Reyna Natividad

Enhancing the electrochemical Cr(VI) reduction in aqueous solution.

In this study we present the cathodic Cr(VI) reduction using electrodissolution of iron anode. In batch experiments we tested four different cathodic materials; the best conditions were found when copper was used. It is observed that when more current is applied into the electrochemical cell faster reduction rates are achieved. Continuous experiments also reveal that Cr(VI) reduction could be done in a very efficient way. To confirm the experimental data, cyclic voltammetry was used and it was found that the cathodic Cr(VI) reduction is taking place.

Biodiesel Production by Using Heterogeneous Catalysts

In recent years, biodiesel has gained international attention as a source of alternative fuel due to characteristics like high degradability, no toxicity, low emission of carbon monoxide, particulate matter and unburned hydrocarbons (Al Zuhair, 2007; Vicente et al., 1998). Biodiesel is a mixture of alkyl esters and it can be used in conventional compression ignitions engines, which need almost no modification. As well, biodiesel can be used as heating oil and as fuel (Mushrush et al., 2001; Wardle, 2003). So far, this alternative fuel has been successfully produced by transesterification of vegetable oils and animal fats using homogeneous basic catalysts (mainly sodium or potassium hydroxide dissolved in methanol). Traditional homogeneous catalysts (basic or acid) possess advantages including high activity (complete conversion within 1 h) and mild reaction conditions (from 40 to 65 °C and atmospheric pressure). However, the use of homogeneous catalysts leads to soap production. Besides, in the homogeneous process the catalyst is consumed thus reducing the catalytic efficiency. This causes an increase in viscosity and the formation of gels. In addition, the method for the removal of the catalyst after reaction is technically difficult and a large amount of wastewater is produced in order to separate and clean the products, which increases the overall cost of the process. Thus, the total cost of the biodiesel production based on homogeneous catalysis, is not yet sufficiently competitive as compared to the cost of diesel production from petroleum. An alternative is the development of heterogeneous catalysts that could eliminate the additional running costs associated with the aforementioned stages of separation and purification. In addition, the use of heterogeneous catalysts does not produce soap through free fatty acid neutralization and triglyceride saponification. Therefore, development of efficient heterogeneous catalysts is important since opens up the possibility of another pathway for biodiesel production. The efficiency of the heterogeneous process depends, however, on several variables such as type of oil, molar ratio alcohol to oil, temperature and catalyst type. Thus, the objective of this chapter is to present a review of the effect of the aforesaid variables on important characteristics of biodiesel such as methyl esters content. Some characterization techniques for both, biodiesel and heterogeneous catalysts will also be addressed.

Ozonation of Indigo Carmine Catalyzed with Fe-Pillared Clay

The ozonation catalyzed by iron-pillared clays was studied. The degradation of dye indigo carmine (IC) was elected as test reaction. Fe-pillared clays were synthesized by employing hydrolyzed FeCl3 solutions and bentonite. The pillared structure was verified by XRD and by XPS the oxidation state of iron in the synthesized material was established to be

Biological hazard evaluation of a pharmaceutical effluent before and after a photo-Fenton treatment

The aim of this study was to evaluate the biological hazard of a pharmaceutical effluent before and after treatment. For the former, the determined 96h-LC50 value was 1.2%. The photo-Fenton treatment catalyzed with an iron-pillared clay reduced this parameter by 341.7%. Statistically significant increases with respect to the control group (P<0.05) were observed at 12, 24, 48 and 72h in HPC (50.2, 30.4, 66.9 and 43.3%), LPX (22, 83.2, 62.7 and 59.5%) and PCC (14.6, 23.6, 24.4 and 25.6%) and antioxidant enzymes SOD (29.4, 38.5, 32.7 and 49.5%) and CAT (48.4, 50.3, 38.8 and 46.1%) in Hyalella azteca before treatment. Also increases in damage index were observed before treatment of 53.1, 59.9, 66.6 and 72.1% at 12, 24, 48 and 72h, respectively. After treatment the same biomarkers of oxidative stress decreased with respect to before treatment being to HPC (29.3, 22.5, 41.6 and 31.7%); LPX (14.2, 43.1, 30.7 and 35.5%); PCC (12.6, 21.3, 24.2 and 23.9%); SOD (39.2, 33.9, 49.5 and 37.9%) and CAT (28.6, 35.8, 33.7 and 31.7) at 12, 24, 48 and 72h, respectively (P<0.05). The damage index were decreased at 12, 24, 48 and 72h in 48.9, 57.8, 67.3 and 72.1%, respectively. In conclusion, the obtained results demonstrate the need of performing bioassays in order to characterize an effluent before discharge and not base such a decision only upon current normativity. In addition, it was also concluded that the heterogeneous photo-Fenton process decreases the presence of PCT, oxidative stress, genotoxic damage and LC50 in Hyalella azteca.

Ozonation of Indigo Carmine Enhanced by Fe/Pimenta dioica L. Merrill Particles

Green synthesis of metallic particles has become an economic way to improve and protect the environment by decreasing the use of toxic chemicals and eliminating dyes. The synthesis of metal particles is gaining more importance due to its simplicity, rapid rate of synthesis of particles, and environmentally friendly. The present work aims to report a novel and environmentally friendly method for the synthesis of iron particles using deoiled Pimenta dioica L. Merrill husk as support. The indigo carmine removal efficiency by ozonation and catalyzed ozonation is also presented. Synthesized materials were characterized by N2 physisorption and scanning electron microscopy (SEM/EDS). By UV-Vis spectrophotometry the removal efficiency of indigo carmine was found to be nearly 100% after only 20 minutes of treatment under pH 3 and with a catalyst loading of 1000 mgL−1. Analytical techniques such as determination of the total organic carbon content (TOC) and chemical oxygen demand (COD) showed that iron particles supported on deoiled Pimenta dioica L. Merrill husk can be efficiently employed to degrade indigo carmine and achieved a partial mineralization (conversion to CO2 and H2O) of the molecule. From the results can be inferred that the prepared biocomposite increases the hydroxyl radicals generation.

Oxidation of 4-Chlorophenol by Mesoporous Titania: Effect of Surface Morphological Characteristics

Mesoporous nanocrystalline anatase was prepared via EISA employing CTAB as structure directing agent. The drying rate was used as a key synthesis parameter to increase the average pore diameter. The resultant mesoporous crystalline phases exhibited specific surface areas between 55 and 150 m2 g−1, average unimodal pore sizes of about 3.4 to 5.6 nm, and average crystallite size of around 7 to 13 nm. These mesophases were used as photocatalysts for the degradation of 4-chlorophenol (4CP) with UV light. Under the studied conditions, the mesoporous anatase degraded 100% 4CP. This was twice faster than Degussa P-25. 57% reduction of chemical oxygen demand (COD) value was achieved.

Synthesis, Characterization, and Catalytic Activity of Platinum Nanoparticles on Bovine-Bone Powder: A Novel Support

Pt nanoparticles supported on bovine-bone powder were obtained by a rather simple method consisting of immersing powder of bovine bone into a Pt+4 metal ion solution at room temperature and subsequent reduction by sodium borohydride. This method eliminates the calcination step of the usual catalyst preparation methods. The nanocomposite was characterized by transmission electron microscopy (TEM), which revealed uniformly dispersed platinum nanoparticles with average particle size of 2.2 nm ± 0.6 nm. The XPS studies exhibited the presence of 63% Pt° and 37% PtO. The catalytic activity was tested in the hydrogenation of 2-butyne-1,4-diol. The nanocomposite shows good catalytic performance with nearly 100% conversion and 83% selectivity towards 2-butene-1,4-diol.

Enhancing the ozonation of industrial wastewater with electrochemically generated copper(II) ions

ABSTRACT This study evaluates the effect of adding electrochemical copper(II) ions into an ozonation process for treating industrial wastewater. Combining the processes resulted in a synergy that enhanced the reduction of physicochemical parameters (COD, TOC, color, turbidity, Z-Potential, and conductivity). In only 15 minutes the integrated process reduced the COD by 83%, TOC by 78 %, color by 93%, turbidity by 77%, and conductivity by 27% at relatively low current density (12.5 mA cm−2). Thus, the combination of the electrochemical and ozonation processes noticeably improves wastewater quality, decreases the process time, and reduces the sludge production.

Comparison of AOPs Efficiencies on Phenolic Compounds Degradation

In this work, a comparison of the performances of different AOPs in the phenol and 4-chlorophenol (4-CP) degradation at lab and pilot scale is presented. It was found that, in the degradation of phenol, the performance of a coupled electro-oxidation/ozonation process is superior to that observed by a photo-Fenton process. Phenol removal rate was determined to be 0.83 mg L−1 min−1 for the coupled process while the removal rate for photo-Fenton process was only 0.52 mg L−1 min−1. Regarding 4-CP degradation, the complete disappearance of the molecule was achieved and the efficiency decreasing order was as follows: coupled electro-oxidation/ozonation > electro-Fenton-like process > photo-Fenton process > heterogeneous photocatalysis. Total organic carbon was completely removed by the coupled electro-oxidation/ozonation process. Also, it was found that oxalic acid is the most recalcitrant by-product and limits the mineralization degree attained by the technologies not applying ozone. In addition, an analysis on the energy consumption per removed gram of TOC was conducted and it was concluded that the less energy consumption is achieved by the coupled electro-oxidation/ozonation process.

Kinetics of Transesterification of Safflower Oil to Obtain Biodiesel Using Heterogeneous Catalysis

Abstract The kinetics of the transesterification of safflower oil and methanol catalyzed by K2O/NaX was studied and modeled. The influence of the oil-methanol initial molar ratio and amount of catalyst were investigated to achieve a maximum triglycerides conversion (99 %) and a final methyl esters content of 94 % ±1. A kinetic model based on an Eley–Rideal mechanism was found to best fit the experimental data when assuming methanol adsorption as determining step. Other models derived from Langmuir – Hinshelwood – Hougen –Watson (LHHW) mechanisms were rejected based on statistical analysis, mechanistic considerations and physicochemical interpretation of the estimated parameters.