Photocatalytic reactors for treating water pollution with solar illumination. III: a simplified analysis for recirculating reactors

A solar photoreactor operated in the batch, recirculating mode is analyzed in terms of very simple observable variables such as the impinging photon flux, the incident area, the initial concentration, the flow rate, the reactor volume and a property defined as the Observed Photonic Efficiency. The proposed equipment is made of a tubular reactor, a tank, a pump and the connecting pipes. The analysis is formulated in terms of the photon input corresponding to an equivalent batch system that is derived as a new reaction coordinate for photoreactions. Employing several plausible approximations, the pollutant concentration evolution in the tank is cast in terms of very simple analytical solutions.Process photonic efficiencies are defined for the system operation and calculated with respect to the maximum achievable yield corresponding to the differential operation of the solar recirculating reactor.     

The photocatalytic destruction of the cyanotoxin, nodularin using TiO2

Titanium dioxide (TiO₂) photocatalysis has been used to initiate the destruction of nodularin, a natural hepatotoxin produced by cyanobacteria. The destruction process was monitored using liquid chromatography–mass spectrometry analysis which has also enabled the identification of a number of the photocatalytic decomposition products. The reduction in toxicity following photocatalytic treatment was evaluated using protein phosphatase inhibition assay, which demonstrated that the destruction of nodularin was paralleled by an elimination of toxicity.     

Premixed flame propagation in a free straight vortex

The paper presents experimental and numerical investigations of the Combustion Induced Vortex Breakdown (CIVB) in a free straight turbulent vortex. The velocity field was measured using the Laser-Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV) methods. The flame propagation is estimated from analysis of pictures taken by a high speed camera. Numerical simulations have been performed using the Large Eddy Simulations (LES). Two different types of the flame propagation along the vortex were identified depending on the equivalence ratio and the swirl number. It was shown that the Combustion Induced Vortex Breakdown takes place if the swirl number exceeds a certain threshold at a constant value of the equivalence ratio. LES simulations confirmed the fact that the CIVB appears in the vortex configuration considered. Detailed analysis of the LES data allows to estimate contributions of different physical mechanisms to the CIVB.     

MTBE adsorption on alternative adsorbents and packed bed adsorber performance

Widespread use of the fuel additive methyl tertiary-butyl ether (MTBE) has led to frequent MTBE detections in North American and European drinking water sources. The overall objective of this research was to evaluate the effectiveness of a silicalite zeolite, a carbonaceous resin, and a coconut-shell-based granular activated carbon (GAC) for the removal of MTBE from water. Isotherm and short bed adsorber tests were conducted in ultrapure water and river water to obtain parameters describing MTBE adsorption equilibria and kinetics and to quantify the effect of natural organic matter (NOM) on MTBE adsorption. Both the silicalite zeolite and the carbonaceous resin exhibited larger MTBE adsorption uptakes than the tested GAC. Surface diffusion coefficients describing intraparticle MTBE mass transfer rates were largest for the GAC and smallest for the carbonaceous resin. Pilot tests were conducted to verify MTBE breakthrough curve predictions obtained with the homogeneous surface diffusion model and to evaluate the effect of NOM preloading on packed bed adsorber performance. Results showed that GAC was the most cost-competitive adsorbent when considering adsorbent usage rate only; however, the useful life of an adsorber containing silicalite zeolite was predicted to be approximately 5-6 times longer than that of an equally sized adsorber containing GAC. Pilot column results also showed that NOM preloading did not impair the MTBE removal efficiency of the silicalite zeolite. Thus, it may be possible to regenerate spent silicalite with less energy-intensive methods than those required to regenerate GAC.     

Model projections for household energy use in developing countries

The residential sector plays an important role in the energy system of developing countries. In this paper we introduce a bottom up simulation model for household energy use. The model describes energy demand for several end-use functions based on a set of physical drivers, such as floor space and heating degree days. The model also recognizes different population groups: i.e. urban and rural households, each distinguishing five income quintiles. The model is applied to analyze possible future developments of residential energy use in five developing world regions: India, China, South East Asia, South Africa and Brazil. We find that in each of these regions cooking is currently the main end-use function, but that other functions, such as space heating, cooling and appliances become more important. At the same time, energy consumption slowly shifts towards modern fuels. The model also shows that climate policy can reduce residential energy emissions, but could also slow down the energy transition away from traditional fuels in low income classes.     

一种连续分离纳米颗粒的确定性横向迁移装置

确定性横向迁移（DLD）是一种利用微米尺寸障碍物阵列对含有颗粒或分子混合物的液流在横跨流体方向上进行连续分离的技术。利用DLD原理,本文介绍了一种连续分离纳米颗粒混合物（颗粒半径可小到70nm）的装置。该装置根据颗粒的半径大小,可在几秒钟内完成分离。文中还研究了装置的几何形状和分离参数之间的关系。这项分离技术最终将被应用到蛋白质分子分离方面。     

Construction and characterisation of a modular microfluidic system: coupling magnetic capture and electrochemical detection

This work presents the fabrication and characterisation of a versatile lab-on-a-chip system that combines magnetic capture and electrochemical detection. The system comprises a silicon chip featuring a series of microband electrodes, a PDMS gasket that incorporates the microfluidic channels, and a polycarbonate base where permanent magnets are hosted; these parts are designed to fit so that wire bonding and encapsulation are avoided. This system can perform bioassays over the surface of magnetic beads and uses only 50 μL of bead suspension per assay. Following detection, captured beads are released simply by sliding a thin iron plate between the magnets and the chip. Particles are captured upstream from the detector and we demonstrate how to take further advantage of the system fluidics to determine enzyme activities or concentrations, as flow velocity can be adjusted to the rate of the reactions under study. We used magnetic particles containing β-galactosidase and monitored the enzyme activity amperometrically by the oxidation of 4-aminophenol, enzymatically produced from 4-aminophenyl-β-d-galactopyranoside. The system is able to detect the presence of enzyme down to approximately 50 ng mL⁻¹.     

Heterogeneous reactive extraction for secondary butyl alcohol liquid phase synthesis: Microkinetics and equilibria

The reaction kinetics for the liquid phase synthesis of a racemic mixture of the secondary butyl alcohols (SBA) from linear butene isomers (1-butene (1B); cis-2-butene (c2B); trans-2-butene (t2B)) and water (W) using a macroporous sulfonic acid ion exchange resin as catalyst were determined experimentally in a multiphase CSTR in the temperature range 39–433 K at 6–8 MPa. This range of pressures is necessary to dissolve butenes in the aqueous phase and to ensure a liquid state of all components. For temperatures higher than 423 K the reaction kinetics for the used catalyst size are influenced by mass transfer resistances within the catalyst matrix. The reaction takes place in the water swollen gel phase of the catalysts microspheres. Due to the large excess of water in the gel phase the compositions in the gel phase, in the macropore fluid, and in the catalyst surrounding aqueous phase are assumed to be identical. According to the literature the reaction is rather catalyzed by hydrated acid protons (specific catalysis) than by polymer-bonded-SO₃H groups (general catalysis). The experimental results can therefore be described sufficiently by a pseudo-homogeneous 3-parameter rate expression in aqueous phase activities. The forward reaction is first-order in butene. The reverse reaction is first-order in secondary butyl alcohol. The activation energy was determined to be 108 kJ/mol. Practically no pressure dependence could be observed for pressures exceeding 6 MPa. The ever-present isomerization of the linear butenes on acid catalysts was found to be remarkably faster than the hydration of butenes to SBA. Therefore, the isomerization is considered to be always in equilibrium during the olefin hydration. The formation of the possible by-product di-sec-butyl ether (DSBE) was never observed to a measurable extent. Simultaneous chemical and phase equilibria were investigated theoretically using the volume translated Peng–Robinson equation of state (VTPR-EoS) in combination with a g^E-mixing rule. Parameters of the used g^E-model were adjusted to experimental ternary liquid–liquid equilibrium (LLE) data.     

Identification of aroma‐active compounds in fresh and stored ‘Mor’ mandarins

In this study, gas chromatography–olfactometry (GC‐O) (sniffing) combined with gas chromatography–mass spectrometry (GC‐MS) analysis was applied to identify volatile aroma‐active compounds in homogenised segments of fresh and stored ‘Mor’ mandarins. The GC‐O nasal impact frequency method was used to identify Twenty‐three aroma‐active compounds, of which seventeen odorants were identified by GC‐MS. The aroma of fresh ‘Mor’ mandarins derived from a mixture of eleven odorants that contribute ‘green’ [(E)‐3‐hexenol and hexanal], ‘fresh’ [(E)‐carveol], ‘fruity’ (ethyl 2‐methylbutanoate), ‘citrus’ (limonene), ‘floral’ (linalool), ‘musty’ (β‐myrecene and γ‐terpinene), ‘potato’ (α‐terpinene), ‘mushroom’ (unknown 2) and ‘cabbage’ (α‐cubebene) odours. During postharvest, storage losses were observed in ‘green’ [(E)‐3‐hexenol] and ‘fresh’ [(E)‐carveol] odours, accompanied by increases in ‘fruity’ (ethyl propanoate) and several unpleasant aromas, such as ‘alcohol’ (ethanol), ‘musty’ [α‐pinene, (E)‐2‐nonenal and 1‐terpinen‐4‐ol] and ‘fatty’ (octyl acetate and δ‐cadinene) odours, all of which possibly account for the observed decrease in sensory acceptability after harvest.