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The behavior of alkaline earth metal cations (Mg2+ and Ca2+) and transition metal cations (Zn2+ and Cu2+) interacting with lambda-DNA-HindIII fragments ranging from 2,027 to 23,130 bp in Tris-borate-EDTA buffer solutions was investigated. The divalent counterions competed with Tris+ and Na+ for binding to polyion DNA, and the competition binding situations were investigated by measuring the reduction of the DNA mobility, by pulsed- or constant-field gel electrophoresis. The interaction of Mg2+ with DNA was intensively studied over a wide range of Mg2+ concentrations. In addition, we examined the competition binding as a function of ionic strength and DNA size. To compare valence effects, we studied Co(NH3)6(3+) interaction with DNA fragments under conditions similar to that of Mg2+. At relatively low Mg2+ concentration, the normalized titration curves of DNA mobility were well fit by Manning's two-variable counterion condensation (CC) theory. The agreement between the predicted value (total charge neutralization fraction theta) from Manning's CC theory and the data based on our measured DNA electrophoretic mobility reduction was consistent under our experimental conditions. In contrast to alkaline earth metal cations (Mg2+ and Ca2+), different binding behaviors were observed for the transition metal cations (Zn2+ and Cu2+). These differences highlight the usefulness of our reduced DNA electrophoretic mobility measurement approach to describing cation interactions with polyelectrolyte DNA.

Hydrogen sulfide (H 2 S) absorption and conversion to hydrogen and sulfur were carried out in an acidic aqueous vanadium dioxide (VO 2 ) þ solution coupled with indirect electrolysis. In this paper, the mechanisms of absorption and electrochemical reactions of the process are discussed. Parametric studies were conducted to determine the effects of operating parameters on absorption and electrochemical reactions. The results showed that the H 2 S absorption increased with temperature; greater than 90% of H 2 S absorption occurred at 50 °C. The absorption reaction was mass-transfer-limiting. In the electrolysis reaction, the current efficiency reached 97% at 45 °C after an extended electrolysis time. The optimal reaction conditions were at a proton concentration of 7 mol/kg of H 2 O in the electrolyte, (VO 2 ) þ concentration of lower than 0.65 mol/kg of H 2 O in the electrolyte, and (VO 2 ) þ concentration of higher than 0.55 mol/kg of H 2 O in the absorbent. Sulfur particles that are produced can be easily recovered. Some aspects related to design optimization of the absorption process and electrochemical reactor are also discussed.

A novel 3D hierarchical bifunctional catalytic electrode, MoS2/Ni3S2 nanorod arrays well-aligned on NF exhibited excellent electrocatalytic efficiency for hydrogen evolution reaction, oxygen evolution reaction and overall water splitting.

The sorption of Pb and Cd from aqueous solutions by spent Agaricus bisporus was investigated. The effects of contact time, pH, ionic medium, initial metal concentration, other metal ions presence and ligands were studied in batch experiments at 25°C. Maximum sorption for both metals was found to occur at an initial pH of around 5.5. The equilibrium process was well described by the Langmuir isotherm model, with maximum sorption capacities of 0.2345 and 0.1273 mmol g−1 for Pb and Cd respectively. Kinetic data followed the pseudo‐second‐order kinetic model. The presence of NaCl and NaClO4 caused a reduction in Cd sorption, while Pb sorption was not remarkably affected. The presence of other metals did not affect Pb removal, while the Cd removal was much reduced. HCl or EDTA solutions were able to desorb Cd from the spent Agaricus bisporus (SAB) completely, while an approximately 60% and 15% desorption yield was obtained for Pb when HCl 0.01 mol L−1 or EDTA 0.001 mol L−1 were used, respectively. The results of FTIR, SEM and EDX analysis indicated that other mechanisms, such as surface complexation and electrostatic interactions, must be involved in the metal sorption in addition to ion exchange. © 2012 Canadian Society for Chemical Engineering