Novel strategy for reusing agricultural mulch film residual by iron modification for arsenic removal in gold-smelting wastewater.

In gold-smelting wastewater after the original treatment process of flocculation and precipitation using mainly lime, a mixture of As, Cu, Pb, Mn, Zn, Al, Ni, and Fe existed with an arsenic concentration of 813.07 mg/L and other ions' concentration at ug/L levels. In this work, a new clean process of mainly adsorption with self-made adsorbent Fe-PE, which was synthesized by loading ferric lignin on agricultural mulch film residual, was investigated to purify and remove arsenic from gold-smelting wastewater. A batch of column experiments was investigated to explore the reaction behavior between wastewater and adsorbent Fe-PE. The results showed while operating the adsorption columns at a pilot scale for 68 days, the arsenic concentration in the effluent was below 0.5 mg/L, and there was no significant change in the concentration of co-existing metal ions, indicating that Fe-PE had a good selective adsorption performance for arsenic in wastewater. Furthermore, Fe-PE did not dissolve and release Fe ions in wastewater, and the whole process could not produce sludge. This work first suggested an efficient and potential application for the purification and removal of arsenic from gold-smelting wastewater with agricultural mulch film residual after chemical modification, which will provide a novel strategy for reusing the agricultural mulch film residual.

A Theoretical Study of H-Abstractions of Benzaldehyde by H, O3(P), 3O2, OH, HO2, and CH3 Radicals: Ab Initio Rate Coefficients and Their Uncertainty Quantification.

Benzaldehyde is a vital intermediate during the oxidation of toluene and oxygenated aromatics, but benzaldehyde's combustion chemistry currently gains little attention. The H-atom abstraction of benzaldehyde is one critical reaction class, yet its rate coefficients rely on the analogy of molecular similarity. For this reason, we have employed the ab initio calculations at the CCSD(T)/cc-pVTZ//M06-2X/6-311+g(d,p) level of theory, along with the RRKM master equation to predict the rate coefficients of H-abstraction reactions of benzaldehyde by H, O3(P), 3O2, OH, HO2, and CH3 radicals. The calculated rate coefficients of benzaldehyde + OH generally agree with literature measurements. From the branching ratio analysis, all the H-abstractions from ring sites can be neglected in kinetic model construction except by OH radical at temperature above 1700 K, where the ring sites contribute a relatively large branching ratio to consume benzaldehyde. A random sampling method has been used to estimate the global uncertainty in the calculated rate coefficients. The logarithm of uncertainty is proportional to the reciprocal temperature, and the global uncertainty is primarily derived from the energy errors and is almost independent of the attacking species. Comparison between benzaldehyde and acetaldehyde reveals that their rate coefficients are consistent only in H-abstractions by H and HO2 but are conflictive in other reactions, especially in the case of OH. By incorporating the new calculations, existing models show a faster prediction in autoignition delay times of benzaldehyde. This study reports the first high-level ab initio calculations for the H-atom abstraction reaction class of benzaldehyde. It is necessary for the future comprehensive kinetic modeling of aromatic aldehyde.

Hydrothermal carbonization of food waste as sustainable energy conversion path.

Every day, a large amount of food waste (FW) is released into the environment, causing financial loss and unpredictable consequences in the world, highlighting the urgency of finding a suitable approach to treating FW. As moisture content makes up 75% of the FW, hydrothermal carbonization (HTC) is a beneficial process for the treatment of FW since it does not require extensive drying. Moreover, the process is considered favorable for carbon sequestration to mitigate climate change in comparison with other processes because the majority of the carbon in FW is integrated into hydrochar. In this work, the reaction mechanism and factors affecting the HTC of FW are scrutinized. Moreover, the physicochemical properties of products after the HTC of FW are critically presented. In general, HTC of FW is considered a promising approach aiming to attain simultaneously-two core benefits on economy and energy in the sustainable development strategy.

Efficient adsorption of heavy metals from wastewater on nanocomposite beads prepared by chitosan and paper sludge.

Chitosan was commonly used with inorganic salt and organic compounds to prepare adsorption material for water treatment. Different materials were mixed for the preparation, leading to a high cost for water treatment. Sludge from papermaking has abundant fiber and inorganic salt, which can reduce the addition of raw materials in preparing the adsorption material and thus lower the cost. This work used recycled industrial paper sludge to prepare adsorption material to remove heavy metals from wastewater. The adsorption properties of the prepared sludge-chitosan material for Cu2+ and Cr3+ in wastewater were investigated. The impacts of adsorption time, pH, and initial concentrations of Cu2+ and Cr3+ on adsorption amount were studied and optimized. The saturated adsorption capacity of sludge-chitosan material for Cu2+ and Cr3+ can reach 114.6 and 110.3 mg/g. The adsorption kinetics satisfied the pseudo-second-order model, indicating two modes, physical diffusion, and chem-sorption, in the heavy metal adsorption by the sludge-chitosan materials. Physical distribution has little Effect on chemical adsorption. The materials can be applied to treating Cu2+ and Cr3+ containing wastewater with the proposed cheap and readily available sludge-chitosan material. The results confirmed that sludge-chitosan material possessed good regeneration performance and was an ideal adsorbent.

Loading ferric lignin on polyethylene film and its influence on arsenic-polluted soil and growth of romaine lettuce plant.

This work developed a composite (Pe-FeLs) which loaded ferric lignin on polyethylene film (PE film) by chemical modification and physico-chemically characterized by Microscope, FESEM with elemental mapping analysis, and XRD. Microscope pictures showed that chemical modification did not destroy the appearance of PE film. The FESEM images of Pe-FeLs showed the well-distributed clusters could be clearly seen and most of the particles were spherical morphology. Elemental mapping of individual element on Pe-FeLs clearly indicated the existing of iron. The XRD pattern showed the amorphous hydroxides of iron on Pe-FeLs. In arsenic solution, the total arsenic adsorption capacity of Pe-FeLs was much higher than that of ferric lignin and PE, which showed Pe-FeLs had the ability to adsorb arsenic. For making Pe-FeLs work well in the soil, a Pe-FeLs system was set up with plastic grid plate, PE film with holes, Pe-FeLs, PE film, and plastic grid plate from the upper to bottom in order. With applying Pe-FeLs system under the soil, arsenic was significantly reduced by 25.5 ~ 53.4% in heavily, moderately, and lower arsenic-polluted soils, the biomass of the romaine lettuce increased and arsenic accumulation in the romaine lettuce decreased.

Liquid hot water as sustainable biomass pretreatment technique for bioenergy production: A review.

In recent years, lignocellulosic biomass has emerged as one of the most versatile energy sources among the research community for the production of biofuels and value-added chemicals. However, biomass pretreatment plays an important role in reducing the recalcitrant properties of lignocellulose, leading to superior quality of target products in bioenergy production. Among existing pretreatment techniques, liquid hot water (LHW) pretreatment has several outstanding advantages compared to others including minimum formation of monomeric sugars, significant removal of hemicellulose, and positive environmental impacts; however, several constraints of LHW pretreatment should be clarified. This contribution aims to provide a comprehensive analysis of reaction mechanism, reactor characteristics, influencing factors, techno-economic aspects, challenges, and prospects for LHW-based biomass pretreatment. Generally, LHW pretreatment could be widely employed in bioenergy processing from biomass, but circular economy-based advanced pretreatment techniques should be further studied in the future to achieve maximum efficiency, and minimum cost and drawbacks.

Chemical characterization of Tianshan green tea polysaccharides and its protective effects on cell oxidative injury.

The purpose of this study was to analyze the chemical characterization of Tianshan green tea polysaccharides (TSPS), and evaluate its antioxidant activity by chemical-based and cellular-based antioxidant models in vitro. The results showed that the TSPS were composed of mannose, ribose, rhamnose, glucuronic acid, galacturonic acid, glucose, galactose, arabinose, and fucose with a molar ratio of 14.5:33.5:10.5:6.5:111.5:22.3:59.5:51: 1.0, and an average molecular weight of 19.49 kDa. TSPS exhibited excellent antioxidant ability to DPPH radical, hydroxyl radical, and ABTS radical, and enhanced the ferric-reducing power (FRAP). The antioxidation model of LO2 and HepG2 cells was established, and found that TSPS had no significant toxicity to either of the two cells at the range of 0.1-5 mg/mL, but clearly protected cells from H2 O2 -induced apoptosis and significantly reduced intracellular ROS level. In addition, the activities of antioxidant-associated enzymes were detected in LO2 cells, which suggested that TSPS could significantly improve the activities of SOD and CAT enzyme when the concentration was higher than 0.5 mg/mL. Furthermore, TSPS activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway by promoting Nrf2 nuclear translocation and inhibited the expression of Kelch-like ECH-associated protein 1 (Keap-1) and enhanced the expression of heme oxygenase-1 (HO-1). PRACTICAL APPLICATIONS: Tianshan green tea, a local variety in Fujian Province, belongs to unfermented tea. Polysaccharide is considered as the most promising component in Tianshan green tea. This study showed that TSPS had excellent antioxidant activity and had no significant toxicity to cells, which provides a scientific foundation and new idea for its further development and application in functional foods.

Rapid determination of trace Cu2+ by an in-syringe membrane SPE and membrane solid-phase spectral technique.

A new in-syringe membrane SPE and solid-phase visible spectral method was proposed for the rapid extraction and visible spectral determination of trace Cu2+. The chelation and membrane SPE can be accomplished in a syringe. The yellow Cu(DDTC)2 complex was separated using a polyethersulfone membrane from the sample solution. Then, the complex can be detected directly on the polyethersulfone membrane utilizing solid-phase visible absorbance spectra without elution. The proposed method simplified the experimental procedure and improved the sensitivity to the µg L-1 level. Furthermore, this method is environmentally friendly since it avoids the use of organic solvents. After the investigation of the influence of different variables on the membrane SPE procedure, water and blood plasma were analyzed to validate the proposed method. A LOD of 0.04 µg L-1 and recoveries of 96.0-103.7% confirmed that the present work can be applied for the determination of trace Cu2+ in water and blood plasma samples.

The complete mitochondrial genome of Arhopalus unicolor (Coleoptera: Cerambycidae).

In this study, the complete mitochondrial genome of Arhopalus unicolor was first sequenced. The length of the complete mitochondria genome of A. unicolor was 15,760 bp with 19.0% GC content, including 40.5% A, 10.8% C, 8.2% G and 40.5% T. There were 13 protein-coding genes (CDS), 22 transfer RNA genes (tRNA), 2 ribosomal RNA genes (rRNA), and an AT-rich region. Phylogenetic analysis showed that A. unicolor was closely related to Spondylis buprestoides. This study provides useful genetic information for subsequent prevention of A. unicolor.

Theoretical studies on the initial reaction kinetics and mechanisms of p-, m- and o-nitrotoluene.

The potential energy surfaces (PESs) of three nitrotoluene isomers, such as p-nitrotoluene, m-nitrotoluene, and o-nitrotoluene, have been theoretically built at the CCSD(T)/CBS level. The geometries of reactants, transition states (TSs) and products are optimized at the B3LYP/6-311++G(d,p) level. Results show that reactions of -NO2 isomerizing to ONO, and C-NO2 bond dissociation play important roles among all of the initial channels for p-nitrotoluene and m-nitrotoluene, and that the H atom migration and C-NO2 bond dissociation are dominant reactions for o-nitrotoluene. In addition, there exist pathways for three isomer conversions, but with high energy barriers. Rate constant calculations and branching ratio analyses further demonstrate that the isomerization reactions of O transfer are prominent at low to intermediate temperatures, whereas the direct C-NO2 bond dissociation reactions prevail at high temperatures for p-nitrotoluene and m-nitrotoluene, and that H atom migration is a predominant reaction for o-nitrotoluene, while C-NO2 bond dissociation becomes important by increasing the temperature.

The complete mitochondria genome of Sipalus gigas (Coleoptera: Curculionidae).

Sipalus gigas is the main pine-hole borer of Pinus. The length of the complete mitochondria genome of S. gigas was 17,120 bp with 33.6% GC content, there were 35 genes including 13 protein-coding genes (CDS), 20 transfer RNA genes (tRNAs), and two ribosomal RNA genes (rRNAs). This study provides useful genetic information for subsequent studying the prevention of S. gigas.

A Systematic Theoretical Kinetics Analysis for the Waddington Mechanism in the Low-Temperature Oxidation of Butene and Butanol Isomers.

The Waddington mechanism, or the Waddington-type reaction pathway, is crucial for low-temperature oxidation of both alkenes and alcohols. In this study, the Waddington mechanism in the oxidation chemistry of butene and butanol isomers was systematically investigated. Fundamental quantum chemical calculations were conducted for the rate constants and thermodynamic properties of the reactions and species in this mechanism. Calculations were performed using two different ab initio solvers: Gaussian 09 and Orca 4.0.0, and two different kinetic solvers: PAPR and MultiWell, comprehensively. Temperature- and pressure-dependent rate constants were performed based on the transition state theory, associated with the Rice Ramsperger Kassel Marcus and master equation theories. Temperature-dependent thermochemistry (enthalpies of formation, entropy, and heat capacity) of all major species was also conducted, based on the statistical thermodynamics. Of the two types of reaction, dissociation reactions were significantly faster than isomerization reactions, while the rate constants of both reactions converged toward higher temperatures. In comparison, between two ab initio solvers, the barrier height difference among all isomerization and dissociation reactions was about 2 and 0.5 kcal/mol, respectively, resulting in less than 50%, and a factor of 2-10 differences for the predicted rate coefficients of the two reaction types, respectively. Comparing the two kinetic solvers, the rate constants of the isomerization reactions showed less than a 32% difference, while the rate of one dissociation reaction (P1 ↔ WDT12) exhibited 1-2 orders of magnitude discrepancy. Compared with results from the literature, both reaction rate coefficients (R4 and R5 reaction systems) and species' thermochemistry (all closed shell molecules and open shell radicals R4 and R5) showed good agreement with the corresponding values obtained from the literature. All calculated results can be directly used for the chemical kinetic model development of butene and butanol isomer oxidation.

Subpatterns of Thin-Sheet Splash on a Smooth Surface.

When a droplet impacts a smooth solid surface with a sufficiently high inertia, a thin sheet is created and the whole droplet fluid then breaks apart. Latka, A. [Thin-sheet creation and threshold pressures in drop splashing. Soft Matter 2017, 13, 740-747] defined it as thin-sheet splash. In this work, we used a high-speed camera with a long-distance microscope and experimentally showed that thin-sheet splash can be subdivided into three distinct patterns in terms of breakup location. Specifically, pattern 1 is characterized by the breakup of the rim with the thin sheet being intact, pattern 2 by the almost simultaneous breakup of both the rim and the thin sheet, and pattern 3 by the breakup of the thin sheet followed by the breakup of the rim. The effects of the Weber number and the Ohnesorge number on the transitions of these subpatterns were determined over large ranges of their values, and a regime nomogram in the parametric space of We-Oh was obtained.

Auto-ignition behaviors of nitromethane in diluted oxygen in a rapid compression machine: Critical conditions for ignition, ignition delay times measurements, and kinetic modeling interpretation.

In this work, the weakest thermodynamic conditions for the auto-ignition of mixtures containing nitromethane were experimentally determined by using the rapid compression machine facility. Results show there is a narrow weak ignition region between ignition and non-ignition. The weak ignition region would disappear with the increase of the EOC (end of compression) pressure and nitromethane concentration. In addition, the ignition delay times for successful auto-ignition for different nitromethane concentrations and equivalence ratio mixtures were measured and compared. Results show that the dependence of nitromethane ignition on the equivalence ratio is weak. Subsequently, the measured ignition delay time data were employed to validate several kinetic models in literature and our previous model shows better agreement with experimental results, as well as other available literature data. Sensitivity analysis for the model reveals the importance of unimolecular decomposition and H-abstraction reactions for the ignition delay times in the temperature range studied herein. Finally, critical conditions for nitromethane ignition under extended conditions that are beyond the ability of the experimental facility were predicted.

Chemical Kinetics of H-Atom Abstraction from Ethanol by HȮ2: Implication for Combustion Modeling.

As a renewable source of energy, ethanol has been widely used in internal combustion engines as either a gasoline alternative fuel or a fuel additive. However, as the chemical source term of the computational fluid dynamics simulation of combustors, there remains a disagreement in understanding the chemical kinetic mechanism of ethanol. The reaction mechanism of ethanol + HÈ®2 is a well-known crucial reaction class in terms of predicting the reactivity of ethanol as well as ethylene formation under engine-relevant conditions. However, the kinetic parameters of the reactions are basically extrapolated by analogy to the n-butanol + HÈ®2 system calculated by Zhou et al. (Zhou et al. Int. J. Chem. Kinet. 2012, 44 (3), 155-164). The reliability of such an analogy remains to be seen because no direct theoretical or experimental evidence is available in the literature to date. In this study, thermal rate coefficients of H-atom abstraction reactions for the ethanol + HÈ®2 system were determined by using both conventional transition-state theory and canonical variational transition-state theory, with the potential energy surface evaluated at the CCSD(T)/cc-pVTZ//M06-2x/def-TZVP level. The quantum-mechanical effects were corrected by the zero-curvature tunneling method at low temperatures (<750 K), and difference schemes of two Eckart functions were fitted to optimize the minimum energy path curves. Torsional modes of the -CH3 and -OH groups were treated by using the hindered-internal-rotation approximation. Furthermore, the rate coefficients of the title reaction were calculated at both the CCSD(T)/cc-pVTZ//M06-2x/def-TZVP and CCSD(T)/CBS//M06-2x/def-TZVP levels of theory with uncertainty of a factor of 3. Similar to the n-butanol + HÈ®2 system, the title system is dominated by α-site H-atom abstraction, but the rate coefficients of the three channels are slightly slower than that of the n-butanol + HÈ®2 system. In general, the new calculations show only a limited effect on the ethanol reactivity at low pressures and high temperatures (>1300 K), but they prevent the kinetic mechanisms from overpredicting ignition delay times under engine-relevant conditions.

One-pot preparation of MnO x impregnated cotton fibers for methylene blue dye removal.

Using natural cotton fibers (CF) as a matrix, a series of novel MnO x impregnated cotton fibers (designated as Mn-X@BCF) were prepared in this study through a one-pot sono-assisted KMnO4 reduction process with no additional reducers. The as-prepared Mn-X@BCF was covered by a uniform and dense layer of MnO x nanospheres (10-30 nm), the amount of which was significantly improved by CF pretreatment and linearly correlated with KMnO4 concentration. Specifically, when KMnO4 concentrations increased from 5 mmol L-1 to 100 mmol L-1, the impregnation ratios of MnO x on BCF increased from 0.34% to 14.98% accordingly. Mn-X@BCF showed substantial removal for the typical dye MB. Under the studied conditions, MB removal equilibrium was reached within 10 minutes and solution pH showed no significant influence over a wide pH range (2-11). MB adsorption by Mn-25@BCF obeyed the pseudo-second-order kinetic model and Langmuir model well. The calculated maximum adsorption capacity (Q m) of Mn-25@BCF was 46.3 mg g-1, close to the cumulative adsorption capacity (Q c 45 mg g-1) of MB determined during the eight cycles of adsorption. It was proposed that adsorption followed by partial oxidation was the main mechanism of MB removal by Mn-X@BCF. The as-prepared Mn-25@BCF has great potential as an efficient and low-cost material for dye wastewater treatment because of its inexpensive and renewable source of raw materials, fast MB removal kinetics, wide working pH range and easy solid-liquid separation.

Adsorption of mercury(ii) from water by a novel sPAN fiber containing sulfhydryl, carboxyl and amino groups.

A novel fiber containing sulfhydryl, carboxyl and amino groups (sPAN) with high adsorption capacity for mercury was facilely prepared by chemically grafting cysteine onto a commercial polyacrylonitrile (PAN) fiber in a one-step reaction. The as-prepared sPAN was characterized for its chemical structure, thermal stability, tensile strength, surface morphology and surface binding species. The adsorption and desorption performances for mercury were investigated by both batch and dynamic experiments. The results showed that sPAN was effective for mercury removal over pH 4-7, and ionic strength produced no obvious interference with the adsorption. The equilibrium adsorption capacity of mercury could be as high as 459.3 (±16.0) mg g-1, much higher than for most previously reported materials due to the strong interaction between mercury ions and sulfhydryl, carboxyl, amino groups. More than 99% adsorbed mercury could be eluted by the mixture of hydrochloric acid and thiourea, and the regenerated sPAN could be reused for mercury removal with no significant loss of adsorption capacity even after 10 cycles. The dynamic adsorption results indicated that at initial mercury concentrations of 0.1 and 1.0 mg L-1, the residual mercury concentration was less than 1 µg L-1, which could meet the criterion for drinking water. Moreover, at an initial mercury concentration of 10 mg L-1, the residual mercury concentration was less than 50 µg L-1, which could satisfy the Chinese national industry water discharge standard.

Kinetics of Hydrogen Abstraction and Addition Reactions of 3-Hexene by ȮH Radicals.

Rate coefficients of H atom abstraction and H atom addition reactions of 3-hexene by the hydroxyl radicals were determined using both conventional transition-state theory and canonical variational transition-state theory, with the potential energy surface (PES) evaluated at the CCSD(T)/CBS//BHandHLYP/6-311G(d,p) level and quantum mechanical effect corrected by the compounded methods including one-dimensional Wigner method, multidimensional zero-curvature tunneling method, and small-curvature tunneling method. Results reveal that accounting for approximate 70% of the overall H atom abstractions occur in the allylic site via both direct and indirect channels. The indirect channel containing two van der Waals prereactive complexes exhibits two times larger rate coefficient relative to the direct one. The OH addition reaction also contains two van der Waals complexes, and its submerged barrier results in a negative temperature coefficient behavior at low temperatures. In contrast, The OH addition pathway dominates only at temperatures below 450 K whereas the H atom abstraction reactions dominate overwhelmingly at temperature over 1000 K. All of the rate coefficients calculated with an uncertainty of a factor of 5 were fitted in a quasi-Arrhenius formula. Analyses on the PES, minimum reaction path and activation free Gibbs energy were also performed in this study.

High-temporal-resolution, full-field optical angiography based on short-time modulation depth for vascular occlusion tests.

We developed high-temporal-resolution, full-field optical angiography for use in vascular occlusion tests (VOTs). In the proposed method, undersampled signals are acquired by a high-speed digital camera that separates the dynamic and static speckle signals. The two types of speckle signal are used to calculate the short-time modulation depth (STMD) of each of the camera pixels. STMD is then used to realize high-temporal-resolution, full-field optical angiography. Phantom and biological experiments conducted and demonstrated the feasibility of using our proposed method to perform VOTs and to study the reaction kinetics in microfluidic systems.

Quantitative measurement of phase variation amplitude of ultrasonic diffraction grating based on diffraction spectral analysis.

A new method based on diffraction spectral analysis is proposed for the quantitative measurement of the phase variation amplitude of an ultrasonic diffraction grating. For a traveling wave, the phase variation amplitude of the grating depends on the intensity of the zeroth- and first-order diffraction waves. By contrast, for a standing wave, this amplitude depends on the intensity of the zeroth-, first-, and second-order diffraction waves. The proposed method is verified experimentally. The measured phase variation amplitude ranges from 0 to 2π, with a relative error of approximately 5%. A nearly linear relation exists between the phase variation amplitude and driving voltage. Our proposed method can also be applied to ordinary sinusoidal phase grating.