Ethanol separation using Sepabeads207 adsorbent

This work was aimed at evaluating the ethanol separation using Sepabeads207 adsorbent. A 10 wt% of ethanol solution was used as a model fermentation broth. The separation of ethanol from the solution was performed in a tube containing Sepabeads207 at different operating conditions: temperatures, 20 to 40°C; solution pH, 4 to 7; and contact times, 5 to 25 minutes. Recovery of ethanol via stripping was studied between 15 and 35 minutes, and at different air temperatures of 80 to 95°C. The concentration of liquid ethanol was measured using gas chromatography and refractometer. A higher ethanol concentration by Sepabeads207 adsorption was obtained at 20°C and solution pH 4 for 5 minutes, while the recovery was performed better at 80°C for 15 minutes. By applying these conditions, 10 wt% of ethanol in the solution was concentrated to 46 wt%. The ethanol adsorption data are: i). capacity of 0.22 g ethanol/g adsorbent, ii). selectivity of 7.75 (g ethanol/g water (adsorbed)) / (g ethanol/g water (original solution)), and iii). efficiency of 100%. Sepabeads207 is a promising adsorbent for ethanol separation from the dilute ethanol solution

A contribution to the mechanism of “reduced” CO₂ adsorbates electro-oxidation from combined spectroelectrochemical and voltammetric data

The nature of reduced CO2 adsorbates, as well as the mechanisms for their electro-oxidation on platinum, have been reviewed through the light of new experimental data obtained by cyclic voltammetry and by Fourier transform infrared reflectance spectroscopy. Three different “reduced” CO2 adsorbates are described as “‘ensembles”. It is suggested that they involve different extents of adsorbed entities, among which weakly bound and strongly bound hydrogen atoms play the most important role.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Chemisorption of methanol on different platinum electrodes (smooth and rough polycrystalline, monocrystalline, and preferentially oriented), as studied by EMIRS

EMIR spectra of methanol electroadsorbates on smooth and rough polycrystalline, monocrystalline and preferentially oriented platinum electrodes are reported. The (100)-type preferred oriented platinum behaves approximately as Pt (100) single crystals. On electrodispersed platinum electrodes the poisoning phenomena due to CO adsorbates appear to be reduced as compared to smooth platinum electrodes. EMIRS results correlate well with the electrochemical behaviour of the different platinum electrodes for methanol electrooxidation.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Pt-decorated nanoporous gold for glucose electrooxidation in neutral and alkaline solutions

Exploiting electrocatalysts with high activity for glucose oxidation is of central importance for practical applications such as glucose fuel cell. Pt-decorated nanoporous gold (NPG-Pt), created by depositing a thin layer of Pt on NPG surface, was proposed as an active electrode for glucose electrooxidation in neutral and alkaline solutions. The structure and surface properties of NPG-Pt were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and cyclic voltammetry (CV). The electrocatalytic activity toward glucose oxidation in neutral and alkaline solutions was evaluated, which was found to depend strongly on the surface structure of NPG-Pt. A direct glucose fuel cell (DGFC) was performed based on the novel membrane electrode materials. With a low precious metal load of less than 0.3 mg cm-2 Au and 60 μg cm-2 Pt in anode and commercial Pt/C in cathode, the performance of DGFC in alkaline is much better than that in neutral condition

Characterization of different FAD-dependent glucose dehydrogenases for possible use in glucose-based biosensors and biofuel cells

In this study, different flavin adenine dinucleotide (FAD)-dependent glucose dehydrogenases (FADGDHs) were characterized electrochemically after “wiring” them with an osmium redox polymer [Os(4,4′-dimethyl-2,2′-bipyridine)2(PVI)10Cl]+ on graphite electrodes. One tested FADGDH was that recently discovered in Glomerella cingulata (GcGDH), another was the recombinant form expressed in Pichia pastoris (rGcGDH), and the third was a commercially available glycosylated enzyme from Aspergillus sp. (AspGDH). The performance of the Os-polymer “wired” GDHs on graphite electrodes was tested with glucose as the substrate. Optimal operational conditions and analytical characteristics like sensitivity, linear ranges and current density of the different FADGDHs were determined. The performance of all three types of FADGDHs was studied at physiological conditions (pH 7.4). The current densities measured at a 20 mM glucose concentration were 494 ± 17, 370 ± 24, and 389 ± 19 μA cm−2 for GcGDH, rGcGDH, and AspGDH, respectively. The sensitivities towards glucose were 2.16, 1.90, and 1.42 μA mM−1 for GcGDH, rGcGDH, and AspGDH, respectively. Additionally, deglycosylated rGcGDH (dgrGcGDH) was investigated to see whether the reduced glycosylation would have an effect, e.g., a higher current density, which was indeed found. GcGDH/Os-polymer modified electrodes were also used and investigated for their selectivity for a number of different sugars