In this study, the mass transfer and reaction kinetics of soybean oil epoxidation using concentrated hydrogen peroxide in a formic acidautocatalyzed reaction system were studied in detail. Studying the mass transfer of formic acid showed that the influence of reactant diffusion near the interface is eliminated when the stirring rate is > 120 rpm in a double-stirred cell, and the mass transfer rate decreases greatly with the conversion of double bonds and a decrease of reaction temperature. A temperature increase has little impact on the equilibrium of formic acid in the oil/water system, while an increase of epoxidized soybean oil significantly increases the value of the partition coefficient of formic acid. Another important aspect in the kinetic study is the decomposition of performic acid, which can cause the reduction of H 2 O 2 and formic acid during the reaction. Finally, a biphasic model, which considers all reactions in oil and aqueous phases, the equilibrium and mass transfer of reagents and products between the phases, and the evolution of proton concentrations with time, was developed to describe the epoxidation process.

Silver nanoparticles (Ag NPs) modified with sodium 2-mercaptoethanesulfonate (mesna) exhibit strong surface-enhanced Raman scattering (SERS). Their specific and strong interaction with heavy metal ions led to a labelfree assay for Hg(II). The covalent bond formed between mercury and sulfur is stronger than the one between silver and sulfur and thus prevents the adsorption of mesna on the surface of Ag NPs. This results in a decrease of the intensity of SERS in the presence of Hg(II) ions. The Raman peak at 795 cm −1 can be used for quantification. The effect of the concentration of mesna, the concentration of sodium chloride, incubation time and pH value on SERS were optimized. Under the optimal conditions, the intensity of SERS decreases with increasing concentration of Hg(II). The decrease is linear in the 0.01 and 2 μmol L −1 concentration range, with a correlation coefficient (R 2 ) of 0.996 and detection limit (S/N03) is 0.0024 μmol L −1 . The method was successfully applied to the determination of the Hg(II) in spiked water samples.

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A novel reactor for exothermic heterogeneous reaction systems was developed and used in a vegetable oil epoxidation process. When hydrodynamic cavitation is coupled with a static mixer, both mass and heat transfer in the reactor can be intensified effectively. The Sauter mean diameter of water/oil dispersion was 8.90 μm under hydrodynamic cavitation conditions with a relatively low inlet pressure (2.5 bar) as compared to 60.33 μm for conventional stirring approach at 500 rpm. The epoxidation temperature variation was controlled within ±1 °C even when the H2O2 was added at once, whereas the temperature rise was up to 19 °C in a stirred-tank reactor. The use of this reactor results in decreased reaction time and a simpler and safer process, with final products having quality similar to that obtained in a traditional process.

The degradation of methylene blue (MB) using an upgraded dielectric barrier discharge (DBD) plasma reactor was investigated in this paper. Air plasma was generated in the glass bead packed bed in the reactor, which was propagated into MB solution through a microporous diffuser plate. Microdischarge phenomenon can be observed on the interface of MB solution and the diffuser plate, where plasma active species were generated. The effects of air flow rate, initial solution concentration, initial solution pH, and initial solution conductivity on MB degradation were examined. Experimental results indicated that the proposed plasma reactor was effective for MB degradation. No obvious change in MB degradation efficiency was obtained for solution with various initial pH and conductivities, which suggested the potential of the reactor in actual wastewater treatment. The possible mechanism of the generation of plasma active species for MB degradation was proposed. In addition, the total organic carbon removal and chemical oxidation demand removal after 30 min treatment were 38.5% and 48.3%, which was higher than that obtained by ozone. The energy yield for MB degradation reached up to 9.3 g/kWh. Finally, a possible degradation pathway of MB solution was proposed.agents. As a promising plasma discharge mode, non-thermal plasma (NTP) technique can be utilized to degrade pollutants in wastewater at atmospheric pressure and room temperature with lower input energy than thermal plasma [8]. The typical NTP discharge in, and in contact with, liquids can be divided into three parts, namely, direct discharge in liquids, discharge in gas phase over a liquid, and discharge in multiphase environment such as bubbles or foams inside liquids [7].For discharge in gas phase over a liquid, the gas breakdown occurs in the gap between liquid and high voltage plate. Thus, plasma active species and high energy electrons are generated and then transferred into liquids to react with organic compound [9,10]. The efficiency of NTP reactors is mainly relevant to the efficiency of mass transfer between gas and liquid phases. A packed water jet bed plasma reactor was put forward by Foster et al. [11] to maximize the plasma contact area with the water. The parallel operation of multiple plasma jets or packed bed arrays of water streams are potential solutions to the scale-up problem. Tichonovas et al. [4] and Li et al. [12] proposed a dielectric barrier discharge (DBD) reactor and a gas-liquid plasma reactor, respectively. In their reactors, the gas was sent into the discharge zone, with plasma generated and dispersed into liquid phase by porous ceramic diffusers. This process can increase the efficiency of mass transfer of active species into liquid, resulting in enhanced degradation efficiency. However, the active species diffused into liquid are mostly ozone since the other active radicals dissipate during diffusion process due to their short lifetime [13]. Thus, the mineralization of contaminants in wastewater is difficult to achieve. Therefore, it ...