Abatement of 1,2,4-Trichlorobencene by Wet Peroxide Oxidation Catalysed by Goethite and Enhanced by Visible LED Light at Neutral pH

There is significant environmental concern about chlorinated organic compounds (COCs) in wastewater, surface water, and groundwater due to their low biodegradability and high persistence. In this work, 1,2,4-trichlorobenzene (124-TCB) was selected as a model compound to study its abatement using wet peroxide oxidation at neutral pH with goethite as a heterogeneous catalyst, which was enhanced with visible monochromatic light-emitting diode (LED) light (470 nm). A systematic study of the main operating variables (oxidant and catalyst concentration and irradiance) was accomplished to investigate their influence in the abatement of 124-TCB in water. The reaction was carried out in a well-mixed reactor of glass irradiated by a visible LED light. The hydrogen peroxide concentration was tested from 0 to 18 mM, the goethite concentration within the range 0.1–1.0 g·L−1 and the irradiance from 0.10 to 0.24 W·cm−2 at neutral pH. It was found that this oxidation method is a very efficient technique to abate 124-TCB, reaching a pollutant conversion of 0.9 when using 0.1 g·L−1 of goethite, 18 mM of H2O2, and 0.24 of W·cm−2. Moreover, the system performance was evaluated using the photonic efficiency (ratio of the moles of 124-TCB abated and the moles of photons arriving at the reactor window). The maximum photonic efficiencies were obtained using the lowest lamp powers and moderate to high catalyst loads.

The research of the electrical properties of thick-film electrodes on piezoceramics in special conditions

The results of the study of the electrophysical properties of metal-ceramic compositions based on nickel boride depending on the composition, heat treatment conditions and after exposure to mixed reactor radiation (neutrons and γ-radiation) are presented. A method of metallization of piezoelectric ceramics based on materials developed using thick-film technology is proposed. The paper discusses the results of the study of physicochemical processes occurring during the heat treatment of films and their influence on the properties of piezoceramics. The advantages of thick-film technology, widely used in microelectronics, are well known, but the use of noble metals causes a number of serious production problems associated with their high cost, the need for waste management and reporting; Operational disadvantages include instability of properties (especially under mixed reactor irradiation conditions) due to the high diffusion coefficients of these metals (especially silver) and their leaching when soldering the leads. This work is devoted to the study of the electrophysical properties of pastes for thick-film metallization of piezoceramics, which do not contain extremely scarce and noble metals, burned in air, are not inferior in their operational parameters to pastes based on silver-palladium alloy and are intended to replace the latter.

Modeling of metallocene catalyzed propylene polymerization in fluidized bed reactors

A study was performed to improve the model for metallocene catalyzed polyolefin polymerization in fluidized bed reactor by adapting multi-scale modeling approach. Monomer concentration and reactor temperature was predicted using kinetic model of polypropylene homopolymerization coupled with well mixed reactor models of fluidized bed reactor. Well mixed model typically used for Ziegler-Nata was selected as supported homogeneous metallocene exhibited heterogeneous property similar to ZN catalyst. Result of simulation showed that model was able to predict reaction temperature accurate with around 3% over-prediction of reactor temperature, which is more accurate than previous model. Model predicted decrease in final monomer concentration from 0.9929 mol/s to 0.986 mol/s when initial reactor was raised from 25C to 75C.

The effect of mixing on fermentation of primary solids, glycerol, and biodiesel waste

In this study, the effect of mixing on volatile fatty acid (VFA) production and composition was investigated through running five identical bench-scale reactors that were filled with primary solid and dosed with either pure glycerol or biodiesel waste. Experimental results revealed that there was an inverse correlation between the mixing intensity and the VFA production. The total VFA production in the un-mixed reactor was 9,787 ± 3,601 mg COD/L, whereas in the reactor mixed at 100 rpm this dropped to 3,927 ± 1,175 mg COD/L, while both types of reactor were dosed with pure glycerol at the beginning of each cycle to reach the initial concentration of 1,000 mg/L (1,217 mg COD/L). Propionic acid was the dominant VFA in all the reactors except the reactor mixed at 30 rpm. It is hypothesized that low mixing facilitated hydrogen transfer between obligate hydrogen producing acetogens (OHPA) and hydrogen consuming acidogens in these non-methanogenic reactors. Also, in a narrower range of mixing (0 or 7 rpm), the total VFA production in biodiesel waste-fed reactors was considerably higher than that of pure glycerol-fed reactors.

Sulfide emissions in sewer networks: focus on liquid to gas mass transfer coefficient

H2S emission dynamics in sewers are conditioned by the mass transfer coefficient at the interface. This work aims at measuring the variation of the mass transfer coefficient with the hydraulic characteristics, with the objective of estimating H2S emission in gravity pipes, and collecting data to establish models independent of the system geometry. The ratio between the H2S and O2 mass transfer coefficient was assessed in an 8 L mixed reactor under different experimental conditions. Then, oxygen mass transfer measurements were performed in a 10 m long gravity pipe. The following ranges of experimental conditions were investigated: velocity flow [0–0.61 m.s−1], Reynolds number [0–23,333]. The hydrodynamic parameters at the liquid/gas interface were calculated by computational fluid dynamics (CFD). In the laboratory-scale reactor, the O2 mass transfer coefficient was found to depend on the stirring rate (rph) as follows: KL,O2 = 0.016 + 0.025 N3.85. A KL,H2S/KL,O2 ratio of 0.64 ± 0.24 was found, in accordance with previously published data. CFD results helped in refining this correlation: the mass transfer coefficient depends on the local interface velocity ui (m.h−1): KL,O2 = 0.016 + 1.02 × 10−5ui3.85 In the gravity pipe device, KL,O2 also exponentially increased with the mean flow velocity. These trends were found to be consistent with the increasing level of turbulence.