Jose Luis Sanchez-Salas

Degradation of 1-hydroxy-2,4-dinitrobenzene from aqueous solutions by electrochemical oxidation: role of anodic material.

Electrochemical oxidation (ECOx) of 1-hydroxy-2,4-dinitrobenzene (or 2,4-dinitrophenol: 2,4-DNP) in aqueous solutions by electrolysis under galvanostatic control was studied at Pb/PbO2, Ti/SnO2, Ti/IrxRuySnO2 and Si/BDD anodes as a function of current density applied. Oxidative degradation of 2,4-DNP has clearly shown that electrode material and the current density applied were important parameters to optimize the oxidation process. It was observed that 2,4-DNP was oxidized at few substrates to CO2 with different results, obtaining good removal efficiencies at Pb/PbO2, Ti/SnO2 and Si/BDD anodes. Trends in degradation way depend on the production of hydroxyl radicals (OH) on these anodic materials, as confirmed in this study. Furthermore, HPLC results suggested that two kinds of intermediates were generated, polyhydroxylated intermediates and carboxylic acids. The formation of these polyhydroxylated intermediates seems to be associated with the denitration step and substitution by OH radicals on aromatic rings, this being the first proposed step in the reaction mechanism. These compounds were successively oxidized, followed by the opening of aromatic rings and the formation of a series of carboxylic acids which were at the end oxidized into CO2 and H2O. On the basis of these information, a reaction scheme was proposed for each type of anode used for 2,4-D oxidation.

Inactivation of Ascaris eggs in water using sequential solar driven photo-Fenton and free chlorine

Sequential helminth egg inactivation using a solar driven advanced oxidation process (AOP) followed by chlorine was achieved. The photo-assisted Fenton process was tested alone under different H(2)O(2) and/or Fe(II) concentrations to assess its ability to inactivate Ascaris suum eggs. The effect of free chlorine alone was also tested. The lowest egg inactivation results were found using Fe(II) or H(2)O(2) separately (5 and 140 mmol L(-1), respectively) in dark conditions, which showed about 28% inactivation of helminth eggs. By combining Fe(II) and H(2)O(2) at the same concentrations described earlier, 55% of helminth egg inactivation was achieved. By increasing the reagents concentration two-fold, 83% egg inactivation was achieved after 120 min of reaction time. Process efficiency was enhanced by solar excitation. Using solar disinfection only, the A. suum eggs inactivation reached was the lowest observed (58% egg inactivation after 120 min (120 kJ L(-1))), compared with tests using the photo-Fenton process. The use of the photo-Fenton reaction enhanced the process up to over 99% of egg inactivation after 120 kJ L(-1) when the highest Fe(II) and H(2)O(2) concentration was tested. Practically no effect on the helminth eggs was observed with free chlorine alone after 550 mg min L(-1) was used. Egg inactivation in the range of 25-30% was obtained for sequential processes (AOP then chlorine) using about 150 mg min L(-1).

Enhanced Antibacterial Activity of CeO2 Nanoparticles by Surfactants

Abstract CeO2 nanoparticles (NPs) were tested to assess their toxicity on Escherichia coli strain in the presence of non-ionic surfactants. The NPs were dispersed in water by sonication at different pH values and times then mixed with three different surfactants (i.e., Triton X-100, Polyvinyl Pyrrolidone (PVP) and Tween 80) with a concentration of 0.001% v/v. It was found that sonication favored dispersion of the material and produced particles having 100 nm sizes in average. The material show toxicity to E. coli at pH 7 when growth using only minimal M9 media; no toxic response was observed for bacteria growth in rich media. The toxic effect in minimal media was enhanced by adding any of the non-ionic surfactants to the media. The use of CeO2 plus surfactant decreased the minimal inhibitory concentration (MIC) value of E. coli. The highest effect was observed for addition of Tween 80, in this case MIC value was 0.150 mg mL–1 compared to 3 mg mL–1 of CeO2 alone (almost 20 times improvement). These findings suggest the importance of different substances that can interact with NPs, like surfactants, usually present in wastewater systems that may lead to undesirable unexpected toxic characteristics in materials usually considered as innocuous.

In vitro antibacterial activity of meclofenamate metal complexes with Cd(II), Pb(II), Co(II), and Cu(II). Crystal structures of [Cd(C14H10NO2Cl2)2∙(CH3OH)]n and [Cu(C14H10NO2Cl2)2(C5H5N)2].

The synthesis and characterization of five metal complexes derived from sodium meclofenamate (1) are reported: [Cd(C14H10NO2Cl2)2∙(CH3OH)]n∙nCH3OH (6), [Pb(C14H10NO2Cl2)2]n (7), [Co(C14H10NO2Cl2)]n (8), [Cu(C14H10NO2Cl2)]n (9), and [Cu(C14H10NO2Cl2)2(C5H5N)2] (10) (C14H10NO2Cl2=meclofenamate; C5H5N=pyridine). The characterization of the compounds was based on FTIR and UV-visible spectroscopy, mass spectrometry and, in the case of complexes 6 and 10, single crystal X-ray diffraction analysis. For compound 6, the structural analysis revealed a 1-D polymeric chain structure, in which pentagonal planar [Cd(RCOO)2(CH3OH)] units were linked through bridging carboxylate functions of the meclofenamate ligands. The overall coordination environment of the Cd(II) ions was seven-coordinate, since each carboxylate group exhibited a μ3-bridging coordination mode. On the other hand, for complex 10 a discrete mononuclear structure was observed, in which the six-coordinate copper(II) metal atoms were coordinated by two pyridine molecules and the carboxylate functions of two meclofenamate entities, in an anisobidentate coordination mode. The antibacterial activity of compounds 6-9 against four strains of Gram positive (Staphylococcus aureus and Bacillus subtilis) and Gram negative (Escherichia coli and Pseudomonas aeruginosa) bacteria was examined, finding that only complex 6 was active. Additionally, it was found that the Co(II) and Cu(II) complexes 8 and 9 showed peroxidase activity.

Solar Water Disinfection Using NF-codoped TiO2 Photocatalysis: Estimation of Scaling-up Parameters

Abstract In this work, the use of previously reported figures-of-merit is proposed for the comparison of solar-driven photocatalytic disinfection technologies using NF-codoped TiO2. These figures-of-merit are based on the solar collection area per order (ACO) through the understanding of the overall kinetic behavior of the disinfection process under the tested conditions: pH 7, four different catalyst concentrations (0.0, 0.10, 0.25 and 50 mgmL− 1) and two solar radiation types (UV+visible and visible radiation alone). The results provide a direct link to the accumulated energy efficiency (the lowest the value the highest the efficiency) of the inactivation process, allowing the comparison between the efficiencies of a broad range of processes evaluating different experimental conditions.

Alkaloids from Bocconia frutescens. and Biological Activity of their Extracts

Abstract In Mexican traditional medicine, Bocconia frutescens. L. (Papaveraceae) is known as “gordolobo” or “llorasangre.” Natives use this plant to treat skin ulcer, dermatitis, and some respiratory tract infections. In this study, the aerial parts afforded the alkaloids dihydrochelerythrine, (±)-6-acetonyldihydrochelerythrine, (±)-6-acetonyldihydrosanguinarine, as well as β.-amyrine acetate and 2-decanol. The structures were determined by spectral methods including UV, IR, NMR and mass spectrometry. The antimicrobial activity of extracts and pure compounds was tested with Escherichia coli., Staphylococcus aureus., Pseudomonas aeruginosa., and Bacillus subtilis.. This study supports the use of B. frutescens. in traditional medicine.

Effect of mutant small, acid-soluble spore proteins containing cysteine or tryptophan on DNA properties in vivo and in vitro

Two derivatives of the alpha/beta-type small acid-soluble spore protein (SASP) SspCwt have been constructed, each containing a residue potentially useful for physico-chemical analysis of protein-protein or protein-DNA interactions. In one mutant protein (SspCtrp) residue 27 (Met) was replaced by Trp; in the second (SspCcys) residue 48 (Asn) was replaced by Cys. Both mutant proteins were expressed in Bacillus subtilis spores at levels similar to those of SspCwt, and SspCcys and SspCtrp restored ultraviolet light (UV) resistance and plasmid negative supercoiling in spores lacking major alpha/beta-type SASP to levels similar to those restored by SspCwt. While the purified mutant proteins bound more weakly to DNA than SspCwt, all three had the same relative affinity for different DNAs, ie poly(dG).poly(dC) greater than poly(dG-dC).poly(dG-dC) greater than pUC19, and purified SspCcys and SspCtrp gave the same pattern of DNase protected bands with pUC19 as SspCwt. Binding of SspCcys or SspCtrp to poly(dG).poly(dC) in vitro also prevented the formation of cyclobutane type cytosine dimers upon UV irradiation, as does binding of SspCwt. These data indicate that the two mutant proteins are extremely similar to SspCwt in their interaction with DNA, and thus may be useful in probing SASP-SASP and SASP-DNA interactions directly by physical or chemical techniques. Indeed, binding of SspCtrp to poly(dG).poly(dC) resulted in a 2.5-fold enhancement of the proteins Trp fluorescence.

Aerobic Treatment of Petroleum Industry Effluents

The main aerobic treatment methodologies for petroleum industry effluents are reviewed. This chapter includes a review of the main topics related to technical considerations and basic knowledge of the aerobic processes for application to petroleum and petroleum derivatives in effluents. Also, an analysis of the main characteristics of petroleum industry effluents is done followed by a review of the available literature on microbiological strains reported for application in petroleum and petroleum derivatives degradation. A fundamental analysis of the transformation processes and mechanisms through primary metabolism in the treatment processes is performed to provide accurate information on the basic processes occurring during effluent bio-treatment. Once all this basic information is reviewed, the chapter concentrates on detailed information on the various procedures available for the biological treatment of petrochemical effluents as well as an analysis of the state of the art in technology development for these applications. Technology topics such as the enhancement of petroleum bioavailability, the use of synthetic and natural tensioactives for biodegradation improvement and the use of genetically modified organisms are reviewed. Finally, a review of the novel trends and an analysis of current perspectives and challenges is included, using all the information from previous analyses.

Occupational exposure to heavy metals in a metal-mechanical auto part manufacturing plant in Puebla, Mexico

Aims: The concentration of Cd, Cr, Al and Pb present in inhalable air and deposited dust in a metal-mechanical parts manufacturing plant in Puebla, México were determined in order to assess the occupational exposure of workers in this plant. Materials and Methods: Fourteen air samples, six from the metal welding (MW) and eight from the metal forming (MF) areas, as well as metal dust accumulated on the floor of an auto part manufacturing plant, were collected. Sampling and analysis followed the National Institute for Occupational Safety and Health (NIOSH) recommended methods for metals in inhalable air. Results: The average concentration of Al and Cd determined in a volume of inhalable air were adequate under NIOSH maximal exposure concentration limits in both sampled sites. Average concentrations of 0.001 (MF sampling site) and 0.105 μg/L (MW sampling site) for Al; 0.003 (MF) and 0.0005 (MW) μg/L for Cd, with respect to the NIOHS limits, 10 and 0.005 μg/L, for Al and Cd, respectively. However, Cr and Pb concentrations exceeded or were close to the limits recommended by NIOHS in both places (0.5 and 0.05 μg/L for Cr and Pb, respectively). Average concentrations of 0.345 (MF) and 0.77 (MW) μg/L for Cr and 0.153 (MF) and 0.649 (MW) μg/L for Pb, were determined. Levels of metal content (Cd, Cr and Pb) in powder samples collected in both sampling sites were also higher than the suggested limits. Conclusion: The average concentration of Cr and Pb exceeded the limits recommended by the Occupational Safety and Health Administration and NIOSH for inhalable air in the workplace. Workers may be on risk of heavy metal occupational exposure. It is endorsed to implement safety measurements to avoid the breathing of contaminated air and also industrial level systems for dust and aerosol particle filtering or precipitation, altogether with stricter policies to regulate heavy metal exposure at these industries.