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Abstract Processes based on non-thermal plasma (NTP) for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone (O 3) and nitrogen oxides (NO x). Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiO x , CoO x and MnO x with different weight percentage 1, 5 and 10 wt.%, deposited on a γ-Al 2 O 3 support. The O 3 removal efficiency (ORE) and the NO x removal efficiency (NRE) were very encouraging in dry air: about 65% and 80%, respectively, by using 2 g 5 wt.% MnO x /Al 2 O 3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity (RH) on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnO x /Al 2 O 3 catalyst with different trichloro(alkyl)silanes (TCAS). The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/g cat of modifying agent represents the best catalytic decomposition performance for O 3. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

The use of non-thermal plasma, corona discharge, was studied for indoor air applications. Toluene at a very low to moderate concentration (a few ppbv–1000 ppbv) was used as the target compound. Both degradation of toluene and generation of by-products (intermediates and ozone) were investigated. Because of the very low concentrations implemented in this study, high levels of removal efficiency were reached with very low specific density (a few J L −1 ). It was found that the polarity of the discharge was the parameter having the greatest influence: at 8.2 ppbv, removal efficiency could reach 98.2% under negative polarity while only 62% removal efficiency was achieved under positive polarity. This result is consistent with the lower ozone concentration in positive polarity and hence the lower plasma reactivity. The relative humidity of the air is another highly important parameter. It was found that the number of intermediates detected at the outlet of the plasma and removal efficiency both increased when increasing the relative humidity from less than 2%–40%. At higher relative humidity, toluene removal efficiency remained on the same order of magnitude (close to 80%), while the number and the amount of intermediates decreased. A higher oxidative rate was expected. [ABSTRACT FROM AUTHOR]

• The 1D model of an open heat storage reactor containing zeolite 13X is presented. • Model validation is based on simultaneous mass and heat transfer measurements. • Three adsorption isotherm models (Langmuir, DA, modified BET) are compared. • The modified BET model provides the best results (> DA > Langmuir). • Proper characterization of the sorbent (isotherms, heat of sorption) is essential. Efficient modeling of thermochemical heat storage reactors is required to predict their performance in various operating conditions and optimize their design. Such modeling necessitates an accurate description of the properties of storage materials, which is still challenging to this day. This paper specifically investigates the influence of the choice of the sorption isotherm model. To this aim, the Langmuir, Dubinin-Astakhov (DA) and modified Brunauer-Emmet-Teller (BET) isotherm models are studied. The 1D model of an open fixed bed reactor based on the hydration and dehydration of zeolite 13X is presented. The model couples heat and mass transfer and uses the linear driving force approximation. Experimental investigations are also performed to characterize the sorption equilibrium of the material, its adsorption kinetics at the reactor scale and the resulting heat storage performance. The model is validated simultaneously on the basis of mass and of heat transfer measurements (i.e., breakthrough and temperature curves). The BET isotherm is shown to be the most relevant for the description of water adsorption on zeolite 13X because it considers multilayer adsorption. It fits the experimental isotherm best. At the reactor scale, the modified BET model also provides the best results, closely followed by the DA model. Still, for consistent predictions, the characterization of the chosen sorbent (i.e., the experimental data used to correlate the isotherm model or the heat of sorption) is of utmost importance and the initial water loading must be adequately specified. [ABSTRACT FROM AUTHOR]

• Extended hygrothermal characterization of unstabilized rammed earth. • Low influence of density and grain size distribution on sorption isotherm. • High influence of density on thermal conductivity and vapor resistance factor. • Same linear dependency of thermal conductivity on moisture content for different soil compositions. • Vapor transfer resistance factor for a large span of relative humidity. Although hygrothermal properties of rammed earth represent great potential for improving thermal comfort during hot summers, still little knowledge is available about this topic. The literature lacks complete sets of hygrothermal characteristics of rammed earth, although they are fundamental for heat and moisture transfer modeling necessary to predict earthen building performances. The present work reports the results of a large collaboration between four academic laboratories in order to obtain an extended hygrothermal characterization of rammed earth, focusing on the material used in a modern construction in Lyon, France. The aim of the article is to provide for the same kind of soil an extend characterization on a large span of relative humidity to provide complete set of material properties for heat and moisture transfer simulation. The hygrothermal measurements cover adsorption and desorption isotherm, intermediate isotherm loop, specific heat capacity, dry thermal conductivity, moisture-dependent thermal conductivity and water vapor resistance factor for a large span of relative humidity. In addition, the capillary rise test was performed to estimate the liquid transport coefficient for suction and redistribution. The results show that variations in the density of the samples have a low impact on sorption isotherm, while they have a non-negligible impact on thermal conductivity and water vapor permeability. Surprisingly, variations in the grain size distribution do not produce a significant modification in the sorption isotherm, while hysteresis slightly reduces when bigger grains are added to the soil composition. Approximation of empirical model coefficients for the determination of moisture-dependent thermal conductivity is proposed for rammed earth materials. [ABSTRACT FROM AUTHOR]

New types of Cu-doped spherical-shaped activated carbons were prepared by pyrolysis at 700 °C of chitosan hydrogels impregnated with KOH at ratios (m KOH /m chitosan) ranging from 22.5% to 135%. At KOH impregnation ratio lower than 63%, the precursor Cu doping allowed obtaining bead-shaped activated carbons (diameter ~ 2 mm) and the highest specific surface areas (1145 m2 g−1). The absence of copper doping yielded to activated carbon powders whatever the KOH impregnation ratio. As increasing the impregnation ratio higher than 63%, the materials porosity type turns from exclusively microporous to both microporous and mesoporous. The microporous volume, determined by N 2 adsorption at 77 K and CO 2 adsorption at 273 K, attains a maximum (about 0.5 cm3 g−1) for a 63% impregnation ratio. Scanning Electron Microscopy (SEM) images show a multi-scale porosity for a KOH impregnation ratio higher than 45%. Nanoparticles of Cu and CuO were identified by SEM and Transmission Electron Microscopy in the ACs beads prepared from copper-doped chitosan. Whatever the composition, the beads are formed of N-enriched carbons showing mainly pyridinic and pyrrolic groups evidenced by XPS. [Display omitted] • Activation at 700 °C of KOH impregnated chitosan hydrogels beads. • Preparation of new types of Cu-doped spherical-shaped activated carbons. • KOH impregnation ratio of 63% optimised to obtain the highest micro-mesopore volume. • Presence of Cu/CuO nanoparticles observed by electron microcopy methods. • N-enriched carbons showing mainly pyridinic and pyrrolic groups evidenced by XPS. [ABSTRACT FROM AUTHOR]