Effect of Nitric Oxide Treatment on Storage Quality of Glorious Oranges

AbstractEffect of nitric oxide (NO) treatment on storage quality and disease resistance of Glorious oranges was investigated in the experiment. The results showed that NO treatment could effectively reduce disease incidence inoculated with Collletotichum goeosporioides Penz and inhibit the increase of lesion diameter of Glorious oranges during storage. Compared with the control, NO treatment kept higher level of titritable acidity (TA), soluble protein, ascorbic acid (ASA) and reducing sugar, and lower level of weight lose rate and soluble solid concentration (SSC), retarding ripening of fruits

Alkanolamines-activated steel slag for stabilization/solidification of heavy metal contaminated soil

Steel slag (SS) is a byproduct discharged from steel-making industry with less than 25% utilization rate in China. The low utilisation rate of SS is associated with its low hydration activity in cement and concrete. In this study, four different alkanolamines (TEA, TIPA, EDIPA and DEIPA) were used to activate SS to improve its cementitious properties and metal binding performance, and hence its capacity on treating heavy metal-contaminated soils containing Cd, Cu, Ni, Pb and Zn. Compared with the reference SS without activators, concentrations of leached Cd, Cu, Ni, Pb, and Zn have reduced by 87.2%, 78.8%, 62.4%, 73.6% and 64.5% by using 0.1% TIPA-activated SS after 28 days, and they were all below their respective regulatory limits by Standard for Pollution Control on the Hazardous Waste Landfill (GB 18598–2019) in China, and the unconfined compressive strength (UCS) of the treated soil at 28 days was enhanced by 237.7% using 0.1% TIPA-activated SS. To elucidate the activation mechanism, the hydration process of SS was thoroughly followed via isothermal calorimetry (IC) and conductivity analysis, and the nature of hydration products was studied by X-ray diffraction (XRD) and thermogravimetric analysis (TGA). It was concluded that alkanolamines facilitated the dissolution of minerals in SS and formation of hydration products (e.g., C-S-H, C-A-H, C-F-H and Mc), and hence significantly enhanced the microstructural development and engineering properties of SS. This work demonstrated a promising way of upcycling SS as an effective and sustainable S/S agent for handling complex heavy metal contaminated soil, with the potential of enhancing the SS utilization significantly

Synthesis of Mg-Al LDH and its calcined form with natural materials for efficient Cr(VI) removal

Layered double hydroxide (LDH) has been extensively studied due to its excellent capacity of heavy metal adsorption. However, the synthesis of LDH is always complex and requiring pure chemical reagents. In this study, two solid minerals, MgO and metakaolin (MK), derived from abundant natural resources, were used as raw materials to synthesize Mg-Al LDH via a facile one-pot method. The compositions and morphologies of synthetic products and its calcined form(C-LDH) were characterized by X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Cr(VI) adsorption by the LDH and C-LDH was systematically studied including the effect of contact time, initial pH value, temperature, liquid/solid ratio, and initial Cr(VI) concentration. The adsorption kinetics and isotherms were modelled, and thermodynamic parameters were determined. Results showed that the LDH and C-LDH exhibited high adsorption capacities (23.5–33.2 mg/g and 33.2–38.9 mg/g, respectively) within a wide pH range of 1.75–6.0, and maintained a higher adsorption capacity in all cases afterwards. The pseudo-second-order kinetic model fitted the kinetic data well in which the Langmuir model described the adsorption isotherms the best. The adsorption process was endothermic and spontaneous. The adsorption mechanisms may include anion exchange, redox reaction, and electrostatic adsorption. Moreover, the effect of the synthesis conditions (i.e., alkali concentration, temperature and liquid/solid ratio) on the adsorption characteristics were discussed. And XPS, UV-Vis Spectrophotometer (UV-Vis) and FTIR analysis confirmed Cr(VI) adsorption on the LDH and C-LDH surface, followed by its subsequent reduction to Cr(III). It has been revealed that the LDH/C-LDH synthesized in this work exhibited higher Cr(VI) removal capacities compared to the ones reported in the literature, demonstrating the significant potential of synthesizing high performance absorbents by low-cost natural materials

One-pot synthesis of Mg-Al layered double hydroxide (LDH) using MgO and Metakaolin (MK) as precursors

Layered double hydroxides (LDH) are a class of basic inorganic layered compounds, which are widely used in the fields of adsorption and catalysis owing to their unique structure and properties. In previous studies, costly soluble Al salts or Al(OH)3 were used as the Al sources for the synthesis of Mgsingle bondAl LDH. The present work proposes a facile and one-pot method to synthesize Mgsingle bondAl LDH in a water bath with MgO and MK as precursors, which are both obtained from abundant natural resources. The effects of liquid/solid ratio (30:1 or 60:1), synthesis temperature (55–90 °C) and alkali concentration (3 or 6 mol/L) were investigated on the composition and characteristics of the synthetic products. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), Scanning electron microscope (SEM) and Nuclear magnetic resonance (NMR). Findings showed that a highly alkaline solution (6 M NaOH) promoted the dissolution of MK, resulting in the release of trivalent Al for the formation of LDH. Increasing temperature also led to faster dissolution of MK and released more Al and Si, which resulted in the formation of both LDH and zeolite. More importantly, it was found that Mg2+ released during the hydrolysis of MgO combined with Al-containing substances directly to precipitate LDH, whereas its hydration product, i.e., brucite, remained stable in the alkaline condition and released little Mg2+ to participate in the formation of LDH. Zeolites may form depending on the Si/Al ratio of the solution which is governed by the various synthesis parameters. The findings not only shed lights on the reaction mechanism between the MgO and MK and the role of key synthetic conditions in the formation of LDH and zeolitic phases, but also demonstrated the feasibility of using widely-available, low-cost natural minerals to produce commercial adsorbents/catalysts

Molecular Characterization of Nitrogen-Containing Organic Compounds in Humic-like Substances Emitted from Straw Residue Burning

The molecular composition of humic-like substances (HULIS) in different aerosol samples was analyzed using an ultrahigh-resolution mass spectrometer to investigate the influence of biomass burning on ambient aerosol composition. HULIS in background aerosols were characterized with numerous molecular formulas similar to biogenic secondary organic aerosols. The abundance of nitrogen-containing organic compounds (NOC), including nitrogen-containing bases (N-bases) and nitroaromatics, increased dramatically in ambient aerosols affected by crop residue burning in the farm field. The molecular distribution of N-bases in these samples exhibited similar patterns to those observed in smoke particles freshly emitted from lab-controlled burning of straw residues but were significantly different with those observed from wood burning. Signal intensity of the major N-bases correlated well with the atmospheric concentrations of potassium and levoglucosan. These N-bases can serve as molecular markers distinguishing HULIS from crop residue burning with from wood burning. More nitroaromatics were detected in ambient aerosols affected by straw burning than in fresh smoke aerosols, indicating that many of them are formed in secondary oxidation processes as smoke plumes evolve in the atmosphere. This study highlights the significant contribution of crop residue burning to atmospheric NOC. Further study is warranted to evaluate the roles of NOC on climate and human health