Showing papers by "Marta I. Litter published in 2014"

TiO2-photocatalytic transformation of Cr(VI) in the presence of EDTA: Comparison of different commercial photocatalysts and studies by Time Resolved Microwave Conductivity

Abstract: The photocatalytic efficiency for Cr(VI) transformation in the presence of etilendiaminetetraacetic acid (EDTA) at pH 2 over various commercial TiO 2 samples (Evonik P25, Cristal Global PC50, PC100 and PC500, Hombikat UV100, Fluka and Kemira S230) was evaluated. The decay was adjusted to a pseudo-first order kinetics in all cases and the photocatalytic activity of the samples was estimated from the kinetic constants. The order of the photocatalytic activity was PC500 ≅ UV100 > P25 ≅ PC100 > S230 ≅ PC50 ≫ Fluka and it strongly depends on the nature of the TiO 2 samples, especially on the specific surface area, except for S230 and for P25. The formation of the Cr(III)–EDTA complex in solution as a product of the Cr(VI) photocatalytic reduction was confirmed by visible spectrophotometry. Simultaneous kinetics of Cr(VI) reduction and of Cr(III)–EDTA formation has been determined for the first time and the results indicate that evolution of both species are related. TRMC measurements were applied for the first time to a reductive heterogeneous photocatalytic reaction of a metal ion system, and the experimental results were adjusted to a power law decay, relating the data to those of the photocatalytic experiments.

Photochemical reduction of U(VI) in aqueous solution in the presence of 2-propanol

Abstract: The efficiency of the photochemical reduction of uranyl (UO 2 2+ ) (0.25 mM, pH 3) was analyzed in the absence and in the presence of 2-propanol (2-PrOH), evaluating the effect of anions (nitrate, acetate and perchlorate) and the use of quartz and glass photoreactors. A higher removal was observed under all conditions with the quartz photoreactor; the best system was that starting from uranyl nitrate, where a 90% UO 2 2+ removal was attained after 15 min irradiation. In the absence of 2-PrOH, the acetate system was the only one where some U(VI) removal was observed (15% after 15 min in the quartz photoreactor) but, in the presence of the alcohol, the acetate system was the least reactive. Under irradiation, nitrate and acetate were consumed during the reaction, causing important effects on the uranyl conversion, while perchlorate was inactive. Uranium was removed from the system as a solid residue in the case of nitrate- (as U(IV)) and perchlorate-containing systems (as U(VI)), while it remained in solution in the case of the acetate systems. Mechanisms are proposed for the different conditions. The importance of nitrate as a reducing agent of uranium species has not been previously reported. The use of uranyl nitrate and short-near UV–vis light seems to be the most advisable way of removing uranyl from solutions, in the form of a stable precipitate.

One Century of the Discovery of Arsenicosis in Latin America (1914-2014) As2014 : Proceedings of the 5th International Congress on Arsenic in the Environment, May 11-16, 2014, Buenos Aires, Argentina

Abstract: The Congress "Arsenic in the Environment" offers an international, multi- and interdisciplinary discussion platform for research aimed towards a holistic solution to the problem posed by the environmental toxin arsenic, with considerable societal impact. The congress has focused on cutting edge and breakthrough research in physical, chemical, toxic

Metallurgical Slag as an Efficient and Economical Adsorbent of Arsenic

Abstract: Water contamination by arsenic has been recorded as an important health problem of global concern; even though the adsorption process has shown to be one of the best removal technologies, there are no adsorbents able to reduce its concentration to drinking water standards (0.010 mg/l) when arsenic is present at high initial concentrations (>1 mg As/l), with an acceptable cost–benefit ratio. This study aims to demonstrate that metallurgical slag (SL) is an efficient and economical adsorbent of arsenic present in water at high initial concentrations by comparing removal efficiencies and treatment costs, using slags and zero-valent iron nanoparticles. Slag was less efficient, in terms of the maximum adsorption capacity, but it produced effluents meeting the limit (0.025 mg/l) of the Mexican drinking water standards, when a 6 mg As/l solution was treated. Considering this, the use of SL instead of expensive commercial adsorbents will make the adsorption process of arsenic for water treatment feasible.

Adsorption of Boron by Metallurgical Slag and Iron Nanoparticles

Abstract: Boron is a problematic pollutant because of the difficulty involved in removing it from water with an acceptable cost-to-benefit ratio, especially at extremely high concentrations (600 mg B/l). It is also necessary to remove the pollutant to comply with the quality criteria for drinking water (1 mg B/l) and even for agricultural irrigation purposes (0.5-15 mg B/l depending on crop tolerance). Although some newly proposed water-treatment technologies use economical adsorbents, they are unable to achieve the residual concentrations. The aim of this work is to show that adsorption using metallurgical slags (SL) can be used either as a pre-treatment of the zero-valent iron nanoparticles (nano-Fe0) or as a final treatment itself for removing boron at high concentrations to obtain effluents complying with the standards established for drinking water and wastewater reuse. Adsorption tests (kinetics and isotherms) were carried out for both adsorbents. The slags showed good results as an adsorbent for boron remova...