Search

Abstract Volatile organic compounds (VOCs) are important precursors in the formation of ground-level ozone. In this study, the hourly mixing ratios of 61 ambient VOC species were monitored from 2018 till 2019 in 10 cities in the Beijing-Tianjin-Hebei (BTH) area of China, and the VOC distributions, speciation and photochemistry were also examined. The highest mixing ratios were found in the south, viz., Langfang (LF), Baoding (BD), Handan (HD) and Shijiazhuang (SJZ), and the lowest ones, in the north, viz., Chengde (CD) and Zhangjiakou (ZJK). In all of the cities, alkanes were the most abundant VOC component (50%), whereas ethane and propane were the most concentrated species. The mixing ratios of the VOCs exhibited a daily double peak as a result of the varying intensity of the photochemical reactions and the formation of the inversion layer. Additionally, the chemical reactivity of the VOCs was evaluated by calculating the loss rate of OH (LOH) for each species. Our results indicated that the alkenes and aromatics possessed higher LOH values as well as higher ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAp) values than the alkanes. Based on the diagnostic ratios of propane/n-butane, propane/i-butane, cis-2-butane/trans-2-butane, toluene/benzene and xylene/ethylbenzene, motor vehicle emissions contributed significantly to the ambient VOCs in the area.

Cephalosporin enzymatic hydrolysis technology is a green technology for recovering 7-amino-3-deacetoxycephalosporanic acid (7-ADCA) from cephalosporin mother liquor. Solubility is critical for the production and purification of 7-ADCA. In this paper, the solubility of 7-ADCA and phenylglycine was measured. Solubility-temperature correlation model and solubility-pH correlation model were investigated, and Akaike information criterion (AIC) analysis was performed. The kinetic parameters of the enzymatic hydrolysis reaction of cephalexin, cefradine, and cefadroxil were determined, and the reaction rates under different substrate concentrations were measured, and the Lineweaver–Burk double-reciprocal equation was used to draw a graph. The Michaelis constants Km/(mg/mL) were 73.98, 583.84, 38.66, Vmax/(mg/mL·min) 4.20, 16.00, 1.96, respectively. The experimental results show that amphoteric compounds and buffers can prompt the reaction, low concentration of methanol promotes the reaction, while high concentration of methanol inhibits the reaction, and ethanol, isopropanol, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), ethylene glycol (EG), 1,4-dioxane all have different degrees of inhibition on the reaction speed. Finally, based on thermodynamic and kinetic studies, a process technology for the preparation of 7-ADCA by hydrolysis catalyzed of cephalexin was developed. It was confirmed that the proposed process route of preferential removal of phenylglycine by elution and/or cooling crystallization was reasonable and effective. The 7-ADCA crystal products obtained by crystallization were characterized by PXRD, thermal analysis, infrared, electron microscope, and high-performance liquid chromatography (HPLC).

Herein, a non-stacked γ-Fe2O3/C@TiO2 double-layer hollow nano photocatalyst has been developed with ultrathin nanosheets-assembled double shells for photodegradation phenol. High catalytic performance was found that the phenol could be completely degraded in 135 min under visible light, due to the moderate band edge position (VB at 0.59 eV and CB at −0.66 eV) of the non-stacked γ-Fe2O3/C@TiO2, which can expand the excitation wavelength range into the visible light region and produce a high concentration of free radicals (such as ·OH, ·O2−, holes). Furthermore, the interior of the hollow composite γ-Fe2O3 is responsible for charge generation, and the carbon matrix facilitates charge transfer to the external TiO2 shell. This overlap improved the selection/utilization efficiency, while the unique non-stacked double-layered structure inhibited initial charge recombination over the photocatalysts. This work provides new approaches for photocatalytic applications with γ-Fe2O3/C-based materials.

7-Aminocephalosporanic acid wastewater usually contains high concentrations of ammonium (NH4+-N), which is known to inhibit nitrification during biological treatment processes. Chemical precipitation is a useful technology to remove ammonium from wastewater. In this paper, the removal of ammonium from 7-aminocephalosporanic acid wastewater was studied. The optimum pH, molar ratio, and various chemical compositions of magnesium ammonium phosphate (MAP) precipitation were investigated. The results indicated that ammonium in 7-aminocephalosporanic acid wastewater could be removed at an optimum pH of 9. The Mg2+:NH4+-N:PO43−-P molar ratio was readily controlled at a ratio of 1:1:1.1 to both effectively remove ammonium and avoid creating a higher concentration of PO43−-P in the effluent. MgCl2·6H2O + 85% H3PO4 was the most efficient combination for NH4+-N removal. Furthermore, the lowest concentration of the residual PO43−-P was obtained with the same combination. Struvite precipitation could be considered an effective technology for the NH4+-N removal from the 7-aminocephalosporanic acid wastewater.

In this work, an N-butyl-pyridinium-based ionic liquid [BPy]BF4 was prepared. The effect of extraction desulfurization on model oil with thiophene and dibenzothiophene (DBT) was investigated. Ionic liquids and hydrogen peroxide (30%) were tested in extraction-oxidation desulfurization of model oil. The results show that the ionic liquid [BPy]BF4 has a better desulfurization effect. The best technological conditions are: V(IL)/V(Oil) /V(H2O2) = 1:1:0.4, temperature 55 °C, the time 30 min. The ratio of desulfurization to thiophene and DBT reached 78.5% and 84.3% respectively, which is much higher than extraction desulfurization with simple ionic liquids. Under these conditions, the effect of desulfurization on gasoline was also investigated. The used ionic liquids can be recycled up to four times after regeneration.

In the title compound, C14H19I, the cyclohexane ring adopts a chair conformation and the substituents are in equatorial sites. The dihedral angle between the mean planes of the cyclohexane and benzene rings is 67.23 (13)°.

Optimizing the photocatalytic efficiency of semiconductor materials is capable of being achievable by the effective tuning of the interfacial transport efficiency of photogenerated carriers utilizing crystal facet engineering. This study adopted a liquid deposition routine tackle to generate cubic, truncated octahedral, and octahedral Cu2O crystals with various exposed facets. Afterward, a Cu2O/g-C3N4 heterojunction was constructed exploiting defective g-C3N4 as a carrier. By controlling the exposed facet, the work function difference between Cu2O and g-C3N4 was adjusted, resulting in an enhanced built-in electric field and greater photogenerated carrier transit via the Cu2O/g-C3N4 heterojunction interface. The OCN heterojunction, which is composed of g-C3N4 and octahedral Cu2O with a {111} facet, revealed the highest photocatalytic degradation effectiveness of tetracycline (90.8%), which exceeded the values of pure octahedral Cu2O and g-C3N4 by 1.26 and 1.75 times, respectively, as determined by photocatalytic activity experiments. Z-scheme heterojunction among g-C3N4 and octahedral Cu2O has been verified through UPS, XPS, EIS, and transient photocurrent response analysis, along the direction of the built-in electric field recognized between them. In contrast, OCN displayed the highest photocatalytic activity due to its Z-scheme heterojunction, which evidently promoted the separation efficiency of photogenerated carriers. This research proposes an innovative approach for regulating the exposed facet of semiconductors and augmenting the inherent electric field strength of heterojunctions, culminating in the efficient photocatalytic degradation of tetracycline. [ABSTRACT FROM AUTHOR]

To reduce the emission of nitrogen oxides (NOx) during the co-disposal of sludge in a TTF-type precalciner, an optimized co-disposal process of a TTF-type precalciner has been implemented in a cement plant in Hebei. The model was built using ANSYS FLUENT software. The effects of three singlefactor perspectives (sludge input ratio, gas flow rate, and tertiary air temperature on NO concentration) were investigated. The response surface method of Box-Behnken design was used. When the sludge ratio increased from 0 to 25%, the NO concentration at the outlet was 122-297 mg/m2. Meanwhile, it increased from 192 mg/m2 to 241 mg/m2 since the airflow increased from 95 m2/s to 122 m2/s. The maximum NO concentration was 192 mg/m2 when the tertiary air temperature was 1170 K. The interaction between airflow and sludge ratio was more significant than any other interaction between other conditions (P < 0.05). Finally, the optimum conditions were a sludge ratio of 5%, airflow 109 m2/s, and tertiary air temperature 1280 K. NO concentration was 166.9 mg/m2 under this condition. [ABSTRACT FROM AUTHOR]

The dissolution of cellulose is an important pretreatment method required for some of its catalytic conversion processes. Morpholinium-based ionic liquids (ILs) are challenging solvent choices available for "greener" and "cheaper" dissolution of cellulose. In this study, morpholinium-based ILs were prepared, and their influencing factors were experimentally investigated. The unique bipolar chemical structure derived from oxygen (electron-rich center) and nitrogen (electron-poor center) considerably enhanced the Hammett acidity function (H0) of task-ILs. N-Methyl-N-allylmorpholinium acetate IL showed the highest H0 (2.324) and polarizability power (1.096). The anion of ILs determined the hydrogen bond basicity (β). The acetate anion contributed to β (0.88) values. As to fluid properties, the morpholinium-based ILs exhibited much lower viscosity. The properties of ILs improved the dissolution efficiency. The cellulose was directly dissolved in morpholinium-based Ils, and no other derivatives were formed. The cations and the anions of ILs studied reacted with oxygen and hydrogen atoms on the hydroxyl groups of cellulose, respectively. [ABSTRACT FROM AUTHOR]

The solubility of (2S)-pyrrolidine-2-carboxylic acid in pure alcohols (methanol, ethanol, isopropyl alcohol, and butan-1-ol) and the aqueous alcohols (methanol, ethanol, and isopropyl alcohol) mixtures was measured by a dynamic method via a laser monitoring technique. The solubility in the pure alcohols follows the order methanol > ethanol > butan-1-ol > isopropyl alcohol. In the binary mixtures, the solubility decreases with the increase of alcohol concentration. The experimental solubility was fitted by the modified Apelblat equation, combined nearly ideal binary solvent/Redlich-Kister (CNIBS/R-K) model, and Van't Hoff equation. The dissolution is endothermic and the dissolution driving force converts from enthalpy-driven to entropy-driven. [ABSTRACT FROM AUTHOR]

The agglomeration of crystallized 1,4-diazabicyclo(2.2.2)octane was investigated in a turbulent agitated semibatch reactor. To modify the agglomeration of 1,4-diazabicyclo(2.2.2)octane, the crystallization operating factors, including the stirring rate, cooling rate, feed concentration, and aging, were studied. The mean particle size of the 1,4-diazabicyclo(2.2.2)octane in the product suspension increased with decreasing feed concentration and cooling rate. The products were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The product obtained at the condition of crystalline concentration of 1.80 g/mL, stirring rate of 200 rpm, and cooling rate of 0.3 K/min is hard to agglomerate. [ABSTRACT FROM PUBLISHER]

7-Aminocephalosporanic acid wastewater usually contains high concentrations of ammonium (NH4 +-N), which is known to inhibit nitrification during biological treatment processes. Chemical precipitation is a useful technology to remove ammonium from wastewater. In this paper, the removal of ammonium from 7-aminocephalosporanic acid wastewater was studied. The optimum pH, molar ratio, and various chemical compositions of magnesium ammonium phosphate (MAP) precipitation were investigated. The results indicated that ammonium in 7-aminocephalosporanic acid wastewater could be removed at an optimum pH of 9. The Mg2+:NH4+-N:PO43--P molar ratio was readily controlled at a ratio of 1:1:1.1 to both effectively remove ammonium and avoid creating a higher concentration of PO43--P in the effluent. MgCl2·6H2O + 85% H3PO4 was the most efficient combination for NH4+-N removal. Furthermore, the lowest concentration of the residual PO43--P was obtained with the same combination. Struvite precipitation could be considered an effective technology for the NH4+-N removal from the 7-aminocephalosporanic acid wastewater. [ABSTRACT FROM AUTHOR]

To explore environmentally benign solvents for the absorption of NO and NO2, a series of caprolactam tetrabutyl ammonium halide ionic liquids were synthesized. The solubility of NO and NO2 was measured at temperatures ranging from 298.2 to 363.2 K and atmospheric pressure, and the following trend in the solubility of NO and NO2 in ionic liquids with various halide anions was observed, respectively: F > Br > Cl and Br > Cl > F. Moreover, as the temperature increased from 308.15 to 363.15 K and the mole ratio of caprolactam increased from 2:1 to 6:1, the solubility of NO increased. Alternatively, the solubility of NO2 decreased as the temperature increased from 298.15 to 363.15 K, and the mole ratio of caprolactamincreased from 2:1 to 6:1. The absorption and desorption of NO and NO2 was practically reversible in the ionic liquids, which was characterized by nuclear magnetic resonance. The method, which is at least partially reversible, offers interesting possibilities for the removal of NO and NO2. [ABSTRACT FROM AUTHOR]

Trans-4-propyl-cyclohexylcarboxylic acid (Trans-4-PA) was synthesized. 1H, 13C, and some 2D nuclear magnetic resonance (NMR) spectra were recorded and signals were assigned. Density functional theory (DFT) calculation was carried out to simulate the optimized trans- and cis-configuration of 4-PA. Both configurations were stable and in minimal energy states. The dihedral angles of Hα-C-C-Hβ with respect to carboxylic carbon were measured in both of the two configurations. The Karplus equation was used to speculate on 3J value of Hα-Hβ in both configurations. The experimental result was compatible with computed figures of trans-configuration. The Fourier transform infrared (FTIR) spectra were also measured and peaks were assigned. [ABSTRACT FROM AUTHOR]

The solubilities of triethylenediamine in methanol, ethanol, isopropanol, 1-butanol, and ethyl acetate between 276.15 K and 363.15 K were measured using a synthetic method at atmospheric pressure. A laser monitoring observation technique was used to determine the disappearance of the solid phase in a solid liquid mixture. The solubility of triethylenediamine in the above solvents increased in the order methanol > ethanol > isopropanol > 1-butanol > ethyl acetate. An empirical equation was proposed and verified by experimental solubility data. [ABSTRACT FROM AUTHOR]