Unusual Effect of the Magnetic Field Component of the Microwave Radiation on Aqueous Electrolyte Solutions

Abstract

The heating characteristics of aqueous electrolyte solutions (NaCl, KCl, CaCl2, NaBF4, and NaBr) of varying concentrations in ultrapure water by 2.45 GHz microwave radiation from a single-mode resonance microwave device and a semiconductor microwave generator were examined under conditions where the electric field (E-field) was dominant and where the magnetic field (H-field) dominated. Although magnetic field heating is not generally used in microwave chemistry, the electrolyte solutions were heated almost entirely by the microwaves' H-field. The heating rates under H-field irradiation at the higher concentrations of electrolytes (0.125 M to 0.50 M) exceeded the rates under E-field irradiation. This inversion phenomenon in heating is described in terms of the penetration depth of the microwaves. On the other hand, the action of the microwave radiation on ethylene glycol containing an electrolyte differed from that observed for water under E-field and H-field conditions.

Review on Microwave-Matter Interaction Fundamentals and Efficient Microwave-Associated Heating Strategies

“…It was reported that heating rates of the electrolyte solutions (NaCl, KCl, CaCl 2 , NaBF 4 , and NaBr) were far more significant than that of same-volume ultrapure water when they are heated in the same microwave conditions [42]. For the aqueous electrolyte solutions, both dipolar polarization and conductive mechanisms contribute to the heating effect.…”

“…Magnetic resonance losses are primarily induced by domain wall resonance and electron spin resonance [42,46,57]. In the literature, residual losses were also used to represent the losses originating from various magnetic relaxations and resonances which occurs mainly in two ways, as rotational resonance and as domain wall resonance [55,58].…”

Microwave Synthesis, Extraction, Improvement and Degradation in Oil Chemistry

“…Therefore, emulsion size is an important factor that determines the heating efficiency by microwave. On the other hand, the microwave-heating rate can be remarkably changed by the addition of inorganic ions as impurities 10 .…”

“…The de-emulsification process was prevented by higher pH and salt concentrations; these conditions contribute to an increase in solution conductivity. Therefore, since the penetration depth of microwave fell, heating efficiency decreased 10 .…”

Utilization of the microwave electric or magnetic field in the synthesis of monometallic and bimetallic nanoparticles

“…This effect has been explained with a Joule loss resulting from an eddy current induced by the microwave's alternating magnetic eld. 24 In this paper, the interference of the polyol synthesis of silver-containing nanoparticles by the microwave E-eld and H-eld was investigated. To investigate the eld effects the synthesis has been performed in solutions containing Ag ions and additionally diamagnetic or paramagnetic (Ni 2+ ) ions.…”