Dependence of displacement of Ca, Md, Fe, K ions from soils from the duration of exposure to H2O and temperature

In the conducted studies on sod-podzolic soils and ordinary chernozems, a change in the rate of transition of Ca, Md, Fe, K ions from the soil to H2O at temperatures of 0 and 20º, the interaction time of 1 day and 1 week was established. It is shown that the speed of the processes depends on the combination of temperature and duration of reactions, differs for individual soils, horizons and certain cations. The magnitude of the change in the rate of the processes under consideration does not fully correlate with the physico-chemical and thermodynamic patterns of changes in the mobility of ions in soils depending on humidity and temperature, which is associated with the simultaneous course of ion exchange reactions, complex formation, sedimentation. The necessity of studying the kinetics of processes occurring in the soil for a more correct assessment of the agroecological state of soils is proved. Keywords: KINETICS, SOIL, TEMPERATURE INFLUENCE, ION DESORPTION

Unexpectedly efficient ion desorption of graphene–based materials

Ion desorption is extensive and extremely challenging for adsorbents with superior performance, for which conventional desorption methods involving high acid or base concentrations and large consumption of reagents are widely used. Here we experimentally demonstrated the unexpectedly rapid and efficient desorption of ions on magnetite–graphene oxide (M–GO) by adding trace amounts of Al3+. The corresponding concentration of Al3+ used was reduced by a factor of at least 250 compared with the conventional desorption method. The desorption rate reached up to ~ 97.0% for the typical radioactive and bivalent ions of Co2+, Mn2+, and Sr2+ within ~ 1 min. Importantly, we achieved the effective enrichment of radioactive 60Co, with the volume of the concentrated 60Co solution reduced by approximately 10 times compared with the initial solution. Density functional theory calculations revealed that the interaction of graphene with Al3+ was much stronger than that with divalent ions, yielding the adsorption probability of Al3+ superior to Co2+, Mn2+, and Sr2+ ions, suggesting that the proposed method could be used to enrich a wider range of ions in the fields of energy, biology, environment, and materials science.

Switching of alternative electrochemical charging mechanism inside single-walled carbon nanotubes: a quartz crystal microbalance study

The increase in charge carrier density in SWCNTs with applied potential overcomes steric hindrance to counter-ion adsorption by switching the dominant charge storage mechanism to co-ion desorption.

Comparison of Oxalate, Citrate and Tartrate Ions Adsorption in the Hydroxyapatite/Aqueous Electrolyte Solution System

The kinetics of adsorption/desorption of oxalate, citrate and tartrate anions was investigated using hydroxyapatite from solutions at the initial concentrations of 0.000001 and 0.001 mol/dm3 anions. The adsorption process from a solution with a concentration of 0.001 mol/dm3 takes place in three stages and is well described by the multiexponential equation of adsorption kinetics. The process of tartrate and citrate ion desorption after increasing the pH to 10 is irreversible, while the oxalate ions undergo significant desorption with the increasing pH. The adsorption of oxalate ions decreases with the increasing pH. This effect is weaker in the adsorption of citrate and tartrate ions. Ion adsorption studies were supplemented with the measurements of zeta potential, FTIR and particle distribution of hydroxyapatite particles.

Low-temperature chemistry induced by cosmic rays: positive and negative ion desorption from nitrile-bearing astrophysical ice analogues

ABSTRACT In cold core of dark molecular clouds, where the UV radiation from external sources is strongly attenuated, cosmic rays can induce chemical reactions on the surface of ice-covered grains promoting the ejection of the processed material to the gas phase. We report the positive and negative secondary ion emission from pure CH3CN, C2H3CN, and i-C3H7CN ices due to the bombardment of heavy ions (252Cf fission fragments), simulating the incidence of cosmic rays on to icy surfaces. The secondary ions emitted from each sample were analysed by time-of-flight mass spectrometry, using Plasma Desorption Mass Spectrometry technique. Several ionic species were identified, indicating strong fragmentation on the frozen surface. Proton-transfer processes are suggested to play a role for positive ion desorption, as evidenced by the protonated RCNH+ parent molecules and (RCN)nH+ ionic clusters. The high electron affinity of the cyano radical seems to contribute to the strong emission of CN−, as well as anions attributed to the CHmCN− fragment and (RCN)nCN− cluster series. Sputtering and desorption of ion clusters (positive and negative) induced by heavy ion bombardment are suggested to constitute a route by which new neutral or ionized molecular species may be delivered to the gas phase where thermal desorption is negligible.