No abstract

No abstract

No abstract

Ultrafine silver (Ag) nanoparticles (NPs) were successfully loaded on a robust aluminum (Al) metal–organic framework (MOF), NOTT-300­(Al), by means of a double-solvent method (DSM), and the construction of Ag@NOTT-300­(Al) composites led to a highly efficient catalytic reduction of nitrophenols in these hybrid systems. Of note, the catalytic activity of Ag@NOTT-300­(Al) was used as a heterogeneous catalyst for the reduction of 4-nitrophenol (4-NP) with a reaction rate constant (k) of 2.67 min–1 and activation energy (E a) of ca. 29.7 kJ mol–1. Kinetics and thermodynamics of catalytic 4-NP reduction in this current system complied with the Langmuir–Hinshelwood mechanism. Moreover, the combined use of ultrafine Ag0 NPs and porous NOTT-300­(Al) supports favored reactants diffusion while accelerating the reduction of 4-NP.

The development of viable absorbents for highly efficient and selective removal of lead (Pb) ions, which might exist in various waste discharges related to human activities, is considered a long-standing challenge. Current scientific interests reside in achieving material absorbents with high porosity and desired functionality that respectively relate to generally higher Pb­(II) uptake and selectivity. In this work, two-dimensional conjugated microporous polymers (CMP-2 and CMP-3) were rationally designed in which the heterogeneous (large and narrow) pores of these materials were chemically functionalized with cyano and pyridyl groups, respectively. As expected, the activated CMP-2a and CMP-3a displayed a high Pb­(II) adsorption capacity of 62.7 and 93.2 mg g–1, respectively. Of note is that the CMP-3a could selectively uptake Pb­(II) (84%) over Cu­(II) (40%) and Ni­(II) (18.6%) in simulated wastewater. It was demonstrated that the formation of functionalized and heterogeneous pore structures in CMP-3a accounted for its highly efficient and selective adsorption property toward Pb2+. In addition, CMP-2a and CMP-3a could be easily recovered and regenerated for Pb2+ removal from aqueous solutions and exhibited nondetectable cytotoxicity, which were favorable for their applications as viable and safe absorbents for Pb­(II) removal in aqueous phases.

To evaluate the effect of low-temperature stress in winter wheat during the early growth stages, the response regularity of the canopy spectral reflectance was evaluated. Besides, winter wheat yield during the maturation stage and the relationship between yield and canopy spectral reflectance were also analyzed. Two multivariate methods, namely, the successive projections algorithm (SPA) and multiple linear regression (MLR), were combined to explore the relationship between the spectral reflectance and yield. Our results showed that the green peak and red valley in visible wavelengths altered obviously and the red edge gradually moved towards blue wavebands. The canopy spectral reflectance in the near-infrared wavebands increased with an increase in low-temperature stress intensity. Moreover, the reflectance proved that the red edge region under low-temperature stress is related to winter wheat yield, and approximately 38% of extracted wavebands were concentrated in the red edge region (680-780 nm). Compared with the predictive MLR models, the model calibrated during the flowering period of winter wheat (25 days post low-temperature treatment) had better performance in predicting crop yield. Whole-spectrum predictive models based on the principle component regression (PCR) method and Normalized Difference Vegetation Index (NDVI) models based on MLR were also established. Moreover, the performance of three kinds of calibration methods and the validation result of the field test were compared to select the optimal monitoring stage and technique to estimate the yield in the early growth stage of winter wheat under low-temperature stress. This study could provide a theoretical basis and practical reference for hyperspectral assessment of yield in winter wheat during low-temperature stress.

As a major province of mineral resources in China, Shanxi currently has 6000 mines of various types, and acid mine drainage (AMD) is a major pollutant from the mining industry. Calcareous soil is dominant in western North China (including the Shanxi Province), therefore, clarifying the migration behavior of the main AMD pollutants (H+, S, Fe, heavy metals) in calcareous soil is essential for remediating AMD-contaminated soil in North China. In this study, the migration behavior of the main pollutants from AMD in calcareous soil was investigated using soil columns containing 20 cm of surficial soil to which different volumes of simulated AMD were added in 20 applications. Filtrate that was discharged from the soil columns and the soil samples from the columns were analyzed. Almost all of the Fe ions (>99%) from the AMD were intercepted in the 0–20 cm depth of the soil. Although >80% of SO42− was retained, the retention efficiency of the soil for SO42− was lower than it was for Fe. Cu, as a representative of heavy metals that are contained in AMD, was nearly totally retained by the calcareous soil. However, Cu had a tendency to migrate downward with the gradual acidification of the upper soil. In addition, CaCO3 was transformed into CaSO4 in AMD-contaminated soil. The outcomes of this study are valuable for understanding the pollution of calcareous soil by AMD and can provide key parameters for remediating AMD-contaminated soil.

No abstract