Sequential extraction of labile and recalcitrant fractions of soil organic matter: A case study focusing on antimony (Sb) in humic acids, fulvic acids and humin fractions of long-term aged contaminated soils.

Soil organic matter (SOM) plays a key role in environmental chemistry of macro and micro nutrients as well as heavy metal (loids). In this research, a modified sequential extraction scheme was used to isolate labile and recalcitrant SOM from organic rich soils after 18 months of ageing with antimony. Humic substances were extracted with a mixture of 0.

Universal Langmuir and Fractal Analysis of High-Resolution Adsorption Isotherms of Argon and Nitrogen on Macroporous Silica.

High-resolution isotherms of argon and nitrogen adsorption on macroporous silica have been simulated with universal Langmuir and fractal models. A four-parameter, fractal universal Langmuir equation is a good fit to the data at low pressures. Standard Gibbs energy changes calculated from equilibrium adsorption coefficients show a series of broad peaks that indicate adsorbate structural transformations as a function of pressure and coverage.

The influence of different antimony (Sb) compounds and ageing on bioavailability and fractionation of antimony in two dissimilar soils.

Assessing the bioavailability of various Sb substances plays a crucial role in human health and the ecological risk assessment of contaminated soils. However, fate, behaviour and bioavailability of different Sb compounds in soils are insufficiently known. Therefore, in this present study, the effects of soil properties and ageing on bioavailability of four different Sb compounds (CHKOSb, SbS, SbO and SbO nanoparticles) were evaluated during 120 days ageing time.

Pressure-varying Langmuir parameters and stepped nitrogen adsorption on alumina and silica.

Insights into surface structures and thermodynamics are provided for nitrogen adsorption on two nonporous alumina adsorbents and two macroporous silica adsorbents by modelling high-resolution data using the simple Langmuir isotherm equation combined with pressure-varying flexible least squares. The fitted parameters, maximum adsorption capacity and standard Gibbs energy change for each adsorbent show multiple steps that are assumed to be indicative of transitions to different complete monolayer and multilayer structures. Pressure-varying N2 cross-sectional areas for three of the adsorbents are calculated by assuming that one of the steps is the Brunauer-Emmett-Teller monolayer with molecular area 16.

Charge density analysis of two polymorphs of antimony(III) oxide.

High-resolution X-ray diffraction data have been collected on the cubic polymorph of antimony(III) oxide (senarmontite) to determine the charge distribution in the crystal. The results are in quantitative agreement with crystal Hartree-Fock calculations for this polymorph, and have been compared with theoretical calculations on the orthorhombic polymorph (valentinite). Information about the nature of bonding and relative bond strengths in the two polymorphs has been extracted in a straightforward manner via topological analysis of the electron density.