Electrochemical Investigation of Heavy Metal Ion Transfer Across the Water/1,2‐Dichloroethane Interface Assisted by 9‐Ethyl‐3‐Carbazolecarboxaldehyde‐Thiosemicarbazone

The transfer of heavy metal ions across the polarized water/1,2‐dichloroethane (1,2‐DCE) interface assisted by 9‐ethyl‐3‐carbazolecarboxaldehyde‐thiosemicarbazone (ECCAT) in the 1,2‐DCE phase has been studied by cyclic voltammetry. Voltammetric waves of Pb(II) and Cd(II) ions were reversible and quasi‐reversible, respectively, whereas that of Hg(II) and Zn(II) ion were irreversible. The voltammogram of Cu(II) ion showed a two‐step wave, however the nature of the transfer could not be satisfactorily evaluated by analyzing the cyclic voltammetric data. When Ni(II) and Co(II) was used no peak was visible under the experimental conditions used in this study. The dependence of the half‐wave potentials of Pb(II) and Cd(II) ions on the ligand concentration reveals that their ion‐transfer is assisted by the formation of 1:3 metal‐ECCAT complex in 1,2‐DCE. The over‐all association constants of [Pb(ECCAT)₃]²⁺ and [Cd(ECCAT)₃]²⁺ complexes in DCE‐phase have been determined to be log β =14.03 and log β =15.44, respectively.     

Transport of Acids through Polyether-Sulfone Anion-Exchange Membrane

Diffusion dialysis of sulfuric acid and hydrochloric acid into water with a polyether-sulfone anion-exchange membrane was studied. Transport of sulfuric acid and hydrochloric acid through the membrane has been quantified by diffusion coefficients and mass transfer coefficients. The mass transfer coefficients were investigated as a function of the rotational speed of the stirring rate of both sides of the membrane and with different pH ranges. It was observed that the diffusion dialysis seems to be dependent on the rotational speed of the stirrer; in contrast, the membrane mass transfer coefficients are independent of rotational speed, but they are slightly affected by the initial acid concentration in donor phase. Copyright 2001 Academic Press.     

Removal of phenol from aqueous phase by using neutralized red mud

The objective of this study is to remove the phenol from aqueous solution by using the neutralized red mud in batch adsorption technique. The study was carried out as functions of contact time, pH, initial phenol concentration, red mud dosage and effect of salt addition. The experiments demonstrated that maximum phenol removal was obtained in a wide pH range of 1-9 and it takes 10 h to attain equilibrium. The adsorption data was analyzed using the Langmuir and the Freundlich isotherm models and it was found that the Freundlich isotherm model represented the measured sorption data well. The influence of addition of salt on phenol removal depends on the relative affinity of the anions for the red mud surface and the relative concentrations of the anions.     

Hydrogen Evolution at Liquid–Liquid Interfaces

Blowing bubbles : Hydrogen evolution by proton reduction with [(C₅Me₅)₂Fe] occurs at a soft interface between water and 1,2‐dichloroethane (DCE). The reaction proceeds by proton transfer assisted by [(C₅Me₅)₂Fe] across the water–DCE interface with subsequent proton reduction in DCE. The interface essentially acts as a proton pump, allowing hydrogen evolution by directly using the aqueous proton.

     

The Effect of pH and Temperature on the Sorption of Zinc(II), Cadmium(II), and Aluminum(III) onto New Metal-Ligand Complexes of Sporopollenin

Sorption of metal ions from aqueous solution onto metal-ligand complexes of sporopollenin derivatives has been measured as a function of pH at several temperatures between 20 and 50°C. Novel metal-ligand exchange resins possessing oxime and carboxylic acid sidearm functionality were prepared through the reaction of diaminosporopollenin with dichloro-antiglyoxime and bromoacetic acid. The pH dependencies and sorption isotherms of various metal ions such as Zn(II), Cd(II), and Al(III) on the resin were investigated from aqueous solution. The sorption behavior of these metal-ligand complexes of sporopollenin derivatives and the possibilities of selectively removing and recovering heavy metals are explained on the basis of their chemical nature and complex properties and the results are interpreted in terms of the variations of pH.     

Biofuel Cell Based on Anode and Cathode Modified by Glucose Oxidase

A single compartment biofuel cell (BFC) based on an anode and a cathode powered by the same fuel glucose is reported. Glucose oxidase (GOx) from Aspergillus niger was applied as a glucose consuming biocatalyst for both anode and cathode of the BFC. The 5‐amino‐1,10‐phenanthroline modified graphite rod electrode (GRE) with cross‐linked GOx was used as the bioanode, and the GRE with co‐immobilised horseradish peroxidase and GOx was exploited as the biocathode of the BFC. The open‐circuit voltage of the designed BFC exceeded 450 mV and a maximal power density of 3.5 µW/cm² was registered at a cell voltage of 300 mV.     

Investigation of the Lipophilicity of 2-Benzoylpyridine-Thiosemicarbazone Based on the Ion Transfer across the Liquid/Liquid Interface

The ion transfer reaction of 2-benzoylpyridine-thiosemicarbazone (HL), which has antimicrobial and antifungal properties and anticancer activity, has been studied to determine its lipophilicity by cyclic voltammetry at the water/1,2-dichloroethane (1,2-DCE) interface. The physicochemical parameters such as standard partition coefficient (lgP_I) and the standard Gibbs energy of transfer ( ) of the protonated form of the ligand were measured as a function of pH in aqueous phase. The protonated form of the ligand exhibited reversible or quasi-reversible voltammograms at the 1,2-DCE in the range of pH 1–5. The protonation constants of the ligand, pK_a1 and pK_a2, were determined spectrophotometrically and were found to be 12.14 and 3.24, respectively. The standard Gibbs energy of transfer ( ) and the partition coefficient of neutral species (lgP_N) were also determined by the shake-flask method. The standard Gibbs energy of transfer of this compound across the water/1,2-DCE interface was evaluated as the quantitative measure of its lipophilicity. The difference between lgP_I and lgP_N was related to the degree of charge delocalization and was used to evaluate qualitatively the lipophilicity of the ligand.     

Aromatic monoterpenoid glycosides from Cruciata taurica

Two new aromatic monoterpenoid glycosides, cruciaside A (2,5-O-beta-D-diglucopyranosyl-3-hydroxy-p-cymene) (1) and cruciaside B (5-O-beta-D-glucopyranosyl-2,3-dihydroxy-p-cymene) (2), were isolated from aerial parts of Cruciata taurica. The structures of the new compounds were determined by spectral and chemical methods. The new compounds seem to be promising as taxonomic markers for C. taurica.     

157-nm laser micromachining of N-BK7 glass and replication for microcontact printing

We report etch-rate and probe-beam-deflection studies of N-BK7 glass ablated using a 157-nm F₂ laser. It is found that controllable material removal at the nanometre level is possible above an ablation threshold of 250 mJ cm^-2. Contact mask printing shows well-defined features can be micromachined in this glass with sub-micron resolution capability. Micro-features produced in this way have been replicated by polydimethylsiloxane (PDMS) moulding and the stamps used to print arrays of fluorescent molecules with sub-micron fidelity. PACS 45.55.Lt; 52.38.Mf; 87.80.Mj; 42.70.Ce