Vermiculite as a potential functional additive for water treatment bioreactors inhibiting toxic action of heavy metal cations upsetting the microbial balance.

A new adsorbent that combines mineral vermiculite with the yeast Saccharomyces cerevisiae, was used for Cd2+ removal. The influence of vermiculite presence on the toxic effects of Cd2+ to Saccharomyces cerevisiae yeast was evaluated as a function of the microorganisms' respiratory activity (CO2 production). The Cd2+ toxicity increased with prolonged exposure time reaching the LC50 value of 857 and 489 mg L-1 after 30 and 120 min, respectively. The yeast managed to bioaccumulate 25.0 ± 0.6 mg g-1 of Cd2+ at the initial Cd2+ concentration of 741.9 mg L-1; the maximum Cd2+ adsorption capacity of vermiculite reached 25 ± 5 mg g-1. The addition of the mineral decreased the cations toxic effect; the LC20 value in vermiculite absence attained approximately 200 mg L-1 after 30 min and decreased to 80 mg L-1 after 2 h, while in the bio-mineral system it was at the level of 435 ± 50 mg L-1 without a significant change in time. The mineral provided a superior living environment for the yeast by removing part of the cations, releasing essential microelements and providing a protective, clay hutch-like habitat for the cells.

Structural Studies of Aluminated form of Zeolites-EXAFS and XRD Experiment, STEM Micrography, and DFT Modelling.

In this article, the results of computational structural studies on Al-containing zeolites, via periodic DFT + D modelling and FDM (Finite Difference Method) to solve the Schrödinger equation (FDMNES) for XAS simulations, corroborated by EXAFS (Extended X-ray Absorption Fine Structure) spectroscopy and PXRD (powder X-ray diffractometry), are presented. The applicability of Radial Distribution Function (RDF) to screen out the postulated zeolite structure is also discussed. The structural conclusions are further verified by HR-TEM imaging.

Catalytic and photocatalytic oxidation of diphenyl sulphide to diphenyl sulfoxide over titanium dioxide doped with vanadium, zinc, and tin.

Samples of TiO2 (P25) doped with zinc, tin, and vanadium, thermally treated at 550 °C for 6 h, were tested as catalysts and photocatalysts for the oxidation of diphenyl sulphide to diphenyl sulfoxide and sulfone, using hydrogen peroxide as an oxidation agent. Thermal treatment of pure TiO2 and its vanadium-doped forms resulted in a decrease of anatase and an increase of rutile content. The opposite effect was observed for TiO2 doped with zinc or tin, where thermal treatment resulted in the rutile to anatase phase transition. The role of V, Zn, and Sn admixtures as TiO2 phase-composition controllers was postulated. The catalytic and photocatalytic activity was found to be influenced more by the rutile and anatase contents of the samples than the presence of admixtures. The rutile-containing samples, TiO2 and V-TiO2, presented much better activity in the catalytic oxidation of diphenyl sulphide compared with the catalysts that only contained the anatase phase, Sn-TiO2 and Zn-TiO2. The reaction efficiency was significantly improved under UV radiation. In this case, the best photocatalytic activity was found for calcined TiO2, containing both anatase and rutile components. An increase in rutile content, observed in the vanadium-doped TiO2, decreased the efficiency of the photocatalytic diphenyl sulphide oxidation. Thus, the presence of both anatase and rutile phases, with their favourable contributions, typical for P25, is necessary for the effective oxidation of Ph2S to Ph2SO. Moreover, it was shown that for the second oxidation stage, Ph2SO to Ph2SO2, the presence of the rutile phase is very important.

Spectroscopic CW-EPR and HYSCORE investigations of Cu(2+) and O(2)(-) species in copper doped nanoporous calcium aluminate (12CaO.7Al(2)O(3)).

Continuous wave (CW) and pulse electron paramagnetic resonance in a variant of hyperfine sublevel correlation spectroscopy (HYSCORE) were used for obtaining structural information concerning speciation and local environment of alien Cu(2+) and native O(2)(-) ions encaged in copper doped nanoporous 12CaO.7Al(2)O(3) (mayenite). The samples were prepared by a solid-state reaction and characterized by means of XRD, SEM, and Raman techniques. X-Band CW-EPR spectra showed that three different Cu(2+) species together with paramagnetic extraframework O(2)(-) anions were present in the mayenite sample, whereas extraframework OH(-) anions were revealed by Raman spectroscopy. (27)Al HYSCORE provided evidence for the interaction of Cu(2+) ions with the mayenite framework. Superhyperfine interaction of the Cu(2+) ions with proximal (d(Cu-OH) = 2.4 A) and distal (d(Cu-OH) = 5.0 A) OH(-) anions, located in the same and the nearby cage, respectively, was resolved by means of (1)H HYSCORE spectra. A different situation held for the encaged O(2)(-) radicals found to be sitting on the Ca(2+) ions. They exhibited only a weak superhyperfine interaction of 1 MHz with the (27)Al(3+) framework ions.