Isovaleraldehyde elimination by UV/TiO2 photocatalysis: comparative study of the process at different reactors configurations and scales

A proposal for scaling-up the photocatalytic reactors is described and applied to the coated catalytic walls with a thin layer of titanium dioxide under the near ultraviolet (UV) irradiation. In this context, the photocatalytic degradation of isovaleraldehyde in gas phase is studied. In fact, the removal capacity is compared at different continuous reactors: a photocatalytic cylindrical reactor, planar reactor, and pilot unit. Results show that laboratory results can be useful for reactor design and scale-up. The flowrate increases lead to the removal capacity increases also. For example, with pilot unit, when flowrate extends four times, the degradation rate varies from 0.14 to 0.38 g h^?1 m_cat ^?2. The influence of UV intensity is also studied. When this parameter increases, zboth degradation rate and overall mineralization are enhanced. Moreover, the effects of inlet concentration, flowrate, geometries, and size of reactors on the removal capacity are also studied.     

Adsorption-oxidation of hydrogen sulfide on activated carbon fibers: effect of the composition and the relative humidity of the gas phase

The removal of hydrogen sulfide by oxidation-adsorption on two type carbon fibers, Actitex FC1201 and RS1301, was studied. Two kinetic steps where identified. During the first step, the degradation appears to be limited by the oxidation reaction. In the second kinetic step, the by-products inhibit the hydrogen sulfide degradation. This leads to a limitation in the carbon site's accessibility and to a lower kinetic. The Langmuir-Hinshelwood model was used to correlate the experimental results and to estimate the kinetic (k) and the Langmuir adsorption (K) constants. For FC1201 fibers, the kinetic constant (k) is five time higher and the adsorption constant is five time lower compared to the RS1301 fibers. The role of the humidity was found to be highly beneficial for the removal of hydrogen sulfide. Especially in the second kinetic step, where it removes the by-product formed and therefore delays the occurrence of this low kinetic step. The kinetic constant (k) is strongly influenced by humidity while the Langmuir adsorption constant (K) seems independent. The effect of the nature of the gas phase on the reaction kinetic was also studied. Under a dry atmosphere, we note that the oxidation-reaction occurs even if the gaseous oxygen is not present. This oxidation is due to the oxygen surface function of the carbon fibers. Moreover, the degradation kinetic is faster under a dry nitrogen atmosphere. The presence of water traces leads to the acidification of the carbon surface, under oxygen or carbon dioxide atmospheres, and hence limits the hydrogen sulfide dissociation. In a humid atmosphere, the oxygen or carbon dioxide leads to a faster reaction kinetic. The acidification of the carbon surface is largely counterbalanced by the dissolution of the by-products.     

Household incidence of pollution control policies: A robust welfare analysis using general equilibrium effects

This study assesses the incidence of pollution control policies on households. In contrast to previous studies, we employ an integrated framework combining a multisector general equilibrium model with a stochastic dominance analysis using household-level data. We consider three policy instruments in a domestic emission trading system: (i) an output-based allocation (OBA) of permits; (ii) the use of the proceeds of permit sales to reduce payroll taxes (RPT); (iii) and the use of these proceeds to reduce consumption taxes instead (UCS). The general equilibrium results suggest that the return to capital is more negatively affected than the wage rate in all simulations, since polluting industries are capital intensive. Abstracting from pollution externalities, the dominance analysis suggests that all three policies have a normatively robust negative (positive) impact on welfare (poverty). Formal dominance tests indicate that RPT first-order welfare dominates OBA over all values of household incomes. UCS also first-order poverty dominates RPT for any choice of poverty line below $CAN 18,600, and poverty dominates for any poverty line (and thus welfare dominates) at the second order. Finally, while the three pollution control policies do not have a numerically large impact on inequality (in comparison to the base run), statistical tests indicate that inequality increases significantly more with OBA and RPT than with UCS.     

Climate change risks in Sahelian Africa

Analyses of Sahel regional and country-specific rainfall and temperature time series derived from a fixed subset of stations show the well-documented large-scale decreasing trend in rainfall that occurred between 1970 and 2000 and also, an increasing trend in summertime maximum and wintertime minimum temperatures. The evolution of summertime mean maximum temperature is almost opposite to that of rainfall, and a significant correlation is observed between the evolution of this quantity and millet yields, in comparison with correlation with summertime rainfall. It appears that quantifying future vulnerability of the Sahel zone to climate change is rather difficult because climate models have not in general shown yet a satisfactory reproduction of the observed climate variability of this area.     

Mesoporous silica synthesized from natural local kaolin as an effective adsorbent for removing of Acid Red 337 and its application in the treatment of real industrial textile effluent

Environmental Science and Pollution Research - This paper presents a synthesis of mesoporous silica (MS) from natural clay as a silica source using Pluronic L35 (EO11PO16EO11) as a...     

Haloacetic acids,phytotoxic secondary air pollutants

Haloacetic acids are atmospheric oxidation products of airborne C₂-halocarbons which are important solvents and propellants. Levels of trichloroacetate (TCA) in conifer needles from mountain ranges in Germany (Black Forest, Erzgebirge) and from two sites in Finland are compared; TCA is present in conifer needles at concentrations up to 0.7 μmol/kg, MCA up to 0.2 μmol/kg. At the Finnish sites, TCA-concentrations and branch degeneration symptoms of Scots pine are correlated. Monochloroacetate (MCA) has been determined in needle samples from Southern Germany in concentrations exceeding its phytotoxicity threshold towards photoautotrophic organisms. Data on atmospheric chloroacetate levels in Germany are also given; ambient air levels of chloroacetic acids range from about 2 pmol/m³ (TCA) to 390 pmol/m³ (MCA). TCA and dichloroacetic acid (DCA) arise from atmospheric oxidation of airborne C₂-chlorocarbons, while the source of MCA is not yet known; several tentative pathways are suggested.     

Gaseous ethylbenzene removal by photocatalytic TiO2 nanoparticles immobilized on glass fiber tissue under real conditions: evaluation of reactive oxygen species contribution to the photocatalytic process

Environmental Science and Pollution Research - Photocatalytic oxidation (PCO) using a TiO2 catalyst is an effective technique to remove gaseous volatile organic compounds (VOCs). Herein, a...     

Machine learning-based prediction of toxic metals concentration in an acid mine drainage environment,northern Tunisia

Environmental Science and Pollution Research - In northern Tunisia, Sidi Driss sulfide ore valorization had produced a large waste amount. The long tailings exposure period and in situ minerals...