Weak magnetic field significantly enhances selenite removal kinetics by zero valent iron

Electrochemically generated magnetic forces at a disk-shaped ultramicroelectrode have been investigated in large, nonuniform magnetic fields. Two sources of magnetic force are simultaneously operative in the electrochemical experiment, both having a significant influence on molecular transport of the electrochemical reactants and products. First, the magnetohydrodynamic (MHD) force, FMHD, described by the Lorentz equation, arises from the diffusion of electrogenerated ions in the magnetic field. The magnitude of FMHD is dependent upon the strength and orientation of the magnetic field. Second, the gradient magnetic force, F∇B, which is proportional to the gradient of the magnetic field, arises from electrogeneration of paramagnetic molecules in a nonuniform magnetic field. F∇B is dependent on the magnetic field strength, its spatial gradient, and the magnetic properties of the redox-active molecules. F∇B and FMHD may be experimentally decoupled and investigated by variation of the field homogeneity and th...

Electrochemically Generated Magnetic Forces. Enhanced Transport of a Paramagnetic Redox Species in Large, Nonuniform Magnetic Fields

The sequestration of Se(IV) by zero-valent iron (ZVI) is strongly influenced by the coupled effects of aging ZVI and the presence of a weak magnetic field (WMF). ZVI aged at pH 6.0 with MES as buffer between 6 and 60 h gave nearly constant rates of Se(IV) removal with WMF but with rate constants that are 10- to 100-fold greater than without. XANES analysis showed that applying WMF changes the mechanism of Se(IV) removal by ZVI aged for 6–60 h from adsorption followed by reduction to direct reduction. The strong correlation between Se(IV) removal and Fe2+ release suggests direct reduction of Se(IV) to Se(0) by Fe0, in agreement with the XANES analysis. The numerical simulation of ZVI magnetization revealed that the WMF influence on Se(IV) sequestration is associated mainly with the ferromagnetism of ZVI and the paramagnetism of Fe2+. In the presence of the WMF, the Lorentz force gives rise to convection in the solution, which narrows the diffusion layer, and the field gradient force, which tends to move pa...

Coupled effects of aging and weak magnetic fields on sequestration of selenite by zero-valent iron.

http://sysweb.cinam.univ-mrs.fr/pro_perso/veesler/pdf/Eve.pdf

Usual and unusual crystallization from solution

One of the key reactions in photosynthesis is the conversion of excitation energy into a charge separated state in the reaction center, which contains 4 bacteriochlorophyls (Bchl), 2 bacteriopheophytins (H) and 2 quinone molecules arranged in two branches The primary electron donor, P, is formed by a pair of closely interacting Bchls. Upon excitation of P, electron transfer occurs from P to BA in ~3 ps, and from BA to HA in ~1 ps (1–3). The B and H pigments are also active in ultrafast (~100–200 fs) energy transfer to P (4–7). This rate is faster than predicted by Forster (dipole-dipole coupling) theory in the very weak limit, and also the observed weak temperature dependence can not be explained by this type of transfer(7). The energy transfer from B to P has therefore been suggested(6) to occur via the upper exciton level of P (~815–825 nm) in the strong coupling limit of Forster theory, or by direct orbital overlap between B and P (6–9).

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Three-Pulse Photon Echo Measurements on the Accessory Pigments in the Reaction Center of Rhodobacter sphaeroides

The effects of a high gradient magnetic field on the Ag+/Cu liquid−solid redox reaction were studied. A copper wire was placed on a sheet of chromatography paper wet with silver nitrate aqueous solution. At zero field silver dendrites grew uniformly around the wire. In the presence of a gradient magnetic field (ca. 380 T2m-1), the dendritic pattern changed drastically. The yield of silver metal increased by about 45%. These results are attributable to the convection of aqueous solution on the surface of the paper which is induced by the magnetic force on the paramagnetic copper ions generated in the reaction.

Effect of High Magnetic Field on the Silver Deposition from Its Aqueous Solution

The crystal growth of benzophenone was observed under high magnetic fields. In the presence of a magnetic field (8 T) the benzophenone crystal, which was diamagnetic, aligned in such a way that its crystal c-axis was perpendicular to the direction of the magnetic field. This phenomenon seemed attributable to the anisotropic diamagnetic susceptibility of the crystal.

The Effect of High Magnetic Field on the Crystal Growth of Benzophenone

Deposition of silver was observed under a high gradient magnetic field. When a copper wire was placed on a piece of filter paper which was wet with silver nitrate aqueous solution (0.5 mol dm−3), the deposition of silver grew uniformly around the wire at zero field. In the presence of the magnetic field (Bmax = 8 T), the area of the deposition at the center of the magnetic field decreased. Diffusion of ions generated in the reaction seems to be affected by the high gradient field.

Shin-ichi Watanabe

Papers

Effect of High Magnetic Field on the Silver Deposition from Its Aqueous Solution

The Effect of High Magnetic Field on the Crystal Growth of Benzophenone

The Effects of High Magnetic Field on the Deposition of Silver