Erika Bustos

Novel Electro-Fenton Approach for Regeneration of Activated Carbon

An electro-Fenton-based method was used to promote the regeneration of granular activated carbon (GAC) previously adsorbed with toluene. Electrochemical regeneration experiments were carried out using a standard laboratory electrochemical cell with carbon paste electrodes and a batch electrochemical reactor. For each system, a comparison was made using FeSO4 as a precursor salt in solution (homogeneous system) and an Fe-loaded ion-exchange resin (Purolite C-100, heterogeneous system), both in combination with electrogenerated H2O2 at the GAC cathode. In the two cases, high regeneration efficiencies were obtained in the presence of iron using appropriate conditions of applied potential and adsorption-polarization time. Consecutive loading and regeneration cycles of GAC were performed in the reactor without great loss of the adsorption properties, only reducing the regeneration efficiency by 1% per cycle during 10 cycles of treatment. Considering that, in the proposed resin-containing process, the use of Fe salts is avoided and that GAC cathodic polarization results in efficient cleaning and regeneration of the adsorbent material, this novel electro-Fenton approach could constitute an excellent alternative for regenerating activated carbon when compared to conventional methods.

Glassy carbon electrodes modified with composites of starburst-PAMAM dendrimers containing metal nanoparticles for amperometric detection of dopamine in urine.

Composites of hydroxyl-terminated PAMAM dendrimers, generation 4.0 (64 peripheral OH groups) containing either Ir, Pt or Rh nanoparticles were synthesized and characterized in solution. Each one of these composites was then immobilized on a glassy carbon electrode (GC) and incorporated as an amperometric detector for dopamine in a high-performance liquid chromatograph (HPLC). Comparison of the analytical performance of the novel electrochemical detectors with a typical UV-vis optical detector for dopamine revealed that the sensitivity of the GC electrode modified with dendrimer-Rh composite is comparable to that of the spectroscopic detector, with a detection limit of 0.15muM, and is linear up to at least 1.0mM (R(2)=0.998). Furthermore, it was found that the electroanalytical approach suffers minimal matrix effects that arise in the analysis of dopamine in samples of urine.

Applications of dendrimers in drug delivery agents, diagnosis, therapy, and detection

In recent years, the application of dendrimers in biomedicine attracted much attention from scientists. Dendrimers are interesting for biomedical applications because of their characteristics, including: a hyperbranching, well-defined globular structures, excellent structural uniformity, multivalency, variable chemical composition, and high biological compatibility. In particular, the three-dimensional architecture of dendrimers can incorporate a variety of biologically active agents to form biologically active conjugates. This review of dendrimers focuses on their use as protein mimics, drug delivery agents, anticancer and antiviral therapeutics, and in biomedical diagnostic applications such as chemically modified electrodes.

Design, self-assembly, and photophysical properties of pentameric metallomacrocycles: [M5(N-hexyl[1,2-bis(2,2':6',2''-terpyridin-4-yl)]carbazole)5][M = Fe(II), Ru(II), and Zn(II)].

A novel family of metallopentacycles was constructed by the facile self-assembly of a bis(terpyridine)-carbazole monomer utilizing terpyridine-metal(II)-terpyridine connectivity; its photophysical properties were investigated.

Synthesis of a water-soluble hexameric metallomacrocycle and its oxidized single-wall carbon nanotube composite

Polycationic water-soluble metallomacrocycles possessing 12 positive charges that facilitate ionic coordination with the carboxylate moieties of Oxi-SWNTs form a nanotube composite en route to tailored electronic properties. The multiple ionic pair interactions between the positively charged metallohexamers and carboxylate modified SWNT are evidenced by TEM and AFM images.

Preparation of IrO2-Ta2O5|Ti electrodes by immersion, painting and electrophoretic deposition for the electrochemical removal of hydrocarbons from water

After intense years of great development, the electrochemical technologies have become very suitable alternatives in niche markets like industrial wastewater reclamation and soil remediation. A key role to achieve a high efficiency in such treatments is played by the characteristics of the coating of the electrodes employed. This paper compares three techniques, namely immersion, painting and electrophoresis, for the preparation of IrO2-Ta2O5ǀTi, so-called dimensionally stable anodes (DSA(®)). The quality of the coatings has been investigated by means of surface and electrochemical analysis. Their ability to generate hydroxyl radicals and degrade aqueous solutions of hydrocarbons like phenanthrene, naphthalene and fluoranthene has been thoroughly assessed. Among the synthesis techniques, electrophoretic deposition yielded the best results, with DSA(®) electrodes exhibiting a homogeneous surface coverage that led to a good distribution of active sites, thus producing hydroxyl radicals that were able to accelerate the degradation of hydrocarbons.

Using a Gridded Global Dataset to Characterize Regional Hydroclimate in Central Chile

AbstractCentral Chile is facing dramatic projections of climate change, with a consensus for declining precipitation, negatively affecting hydropower generation and irrigated agriculture. Rising from sea level to 6000 m within a distance of 200 km, precipitation characterization is difficult because of a lack of long-term observations, especially at higher elevations. For understanding current mean and extreme conditions and recent hydroclimatological change, as well as to provide a baseline for downscaling climate model projections, a temporally and spatially complete dataset of daily meteorology is essential. The authors use a gridded global daily meteorological dataset at 0.25° resolution for the period 1948–2008, adjusted by monthly precipitation observations interpolated to the same grid using a cokriging method with elevation as a covariate. For validation, daily statistics of the adjusted gridded precipitation are compared to station observations. For further validation, a hydrology model is driven...

Glassy carbon electrodes sequentially modified by cysteamine-capped gold nanoparticles and poly(amidoamine) dendrimers generation 4.5 for detecting uric acid in human serum without ascorbic acid interference

Glassy carbon electrodes (GCE) were sequentially modified by cysteamine-capped gold nanoparticles (AuNp@cysteamine) and PAMAM dendrimers generation 4.5 bearing 128-COOH peripheral groups (GCE/AuNp@cysteamine/PAMAM), in order to explore their capabilities as electrochemical detectors of uric acid (UA) in human serum samples at pH 2. The results showed that concentrations of UA detected by cyclic voltammetry with GCE/AuNp@cysteamine/PAMAM were comparable (deviation <±10%; limits of detection (LOD) and quantification (LOQ) were 1.7×10(-4) and 5.8×10(-4) mg dL(-1), respectively) to those concentrations obtained using the uricase-based enzymatic-colorimetric method. It was also observed that the presence of dendrimers in the GCE/AuNp@cysteamine/PAMAM system minimizes ascorbic acid (AA) interference during UA oxidation, thus improving the electrocatalytic activity of the gold nanoparticles.

Electrokinetic – Enhanced ryegrass cultures in soils polluted with organic and inorganic compounds

Abstract The effect of electric fields on seed germination and development of ryegrass (Lolium perenne L.) was studied in clean and contaminated soil with heavy metals and/or PAHs. The application of 0.2 DCV/cm in clean soil near ryegrass seeds enhanced the germination by 75%. The presence of contaminants in soil hindered the germination and growing of ryegrass. However, the application of DC electric field favored the germination and growing of plants compensating the negative effects of the contaminants. The electrode material in anodes has a decisive influence in the germination and growing of ryegrass. Stable anode materials have to be used to avoid the release of toxic ions in the soil that affect the development of the plant. Graphite anodes are very appropriate because they are inexpensive and does not generate toxic effects on plants. The electro‐phytoremediation of mixed contaminated soil with ryegrass showed very promising results, especially AC electric fields. The tests with AC current showed the highest biomass production in a treatment of 1 month. The more biomass production the more removal of heavy metals and PAHs from soil. HighlightsLow DC electric fields enhanced the germination and growing of ryegrass, even in contaminated soils.Contaminants in soil hindered the germination and development of plants.Better germination and plant development was observed with stable anode materials.AC electric field enhanced the the phytoremediation of mixed contaminated soil with heavy metals and PAHs.

Electrochemical Incineration of Phenolic Compounds from the Hydrocarbon Industry Using Boron-Doped Diamond Electrodes

Electrochemical incineration using boron-doped diamond electrodes was applied to samples obtained from a refinery and compared to the photo-electro-Fenton process in order to selectively eliminate the phenol and phenolic compounds from a complex matrix. Due to the complex chemical composition of the sample, a pretreatment to the sample in order to isolate the phenolic compounds was applied. The effects of the pretreatment and of pH on the degradation of the phenolic compounds were evaluated. The results indicate that the use of a boron-doped diamond electrode in an electrochemical incineration process mineralizes 99.5% of the phenolic sample content. Working in acidic medium (pH = 1), and applying 2 A at 298 K under constant stirring for 2 hours, also results in the incineration of the reaction intermediates reflected by 97% removal of TOC. In contrast, the photo-electro-Fenton process results in 99.9% oxidation of phenolic compounds with only a 25.69% removal of TOC.