Diacetate Cellulose-Silicon Bionanocomposite Adsorbent for Recovery of Heavy Metal Ions and Benzene Vapours: An Experimental and Theoretical Investigation

The diacetate cellulose-silicon bionanocomposite adsorbent (DACSBNC) was first introduced to recover heavy metal ions and benzene vapors. The adsorption thermodynamics of heavy metal ions and benzene vapors on the DACSBNC was first investigated by the adsorption-calorimetric, X-ray, and theoretical methods. The observed results confirmed that (i) the adsorption capacitance of DACSBNC for cadmium (II), mercury (II), and lead (II) ions were accounted for 12.23, 13.87, and 31.40 mg/g, respectively; (ii) the sorption capacitance of DACSBNC for benzene vapors was 0.5618 mmol/g. The quantum chemical calculation was also carried out on the density functional theory (DFT) using the 6-31G (d, p)/B3LYP basis sets in Gaussian 09. The results of the quantum chemical analysis support the experimental results.

Impedance Study of Adsorption of Chloride Ions in Ethanol on Bi(001) Single Crystal Plane

The impedance spectra for Bi(001) single crystal plane in 0.1, 0.02 and 0.003 M LiCl solutions in ethanol have been measured. It was found that reproducible experimental data for Bi electrode in ethanol solutions could be obtained at ac frequencies between 0.1 and 10 000 Hz and electrode potentials from -1.6 to -0.2 V (vs saturated calomel electrode). Outside this potential region, faradaic processes were detected. By fitting the experimental data to various equivalent circuits it was found that the Frumkin-Melik-Gaikazyan model yields good fit in almost the whole potential range studied. Using this model the dependences of "true" and adsorption capacitance as well as diffusion resistance on electrode potential have been obtained. The ionic charge due to the specific adsorption has been obtained using the mixed-electrolyte method for both electrode charge and electrode potential as the independent electric variables. The Gibbs energy of adsorption of Cl- ions has been calculated using a simple virial adsorption isotherm. It was found that the adsorption of Cl- anion increases in the order methanol < ethanol < propan-2-ol. It was found that on the Bi(001) plane the electrosorption valency has a constant value in the potential range studied. It was concluded that the formed effective surface dipole is significantly screened by the solvent molecules and the metal electron gas.

Examination of electrocatalysis in the anodic O 2 evolution reaction at Pt through evaluation of the adsorption behaviour of kinetically involved intermediate states

In regular heterogeneous catalytic reactions, evaluation of the adsorption behaviour of the ephemeral intermediates that participate kinetically in the main reaction pathway is often inaccessible experimentally. In electrocatalysis, on the other hand, electrochemical transient methods can provide such information. In the present paper, potential-relaxation transients are used to derive information on the electroactive, kinetically significant adsorbed intermediate states that are involved in the anodic O 2 evolution reaction (OER) at Pt electrodes. By means of such transients, digitally recorded over 5–6 decades of time from microseconds to seconds, the adsorption capacitance of the intermediate states in the reaction is evaluated as a function of potential over a range corresponding to appreciable current densities for O 2 evolution. Anodic O 2 evolution takes place at Pt, as at all other metal anodes, on an oxide film. A well-defined state of such a film must be established by a pre-conditioning programme to make meaningful and reproducible kinetic studies on the OER. The state of the oxide film is conveniently characterized by means of cyclic-voltammetry. The intermediate surface states in the reaction can be two or more oxidation states of Pt atoms in the oxide and OH or O species at the oxide’s surface. Two distinct types of adsorption behaviour are distinguished for potentials above and below ca . 1.85 V against the reversible H 2 electrode (RHE), and are related to the observed kinetics of the OER.