Influence of Electroconvection on Chronopotentiograms of an Anion-Exchange Membrane in Solutions of Weak Polybasic Acid Salts

Visualization of electroconvective (EC) vortices at the undulated surface of an AMX anion-exchange membrane (Astom, Osaka, Japan) was carried out in parallel with the measurement of chronopotentiograms. Weak polybasic acid salts, including 0.02 M solutions of tartaric (NaHT), phosphoric (NaH2PO4), and citric (NaH2Cit) acids salts, and NaCl were investigated. It was shown that, for a given current density normalized to the theoretical limiting current calculated by the Leveque equation (i/ilimtheor), EC vortex zone thickness, dEC, decreases in the order NaCl > NaHT > NaH2PO4 > NaH2Cit. This order is inverse to the increase in the intensity of proton generation in the membrane systems under study. The higher the intensity of proton generation, the lower the electroconvection. This is due to the fact that protons released into the depleted solution reduce the space charge density, which is the driver of EC. In all studied systems, a region in chronopotentiograms between the rapid growth of the potential drop and the attainment of its stationary values corresponds to the appearance of EC vortex clusters. The amplitude of the potential drop oscillations in the chronopotentiograms is proportional to the size of the observed vortex clusters.

γ-Ray-Induced Proton Generation in Polymers: Quantifiable Single-Component Fluorescent Ratiometric Chemosensor

<p>Detection of g-rays is of vital significance in various areas such as high-energy physics, nuclear medicine, national security and space exploration. However, most current spectrometry methods are typically based on ionization effects which are limited to electron counting techniques. Herein, we report an alternative, quantifiable g-ray chemosensor from a g-ray-induced proton generation process more sensitive to poly (methyl methacrylate) (PMMA) and polyvinyl chloride (PVC) by surveying a series of commercially available polymers. Accordingly, a pH-sensitive yet g-ray-stable fluorophore is designed, resulting in dramatic fluorescence shift from the blue (<i>l</i>_em = 460~480 nm) to the red region (<i>l</i>_em = 570~620 nm) after subjecting it to g-irradiation in PMMA or PVC films. A linear response of ratiometric fluorescence intensity (I_red/I_blue) to g-ray dosage in a wide range (80-4060 Gy) was established, which can be used as a visual dosimeter. Meanwhile, the discovery also opens new doors for proton-based radiation detection and chemistry. </p>

γ-Ray-Induced Proton Generation in Polymers: Quantifiable Single-Component Fluorescent Ratiometric Chemosensor

<p>Detection of g-rays is of vital significance in various areas such as high-energy physics, nuclear medicine, national security and space exploration. However, most current spectrometry methods are typically based on ionization effects which are limited to electron counting techniques. Herein, we report an alternative, quantifiable g-ray chemosensor from a g-ray-induced proton generation process more sensitive to poly (methyl methacrylate) (PMMA) and polyvinyl chloride (PVC) by surveying a series of commercially available polymers. Accordingly, a pH-sensitive yet g-ray-stable fluorophore is designed, resulting in dramatic fluorescence shift from the blue (<i>l</i>_em = 460~480 nm) to the red region (<i>l</i>_em = 570~620 nm) after subjecting it to g-irradiation in PMMA or PVC films. A linear response of ratiometric fluorescence intensity (I_red/I_blue) to g-ray dosage in a wide range (80-4060 Gy) was established, which can be used as a visual dosimeter. Meanwhile, the discovery also opens new doors for proton-based radiation detection and chemistry. </p>

Preventing Silica Scale Formation Using Hydroxide Ions Generated by Water Electrolysis

The reaction of silica with various cations in a solution and with hydroxide ions generated by water electrolysis was investigated as a means of preventing the formation of silica scales in geothermal binary power generation. Through batch and continuous experiments, it was found that all silica in the cathode phase of a reaction device could be removed if the necessary amounts of magnesium and calcium were present. This occurs because a silica-magnesium-calcium compound is produced via a polymerization reaction with cations in a solution and with hydroxide ions generated by electrolysis. Analysis by inductively coupled plasma and energy dispersive X-ray spectroscopy shows that this material has the formula 2CaO-5MgO-8SiO2-H2O, and thus is likely generated by the reaction proposed by Sheikholeslami et al. (2019). Increasing the current sent through the reaction solution subsequently produces calcium carbonate. This technique for the separation of silica and calcium from aqueous solutions can be operated continuously without channel clogging, which indicates the possibility of practical applications. However, overly high currents promote the migration of protons from the anode to cathode phases, which inhibits the formation of precipitates due to a neutralization reaction. The proposed method is an effective approach for removing silica from a solution in geothermal binary power generation; although, a means of suppressing the effects of proton generation will be necessary if the process is also to be used to remove calcium ions.