Changes in CO2 Adsorption Affinity Related to Ni Doping in FeS Surfaces: A DFT-D3 Study

Metal sulphides constitute cheap, naturally abundant, and environmentally friendly materials for energy storage applications and chemistry. In particular, iron (II) monosulphide (FeS, mackinawite) is a material of relevance in theories of the origin of life and for heterogenous catalytic applications in the conversion of carbon dioxide (CO2) towards small organic molecules. In natural mackinawite, Fe is often substituted by other metals, however, little is known about how such substitutions alter the chemical activity of the material. Herein, the effect of Ni doping on the structural, electronic, and catalytic properties of FeS surfaces is explored via dispersion-corrected density functional theory simulations. Substitutional Ni dopants, introduced on the Fe site, are readily incorporated into the pristine matrix of FeS, in good agreement with experimental measurements. The CO2 molecule was found to undergo deactivation and partial desorption from the doped surfaces, mainly at the Ni site when compared to undoped FeS surfaces. This behaviour is attributed to the energetically lowered d-band centre position of the doped surface, as a consequence of the increased number of paired electrons originating from the Ni dopant. The reaction and activation energies of CO2 dissociation atop the doped surfaces were found to be increased when compared to pristine surfaces, thus helping to further elucidate the role Ni could have played in the reactivity of FeS. It is expected that Ni doping in other Fe-sulphides may have a similar effect, limiting the catalytic activity of these phases when this dopant is present at their surfaces.

Biochar-Ca and Biochar-Al/-Fe-Mediated Phosphate Exchange Capacity are Main Drivers of the Different Biochar Effects on Plants in Acidic and Alkaline Soils

Because of the low consistency of the results obtained in the field, the use of biochar as a soil amendment is controversial. Thus, in general, in acidic soils, results are positive, while in alkaline soils, they are non-significant or even negative. The results regarding biochar action in acidic soils have been related to a lime-like effect due to its alkaline pH and the high doses normally used. However, the causes of biochar effects in alkaline soils remain unknown. Our objective was to explore the chemical mechanism of biochar interaction in acidic and alkaline soils. We used well-characterized biochar as a component of two complex N and PK granulated fertilizers at two different doses (1% and 5%). These fertilizers were applied to wheat cultivated in pots containing an alkaline soil and grown for 60 days. No effect was shown for the N-biochar fertilizer application. However, the PK-biochar fertilizer application caused a decrease in crop yield. In addition, the adsorption isotherms of Al, Fe, Mo, Mn, and Phosphate (Pi) in biochar were also studied. The results showed that Fe and Al were rapidly adsorbed in biochar, while Pi was only adsorbed on the Fe-, Al-biochar complex. Desorption experiments showed that P and Fe/Al were not desorbed from the P-Fe/Al-biochar complex by water or the Olsen reagent, while partial desorption was observed when HCl 0.1 M was used. This blockage of Fe/Al and P through Fe/Al bridges in biochar could partially explain the negative effects in alkaline soils. After these studies, soil solution sorption experiments were carried out in both acidic and alkaline soils and were complemented with a greenhouse trial using tomato plants. The results showed that biochar enhanced foliar Ca and N content, as well as growth in acidic soil only, and the possible mechanism of the failure in alkaline soils.

The chemical interaction of biochar with iron and phosphate might explain the effects of biochar in alkaline and calcareous soils

<p>Due to the low consistency of the results obtained in field, the use of biochar as soil amendment is controversial. Thus, in general in acidic soils results are positive while in alkaline soils they are non-significant or even negative. The results regarding biochar action in acidic soils have been related to a lime-like effect due to its alkaline pH and the high doses normally used. However, the causes of biochar effects in alkaline soils remain unknown. We have used a well characterized biochar as a component of two complex N and PK granulated fertilizers at two different doses (1 and 5%). These fertilizers have been applied to wheat cultivated in pots containing an alkaline and calcareous soil and grown for 60 days. No effect was shown for the N-biochar fertilizer application. However, the PK-biochar fertilizer application caused a decrease in crop yield. Complementary, the absorption isotherms of Iron (Fe), Molybdenum (Mo), Manganese (Mn) and Phosphate (Pi) in biochar were also studied. The results showed that Fe was rapidly adsorbed in biochar, while Pi was only absorbed on the Fe-Biochar complex. Desorption experiments showed that P and Fe were no desorbed from the P-Fe-biochar complex by water or the Olsen reactant, while a partial desorption was observed when HCl 0.1 M was used. This blockage of Fe and P through Fe bridges in biochar could partially explain the negative effects in alkaline soils.</p>

SORPTION OF Au(III) BY Saccharomyces cerevisiae BIOMASS

Au(III) sorption by S. cerevisiae biomass extracted from beer waste industry was investigated. Experimentally, the sorption was conducted in batch method. This research involved five steps: 1) identification the functional groups present in the S. cerevisiae biomass by infrared spectroscopic technique, 2) determination of optimum pH, 3) determination of the sorption capacity and energy, 4) determination of the sorption type by conducting desorption of sorbed Au(III) using specific eluents having different desorption capacity such as H2O (van der Waals), KNO3 (ion exchange), HNO3 (hydrogen bond), and tiourea (coordination bond), 5) determination of effective eluents in Au(III) desorption by partial desorption of sorbed Au(III) using thiourea, NaCN and KI. The remaining Au(III) concentrations in filtrate were analyzed using Atomic Absorption Spectrophotometer. The results showed that: 1) Functional groups of S. cerevisiae biomass that involved in the sorption processes were hydroxyl (-OH), carboxylate (-COO-) and amine (-NH2), 2) maximum sorption was occurred at pH 4, equal to 98.19% of total sorption, 3) The sorption capacity of biomass was 133.33 mg/g (6.7682E-04 mol/g) and was involved sorption energy 23.03 kJ mol-1, 4) Sorption type was dominated by coordination bond, 5) NaCN was effective eluent to strip Au(III) close to 100%. Keywords: sorption, desorption, S. cerevisiae biomass, Au(III)

Adsorption of Oleate Anions on to Cationized Lignocelluloses

Oleic acid and its salts are present among the toxic pollutants in olive oil mill wastewaters. Four lignocellulosic materials modified by grafting quaternary ammonium groups have been tested for the adsorption of the oleate anion from aqueous solutions, viz. cotton fibres, viscose fabric, wood sawdust and maize cob powder. As a result of their strong ionic interactions, the carboxylate moities were entrapped at a rate equivalent to the ammonium content of the support. Furthermore, when this charged support was left in contact with the polluted solution without agitation, an additional quantity of pollutant was adsorbed due to associations by the hydrophobic tails of the oleate moities. Partial desorption was achieved in 1 M HCl solution.

Transformation In Hydrogenated ZR-CU-NI-AL Quasicrystals

The high number of potential interstitial sites suitable for hydrogen and the favorable hydrogen-metal chemistry make quasicrystalline alloys candidates for hydrogen storage applications. Hydrogen charging was performed electrochemically in a 2:1 glycerin-phosphoric acid electrolyte. The microstructure of quasicrystals in Zr69.5Cu12Ni11Al7.5 was investigated by x-ray diffraction and TEM, the kinetics of transformations by DSC and TDA.Hydrogen was observed to exhibit a significant effect not only on the formation of Zr-based quasicrystalsfrom the glassy precursor material, but also on their stability. Ribbons with an icosahedral microstructure were found to absorb hydrogen up to H/M = 2.0. With increasing hydrogen content an expansion of the quasilattice constant was observed, followed by the formation of approximants and finally amorphization.Only partial desorption of hydrogen can occur prior to the decomposition of the quasicrystalline phase. Desorption at lower temperatures is hindered by the formation of a thin ZrO2 barrier. Pd plating, often used to overcome such a barrier, improves the absorption kinetics as well as the desorption behavior significantly. DSC of uncoated Zr-based quasicrystals reveals that at low hydrogen contents the decomposition ofthe icosahedral quasicrystals is shifted to lower temperatures; at high hydrogen contents the formation of ZrH2-x was revealed. In the Pd-coated ribbons fully desorption is observed even below 300°C, butonly after hydrogenation up to H/M = 0.5; higher hydrogen contents lead to irreversible changes.The micromechanism of transformations during hydrogenation as well as the decomposition during annealing of hydrogenated uncoated as well as Pd coated Zr-based quasicrystals are discussed in some detail.

Na and Cl2 Interaction on it and 2H–TaSe2(0001) Surfaces

In this paper we study the interaction of Cl 2 and Na on 1T– TaSe 2 and 2H– TaSe 2(0001) surfaces in the temperature range of 100–300 K. The experiments are performed in UHV with the use of LEED and SXPS by synchrotron radiation measurements. Deposition of Na on Cl 2-covered 1T– TaSe 2 at 100 K forms initially a [Formula: see text], which with increasing temperature to 300 K leads to NaCl formation. Adsorption of Cl 2 on Na-intercalated 1T and 2H– TaSe 2 surfaces at 100 K forms Cl 2 multilayers. The first Cl 2 layer, in contact with the substrate, interacts with the Na near the surface and forms [Formula: see text]. Warming up to 300 K leads to partial desorption of Cl 2, while the remaining chlorine interacts strongly with Na, causing the deintercalation of Na to the surface in the tendency to form NaCl. The intercalation–deintercalation process takes place across the van der Waals planes and it is much faster on 2H than on 1T– TaSe 2, which is attributed to the different crystal structure of 2H and 1T of TaSe 2.

MONTE-CARLO SIMULATION OF MBE GROWTH OF GaAs ANALYSIS OF RHEED

We have performed Monte-Carlo simulations of the growth of GaAs by MBE. We included in our calculations the anisotropy of the migration, the formation of As-and a partial desorption of the As. As an observable we calculated the RHEED signal of the specularly reflected electrons. The results have been compared with experimental data comprising both the damping of the oscillations and the recovery following a growth interrupt. The agreement between experiment and calculations is rather good. Moreover we could identify the mechanisms underlying the fast and the slow component of the recovery.