Oblique impact breakage unification of nonspherical particles using discrete element method

Particle breakage commonly occurs during processing of particulate materials, but a mechanistic model of particle impact breakage is not fully established. This article presents oblique impact breakage characteristics of nonspherical particles using discrete element method (DEM) simulations. Three different particle shapes, i.e. spherical, cuboidal and cylindrical, are investigated. Constituent spheres are agglomerated with bridging bonds to model the breakage characteristics under impact conditions. The effect of agglomerate shapes on the breakage pattern, damage ratio, and fragment size distribution is fully investigated. By using a newly proposed oblique impact model, unified breakage master surfaces are theoretically constructed for all the particle shapes under oblique impact conditions. The developed approach can be applied to modelling particulate processes where nonspherical particles and oblique impact breakage are prevailing.</p

The use of 3-(2-pyridyl)-5, 6-diphenyl-1, 2, 4-triazine as precolumn derivatizing reagent in HPLC determination for Fe(II) in natural samples

The 3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PDT) was used for the first time as a precolumn derivatizing reagent applied in the high-performance liquid chromatography (HPLC) method with UV-detection for the Fe (II) determination. The Fe (II) reacts with PDT to form a magenta colored chelate in the presence of sodium dodecyl sulfate (SDS) and acetic acid-sodium acetate buffer solution medium of pH 4.65. The selection of maximum absorbance detect wavelength and the optimum composition of the organic modifier in the mobile phase were investigated in detail for the quantitative determination of Fe (II) using HPLC system. The formed Fe(II)-PDT chelate was satisfactorily separated from PDT on a Agilent Shim-pack ODS column (Eclipse XDB-C8,4.6x150mm) by isocratic elution with acetonitrile and 0.02 mol L-1 acetic acid-sodium acetate buffer solution (pH 4.65, containing 0.02% of SDS and 60x10-3 mol L-1 NaClO4) as mobile phase at a flow rate of 1 mL min-1, and monitored with a multiple wavelength detector. The detection limit (S/N =3) is 0.35 ng ml-1. Due to the excellent separation ability of HPLC, the innovative introduction of PDT as the precolumn derivatizing reagent, and the proper selection of the detect wavelength, the sensitivity of our newly developed HPLC method was enhanced remarkably compared to the common spectrophotometric methods. The developed HPLC method was successfully applied to the determination of Fe(II) in lake water samples

Numerical Study on the Migration of Leaked Oil in Submarine Sediment Caused by Pipeline Leakage Using Two-phase Flow Model

Oil leakage from submarine pipelines can cause severe environmental problems and economic losses. In this study, a two-phase immiscible flow model in porous media is proposed to simulate the migration of leaked oil caused by the leakage of a buried submarine pipeline in sandy sediment. The relationship between saturation, pore pressure, and relative permeability of different fluids in porous media is considered in present model, which is distinguished from previous studies. The spilled oil spreads radially from the leakage point into surrounding sediment driven by the leakage velocity. Moreover, it continues to migrate in sediment under the capillary pressure and gravity. Interestingly, the effect of wave-induced transient response on the ultimate migration of spilled oil in a sandy sediment is negligible. However, increasing sediment porosity can greatly enhance the upward migration of leaked oil based on systematically parametric analysis. Meanwhile, the migration rate of leaked oil decreases with increasing oil density or viscosity. The oil-contaminated area significantly expands with the increase of leakage rate. Fitting formulas between dimensionless time required for the leaked oil to reach the overlying seawater and non-dimensional influencing parameters are well established, which can provide useful guidelines for similar disasters.</p

Global fallout Pu recorded in lacustrine sediments in Lake Hongfeng, SW China

Studies on the distribution and isotope compositions of fallout Pu are important for source characterization of possible future non-fallout Pu contamination in aquatic environments, and useful for dating of recent sediments to understand the pollution history of environmental contaminants. We present the historical record of atmospheric Pu fallout reconstructed from a sediment core from Lake Hongfeng, China. The Pu activity profile was in agreement with the 137Cs profile. Inventories were 50.7 Bq m-2 for 239+240Pu and 1586 Bq m-2 for 137Cs. The average 240Pu/239Pu atom ratio was 0.185 &#61617; 0.009, indicating that Pu originated from global stratospheric fallout rather than from direct tropospheric or close-in fallout from the Chinese nuclear testing conducted in the 1970s. Our data suggested that Lake Hongfeng would be an ideal setting for monitoring atmospheric fallout and environmental changes in this region

Vertical distributions of 239+240Pu activity and 240Pu/239Pu atom ratio in sediment core of Lake Chenghai, SW China

Due to the different 240Pu/239Pu atom ratios from different sources of Pu in the environment, Pu isotopes have been widely used for source identification of radionuclides in sediments. In this work, using sector-field ICP-MS, we investigated Pu inventory and its isotopic composition in a lacustrine sediment core collected in Chenghai Lake, SW China. The 240Pu/239Pu atom ratios in this sediment core ranged from 0.166 to 0.271 with a mean of 0.195 +/-0.021; 0.021, which was slightly higher than that of global fallout. The 239+240Pu/137Cs activity ratios ranged from 0.0155 to 0.0411, with a mean of 0.0215, and the 239+240Pu inventory was 35.4 MBq/km2; both 239+240Pu/137Cs activity ratio and Pu inventory were close to those values of global fallout at 20 - 30 N. Three peaks were observed for both 137Cs and 239+240Pu activities in the examined sediment core; they most probably indicated the maximum deposition of global fallout between 1963 and 1964, the fallout from a series of Chinese nuclear tests during the 1970s, and the deposition of resuspended Pu-bearing particles from the Chernobyl accident. Therefore, the vertical profile of Pu isotopes should provide useful time markers for rapid dating of recent sediments

Ultraviolet absorbance titration for determing stability constants of humic substances with Cu(II) and Hg(II)

We describe an ultraviolet absorbance titration method that can be used to determine complexing capacities and conditional stability constants of humic substances with metal ions such as Cu(II) and Hg(II). Two fulvic acids and one humic acid were used for this study. UV absorbance of HSs gradually increased with the addition of Cu(II) or Hg(II) after blank correction, and these increases followed the theoretical 1:1 (ligand:metal ion) binding model. The results from the absorbance titration calculation for HSs with Cu(II) and Hg(II) compared well with those from fluorescence quenching titration. The titration of the model compound L-tyrosine with Cu(II) proved the validity of this method, and the K and CL were within 2.3 % and 7.4 % of the fluoresence quenching titration. The results suggest that the UV absorbance titration can be used to study the binding capacities of HSs and/or dissolved organic matter with trace metals. The advantages and disadvantages of the absorbance titration method were also discussed