experimental observations point to the excess of LiNaCO3 and complete consumption of Na2CO3 in eutonic composition formation, which results in the absence of Na2CO3 hydrates during phase transitions. The results provide key data for model simulations of hygroscopic properties and phase transitions of Na2CO3 as well as mixed soluble carbonates.

Oxygen vacancies (OVs) defects in metal oxide-based photocatalysts play a crucial role in improving the charge carrier separation efficiencies to enhance the photocatalytic performances. In this work, OVs were introduced in 3D Bi2MoO6 microspheres through a facile and fast microwave-assisted method via the modulation of tetramethylethylenediamine (TMEDA). EPR, Raman and XPS results demonstrated that large amounts of oxygen vacancies were formed on the surface of BMO microspheres. The photocatalytic properties of the samples were studied by degradation of tetracycline (TC) under visible light. The optimal Bi2MoO6 with OVs exhibited optimum photocatalytic activity, and the degradation rate was 7.0 times higher than that of pristine Bi2MoO6. This enhancement can be attributed to the 3D structure furnishing more surface active sites and suitable OVs defects favoring the electron–hole separation. Moreover, the defective Bi2MoO6 microspheres exhibit high stability because the photocatalytic activity remains almost unchanged after 5 cycles, making them favorable for practical applications. Finally, a possible visible light photocatalysis mechanism for the degradation of TC was tentatively proposed.

A ternary photocatalyst, Fe3O4-loaded g-C3N4/C-layered composite (g-C3N4/C/Fe3O4) was fabricated by a facile sonication and in situ precipitation technique. Carbon nanosheets were prepared using the remaining non-metallic components of waste printed circuit boards as carbon sources. In this hybrid structure, g-C3N4 was immobilized on the surfaces of carbon nanosheets to form a layered composite, and 10–15 nm Fe3O4 nanoparticles are uniformly deposited on the surface of the composite material. The photocatalytic performance of the catalyst was studied by degrading tetracycline (TC) under simulated sunlight. The results showed that the photoactivity of the g-C3N4/C/Fe3O4 composite to TC was significantly enhanced, and the degradation rate was 10.07 times higher than that of pure g-C3N4, which was attributed to Fe3O4 nanoparticles and carbon nanosheets. Carbon sheets with good conductivity are an excellent electron transporter, which promotes the separation of photogenerated carriers and the Fe3O4 nanoparticles can utilize electrons effectively as a center of oxidation–reduction. Moreover, a possible photocatalytic mechanism for the excellent photocatalytic performance was proposed.

In ambient air, aqueous-phase oxidation may turn precursors into more light-absorbing and toxic products, leading to air quality deterioration and adverse health effects. In this study, we investigated eugenol degradation in aqueous phase under direct photolysis, and triplet excited organic (3C*) and hydroxyl radical (OH) as oxidants. Results showed degradation rates of eugenol followed the order of 3C* > OH > direct photolysis. Relative contributions of reactive oxygen species (ROS) and 3C* were evaluated via quenching and O2-free experiments. 3C* played a dominant role in eugenol degradation for 3C*-initiated oxidation, while both O2 and O2•-generated were important for eugenol degradation for OH-initiated oxidation. Rate constants under O2, air and N2 followed the order of ko2＞kAir＞kN2 under both direct photolysis and OH oxidation, and it changed to kAir＞kN2＞ko2 in 3C*-initiated oxidation. Light absorption spectra showed absorbance at 300–400 nm increased as photolysis progressed, and there were new broad fluorescent spectra at excitation/emission (Ex/Em) = 250/(400–500) nm, suggesting the formation of new chromophores and fluorophores, such as humic-like substances (HULIS). Additionally, distinct fluorescence peaks appeared at Ex/Em=(300–350)/300 nm at different stages. Concentration of generated HULIS increased gradually over time, then leveled off. Dithiothreitol (DTT) assay was applied to assess the oxidation potential of products, which was greater than pure eugenol, suggesting more harmful species were produced during oxidation. Detailed reaction pathways were elucidated via analyses of chemical characteristics of the products.

The development of biogas projects feed by lignocellulosic biomass has been constrained by the high cost of pre- and post-treatment. In this study, a novel strategy for pretreatment by using two by-products, i.e., CO2 and liquid digestate (LD), generated from anaerobic digestion (AD) was developed to overcome these shortcomings. Results showed that corn straw pretreated in LD pressurized under 1 Mpa CO2 at 55 ℃ resulted in increased glucose and xylose contents and a 9.80% decrease in cellulose crystallinity. After 45 days of AD conversion, the methane yield increased by 50.97% compared with untreated straw. However, pretreatment in LD pressurized under 1 Mpa CO2 at 170 ℃ produced 5-hydroxymethylfurfural and furfural, which led to a decrease in methane production from the straw in the subsequent AD conversion. The alteration of the microbial community in the pretreated slurry at 55 °C was another potential contributor to the enhanced performance of AD.

To develop an efficient photofermentative process capable of higher rate biohydrogen production using carbon components of lignocellulosic hydrolysate, a desired carbon substrate by mixing xylose with glucose was formulated. Effects of crucial process parameters affecting cellular biochemical reaction of hydrogen by photosynthetic bacteria (PSB), i.e variation in initial concentration of total carbon, glucose content in initial carbon substrate, as well as light intensity were experimental investigated using response surface methodology (RSM) with a Box-Benhnken design (BBD). Hydrogen production rate (HPR) in the maximum value of 30.6 mL h− 1 L− 1 was attained under conditions of 39 mM initial concentration of total carbon, 59% (mol/mol) glucose content in initial carbon substrate and 12.6 W m− 2 light intensity at light wavelength of 590 nm. Synergic effects of metabolizing such a well formulated carbon substrate for sustaining the active microbial synthesis to sufficiently accumulate biomass in bioreactor, as well as stimulating enzyme activity of nitrogenase for the higher rate biohydrogen production were attributed to this carbon substrate can enable PSB to maintain the relatively consistent microenvironment in suitable culture pH condition during the optimized photofermentative process.

Visible-lightdriven C–TiO2 nanocomposites were prepared via a simple calcination and acid etching process. The C–TiO2 nanocomposites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and high-resolution TEM. The results showed that TiO2 nanoparticles were combined with a porous carbon layer through surface C–O groups, which facilitates the strong interface interaction. The interface combination of nano-TiO2 and carbon material increases the specific surface area of nano-TiO2, widens the range of light response, and improves the efficiency of light-induced electron migration. The visible-light photocatalytic activity of the prepared photocatalyst was evaluated by the decomposition of tetracycline aqueous solution. Compared with that of pure TiO2, the photocatalytic activity of C–TiO2 nanocomposites was significantly improved. Furthermore, a possible photocatalytic mechanism was also tentatively proposed. This work can promote th...

Photofermentative hydrogen production at higher rate is desirable to make the technology of biological hydrogen production in practical application. An easy fabricating alveolar panel photobioreactor with high surface-to-volume ratio was proposed in this study to realize biofilm formation and used for developing a continuous bioprocess of hydrogen production. Effects of key operating parameters, i.e. variation in intensity of incident light, initial concentration of carbon substrate and flow rate on the rate of nitrogenase-based H2 production were investigated using response surface methodology (RSM) with Box-Behnken design. Surface and contour plots of the fitted regression model revealed that optimum H2 production rate of 57.6 mL/h/L was obtained at 125.9 μE/m2/s incident light intensity at 590 nm light wavelength, 52.4 mM initial concentration of carbon substrate and 209 mL/h flow rate. Regular groove surfaces within this photobioreactor were considered to have mutual effects on enhancement of continuous hydrogen production by enriching bacterial cell density, enhancing mass transfer of carbon substrate to facilitate release of protons and electrons, enhancing removal of molecular H2, and uniformly distribution of incident light within the photobioreactor for sufficient conversion into ATPs.

Secondary organic aerosol (SOA) species formed in atmospheric aqueous phases is recently recognized as an important contributor to fine aerosols, which is known to be a prominent human health risk factor internationally. This work, for the first time, systematically investigated aqueous-phase photochemical oxidation of 4-ethylphenol (4-EP) - a model compound from biomass burning and a surrogate of intermediate volatility organic compounds, under both ultraviolet (UV) (Hg lamp) and simulated sunlight (Xe lamp). We found that 4-EP could degrade upon hydroxal radical ( OH) oxidation under UV light nearly 15 times faster than that under simulated sunlight, but large aqueous SOA (aqSOA) yields (108%–122%) were observed under both situations. AqSOA masses and oxidation states continuously increased under simulated sunlight, yet they increased first then decreased quickly under UV light. We proposed a reaction scheme based on identified products, showing that oligomerization, functionalization and fragmentation all can occur during 4-EP oxidation. Our results demonstrate that OH radical may suppress oligomerization and functionalization, but is favorable for fragmentation. Under UV light with H2O2 (high OH), fragmentation was dominant, producing more volatile and smaller molecules, and less aqSOA in later oxidation; Under simulated sunlight with H2O2 (moderate OH), functionalization that can form hydroxylated monomer was more important. Moreover, 4-EP oxidation by the organic triplet excited state (3C*) could form species with stronger visible light absorptivity than those from OH-mediated oxidation, and the absorptivity showed positive link with contents of humic-like substances.

The hygroscopicity and phase state of atmospheric aerosols, depending on relative humidity (RH), dominate their impacts on global climate and heterogeneous atmospheric chemistry. It is challenging to achieve full course measurements on hygroscopic mass growth factors (MGFs), deliquescence relative humidity (DRH), efflorescence relative humidity (ERH) and efflorescence kinetics of aerosols at different ambient RH, which concerns the gas, liquid and solid phases. The combination of a rapid scan vacuum FTIR and a RH pulsed controlling system allowed us to directly and synchronously determine ambient RH and MGFs of aerosols, as well as nucleation rates in the efflorescence process with a subsecond time resolution. With an excellent signal-to-noise ratio and high time resolution spectra, the vacuum FTIR method allowed for real-time in situ measurements of water partitioning between gas and particle phases as it changed with RH, as well as the ratio between the number of crystallized aerosol droplets and the total number of particles during the efflorescence of aerosols. The hygroscopicity and efflorescence kinetics of NaCl and (NH4)2SO4 aerosols were studied in linear RH change mode and in pulsed RH change mode. The measured MGF values, DRH and ERH agreed well with theoretical data from the Extended Aerosol Inorganic Model (EAIM) and literature for both the linear and pulsed RH change modes. In addition, the pulsed RH mode also provided both heterogeneous and homogeneous nucleation rates for NaCl and (NH4)2SO4 aerosols. There were significant advantages of the vacuum FTIR method combined with the pulsed RH controlling technique. First, the RH was continuously changed and was determined in real-time with a time resolution of 0.12 s in the pulsed mode. During the RH change process, the water content in the aerosols was measured synchronously with the same time resolution, allowing for high-efficiency measurements of MGFs, ERH and DRH. The deviations of measured MGFs from the EAIM predictions in the RH range of 75–55% were less than ±3.3%. Second, FTIR spectroscopy was sensitive to phase transitions, which provided quantitative information on the ratio of the number of aerosols transformed from droplets to solid particles at ERH, allowing for the measurement of nucleation kinetics during the efflorescence of aerosols.

In this study, we investigate the soil gas concentration attenuation with diffusive transport in lateral and vertical transport in cases with surface pavements with a pilot-scale tank. Three scenarios were investigated, one with a completely open soil surface and the other two involving partially paved soil surface. The results, on the one hand, indicate that the soil gas concentration generally decreases linearly and exponentially in the vertical and horizontal transport directions, respectively, generally in accordance with available modeling studies. On the other hand, our experiment shows that low-permeability ground covers can increase shallow soil gas concentrations beneath the pavement by at most 3–4 times, inducing higher subslab concentration than that below open ground surface, even if the latter is obtained at a closer location to vapor source. For cases with uniform soil properties, our study suggests exterior soil gas sample should be taken at a depth below the building foundation by half of the building footprint size, if the vapor source is laterally extensive relative to the building footprint, or by 1 m and 2–3 m for slab-on-grade and basement scenarios, respectively, if the vapor source is located laterally away from the building.

The experimental data for "Observations on hygroscopic growth and phase transitions of 1, 2, 6-hexanetriol/(NH4)2SO4 mixed particles: Investigation of liquid-liquid phase separation (LLPS) dynamic process and mechanism and secondary LLPS during the dehumidification"

With regard to the treatment of multicomponent wastewaters, to construct multifunctional super-wetting membranes is highly attractive in current decade. In this work, a low-cost and novel NiFe

Upland rice is a distinct ecotype that grows in aerobic environments and tolerates drought stress. However, the genetic basis of its drought resistance is unclear. Here, using an integrative approach combining a genome-wide association study with analyses of introgression lines and transcriptomic profiles, we identify a gene, DROUGHT1 (DROT1), encoding a COBRA-like protein that confers drought resistance in rice. DROT1 is specifically expressed in vascular bundles and is directly repressed by ERF3 and activated by ERF71, both drought-responsive transcription factors. DROT1 improves drought resistance by adjusting cell wall structure by increasing cellulose content and maintaining cellulose crystallinity. A C-to-T single-nucleotide variation in the promoter increases DROT1 expression and drought resistance in upland rice. The potential elite haplotype of DROT1 in upland rice could originate in wild rice (O. rufipogon) and may be beneficial for breeding upland rice varieties.