Accelerated Oxidative Degradation of Phosphonium-Type Ionic Liquid with l-Prolinate Anion: Degradation Mechanism and CO2 Separation Performance.

Amino acid ionic liquids (AAILs) are regarded as green alternatives to existing CO2-sorptive materials because amino acids are readily available from renewable sources in large quantities. For widespread applications of AAILs, including direct air capture, the relationship between the stability of AAILs, especially toward O2, and the CO2 separation performance is of particular importance. In the present study, the accelerated oxidative degradation of tetra-n-butylphosphonium l-prolinate ([P4444][Pro]), a model AAIL that has been widely investigated as a CO2-chemsorptive IL, is performed using a flow-type reactor system. Upon heating at 120-150 °C and O2 gas bubbling to [P4444][Pro], both the cationic and anionic parts undergo oxidative degradation. The kinetic evaluation of the oxidative degradation of [P4444][Pro] is performed by tracing the decrease in the [Pro]- concentration. Supported IL membranes composed of degraded [P4444][Pro] are fabricated, and the membranes retain CO2 permeability and CO2/N2 selectivity values in spite of the partial degradation of [P4444][Pro].

Two-step droplet formation in monodisperse nanodroplet generation in quenched hydrothermal solution as revealed by spontaneous transformation of nanodroplets to swollen micelles in octane­in­water nanoemulsions.

HYPOTHESIS: Monodisperse nanodroplet generation in quenched hydrothermal solution (MAGIQ) is a newly developed bottom-up process for preparing nanoemulsions. In this process, homogeneous solutions of oil in supercritical water are quenched by adding cold water containing a surfactant to induce rapid phase-separation, during which oil molecules self-assemble to form nano-sized oil droplets. The droplet size in MAGIQ is known to be influenced by the interplay of the phase-separation dynamics, coalescence kinetics of the droplets, and adsorption kinetics of the surfactant on the droplet surface; however, the primary stages of the droplet formation are still elusive. EXPERIMENTS: Octane­in­water nanoemulsions containing 0.5, 1, and 3 vol% octane were prepared by the MAGIQ method. Their ripening was studied by dynamic light scattering, and the phase diagram was established. FINDINGS: The nanoemulsions containing 0.5 and 1 vol% octane transformed to thermodynamically stable microemulsions containing swollen micelles, whereas the nanoemulsion containing 3 vol% octane underwent Ostwald ripening. The initial formation of the nano-sized droplets in the former was ascribed to a unique mechanism of droplet formation in MAGIQ-the droplets are first formed by the phase separation of homogeneous binary solutions of oil in supercritical water and then stabilized upon surfactant adsorption.

Capacity for survival in global warming: Adaptation of mesophiles to the temperature upper limit.

The Intergovernmental Panel on Climate Change recommends keeping the increase in temperature to less than a two-degree increase by the end of the century, but the direct impact of global warming on ecosystems including microbes has not been investigated. Here we performed thermal adaptation of two species and three strains of mesophilic microbes for improvement of the survival upper limit of temperature, and the improvement was evaluated by a newly developed method. To understand the limitation and variation of thermal adaptation, experiments with mutators and by multiple cultures were performed. The results of experiments including genome sequencing and analysis of the characteristics of mutants suggest that these microbes bear a genomic potential to endure a 2-3°C rise in temperature but possess a limited variation of strategies for thermal adaptation.

Application of Quartz Crystal Microbalance as a Tool for Detergency Evaluation of Fatty Acid Contamination in Aqueous Systems.

Removal process of a fatty acid from four substrates was monitored using a quartz crystal microbalance (QCM). Model substrates included carbon, silica, and gold sputtered electrodes and a polymer film prepared on a gold sputtered electrode. Stearic acid (SA), a model solid oily contaminant, was deposited on the substrates as an ultra-thin layer using the Langmuir-Blodgett (LB) technique. Cleaning tests of the SA-LB films were performed in aqueous solutions containing sodium chloride (NaCl), sodium hydroxide (NaOH), and/or sodium dodecyl sulfate (SDS). The removal efficiency was calculated from the QCM frequency vs. time curve obtained during the cleaning process. The neutralization by NaOH was effective for removing the SA-LB film from all substrates, although the reaction was slow. In the absence of NaOH, minor amounts of the SA-LB film was removed from the substrates, with the exception of silica, even in the SDS solution. To increase the removal efficiency of the SA-LB film in the absence of NaOH, the SA-LB film deposited on the substrates was exposed to atmospheric-pressure plasma before the cleaning process. This treatment promoted the removal of the film in the NaCl and/or SDS solutions, which we interpreted to be due to the hydrophilization of both the surfaces of the substrates and the SA-LB film.

Introduction of Atmospheric Pressure Plasma to Aqueous Detergent Processes.

The effects of exposure of polymer surfaces to atmospheric pressure plasma (APP) on detergency were investigated from the viewpoint of pretreatment to cleaning in aqueous systems using three PET substrates: film, mesh, and fabric. The PET substrates were soiled with stearic acid as a model oily contaminant, and were treated with the APP jet immediately before cleaning. Stir washing in aqueous solutions with and without alkali or anionic surfactant was performed, and then the detergency was evaluated from the microscopic image analysis or surface reflectance measurement. For all PET samples and detergent solutions, APP exposure was found to promote the removal of stearic acid. Contact angle measurements showed that APP exposure enhanced the hydrophilicity of PET and stearic acid. The increase in the surface oxygen concentration on PET and stearic acid due to the APP exposure was also observed by XPS analysis. The simultaneous oxidation of the PET substrate and stearic acid soil by the APP pretreatment resulted in detergency improvement via surface hydrophilization. Furthermore, microscopic observations suggested that the collapse of crystallized stearic acid deposited on the PET substrate by APP heating facilitated its removal. In situ detergency evaluation by a quartz crystal microbalance technique confirmed that the removal of stearic acid from the PET substrate was promoted by the APP exposure. The experimental findings of this study demonstrate the effectiveness of the APP exposure before cleaning in aqueous solutions.