Multiscale Modeling of Barium Sulfate Formation from BaO

The present paper presents a multiscale (DFT to mean-field) modeling approach for describing barium sulfate formation through the adsorption of sulfur oxides on BaO. Sulfur oxide emissions, a major environmental concern, also represent one of the technological issues for a large-scale implementation of alkaline-earth oxides as NO<i>x</i> abatement techniques for vehicle exhaust depollution. SO<i>x</i> adsorption was studied at the atomic level on various BaO sites (terraces, surface defects, and bulk) for a closer description of a real storage material. Ab initio data were used to conceive a kinetic model for SO<i>x</i> adsorption that allows us to follow species adsorption and desorption dynamics. Our results confirm that sulfur oxides interact strongly with the NO<i>x</i> trapping material to form thermodynamically favored sulfate species, consequently leading to the blockage of NO<i>x</i> sorption sites and altering the storage properties

Influence of Operational Parameters in the Heterogeneous Photo-Fenton Discoloration of Wastewaters in the Presence of an Iron-Pillared Clay

An iron-pillared Tunisian clay (Fe-PILC) was prepared and used as the catalyst in the heterogeneous photo-Fenton oxidation of Red Congo and Malachite Green in aqueous solution. The catalyst Fe-PILC was characterized by XRF, XRD, BET, and FTIR methods. This physicochemical characterization pointed to successful iron pillaring of the clay. The influence of several operational parameters such as the pH, H₂O₂ concentration, catalyst dosage, and initial dye concentration was evaluated. A solution pH in the range 2.5–3, the addition of 8 mL of 200 mg/L H₂O₂, and a catalyst dosage of 0.3 g/L appeared as the most favorable reaction conditions for achieving complete discoloration, either for Red Congo or Malachite Green, although oxidation was found to be slower and more complicated in the former case. The kinetics of discoloration of both dyes followed a pseudo-first-order rate law. In general, 20 min of UV irradiation was enough to achieve 100% discoloration of the aqueous solution. UV–vis and chemical oxygen demand measurements indicated, however, that longer reaction times of around 1 h were required for achieving dye mineralization. Leaching tests confirmed a very low amount of dissolved iron and good stability of the catalyst, with almost unaltered discoloration efficiency upon three cycles. Hence, taking into account the favorable photocatalytic properties and low leaching of iron ions, such iron-pillared clay can be considered a promising catalyst for dye wastewater treatment