Cristina Segura

Kinetic study of Imidacloprid removal by advanced oxidation based on photo‐Fenton process

In this paper, the kinetics of Imidacloprid removal from aqueous solution by photo‐Fenton processes is presented. Experiments were conducted in batch mode, using a two litre jacketed Pyrex glass reactor, fitted with magnetic stirring, and six 6 W black light fluorescent lamps (λmax 365 nm), arranged in parallel to the reactor axis. The effect of initial Fe(II) concentration (<0.7 mM), incident photon flux (0 to 5·10−6 Einstein s−1), and temperature (288–313K) on the rate of Imidacloprid oxidation is also assessed. When Fe(II) is present as the initial source of iron ions, a first stage of almost instantaneous Imidacloprid removal is observed, followed by a slower process. A simplified kinetic model is described and fitted well experimental data, and could be used for process design, optimization, and control purposes.

Steam torrefaction of Eucalyptus globulus for producing black pellets: A pilot-scale experience

Steam torrefaction of Eucalyptus globulus was performed at temperatures between 245°C and 265°C in a 100kg/h pilot plant. Torrefied biomass was then pelletized in a 300kg/h unit and the pellets were subject to durability, density and combustion tests. The structural changes measured with FTIR were studied along with the combustion behavior of the materials. Compositional analysis showed that increasing the torrefaction temperature reduced both hemicellulose fraction and overall mass yield (MY). Furthermore, there was a linear relationship between the energy yield (EY) and mass yield (EY=[1.04-0.9(1-MY)]) for these samples. The ignition and comprehensive indexes confirmed that the stability of the torrefied biomass in a combustion environment was higher than for untreated biomass. Finally, pellets showed high durability (98%), and had an energy density (13-14GJ/m3), which is comparable to low-rank coals.

Effect of temperature on Imidacloprid oxidation by homogeneous photo-Fenton processes

This paper presents experimental results on the effect of temperature on the rate of Imidacloprid removal from waste water using homogeneous photo-Fenton processes. Experiments were conducted in a 2 L photo reactor set at 15-42 degrees C, initial concentrations in the range of 10 to 40 mg L(-1) Fe(II) and 100-450 mg L(-1) H(2)O(2); 30 150 min processing times. Initial H(2)O(2) concentration determined the extent of the oxidation process, whereas iron concentration played a key role in the process kinetics. Homogeneous photo-Fenton showed a fast initial reaction leading to 50% Imidacloprid degradation after less than 1 min of treatment, followed by a slower process until full removal was achieved. Rapid Fe(II) oxidation to Fe(III) seems responsible for the initial Imidacloprid removal. Imidacloprid removal fitted well a pseudo-first order kinetic scheme, with apparent activation energy of approximately 31.6 kJ/mole. Untreated Imidacloprid samples showed significant acute toxicity to Daphnia magna and genotoxic effects on Bacillus subtilis. Acute toxicity and genotoxicity remained detectable even after complete pesticide removal, showing that toxic by-products were present. The design and operation of photo Fenton processes should focus on toxicity removal rather than on specific target pollutants.

STUDY OF THE CATALYTIC CONVERSION AND ADSORPTION OF ABIETIC ACID ON ACTIVATED CARBON: EFFECT OF SURFACE ACIDITY

This study reports the adsorption and catalytic conversion of abietic acid as representative compound of tall oil, using activated carbons. Acid functional groups present on CGRAN activated carbons favored the adsorption of abietic acid, probably through a physical adsorption mechanism. In contrast, the conversion of abietic acid was not favored in DARCO activated carbon by increase of acid sites thought HNO3 treatment. The detection of neoabietic, palustric and/or levopimaric acids as reaction products indicate that the transformation of abietic acid was by dehydrogenation and/or isomerization routes. The negative influence of acid sites on the catalytic activity, in addition to the non-detection of volatile products, suggests that the cracking pathway for the conversion of abietic acid over these catalysts can be ruled out. Contrasting effects of the surface groups on the adsorption capacity and the conversion was observed: strong acid sites of CGRAN activated carbon favor the adsorption of abietic acid and decrease competitive adsorption between substrate and solvent, while conversion is not favored by these acid sites.