Enhanced generation of active oxygen species induced by O3 fine bubble formation and its application to organic compound degradation.

By using O3 fine bubbles that promote the mass transfer of O3 to the liquid phase and the conversion of the dissolved O3 into active oxygen species with a high oxidation potential, an improved liquid-phase oxidation technique was developed to accelerate the degradation of an organic compound at a constant O3 flow rate. By the use of a dielectric-barrier-discharge reactor, O2 was converted into O3 at an O2 flow rate of 0.56 mmol/(L·min), with 5 mol% O2-to-O3 conversion. Using a self-supporting bubble generator, O3 bubbles with an average diameter (dbbl) of 50 µm were continuously supplied into a solution in TBA (OH• scavenger) at 303 K, and the TBA being degraded. For comparison, O3 bubbles with dbbl values of 200-5000 µm were obtained using a dispersing-type generator. It was found that the minimization of bubble diameter accelerated both O3 dissolution, as a consequence of the increase in the gas-liquid interfacial area and the residence time of the bubbles, and enhanced OH• generation, because of the increase in contact probability between dissolved O3 and OH- at the minute gas-liquid interfaces, caused by the accumulation of OH- around the fine bubble surfaces. To ascertain the influence on organic compound degradation of the improved oxidation potential, bisphenol A, as a model compound, was degraded by O3 bubble injection at different dbbl values. Sequentially, the high OH• selectivity obtained by minimizing the bubble diameter can effectively achieve the rapid degradation of organic compounds and intermediates under a constant O3 flow rate.

Evidence of transport of styrene oligomers originated from polystyrene plastic to oceans by runoff.

This study demonstrates for the first time that styrene oligomers (SOs), which are indicators of polystyrene (PS) plastic contamination in the environment, are transported from land to the ocean. Samples of sand and seawater were taken from the coastline of the Tokyo Bay over the past four years, and all samples of both sand and seawater were found to contain SOs such as styrene monomer (SM), styrene dimers (SD), and styrene trimers (ST), with the concentration distributions of these being in the order of ST > SD > SM. The concentrations of these SOs are linearly proportional to monthly precipitation. These results indicate that various land-based SOs sources are connected with the estuary, a substantial amount of which are transported into Tokyo Bay through runoff as overland flow. As a result, runoff by precipitation is a potential transport pathway of land-based SOs sources. This finding is of interest in terms of both the extent of PS plastic pollution and the transport of SOs to the ocean. CAPSULE ABSTRACT: The assessment of the transport of styrene oligomers (SOs) in the coastal environment is performed.

Mechanistic and exploratory investigations into the synthesis of 1,3,5-triaroylbenzenes from 1-aryl-2-propyn-1-ones and 1,3,5-triacetylbenzene from 4-methoxy-3-buten-2-one by cyclotrimerization in hot water in the absence of added acid or base.

Neat 1-phenyl- and 1-(p-tolyl)-2-propyn-1-ones (1 and 1', respectively) were heated in water without any additive at 150 °C for 2 h to give 1,3,5-tribenzoyl- and 1,3,5-tri-(p-toluoyl)benzenes (2 and 2', respectively) in 74 and 52% yields, respectively. The crossed reactions of 1 with the enolate of p-toluoylacetaldehyde (3') and 1' with the enolate of benzoylacetaldehyde (3) were carried out to give unsymmetrically substituted 1-toluoyl-3,5-dibenzoylbenzene (Ph2Tol) and 1,3-ditoluoyl-5-benzoylbenzene (PhTol2), respectively, corroborating the previously proposed reaction mechanism in which 3 and 3' that are formed by rate-determining nucleophilic attack of HO(-) on 1 and 1' or its conjugate acids formed by subsequent protonation would serve as a common intermediate for the formation of 2, 2' and the acetophenone derivatives as byproducts. When 4-methoxy-3-buten-2-one (4) was heated in hot pure water without any additive at 150 °C for 30 min, 1,3,5-triacetylbenzene (5) was obtained in an isolated yield of 77% just by removing water by filtering the crystalline product from the cooled reaction mixture. The reaction did not take place in the absence of water. Slow decompositions of 5 in water set in at the temperature of 300 °C for 30 min.

Evaluation of the thermal effect on separation selectivity in anion-exchange processes using superheated water ion-exchange chromatography.

The thermal effect on retention and separation selectivity of inorganic anions and aromatic sulfonate ions in anion-exchange chromatography is studied on a quaternized styrene-divinylbenzene copolymer anion-exchange column in the temperature range of 40-120 °C using superheated water chromatography. The selectivity coefficient for a pair of identically charged anions approaches unity as temperature increases provided the ions have the same effective size, such that the retention of an analyte ion decreases with an increase in temperature when the analyte ion has stronger affinity for the ion-exchanger than that of the eluent counterion, whereas it increases when it has weaker affinity. The change in anion-exchange selectivity with temperature observed with superheated water chromatography has been discussed on the basis of the effect of temperature on hydration of the ions. At elevated temperatures, especially in superheated water, the electrostatic interaction or association of the ions with the fixed ion in the resin phase becomes a predominant factor resulting in a different separation selectivity from that obtained at ambient temperature.

One-pot synthesis of 1,3,5-tribenzoylbenzenes by three consecutive Michael addition reactions of 1-phenyl-2-propyn-1-ones in pressurized hot water in the absence of added catalysts.

Cyclotrimerization of 1-phenyl-2-propyn-1-one in pressurized hot water gave 1,3,5-tribenzoylbenzene in one pot in 65 % yield after 7 min at 200 °C, or in 74 % yield after 60 min at 150 °C. The reaction did not take place in the absence of water, and added base promoted the reaction at 250 °C, suggesting a mechanism of three-consecutive Michael addition reactions. The reaction rates increased with temperature, but the yield of 1,3,5-tribenzoylbenzene decreased at the expense of formation of acetophenone as a side product at higher temperatures. p-Methyl and p-chloro-substituents on the phenyl ring retarded and enhanced the reaction, respectively. A mechanism involving the enol of benzoylacetaldehyde at a branching point of the pathway leading to 1,3,5-tribenzoylbenzene and acetophenone was suggested.