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Mexico City, Mexico

Camposeco R.,Mexican Institute of Petroleum | Castillo S.,Mexican Institute of Petroleum | Mejia I.,Mexican Institute of Petroleum | Mugica V.,Metropolitan Autonomous University | And 5 more authors.
Catalysis Communications

In this study we report the formation of nanocrystals and nanotubes of TiO 2 synthesized by the sol-gel method and hydrothermal treatment respectively. The obtained TiO 2 nanostructures were characterized by XRD, BET, TEM, UV-vis, XPS and FTIR; and evaluated in the CO oxidation. As for the nanotube-based samples, two catalysts were prepared (NTB5 and NTB10) through the hydrothermal treatment of nanosized titania in NaOH (5 and 10 N) at 160°C, followed by HCl rinsing until pH 1 was reached. From both catalysts, NTB10 showed the highest surface area (290 m 2/g), nanocrystals (15 nm) and stable phase (H 2Ti 3O 7) with a high CO oxidation capacity. We found that the band gap for NTB10 catalyst was of 2.85 eV, the lowest value respect to that of NTB5 and SGTB3 catalyst, based material (SGTB) showed both the lowest textural properties and catalytic performance. © 2011 Elsevier B.V. All rights reserved. Source

Sathish-Kumar K.,CINVESTAV | Solorza-Feria O.,CINVESTAV | Solorza-Feria O.,Hydrogen and Fuel Cells Group | Tapia-Ramirez J.,CINVESTAV | And 2 more authors.
International Journal of Hydrogen Energy

In microbial fuel cells (MFCs) efficient extracellular electron transfer microbes, also known as anode-respiring bacteria, play an important role on cell performance. This type of microbes can be developed by application of enrichment procedures. The objective of this study was to compare a chemical (only C, final terminal electron acceptor Fe(III)), an electrochemical (only E), and a hybrid method (H, i.e., E followed by 3 serial transfers in iron (III) citrate medium) enrichment methods departing from a saline-sodic soil inoculum. In the electrochemical enrichment procedure in an electrolysis cell, the inoculum was subjected to a continuous electrical stress continually by posing the cell at -150 mV/SCE (+94 mV/SHE). The only C enrichment method delivered powers superior to the only E one (higher values of PAn,max = 49 mW m-2 and PV,max = 558 mW m-3 of C compared to 33 and 379 of only E). Interestingly, overall resistance as determined by EIS was lower for only E (1240 Ω) than for only C (1632 Ω). Yet, the hybrid H method, showed electrochemical characteristics consistently superior to both only C and only E methods (higher PAn,max and PV,max, lower internal resistance). Further detailed electrochemical studies of only E-method showed that the anodic resistance decreased with the time of operation of the electrolysis cell that would be consistent with the adaptability/ enrichment purpose of the method. Also, Cyclic voltammetry peaks with values close to those reported for bacterial cytochromes appeared with time of cell operation. To the best of our knowledge, this is the first time that it is reported that serial transfers with Fe(III) as electron acceptor to an inoculum previously enriched in an electrolysis cell, leads to improved characteristics of MFC and increased Fe(III)-reducing capability of the inoculum. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

Robles-Gonzalez V.,ENCB IPN | Galindez-Mayer J.,ENCB IPN | Rinderknecht-Seijas N.,ESIQIE IPN | Poggi-Varaldo H.M.,Energy and Environmental Research Center
Journal of Biotechnology

Mexican distilleries produce near eight million liters of mezcal per year, and generate about 90 million liters of mezcal vinasses (MV). This acidic liquid waste is very aggressive to the environment because of its high content of toxic and recalcitrant organic matter. As a result, treatment is necessary before discharge to water bodies. It is interesting, yet disturbing; verify that there is a significant gap on the treatment of MV. However, there is an abundant body of research on treatment of other recalcitrant toxic effluents that bear some similarity to MV, for example, wine vinasse, vinasses from the sugar industry, olive oil, and industrial pulp and paper wastewaters. The objective of this review is to critically organize the treatment alternatives of MV, assess their relative advantages and disadvantages, and finally detect the trends for future research and development. Experience with treatment of this set of residuals, indicates the following trends: (i) anaerobic digestion, complemented by oxidative chemical treatments (e.g. ozonation) are usually placed as pretreatments, (ii) aerobic treatment alone and combined with ozone which have been directed to remove phenolic compounds and color have been successfully applied, (iii) physico-chemical treatments such as Fenton, electro-oxidation, oxidants and so on., which are now mostly at lab scale stage, have demonstrated a significant removal of recalcitrant organic compounds, (iv) fungal pretreatment with chemical treatment followed by oxidative (O 3) or anaerobic digestion, this combination seems to give attractive results, (v) vinasses can be co-composted with solid organic wastes, particularly with those from agricultural activities and agro-industies; in addition to soil amenders with fertilizing value to improve soil quality in typical arid lands where agave is cultivated, it seems to be a low cost technology very well suited for rural regions in underdeveloped countries where more sophisticated technologies are difficult to adopt, due to high costs and requirements of skilled personnel. © 2011 Elsevier B.V. Source

Valor A.,IPN ESIQIE | Caleyo F.,IPN ESIQIE | Alfonso L.,National Autonomous University of Mexico | Velazquez J.C.,ESIQIE IPN | Hallen J.M.,IPN ESIQIE
Mathematical Problems in Engineering

The stochastic nature of pitting corrosion of metallic structures has been widely recognized. It is assumed that this kind of deterioration retains no memory of the past, so only the current state of the damage influences its future development. This characteristic allows pitting corrosion to be categorized as a Markov process. In this paper, two different models of pitting corrosion, developed using Markov chains, are presented. Firstly, a continuous-time, nonhomogeneous linear growth (pure birth) Markov process is used to model external pitting corrosion in underground pipelines. A closed-form solution of the system of Kolmogorov's forward equations is used to describe the transition probability function in a discrete pit depth space. The transition probability function is identified by correlating the stochastic pit depth mean with the empirical deterministic mean. In the second model, the distribution of maximum pit depths in a pitting experiment is successfully modeled after the combination of two stochastic processes: pit initiation and pit growth. Pit generation is modeled as a nonhomogeneous Poisson process, in which induction time is simulated as the realization of a Weibull process. Pit growth is simulated using a nonhomogeneous Markov process. An analytical solution of Kolmogorov's system of equations is also found for the transition probabilities from the first Markov state. Extreme value statistics is employed to find the distribution of maximum pit depths. © 2013 A. Valor et al. Source

Vazquez-Larios A.L.,CINVESTAV | Poggi-Varaldo H.M.,CINVESTAV | Solorza-Feria O.,CINVESTAV | Rinderknecht-Seijas N.,ESIQIE IPN
International Journal of Hydrogen Energy

This research aimed at evaluating the effect of inoculum type and the application of RuxMoySez as a cathode catalyst on the treatment and bioelectricity production of a microbial fuel cell (MFC) fed with a municipal leachate. The inocula assayed were a plain sulphate-reducing inoculum (In-SR), an enrichment in Mn(IV)-reducing bacteria (In-EMn(IV)), and two enrichments in Fe(III)-reducing bacteria, namely, In-EFe(III)-S and In-EFe(III)-SR. In the batch experiments where the cells were operated with the faces connected in parallel and loaded with an external resistance of 100 Ω, enriched inocula had a significant, positive effect of cell performance. The average volumetric powers PV-ave observed ranged from 2146 (In-SR) to 13 304 mW/m3 (In-EFe(III)-S). The highest value of PV-ave achieved in our work was about 30% of that of commercial anaerobic digestion of wastes. Application of inocula enriched in Fe(III) and Mn (IV)-reducing bacteria significantly improved the performance of cells that used RuxMoySez as a cathodic catalyst for the oxygen reduction reaction. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

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